Draft for

Public Comment

Zambian Standard

SAMPLING PETROLEUM PRODUCTS- Part 1: Manual

sampling of liquid hydrocarbons

ZAMBIA BUREAU OF S T A N D A R D S

DZS 396 Part 1: 2018

ICS 75.080:75.160.20

THIRD EDITION

This draft is for Public Comments

ONLY and should, therefore,

NOT be used or referred to as a

Zambian Standard

ii

DATE OF PUBLICATION

This Zambian Standard has been prepared and published under the authority of the Standards Council of the

Zambia Bureau of Standards on …………………..

ZAMBIA BUREAU OF STANDARDS

The Zambia Bureau of Standards is the Statutory National Standards Body for Zambia established under an act of

Parliament, the Standards Act, No 4 of 2017, of the Laws of Zambia for the preparation and promulgation of

Zambian Standards.

REVISION OF ZAMBIAN STANDARDS

Zambian Standards are revised, when necessary, by the issue of either amendments or of revised editions. It is

important that users of Zambian standards should ascertain that they are in possession of the latest amendments or

editions.

CONTRACT REQUIREMENTS

A Zambian standard does not purport to include all the necessary provisions of a contract. Users of Zambian

standards are responsible for their correct application.

TECHNICAL COMMITTEE RESPONSIBLE

The preparation of this Zambian Standard was undertaken by the Petroleum Products Technical Committee

(TC 4/14) upon which the following organizations were represented:

Afrox Zambia Limited

Alfred H. Knight (Z) Limited

Bio Fuels Association of Zambia

Energy Regulation Board

INDENI Petroleum Refinery Company Limited

Konkola Copper Mines Plc

Lublend Limited

Ministry of Energy and Water Development – Department of Petroleum

Mopani Copper Mines Plc

Puma Energy Zambia Plc

Tazama Pipelines

Zambia Bureau of Standards

Zambia Compulsory Standards Agency

Zambia Environmental Management Agency

Zambia Bureau of Standards Email: zabs@zamnet.zm or infozabs@zamnet.zm

Lechwe House Website: www.zabs.org.zm

Freedom Way South-end

P.O. Box 50259

Lusaka

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Table of Contents Page

TECHNICALCOMMITTEE RESPONSIBLE ............................................................. I

1. SCOPE............................................................................................................................................1

2. NORMATIVE REFERENCE ......................................................................................................2

3. DEFINITIONS...............................................................................................................................3

4. PRINCIPLES .6

5. APPARATUS.................................................................................................................................6

6. SAFETY PRECAUTIONS .........................................................................................................19

7. PROCEDURES ...........................................................................................................................22

8. PROCEDURES FOR CRUDE OILS AND OTHER NON-HOMOGENOUS LIQUIDS.....32

9. SAMPLE HANDLING ...............................................................................................................33

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FOREWORD

This Standard has been prepared by the Petroleum Products Quality Standards Technical Subcommittee

on Sampling in accordance with the procedures of the Bureau.

The absence of official national specifications or standards with respect to petroleum led necessitated the

formation of a subcommittee under Petroleum Products Technical Committee (CHD/14).

The standard supersedes the Zambian/International Standard ZS/ISO 3170:1988 Sampling Petroleum

Products - Part 1: Manual sampling of liquid hydrocarbons.

COMPLIANCE WITH A ZAMBIAN STANDARD DOES NOT IN ITSELF CONFER

IMMUNITY FROM LEGAL OBLIGATION.

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INTRODUCTION

This Standard should be applied in combination with ISO 3171, Petroleum liquids - Automatic pipeline

sampling.

The purpose of this Standard is to standardize conditions for obtaining a sample of liquid/semi-liquid

hydrocarbons from a tank, drum or pipeline. If the hydrocarbon materials to be sampled are of non-

homogeneous character showing significant variations in composition or containing sediments and water,

samples taken manually should not be expected to be representative, but enable the degree of non-

homogeneity to be assessed and estimates of quality and quantity to be made.

It is realized that in many countries some or all of the items covered by this Standard are the subject of

mandatory regulations imposed by the laws of those countries; such regulations must be rigorously

observed. In cases of conflict between such mandatory regulations and this Standard, the former shall

prevail.

1

ZAMBIA BUREAU OF STANDARDS

DRAFT ZAMBIAN STANDARD

SAMPLING PETROLEUM PRODUCTS

Part 1: Manual sampling of liquid hydrocarbons

1. SCOPE

This Zambian Standard specifies the procedures to be used for obtaining, by manual methods,

samples of liquid hydrocarbons, tank residues and deposits from fixed tanks, railcars, road vehicles,

ships and barges, drums and cans or from liquids being pumped in pipelines (see 4.1). The Standard

does not cover the manual sampling of aviation turbine fuels.

It applies to the sampling of liquid petroleum products, crude oils and intermediate products which are

stored in tanks at or near atmospheric pressure or transferred by pipelines and are handled as liquids at

temperatures from near ambient up to 100 oC

The sampling procedures specified are not intended for the sampling of special petroleum products

which may be the subject of other Standards, such as aviation fuels, electrical insulating oils, liquefied

petroleum gases, liquefied natural gases, bitumen and chemical products, nor to unstabilised crude oils

having a Reid vapour pressure above 180 kPa (1.8 bar).

Two basic manual sampling methods are available:

- Tank sampling

- Pipeline sampling

When a batch is received or consigned, either tank or pipeline sampling or both may be possible.

However, if both methods are used, the two sets of samples shall not be mixed.

Procedures are specified which minimize or eliminate losses of light ends from samples. Such losses

can occur during handling or transfer of samples thereby making them non-representative of the bulk

material.

If the procedures intended for obtaining representative samples of stocks or movements of

homogeneous petroleum liquids are applied to non-homogeneous liquids having significant variations

in composition or containing sediments and/or water the samples may not be representative.

2

The sampling procedures specified are intended to provide samples for the following purposes:

a) the determination of the oil quality

b) the determination of the water content of the oils

c) the determination of other contaminants that are not considered to be part of the liquid

transferred.

If the sampling conditions for the purposes a), b) and c) are in conflict, separate samples are required.

Sampling procedures for tank contents that are not homogeneous are specified that enable the degree of

non-homogeneity to be assessed and estimates of quality and quantity to be made.

Procedures for the sampling of residues and deposits in tanks are included, together with techniques for

liquid hydrocarbons under inert gas pressure.

2 NORMATIVE REFERENCE

The following Publications contain provisions which, through reference in this text, constitute provisions

of this standard. All standards are subject to revision and, since any reference to a publication is deemed

to be a reference to the latest edition of that publication, parties to agreements based on this standard are

encouraged to take steps to ensure the use of the most recent editions of the standards indicated below.

ISO 3117:1988 Petroleum liquids - Automatic pipeline sampling

ISO 2859 Sampling procedures and tables for inspection by attributes

ISO 2859/Add 1 General information on sampling inspection and guide to the use of the ISO 2859

tables

ISO 3734 Crude petroleum and fuel oils - Determination of water and sediment -Centrifuge

method

ASTM D 4057 Standard Practice for Manual Sampling of Petroleum and Petroleum Products

3. DEFINITIONS

3.1.1 Competent Person: A person who by reason of his or her training, experience and theoretical and

practical knowledge is able to detect any defects or weaknesses in the plant or equipment and to make

an authoritative judgement as to its suitability for further use.

