Sasol Technology Work Instruction for:
Sasol Technology Commissioning ManualCleaning of process
equipmentQMS / 360P/Volume 4.5, Rev 1Issued by: Commissioning
EngineeringApplicable to: Internal and external to Sasol
TechnologyDocument Control Status: Approved Process Type: Mandatory
Key Words: cleaning, washing, steaming1 Purpose (of this
document)The purpose of this mandatory procedure is to describe the
techniques and procedures to clean process equipment during the
initial operations of a plant.2 Scope
This procedure is applicable to:all process lines;all utility
lines;vacuum systems;steam boiler;oil systems;oxygen systems;
andprocess equipment.3 Revision Description
This document has been rewritten to be in line with the new
format for QMS documentation.4 Approvals
Proposed:SIGNED
09/09/2009
Andrew Oosthuizen
Chief Commissioning EngineerDate
Recommended:SIGNED
09/09/2009
Dirk Bosch
Principal Commissioning EngineerDate
Approved:SIGNED
09/09/2009
Richard Brink
Manager Commissioning EngineeringApproved and Effective Date
Any comments and proposals for revisions or additions to be
directed in writing to:
MANAGEMENT SYSTEMS [email protected] 4687
Table of contents
Page11Purpose (of this document)
12Scope
23Revision Description
24Approvals
55Purpose
56General precautions
56.1The following precautions are recommended
77Flushing
78Rumbling flushing
89Blowing
89.1Air blowing general
99.2Direct air blowing
99.3Accumulation air blowing
1010Steam blowing
1010.1General
1310.2Steaming
1410.3Fixed program
1410.4Target plate blowing
1511Acid cleaning or pickling
1511.1Chemical cleaning
1811.2Chemical cleaning precautions
1812Degreasing
1812.1Degreasing theory
2013Hand cleaning
2014Pigging
2115Sand blasting
2216Cleaning of oxygen systems
2216.1Preparation
2216.2Cleaning
2316.3Mechanical cleaning
2316.4Aqueous detergents
2416.5High pressure hot water cleaning
2416.6Solvent cleaning
2516.7Inspection methods
2616.8Acceptance criteria
2717Generic machine precautions
2718Appendices
2819Acknowledgements
2820Review Cycle
29Appendix A: Comparisons of cleaning methods
31Appendix B: Definition of cleaning classes
32Appendix C: Cleaning Decision Tree
5 Purpose
5.1 During manufacturing, construction and pre-commissioning of
equipment, the surfaces of the equipment is exposed to the
environment. This may cause the formation of scales, mildews and
rust. 5.2 The manufacturer of the piping or equipment may also
apply surface coatings to protect the surfaces against exposure to
the environment. 5.3 These contaminants as well as construction
debris may result in the contamination of processes, fouling and
failure of equipment and thus need to be removed prior to
commissioning.
5.4 Several methods exist for the cleaning of equipment and need
to be used in conjunction with each other and correctly to provide
the required result. These methods include the following:a
Flushing
b Air blowing
c Steam blowing
d Acid Cleaning
e Alkaline Cleaning
f Hand cleaning and
g Pigging
h Sand Blasting
i Cleaning Oxygen Systems
5.5 These methods will be discussed in detail in the following
sections 6 General precautions
6.1 The following precautions are recommended
6.1.1 For cleaning of process systems, all equipment that can be
damaged or fouled during the cleaning process must be removed.
These include dosing points, flow meters, injectors etc.
6.1.2 All equipment that restricts the free flow of the cleaning
medium should be removed from the system prior to cleaning. These
include orifice plates.
6.1.3 All equipment that will be exposed to pressure above their
design pressure during cleaning should be removed or isolated
6.1.4 Systems being cleaned should not be exposed to pressures
and temperatures above their design conditions
6.1.5 Cleaning methods is intended to remove foreign objects
from system, thus ensure adequate free space in front, around and
below the point where these objects may exit.
6.1.6 Equipment material of construction should be verified as
compatible to the chosen cleaning medium. This include valve
internals, filter cartridges, packing, screens and meshes.
6.1.7 At all times wear the appropriate personal protective
clothing and equipment.
6.1.8 Within existing facilities or where the owner has taken
care, custody and control of the facility a work permit is required
for all cleaning work.
6.1.9 Ensure all persons involved are trained and competent to
do the work required and operate the applicable equipment
6.1.10 Notification high pressure water cleaning in progress
must be placed outside the fence around the work area where
applicable.
6.1.11 Working area must be fenced with one entrance.
6.1.12 All high pressure connections must be fitted with anti
whip devices.
6.1.13 Ensure that all equipment is in good and safe condition
for operation. Plant Supervisor must complete equipment inspection
check list in accordance with SSP S-011 1 before any work can
commence on the plant.
