This research was carried out with the sole aim of monitoring interface in the transportation of petroleum pipeline products and the analysis of this product from Enugu depot.  In the research it was observed that product contaminates each other if interface was not properly monitored and cut at the appropriate time.

The three major products that were considered in this research were premium motor spirit (PMS) automotive gas premium (AGO0 and dual purpose kerosene  (DPK).

The tests carried out point test smoke point test, initial and final boiling point test (Distillation), temperature and density test, to ascertain the standard quality specification and the extent of their purity.

It was observed from the result that the flash point value for DPK and AGO were 430c and 820c respectively.  The average smoke point test values for DPK product was 21.92mm.  the initial  and final boiling point of PMS were350c and 1750c, respectively.   The observed density at the DPK/AGO interface monitoring test were 819 kg/m3 and 850 kg/m3 and corrected densities for DPK and AGO were 830.2kg/m3 and 859.9kg/m3 respectively. The interface reception cut point for DPK/AGO interface  monitoring was made at the corrected density of 849.0 kg/m3.  And the temperature of DPK and AGO were 310c respectively.

The result from the analysis revealed that the boiling point of PMS was far more lower than that of AGI and DPK, which implies that PMS has a higher volatility than the two other products the flash point test revealed that the minimum temperature at which AGO and DPK ignites was 66.50c and 430c PMS was not determined because of its high volatility.  Also, the standard minimum smoke point of DPK was determined to be 22mm.  The smoke point test for AGO and PMS were not carried out because, they were not domestically used and their combustion normally takes value in an engine.

This research has become very necessary because it reveals the proper way pf handling petroleum pipeline product to meet standard specification for domestic and industrial use.



1.0 Introduction

1.1     Historical perspective

1.2     Introduction to petroleum transportation by pipeline

1.3     Product movements and handling

1.4     Batching procedure

1.5     Interface detection and control

1.6     Interface growth

1.7     Product quality control

1.8     Sample

1.9     Product contamination


2.0              Literature review

2.1       Historical review of interface

2.2              Pipeline hydraulics

2.3              Laminal and turbulent flow

2.4              The Reynolds number

2.5              Operating philosophy


3.0              Experimental method/ procedure

3.1       List of laboratory equipment

3.2              Experiment method

3.3              Interface monitoring test (first step)

3.4              Experimental test on the various pipeline product (second step)

3.4.1        Flash point test

3.4.2        Smoke point test

3.4.3        Distillation test

3.4.4        Temperature and relative density test


4.0              Experimental results


5.0              Discussion


6.0              Conclusion


7.0              Recommendation




1.0              INTRODUCTION



As an instrument of transport, the pipeline is almost as old as the wheel.  Indeed, one of the big problems facing earning civilizations in their development of the first cities was the provision of an effective water supply, and the inventive clines are believed to have used bamboo pipes for this purpose as much as 7,000 year ago.  The Syrians the Egyptians, the Greeks and the Romans all used water mains made of clay or hollow stone, and in 525 B.C.  the king of Persia supplied his desert arm with water by means of a pipeline made of sown oxetride.

The problem of bulk transport of oil arose an soon as the modern international oil industry itself was in Pennsylvania in 1859.  During the early days of the industry the uniform method of moving crude oil or refined products in bulk was by barrels.  These were loaded on to wagons trains or ships like any ordinary merchandise.  However teamsters owning wagons were charging such exorbitant have age was sought.  Pipeline appeared the obvious answer and after some encouraging experiments with wooden pipes the first commercially successful oil pipeline was built in 1865.  this line, 2 in diameter was made of cast iron could handle 250 tones of oil per day.  Its advantages over wagons and barrels for over land transport was instantly appreciated by other petroleum dealers, and very soon many more lines were in service.  steel began replacing cast iron about the year 1910, and a proliferation of pipelines resulted.

It has many year been accepted that whereas pipeline for cheaper transportation than road or rail tankers, they cannot compete on equal terms with ocean going tankers and are this economically dependent on the fact that they can usually be laid on a short alignment than the corresponding sea have.