3.1.2 Integrity of the sample: The condition of being complete and unaltered i.e. the sample being preserved

with the same composition as when it was taken from the bulk of the liquid.

3.1.3 Mixer: A device that provides a homogeneous mixture of the liquid within a pipeline or container in order

to obtain a representative sample.

3.1.4 Static mixer: A mixing device having no moving parts and located within a pipe or tube. It depends

on the kinetic energy of the moving liquid for the energy required to mix the liquid.

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3.1.5 Pipeline: Any section of pipe used for the transfer of liquid. An unobstructed pipe does not have any

internal fittings such as a static mixer or orifice plate.

3.1.6 Residues and deposits: Organic and inorganic material together with any water dispersed within it, which

has separated from the liquid or either

a) fallen to the bottom of the tank containing the liquid or

b) been left in the tank after the liquid has been pumped out.

3.1.7 Sample conditioning: Homogenisation necessary to stabilize the sample during sample handling in

preparation for analysis.

3.1.8 Sample handling: The conditioning, transferring, dividing and transportation of sample. It includes

transferring the sample from sampler (receiver) to a container and from the container to the laboratory

apparatus in which it is to be analysed.

3.2 Sample types

3.2.1 all-levels sample: A sample obtained with an apparatus that is filled when passed through the total liquid

height in one direction.

3.2.2 bottom sample: A spot sample taken from the material at the bottom surface (floor) of a tank

or container (see figure 1).

3.2.3 composite sample: A sample obtained by combining a number of spot samples in defined proportions

so as to obtain a sample representative of the bulk of the material. The usual types of composite

sample are obtained by combining samples in accordance with one of the following (see clause 4 and

7.7.1.1.2):

a) upper, middle and lower samples in equal proportions;

b) upper, middle and suction-level samples in equal proportions;

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c) a series of spot samples from a non-homogeneous all taken at more than three levels and blended in

proportion to the quantities of oil represented;

d) individual samples from several tanks or ship's compartments proportional to the total quantity each

sample represents;

e) a series of spot samples of equal volume obtained from flowing pipeline taken at specified intervals.

3.2.4 representative sample: A sample having its physical or chemical characteristics identical to the

volumetric average characteristics of the total volume being sampled.

3.2.5 running sample: A sample obtained by lowering a container from the top of the oil to the bottom and

returning it to the top of the oil at a speed such that the container is about three-quarters full when

withdrawn from the oil.

3.2.6 spot sample: A sample taken at a specific location in a tank or from a pipe at a specific time during a

pumping operation.

3.2.7 suction-level sample: A sample taken at the lowest level from which liquid hydrocarbon is pumped from

the tank. In determining this level, appropriate allowance is made for any fittings within the tank such as

swing-arm, suction baffle or internal bend (see figure 1).

3.2.8 upper sample: A sample taken at a level of one-sixth of the depth of liquid below the top surface (see

figure1).

5

3.2.9 middle sample: A sample taken at a level of one-half of the depth of liquid below the top surface (see

figure 1).

3.2.10 lower sample: A sample taken at a level of five sixths of the depth of liquid below the top surface (see

figure 1).

3.2.11 top sample: A spot sample obtained 150 mm below the top surface of the liquid (see figure 1).

3.2.12 skim sample (surface sample): A sample taken from the surface of the liquid (see figure 1).

3.3 Statistical terms

3.3.1 AQL (acceptable quality level): The maximum per cent defective (or the maximum number of defects

per hundred units) that for purposes of sampling inspection can be considered satisfactory as a process

average.

3.3.2 batch: A collection of packages containing a product of a single type and composition and of a single

manufactured lot or of a single delivery.

3.3.3 package: Any type of container, such as a drum barrel, peg, can or bottle.

3.3.4 per cent defective: one hundred times the number of defective units of product contained in any given

quantity of units of product divided by the total number of units of product i.e.

Per cent Defective = (number of defectives / number of units inspected) x 100

3.3.5 sample size: The number of samples to be drawn from a batch to determine its acceptability as given in

sampling plans.

3.3.6 Ullage: For the purpose of this Zambian Standard, the empty capacity left in a sample receiver/container

above the liquid surface expressed as volume.

3.4 Water

3.4.1 Dissolved water: The water contained within the oil forming a solution at the prevailing temperature.

3.4.2 suspended water: The water within the oil that is finely dispersed as small droplets.

NOTE - It may, over a period of time, either collect as free water or become dissolved water, depending on the conditions of

temperature and pressure prevailing.

3.4.3 free water: The water that exists as a separate layer from the oil and typically lies beneath the oil.

3.3.4 total water: The sum of all the dissolved, suspended and free water in a cargo or parcel of oil.

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4. PRINCIPLES

To ensure that samples submitted for examination are as representative as possible of the oil being sampled,

the necessary precautions are given. The physical and chemical property tests to be performed on a sample will

dictate the sampling procedures, the sample quantity required, and many of the sample handling requirements.

Tank sampling is commenced when the contents of the tank are at rest. The following samples are normally

taken for analysis:

Either

a) upper, middle and lower samples or

b) upper, middle and suction level samples.

If tests on these samples show that the contents of the tank are homogeneous, they may be combined in equal

proportions for further tests.

If the tests on these samples show that the contents of the tank are non-homogeneous, it is necessary to draw

samples from more than three levels and either a composite sample is prepared for analysis or if blending would

impair the integrity of the sample, each sample is analysed separately and the composition corresponding to the

composite sample is calculated. In this calculation, allowance is made for the proportion of the oil represented

by each sample.

Other methods are

c) a running sample, or d) an

all-levels sample.

To obtain a representative sample from a batch of non-homogeneous material being pumped in a pipeline, the

sample shall be drawn using an automatic sampling device as stated in ISO 3171. On occasions it may be

necessary to take samples manually. These are spot samples and may not be representative of the bulk.

5. APPARATUS 5.1 General

All sampling devices shall be designed and constructed so as to assure the function for which they are intended

in order to maintain the initial characteristics of the oil. They shall be of sufficient strength and externally

protected to withstand normal internal pressures likely to be generated, or provided with a relief valve and

sufficiently robust to withstand any handling that may be encountered. Their cleanliness shall be confirmed

before use.

Regardless of the type of sample container used, the sample container should be large enough to contain the

required sample volume without exceeding 80 % of the container capacity. The additional capacity is required

for thermal expansion of the sample and enhances sample mixing.

NOTE -Various sampling devices are described in general terms in 5.2 to 5.7 and any essential aspects are specified. Detailed specifications have not been given for these items because any suitable device of the type described may be used.

5.2 Tank samplers

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5.2.1 General

The tank samplers are classified according to the type of sample to be drawn:

- spot sample;

- bottom sample;

- tank deposits/residues sample;

- running sample;

- all-levels sample.

The devices shall have a cord or cable or chain of conductive, spark proof material attached to them for the

purpose of lowering or raising them in the tank.

NOTE - The cord should be sufficiently conductive not to be capable of producing static electricity.