6.1.14 If equipment is not used correctly injuries can result
from:
a hoses coming loose;
b pipes being blocked which may rupture under pressure;
c high pressure water;
d slipping / tripping; and
e if pressure is not released on completion.7 Flushing
7.1 Flushing is the process whereby the kinetic energy of moving
water is used to remove loose dirt, construction debris and foreign
objects from piping. The kinetic energy can be achieved by means of
gravity or by pumping the water through the system
7.2 Flushing is normally used in applications were fluids are
used in the process application and water will not have an adverse
affect during commissioning and start-up.
7.3 Flushing is effective for piping diameter less than 250mm
and a minimum flow velocity of 4 m/s is recommended.7.4 In the case
where water movement is provided by pumping, the pump should be
protected from dirt and foreign objects by installing a 20 60 mesh
or strainer on the suction side of the pump.
7.5 For flushing austenitic stainless steel, the water used for
flushing should not contain more than 30 ppm chloride ion. If the
water used does contain more than this amount of chloride, it
should be flushed with demineralised water; alternatively the
piping should be flushed with a neutralizing solution of sodium
nitrate. A solution of 4ppm sodium nitrate for every 1 ppm chloride
is recommended.
7.6 Piping should be thoroughly drained and dried after flushing
and it is recommended that an air connection be provided to dry the
system of free water. This is to prevent excessive rust formation
in the piping after flushing.8 Rumbling flushing
8.1 Rumble flushing or air rumbling is the process where water
is introduced into a system or pipeline, and then under controlled
conditions either air, nitrogen or steam can be introduced to
increase the effectives of just straight forward flushing.
8.2 The same precautions as with flushing should be followed
with the addition the system being flushed should be properly
secured as rumbling my cause additional vibrations with the system
being cleaned.
9 Blowing
9.1 Air blowing general
9.1.1 Air blowing is normally used in process application which
is gas based and the introduction of water into the system may lead
to mal-operating during commissioning and start-up.
9.1.2 Larger line sizes can also be cleaned with air blowing
compared to water flushing and is dependent on the availability of
blowing medium.
9.1.3 For blowing it is recommended that a flow of 35 60 m/s be
achieved for effective blowing.
9.1.4 Air or nitrogen can be used as the blowing medium
depending on the availability and the process requirements.
9.1.5 If Air is used, the following is applicable:
a Air needs to be readily available.
b If not, compressors will be needed.
c Normally at atmospheric humidity and thus contains water
vapour.
d Air can be heated to reduce moisture content.
e Air can be dried using desiccants.
f Air should be oil free.
9.1.6 If nitrogen is used, the following is applicable:
a Nitrogen needs to be dry and oxygen free.
b It must be available in remote location via tankers.
c Large volumes can be maintained through vaporization rigs
d Safety precaution during blowing must be strictly
administered.
9.1.7 Two methods of blowing are normally used namely:
a Direct blowing
b Accumulation or kinetic blowing
9.2 Direct air blowing
9.2.1 During direct blowing, the process equipment or piping is
connected directly to a continuous constant supply of compressed
medium i.e. air or nitrogen. This can be a supply from a utility
main, permanently installed compressor in the process or a
temporary compressor.
9.2.2 The following precautions should be followed when direct
blowing is used:a Nitrogen is heavier than air and displaces it.
Sufficient space around the exit point is required for the nitrogen
to dissipate into the air.
b Due to the large amount of kinetic energy used in blowing,
foreign objects tend to exit the process equipment at high speed.
The area in front of the exit point should be kept clear or a solid
barrier installed.
c Blowing is associated with excessive noise. The area should be
barricaded and personal noise protection used.
9.3 Accumulation air blowing
9.3.1 Accumulation blowing (kinetic blowing) is used were a
limited amount of air or nitrogen is available or in larger line
sizes where the available air supply is not sufficient to obtain
the velocities required.
9.3.2 The method uses the theory of gasses ability to store a
large amount of energy though compression and converting it into
kinetic energy when suddenly releases.
9.3.3 The method entails the initial compression of the system
to be blown with the blowing medium and then suddenly releasing by
means a valve or bursting disk.
9.3.4 Two methodologies are normally used, namely:
a Full system compression
b Accumulator firing compression
9.3.5 Full system compression entails the full system to be
compressed with a release mechanism installed on the exit point. I
bursting disk is normally used. This method is recommended for
large, long piping sections as the amount of energy that can be
stored is proportional to the system size.
9.3.6 Accumulation compressor entails the use of a drum or
accumulator that is installed at the back end of the system,
charged with the blowing medium and the released or fired into the
system by means of a release mechanism. A fast acting valve is,
i.e. ball valve, is recommended. The method is recommended for
smaller, shorter systems, as the amount of energy that can be
stored is proportional to the size the accumulator used.
9.3.7 An air pressure of between 2 and 3 bar gauge is sufficient
to blow a system clean but 3 to 4 blows is normally required.
9.3.8 The following precautions should be followed when
accumulation blowing is used:
a Nitrogen is heavier than air and displaces air. Sufficient
space around the exit point is required for the nitrogen to
dissipate into the air.
b Due to the large amount of kinetic energy used in blowing,
foreign objects tend to exit the process equipment at high speed.
