Manually Sample Non-Pressurized Tanks · 2018. 5. 14. · Manually Sample Non-Pressurized Tanks Human Development˜ Consultants Ltd. American Society for Testing and Materials (ASTM):

Human DevelopmentConsultants Ltd.

Training Module

Manually SampleNon-PressurizedTanks

Manually Sample Non-Pressurized Tanks

December, 2003


© HDC Human Development Consultants Ltd. All rights reserved. No part of this publication may be copied, reproduced, stored in a computer or retrieval system, published, distributed, or transmitted in any form or by any means whatsoever, including without limitation by mechanical means, photo copying, recording, digital or electronic media, the Internet, or otherwise, without the express prior written permission of HDC Human Development Consultants Ltd. (HDC). HDC grants to the purchaser of a Single User License (as defined in the agreement with such purchaser) a limited license to store the electronic file(s) on one computer only and to make a single paper copy of this publication. HDC grants to the purchaser of a Site License (as defined in the agreement with such purchaser) a limited license to store the electronic file(s) on one local area network server accessible by individual users' computers at one site or location only and to make paper copies of this publication for a company’s employees at the same site or location only. Each site or location must purchase a separate Site License for employees at that site. HDC grants the purchaser of a Corporate License (as defined in the agreement with such purchaser) a limited license to store the electronic file(s) on its intranet and on computers at company sites or locations and to make paper copies for any or all employees. Nothing in the foregoing restricts, amends or abrogates the provisions of the agreement between HDC and the purchaser of the applicable license. Any copying or use other than pursuant to such a license is illegal. For further information, please consult the applicable license agreement. This publication is designed to provide general information regarding the subject matter covered. Care has been taken to ensure the accuracy of the information and that the instructions contained in this publication are clear and reflect sound practice. The user understands that HDC is not providing engineering services. The user understands that any procedures (task steps) that are published or referenced may have to be modified to comply with specific equipment, work conditions, company standards, company policies and practices, legislation, and user qualifications. HDC does not make any representations, guarantees, or warranties of any kind whatsoever with respect to the content hereof and the results to be achieved by implementing the procedures (task steps) herein. To the maximum extent permitted by applicable law, in no event shall HDC be liable for any damages whatsoever (including without limitation, direct or indirect damages for personal injury, damages to the environment, damages to business property, loss of business profit, or any other pecuniary loss). The use of the information and procedures (task steps) herein is undertaken at the sole risk of the user. ISBN 1-55338-038-X Canadian Cataloguing in Publication Data 1. Petroleum—Sampling. I. HDC Human Development Consultants TP692.5.M25 2003 665.5’028’7 C2003-905958-8 This training kit consists of the following parts: ♦ Training Module and Self-Check ♦ Knowledge Check and Answer Key ♦ Blank Answer Sheet

♦ Performance Check ♦ Job Aid

Published by HDC Human Development Consultants Ltd.

Published in Canada

HDC Human Development Consultants Ltd. Website: www.hdc.ca E-mail: [email protected] Phone: (780) 463-3909


Human Development�Consultants Ltd.

Contents Training Objectives 1

1 Introduction 1

2 Samples 3 2.1 Spot and Composite Samples 3 2.2 Sampling Levels 4 x

3 Sampling Equipment 7 3.1 Samplers (Primary Sample Receiver) 8 3.2 Drop Cords and Trip Cords 14 3.3 Sample Containers (Secondary Sample Receiver) 15 3.4 Sampler and Sample Container Closures 15

4 Sample Accuracy 16 4.1 Uncontaminated Sample 16 4.2 Representative Sample 17 4.3 Sample for Laboratory Analysis 19 4.4 Properly Labeled Sample 19 4.5 Correct Sample Handling and Shipping 20

5 Safety 21 5.1 Physical Hazards 21 5.2 Chemical Hazards 22 5.3 Safety before Climbing to the Roof 24 5.4 Safety while Sampling 24 5.5 Sampling Tanks with Floating Roofs 25