5.2.2 Spot samplers

This apparatus shall be constructed so that a sample can be taken at any specific level in a tank. The

following kinds of apparatus are suitable.

5.2.3 Sampling cage

8

This shall be a metal or plastics holder or cage, suitably constructed to hold the appropriate container.

The combined apparatus shall be weighted so as to sink readily in the material to be sampled and

provision shall be made to fill the container at any desired level (see figure 2).

Bottles of the appropriate dimensions are required to fit a sampling cage. The use of a sampling cage

is generally preferred to that of a weighted sampling can for volatile products, since loss of light ends

is likely to occur when transferring the sample from a weighted sampling can to another container.

NOTE - The sampling cage may be omitted if the sample bottle is securely attached to a weighted cord. The cork is also tied to the

line about 150 mm from the neck of the bottle.

9

5.2.4 Weighted sampling can (see figure 3)

This shall be weighted so as to sink readily in the oil to be sampled. If used for obtaining upper,

middle lower or suction level samples, the lowering device shall be attached to the can in such a

manner that the stopper can be opened by means of a sharp jerk. If used as a running sampler, the

special stopper shown in figure 4 shall be used. In order to avoid problems in cleaning the can any

weighting material shall be fixed to the can in such a way that it does not come into contact with the

sample.

Some sampling cans have special opening facilities for example devices having valves opened or

closed at the desired level by a weight falling down alongside and guided by the suspending cable or

having wing or flap valves which are closed upon initiation of upward movement.

NOTE - The size of opening will be dependent on the viscosity of the liquid, its depth and the size of container.

Table 1. Weighted Sampling Bottle or Beaker

Material

Diameter of opening, cm.

Light lubricating oils, kerosenes,

gasolines, transparent gas oils, diesel

fuels, and distillates.

2

Heavy lubr icat ing o i l s , non-

transparent gas oils.

4

Light crude oils less than 43 cSt at 40 C. 2

Heavy crude and fuel oils. 4

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5.2.5 Interface sampler

A tube made of glass, metal or plastics material open at both ends to allow a free flow of liquid during

lowering through the liquid. Various devices may achieve the closing of the lower end at the desired

level:

a) a closure mechanism actuated by upward movement of the sampler; b) a weight falling down guided by the suspending cable (drop messenger) so as to actuate the closure

mechanism.

An interface sampler may be used for withdrawing a spot sample from a selected level or taking a bottom

sample to detect the presence of contaminants.

It shall be designed and constructed such that if lowered slowly it can be used to trap a vertical column of

liquid at the bottom of the tank or at any other selected level (see figure 5)

5.2.6 Bottom samplers

These are receptacles which can be lowered to the bottom of a tank where a valve or similar closure is

opened by contact with the floor of the tank and closed on lifting (see figure 6).

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5.3 Residue/deposit samplers

5.3.1 Grab sampler

The sampler consists of a sturdy-walled brass casing with an integrated grasping device. The bottom of

the sampler body consists of two spring-closed jaws, the mechanism of which is released by a drop

messenger. Two light plates cover the opening at the top of the sampler to prevent the sampler from being

washed out while the sampler is being raised out of the liquid (figure 7).

5.3.2 Gravitation/ram core sampler

This is a tubular device of uniform diameter either weighted or equipped with a mechanically operated

driver to penetrate the deposit layer to be sampled.

5.3.3 Running samplers

A running sampler is a container weighted or enclosed in a weighted cage and equipped if necessary with

a restrictive filling device (see figure 4). It is designed to obtain a sample whilst being lowered and raised

through the oil (see figures 2 and 3). It has not been established that such devices fill at a uniform rate.

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5.4 All-levels sampling devices

These devices have a liquid inlet and gas outlet designed to obtain a sample whilst being lowered or raised through the

oil. It has not been established that such devices fill at a uniform rate.

An example is shown in figure 8.

5.5 Vapour-lock devices

These are used to take samples from tanks under pressure in particular from those tanks utilizing inert gas systems.

They can consist of a gas-tight enclosure placed on top of a valved roof connection as shown in figure 9. A sample

container in a suitable sampling cage or the special sampler shown in figure 9 can be attached, via a gas tight window

to the lowering gear. The window is then closed, the roof valve opened and the sample container or sampler lowered

to the required depth in the product before filling. The valve is closed with the sampler in the elevated position before

the latter is withdrawn via the window.

5.6 Drum and can samplers

A tube sampler is commonly used (see figure 10). This is a tube made of glass, metal or plastics material with suitable

fittings if required to facilitate handling, which can be inserted into a drum, can or road vehicle to the desired level. It

may be used for withdrawing either a spot sample from a selected level or a bottom sample to detect the presence of

contaminants. A tube sampler having a closure mechanism at the lower end can be used for taking a representative

sample through a vertical cross-section of the liquid.

Alternatively, a small sampling cage of appropriate dimensions or a drum pump or siphoning device may be used.

5.7 Pipeline samplers

If an automatic pipeline sampler is required refer to ISO 3171.

5.7.1 Manual Pipeline Sampling

5.7.1.1 Application. This manual pipeline sampling is applicable to liquids of 101 kPa (14.7 psia) RVP or less and semi-

liquids in pipelines, filling lines, and transfer lines. When custody transfer is involved, continuous automatic sampling

is the preferred method as opposed to manual pipeline samples. In the event of automatic sampler failure, manual

sampling may be needed. Such manual samples should be taken as representatively as possible.

Figure 11. Probes for Spot Manual Samples

17

Apparatus. A sampling probe is used to direct sample from the flowing stream. All probes should extend

into the centre one-third of the pipe's cross-section area. All probes inlets should be facing

5.7.1.2 A tube bevelled at a 45 angle as shown in fig 11 A.

5.7.1.3 A short radius elbow or pipe bends. The end of the probe should be chamfered on the inside diameter to

give a sharp entrance edge (see fig. 11 B).

5.7.1.4 A closed-end tube with a round orifice spaced near the closed end as shown in fig. 11 C.

5.7.2 Probe Location

5.7.2.1 Since the fluid to be sampled may not always be homogenous, the location, position, and size of the

sampling probe should be such as to minimize any separation of water and heavier particles that would

make their concentration different in the gathered sample than in the main stream.

5.7.2.2 The probe should always be in a horizontal plane to prevent drain back of any part of the sample to the

main stream.

5.7.2.3 The sampling probe should preferably be located in a vertical run of pipe where such a vertical run can be

provided. The probe may also be located in a horizontal run of pipe. The flowing velocity must be high

enough to provide adequate turbulent mixing.

5.7.2.4 Where adequate flowing velocity is not available, a suitable device for mixing the fluid flow should be

installed upstream of the sampling tap to reduce stratification to an acceptable level. If flow has been

vertical for a sufficient distance, as in a platform riser, such a device may not be necessary even at low

flow rates. Some effective methods for obtaining adequate mixing are: a reduction in pipe size, a series of

baffles, and orifice of perforated plate, or combination of any of these methods. The design or sizing of

the device is optional with the user, as long as the flowing stream is sufficiently well mixed to provide a

representative sample from the probe.

5.7.2.5 Sampling lines, used in conjunction with probes, should be as short as is practical and should be cleared

before the samples are taken.

