Metal Blasting Surface Prep Safety Bulletin

7/23/2019 Metal Blasting Surface Prep Safety Bulletin

1/29 2005-2015 Technology Publishing C

1

jpclPA INTSQUARE .COM JOURNAL OF PROTECT IVE COAT INGS & L IN INGS

SURFACE PREPARATION & SAFETY

A JPCLeResource



Copyright 2005 by

Technology Publishing Company2100 Wharton Street, Suite 310

Pittsburgh, PA 15203

All Rights Reserved

This eBook may not be copied or redistributedwithout the written permission of the publisher.

Surface Preparation & Safety



i

v Introduction

1 Safety Monitoring and Remote Control Systems3 OSHAs Proposed Rule for Silica Hits the Streets

By Alison B. Kaelin, CQA, ABKaelin, LLC

5 Shipyard Regulatory Update By Alison B. Kaelin, CQA, ABKaelin, LLC

10 On the Time Between Blasting and Priming

11 Safety Considerations for Abrasive Blasting Operations

15 Setting Up Air Blasting Equipment

19 Surface Preparation: Adventures in Frustration By Peter Bock, CorrLine International

Contents
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IntroductionThis eBook features articles from the Journal of Protective Coatings &

Linings(JPCL) about surface preparation and safety. All information about

the articles is based on the original dates of publication of these materials

in JPCL. Please visit www.paintsquare.com for more articles on these and

other topics.

v



1

Blast cleaning is a critical process to remove mill scale,

slag, and pre-existing coatings on steel surfaces and to

prepare substrates for the subsequent application of aprotective coating. Dry abrasive blast cleaning is known

to provide the best surface roughness for an ordinary

organic or inorganic coating, although it is considered a very

dangerous process.

In shipyards, dry abrasive blast cleaning is especially dan-

gerous. Modern shipbuilding practice is to construct vessels

as a series of blocks, coat these, and then join up to finish

the build. Workers must contend with a very poor environ-

ment because of a mist of paint debris, spent abrasive parti-

cles, noise, and the danger from blasting media traveling at

a high speed. Also, their work can involve moving through

narrow access holes (600 mm x 800 mm hole) in the steel

blocks. Moreover, blasters work alone for a long time. There

is virtually no visibility inside these steel blocks during blast-

ing, so developing a safety system for blast cleaning workers

is more essential than for many other types of projects.

Basing a remote workers safety and contact system on

wireless technology is more difficult to develop than such

a system for other work areas because of the possibility at

shipyards of wireless data transmission errors by reflection,

refraction, and diffusion of the radio waves in the blasting

area (cell). There are also technological limits in building

the safety system for shipyard job areas, but developments

in IT (Information Technology) and RFID (Radio-Frequency

Identification) technology have made remote control safetysystems possible.

This article summarizes work carried out by Won-Jun

Yun, Byung Hun Lee, and Dong-Min Kim of Hyundai Indus-

trial Research Institute, Hyundai Heavy Industries, Co. Ltd.

Korea, and Young-Shick Ro, School of Electrical Engineering,

University of Ulsan, Korea, into such a system. The summa-

ry will concentrate on the features of such a safety system,

rather than on the technical aspects.

The summary is based on a presentation given at PACE

2010, the joint conference of SSPC and PDCA, held Feb.

710, 2010, in Phoenix, AZ. The full paper is published in the

Proceedings (www.sspc.org).

The Safety System FeaturesThe complete safety system is composed of three sub-sys-

tems: the monitoring system for checking the blast workerssafety, the remote control system of the blasting nozzle(s),

and the special bone conduction ear-set system for voice

communications among workers and managers. Addition-

ally, the safety system has a function to analyze the actual

result of a blast cleaning job.

In shipyards, dry abrasive blasting

is especially dangerous.

The Safety Monitoring System

The safety monitoring system features emergency call sig-

naling, sensing vibration data, and checking location data for

blast cleaning workers in the blasting cell.

When the worker with a 2.45GHz RFID active tag is work-

ing in the blasting cell, the safety system works as follows:

information about working conditions is transmitted from

the active tag through a network to the monitoring system,

where the manager can check workers safety using comput-

er-analyzed emergency signal data with the workers loca-

tion information.

The monitoring system consists of three functions to

check workers safety and to send the emergency signal tothe manager. First, its a function for storing and analyzing

information; second, its a function for monitoring workers

location and their safety information; and third, its a func-

tion for sounding a buzzer and sending SMS (Short Mes-

sage Service) to the manager. Also, it can give an alarm by

analyzing the vibration sensor on a worker, including direct

emergency calling. Finally, it can monitor remaining battery

capacity of the active tag and temperature of the working

conditions.

The Remote Control System for Blasting Nozzles

The remote control of blasting nozzle(s) is integrated with

Safety Monitoringand Remote Control Systemsfor Blasting in Shipyards

1



2

Operation Procedure of the Safety SystemTo confirm workers safety, there are three ways to check the

emergency signals from workers in the blasting cell: sensing

the active tag emergency call, analyzing a sensed danger

signal automatically by vibration sensor, and using voice

communication with a special bone conduction ear-set.

The monitoring system can sense various emergencies,ring alarms, and send the information about the emergen-

cy to managers. After the manager checks the SMS or the

emergency signal on the monitoring system, he or she

can reconfirm the workers safety by having a conversa-

tion through the bone conduction ear-set. If an emergency

occurs, the blasting nozzles can be controlled remotely by a

manager. Also, actions can be taken for workers to be safely

evacuated from the life-threatening emergency, as well as

for the urgent rescue of nearby co-workers. Emergency sig-

nals can be transmitted to all managers to prevent sudden

accidents and to inform them of the rescue process.

This innovative safety system for workers blasting in ship-

yards allows managers to communicate with workers in realtime and thus also allows managers to properly distribute

the workload and make a contribution to the improvement in

productivity.

the safety monitoring system to cut compressed air when an

emergency situation occurs. Managers also can check the

blasting nozzle status and turn it off remotely using PC when

emergencies occur. The remote control system can control

the blasting nozzle valve directly after checking the condition

of blasting nozzles one by one or altogether.

The Special Bone Conduction

Ear-Set Communication

The special bone conduction ear-set system with neck mi-

crophone is necessary to communicate about blast working

conditions in the cell with a person in the managing office.

Working conditions in the blasting cell and protective

clothes for blast cleaning work are not conducive to easy

voice communication. So it is more difficult to communicate

using normal methods inside the steel block. Thus, a special

system that the worker can use while wearing a mask, ear-

plugs, and a helmet had to be developed.

For communication among workers and managers during

the blast cleaning job, the special voice communicationsystem using the existing infrastructure with TRS (Trunked

Radio System), which can communicate with a group, was

used. Workers wearing masks and earplugs can still listen

with the aid of the bone conduction mechanism and speak

using a neck microphone, which makes communication pos-

sible through the vibration of vocal cords.

Because blast cleaning workers must pass through small

access holes to work in the steel block, the developed sys-

tem is small and has the added conveniences of portability

and noise interception.



3

others discussed in the proposal: abrasives such as mineral

slags as well as sand, paints, concrete, portland cement,

silicates, and soil.

As part of the rulemaking, OSHA performed an extensive

analysis entitled Respirable Crystalline SilicaHealth

Effects Literature Review and Preliminary Quantitative Risk

Assessment. The available evidence indicated that employ-ees exposed to respirable crystalline silica at concentrations

well below the current PELs (of 100 and 250 g/m3) have

an increased risk of lung cancer and silicosis. Occupational

exposures to respirable crystalline silica also may result in

the development of kidney and autoimmune diseases and in

death from other nonmalignant respiratory diseases, includ-

ing chronic obstructive pulmonary disease (COPD).

Summary of the Proposed RulesAmong the aspects of the proposed rule that may be of inter

est to the coatings industry are the following.

Requirements to comply with applicable ventilation stan-

dards (e.g., 29CFR1926.57) for abrasive blast cleaning. Whilethe ventilation standards have long been in place, they have

not been fully implemented in many containment systems.

Requirements for laboratory analysis of respirable silica

samples by an ISO 17025-accredited laboratory.

Construction industry exemption from exposure monitor-

ing for specific operations if engineering and work practice

controls and respiratory protection are implemented.

Options for establishing regulated areas or developing a

written access plan (which appears to be very similar to the

worker protection plan required by the Lead Standard).