The area in front of the exit point should be kept clear or a solid
barrier installed.
c Blowing is associated with excessive noise. The area should be
barricaded and personal noise protection used. An explosion like
noise is generated by the sudden release of air and good
communication to all relevant parties is recommended.
d Protect all windows in the close vicinity of the blowing
activity as the shock wave generated may shatter them.
e Never pressurize the system more than the design pressure of
the system.f Accumulation blowing induces large forces on the
piping system that may result in it jumping or kicking. The design
of the system and supports must be verified to support the forces
induced by accumulation blowing. Additional support, kick-blocks
and anchors are often required.10 Steam blowing
10.1 General
10.1.1 Steam blowing is generally used for the cleaning of steam
utility piping and steam process piping.
10.1.2 The system must be designed to handle the temperature and
consequent expansion to utilise this method.
10.1.3 The method uses the combination of kinetic and thermal
energy of the steam to remove debris from the line as well as to
strip rust and scale from the internal surface of the pipe.
10.1.4 In order to ensure the effective cleaning of pipe
internal surface a series of thermal expansion cycles are required
to loosen the impurities.
10.1.5 A series of heating and cooling cycles are used to ensure
the thermal expansion and contraction of the pipe.
10.1.6 Steam from a main supply or temporary boiler can be used
for this procedure.
10.1.7 This method requires the repetitive throttling of the
steam flow through or into the system to be cleaned and it is
recommended that a sacrificial valve or a throttling glove valve be
in stalled to regulate the flow.
10.1.8 After blowing, the valve, or internals, should be
replaced. A bypass valve a of the line size being cleaned is
recommended for effective heating of the line.
10.1.9 Two methodologies can be used to determine the amount of
steam required for blowing:
a Mass- flow criteria
b Disturbance factor criteria
10.1.10 Mass flow Criteria
The mass flow criteria state that the mass flow used for blowing
the system, should be equal to the mass flow in the system during
normal full load operation
10.1.11 Disturbance factor criteria
The concept of disturbance factor is to pass steam through the
line so as to carry the debris more effectively than would be
accomplished by steam flow at normal full load requirements. This
results in the need for steam blowing with greater kinetic energy
than that of the normal operating condition.
The disturbance factor is the ratio:
This can be expressed as:
Where V is the specific volume of the steam and F is the mass
flow rate of the steam.
Subscript 1 refers to the blowing condition, and subscript 2
refers to the normal maximum load condition.
10.1.12 The ratio, sometimes also called the shifting factor,
should be greater than one.
10.1.13 Experience has shown that a line blown with a
disturbance factor of 1, 5 or greater is well cleaned, once
acceptable target plates have been obtained. The disturbance factor
must be assessed just downstream of the throttling valve, or at the
initial point of cleaning.
10.1.14 The following precautions should be noted of during
steam blowing:
a A thorough potential deviation analysis (PDA) should be done
on each steam blowing application to identify all the relevant
risks and develop mitigating actions.
b Sufficient size drains should be installed on the steam piping
to remove solid foreign objects. On larger lines it is recommended
that the entire line be visually be inspected prior to blow to
ensure it is free from large foreign objects. Failure to do so
might lead to the system having to be cut open, cleaned and
re-welded or fitted to remove the objects.
c Remove all condensate traps prior to blowing the system.
d Trap systems should be provided with throttling globe valves
to control the steam escaping through the traps during the heating
cycle.
e Thermal expansion should be monitored during the first heating
and cooling cycled and verified with the design and by site
inspection to confirm expansion slide plates remain on their
supports. The system should be heated to full design temperature to
fully evaluate the thermal expansion.
f All scaffolding or temporary platforms on or close to the
system being blown should be removed. It is recommended that the
whole system be inspected prior to blowing for any equipment that
might limit the movement of the system
g Considerable noise generation is normally associated with
steam blowing. A silencer arrangement, with particle al screen,
should be used to limit the noise generated. Such a silencer should
be securely mounted on an engineering approved support or base.
Silencers repeatedly used for such applications, should be
regularly inspected for cracks on the internals. It is recommended
that such silencers be inspected by approved inspection authority
prior to each application.
h Lagging should be installed on the steam line prior to
blowing. This will not only ensure the safety of the personnel but
also ensure effective heating up of the system. On long piping
section is almost impossible the heat the piping to design
temperature without lagging being installed as it is part of the
design intent.
i For lines blown in opposite directions than normal process
flow, the thermal expansion design should be verified for the flow
direction during blowing.
j Heating up should be done slowly through the steam traps
bypasses in order to effectively drain all condensate and thus
preventing water hammer.
k The line should always be kept open during the cooling down
cycles to ensure that a vacuum does not form which can result in
the collapse of the piping or associated vessels.
l After the full cleaning cycle the line should be placed in
service as soon as possible or preserved under nitrogen
blanket.
m Valves in the system should be heated fully and the
differential pressure equalized prior to being operated. During
blowing, these valves should be fully open or fully closed to
ensure that they are not damaged.