Product lines in any country depend upon the development of a large concentrated market area.  Pipeline constitute the most economical method of transporting large volumes of fluid under these conditions.  Under normal conditions a pipeline can transport products at about one quarter the cost of a comparable movement burial are even greater.  In addition, pipeline can compete economically with all types of in land large movements.


The commercial transportation of petroleum is done in bulk so as to take the advantage of the economy of seal and thereby reduce unit cost of shipment.  Moving the commodity in bulk required the use of read tanker trucks rail wagons, pipeline and ocean- going vessel however among by three hinter land means of transportation by rail wagon, pipeline and road truck, transportation by pipeline remain the cheapest and safest.

At independence, in 1960, multinational companies such as Mobil supplied Nigeria’s petroleum product needs through the importation of petroleum products, total British petroleum  (now African petroleum) and ESSO (now OANDO) the first refinery in Nigeria was owned by BP- shell and was commissioned in 1965 shortly before the out break of the civil was that spanned the period 1966-1970.  The refinery, with the daily capacity of 35, 000 BSD become grossly inadequate to meet the national consumption at the end of the civil war in 1970.  This was due largely to the unprecedented high level of economic activities engaged upon by the federal government to re-construct and rehabilitate the damage done to infrastructure during the civil war.

The federal government subsequently built and commissioned the warri refinery and constructed and company (WRPC) in 1972 constructed and commissioned 30lkm of pipeline with its associated petroleum storage depots in 1979/80 under the pipeline phased.  182 project.  In addition, it constructed and commissioned the Kaduna refining and petrochemical company (KRPC) in 1979.  The pipeline phase 182 comprise five systems for ease of operations namely 2A, 3B, 2C, 2D, and 2E.  this network was expanded under the pipeline phase 3 to a total of 4950km, to link all the three refineries in the country in 1995 and designated system 2CX,2DX,and 2EX.

The nation wide NNPE pipeline system with its associated bulk petroleum storage depots, therefore, brought the supply of white petroleum products close to major cities and towns in Nigeria.  The depots are located at Lagos (at satellite), Atlas cove, Ibadan Ilorin, Ore, Benin, Warri, Port Harcourt, Aba, Enugu, Markurdi, Yola, Suleja, Minna, Kaduna, Kano, Gombe, Gusau, Jos and Maiduguri. These depots are linked by pipelines of various sized ranging between 6 to 16 no her in diameter.Only the calabar depot is not linked to the pipeline network.

Consequently, government through the NNPC took over the importation of petroleum products into Nigeria, after the findings of the oputa panel of Enguiry in  1975 to examine the root cause of the refining and storage facilities and pipelines to link these storage centers.  This culminated in the construction and commissioning of ht 125, 00 bld capacity warri refinery in 1978, the phases 1 and 2 pipeline system along with 17 storage depots in 1979 and the 110,000b/d capacity Kaduna refinery in 1980.

The commissioning of the Kaduna complex enable the nation to produce base oils for the manufacturing of engine oils and bitumen for road construction


The NNPC headquarters of the Nigerian products pipelines system has the primary function of coordinating the safe movement of products through the entire pipeline system its scheduling group is responsible for overall planning of product movements is coordination with the dispatching group at the port Harcourt control center the system 2E port Harcourt to Makurdi pipeline dispatching group under deputy chief engineer operations is responsible for implementing the schedule and adjusting for short term scheduling changes.  This function also involves the handling of information from locations remotely controlled by the port Harcourt control center.

To dispatchers require accurate current information on all movements. Efficient operation of the pipeline requites very close cooperation of filed and disputing personal.

NNPC headquarters will prepare system 2E, port Harcourt to Makurdi pipeline pumping schedules.  This schedule will normally provide pumping rates used as the basis of preparing the schedule.  From the NNPC schedule the dispatchers will prepare detailed 15 day pumping and delivery schedules based on actual pumping rates and stripping rates of products leaving the line at delivering points.