Addressing training requirements via the Hazard Communi-

cation Standard.

The paragraphs in the proposed rule address similar topics

(e.g., methods of compliance) of other comprehensive health

standards.

The box on p. 53 gives a brief summary of the proposals

for General Industry and Shipyards and for Construction.

The box highlights some similarities and differences be-

tween the two proposals.

Alison B. Kaelin, CQA, has more than 25 years of public

health, environmental, transportation, and construction man-

agement experience in the coatings industry. She is the own-

er of ABKaelin, LLC, a Pittsburgh,

PA-based provider of outsourcedquality assurance, auditing, training,

consulting, and related services

to the protective coatings, con-

struction, fabrication, and nuclear

industries. She is a certified quality

auditor, a member of SSPC, and a

NACE-certified coating inspector.

She was a 2012 JPCL Top Thinker,

a 2012 JPCL Editors Award Winner, and an SSPC Technical

Achievement Award winner in 2005.

(See table on next page)

OSHAS Proposed Rulefor Silica Hits the Streets

By Alison B. Kaelin,

CQA, ABKaelin, LLC

On August 23, 2013, the U.S. Occupational Safety and

Health Administration (OSHA) unveiled its long-expect-

ed proposed rule for protecting workers against respi-

rable crystalline silica. OSHA issued two versions of the

proposed rule, one for general industry and shipyards

(1910/1915) and one specific to construction (1926).

The proposed rule reduces the current permissible exposure

limit (PEL) for general industry, shipyards, and construction

to 50 micrograms per cubic meter of air (g/m3). The current

PEL for general industry and shipyards is 100 g/m3, and the

current PEL for construction is 250 g/m3.

Once published in the Federal Register, OSHA will acceptcomments for 90 days, as part of a rulemaking process. A

hearing will be held in early March 2014, and the final rule

will be issued sometime after. The proposal and related in-

formation can be read on https://www.osha.gov/silica/index.

html.

While no conclusions on the actual requirements should

be drawn based on a proposed rule, the proposed provisions

do provide insight into likely approaches that will be con-

sidered by OSHA when the final rule is issued. Employers

should consider the requirements of the proposed rule as

they apply to their operations, and plan how to implement

the requirements when the rule is final. Background on

respirable crystalline silica, including its health effects, and asummary of the proposal follow.

BackgroundSilica is a compound composed of the elements silicon and

oxygen (chemical formula SiOz). Respirable crystalline silica

means airborne particles that contain quartz, cristobalite,

and/or tridymite. The respirable portion is determined by a

respirable-particle-size-selective sampling device.

The proposed rule estimates that exposures to crystalline

silica can occur in more than 30 major industries and opera-

tions. Silica can be present in the following materials and in



4



This article reviews OSHA enforcement on shipyard ac-

tivities and recent guidance on illumination and ventila-tion related to ship repairing, shipbuilding, and ship-

breaking that fall under OSHAs Standards for Shipyard

Employment (29 CFR 1915). It also discusses new OSHA

information on abrasive blasting hazards and potential Cal/

OSHA Lead Standard changes that are applicable to shipyard

and many other industrial painting sectors.

Shipyards are fixed facilities with dry docks and fabrication

equipment capable of building a ship, defined as watercraft

typically suitable or intended for uses other than personal

or recreational. Activities of shipyards include the construc-

tion of ships, their repair, conversion and alteration, and theproduction of prefabricated ship and barge sections.

OSHA Enforcement SummaryReview of the most frequent OSHA citations for NAICS Code

336611Ship Building and Repairing from October 2012

through September 2013, and OSHAs enforcement data

for NAICS 336611 and 29 CFR 1915, indicates the following

areas of non-compliance resulting in citations. Areas are

ordered from highest to lowest, and some similar areas were

grouped by the author.

Respiratory protection

Wiring design, protection, methods, components, andequipment for general use

Guarding of deck openings and edges

Welding and cutting (arc, gas, and oxygen-fuel)

Hazard communications

Toxic metals

Painting

Abrasive wheel machinery

Occupational noise

Hand and portable powered tools and equipment

Confined space

Lighting Lockout/tagout

OSHA Shipyard Fact Sheets IlluminationIn November 2013, OSHA issued a Fact Sheet on Safe Light-

ing Practices in the Shipyard Industry. It elaborated upon

29 CFR 1915.82, Subpart F, General Working Conditions:

Lighting, and provided the minimum lighting requirements

(Table 1).

Note that the values in Table 1 differ from SSPC-Guide 12,

Guide for Illumination of Industrial Painting Projects, which

Shipyard Regulatory UpdateWhats Happening with Enforcement, Regulation,

and New OSHA Guidance DocumentsBy Alison B. Kaelin, CQA,

ABKaelin, LLC

iStockphoto/milarka

5



6

suggests that a higher level of lighting is required for work,

surface preparation, and inspection activities. SSPC-Guide

12 recommendations are shown in Table 2.

Use of a portable light meter can help assess the adequacy

of lighting. Be sure to use it frequently to re-verify that light-

ing levels remain constant. Make sure your light meter is

capable of taking measurements in the range of your lights

and that it meets your accuracy needs. Most light metershave an accuracy range from 5% up to 18% and even higher.

OSHA Ventilation in Shipyard Employment Guide A Shift in Approach?OSHA 3639-04 2013: Ventilation in Shipyard Employment

provides a review of basic principles of ventilation and

provides methods for selection, installation, and use of venti-

lation systems to reduce contaminants during shipyard oper-

ations. While it primarily focuses on confined and enclosed

spaces, it provides guidance applicable to any industry.

Unlike General Industry (1910) and Construction (1926), Mar-

itime (1915) does not have specific ventila-

tion requirements.

OSHA General Industry Standard Ven-

tilation standard (1910.94, Ventilation),

published in the 1970s, established the first

requirements for abrasive blast booths as(1) exhaust-ventilated to provide continuous

air flow at all openings during blasting op-

erations, (2) capable of preventing escape

of abrasives into adjacent work areas, and

(3) able to provide prompt clearance of dust

when abrasive blasting ceases.

The Industrial Ventilation: Manual of

Recommended Practices, published by the

American Conference of Governmental

Industrial Hygienists, provided the basis

for the design of blast booths for the statedpurpose of operator visibility and to con-

trol escape of contaminants into adjacent

work areas. It established the minimum

air flows (60100 feet per minute), trans-

port velocities in ductwork (3,500 feet per

minute), and design criteria with inward air

flow exhausting to a remotely located dust

collection system, as shown in Figure 1.

SSPC-Guide 6, Guide for Containing

Surface Preparation Debris Generated

During Paint Removal Operations, relies onthe Industrial Ventilation Manual criteria as

Fig. 1: Typical blast booth

design

Source: Reference 10.80.3

and 10.80.4; American

Conference of Govern-

mental Industrial Hygien-

ists, Abrasive Blasting

Room, 02-91, VS-80-01

Q = 60100 cfm/ft2 of floor for downdraft with typical choice 80 cfm/

Q = 100 cfm/ft2 of wall for cross draft

Lower control velocities may be used depending on toxicity of the co

taiminant, object and blasting media, and the size of the blasting roo

Notes: 1. The above ventilation is for operator visibility and to

control escape of contaminants into adjacent work areas.

2. Operator in an abrasive blasting room is required to wea

appropriate NIOSH-certified respiratory protection.

3. For rotary tables, use 200 cfm/ft2 of total opening (taken

without curtains).

4. For blasting cabinets, see VS8002.

SECTION THROUGH TYPICAL ROOM



7

the basis of its ventilation requirements for abrasive blast-

ing containments. In industrial field painting, it generally

involves bringing duct work to the face of the containment

system or just inside the containment wall and having air

inlets generally across from them, mimicking the design of a

blast booth (Fig. 2). This type of venti-

lation is considered

dilution ventilation

(general exhaust

ventilation), which is

a form of exposure

control that involves

providing enough air

in the workplace to di-

lute the concentration

of airborne contam-inants to acceptable

levels.1

The Shipyard

Guide states that both

general dilution ventilation and local exhaust ventilation

(LEV) at the source are suitable for controlling exposures.

However, it states that local exhaust ventilation is typically

preferred and more effective.

