Scope
This guideline provides instructions for performance verification of an
automatic sampling system.
Frequency Once during commissioning of a sampling system and anytime operating
conditions differ in excess of operating conditions observed during
successful testing of the sampling system.
WATER INJECTION TEST OF AUTOMATIC SAMPLING SYSTEMS PROCEDURE
RESPONSIBILITIES:
2.1 The plant foreman will be responsible for ensuring compliance
with the instructions outlined in this procedure.
2.2
The shift coordinator will be responsible for ensuring that crude
oil source tanks with minimum level of 40 feet are provided two
days in advance of the scheduled date of the test. Alternatively,
where crude is supplied through pipeline, at least 8 hours of
uninterrupted flow is assured on the day of test.
2.3 Coordinate with OSPAS to arrange the shipment for required
flow levels normally for the day of test.
2.4 The crude tank farm supervising operator will be responsible for
ensuring the designated tanks are thoroughly mixed and water
drained as many times as possible prior to the scheduling date.
The tanks must be sampled for %BS&W. This will be the base
BS&W.
2.5 The nominated test coordinator will be responsible for:
2.5.1 Ensuring the field equipment is prepared and thoroughly
checked as outlined in this procedure.
2.5.2 Ensuring that the involved Operations personnel are
intensively instructed in their respective duties.
2.5.3 Ensuring that the laboratory personnel are informed one
week in advance of the scheduled test dates.
3. PRE-TEST INFORMATION
3.1 Sampler Identification:
Identify the sampler to be tested by
make and serial number. Normally there is more than one
sampler at the same site. Fill the data sheet Supplement-1.
Make sure the probe insertion length is optimum and its crude
collecting tip facing the upstream.
3.2 The test will be witnessed by representatives of Custody
Measurement Unit/ESD/CSD (Tel.874-6164) and MINPET. CMU
will notify MINPET a month in advance of the test requesting
them to furnish their representative’s name.
3.3 A field test is conducted by injecting an accurately measured 1%
maximum volume of water into the crude oil stream from 500 –
1000 meters is required for mixing in the pipeline before getting
into sampler.
3.4 The test is carried out in accordance with the API Manual of
Petroleum Measurement Standards, Chapter 8, Section 8.2.12
4. MIXING TEST:
A procedure for proving the adequacy of the sample receiver and mixer
is comprised of the following steps:
4.1 Optimum Mixing Time:
4.1.1 Clean the receiver with xylene as described in Sec.5.2
below. Add a known volume of usually collected oil per
day, relatively dry oil to the sample receiver. Mix the
known volume of oil and withdraw the representative
sample into the centrifuge tubes and determine the
percent sediment and water by centrifuge method.
4.1.2 Prepare samples with known sediment and water
contents by adding measured amounts of water to the
measured amounts of relatively dry oil that contains only
dissolved or entrained water. These measured water
volumes are poured directly into the sample receiver.
Recommended volume of added water should be 0.5 to
2% to provide good readability level during the test.
4.1.3 Mix the known sample. While mixing withdraw samples
into centrifuge tubes each minute starting at 5 and ending
at 15 minutes.
4.1.4 Measure the S&W content by centrifuge method.
Determine optimum mixing duration by comparing the
results with the known percent, i.e., optimum mixing time
is the closest time which has produced same percent of
S&W as was actually mixed.
4.2 System Performance:
4.2.1 After determining the optimum mixing time, repeat steps
4.1.1 to 4.1.2. Mix the known sample for optimum time.
Measure the S&W of the contents by centrifuge method.
The test results should be within repeatability limits
defined in the analytical technique. This determines the
system performance.
5. TESTING THE SAMPLER:
5.1
Install a water injection manifold at the selected location. This
consists of a calibrated flow meter, a check valve and a block valve.
Water source shall be from the nearest firewater outlet any other one.
Note: When the test is completed, the manifold assembly should be left
in place until the results of the test have been analyzed and found to be
acceptable.
5.2 Before testing the sampler, the following procedure shall be
carried out on the sampler.
5.2.1 Stop the sampler. Close the fast loop pump suction and
discharge valves if the sampler has them.
5.2.2 Drain the sampler container/reservoir and associated
piping completely.
5.2.3 Pour two gallons of toluene or xylene into sample
reservoir and circulate for ten minutes.
5.2.4 Drain the reservoir and piping completely.
5.2.5 Inspect the sample reservoir internally, checking that it is
fully drained and cleaned. Box-up the container. Re-open
the car seal and fast loop pump suction and discharge
valves.
Check manual block valves to be used for the test are
easily operable.
6. TESTING LOADING METER AUTO SAMPLER
1. Testing will be done during loading to the ship for new sampler
at each berth for each metering system.
2. Set the batch volume as advised by metering engineer
3. Start the auto sampler fast loop
4. Record opening reading of the meters selected for the test
5. Set the flow rate to minimum possible
6. Continue to transfer for I hour. Stop the sampler grab pump by
entering a zero setting to the Durant counter.
7. Drain the sampler reservoir ready to receive the dry oil (without
water)
8. Start the sampler grab pump, simultaneously recording the
meter reading and time.
9. Stop the sample grab pump when instructed by the test
coordinator. Simultaneously record the meter closing reading
and time.
10. Mix the reservoir contents for ten minutes
11. Two samples will be drawn by laboratory technician and
identified as “Baseline Sample1”.
12. Drain the sample reservoir.
13. When instructed by the test coordinator:
14. Record the opening water meter reading.
15. Open the fire hydrant.
16. Adjust the manual block valve upstream of the water meter to
the rate required.
17. Start the sampler grab pump; simultaneously record the meter
opening reading and time.
18. When instructed by the test coordinator:
19. Stop the sampler grab pump. Simultaneously record the meter
closing reading and time
20. Close the manual block valve at the water meter.
21. Record the stop time and meter closing reading.
22. Mix the sampler reservoir contents for 10 minutes
23. Two samples are drawn by the lab technician and identified as
“Water Injection Samples”.
24. Drain the sample reservoir.
25. Continue with the oil circulation to allow any water left in the line
to be purged out.
26. When instructed by the test coordinator, start the sampler grab
pump; simultaneously record the meter opening reading.
27. When instructed by the test coordinator, stop the sampler grab
pump; simultaneously record the meter closing reading.
28. Stop the pump, close down the line-up. Record the tank gauge,
temperature, closing meter readings.
29. Stop the pump, close down the line-up. Record the tank gauge,
temperature, closing meter readings.
30. Mix the sample reservoir contents for 10 minutes.
31. Two samples will be drawn by the lab technician and identified
as “Baseline Sample 2”.
32. Drain the sample reservoir. Now the test is complete.
WATER INJECTION TEST DATA SHEET-1