5.7.2.6 When sampling semi-liquids, it may be necessary to heat the sample line, valves, and receiver to a

temperature just sufficient to keep the material liquid and to ensure accurate sampling and mixing.

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5.7.2.7 To control the rate at which the sample is withdrawn, the probe should be fitted with valves or plug cocks.

5.7.3 Procedure

5.7.3.1 Adjust the valve or plug cock from the sampling probe so that a steady stream is drawn from the probe.

Whenever possible, the rate of sample withdrawal should be such that the velocity of liquid flowing

through the probe is approximately equal to the average linear velocity of the stream flowing through

the pipeline. Measure and record the rate of sample withdrawal as litres per hour. Divert the sampling

stream to the sampling container continuously or intermittently to provide a quantity of sample that

will be of sufficient size

5.7.3.2 In sampling crude petroleum and other petroleum products, samples of 250 ml or more should be taken

every hour or at increments less than an hour, as necessary. By mutual agreement, the sample period or

sample size, or both, may be varied to accommodate the parcel size. It is important that the size of the

samples and the intervals between the sampling rate and volume must be varied accordingly so that the

flow is proportional. In practice, this is difficult to accomplish manually.

5.7.3.3 Each sample of crude petroleum should be placed in a closed container, and at the end of the agreed upon

time period, the combined samples should be mixed and a composite sample taken for test purposes. The

sample container should be stored in a cool, dry place; exposure to direct sunlight should be avoided.

5.7.3.4 Alternatively, line samples may be taken at regular intervals and individually tested. The individual test

results may be arithmetically averaged, adjusting for variations in flow rate during the agreed upon time

period.

5.7.3.5 Either composite or arithmetically averaged results are acceptable by mutual agreement.

5.7.3.6 With either procedure, always label each sample and deliver to the laboratory in the container in which it

was collected.

5.7.4 Containers

Sample containers shall be glass or plastics bottles, metal covered bottles or cans, depending on the

material to be sampled. The size of such vessels normally varies between 0.25 and 5 litres, but larger

containers may be required when special tests bulking or division of samples is called for. Plastics

containers shall not be used for sample storage as these may not retain the integrity of the sample due to

diffusion in addition, the use of containers made of non-linear polyethylene would lead to sample

contamination and/or sample container failure.

5.7.5 Container closures

Corks, ground glass stoppers or plastics or metal screw caps may be used for closing sample bottles.

Rubber stoppers shall not be used. Corks shall be of good quality and free from loose pieces or dust.

They shall be softened by rolling or squeezing and pressed well into the neck of the bottle to prevent

leakage or evaporation. Where necessary a protective cover of a suitable material shall be used. Corks

shall not be used with volatile liquids as the vapour may penetrate into the cork and cause contamination

of subsequent samples; an inert vapour-tight closure shall be used.

Corks shall not be re-used for different types of product, since thorough cleaning is difficult and

hydrocarbons may penetrate into the cork and cause contamination of subsequent samples. Re-use of

corks is permissible only if the use is restricted to one type of product.

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Screw caps of cans or bottles shall be fitted with discs of cork or other oil resistant material. The disc

which shall only be used once shall be removed before the cleaning of screw caps and a new disc shall

subsequently be fitted.

5.7.6 Sample coolers

A cooling coil made of seamless copper tubing or other suitable metal tubing with an internal diameter in

the range of 6 to 10 mm is fixed in an open, portable container in such a way that it is immersed in a

water/ice cube mixture during use.

The inlet end of the tubing shall be furnished with a flange or other appropriate means of connection to

the sampling valve.

The outlet end shall be open.

6 SAFETY PRECAUTIONS 6.1 General

6.1.1 The safety precautions given below apply generally and constitute good practice, but the list is not

necessarily comprehensive. The list shall be read in conjunction with ZS 402 and appropriate

national safety regulations or any recognized company of the petroleum industry. The precautions given

below shall be taken whenever they do not conflict with local or national regulations that must in any case

always be followed.

6.1.2 Careful consideration shall be given to the nature and kind of hazards of the material being sampled,

which will affect detailed nature of the precautions to be observed.

6.1.3 Personnel shall be made aware of the potential hazards and be given instructions in safety precautions

to be observed.

6.1.4 All regulations covering entry into hazardous areas shall be rigorously observed.

6.1.5 Care shall be taken to avoid inhaling petroleum vapours during the sampling operations by using

appropriate breathing apparatus. Protective clothing made from hydrocarbon-insoluble materials shall

be worn. Eye-shields and face-shields shall be worn where there is a danger of splash. Additional

precautions may be necessary when handling crude.

.

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6.2 Safety aspects of equipment

6.2.1 With regard to their mechanical properties, received containers shall be properly designed in

accordance with respective national/ international standards.

6.2.2 A competent person shall perform pressure tests and other inspection work according to the local

regulations and results of such tests shall be recorded. Cleaning and testing operations shall be

performed at regular intervals.

6.2.3 Cords used for lowering sampling equipment shall be electrically conductive. They shall not be made

solely from synthetic fibres; vegetable fibres such as manila or sisal are preferred for this purpose.

6.2.4 Portable metal sampling equipment used in flammable atmospheres shall be of non-sparking material.

6.2.5 Sampling personnel shall be provided with carriers for their equipment in order that at least one hand

may be free.

6.2.6 Lamps and torches shall be of an approved type which shall be intrinsically safe for use in flammable

atmosphere .

6.2.7 Suitable clothing and equipment to provide protection against all known hazards associated with the

material sampled shall be worn.

6.2.8 If the Reid vapour pressure (RVP) of the product sampled is between 100 kPa (1,0 bar) and 180 kPa

(1.8 bars) the sample bottles shall be protected with a metal case until the sample is discarded. Above

180 kPa (1,8 bar) RVP only sampling cans constructed to contain the pressure in shall be used (see

also 5.5)

6.2.9 Care shall be taken to avoid heating of volatile samples in containers with gas-tight closures.

6.3 Safety at sampling points

6.3.1 Sampling points shall be provided which enable samples to be taken in a safe manner. Any potential

hazards associated with sampling shall be clearly marked and it is recommended that a pressure gauge

be provided.

6.3.2 The sampling point and equipment shall be adequately maintained and regularly inspected and the

results of the inspection recorded by a competent person.

6.3.3 Safe access to sampling points with adequate lighting shall be provided. Access ladders, stairways,

platforms and handrails shall be maintained in a structurally safe condition and regularly inspected by a

competent person.

6.3.4 Adequate and safe drainage for all draining and flushing requirements shall be provided.

6.3.5 Any spillages or defects in equipment shall be reported immediately to a competent person.

6.3.6 Care shall be taken to avoid inhaling petroleum vapours during sampling operations.

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6.3.7 Floating roof tanks shall be sampled from the top platform whenever practicable as toxic and

flammable vapours may accumulate above the roof. When it is necessary to descend to the roof for

sampling, unless the atmosphere above the roof has been proved to be safe at least two persons

wearing self-contained breathing apparatus shall be present.

The second or other person(s) shall stand by at the head of the stairway where he (they) can clearly

observe the sampler on the roof. The sampler shall descend to the roof take the required samples and

return to the head of the stairway in the minimum time possible.