December, 2003 Page i of ii



Contents (continued) 6 Sampling Procedures 26

6.1 Spot Sample Procedure: Core Thief Sampler 26 6.2 Spot Sample Procedure: Bacon Bomb Sampler 28 6.3 Spot Sample Procedure: Cage and Bottle Sampler 29 6.4 Spot Sample Procedure: Weighted Beaker Sampler 30 6.5 Running Sample Procedure: Cage and Bottle Sampler 31 6.6 Bottom Sample Procedure: Core Thief Sampler 32

7 Self-Check 33

8 Self-Check Answer Key 37

December, 2003 Page ii of ii



Training Objectives

Upon completion of this training kit, you will be able to:

Describe the purpose and importance of manually sampling non-pressurized tanks Describe types of samples Describe tank sampling equipment Describe tank sampling accuracy Describe tank sampling safety hazards and precautions Sample tanks

1 Introduction In the oil and gas industry, well emulsions, fuel, field chemicals, by-products from gas processing, and refined petroleum products are stored and transported in non-pressurized tanks. Non-pressurized tanks include storage tanks at well sites, batteries, plants, and terminals, and also rail tank cars, tanker trucks, and ship and barge tanks.

Products in a tank are sampled and analyzed to determine the product’s chemical and physical properties, such as density (API gravity), water content, and contaminants. These properties are used in the determination of standard volumes and prices.

To take a sample, an operator lowers a sampler on a cord from the gauge hatch at the top of the tank until the sampler is at the desired level in the tank. At the desired level, the operator remotely trips the sampler to allow the sampler to fill and then pulls the sampler back up. The operator carefully transfers the sample from the sampler to a sample container, closes the container, and affixes a label to the container. Depending on the analyses required, the operator analyzes the sample immediately, takes the sample to a local laboratory, or sends the sample to a central laboratory.

Tanks are sampled in accordance with the standard practice published by:

American Petroleum Institute (API): Manual of Petroleum Measurement Standards, Chapter 8—Sampling; 8.1—Manual Sampling of Petroleum and Petroleum Products; 8.3—Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products

December, 2003 Page 1 of 37



American Society for Testing and Materials (ASTM): D 4057-95 (2000)—Standard Practice for Manual Sampling of Petroleum and Petroleum Products International Organization for Standardization (ISO): Petroleum Liquids – Manual Sampling (ISO 3170)

Contents of this Training Kit This training kit describes how to safely and reliably take manual samples of liquid petroleum products and free water from non-pressurized tanks. The kit focuses on methods for sampling:

crude petroleum liquid hydrocarbons with Reid Vapor Pressure (RVP) below 101.32 kilopascals (kPa) (14.7 pounds per square inch absolute—psia)

NOTE Reid Vapor Pressure is the pressure of a liquid when it is heated to a temperature of 37.8°C (100°F) in a sealed Reid test chamber. A product’s RVP is a measure of the product’s volatility: the higher the RVP, the more volatile the product. This kit is aimed primarily at pipeline terminal/field operators who are responsible for manually sampling storage tanks, rail tank cars, tank trucks, and ship and barge tanks. The kit describes:

different types of sample

manual sampling equipment practices which ensure sample accuracy manual sampling safety issues procedures for manually obtaining a sample of liquid hydrocarbons from storage tanks, rail tank cars, tank trucks, and ship and barge tanks.

This training kit does not include procedures for:

manual sampling of tank residues, lumpy solids, greases, or asphaltic materials manual sampling of pipelines automatic sampling of tanks or pipelines sampling fuels for determining the fuel’s volatility sampling products with Reid Vapor Pressure above 101.32 kPa (14.7 psia)




This kit is one of a series of two HDC training kits related to storage tanks. The other kit is Manually Gauge Non-Pressurized Above-Ground Tanks.

NOTE This kit provides instruction on tank sampling equipment and its application. The kit does not endorse or promote any specific model, manufacturer, or supplier.

2 Samples This section describes spot and composite samples and the levels in the tank at which samples are taken.

2.1 Spot and Composite Samples Types of sample include:

spot sample—a sample taken at a specific location in a tank

composite sample—a sample obtained by combining spot samples in defined proportions so that the sample is representative of the product in the tank: – for upright cylindrical tanks, spot samples are taken at

the levels indicated in the following table and blended in equal proportions. (Sampling levels are described in the next section.)