The dispatcher at the port Harcourt control center will supply port Harcourt station, Aba, Enugu, AND Makurdi with switching times gravities and supplemental information relative to each operation.

Any unusual incidents or circumstances related to product hardly or product quality must be reported to the port Harcourt dispatcher at once.


Scheduling activities should be accomplished in such a manner as to ensure the at the least operating the required product volume group of NNPC headquarters is responsible for planning all shipments throughout the entire system.

However, a 15-day pumping schedule will be issued weekly by the port Harcourt control center and revised as required. Schedulers at NNPC headquarters and operating personnel at port Harcourt and depot stations will  view the 15-day pumping schedule to ensure they  have a mutual understating of the planned movement both at origin and dewberry  terminal if this review indicates a conflict or minister predation  of the schedule, the local operations supervisor will contact the supervisor of pipeline control at port Harcourt control center for clarification.

A quarterly product movement forecast will be issued by the NNPC hindquarters for   planning purpose.

Dispatening personnel at port Harcourt are to furnish all depot stations with updated delivery times at least 1 day prior to delivery.


Normal batching procedures are to be developed around the following sequence to refined  products in a cycle.


A detailed review product contamination limits and initial batch volumes indicates that is to be kept uncontaminated or PMS if DPK is to be kept uncontamination.  It is recommended    that AGO be transported before DPK to avoid contamination of DPK.

In subsequent years and when the batch volumes of DPK grow larger, the normal initial cycle may be revised and altered to suit future operating conditions.

However, petroleum products, such as various grades of motor and aviation gas line, kerosene propane butane and some light diesel fuels which are pumped in the appropriate batching sequence may be transported in the same product pipeline.  Interface contamination is not a serious problem in a properly operated system. However where extreme purity is required mechanical separators may be inserted at the required product interface.



The supervisory control and date Acquisition system will provide for the accurate tracking of batch deliveries within the pipeline.  Each batch will be identified by a unique batch number.  The batch number will consist of a three- character product code followed by a three- digit sequence number.  The product code will designated by the operator when scheduling a batch or by the computer, if an unscheduled batch is initiated . in either case the product codes will be designated as follows. 

PMS-   Premium motor spirit

RMS-  Regular motor spirit

DPK-   Dual purpose kerosene

AGO – Automotive gas oil

HFI     - High flash interface

LFI-     Low flash interface

The sequence number will be assigned sequentially by the system at the same time that the product code is entered scheduled batches will be assigned number in the range of from 600 through 899.  unscheduled batches will be assigned number 900 through 1999


The cut point for batch changes are based on initial yearly theoretical human batch volume during a normal batching cycle and on equations proposed by J.E Austin and J.R Palfrey. if batch volume are reduced in a subsequent cycle or if a batch is eliminated from a subsequent cycle dispersion of may take several subsequent blending cycles to comply with contamination limits as specified in below contamination limits.

*          The batch cut point and slop distribution at Enugu and ABA are as follows

Interface                      Cut at

Leading-trailing          (%by volume)                          Cut to

PMS-   RMS                15% RMS       RMS product tank

RMS-  AGO               1% AGO         PMS-1slope tank

RMS-  AGO             65% AGO     AGO 1 slope tank

RMS-  AGO             99% AGO   AGO product tank

AGO- DPK                 5% DPK          AGO-2 Slope tank

AGO- DPK                 100% DPK      DPK product tank

DPK- PMS                  Trace PMS      PMS- 2slope tank

DPK-   PMS                99& PMS        PMS product tank

it should be noted that the cut points should are based on a certain shaped interface. In some cases, the interface shape may vary and therefore the most desirable cut points might be different than those given in the preceding table.  It is stressed that actual operating data must be obtained before definitive limits are established for cut points.

To accomplish an accurate batch split, the operator must obtain in advance, the specific gravities (corrected for temperature) for each product to be received.  This information to be provided by the chemist, is critical to make accurate switched and minimize contamination.