1.1.2 Three methodologies can be used for steam cleaning:a
Steaming applicable to utilities lines and steam tracing
b A fixed program for heat exchangers, steam injectors,
atomizers, vessels, drums, de-super heater and any other steam
equipment using steam or generating steam that will NOT BE USED IN
TURBINE APPLICATIONS
c Steam blowing to target plate specification for steam systems
that generate on transport steam to turbines applications
10.2 Steaming
Steaming entails the single blow of a system with steam until it
is free from debris and foreign objects.10.3 Fixed program
10.3.1 Fixed program entail the blowing of the system in three
consecutive cycles up to, or as close as possible, to design
temperature.
10.3.2 Blowing for 10 15 minutes at this temperature and then
cooling down to a surface temperature at least 200oC below the
blowing temperature.
10.3.3 The delta temperature between hot and cold stages will
ensure enough thermal expansion to release mill scale and rust.
10.4 Target plate blowing
10.4.1 Target plate blowing consists of blowing to a target
plate specification. This specification entails the installation of
a small metallic plate in the main steam flow, at a right angle,
and measuring the amount of impacts, caused by small debris
particles, rust and mill scale during blowing, after each blow.
10.4.2 Depending on the application various materials are used
for the target plates including:
a carbon Steel;
b stainless steel;
c aluminium; and
d brass.
10.4.3 The manufacturer of the applicable equipment that will be
serviced by the related piping will specify a target plate or
impingement specification. Such a specification should include the
following:
a Material to be used for target plate ea. Carbon steel
b Duration of impingement blow ea hour
c Area size to be inspected ea. 10cm2
d Number of raised impingement /embedded pits per area ea.
one
e Number of impingement per area ea < 2/cm2
f Acceptable size of such impingements ea < 1 mm
10.4.4 In absence of such a guarantee specification requirement,
the following is generally used for steam driven turbines:
a Stainless steel target plate, polished to mirror finish
b 15 min blow at superheated temperature
c No raised pits
d Less than1 impingement larger that 0.5 mm per square
centimetre
10.4.5 To obtain such stringent specification the following
guidelines should be followed:
a A minimum of 3 cycles of blowing is recommended before
measurement start.
b Blow at least design flow and temperature for 3 hours during
each cycle.
c Up to 10 cycles of blowing may be required to reach
specification.
d Cooling down the pipe external temperature during the cooling
cycle to below 200oC that of the external surface during blowing.
This will ensure adequate thermal expansion and contraction to
loosen mill scale and rust.
e Use of brush pigging prior to steam blowing will reduce the
blowing cycles required.
f Internal sandblasting, with fine specification sand, of
fittings prior to installation will reduce team cycles required to
reach the specification.
g Install target plates after blowing, before cooling down, to
measure specification. Condensate present in the steam during
warming up of the system from cold may also cause impingement on
the plate which will thus not be a true reflection of the surface
quality of the piping.11 Acid cleaning or pickling
11.1 Chemical cleaning
11.1.1 Chemical cleaning is reliant on the properties of some
acid chemicals to dissolve rust, slag and mill scale that forms on
the metal surface and is used in various systems:
a Compressor suction piping
b Boiler feed water systems
c Oil systems of rotating equipment
d Oxygen service systems
11.1.2 Acid cleaning is not required for stainless steel systems
care must be taken in designing the circulating system to ensure
the entire system is sufficiently exposed to the cleaning and
neutralising medium. Specific care must be taken in system where
crevices are present as it is difficult to ensure complete
neutralisation in these areas leading to corrosion.
11.1.3 Mineral acids such as hydrogen chloride or organic acid
such as citric acid is normally used, but an approved; experience
contractor will recommend the correct formulation for the specific
application.
11.1.4 Two methods of acid cleaning are generally used:
a Dipping in a solution
b Circulating a solution
11.1.5 Acid cleaning is always done in a sequence of stages. The
stages are as follows:
a Flushing
b Degreasing
c Intermediate rinsing
d Acid cleaning or Pickling
e Main Rinsing and Neutralizing
f Passivation
g Drying
h Preservation
11.1.6 Each of these steps will be discussed briefly:
a Flushing
i) Flushing with water is used to remove foreign objects, dust
and debris from the system. Excessive amounts of debris and dust
may also negatively impact on the reactivity of the acid.
ii) Flushing can also be used to test the circulation equipment
being used for the acid cleaning for effectiveness and leaks.
b Degreasing
Decreasing is used to remove excess oil, lubricant and organics
that is insoluble in acid from the system. Deceasing will be
discussed in detail in the next section.c Intermediate flushing
Flushing with water at approximately 70oC for 15 minutes will
neutralize the degreasing agent prior to acid cleaning. Full
neutralization should be tested with a pH paper test on the surface
of the piping or by measuring the pH of the flushing water.d Acid
Cleaning/Pickling
iii) The solution used can be a solution of Hydrochloric or
Citric acid at a 10% wt solution with water. A corrosion inhibitor
should be added to prevent the equipment from rusting as it is
removed from the bath or drained.