Composite Sample: Vertical Cylindrical Tanks

Required Samples Tank Capacity Product Height upper middle lower

larger than 160 m3 (1000 bbls)

> 4.5 m (>15 ft.)

larger than 160 m3 (1000 bbls)

3 – 4.5 m (10 – 15 ft.)

up to and including 160 m3 (1000 bbls)




– for horizontal cylindrical tanks, such as rail tank cars and tank trucks, samples are taken and blended at the levels and proportions indicated in the following table. Figure 1 illustrates this concept.

Composite Sample: Horizontal Cylindrical Tanks

Sampling Level (percentage of diameter

above the bottom)

Composite Sample (proportional parts

out of 10)

Liquid Depth (percentage of

diameter) upper middle lower upper middle lower

100 80 50 20 3 4 3 90* 75 50 20 3 4 3 80 70 50 20 2 5 3 70 50 20 6 4 60* 50 20 5 5 50 40 20 4 6 40* 20 10 30 15 10 20 10 10 10 5 10

*Refer to Figure 1. For tankers or vessels with compartments, take at least one sample from each compartment. When a composite sample of the different compartments is required, the volume of sample from each compartment making up the composite sample should be in the same proportion as the volume of product in each compartment. For example, one compartment of a tanker truck is 100% full and the other compartment is only 60% full. The composite sample would contain 10 parts from the first compartment and 6 parts from the second compartment.

2.2 Sampling Levels Samples are taken from the gauge (thief) hatch at the top of the tank.

NOTE Samples are not taken from valves near the bottom of the tank. Such samples are usually not representative of the product in the tank. Also, with infrequent use, the valve may fail when opened and tank contents may be spilled.





50%

3

3

4

25%20% level

50% level

75% level 75%

100%

0%Tank 90% full

5

5

20% level

50% level

Tank 60% full

10

20% level

Tank 40% full

50%

25%

75%

100%

0%

50%

25%

75%

100%

0%

Figure 1—Sampling Levels and Composite Samples for Horizontal Cylindrical Tanks




water & sediment

outlet (suction level)sample

lower 1/3

middle 1/3

lower sample(middle of lower 1/3)

middle sample(middle of middle 1/3)

upper sample(middle of upper 1/3)

(1/6 from top surface)

top sample150 mm (6 in)below surface

bottom sample

upper 1/3

Figure 2—Sampling Levels The following sampling levels are illustrated in Figure 2: top sample—a spot sample taken 150 mm (6 in.) below the

top surface of the liquid. upper sample—a spot sample taken from the middle of the

upper one-third of the product in the tank (i.e., one-sixth of the depth of liquid below the top surface), excluding any free water or sediment at the bottom of the tank.

middle sample—a spot sample taken from the middle of the middle one-third of the product in the tank (i.e., one-half of the depth of liquid below the top surface), excluding any free water or sediment at the bottom of the tank.

lower sample—a spot sample taken from the middle of the lower one-third of the product in the tank (i.e., five-sixths of the depth of liquid below the top surface), excluding any free water or sediment at the bottom of the tank.

outlet (suction-level) sample—a spot sample taken at the tank outlet. The opening of the sampler is level with the bottom of the outlet.

Gauge (Thief) Hatch Small cover located on the top of the tank. The gauge hatch allows operators to look inside the tank and to gauge and sample the tank.



bottom sample—a spot sample taken from the material at or close to the bottom of the tank. Bottom sample locations must be specified (e.g., “150 mm [6 in.] from the bottom”). bottom water sample—a spot sample of the layer of free water located below the petroleum in the tank all-levels sample—a sample obtained with a sampler which is filled to between 70 and 85% while the sampler passes through the total liquid height in either a downward or an upward direction: – an empty, stoppered sampler is lowered to the bottom of

the tank (or just above the free water level). At the bottom, the stopper is removed remotely and the unstoppered sampler is raised to the surface at a rate that allows the sampler to fill between 70 and 85 percent.