The Shipyard Guide also states that dilution ventilation

involves the reduction of contaminants being generated

in the space through the introduction ofclean outdoor air (through air inlets) and

removal of the contaminants through a

dust collector. It notes that sometimes, this

can cause a supply and exhaust imbalance

that positively or negatively pressurizes the

space or results in short circuiting (when

only a small portion of the space is venti-

lated). The Shipyard Guide depicts dilution

ventilation as inefficient, requiring a lot of

air and air movement to reduce the level of

hazardous contaminants. The Shipyard Guide also suggests that

four factors should be considered before

using dilution ventilation for protecting

worker health.

(1) The quantity of contaminant released

should be relatively low and uniform.

(2) Workers should be located far away

from the contaminant source.

(3) The toxicity of the contaminant must be

low.

(4) There is no need to collect the air contaminant.

If we apply the four factors to industrial painting and abra-

sive blast cleaning in the construction, marine, or shipyard

industries, where the quantity of contaminants are high and

non-uniform and many of which are toxic, it would suggest

that LEV may be more appropriate than dilution ventilation. LEV is an industrial ventilation system that captures

and removes emitted contaminants before dilution into the

ambient air of the workplace.1 While we typically associate

LEV with vacuum shrouds and vacuum attachments, LEV can

include placement of one or more exhaust air ducts in the

immediate vicinity of where the exposure is occurring. LEV

is frequently used in the shipbuilding industry and is the rec-

ommended method when workers are exposed to hazardous

chemicals, when a large amount of dust or welding fumes

are generated, or during cold weather when increased heat-

ing costs from the use of dilution ventilation is a concern. The Shipyard Guide suggests that using ventilation in an

exhaust mode and placing the ductwork where contami-

nants are released in the air by the operation is an effective

method in capturing the generated contaminants and greatly

reduces exposure to workers in a space (Fig. 2).

Table 3 (excerpted from Ventilation in Shipyard Employ-

ment), suggests that LEV may be more appropriate for abra-

sive blast cleaning.

While the preference for LEV may be specific to shipyards,

all industries should evaluate the hazards and unique char-

Fig. 2: Ecient method of supplied

ventilation (forced air) with system

away from tank opening.

Source: Edward J. Willwerth, Atlantic

Environmental & Marine Services



8

acteristics of the work area to which their employees are

exposed and consider all methods for reducing exposures.

When working with materials covered by comprehensive

health standards (such as lead) which require the use of

engineering controls for the purpose of reducing worker

exposures to as low as feasible, LEV may be more in linewith the definition of an engineering control, which focuses

on elimination or reduction of the hazard at the source.

Duct WorkWhether you use dilution or local exhaust ventilation, an

integral part of the system is the ductwork. The Shipyard

Guide is consistent with the guidance provided in SSPCs

C3 Course, and SSPC-Guide 16, Guide to Selecting Dust

Collectors, and states that consideration should be given to

the type and length of the hose and layout of duct work to

ensure the greatest amount of air flow. As the length of hose or ductwork increases, the amount

of air moved decreases due to frictional losses. Therefore,

the shortest length of hose or ductwork should be used.

Equally important is the amount of bends or turns in

the ductwork. A greater number of bends or turns greatly

decreases the volume of air moved. Try to keep the hose as

straight as possible. To put this in perspective, one sharp

90-degree bend in a 20-inch-diameter duct is equivalent to

adding 46 additional feet to the length of the ductwork.

When we install ductwork through manways, small open-

ings, and other limited egress areas, it may impede entry/exit. The Shipyard confined space standard requires that if

ventilation ductwork blocks access to a confined space, then

all workers must be provided with airline respirators, and

a person must be stationed outside the space to maintain

communication and to aid in the event of an emergency. The

Guide suggests a saddle be used in these cases. A saddle is

a piece of equipment that allows entry/exit without remov-

ing the duct work.

Abrasive Blasting Hazards

OSHA released a new fact sheet in November 2013, titled,

Protecting Workers from the Hazards of Abrasive BlastingMaterials. It outlines the following abrasives and likely

health effects.

Silica sand (crystalline) can cause silicosis, lung cancer,

and breathing problems in exposed workers.

Coal slag and garnet sand may cause lung damage similar

to silica sand (based on preliminary animal testing).

Copper slag, nickel slag, and glass (crushed or beads) also

have the potential to cause lung damage.

Steel grit and shot have less potential to cause lung dam-

age.

Slags can contain trace amounts of toxic metals such as

arsenic, beryllium, and cadmium.

The fact sheet also suggests that when performing abra-

sive blasting to reduce worker hazards from materials, one

needs to use nearly identical controls as one would for lead

or other toxic metals, including engineering controls (e.g.containment and ventilation), work practices (hand and body

PPE and hygiene), and respiratory protection. Some other

observations made in the fact sheet include:

recommending the use of alternative, less toxic blasting

materials such as sponge, baking soda, or dry ice;

keeping coworkers away from the blaster;

cleaning and decontaminating tarps and other equipment

at the worksite; and

scheduling blasting when the least number of workers are

at the site.

Take a look at your abrasive blast cleaning operations andmaterials and consider what equipment, processes, materi-

als, or worker changes may be necessary to reduce worker

exposures to abrasive blasting material hazards.

Are We Closer to Revising the Cal/osha Lead Standard?

In April 2011, the California Department of Health/Occupa-

tional Lead Poisoning Prevention Program (OLPPP) began

providing information to support revisions to the 30-year-old

Cal/OSHA Construction Lead Standard based on more recent

health-based scientific evidence. OLPPP suggests that the

following changes are necessary.

Provide medical surveillance, blood lead level (BLL)testing, annual blood pressure measurements, and question-

naires to all employees likely to be exposed to lead.

Increase frequency of medical surveillance of BLLs and

further increases if above 10 g/dL.

Remove employee from lead exposure at or above 30 g/

dL or if two successive blood lead concentrations measured

over a four-week interval are at or above 20 g/dL.

Return employee to work when two blood lead tests taken

four weeks apart are less than 15 g/dL.

Lower Permissible Exposure Limit (PEL)/Action Level (AL)

which reflect new medical/toxicological information onchronic and low-level health effects.

Conduct regular testing of surfaces in eating areas and

change areas and clean more frequently when lead is found.

Establish a quantitative limit for lead on surfaces and specify

sample collection and analysis methods.

Provide quarterly employee training. Training should maxi

mize the use of participatory and hands-on methods.

Post warning signs in areas where lead is present.

Define and require minimum engineering and work prac-

tice controls unless the employer can demonstrate that such



9

controls are not feasible.

Do not allow certain high-risk work

practices.

In October 2013, the California Department of Public

Health (CDPH) made a recommendation to Cal/OSHA for a

new PEL based on the low level health effects literature andnew modeling of the relationship between air lead levels and

blood lead levels.

CDPH used an updated version of the original model used

by OSHA to develop the General Industry Standard for lead

and challenged the model using actual BLL and mortality

data obtained over the last 20 years. The modeling and the

conclusions support the overwhelming body of recent scien-

tific evidence indicating the health impacts of very low BLL

exposures ranging from 510 g/dL. The modeling focused

on two issues.

Estimate the amount of lead in workplace air inhaled byworkers without respirators that would result in BLLs of 5,

10, 15, 20, and 30 g/dL over a 40-year working lifetime.

Estimate the time it would take for a workers BLL to come

down to 15 g/dL from a higher level once the worker is

removed from workplace lead exposure.

The modeling arrived at the following conclusions.

To keep almost all workers (95%) BLLs below 5 g/dL

over their working lifetime, the amount of lead in the air the

worker is exposed to must not be above 0.5g/m3 averaged

over an 8-hour workday.

The model also shows that the amount of lead in a work-ers blood climbs very fast in the first few years of workplace

exposure and then climbs much more slowly in the remain-

ing years. Even though a workers BLL does not climb much

during the remaining years, lead levels in the bones continue

to increase. The lead in the bones is slowly released into the

blood throughout a workers lifetime.

The model also estimates the time it may take for a work-

ers BLL to come down to a BLL of 15 g/dL, after removal

from workplace exposure.

The CDPH concluded that based on available scientific

evidence adverse health effects begin to emerge at BLLs of10 g/dL and likely lower.

Modeling suggests that in order to maintain BLLs of 10 g/

dL over a working lifetime in 95% of workers, the air concen-

tration of lead must not exceed 2.1 g/m3 as an 8-hour TWA

average or to maintain a BLL of 5 g/dL a PEL of 0.5 g/m3

as an 8-hour TWA average.