iv) The temperature of the solution should be between 60 70oC
and agitated or circulated continuously.
v) 12 hours is recommended for an exposure period depending on
the strength of the solution but 6 hours should be taken as a
minimum.
vi) The pH of the solution should be constantly monitored to the
suppliers specification and if the amount of Iron ion in the
solution exceeds 0.4% by weight, the solution should be
replaced.
vii) The solution should be disposed of in a responsible manner
after being drained
e Main Rinsing and Neutralizing
viii) The system should not be allowed to dry prior to rinsing.
Rinsing or neutralization can be done by means of flushing with
clean water or with a neutralization solution of 1% to 1.5% wt Soda
ash in water. Such solution should be at a pH of above 9 and at a
temperature of between 70oC and 80oC
ix) Circulation of the neutralization solution should be for at
least 10 minutes and the pH of the wet surface should be neutral
afterwards. pH paper can be used for this test.In complex systems,
all supply and return lines must be monitored to ensure continuous
flow through each line. Restriction in any line may lead to the
acid not being neutralised and consequent corrosion will damage
that portion of the system.
f Passivation
Passivation is done to form a protective layer of Fe3O4 on the
internal surface of the piping. This layer is normally a thin black
hard layer. Passivation chemicals are normally proprietary
solutions supplied by the contractor, but often have an amine
base.g Drying
The system should be completely dried after acid cleaning by
blowing it with nitrogen or warm airh Preservation
After chemical cleaning the system should be preserved under a
nitrogen blanket or put into service as soon as possible11.2
Chemical cleaning precautions
11.2.1 The following precautions should be followed during
chemical cleaning:
a A thorough potential deviation analysis (PDA) should be done
on each chemical cleaning application to identify all the relevant
risks and develop mitigating actions.
b Relevant and applicable safety clothing should be used at all
times
c Disposal of chemical solution should be according to the local
and company regulations
d MSDS documentation must be available for all chemicals
used.
e Material compatibility test must be done on all material in
the system to be chemical cleaned with the relevant cleaning
solutions. This includes valve internals, gasket material, busting
discs and sealants.
f Ensure that all chemical solution required are onsite and
available prior to commencing the cleaning.
g Ensure that a temporary emergency shower is available in close
proximity, during the cleaning operations
h Clearly demarcate the area in which the cleaning process take
place and regulate access to this area.
i Acid cleaning should always be done by an approved and
reputable contractor.
12 Degreasing
12.1 Degreasing theory
1.1.3 Degreasing uses the chemical theory that mineral oils and
fats can be torn off the surfaces with a caustic solution and then
be suspended in the solution while organic oils will be hydrolysed
to glycerine or aliphatic sodium salts in the same solution thus
degreasing the specific system.
1.1.4 The process is generally used to:a clean stainless steel
piping;b clean carbon steel piping prior to acid cleaning;c clean
out boiler drums; andd clean amine systems to prevent foaming
during operation.
1.1.5 The system should be thoroughly flushed prior to
commencing degreasing.1.1.6 Sodium Hydroxide or Sodium Carbonate is
generally used to perform degreasing within a solution with water
under the following conditions:a Sodium Hydroxide, 6% solution,
80oC-90oC, for 30 minutes
b Sodium Carbonate, 2% solution, 80oC-90oC, for 30 minutes
1.1.7 After degreasing the system should be thoroughly flushed
until the pH of the flushing water is below 8.5.
1.1.8 The following precautions should be followed during
chemical cleaning:a A thorough potential deviation analysis (PDA)
should be done on each chemical cleaning application to identify
all the relevant risks and develop mitigating actions.
b Relevant and applicable safety clothing should be used at all
times.c Disposal of chemical solution should be according to the
local and company regulations.d MSDS documentation must be
available for all chemicals used.
e Material compatibility test must be done on all material in
the system to be chemical cleaned with the relevant cleaning
solutions. This includes valve internals, gasket material, busting
discs and sealants.
f Ensure that all chemical solution required are onsite and
available prior to commencing the cleaning.
g Ensure that a temporary emergency shower is available in close
proximity, during the cleaning operations.h Clearly demarcate the
area in which the cleaning process take place and regulate access
to this area.
i It is recommended that degreasing be done by an approved and
reputable contractor.13 Hand cleaning
13.1 Hand cleaning is the principal of rubbing, wiping, broom
sweeping, sanding or brushing the internals of equipment, including
vessels, reactors and piping diameters larger than 600mm.13.2 The
following precautions should be followed during any hand cleaning
activity:a A vessel entry permit is required for any duty where a
person is required to stick his head into an enclosed space. All
vessel entry precautions must be adhered to during such cleaning
processes.
b Relevant and applicable safety clothing should be used at all
times.
c A standby person is required to monitor and assist the
employee executing the cleaning when required.
d Only 24V supply and lower lighting may be used in an enclosed
space.
e Continuously monitor the air quality as required by the vessel
entry permit conditions.14 Pigging
14.1.1 PIG or Pigging is an abbreviation for Pipeline Inspection
Gauge.