– an empty, unstoppered sampler is lowered to the bottom of the tank (or just above the free water level) at a rate that allows the sampler to fill between 70 and 85 percent. At the bottom, the stopper is inserted remotely and the stoppered sampler is raised to the surface.

running sample—a sample obtained with a sampler which is slowly filled while the sampler passes through the total liquid height in both downward and upward directions. An empty sampler, stoppered with a perforated stopper, is lowered to the bottom of the liquid in the tank and raised to the surface at a uniform rate that allows the sampler to fill between 70 and 85 percent.

3 Sampling Equipment Sampling equipment includes:

samplers (primary sample receiver) drop cords and trip cords sample containers (secondary sample receiver) closures sample carriers

3.1 Samplers (Primary Sample Receiver) Several different types of samplers have been designed for manually sampling petroleum tanks.




The type of sampler to use depends on the type of product and the type of sample required. Before selecting a sampler, consider the following:

Samplers must be resistant to the solvent action of the product and cleaning agents used to clean the sampler after use.

Plastic samplers and bottles: – are acceptable for sampling and storing gas oil, diesel

oil, fuel oil, and lubricating oil – should not be used to store crude oil, gasoline, aviation

jet fuel, kerosene, and white spirit

NOTE Conventional polyethylene (i.e., non-linear polyethylene) containers must not be used because the polyethylene may contaminate the petroleum sample.

Samplers and sample containers must be made of a non-sparking material.

The sample taken must be suitable for the analyses that will be performed on the sample: – Samplers must be large enough to contain the required

sample. If the sampler is used as both primary and secondary receiver (i.e., if the sample will not be transferred from the sampler to a sample container), samplers must have room for thermal expansion (approximately 10 to 15%).

– Samples may lose light ends (i.e., volatile gases) during transfer from a primary sampler to a secondary sample container. When analyses of density or composition are required, samples should be left in the primary sampler until the moment of analysis (providing the primary sampler can be adequately sealed). When taking composite samples for density analysis, you will need enough samplers to take the required samples and hold the samples until the analyses are performed.

Light Ends The lighter molecules in a hydrocarbon mixture. Light ends have a lower boiling point and tend to vaporize readily.

– If the sample needs to be mixed before analysis, consider how suitable the sampler is for mixing. For example, if a sample of crude oil has stratified in the sampler before arriving at the laboratory, the sampler/ sample may need to be placed on a mixer and mixed before analysis. In this case, the sampler must be able to fit on the mixer and withstand the mixing action.





This section describes: the four common types of sampler:

– core thief – Bacon bomb – cage and bottle – weighted beaker

samplers used for: – all-levels and running samples – bottom samples

Core Thief Sampler Core thief samplers (thiefs) (Figure 3) are used to take spot samples and bottom samples in storage tanks, rail tank cars, tank trucks, and ship and barge tanks.

Core thiefs have the following features: a transparent glass or plastic (or metal) barrel with top and

bottom spring-loaded closures a gauge for determining the height of sediment and water in

the barrel a mechanical device and trip cord for tripping the valve

closure mechanism. The operator uses the trip cord to remotely open/close the valve.

Figure 3—Two Core Thief Samplers (Courtesy of W. L. Walker Co., Inc.)



low clearance: able to take a sample within 15 to 25 mm (1/2 to 1 in.) of the tank bottom sufficient weight so that the thief can sink in the product removable extension rods (from 75 to 460 mm) (3 to 18 in.) for sampling at specific heights above the tank bottom

Samples taken in core thiefs usually have to be transferred to a sample container so that the thief can be reused.

Bacon Bomb Sampler Bacon bomb samplers (Figure 4) are used to take bottom samples and spot samples in storage tanks, rail tank cars, tank trucks, and in ship and barge tanks.

Figure 4—Two Bacon Bombs (Courtesy of Koehler Instrument Company, Inc.)

Bacon bombs have the following features:

a chrome-plated brass or stainless steel barrel an internal plunger-type valve: – The plunger opens automatically when the sampler

strikes the tank bottom and closes when the sampler is raised.