Cal/OSHA is expected to introduce a final rule by the end

of this year. Industry professionals expect medical removal

levels to be established at 1520 g/dL and a PEL of approxi-

mately 20 g/m3 as an 8-hour TWA average.

References1. OSHA Technical Manual.

About the AuthorAlison B. Kaelin, CQA, has more than 25 years of public

health, environmental, transportation, and construction man-agement experience in the coatings industry.

She is the owner of ABKaelin, LLC, a pro-

vider of OSHA training, quality assurance,

auditing, consulting, and related services

to the protective coatings, construction,

fabrication, and nuclear industries.

Kaelin is a certified quality auditor and

NACE-certified coating inspector. She was a 2012 JPCL Top

Thinker, a 2012 JPCL Editors Award Winner, and an SSPC

Technical Achievement Award winner in 2005. At SSPC 2014,

she was presented the inaugural Women in Coatings ImpactAward. She is a JPCL contributing editor.



10

From Lee Edelman

CW Technical Service

Always attempt to prime the prepared surfaces before the

specified surface preparation starts degrading. Most speci-

fications will address this practice. Humidity and dew pointshould be monitored throughout the process, so that when

humidity or dew points exceed what the specification al-

lows, there should not be any painting activities.

If the prepared surface has degraded, most specifications

will require reblasting to the specified degree of surface

preparation.

From Richard D. Souza

Stoncor Middle East LLC

How long a blast-cleaned surface can remain uncoated is not

the issue; rather, the highest criterion is the steel tempera-ture: It should always be at least 3 degrees C (5 F) higher

than the calculated dew point temperature. This margin of

safety is sufficient for all type of coatings.

A common scenario is that the contractor blasts all day

long; experiences problems with the compressor or oth-

er piece of equipment; and as a result of the equipment

problems, lets the newly blasted steel sit a long time before

coating. But the standard requires that the surface to be

painted must meet the cleanliness criteria set by the client or

consultant. These criteria supersede every other judgment

and vary from job to job. In Jordan, for example, oxidation

or orange rust may not occur for several hours or days, but

in UAE, you can probably expect to see rust break through in

few hours, depending on the time of the day or night.It is almost impossible to state the effect of time, tem-

perature, and humidity on all blast-cleaned surfaces. On any

given job, the answer must be the sole responsibility of the

inspector, who conducts on-site checks of the conditions

such as the following:

Place of work

Air temperatureminimum and maximum

Relative humidity

Dew point

Steel temperature

Necessary ventilation Type of weather, such as sunlight, rain, wind speed, and

direction

These on-site checks must be done at least three times per

shift. The inspector should have the sole right to determine

the time without deviating from the specification.

From Remko Tas

Futuro SRL

As a curiosity, flash rust did not occur for 10 days in a dry cli-

mate at an altitude of 4,000 m (13,000 ft) in Bolivia, hundreds

of kilometers away from the influence of saltwater and con-tamination from industry-generated air pollution. We could

still safely paint the interior of the tank in one shot, achieving

a high efficiency.

From Lubomir Jancovic

MSPLUB Inc.

You have to prime the blasted surface of steel within eight

hours. Otherwise, blasting was for nothing. If the relative

humidity is more like 60%, you have to prime the surface

within four hours.

How long can a blasted

surface be left before

priming under different

temperatures/relative

humidity environments?

Editors Note: Problem Solving Forum questions are posted

on the free daily electronic newsletter, PaintSquare News,

on behalf of JPCL. Responses are selected and edited to

conform to JPCL style. To subscribe to PaintSquare News,

go to www.paintsquare.com/psn/.

On the Time between Blasting and Priming



11

The Occupational Safety and Health Administration

(OSHA) writes and enforces regulations that govern

safety and health practices in the work place, with many

pertaining to cleaning and painting operations. Most

of these regulations are very specific about how to

do a job safely. Their purpose is not to make our job more

difficult, but to make it safer. These regulations have been

developed over many years through studies on how and

why accidents happen, and following these written proce-

dures and regulations should ensure that we don t make the

same mistakes that have injured others in the past.

This article will review some of the general requirements

of regulations on abrasive blasting and explain how they can

help increase job safety.

Hazards of Abrasive Blasting

When you blast clean surfaces with abrasive driven by air,

you have to deal with several hazards to your health and

safety. Some of these hazards can be lethal, so it is import-

ant that you understand what they are and observe the

proper safety precautions. The hazards of abrasive blasting

include, but are not limited to:

dust,

noise, and

equipment.

Dust

The dust produced by abrasive blasting is a very serious

health hazard. Dust results from the breakdown of abra-

sives and the pulverizing of surface coatings, rust, millscale,

and other materials on the steel surface being blasted. The

individual dust particles vary in size from 1 micron (125,000-

inch) to 1,000 microns (125-inch) in diameter. Dust larger

than 10 microns may be visible and settles quickly. Dust

smaller than 10 microns, called respirable dust, is invisible,

remains suspended in the air for a longer period of time,

and can pass through the respiratory systems defenses and

settle in the small air sacs in the lung called alveoli.

Safety Considerations

for Abrasive Blasting Operations

Editors Note: This Applicator Training Bulletin i

an update of an original article written by Walte

Shuler, certified safety professional and safety

consultant; Jeff Theo, Service Painting Compa-

ny; and Mike McGinness, Custom Process Sys-

tems. The article was originally published in the

June 1998 issue of Protective Coatings Europe

(PCE) and was updated for this issue by Dan

OMalley, Manager of the Environmental, Health

and Safety Group; and Stan Liang, Director of

Health and Safety; KTA-Tator, Inc.

iStockphoto/ZooCat



12

Dust of this size cannot be dissolved by the lung fluids.

Because the lung cannot break down or cast out the par-

ticles, it does the next best thing in its defense program,

which is to isolate the intruder by building a thick, fibrous

tissue around it. When too much of this tissue develops, the

lung is said to be fibrotic, or in a condition of fibrosis. The routes of entry and the associated health effects de-

pend on the chemical and physical properties of the dust. If

the dust is soluble in water and respirable in size, it can enter

the alveoli, pass through the walls of the alveoli in the lungs,

and enter the bloodstream. Once in the bloodstream, dust

can be transported rapidly throughout the body and damage

various organ systems.

Other health hazards may be present in the dust pro-

duced by the abrasive blasting process. These hazards can

result from the removal of coatings containing toxic metals

such as lead, arsenic, cadmium, and hexavalent chromium.

One of the most common toxic metal hazards encountered

in the removal of a coatings system is lead, a toxic metal tha

can damage the bodys blood-forming, nervous, urinary, and

reproductive systems. Lead also accumulates in the body;

thus, exposure to small doses over long periods of time cancause great harm.

Exposure to toxic metals can also directly affect the skin.

Metals such as hexavalent chromium can irritate the skin or

cause an allergic reaction. Other metals can have an irritant

effect on the respiratory tract, such as pulmonary edema

(fluid build-up in the lungs) caused by severe cadmium

dust exposure. Entry can also occur via ingestion, typically

caused by poor hygiene practices such as eating, drinking,

and smoking in the work area.

To determine the specific toxic metals likely to be present

in a coatings system, paint chip samples should be collectedfrom representative areas of the structure. The metals that

the samples should be analyzed for would depend on a num

ber of considerations, such as the type of structure and the

type of coatings system being evaluated. Sometimes, toxic

metal content can be determined based on historical knowl-

edge of the coatings system being evaluated.

Toxic metals can also be present in the virgin abrasive

blast media, such as crystalline silica in silica sand abra-

sive. However, dust-containing crystalline silica also can be

produced during other abrasive blasting activities, such as

surface preparation of concrete. A study published in theSeptember 2006 issue of the Journal of Occupational and

Environmental Hygiene indicated that elevated exposure to

crystalline silica exposure also can result when it is present

in the coatings system being removed.1

The Safety Data Sheet should be consulted to determine

what metals may be present in the abrasive blast media.