In multi- product pipelines it is necessary for different products or grades of products to follow one another in direct constant the mixture between the two is know as the interface.  Pipeline interface are divided into two categories.

Critical interface and non critical interface.

Critical interfaces occur between incompatible products such as motors spirits (low when point) and gas oil (high flash point) when the specification of one can be seriously affected by the other.  Serious intermixing will put both products off specification.

Non- critical interface occur between two grades of the same group such as premium and regular motor spirits.  Nevertheless the permissible contamination of one on the other is strictly limited.  At worse

*          Serious intermixing can only put the higher grade off specification.

Table 1 below show the product’s specific gravity and colour which are the determining factors for the detection of interfacial mixtures.


1.6              INTERFACE DETECTION

Interface generated between products are automatically detected and recorded by the Nusonic interface detected or they can be detected by sampling the interface mixture with the hydrometer will assembly in the sample building.  Another method which would in the used only for special conditions utilized spheres launched during batch changes.

A hydrometer is a device which consists of a glass cylinder and a graduated scale used to determine the specific gravity of a fluid or a mixture of fluids by sampling an interface mixture at certain time intervals and recording the readings in the product change report.

The Nusonic interface detector is an electronic instrument which detects and records changes in the sound velocity of fluids. Batch changes passing by the probe are displayed graphically in the control room as a gravity trend indicating the beginning and end of an interface.  The gravity trends are automatically corrected to C00F (1560C) 0 psig cokglm2

By a microprocessor

During the initial operation of the system the manual  detection of interfaces by hydrometer and colour sampling will be made.  The local operation will then either make the cut or tell the dispatchers when to cut.

The interface detector is best used for making batch cuts which are made at the first trace of interface or heat cut.  It can be easily seen on the graph when the specific gravity first begins to change by a sudden deviation from a straight line.  Batch cuts that are made at some point other than the end points of an interface should be made using hydrometer reading.

It is suggested that the practice of manual detections of interface by hydrometer and colour sampling continue as detector.

In order to accomplish manual determination of specific gravity have ASTMD 1250 available for              gravity corrections to 600F (15.60c)

1.6                   INTERFACE GROWTH

In is know that after the first 150km or so of travel, the elongation rate falls off and further growth is insignificant

Interface growth is affected by:

-                                  Pipe diameter

-                                  Pipe length

-                                  Relative densities and hence viscosity of adjoining products

-                                  Flow rate (turbulent flow must be mainted)

-                                  Pressure surges/ siphoning due to insufficient back pressure

-                                  Shunt downs (can add 10% to length each time)

-                                  Bad operating procedures (ie. In correct line stopping and starting allowing line to slacken)

-                                  Manifold value changes (must be quick to reduce growth at input to pipeline)

-                                  Rurming spheres in the interface (this can reduce growth by up to 30/40%)



a.                     In order to minimize interface growth, the following practice should be adopted

1.                              The pressure in the line must not be allowed to fall to a level which would create the damages of the hydraulic gradient cutting any point on the line profit

2.                              Where booster pumps are used, flow rate must kept balanced throughout the system.

3.                              interface parking should be reduced to a minimum .

4.                              maximum pumping rates should be maintained with an interface is in the line

5.                              line shunt down and start up sequencing that ensure that the line is always kept packed under constant.

6.                              operating process dares that ensure interface which have to be parked are not parked in areas of idly changing ground profile

b.   During design of the systems, the following factures can be incorporated so as to minimize interface growth:

-                                  Fast acting manifold values to minimize mixing of product at input to the pipeline

-                                  Flow control monitoring which ensure that the pipe-line always operated in the turbulent flow region.

-                                  Pipe-line always operates in the turbulent flow region.

-                                  The use of ramped flow control values at each receipt point and pump station to give a smooth and quick acceleration of product on start up.