– If the plunger is fitted with a trip cord, the operator can remotely open and close the plunger by lifting and releasing the trip cord.





low clearance: able to take a sample within 15 to 25 mm (1/2 to 1 in.) of the tank bottom

sufficient weight so that the bomb can sink in the product removable extension rods (from 75 to 460 mm) (3 to 18 in.)

for sampling at specific heights above the tank bottom Samples taken in Bacon bombs usually have to be transferred to a sample container so that the Bacon bomb can be reused.

Cage and Bottle Sampler Cage and bottle samplers (also known as weighted bottle samplers) (Figure 5) are used for taking spot samples, all-levels, and running samples, and for taking samples of volatile products in storage tanks, rail tank cars, tank trucks, and ship and barge tanks.

Cage and bottle samplers have the following features: a brass, stainless steel, or plastic frame or cage fitted with a

litre or half litre (quart or pint) clear or amber glass bottle a stopper connected to the cage by a rod (as in Figure 5), a

cord, or a chain. During sampling, the operator removes the stopper by sharply jerking the drop cord.

sufficient weight so that the sampler can sink in the product

Figure 5—Cage and Bottle Sampler (Courtesy of HERMetic, Inc.)



Samples taken in cage and bottle samplers do not have to be transferred to a sample container. Bottles can be removed from the cage, wiped off, stoppered, and transported to the lab. In this way, volatile light ends are not lost through evaporation during the transfer. For this reason, cage and bottle samplers are preferred for sampling volatile products.

Weighted Beaker Samplers Weighted beaker samplers (also known as weighted can samplers) (Figure 6) are used for taking spot samples, all levels samples, and running average samples in storage tanks, rail tank cars, tank trucks, and ship and barge tanks.

Figure 6—Weighted Beaker Sampler (Courtesy of Koehler Instrument Company, Inc.)




Weighted beaker samplers have the following features: made of stainless steel, copper, or brass attached to a lead base

equipped with a stopper tied to the beaker. During sampling, the operator removes the stopper by sharply jerking the drop cord. sufficient weight so that the sampler can sink in the product

After the sampler has been raised to the surface, the sample must be transferred to a sample container so that the weighted beaker can be reused. The flux used during the soldering manufacture of can samplers must be thoroughly removed before the sampler can be used. Some fluxes are difficult to remove and may contaminate the sample for certain analyses. Check with your vendor and laboratory to determine the suitability of the sampler.

Samplers Used for All-Levels and Running Samples Cage and bottle samplers and weighted beaker samplers can be used to take all-levels samples and running samples. Bottles and beakers can be fitted with closures that have small openings, allowing restrictive filling. When the sampler is lowered to the bottom of the tank and raised at a uniform rate, liquid flows into the restrictive opening. The product viscosity, density, and tank height dictate the size of the opening required. When the opening size and sampling speed are correct, a pocket of air remains when the sampler is removed from the tank. If there is no pocket of air, the sampler filled before the complete run was completed and the sample may not be representative of the product at all levels. Even when filled correctly (i.e., 70 to 85% full), the sample is not necessarily representative, depending on operator skill and tank dimensions. Bacon bomb samplers can be equipped with a needle valve at the top of the bomb. When the sampler is lowered to the bottom of the tank at a uniform rate, liquid flows into the lower end of the sampler only at the rate the air is displaced through the needle valve at the top.




Because you cannot see into the sampler, it is not possible to determine if the sampler is correctly filled (i.e., if there is a pocket of air).

Samplers Used for Bottom Samples Core thief samplers and Bacon bomb samplers are used for bottom sampling. Both types allow a sample to be taken from very close (15 to 25 mm; 1/2 to 1 in.) to the bottom. The core thief sampler is open while being lowered to the tank bottom: product flows through the sampler. When the sampler strikes the bottom (or when the operator remotely trips the mechanism), the valves close, trapping bottom product. The Bacon bomb sampler is closed while being lowered to the tank bottom. When the sampler strikes the bottom, the valve opens, admitting product into the bottom and expelling air from the top. When the sampler starts moving upward, the valve closes and traps bottom product.

3.2 Drop Cords and Trip Cords Drop cords or chains (also known as sample lines or lowering cords) are used to lower the sampler into the product. Trip cords (also known as plunger lines or valve cords) are used to trip the valve mechanism on core thief and Bacon bomb samplers.

