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INTERFACE MONITORING
AND ANALYSIS OF PIPELINE AND PRODUCTS MARKETING COMPANY LIMITED ENUGU DEPOT.
ABSTRACT
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.
TABLE
OF CONTENTS
CHAPTER ONE
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
CHAPTER TWO
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
CHAPTER THREE
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
CHAPTER FOUR
4.0
Experimental results
CHAPTER FIVE
5.0
Discussion
CHAPTER SIX
6.0
Conclusion
CHAPTER SEVEN
7.0
Recommendation
References
Appendices
CHAPTER ONE
1.0
INTRODUCTION
1.1
HISTORICAL PERSPECTIVE
PIPELINE TRANSPORT
OPERATION
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.
1.2
INTRODUCTION TO PERTOLEUM TRANSPORTATION BY PIPELINE
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
1.3
PRODUCT MOVEMENTS AND HANDLING GENERAL
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.
1.31
PRODUCT MOVEMENT SCHEDULE
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.
1.3.2
SEQUENCE OF PRODUCT MOVEMENT
Normal batching procedures are to be
developed around the following sequence to refined products in a cycle.
DRAWING
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.
1.4
B`ATCHING PREDURES
1.4.1
BATCH IDENTIFICATION
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
1.1.2
CUT POINTS FOR SATCH CHANGES
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.
1.5
INTERFACE DETECTION AND CONTROL
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%)
1.7
MINIMISATION OF INTERFACE GROWTH
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.
INTERFACE
CONTAMINATION
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
EXAMINATIONS AND
ANALYSIS
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
QUALITY CONTROL MAY
CONSIST OF
-
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
1.7.1
DIFFERENT TYPES OF QUALITY CONTROL – UPON RECEPTION
-
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.
-
TEST AFETR LOADING THE DELIVERY VEHICLES
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)
Where:
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
1.7.2
TYPE OF EXAMINATION OR ANALYSIS
a)
VISUAL EXAMINATION AND FIELD ANALYSIS
-
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
b) SHORT ANALYSIS
-
Complete visual examination
-
Flash point
c) LABORATORY
EXAMINATION
-
Complete analysis (checking of the characteristics indicated by the reference
standard)
-
Partial analysis (checking of certain characteristics)
1.7.3
APPLICATION FOR ANALYSIS
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.
QUANTITATIVE EXTENT
OF SAMPLES.
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
|
2litres
|
|
|
Gums, distillation
vapour pressure
|
1litre
|
|
|
Visual examination
(colour specific gravity smell)
|
1litre
|
|
On site
|
Short analysis
(visual examination flash point viscosity
|
1litre
|
1.8
SAMPLE
SAMLING OF PETORLEUM
AND PETROL FUM PRODUCTS
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)
THERE EXIST TWO
POSSIBILITIES
-
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
CONTAMINATION LIMITS
Design criteria for slop blending rates
at the depot are based on contamination limits as follows.
CONTAMINATE
|
Product
|
PMS
|
RMS
|
DPK
|
AGO
|
|
PMS
|
100%
|
5.0%
|
0.5%
|
0.5%
|
|
RMS
|
5.0%
|
100%
|
0.5%
|
0.5%
|
|
AGO
|
0.1%
|
0.1%
|
5.0%
|
100%
|
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.
SOURCE OF PROCUT
CONTAMINATION
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.
TYPE OF PRODUCT
CONTAMINATION
Two major type of contamination occurs
in products handling namely:
1.
Solid impurities contamination
2.
Product- to-product contamination
1.SOLID IMPURITIES 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.
2. PRODUCT-TO-PRODUCT
CONAMINATION
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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