The following are some of the conditions that may render the atmosphere above the roof hazardous:

a) the product contains hydrogen sulphide and volatile mercaptans;

b) the roof is not fully floating;

c) the roof seal is faulty.

6.4 Static electricity

The following precautions shall be taken to avoid danger from static electricity when sampling tanks

containing flammable hydrocarbons stored at temperature above their flash points in which a flammable

atmosphere of hydrocarbon vapour or mist has been produced.

6.4.1 The contents of storage tanks, road vehicles, rail cars, ships or barges shall not be sampled during

filling especially when being filled with clean refined volatile products capable of giving rise to

flammable vapour air-mixtures in the ullage space.

6.4.2 When sampling, the sampling line should be kept firmly earthed at all times either by direct earth

connection or firm contact with the dip hatch to prevent sparking.

6.4.3 When sampling clean, refined volatile products including kerosene and gas oil which have been loaded

at a temperature near or above flash point or into tanks which are not gas-free, it is essential that a

relaxation time of 30 min after completion of transfer or loading into each tank or container shall be

allowed before introducing any conductive sampling equipment into the tank or container.

6.4.4 However, if one or more of the following apply, sampling may take place before the elapse of the 30

min relaxation time:

a) for a floating-roof tank, the sampling is carried out from a slotted dip pipe;

b) for a fixed-roof tank, the tank is fitted with an earthed floating cover;

c) the product contains sufficient static-dissipating additive to ensure an overall conductivity greater

than 50 pS/m and no mist or spray is being formed in the ullage space (see the note).

NOTE- Static dissipating additives can increase the conductivity of hydrocarbon liquids to a level sufficient to avoid the

accumulation of static electrical charge; an overall conductivity of 50 pS/m is acceptable. The relaxation time for a bound charge in

the body of a liquid is so short at this conductivity level that the charge is dissipated almost as it forms. As a result gauging and

sampling may take place without delay or even while filling is in progress so long as no mist or spray is being formed in the ullage

space. Charged droplets can exist in mists or sprays and produce an accumulation of static electricity regardless of the presence of

static dissipation additives in the liquid product.

6.4.5 Footwear capable of causing sparks shall not be worn in areas where flammable vapours are likely to

be present. Rubber footwear is not recommended in dry zones.

6.4.6 Clothing shall be of cotton or linen or wool and the wearing of synthetic fibres shall be avoided.

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6.4.7 Sampling shall not be carried out during periods of atmospheric electric disturbance or hailstorms.

6.4.8 In order to earth any static charge on his person, the operator shall touch some part of the tank structure

at least 1 m from any sampling opening immediately before carrying out any sampling operation.

7 PROCEDURES 7.1 Introduction

In this clause the general procedures that shall be applied for sampling homogeneous oils are described

and the additional procedures that shall be applied for sampling crude oil and non-homogenous oils are

described in clause 8.

Unless otherwise specified, multiple spot samples shall be collected using the detailed procedure relevant

to the particular application.

7.2 Precautions

7.2.1 General precautions

7.2.1.1 A sample shall not include material other than that to be sampled and if it is necessary to transfer a sample

from a sampler to a container, appropriate precautions shall be taken to preserve the integrity of the

sample.

NOTE - The transfer of a sample will usually have the following effects:

a) loss of light ends (affecting density and vapour pressure)

b) changes in the relative proportions of oil and contaminants such as water and sediment.

7.2.1.2 Sampling personnel shall be fully instructed in the relevant procedures. Correct and clearly defined

sampling and handling procedures are essential in order to ensure that samples are as representative as

possible of the material being sampled and are suitable for the tests required. Specific precautions are

necessary when drawing samples for certain tests and the correct sampling procedures shall be closely

followed to ensure that the test results are meaningful. These additional precautions do not form part

of this Standard, but shall be set out in the test method or product specification concerned.

7.2.1.3 For handling samples, use sampling equipment containers and receivers that are impervious to and

resistant to solvent action by the material handled (see 8.3)

7.2.1.4 Thoroughly inspect all sampling equipment including closures to ensure that it is clean and dry.

7.2.1.5 Leave at least 10% ullage in the container to allow for expansion. Decanting to obtain the 10% ullage is

not good practice because it will invalidate the representativity of the sample, particularly if any free water

or an emulsion layer is present. If spot samples are drawn from a tank some of the sample has to be

removed from the sample container and this shall be done immediately the sample container has been

withdrawn from the tank.

7.2.1.6 Immediately after filling and closing the receiver or container examine it closely for leaks.

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7.2.1.7 If large volume samples are required, which may not be obtained by the bulking of smaller quantities (because of

volatility or other considerations), mix the tank contents thoroughly by the means available (e.g. circulation tank

side mixer). Confirm the homogeneity by tests on samples taken at sufficient different levels as described in 7.7

and 8.2.1. The container shall be filled using a sample inlet extending to near the bottom of the container from tank

side taps a circulation pump bleed valve or by siphoning.

7.3 Samples for special analysis

If samples are taken for the determination of trace elements, for example lead, specially prepared sample containers may

be recommended in the method of test. Take such samples directly in the prepared container. Ancillary equipment and

sampling cord used shall in no way contaminate the sample.

7.3.1 If the tests for which the sample is intended include certain specific requirements such as copper or silver strip

corrosion take the sample in dark-coloured glassware and protect the sample from d i r e c t light prior to

testing. Any other method of obtaining the sample could affect the results of the corrosion test.

7.3.2 If tests for parameters such as water separation characteristics, oxidation stability, existent gum etc. are required

then take care to ensure that any sample container has been suitably prepared and is entirely free from contaminants

such as flux or other chemicals

7.4 Volatile materials

7.4.1 When taking samples of volatile crude oils and products, it is necessary to avoid the loss of light ends for example for

determination of density, vapour pressure or distillation, do not transfer or bulk oil from the original sample

container. Transport and store the sample in an inverted position to avoid loss of light ends through the closure.

7.4.2 Depending on the nature and temperature of the liquid the ambient temperature and the purpose for which the sample

is required, some or all of the following precautions may be necessary;

a. passing the sample through a sample cooler at the point of sampling;

b. cooling the sample container to a suitable temperature;

c. keeping the sample container cool until it has been sealed.

Sample containers may be cooled if necessary by immersion in a cooling medium e.g. crushed ice.

7.5 Tank side and pipeline sampling

If a tank side or pipeline sampling point is used adopt the following additional sampling precautions:

a) Before taking tank side or pipeline samples completely flush the sampling line to ensure removal of all

previous contents of the line.

b) The sample line outlet shall be designed to extend to near the bottom of the sample container during

sampling

c) If the material being sampled is volatile cool the sample container to a suitable temperature and

use an in line cooler if necessary.

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d) If the oil being sampled has a high pour point, it may be necessary to insulate the sample line thermally

or to provide means of heating the sampling connections in order to prevent solidification.

7.6 Labelling and transport

7.6.1 Clearly label sample containers; tie-on labels are preferred. Use indelible marking on the labels. It is

recommended that the following particulars be included in those recorded:

- place at which sample was drawn;

- date and time at which sample was drawn;

- initials or other identification mark of operator;

- description of material;

- quantity represented by sample;

- Tank No., package No. (and type) name of ship;

- type of sample;

- sampling device used.