14.1.2 Pigging is the method generally described as the forcing
a bullet shaped object, or a pig, through the line to perform some
method of mechanical cleaning on the inside surface of the pipe.
The pig is forced hydraulically by means of water through the pipe.
Air is more commonly used.
14.1.3 Pigs are generally used in long pipelines that are
difficult to access or require large volumes of water, air, steam
or chemical solutions to clean.
14.1.4 Pigs for various duties are available, including the
following:
a Rubber pigs for water removal.
b Foam pigs for removal of foreign objects and construction
debris.
c Brush pigs for abrasive cleaning.
d Intelligent pigs for wall thickness measurements.
e Slug pigs for containing a batch or slug of chemical cleaning
solution between a set of two pigs.
14.1.5 Systems normally require some design changes to enabling
pigging to occur. This includes the following:
a Space at the start and end of the piping section for pig
launchers and pig receivers. These are normally piping sections,
bolted onto the pipe, with larger diameters than the pig it should
launch or receive and has normally a hatch or manhole to load and
unload the pigs.
b Pigging bars should be installed in equal diameters T to
direct to flow of the pig
c Design pressure of pipe section should be evaluated to
withstand the hydraulic forces.
d Piping supports should be reviewed and temporary supports
installed where required withstanding the increase vibration caused
by the pig.
14.1.6 A recommended pig velocity is between 1 and 4 m/s but
depends on the application and the pigs being utilized.
14.1.7 It is recommended that pigging be done by an approved and
reputable contractor.15 Sand blasting
15.1 Sandblasting is the method of cleaning the internal or
external service by blowing a powerful jet of abrasive material
onto the surface.
15.2 The following precautions should be followed during any
sand blasting cleaning activity:
j A vessel entry permit is required for any duty where a person
is required to stick his head into an enclosed space.
k Relevant and applicable safety clothing should be used at all
times.l A standby person is required to monitor and assist the
employee executing the cleaning when required.
m Only 24V supply and lower lighting may be used in an enclosed
space.n Continuously monitor the air quality as required by the
vessel entry permit.15.3 The following guidelines can be followed
for sand blasting cleaning:
a Sandblast the lines internally to a finish of SA2.5 and
inspect line internally with a boroscope.
b Avoid damaging the flanges when withdrawing the sand blasting
head form the pipe. Flanges faces can be taped for protection.
c Care should be taken at elbows to avoid wall thinning.
d Dry, oil free, air or nitrogen should be used to blow the grit
or aluminium oxide. Metallic shot is not recommended.
e Sandblasted surfaces should always be immediate preserved
after cleaning, as the bare metal surfaces will start to rust
immediately.
15.4 Sand blasting blowing speeds for different pipe bore sizes
is suggested as follows:
o 25 mm Blow through
p 50 mm Blow through
q 75 mm 30 seconds per meter
r 100 mm 35 seconds per meter
s 150 mm 50 seconds per meter
t 200 mm 70 seconds per meter
u 300 mm 100 seconds per meter
16 Cleaning of oxygen systems
16.1 Preparation
1.1.9 Oxygen systems are defined as all pipe work and equipment
containing pure gaseous oxygen or gas mixtures containing more than
23% oxygen.
1.1.10 Oxygen system needs to be cleaned properly prior to the
introduction oxygen, as the presence of surface contamination,
minute solid particles, oil or grease on the surface of the piping
and equipment in the presence of gaseous oxygen may cause
spontaneous combustion and subsequent fire.
1.1.11 All equipment items, instrumentation and valves are
required to be designed, manufactured, supplied, transported and
stored for oxygen service.
1.1.12 The contractor shall inspect all equipment and piping
components prior to commencing fabrication, to ensure that all
protective coatings have been removed. Any protective coatings
shall be removed as a separate operation to any cleaning for oxygen
service.16.2 Cleaning
16.2.1 Several methods of cleaning may be used to achieve the
required level of cleanliness. The final choice will depend on the
type of equipment or component, the length and layout of pipe work,
the timing and location of cleaning operations etc. These
include:
a Mechanical cleaning
b Aqueous detergent cleaning
c High pressure hot water cleaning
d Solvent cleaning
16.2.2 Most aqueous or solvent cleaners are not compatible with
oxygen or leave non-compatible residues behind; therefore
scrupulous care shall be taken in rinsing thoroughly immediately
after the cleaning process to ensure the complete removal of all
traces of the cleaning solvent.
16.2.3 Prior to commencing any solvent or aqueous cleaning,
Contractor shall certify that the solvent or aqueous cleaner
proposed for use is non-injurious to all the materials (metallic
and non-metallic) used in the manufacture or fabrication of the
item or component being cleaned.