One of the key skills of pipelining is to maximize through  put at minimum cost.  A well operated system is one in which all of he interface material generated is either disposed of by down grading into adjacent  products within agreed contamination limits or by delivery to segregated slop tanks for subsequent blending by ret injection into incoming grades (whilst still maintaining overall on-specification product).  It follows that the volume of interface material to be absorbed limits the parcel sizes of products and this affects the volume of tankage to be provided for a given system.


Interface contamination at the receipt point can be handled in several ways:

-                       All interface material can be cut into one slop tank for either

·         Return to the nearest refinery: this includes considerable cost for transportation and refinery handing

·         Re- injection: this has disadvantage that thee is a 50/50 mixture of both products present.

-                       The interface can be cut into 2 (or more )portions:

·         Each portion can be taken directly into main storage tanks.  This is particularly applicable to non-certical interfaces   

·         Each portion can be cut into separate slop tanks for re-injection into products received from the line

1.7                   PRODUCT QUALITY CONTROL


1.                     GENERAL

The purpose of quality control at the different stages of reception storage and delivery is to ensure that the products:

-                                  Delivered by suppliers are in accordance with the specifications,

-                                  During storage, keep their characteristic

-                                  In certain cases of pollution by other product or impurities will remain useable,

-                                  When being leased into delivery road tankers have not been subject to incorrect handling


-                                  A short analysis of certain products upon reception (flash point, viscosity degree of the GO)

-                                  A laboratory analysis in order to check the phyisco- chemical characteristics of a product whenever the latter is in force or whenever it does not fall into the category of polluted products to be re injected with out analysis


-                                  Take a sample at the pipeline outlet in the depot.  These samples are considered by the depot as check sample in the case of possible dispute.

-                                  Each sample should be visually examined by the depot managers.

-                                  In addition, gas-oil samples are subjected to a short analysis

-                                  Sample are kept in the depot until one month after the stocks constituting the batches received have been normally disposed of.

After this time they are re-used normally.

NOTE:     Samples are taken as soon as possible and examined in accordance with a standard to be agreed and procedure described in a later chapter. Visual examination of samples can be followed by a partial or complete analysis of the physco-chemical characteristics in the case of questionable products.

No pumping is to take place before the examination have shown that the product complies with the specifications.


-                                  BEFORE PUMPING INTO PARTIALLY FILLED TANKS

-                                  Take an all level sample from each of the tanks to be topped up with the products received.

-                                  Sample are considered as check sample of the characteristics of the products contained in the tanks to be topped up.

-                                  Sample are re-used after normal disposal of he whole stocks contained in the tanks

-                       WHEN PUMPING:

When gas- oil of a specified plash point is received:

-                                  Take a sample from the receiving line within half an hour following the start of pumping and check the flash point.

-                                   After one hour’s pumping take a sample from the receiving tank and check the flash point.

-                                  After the 1st hour and every hour take a sample from the receiving line and check the flash point.

-                                  In each case, the time at which the sample was taken and the time at which the sample was checked shall be mentioned in the sample entry book.  The name of the persons taking the sample and checking the flash point shall be also indicated.

If pollution is noticed, pumping is to be stopped immediately until the cause of pollution is discover and content of receiving tank checked.

-                                  AFTER PUMPING INTO TANKS

When  sample are taken from the tanks, two possibilities may occur:

-                                  The total bulk to which the sample refers is homogeneous (case of a normal overall reception): an average sample is to be tanker

-                                  The total bulk is heterogeneous case of deliveries of the some product spread over a certain period possible topping up a number of partial samples at different depths must be taken

-                                  WHEN BEING STORED

-                                  When  analysis proves to be necessary for a periodic check on the stability of the product being stored a samples is to be taken from the tank (s) concerned

-                                  Send the sample (s) to the laboratory responsible for quality control.

-                                  A check sample of he same quality control

-                                  A check sample of the same quantity and quality is kept at the depot

-                                  TEST POLLUTED PRODUCTS

When it is necessary to perform a check analysis of a polluted.  Product which does not fall into the category of the products which can be directly re-injected into tanks, take send the sample (s) to the laboratory responsible for quality control.