Recently, OSHA has begun requiring abrasive manufacturers

to list toxic metals in their products, even if they are present

only in trace amounts. Arsenic is commonly found in steel

grit and coal slag abrasives, while beryllium is commonly

found in coal slag abrasives. When there is exposure to toxic dust, the primary con-

cern is to control respiratory exposure. Respiratory protec-

tion must comply with the OSHA Respiratory Protection

Standard (29 CFR 1926.103). This standard requires feasible

engineering and work practice controls to be employed be-

fore respiratory protection is used by workers. Engineering

controls include ventilated abrasive blasting containments

and considering alternatives to abrasive blasting, such as

vacuum-shrouded power tools, water jetting, and chemical

stripping. Job rotation is an example of a work practice con-

iStockphoto/tolgabayraktar



13

trol. Note that job rotation is not permitted by OSHA in all

cases (if workers are exposed to hexavalent chromium, for

instance). If such a control is used, a written schedule must

be developed and followed.

Respiratory protection may only be used after engineer-

ing and work practice controls are employed and workers

are still exposed above the OSHA Permissible Exposure

Limit (PEL) for a given toxic dust. Employers must select,

use, and maintain respirators in accordance with a written

program (the elements of which are specified by OSHA in

the Respiratory Protection Standard).

Blasters typically use a Type CE or helmet-type airline

respirator. Workers in the vicinity of the blasting area, such

as pot tenders and lookouts, are required to wear respiratory

protection. Workers engaged in clean-up operations should

also be equipped with respiratory protection. These workers

are usually assigned a half-mask, air-purifying respirator

with high-efficiency cartridges (labeled as N, R, or P 100).

However, workers cleaning up abrasive blasting debris when

blasting is still in progress (as is often the case when recycla-

ble grit is used) may need a higher level of protection. Such

workers may need to wear the same type of respirator as the

blasters, as their exposure levels are likely to be similar.

The National Institute of Occupational Safety and Health

(NIOSH) conducts research on health issues in the work

place, and one of its main functions is to test and certify

industrial respiratory protection equipment. All respiratoryprotection equipment used in the workplace must be ap-

proved by NIOSH.

Respiratory protection should continue to be worn after

blasting as long as dust-laden air remains. Respirable dust

in an abrasive blasting booth or containment can remain

suspended for long periods of time after blasting is finished.

This time period is largely dependent on the effectiveness of

the ventilation system, unless the work is performed out-

doors.

A health and safety professional should review all proj-

ects that require abrasive blast cleaning to determine whatprecautions, if any, should be taken to eliminate the hazard

of chemical exposure. Examples of these precautions include

disposable clothing, boots, gloves, respiratory protective

devices, and hygiene practices. Hygiene facilities that can be

required by OSHA include hand wash stations and showers.

OSHA requires provision of a hand wash station when work-

ers may come into contact with toxic materials. Whether or

not showers are mandatory depends on which OSHA stan-

dard is applicable. If workers are exposed to lead, showers

are required when exposures exceed the PEL.

NoiseMost forms of abrasive blasting create the hazard of noise

exposure, which will vary depending on the blasting condi-

tions. Regardless of the nature, excessive amounts of noise

may require personal hearing protection for blasters and

other workers in the general area. Depending on the size of

the equipment, the material being blasted, and the location

of the blasting operation, noise levels can range from about

90 decibels to more than 110 decibels. OSHAs limit for noise

depends on the duration of exposure. For an eight-hour shift

of continuous exposure, the limit is 90 decibels. Personal

hearing protection should then be recommended if the level

and exposure time of the workers exceed the OSHA stan-

dard. Noise protection must reduce exposure to below the

OSHA limit.

Note that some abrasive blasting hoods already provide

some degree of noise protection, but the manufacturers

specifications should be checked to see if the degree of noise

reduction will be adequate. When there is any question

about the existing levels (meaning a noise survey is needed)

or the adequacy of hearing protection, a health and safety

professional should be consulted.

EquipmentThe equipment used in abrasive blasting operations can

create physical hazards that require certain precautions. The

following are some examples of equipment commonly usedduring the abrasive blast cleaning process and the respective

precautions that should be taken during their use.

Deadman control: This is usually a spring-loaded control

located near the nozzle end of the blast hose. When de-

pressed, it starts the flow of high-pressure air and abrasive.

When released, it stops the flow. Deadman controls can be

either pneumatic (air-operated) or electric. In either case,

the control must be kept depressed by the operator for the

system to work. This prevents a nozzle from blasting the

operator or nearby workers with abrasive if dropped. Always

verify that there is a Deadman control and that it is operablebefore any work is performed.

Hoses: Hoses are subject to severe abrasion from the

high-pressure air and abrasive that moves from the pressure

vessel to the nozzle. Ruptures can cause serious injury. Meta

piping carrying abrasive also deteriorates rapidly. Hoses and

piping should be inspected on a regular basis and repaired

or replaced periodically as necessary. Hose and pipe cou-

plings also should be inspected regularly. Blast hose cou-

plings should be wired together and whip checks should be

used. Whip checks are safety cables that restrain movement



14

of the hose should the coupling connection become compro-

mised.

Pressure vessels: Pressure vessels for compressed air or

abrasive under pressure should be checked regularly be-

cause they are also subject to abrasion and deterioration be-

yond that of normal pressure vessels. Pressurized abrasivetanks must have a removable plate for internal inspection.

All vessels must conform to American Society of Mechani-

cal Engineers (ASME) boiler and pressure vessel codes.

Valves: All valves and rubber valve parts are subject to

wear and should be inspected and replaced periodically.

Fill ports: Pressure vessels for abrasive blasting should

have a funnel-shaped input that is easily accessible to the

operator so that strain caused by lifting bags of abrasive is

avoided.

Hoseline grounding: Nozzles should be grounded because

the air and abrasive can create enough friction to develop asubstantial charge of static electricity. This is most important

while working inside tanks or in other areas where there is

potential for explosion.

Personal protective equipment: In addition to respiratory

and noise protective equipment, blasters should wear ap-

parel to prevent damage to their skin from abrasive blast-

ing and ricochet. Such apparel includes safety footwear or

toe guards, coveralls, leather or rubber capes, and gloves.

Pant and sleeve cuffs should be secured with tape or other

suitable fasteners. These clothing rules are most difficult

to enforce during hot weather, but despite the discomfort,they still must be enforced. Protective equipment should be

inspected daily and repaired or replaced as necessary. Clean

storage areas should be provided for respiratory protection

and protective apparel. It is most important that blasters

receive proper training in the use of personal protective

equipment.

SummaryWhen performing abrasive blasting, safety considerations

must be given to hazards including dust, noise, and equip-

ment. Once the hazards are determined, procedures for

personnel protection can be developed. In addition to being

provided with personal protection, workers must be properlytrained in the use, inspection, and maintenance of equip-

ment.

Procedures to control exposure to health and safety

hazards must conform to the OSHA regulations that govern

blasting operations. Additional regulations from state or

local jurisdictions may be in force. Twenty-three states have

their own version of OSHA, and their regulations are at least

as strict and, in some cases, stricter than federal OSHA regu-

lations.

This article should not be considered a comprehensive

analysis of abrasive blasting health and safety. When thereis any doubt about the nature of the hazard or how to protect

workers, assistance should be obtained from a health and

safety professional, typically someone who is a Certified

Industrial Hygienist or a Certified Safety Professional or pos-

sesses a degree from a related field of study.

References:1. Meeker, John D., Pellegrino, Anthony, and Susi, Pam,

Comparison of Occupational Exposures Among Painters

Using Three Alternative Blasting Abrasives. Journal of

Occupational and Environmental Hygiene, Volume 3, Issue 9(September 2006): pp. D8084.



15

An air abrasive blast equipment system is composed of

several major components, including the following.

Air Compressor

Blast Pot (Pressure Blast Tank)

Abrasive (Blast Media)

Blast Nozzle

Moisture Trap

Deadman Switch

Blast Hood

Interconnect Hoses

Lets take a look at each to see how they work together toprovide an efficient abrasive blast system.

Air CompressorThe air compressor provides high-pressure air for the blast-

ing operation. This machine takes in atmospheric air at 14.7

psi and compresses it to a pressure several times higher,

usually about 120 psi. The heat generated through compres-

sion is somewhat dissipated by an air intercooler. The air

then passes through moisture and oil separators to make it

dry and oil-free as it exits the compressor.

Air compressors are generally identified by output capaci-ty, such as 250 CFM, 325 CFM or 750 CFM. CFM means cubic

feet per minute, which is how the volume of pressurized air

is measured. The power to run a compressor is usually pro-

vided by an internal combustion engine (gasoline or diesel)

or by an electric motor. Selection of a power unit is generally

dictated by the area where blasting is to be done or by the

availability of utilities.