Cords and chains should be spark resistant (i.e., unable to carry a static electrical charge—a source of ignition). For this reason, cords are usually made of vegetable fibers such as cotton or sisal; man-made fiber content should be limited. Chains are usually made of nickel-plated brass or stainless steel. Before taking samples, the operator measures and marks the required sample levels on the cord or chain. Cords are available with brass ferrules spaced at 300, 400, or 450 mm (12, 16, or 18 in.) intervals from the bottom of the sampler.




3.3 Sample Containers (Secondary Sample Receiver) Sample containers (secondary sample receivers) are normally clear or amber glass or metal bottles with an adequate stopper. Bottles normally range between 0.25 and 5 litres (1 cup to 1 gallon); they must be large enough to hold the required sample with sufficient space for expansion and mixing (10 to 15%). As with samplers:

sample containers must be resistant to the solvent action of the product and cleaning agent

conventional polyethylene (i.e., non-linear polyethylene) containers must not be used sample containers must be made of a non-sparking material

Sample containers must have a tight stopper to prevent the escape of volatile light ends. On metal bottles, the flux used during the soldering manufacture must be thoroughly removed before the bottle can be used. Some fluxes are difficult to remove and may contaminate the sample for certain analyses. Check with your vendor and laboratory to determine the suitability of the metal bottle.

3.4 Sampler and Sample Container Closures Closures for samplers and sample containers are corks, inert plastic stoppers, ground glass stoppers, and plastic or metal screw-caps. Corks should be clean, intact, and free from crumbling or loose bits. Corks:

should only be used for one type of product to prevent cross-contamination between different types of product should not be used for volatile liquids, because the vapor can diffuse into the cork and contaminate other samples




Wrapping the cork in clean aluminum foil before insertion into the container prevents the sample from contacting and contaminating the cork. Wrapping any stopper with aluminum foil protects highly refined products from moisture and dust. Containers with screw caps are used for samples that will be tested for density or composition. Screw caps must provide a vapor-tight seal. Caps should be fitted with a liner made of cork or other oil-resistant material. Cork liners must be replaced each time the screw cap is used to prevent cross-contamination between samples. Rubber stoppers should not be used because the rubber may be degraded by the product.

4 Sample Accuracy Samples must be taken and handled properly to ensure the sample which arrives at the laboratory is representative of the product in the tank. If sampling techniques are not correct, the sample—and subsequent analyses—may not be accurate. Inaccurate test results can mean lost revenue for your company. Sampling must therefore be carefully carried out. Ensure that:

the sampler and sample container are free of contaminants

the sample is representative of the product (i.e., has the same composition as the product) the sample is suitable for the required laboratory test the sample is correctly labeled the sample is correctly handled and transported

4.1 Uncontaminated Sample Cleanliness is an important part of proper sampling: any contaminants (such as water, dirt, cleaning solvent, soap, lint) introduced into the sample will produce inaccurate test results. All sampling equipment must be clean before a sample is taken.





Cleaning Procedure After the sample has been removed, reusable samplers and sample containers should be cleaned thoroughly with cleaning solvent to remove all traces of product and sediment.

WARNING

Read the material safety data sheet (MSDS) for the cleaning solvent. Use the personal protective equipment recommended in the MSDS when working with the solvent. Discard the solvent in accordance with your company’s hazardous waste procedures. Cleaning with solvent is followed by a wash in a strong soap solution to remove all traces of solvent, a thorough rinse with tap water, and a final rinse with distilled water. The containers must be air dried, either with clean, warm pressurized air or in a hot dust-free cabinet. As soon as the containers are dry, they must be stoppered and stored in a clean cabinet.

Gauge (Thief) Hatch Dirt and grime may be present around the tank’s gauge hatch. Operators should ensure that the gauge hatch and the area

End of Sample A full licensed copy of this kit includes: • Training Module and Self-Check • Knowledge Check and Answer Key • Blank Answer Sheet • Performance Check • Job Aid

Documents

Manually Sample Non-Pressurized Tanks · 2018. 5. 14. · Manually Sample Non-Pressurized Tanks Human Development˜ Consultants Ltd. American Society for Testing and Materials (ASTM):