A check sample of the sample quantity and quality is kept at the depot.


Carry out visual examination in order to avoid incorrect handling of the product upon loading of vehicles.

-                 MULTIPLE TESTING

If the number of results obtained in either one or both laboratories is more than one, then the allowable difference between the averages from the two laboratories is given as follows.


Difference             R1        =          (R2- r2 (1-1/2n1-1/2 n2)


                  R         =          reproducibility of the method

                  r           =          reproducibility of the method

                  n1         =          number of results of the first laboratory

                  n2         =          number of results of the second laboratory




-                                  Product identification

-                                  Check the degree of purity

-                                  Appearance- transparency

-                                  Search for water and or sediments

-                                  Colour to be compared with the colour indicated by the standard.

-                                  Measurement of the specific gravity

-                                  Volume mass (or specific gravity) to be compared with the standard          



-                                  Complete visual examination

-                                  Flash point


-                                  Complete analysis (checking of the characteristics indicated by the reference standard)

-                                  Partial analysis (checking of certain characteristics)  



Generally applications for analysis are to be accompanied by detailed information.  They shall comprise:

-                                  The identification of the sampling operation

-                                  Place of sampling

-                                  Name of operator

-                                   Date of operation

-                                  serial number of operation

-                                  The identification of the batch where the sampling comes from:

-                                  Name of product

-                                  Quality of he batch to which the sample refers,

-                                  Type of sample (upper, average, partial etc)

-                                  Quality sent to laboratory.

-                                  The specification of the work requested from laboratory:

-                                  Nature of tests (complete analysis   partial analysis, indicate whether a check sample is kept at the depot, indicated the tank level/ levels that the sample/partial sample were taken from)

-                                  Any research of a specific nature (indicate all elements likely to be of help to the laboratory)


Moreover, reference to the above indications is to be made on the label which is attached to the vessel containing the sample so that it is possible to relate this label to the application for analysis.

A book opened each year with a single series of numbers will be used in each depot to record the different applications for analysis.



According to the extent of the analysis, the following quantities shall be taken.                                                                                                                                                                                                                                          


Type  of examination complete analysis

Kerosene P.G.R.G.O 20litres

In laboratory

Partial analysis

Octane number poor mixture



Gums, distillation vapour pressure



Visual examination (colour specific gravity smell)




On site

Short analysis (visual examination flash point viscosity




1.8                   SAMPLE


Samples of petroleum and petroleum product using various ASTM methods for the determination of physical and chemical characteristics.  It is accordingly necessary that the samples be truly representative of the petroleum or petroleum product question. The precautions required to ensure that representative character of the samples are numerous and depend upon the type of product being sampled the tank the carrier or container from which the sample is being obtained, the type and cleanliness of the sample container, and the sampling procedure that is to be used.  A    summary of he sampling procedures and their application is presented in table 2. each procedure is suitable for sampling a number of specific materials under definite storage transportation or container conditions.  The basis principle of each  procedure is to obtain a sample or a composite of several samples in such manner and from such the sample or composite will be truly representative of the petroleum or petroleum product.

However, samples of petroleum and petroleum products are examined by various methods of test for the determination of physical and chemical characteristics. The test results are often used for custody transfer and pricing determinations.


For a sample to be value, it should meet the following conditions.

-                                  It must be reproceducible (ie taken from the product bulk)

-                                  It must be unpolluted (ie contains the product only especially if the latter is itself polluted)

-                                  Precise indications of what it should be clearly marked (labeling)

-                                  The sample must not be likely to deteriorate after being taken or during transportation (packing)

-                                  The amount of the sample must be large enough for test measurements to be made  (do not forget that sampling means taking a responsibility)



-                                  The total to which the sample refers is homogeneous (ie, as in the case of an overall normal reception)

-                                  The total bulk to which the sample refers is not homogeneous (ie as in case of deliveries of the same product spread over a certain period)

Therefore, it is first of all necessary to ascertain the homogeneous or heterogeneous character of the product to be sampled.  This can be done by taken specific gravities at different depths

If the bulk is homogeneous an average sample can be quit safely taken at any level

If the total bulk is heterogeneous a partial sample can betaken.  If necessary, a number of partial sample taken from different depths of a single bulk can be made up.