Before starting the compressor, remember to:

check the engine oil level;

check the coolant level; and

check the belts and hoses for leaks or defects.

Blast PotThe blast pot (Fig. 1, p. 17) is a coded pressure vessel gen-

erally referred to as a pressure blast tank (PBT). Because it

is a pressure vessel, it must have a stamp on it showing that

it has been pressure tested. The PBT is further identified by

size. For example, it may be called a 6-ton PBT or a 6-sack

pot (based on silica sand), referring to the amount of abra-

sive it can hold. During operation, the blast pot is pressur-

ized and feeds abrasive into the air stream.

Fig. 1: Blast pot

Courtesy of Axxiom Manufacturing

Setting Up Air AbrasiveBlast EquipmentEditors Note: This Applicator Training Bulletin is an

update of a previous article written by Joe Fishback of

Custom Blast Services Inc. It was first published in the

November 1989 JPCL and has been updated for this issue

by Bill Corbett and Stan Liang of KTA-Tator, Inc.



16

Abrasive (Blast Media)While not usually thought of as abrasive blast equipment,

not much happens to the surface without the abrasive.Abrasives are generally categorized as expendable (one-time

use) or recyclable (multiple uses). The type, size, shape and

hardness of the abrasive all affect productivity as well as the

depth and shape of the surface profile or anchor pattern. The

cleanliness of the abrasive is just as important as the clean-

liness of the compressed air used to propel the abrasive. A

vial test is performed on new or recycled abrasive prior to

use. The abrasive is tested for oil according to ASTM D7393

and conductivity according to ASTM D4940. According to the

SSPC standards, abrasives cannot contain any visible oil and

cannot have a conductivity that exceeds 1,000 S.

Blast NozzleThe blast nozzle is a small but important piece of the blasting

equipment. It is the last item to exert influence on the blast

media. Nozzles are identified by their shell composition, their

lining composition, the size of the orifice and length (for ex-

ample, aluminum shell with tungsten lining, size #7, short).

The orifice size number relates to the size in 116-inch units

(#7 = 716-inch). The size of the nozzle has a bearing on the

amount of air and abrasive used and on the amount of work

completed. The larger the size of the nozzle, the greater theconsumption of supplies. Nozzles are chosen for the work to

be performed.

Moisture TrapThe moisture trap is a device that allows the compressed

air to shed water. As the air is compressed, heat is gener-

ated. As this hot air passes through the heat exchanger to

lower the air temperature, water in suspension (humidity) is

condensed. Generally, a compressor is fitted with a moisture

trap. This first trap catches most of the water. However, as

the compressed air continues to cool, additional moisture

condenses in the bull hose. This remaining moisture is

trapped by the moisture separator just before it enters the

PBT. This trapping is done either with a centrifuge-style

separator or with a replaceable filter element-style separator

Generally, it is necessary to leave an air bleed valve open inthe bottom of the moisture trap when blasting to allow the

moisture to be expelled.

Deadman SwitchThe deadman switch (Fig. 2), either pneumatic or electrical,

allows the blaster to have remote control over the pressur-

ization of the blast hose. With pneumatic operation, this is

accomplished when pressure through the deadman switch

closes the air control valve and opens an escape valve. This

prevents air from entering the PBT and at the same time,

it depressurizes the PBT. Electrically operated systems usepinch valves to stop the flow in the blast hose. With electri-

cally controlled systems, the PBT is always pressurized when

the bull hose is connected and pressurized.

The primary purpose of the deadman switch is safety. It

provides a means to stop the discharge of abrasive from the

nozzle when a safety hazard arises. The fact that it allows the

blaster to start and stop work at his discretion is a secondary

purpose.

Blast Hood

The blast hood (Fig. 3) is a piece of safety gear that providesa degree of comfort to the blaster as well. This hood is gen-

erally a reinforced plastic shell with a replaceable skirt that

covers the torso of the blaster. It has a double-faced shield of

clear plastic for eye protection and an air feed line to provide

positive pressure under the hood. The positive air pressure

under the hood prevents the entrance of harmful blasting

dust and abrasive. Air coolers are also available. If the air is

coming from a diesel compressor, an air purifier and carbon

monoxide monitor are required.

HosesHoses vary in size depending on the work to be performed,

available air capacity, distance to work area and other con-

siderations.

The first in the sequence is the bull hose. This is generally

a short hose less than 50 feet long, with an internal diam-

eter (ID) of approximately 2.5 inches or less that provides

passage of air from the compressor to the PBT.

The next hose is an air-line with an approximate ID of 0.75

inches or less that provides air first to a moisture trap and

then to the blast hood. The section between the moisture

Fig. 2: Multi-colored deadman switches. Courtesy of SAFE

Systems, Inc.



17

trap and the hood is smaller, down to 0.25-inch ID.

Control hoses can be down to 0.20-inch ID and are gener-

ally duplex (dual-line) hoses. They run from the control valve

on the PBT to the deadman switch and back to complete the

circuit when the blaster is ready to commence work. Includ-

ed here is the electrical wiring necessary if the deadman iselectrically operated. It generally operates from a 12-volt DC

source such as the compressor power units DC system.

The last hose in the circuit is the blast hose. It is a thick-

wall, wire-reinforced hose designed and constructed to

contain the high-pressure air (up to 120 psi) and abrasive

mixture that moves from the PBT to the blast nozzle. The

blast hose is constructed in three layers: an inner wearing

lining, a conductive layer and an outer wrapping. Abrasive

passing through a blast hose builds up static electricity.

The conductive layer is needed so the whole system can be

grounded. As a general rule, the hose should be three timesthe ID of the nozzle orifice; ideally, 1.25 inches to 1.5 inches

for optimum production.

Setting Up the SystemWith the major sub-assemblies identified, we can now set

up our blasting equipment. Position the compressor upwind

from the work area so that airborne grit does not enter the

cooling or air intake systems. The compressor should be

level so that the oil and moisture separators can function

efficiently. The power units lubrication system also depends

on the compressor being level. After fluid levels (oil, coolantand fuel) have been verified and topped off, the compressor

is ready to start.

The bull hose should be laid out with no kinks and a min-

imum of bends. Prior to making connections at the com-

pressor and PBT, the sealing gaskets should be examined

for tears, cracks or other sealing problems. As soon as the

connectors have interlocked, a safety pin or wire should be

inserted to prevent accidental separation of the joint. If this

separation should occur, there is great potential for per-

sonnel or property damage as the hose whips around. The

hose should be examined for damaged locking lugs, missinggaskets, soft spots, torn covers or other damage.

If any defects are observed, consideration should be given

to replacement of the worn or damaged part. If all appears

in good condition, make the connections at the compressor

and PBT moisture trap.

The next step is to lay out the blast hose utilizing the same

inspection procedures used for the bull hose and fittings. If

all is in good shape, connect the selected nozzle and pin all

fittings.

When the blast hose connection is complete, you can run

the hose for the deadman switch. The fittings on the ends of

this hose are brass, male/female and threaded. It is neces-

sary to use the proper-sized wrench to prevent damage to

the brass hex surfaces. As the hose is installed, care should

be taken to lay the hose parallel to the blast hose. The

control line should also be secured to the blast hose by tape

or other means to minimize possible damage to this less du-rable hose. This is important because air leaks in the control

line will not allow the control valve to pressurize the PBT and

thus no blasting takes place. The threaded fittings should be

tightened securely but not over tightened.

Now, go back to the air source for connection of an air-line

to feed the small moisture trap for hood atmosphere. These

fittings are usually 0.75-inch crows foot, quick-disconnect

fittings. Inspection of hose gaskets and locking lugs is once

again necessary. Be certain to pin all quick-disconnect crows

feet.

Fig 3: Blast hood

Courtesy of Bullard



18

The hood atmosphere line is the last hose to be hooked

up. This hose has brass screwed fittings similar to those on

the control line. The same care in hook-up should be exer-

cised, with particular attention to preventing entry of debris.

Now, with all hoses connected to their respective fittings,

you are ready for pressurized air. Close all air outlet valveson the compressor. Press the shutdown bypass button

as well as the start button. The compressor should start

and run. After the temperature moves up to the operating

temperature, it is time to press the service air switch. At this

time the air pressure gauge should register approximately

110120 psi. If the reading is higher or lower, adjustments

should be made before beginning the blasting operation.