It is recommended that details be recorded in a book kept for this purpose.

7.6.2 If samples are to be dispatched it is essential that care be taken to comply with the appropriate regulations.

If absorbent packing materials are used cover the cork or stopper with a paper, plastics or viscose cap in order to

prevent contamination of the sample on opening ensuring that the material used will not itself contaminate the sample.

7.7 Tank sampling

7.7.1 Shore tanks

7.7.1.1 Vertical Cylindrical Tanks

7.7.1.1.1 Spot samples

Lower the can or bottle/cage until its mouth is at the required depth open it in the appropriate manner and maintain

the sampling device at the required level until it is filled. In the case of a top sample lower the uncorked can carefully

until its neck is just above the surface of the liquid and then allow the sampler to fall sharply 150 mm below the

surface. When the sampler is full as indicated by the cessation of air bubbles withdraw it.

When sampling at different levels take the samples in sequence from top to bottom in order to avoid disturbance

at a lower level.

7.7.1.1.2 Composite samples

To prepare a composite sample transfer aliquot portions of representative individual samples into a composite

sample container.

NOTE- Evaporation of light ends and adhesion of water/sediment to the wall of the original sampler may influence the representative nature of the

sample (see also 7.4.1).

Do not prepare composite samples for testing unless they are specifically specified or agreed by the interested

parties. Otherwise, individual spot samples shall be tested and an overall value calculated from

the individual test results and the proportion of the bulk represented by each sample.

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7.7.1.1.3 Bottom sampling

Lower the bottom sampler until it rests in an upright position on the bottom of the tank. After

withdrawing the sampler, if necessary transfer the contents into the sample container, taking care that the entire

sample is properly transferred including any water or solids that may adhere to the inner walls of the sampler.

7.7.1.1.4 Interface sampling

Lower the sampler with the valve open to permit the liquid to flush through the device. At the level desired, close the

valve(s) and withdraw the sampler from the liquid.

If a transparent tube is used any existing interface can be detected visually through the wall of the sampling tube and

its position within the tank determined by measurement on the ullage tape. Check that the valves have properly

closed, otherwise resample.

NOTE - The sample may be retained for testing.

7.7.1.1.5 Tank side sampling

This is not a preferred method and therefore shall be applied only if no other way is possible.

The sampling valves shall be fitted to the side of the tank by connections extending at least 150 mm into the tank

except on floating-roof tanks, in which this is impossible. The lower connection shall be level with the bottom of the

suction pipe (see also 7.2.1.7).

Before a sample is taken, flush the tap or valve connection with the product to be sampled, and then draw off a

sample into a container or receiver.

CAUTION - Open the taps with care when sampling under pressure. Make no attempt to clear a blocked

connection by rodding through an opened valve.

If the contents of a tank fail to reach the upper or middle sample connections on a tank equipped with three

connections take the sample for the tanks as follows:

a) if the level of the contents is nearer the upper sample connections than the middle one, take two third of the

sample from the middle connection and one-third from the lower one.

b) if the level is nearer the middle connection than the upper take one half of the sample from the middle

connection and one-half from the lower one.

c) if the level of the contents is below the middle sample connection take all sample from the lower

connection.

7.7.1.1.6 All-levels sampling

This is not a preferred method, as it has not been established that such devices fill at a uniform rate. Make sure that the free drop or the regular withdrawal of the device is effective and that the device is not completely filled as it emerges from the oil (see also 5.4).

7.7.1.1.7 Running sample

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This is not a preferred method, as it has not been established that such devices fill at a uniform rate. To

obtain a running sample, use a bottle fitted to a weighted sampling cage (figure 2) and equipped if

necessary with a suitable device to restrict the filling rate (see figure 4). Lower the can or bottle/cage from

the surface of the oil to the bottom and raise it back to the surface at uniform speed and without stopping

at any point so that the bottle or can is about 75% full, but not more than 85% full when withdrawn from

the oil (see also 5.3.3).

7.7.1.2 Horizontal cylindrical and elliptical tanks

Samples shall be taken as spot samples as described in 7.7.1.1.1 from the levels indicated in table 1. If

they are to be combined to give a composite sample as described in 7.7.1.1.2 combine them in the

proportions given in table 1.

Table 1 a

Liquid depth

(percentage of

diameter)

Sampling level

(percentage of diameter above

bottom)

upper middle lower

Composite sample

(proportional parts)

upper middle lower

100

90

80

70

60

50

40

30

20

10

80

75

70

50

50

50

50

50

40

20

20

20

20

20

20

20

15

10

5

3

3

2

4

4

5

6

5

4

3

3

3

4

5

6

10

10

10

10

7.7.1.3 Miscellaneous tanks

Sample spherical tanks and tanks of irregular shape as described in 7.7.1.1.1. Determine the actual levels

at which the samples are to be taken to allow for the volume distribution over the height of the vessel.

7.7.2 Tanks on ships or barges

7.7.2.1 General

The total load capacity of a vessel is normally subdivided into a number of compartments that may vary in

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size. Draw spot samples from each compartment as described in 7.7.1.1.1.

If the composite sample is required, prepare this as described in 7.7.1.1.2.

7.7.2.2 Sampling non-inerted, non-pressurized vessels

Use the procedure described for sampling vertical cylindrical shore tanks (see 7.7.1.1).

7.7.2.3 Sampling inerted but depressurised vessels.

In order to prevent the infusion of oxygen into the tank atmosphere, open tanks in a consecutive manner

for sampling. Use the respective sampling/gauging pipe and the sampling procedures described in 7.7.1.1.

NOTE _ In order to minimize infusion of oxygen into the tanks, the number of tanks opened for sampling should not be more than

that number laid down by terminal/port/vessel regulations and should relate to the construction of the vessel.

7.7.2.4 Sampling inerted and pressurized vessels

Use an appropriate device for this purpose (see 5.5)

7.7.3 Rail cars

See 7.7.1.2

7.7.4 Road vehicle tanks

See 7.7.1.3

7.8 Sampling of tank residues/deposits

Tank residues are organic and inorganic sediments forming a layer on the bottom of either marine or land-

based tanks. At ambient temperatures the material is unpumpable and of soft to stiff consistency.

Samples of tank residues/deposits will not be representative and shall only be used for guidance regarding

their nature and composition.

The sampling method to be applied depends on the depth of the layer remaining in the tank. Up to a

thickness of 50 mm a grab is the preferred device. For its use the manufacturer's operating instructions

shall be followed. Because of the dimensions of a grab the sampling aperture may have to have a hatch or

a manhole.

For sampling of layers deeper than 50 mm, a borer method shall be applied using either a gravitation tube

sampler for soft residues or a ram tube sampler for stiff residues or any other suitable equipment. These

devices often have small enough diameters to be inserted into the tank through the normal gauging and

sampling aperture. When using this equipment follow the manufacturer's operating instruction.

Transfer the sample from the device into a metal plastics or glass container, which shall maintain the

integrity of the sample.

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7.9 Package sampling

7.9.1 Statistical aspects of sampling packages

7.9.1.1 Number of samples to be taken

7.9.1.1.1 General

The variability of the material both within and between packages, the number of packages sampled and

the precision of the test methods may all contribute to errors in the determination of the properties of the

material as shown by the test results. The number of samples to be drawn will depend on the number of

units of product, the percentage defects acceptable (AQL) and the inspection level. The following

recommendations as to the number of samples to be taken give a qualitative assessment of the errors

involved.