NOTE:           A difficulty arises when a sample is to be taken from a storage tank for products of different specific gravities may have been pumped in. in this case layering occurs and the layer are disposed in decreasing order of specific gravity from the bottom up.  Dispersion occurs slowly and the rate of dispersion is directly proportional to the viscosity of the product.  The contents of a tank are practically always heterogeneous.

1ST CASE:      In order to study the layering of the contents of tank, samples are taken at different depths by means of a bottle which can be opened at the depths selected and then securely closed again to ensure that the bottle contains a sample from the selected depth only

2ND CASE:     If an average sample is required, it is possible either to lower the weighted bottle and with liquid at all level: or to take a great number of samples at different levels with which an average sample can made up.  This method is the best as viscosity does not influence the outcome.

1.8.1                                DIFFERENT KNDS OF SAMPLES

-UNIFORM PETROLUM PRODUCT:    One in which spot sampled from top, upper middle, lower and outlet agree within the precision of laboratory tests.  Similarly in pipeline transfers, spot samples taken at 120,50 and 80% of the total volume agree within the precision of the laboratory tests.

-A SAMPLE: represent a small portion of its total volume of material (for example tanks, ships, compartments, container and pipeline tenders ) obtained with precision equal to or better than the precision of the laboratory method by which this sample is to be analyzed.

- “OFFICIAL” SAMPLE:   a sample taken t the point of custody transfer and used for the custody transfer laboratory determination

- AVERAGE SAMPLE:      Consists of proportional quantities taken from all level of the tank.  When a sampling probe which collects the product gradually over its whole depth in the tank, is used the sample obtained is called an “all levels” sample.

-“ ALL LEVEL” SAMPLE:           Is obtained by immersing the closed sampling tube or the stopped sample bottle as close as possible to the drain level and by opening this vessel and raising it so that it is nearly but not completely filled when it emerges from the liquid

- TOP SAMPLE:      Is taken from the middle of the upper third of the contents of the tank.

- MIDDLE SAMPLE:          Is taken from the middle of the contents of the tank

- BOTTOM SAMPLE:         Is taken from the middle of the lower third of the contents of the tank.

- MIXED SAMPLE FROM A SINGLE TANK:  Consists of a mixture of top, middle and bottom samples.  The average sample representative of the whole tank is made up by mixing in the following proportions the samples take at the three levels.

Upper zone                                          1part

Intermediate zone                               3part

Lower zone                                         1part

- OUTELT SAMPLE:          Is taken at the drain nozzle of the tank.

-TUBE OR THIEF SAMPLE:        A sample obtained with a sampling tube or special thief either as core sample or spot sample from a specified point in the tank or container.


1.8.2                                SAMPLING EQUIPMENT

-                                              Sample containers: may be clear or brown glass bottles or comes. The clear bottle is advantageous because it may be examined visually for cleanliness and also allows visual inspection of the sample for free water or solid impurities.  The brown glass bottle affords some protection from light

-                                              PLASTIC BOTTLES:   Made of suitable un pigmented linear polyethylene may be used for the handling and storage of gas oil fuel oil and lubricating oil.  They should not be used for gasoline, aviation jet fuel kerosene crude oil, white spirit, medicinal white oil and special boiling point products unless testing indicates there is no problem with solubling contamination or loss of light ends

-                                              CONTAINER CLOSURE:                   Cork or glass stoppers or screw caps of plastic or metal, may be used for glass bottles, screw caps only tight closure seal.  Corks must be of good quality, clean and free of holes and loose hits of cork. Never use rubber cork may be prevented by wrapping tin or aluminum foil around the bottle glass stoppers must be or perfect fit. Screw caps must be protected by a disk faced with tin    


1.9                                      PRODUCT CONTANMINATION

Contamination can be define as the defilement or desecration of one product by the other contaminated product may be detected at the pump stations and the delivery stations by means of either interfaced detectors or hydrometer or color analysis from the sample points.  When it is discovered that contaminated product is in the line before delivery is started, the senior supervisor  depot ; and deputy chief engineer operations should be notified immediately.  The deputy chief engineer operation will then decide on the disposition of the product.