16.3 Mechanical cleaning
16.3.1 Mechanical blast cleaning with grit or aluminium oxide
using dry, oil free air, nitrogen or high pressure water as the
carrier medium is acceptable for large, easily accessible
areas.
16.3.2 Metallic shot shall not be used.
16.3.3 The use of proprietary abrasive cleaning processes as
such shall be subject to specific review and approval by owner.
16.4 Aqueous detergents
16.4.1 Aqueous detergents shall be supplied in concentrated
liquid form and shall be mixed according the manufacturers
recommendation.
16.4.2 The solution may be heated to 50-650C to increase its
effectiveness.
16.4.3 The following cleaning solutions have proved effective in
obtaining the required level of cleanliness when used in accordance
with the manufacturers recommendations:-
a Blue Gold Cleaner
b Beyond 2001(c Simple Green(d Crystal Simple Green(16.4.4 For
larger equipment items high pressure, hot water cleaning with
aqueous detergent may be used.
16.4.5 For piping systems, the aqueous detergent solution shall
be circulated for a minimum of two hours or the manufacturers
recommendation (whichever is longer) and then flushed with hot,
clean, potable water until all traces of detergent are removed.
16.4.6 The system shall be dried with dry, oil free air or
nitrogen or a combination of both.
16.4.7 The spent cleaner shall be disposed of in accordance with
the manufacturers recommendation and local and national
regulations.
16.5 High pressure hot water cleaning
16.5.1 Pre-wash the surface with hot water (at least 900C) to
heat any oil or grease and reduce its viscosity followed by
spraying with an aqueous detergent cleaner.
16.5.2 After the soak period as recommended by the manufacturer,
wash the surface with hot water and allow drying.
16.5.3 The cleaning water shall be disposed of in accordance
with local and national regulations.16.6 Solvent cleaning
16.6.1 Solvent cleaning may be accomplished in a one-step or
two-step procedure.
16.6.2 The choice of which method to use will depend on the
degree of contamination with oil and grease.
16.6.3 For heavily contaminated surfaces a two step procedure is
recommended.
16.6.4 Recommended one step solvents are:
a Borothene
b Leksol(c AK 225
d Vertrel(e Novec(16.6.5 For two set solvent cleaning, the
recommended first step solvents are:
a Art 98
b Glidsol( 66-2
c Actrel( 3349L
16.6.6 For piping systems the method of solvent cleaning shall
be agreed with the owner.
16.6.7 Wherever possible solvents shall be sprayed onto the
surface ensuring that all parts of the surface are contacted.
16.6.8 Where spraying is not possible, solvent shall be
circulated for at least one hour or the manufacturers
recommendations, whichever is greater.
16.6.9 The system shall be dried with dry, oil free air or
nitrogen or a combination of both.
16.6.10 The spent solvent shall be disposed of in accordance
with the manufacturers recommendations and local and national
regulations.
16.6.11 Prior to any solvent cleaning, a fresh sample shall be
stored for reference purposes.
16.7 Inspection methods
16.7.1 Immediately after drying, inspection shall be performed
by each of the following methods:
a Visual inspection under a bright, white light.b Visual
inspection under an ultraviolet light (wavelength 32-38m, 3200 4000
Amstrom units).c Light to be warmed up for 5 min prior to use
i) Inspection should not be carried out in direct sunlight or
under florescent lighting
ii) Lighting intensity of light on the surface to be tested
shall not be less than 500W/cm2
iii) Light should be kept 20 30 cm form the surface tested
16.7.2 Visual inspection by wiping and inspecting the wipe
medium under bright, white light and ultraviolet light. For the
wipe test, inspection shall be performed by wiping approximately
0.1m2 with a clean, white, lint-free cloth, or clean, lint-free
filter paper.
16.7.3 If surfaces cannot be inspected visually, but hand access
is possible, a wipe test as specified shall be utilised.
16.7.4 If it is not possible to perform a visual inspection or
wipe test, a quantity of unused solvent shall be circulated over
the surfaces. A 100ml sample shall be collected in a clean, glass
container and examined for compliance, after which a 20ml sample
shall be evaporated to dryness on a clean watch glass and examined
for compliance.
16.8 Acceptance criteria
16.8.1 For final acceptance, oxygen systems shall be inspected
either immediately prior to final closing welds (for items subject
to pre-fabrication cleaning) or after post-erection cleaning and
shall meet the following criteria:
a No moisture present
b No cleaning agent residue present
c No corrosion scale, particulate matter, weld spatter, flux
residue from welding, cutting swarf or foreign materials such as
sand or site debris present
d No paint, crayon or protective coatings present
e No hydrocarbon or organic material residues, such as oil,
grease, adhesives or sealants present.
16.8.2 Visual inspection under ultraviolet light shall show no
evidence of hydrocarbon fluorescence or significant quantities of
textile fibres (not greater than 75 particles per 0.1m2). Areas of
low intensity fluorescence shall be re-examined visually and with a
wipe test to determine acceptability.