When the compressor stabilizes at working air pressure,

slowly open the valve to furnish hood atmosphere air. After

the quality (oil and contaminant-free) and quantity of this air

are verified, slowly open the valve for the bull hose. Thereshould be no air escape except at the moisture trap bleeds.

If air leaks are present, they should be repaired. The PBT can

now be filled with abrasive.

The blaster should be clothed with sturdy shoes or boots,

heavy pants, a long-sleeved heavy shirt and leather gloves

for protection from bounce-back of abrasive. When the blast-

er has been properly suited up, he or she can check opera-

tion of the blast equipment. He or she does this by opening

the deadman valve to pressurize the PBT and thus force

a quantity of abrasive to enter the air stream to the blast

hose.Adjustments in the amount of abrasive delivered to the

nozzle can be made with an abrasive valve located close

to the bottom of the PBT. Enough abrasive to do the work

should be delivered, but not so much as to slow the impact

or choke the blast hose or nozzle.

To assure the quality of cleaning, two important checks

should be made. The first is a compressed air cleanliness

test, also known as a white rag or blotter test. This test

determines if the blast air is free of moisture and oil as it

is delivered to the nozzle. The abrasive valve is closed to

prevent abrasive from entering the air stream. A white ragor blotter (called an absorbent collector) fastened to a

rigid backing is then positioned in the air stream within 24

inches of the nozzle. A non-absorbent collector such as rigid

transparent plastic may also be used. After a minimum of

one minute, the collector is removed and examined for oil or

moisture contamination. If evidence of oil is present on the

collector, adjustments must be made to the system, possibly

by service personnel from the supplier of the compressor.

The second test measures nozzle pressure. This measure-

ment is taken with a needle pressure gauge. The needle

is inserted into the blast hose in the direction of air andabrasive flow. This insertion takes place close to the nozzle

with both the air and the abrasive flowing. Nozzle pressure is

read directly on the face of the gauge. Optimum blast nozzle

pressure should be approximately 100 psi for productive

work. Pressures lower or higher than 100 psi may improve

productivity depending on the abrasive being used.

With proper setup of equipment and a thorough knowl-

edge of good safety practices, your job should be safe and

trouble-free.



1

T

hese are dreaded words a contractor hates to hear,

whether they come from a third-party inspector or from

the contractors own QA/QC manager. Abrasive blasters

have been hard at work all morning. Just before lunch-

time the blasters shut down. The spent blasting grit andthe old coating (and rust) blasted from the surface have been

hurriedly gathered and removed, the blasted surface blown

down or vacuum cleaned to remove blasting dust, and the

inspector summoned.

The inspector or QA/QC person is not the bad guy he

or she is simply following his or her interpretation of the

project specification and the industry standards used to write

the specification. If there has not been sufficient discussion

and agreement about standards and interpretation during

the pre-bid and pre-job conferences, the QA/QC person, the

third-party inspector and the contractors site superintendentmay have significantly different opinions of what meets the

project surface preparation specification.

This article discusses potential ambiguities in visual

surface preparation standards and provides insight into

preventing disagreements between owners, inspectors and

contractors, and avoiding delays and costly reblasting.

SSPC-SP 5/NACE No. 1, White Metal Blast CleaningSurface preparation standards are almost entirely visual.

SSPCs definition of a White Metal Blast Cleaned surface

(SSPC-SP 5/NACE No. 1) reads as follows:

2.1 White Metal Blast Cleaned Surface: A white metal

blast cleaned surface, when viewed without magnification,

shall be free of all visible oil, grease, dust, dirt, mill scale,

rust, coating, oxides, corrosion products and other foreignmatter.

That should be easy and straightforward its white or

it isnt. But its not always that simple. The standard states

that the the surface needs to be white when viewed without

magnification. Does that mean the inspector has a right to

get his nose half an inch from the blasted surface, or should

he view it from a more normal range? How visible are

the visible contaminants and foreign matter? What about

non-visible contaminants?

2.1.1: Acceptable variations in appearance that do not

affect surface cleanliness as defined in Paragraph 2.1 includevariations caused by type of steel, original surface condition,

thickness of the steel, weld metal, mill or fabrication marks,

heat treating, heat-affected zones, blasting abrasives, and

differences because of blasting technique.

Acceptable white metal prepared steel surfaces may

in fact be several shades of gray, some of them because of

abrasive blasting, some of them in spite of it, and white

metal is a somewhat of a misnomer.

7.4: Immediately prior to coating application, the entire

surface shall comply with the degree of cleaning specified...

Abrasive blasting structural beams

for a coastal petrochemical

project. All photos courtesy of

Mobley Industrial Services Inc.

By Peter Bock

CorrLine International

Surface Preparation:

Adventures in Frustration

No, its just not

good enough.Youll have to

reblast.

19



20

Any visible rust that forms on the surface of the steel after

blast cleaning shall be removed by recleaning

If the inspector thinks that the job has not been done well

enough, the contractor will have to reblast the unaccept-

able areas. Because the contractor has already set up forpainting to ensure no more deterioration immediately prior

to coating application, all that effort is wasted. Blasting

equipment has to be brought back in, spent abrasive has to

be once again gathered and removed, the surface has to be

vacuumed or blown down again and the dread of dreads

the inspector has to be called back to re-inspect. In the

meantime, other previously acceptable areas of blasted sur-

face may have deteriorated, so from a practical viewpoint,

if the inspector turns down a portion, reblasting or at least

resweeping the entire shifts work is often the most cost-ef-fective option.

White Metal Blast

Cleaning, is usually

specified only for tank

and vessel lining and for

critical exterior surfac-

es. The costs and the

perfection required are

too high for most coating

projects and SSPC-SP 10/

NACE No. 2, Near WhiteMetal Blast Cleaning,

or SSPC SP-6/NACE No.

3, Commercial Blast

Cleaning, are specified

instead. Near White

Metal Blast Cleaning allows 5 percent of a unit area of

abrasive blasted steel surface to be less than white metal

and Commercial Blast Cleaning allows for 33 percent. For

both standards the less-than-white areas can have only ran-

dom staining consisting of light shadows, slight streaks or

minor discolorations caused by stains of rust, stains of millscale, or stains of previously applied coating.

A unit area is defined as a 3-inch-by-3-inch square.

Therefore, if an inspector finds a 3-inch-square area in which

more than 3 square inches are randomly stained, the area

fails Commercial Blast. The math is easy; the stains are

not.

When is a Stain Not a Stain?Although the SSPC Protective Coatings Glossary defines

a stain as An area of a surface which, when compared to

adjacent areas, has an equal surface profile but is discolored(usually darker) with a material having no apparent volume;

upon visual assessment, confusion remains about what

constitutes a stain versus actual rust or mill scale left on the

surface. How light, slight or minor do the light shadows,

slight streaks or minor discolorations specified in SSPC-SP

6/NACE No. 3, Paragraph 2.1 have to be to pass, especially

since the following paragraph (2.1.1) of the specification

allows the same steel color variations as for White Metal?

Just as for White Metal Blast, Near White Metal

and Commercial Blast require that immediately prior to

This blaster is using medium-grade garnet abrasive to obtain

a Commercial Blast Cleaned surface (SSPC-SP 6) and a 2-to-

3-mil anchor profile.

Beam end area has been blasted to a "Near White Metal"

finish (SSPC-SP 10).

An area of staining or discolor-

ation in SSPC-SP 10 blast.

Does it pass or fail?



21

coating application, the entire surface shall comply with the

degree of cleaning specified. Any visible rust that forms on

the surface of the steel after blast cleaning shall be removed

by recleaning But are the stains the inspector is findingon newly blasted Near White Metal or Commercial steel

from before blasting, or are they new turning or rerusting of

the steel?

Get the PictureVisual comparison standards for acceptable quality of

dry-abrasive-blasted surfaces (SSPC VIS 1) should be avail-

able at the job site and should have been discussed and

agreed on at the pre-bid and pre-job conferences. Whether

using available photographic standards, or digital photos of

test-blasted areas done as part of the contractor bid quali-

fication or pre-job qualification, there should be a general

agreement between the owner, contractor and third-party

inspector. In advance of the project, a decision should be

reached about what constitutes acceptable visual appear-

ance of the prepared surfaces in order to conform to thespecification standard. Inspection of the days surface prepa-

ration work should be an opportunity for agreement, not a

source of frustration, confusion and conflict.