In the event contaminated product is noticed at a delivery station, the line is to be shut down immediately.  The deputy chief  engineer operations, will decide on the disposition of the product.

Initiate a search to determine the cause of contamination.

1.                                                      Test samples wherever available

2.                                                      check all block and bleed value for leakage



Design criteria for slop blending rates at the depot are based on contamination limits as follows.
























Specific blending rates for blending slop with product will depend on the refinery product specifications and the specification of the slop.  Each case must be analyzed by the chemical before proceeds.




1. The WRONG estimated time of interface arrival given by dispatchers to the quality control section: quality control personal are supposed to be at the point of product interface arrival two hours before the arrival of interface

however, there had been instances when the interface had passed into the receiving tank before the two hours that the personnel supposed to be at the interface point, this lead to product contamination.

Also there had been an instance when a quality control personnel was at the interface point for eight hour before the arrival of interface.

2.The second source of product contamination is during product blending: usually when products are to be blended, one should make the theoretical calculation of the products to be blended, followed by a practical laboratory test of the blend.  The laboratory test is  supposed to be the guide, also, a five to ten (10%) percent limits is given as gap in case of human error or equipment malfunction.  However, most operators do not follow this procedure, instead, they like to take short-cuts that results in further product contamination.

Product blending is done to reduce waste in the amount of slop products. The product blending is done as trial blends before the actual blending so as to ensure that the resultant blend is not adversely affected as well as product performance.  However, the laboratory trial blends are done, and tested for the result and blend flash point (except PMS), distillation And density.

3. The third source of product contamination is value malfunction at the depot: when values are not well seated as a result of accumulated dirts  product in another tank. This see page gradually accumulates and result in contamination.

4. The fourth source of contamination is during product reception, when wrong tank is opened for a different product entirely during line-up for reception. However, before the mistake  is realized and corrected, the tank product would have been contaminated.

5. The fifth but the least source of product contamination is by the universal liquid-water: usually the mixture of water with any product is not considered to be contamination.  However, if it becomes a persistent affair that forms a nuisance like the historical Jos depot product tank, it then becomes a contamination

6. The sixth source of product contamination is by tanker switch leading at the depot.  This is being done by AGO and DPK switch loading.  If a tanker is not adequately drained before loading with another product, this may result in contamination of product.



Two major type of contamination occurs in products handling namely:

1.      Solid impurities contamination

2.      Product- to-product contamination


The solid impurities are removed by:

- STRAINERS:         Use of wire mesh to trap coarse materials that can cause damage to pumps and meters e.g. metal pieces broken pieces, of pig brushes etc.

- FILTERS:               This device uses clay earth or fiber glass to capture fine particles that can clog pum and measuring turbine meters e.g. rust scale, water etc.

- SETTING TANK: Uses no flow and density differences.




Means of controlling product contamination include:

a) SPHERES SERAPPERS, PIGS:            It is used for cleaning pipeline but also used to keep products apart to avoid contamination

b) HYDROMETERS:          Used to identify different type of products by specific gravity, thereby resulting in neat cuts.

c) PRESSURE AND BACK PRESURE:  Keep the pipeline packed to reduce product spread and mixture at shut down

d) HEART CUT:      At intermediate terminals, making the delivery out of the center of he batch

e) VALUE CLEANING:     Proper value cleaning and service in the various depots to ensure that there are no debris dirts.


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