16.8.3 Where a wipe test is performed, no discolouration of the
wiping medium, except that caused by oxidation of the parent
material, no evidence of oily residue or any other visible
particles on the wiping medium and no evidence of hydrocarbon
fluorescence.
16.8.4 For the analysis of the circulated solvent, if laboratory
analysis is available, a level of 200mg/m2 is considered an
acceptable maximum for oil films.
16.8.5 For the evaporation test the sample shall not contain
more than 20mg/kg residue.17 Generic machine precautions
17.1 During cleaning various high pressures portable equipment
may be used for the provision of:
a steam;b air;c nitrogen;d vacuum; ande liquid circulation;17.2
The following general precautions should be followed with such
machines and related auxiliary equipment:
f Make sure the machines are in a good operating condition. Most
suppliers would be able to provide an equipment check sheet. The
inspection check sheet should be in accordance to SSP-S-0111.
g All safety documentation for the equipment must be available
on site ea. RV setting certificates, Pressure vessel inspection
information etc.
h Declaring of competency must be available for the operators of
the machines.
i All piping connections should be according to Sasol
specification.
j Area around the machine should be demarcated or
barricaded.
k Ensure that all personnel are trained to operate the
equipment.
l The task at hand should be well understood.
m A risk assessment is required before the work start. This
could be in the form of a possible deviation analysis (PDA).
n All flexible connection must be fitted with anti whip
devices.
o Ensure that all nozzle connections is secure.
p During any high pressure cleaning a notice must be posted at
the work area indicating that high pressure cleaning in
progress.
q All electrical connections should be according to Sasol
specifications.
r The person operating the machine should always be in eye
contact with the operator performing the cleaning actions.
18 AppendicesAppendix A: Comparisons of cleaning methods
Appendix B: Definition of cleaning classesAppendix C: Cleaning
decision Tree 19 AcknowledgementsAcknowledgement to the following
departments and persons for their contributions to this
document:Dirk Bosch
Tas van Staden
Management Systems
20 Review Cycle
This document to be reviewed within:
6 months
1 year(
2 years
3 years
Appendix A: Comparisons of cleaning methods
MethodCleaning MethodProcess ApplicationEffectivenessMedium
usedMin DiameterMax diameterCyclesPressureFlow
1FlushingLiquid EquipmentDebrisWaterN/A250mm1N/A> 4m/s
2Air blowing - DirectGas PipingDebrisAir or NitrogenN/A600
mm1N/A35 60 m/s
3Air blowing - AccumulationGas PipingDebrisAir or NitrogenN/A600
mm3-42-3 barN/A
4Steam Blowing - SteamingSteam
UtilitiesDebrisSteamN/AN/A1N/ADesign
5Steam Blowing ProgramSteam Process EquipmentScale and rustSteam
N.AN/A3N/ADesign
6Steam Blowing TargetSteam TurbinesScale and rustSteam N.AN/A4
-8N/ADesign
7Acid CleaningTurbine Suction
Oil systems
Oxygen systems
Boiler feed waterScale, rust, mill scaleInorganic/Organic
AcidN/A600 mm1 cycle
7 stepsN/A
MethodCleaning MethodProcess ApplicationEffectivenessMedium
usedMin DiameterMax diameterCyclesPressureFlow
8DegreasingBoiler drums
Amine Systems
Pre- acid cleanMineral and organic oils and fatsSodium
Hydroxide
Sodium Carbonate
N/A600 mm1 Cycle
3 stepsN/AN/A
9Hand cleaningVessels
PipingDebrisElbow grease600 mmN/A1N/AN/A
10PiggingLong PipingFree Water
Debris
Scale and rustSynthetic Pig
Water or Air to drive pig50 mm850mm1-101 -4 bar/m2 pipe
diameter1 1.5 m/s
11Sand blastingVessels & Large PipingScale, rust and
protective coatingsSand, grid or alumina oxide250 mmN/A1N/AN/A
Appendix B: Definition of cleaning classesClassDefinition
1 Remove all lose debris
2 Remove all debris
Remove adhered material that would come loose under
operation
3 Remove all debris
Remove adhered material that would come loose under
operation
Remove all oil, grease and protective coatings
4 Remove all debris
Remove adhered material that would come loose under
operation
Remove all oil, grease and protective coatings
Remove rust, mill scale and welding spatter to achieve bare
metal.
Appendix C: Cleaning Decision TreeLead and Direct
Measure, Analyse and Improve
Deliver
Enable to Deliver
Proposed by:A. OosthuizenApproved by:R. Brink
Validity:This document is only valid for 14 days after 29
September 2009, if printed
Copyright:This document is protected by copyright and is the
sole property of Sasol Technology. The information is proprietary
to Sasol Technology and any unauthorised use, disclosure or copying
or any other means of duplication or reproduction is prohibited.
Copyright 2009. Sasol Technology. All rights reservedPage 1 of
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