After a commercial or near white blast of aged steel in a

refinery or chemical plant environment (especially at a coast

al location where high humidity and salt in the air are almost

constant), it is often difficult to determine whether stains the

inspector finds are allowable, or a result of degradation of

the blasted surface.

According to the inspector, the most straightforward way

to tell is to let the blasted area sit a while and see if the stain-ing gets worse. From the contractors perspective, this can

be perceived as an expensive way for the inspector to force

a reblast. Using an agreed-upon visual comparison standard

up front can help to avoid disagreement.

SSPC-PA 17

Procedure for Determining Conformance to Steel Profile/Surface Roughness/Peak Count RequirementsTesting of a dry-abrasive-blasted surface for specified anchor

profile can be a non-visual, quantifiable test. The traditional

visual comparator test has been superseded by the useof profile replica tape, or of depth micrometer testing of the

profile. Both replica tape and depth micrometer testing are

quantitative measurements, but they measure only small

samples of the entire prepared surface. The number of

required anchor profile tests should follow standards as a

minimum or should be specified and agreed upon at the pre-

job conference. Depth micrometer testing is highly accurate

but measures only one pit per reading, so multiple groups

of readings must be done to assure accuracy. The project

specification should clearly state the type and frequency of

blast profile tests required. If newly-abrasive-blasted steel could be stabilized as it

was blasted and without degradation, the inspector could

inspect it and pass or fail the actual preparation work itself,

rather than the preparation that has subsequently been

affected by environmental conditions.

The presence of salts on White Metal blasted steel sur-

faces has been known since before coating inspectors were

assigned CIP numbers. When the author was first learning

the offshore oil field maintenance painting business in the

late 1970s, there was already a primitive test for salt residue

Newly-blasted support beam unit has flash rusted badly after

an unexpected rain shower.

Light flash rusting on steel dry blasted to SSPC-SP 10. This

area needs to be reblasted.



22

contamination on newly-blasted-steel surfaces. The original

field salt test consisted of licking the newly-blasted steel.

At that time the blasting medium was silica sand, and the

steel looked clean when viewed without magnification, so

licking it was safe and sanitary, but you could always taste

the salt. And, of course, the spot you licked immediately

flash rusted. Then the contractor painted over all that salt,

because there was no cost-effective way of removing it.

SSPC Guide 15Field Methods for Extraction and Analysis of Soluble Salts

on Steel and Other Nonporous Substrates

Since then, much more sanitary and quantifiable tests have

been developed for measuring salt residues left on new-

ly-blasted surfaces. Different types of salt test procedures

measure different groups of salts and it should be noted that

test results may vary, depending on the test method used.

All the tests have in common the facts that they are expen-

sive (anywhere from $10 to $40 for the test kit itself, exclud-

ing the cost of the measuring device) and they are slow,

typically taking 10 to 30 minutes per test. All of the salt testsare also handicapped by two other factors: first, they mea-

sure only a tiny area of the blasted surface, typically about

one one-hundredth of one percent, which is then assumed to

be uniformly representative of the entire prepared surface,

and secondly, they do not specifically measure iron sulfides

left on the surface, and these are one of the primary causes

of flash rerusting.

A salt test measures salt concentration on two-to-four

square inches of the prepared surface and the test results

will be representing several hundred square feet of prepared

surface or more. The project specification should include

the specific method to be used for testing for soluble salts.

It may also include the number, frequency and location of

tests. There is also a visual component structures tend

to corrode unevenly; verification tests have often shown

widely varying results, indicating that surface contaminantsare unevenly distributed on the prepared surface, tending

to cluster or aggregate. This accounts for the phenomenon

that some areas of the same abrasive blasted surface tend to

flash rust faster and more severely than others.

Both the equipment owner and a seasoned third-party

inspector may have experience indicating where the struc-

ture being prepared will tend to corrode, that is, where the

previous coating system failed the earliest or most exten-

sively. Salt tests should be specified to be taken at precise

areas which are expected to have the highest levels of resid-

ual non-visible contaminants. Without such specificity, theremay be disagreement.

Wet surface preparation methods like wet-abrasive blast-

ing or UHP water washing remove some non-visible contam

inants, but the wet prepared steel surface can quickly flash

rust as it dries. There are methods of inspecting a flash-rust-

ed surface after wet preparation, but these are also entirely

visual and are even more subjective than the staining

described in SSPC-SP 6/NACE No. 3 or SSPC-SP 10/NACE

No. 2.

The most common method of delaying flash rusting on

dry-abrasive-blasted steel is dehumidification reducingrelative humidity over the newly-blasted surfaces to a level

where an electrolytic cell does not exist and flash rusting

cannot occur.

Dehumidification (DH) for the interior of a roofed tank

being dry-abrasive-blasted is relatively simple. There are few

and relatively small openings, and the steel sides and floor

contain air and hold heat. Exterior structures can be scaffold-

ed and tented with plastic sheeting to allow for DH, but such

tenting can be leaky and requires more DH to accomplish the

originally desired results. In either case, the cost of running

the DH system continuously can be very expensive, and ifthe DH is stopped for any reason, the blasted steel can quick-

ly flash rust.

An alternative and less expensive method of controlling

flash rusting after dry-abrasive blasting is the use of a

waterborne inhibitor chemical which changes the pH of

the abrasive-blasted steel or leaves a thin residual coat on

the blasted surface, or both. The inhibitor chemical can be

sprayed onto the newly-blasted surface immediately after

blasting is completed or it can be used as a part of a wet-

abrasive-blast process.

Moderate flash rusting on steel dry blasted to SSPC-SP 10.


29/29

23

Use of an inhibitor chemical allows a contractor some

time to finish abrasive blasting and cleanup, allows the

inspector time for a thorough inspection, and in some cases,

allows abrasive blasting to continue for several shifts before

shutting down, inspecting, and coating or lining the pre-

pared surfaces.Inhibitors are frequently used during maintenance work

where the owner or inspector requires Near White Metal

appearance, but blasting and coating application cannot be

done quickly enough to prevent flash rusting. The process is

not recommended by paint companies but is frequently used

in the oil and petrochemical maintenance areas.

The dried inhibitor film is visually transparent. To the

inspectors eye, the steel appears to be Commercial or

Near White Metal Blast, (whatever the original standard

and quality of blast), so it fulfills the visual standard.

A third, relatively new method for controlling flash ruston abrasive-blasted steel is a proprietary waterborne pas-

sivation process. Unlike inhibitors, which must be applied

before any flash rusting occurs, the passivation process

claims to remove flash rust, restoring prepared steel to its

White Metal stage. Visual inspection and salt testing after

the passivation process are the same as for newly dry-abra-

sive-blasted steel.

ConclusionSurface preparation is the first and sometimes the most

important part of a successful industrial coating or liningproject. Unfortunately, specification standards for surface

preparation are almost entirely visual and can be somewhat

subjective. After dry-abrasive-blast-surface preparation,

properly prepared surfaces can quickly degrade from their

initial state on completion of blasting, and need to be quickly

inspected, approved and coated.

Field-usable salt contamination tests can determine the

presence of non-visible contaminants on visually-acceptable,

prepared surfaces, but the tests available today are expen-

sive, slow, and measure too small of a percentage of the

prepared surface to be completely reliable. Flash rusting of a newly-abrasive-blasted surface can be

prevented by dehumidification, which keeps humidity at

the bare steel surface below a level where it can act as an

electrolyte, by the use of inhibitors, or by a steel passivation

process.

Whichever method is used, determination of the speci-

fied level of surface preparation is predominantly a visual

process. To prevent disagreements, delays, frustration and

costly reblasting; the end user, contractor and third-party in-

spector should agree on visual acceptance standards before

surface preparation begins. The best way to reach agree-ment is to use visual samples, preferably photos of accept

able surface preparation samples, available to all parties at

the job site.

About the AuthorPeter Bock is vice president and technical service manager

for CorrLine International in Sugar Land, Texas. He is a U.S.

Air Force veteran and has degrees

from Tulane University and the

University of Northern Colorado.

Bock has 37 years of experience withsales, management and technical

service in oilfield and petrochemi-

cal heavy-duty coatings in the U.S.,

Canada, Mexico, Venezuela, Indone-

sia, and Taiwan. He has experience

with on- and offshore production,

drilling and workover rigs, shipyard work, natural gas and

LNG, pipelines, terminals, refineries, and chemical plants.

He is a specialist in elevated temperature systems and CUI

mitig