7.9.1.1.2 Sampling to assess uniformity in a package

Draw spot samples from evenly distributed points within the material. Test each sample using a simple

test based on an easily assessable characteristic such as density, colour etc. Any variations in the test

results in excess of the repeatability of the test method indicate that the material in the package is not

uniform.

7.9.1.1.3 Sampling to assess the average quality of a batch.

A batch consists of a number of packages of a product of a single composition:

a) Single package

If the material has been shown to be uniform (see 7.7.1.1.1) take a single spot sample, but if not take a

sufficient number of spot samples and combine them to give a representative sample.

b) Multiple packages

The accuracy with which an estimate of the average quality of the material within a number of

packages can be made is dependent on

1) the number of packages sampled,

2) the precision of the test method used,

3) the variability of the material between packages.

It is strongly recommended that all the packages in a consignment be sampled in order to eliminate the

majority of these errors.

7.9.1.1.4 Sampling of whole consignment

If all the packages are sampled, this necessarily involves the greatest amount of sampling and the error in

the determination of the average quality will depend on the testing of the samples.

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If each of the samples is tested once, the average of the test results will be a measure of the average quality

with the lowest uncertainty. If a representative sample is prepared and is tested once the result will be a

measure of the average quality but with a much higher uncertainty.

7.9.1.1.5 Sampling of part of the batch

It is recognized that it is not always possible to sample all the batch and plans are given to enable a

decision to be made as to the number of discrete samples which need to be taken from a batch in order that

a valid conclusion may be arrived at regarding the quality of the total contents of all the packages

7.9.1.2 AQL

The AQL used for this Zambian Standard shall be 2.5%

7.9.1.3 Inspection level

The inspection level determines the relationship between the lot or batch size and the sample size (number

of packages per batch the required number of samples). The normal inspection level (see ISO 2859) shall

be used for this International Standard.

7.9.1.4 Sampling plan

7.9.1.4.1 General

A sampling plan indicates the number of units of product from each batch which are to be inspected

(sample size or series of sample sizes) and the criteria for determining the acceptability of the lot or batch

(acceptance and rejection numbers) (see table 2.)

7.9.1.4.2 Single sampling plan

The number of sample units inspected shall be equal to the sample size given by the plan. If the number

of defectives found in the sample is equal to or less than the acceptance number (see 'Ac' in g table 2b),

the lot or batch shall be considered acceptable. If the number of defectives is equal to greater than the

rejection number (see Re in the table 2b) the lot or batch shall be rejected.

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7.9.1.4.3 Double sampling plan

The number of sample units inspected shall be equal to the first sample size given by the plan. If the

number of defectives found in the first sample is equal to or less than the first acceptance number (see

table 2c) the lot or batch shall be considered acceptable.

If the number of defectives found in the first sample is equal to or greater than the first rejection number

31

(see table 2c) the lot or batch shall be rejected.

If the number of defectives found in the first sample is between the first acceptance and rejection numbers

(see table 2c) a second sample of the size given by the plan shall be inspected. The number of defectives

found in the first and second samples shall be accumulated. If the cumulative number of defectives is

equal to or greater than the second rejection number, the lot or batch shall be rejected.

NOTE - Instructions on the use of the plans to determine acceptability of the batch is given with each plan (see also 7.9.1.4)

7.92 Procedures for sampling packages

7.921 Drums and barrels

Place the barrel on its side with the bung up. If the drum does not have a side bung, stand it upright and

sample from the top. If detection of water, rust or other insoluble contaminants is desired, let the barrel or

drum remain in this position long enough to permit the contaminants to settle.

Remove the bung and place it beside the bunghole with the oily side up. Close the end of the clean dry

sampling tube with the thumb, and lower the tube into the oil to a depth of 300 mm. Remove the thumb,

allowing oil to flow into the tube. Again close the upper end with the thumb and withdraw the tube. Rinse

the tube with the oil by holding it nearly horizontal and turning it so that the oil comes into contact with

that part of the inside surface that will be immersed in the oil during the sampling operation.

Discard the oil used to rinse the tube and allow the tube to drain.

Insert the tube in the oil again, holding the thumb against the upper end. (If an all levels sample is

required insert the tube with the upper end open.) When the tube reaches the bottom, remove the thumb

and allow the tube to fill. Replace the thumb, withdraw the tube quickly and transfer the contents to a

sample container. Do not allow hands to come into contact with any part of the sample. Close the sample

container; replace and tighten the bung in the drum or barrel.

7.9.2.1 Cans

Obtain samples from cans of 20 l capacity or larger in the same manner as from drums and barrels (see

7.9.1.1.3) using a tube of proportionately smaller dimensions. For cans of less than 20 l capacity, use the

entire contents as the sample, selecting cans as described in 7.9.1.1.5 or as otherwise specified.

7.10 Pipeline Sampling

7.10.1 Non-homogenous liquids

See Clause 8

7.10.2 Homogenous liquids

Sampling shall be done from a suitable pipeline sampling apparatus (see 5.7). Before a sample is

drawn, flush the sample line and valved connection with the product to be sampled, after which draw

off a sample with a sample container or receiver, taking into account the precautions given in 7.5.

NOTE: The contents of the pipelines may be under considerable pressure and therefore special procedural precautions and

32

equipment will be necessary (see 6.3). It is recommended that a pressure gauge be provided in the line at each sampling point to

enable the pressure to be read before sampling. The line service should be clearly labelled and updated at the change of service.

8. PROCEDURES FOR CRUDE OILS AND OTHER NON-

HOMOGENOUS LIQUIDS 8.1 General

If available, automatic pipeline sampling as specified in ISO 3171 shall be used for sampling crude oil

and non-homogenous oils in preference to the following manual procedures. This procedure is

applicable to crude oils and other non-homogenous oils such as so-called heavy crude oils and

residual fuels. The manual sampling methods specified in clause 8 will not provide representative

samples for the following reasons.

a) The concentration of dispersed water in the oil is generally higher near the bottom of a tank.

The running sample or the composite sample of the upper, middle and lower samples may not

provide a sample representative of the concentration of dispersed water.

b) The interface between oil and free water is difficult to locate, especially in the presence of

emulsions, layers or water bearing sludges.

c) The free water level may vary across the tank bottom surface. The bottom is often covered by

pools of free water or water/oil emulsion impounded by layers of sludge or wax.

d) Light ends can be lost easily in manual operations, affecting the density and vapour pressure

of the sample.

Because circumstances will arise where manual methods of sampling have to be employed, procedures

are given in this clause which shall be followed so that a sample may be drawn which is as

representative of the bulk as the techniques allow. The procedures specified are additional to or replace

those specified in clause 7.

8.2 Procedures

8.2.1 For tank sampling, use one of the following techniques specified in 7.7:

Spot sampling

Running sampling

All levels sampling

If the spot sampling technique is used, draw samples initially from the upper, middle and suction

levels, transport them to the laboratory and test them for density and water by standard methods.

If the results of these tests lie within the repeatability limits of the average value, the samples may be

considered as representative of the bulk. However, if this is not so or if it is not possible to test the

samples prior to completing the sampling, draw samples at metre intervals, measured from the bottom

of the suction level of the tank to the surface of the liquid (see figure 1). If the outlet pipe turns down

33

into a small sump of less than 1500 l capacity, take the lowest sample at the bottom of the tank.

These samples are to be tested and the results used to compute the properties of the contents of the

tank.

8.2.2 For pipeline sampling use the procedures described in ISO 3171.

Give particular attention to the precautions referred to in respect of the following:

a) high pour point oils (see 7.2.1)

b) volatile oils (see 7.4)

c) collection of large volume samples (see 7.2.1.7)

d) ullage to be left in sample containers (see 7.2.1.5)

e) samples for transportation (see 7.6 and 8.6)

8.2.3 Transport samples of crude oils to the test laboratory in the original sample container, without transfer

or compositing (bulking) in order to maintain the integrity of the sample. If it is impossible to

transport the sample in the original container, transfer it to a suitable container following the procedure

specified in 9.4 and record the transfer. Transport and store the sample container in an inverted

position, if feasible.

8.2.4 The requirements relating to sample handling are summarized in clause 8.3 and shall be strictly observed.

8.3 SAMPLE HANDLING

8.3.1 General

8.3.1.1 The method of handling samples between the point at which they are extracted or drawn and the

laboratory test bench or sample storage are devised to ensure that the nature and integrity of the sample

are maintained

8.3.1.2 The method of handling a sample will depend on the purpose for which it has been taken. The laboratory

analytical procedure to be used will often require a special handling procedure to be associated with it.

For this reason consult the appropriate method of test so that any necessary instructions as to sample

handling can be given to the person drawing the sample. If the analytical procedures to be applied have

conflicting requirements, then draw separate samples and apply the appropriate procedure to each sample.

8.3.2 Take particular care in respect of the following:

a) liquids containing volatile material since loss by evaporation can occur

b) liquids containing water and/or sediment since separation tends to occur in the sample container;

c) liquids with potential wax deposition, since deposition can occur if a sufficient temperature is not

maintained

34

8.3.3 When making up composite samples, take great care not to lose light ends from volatile liquids and not to

alter water and sediment content. This is a very difficult operation and should be avoided if at all possible.

8.3.4 Do not transfer samples of volatile liquids to other containers at the sampling location but transport them

to the laboratory in the original sample container cooled and inverted, if necessary. Great care is

necessary if a sample contains both volatile components and free water.

8.4 Homogenisation of samples

8.4.1 Introduction

Procedures are specified for the homogenisation of samples that may contain water and sediment or are in

any other way non-uniform, before transfer from sample container to smaller containers or into laboratory

test apparatus. Procedures for verifying that the sample is satisfactorily mixed before transfer are given in

8.5.

It is not possible to agitate manually samples of liquids containing water and sediment sufficiently to

disperse the water and sediment within the sample. Vigorous mechanical or hydraulic mixing is necessary

in order to homogenize the sample prior to transfer or sub-sampling.

Homogenisation may be by various methods. Whichever method is used, it is recommended that the

homogenizing system produce water droplets below 50 µ m but not less than 1 µ m. Water droplets of

below 1 µ m will give a stable emulsion and the water content cannot then be determined by centrifuge

methods.

8.4.2 Homogenisation by high-shear mechanical mixer

Insert a high shear mechanical mixer into the sample container so that the rotating element reaches to

within 30 mm of the bottom. A mixer with counter rotating blades operating at about 3 000 min-1

is

usually suitable. Other designs may be used if the performance is satisfactory.

In order to minimize loss of light ends from crude oils or other samples containing volatile compounds,

operate the stirrer through a gland in the closure of the sample container. Mix until the sample is

completely homogenized. A mixing time of 5 min is sometimes sufficient, but the size if the container

and the nature of the sample affect the homogenisation time. Verify that the sample has become

homogenous (see 8.5).

NOTE - High shear mixers frequently produce stable emulsions and water contents after stirring cannot be determined by the

centrifuge method (ISO 3734).

Avoid any significant rise in temperature during the mixing.

8.4.3 Circulation with external mixer

This method can be applied to both permanently sited sample containers and portable containers; for the

latter, use a quick-disconnect coupling. Circulate the contents externally using a small pump through a

35

static mixer installed in small-bore piping. Various designs are suitable; follow the manufacturer's

operating instructions.

Use a circulating flow rate sufficient to circulate the contents at least once per minute. A typical mixing

time is 15 min, but this will vary according to the water content, the type of hydrocarbon and the design of

the system. When the whole sample is thoroughly mixed run off the required quantity of sub-sample from

a valve in the circulating line, whilst the pump is running. Then empty the container and thoroughly clean

the entire system by pumping solvent round until all traces of the hydrocarbon have been removed.

8.5 Verification of mixing time

8.5.1 Whenever means are chosen for obtaining a sub-sample from a non-homogeneous mixture, verify the

suitability of the mixing technique and the time required to obtain a suitably mixed sample.

8.5.2 If the sample remains homogeneous and stable after mixing (e.g. where completely miscible components

such as lubricant additives have been blended) continue the mixing procedure until successive samples

drawn from the main bulk of the sample give identical results. This establishes the minimum mixing time.

NOTE - As the sample is homogeneous after this time and will remain so transfers from the main bulk can be made without

further mixing.

8.5.3 If the sample does not remain homogeneous for more than a short period of time after mixing (e.g. if

water and sediment are part of the mixture) use the special method for the verification of mixing time

described in 8.4.

NOTE - It may be necessary owing to the characteristics of the hydrocarbon to sub-sample while mixing is still in progress.

8.5.4 Ensure the sample as drawn fills the container to about three-quarters full and homogenize the sample for

a known period of time that shall be recorded. During this period draw off small portions at regular

intervals and test each immediately for water content by a standard method (see 8.4). When the test results

are consistent record the value obtained as the blank water content.

Add an accurately measured quantity of water between 1% and 2% and homogenize for the same period

of time as for the blank and take samples as before. If there is good agreement between the water content

determined taking account of the blank water content and the quantity of water added then repeat by

adding a further accurately measured quantity of water again between 1% and 2%. If the results continue

to give good agreement then assume that the mixing time is adequate.

If the results do not show good agreement (within the repeatability of the method) then discard them.

Revert to the beginning of the procedure and use a longer period of mixing.

8.5.5 Do no determine water content by the centrifuge method (ISO 3734) for this verification of the mixing

system as the method cannot be relied upon to give the total water content.

8.6 Transfer of samples

8.6.1 If the sample container is not portable, or if it is inconvenient to take samples directly from the container

into laboratory test apparatus, transfer a representative sample into a portable container for transport to the

laboratory.

8.6.2 At every stage of transfer of a sample it is essential to homogenize the contents of the container from

DZS 396-1: 2018

Third Edition

which the sample is being taken using one of the methods specified in 8.4.

8.6.3 Verify the mixing time for each combination of container and mixer by one of the methods specified in

8.5.

8.6.4 Complete any transfer of sample within the period during which the mixture is known to be

homogeneous and stable. This period is short do not take longer than 20 min to complete any transfer.