Part 1 - Test and Performance Specifications for Type Approval of Oil Content Meters

  1.1.1 This test and performance specification for type approval relates to oil content meters for oil discharge monitoring and control systems for oil tankers. A meter may be tested for one of several specified applications (crude oils, black products, and white products) and the certificate of type approval should clearly indicate the accepted application(s). In addition, the electronic and measuring section of the oil content meter should be tested in accordance with the specification for environmental testing contained in part 2 of this annex.

  1.1.2 The meter being tested should satisfy all the relevant requirements contained in section 6 of these Guidelines and Specifications.

  1.2.1 A meter designed to operate over a wide range of oil content should measure the true oil content of the sample entering the meter during each test within ±10 ppm or ±10%, whichever is the greater, and testing should be performed in accordance with the procedures detailed in paragraphs 1.2.5 to 1.2.18 of this specification. The accuracy should remain within these limits in the presence of contaminants other than oil and ±10% variations from design criteria with respect to power (electricity and compressed air).

  1.2.2 A diagrammatic arrangement of a test rig for evaluating the performance of oil content meters is given in figure 1. The accuracy of the oil content meter should be determined by comparing its readings with a known flow of oil injected into a known flow of water. The grab samples taken should be analysed in a laboratory by the method described in paragraph 1.3 of this specification. The results of the laboratory analysis will be used for correlation and to indicate sampling and test equipment variability. The water flow rate should be adjusted so that the entire oil-water flow passes through the oil content meter, except the intermittent grab sample stream. Special care should be given to keep, continuously, a constant oil content in the water that flows into the meter. The oil and contaminant metering pumps should be adjusted to deliver a steady flow. If oil injection becomes intermittent at low concentrations, the oil may be premixed with water to provide continuous flow, if absolutely necessary. The oil injection point should be immediately upstream of the oil content meter inlet to minimize time lags caused by the sample system. Wherever No.2 crude oil is specified in particular tests, a similar crude oil may be substituted, provided that the oil selected is used throughout the tests.

Test rig

  1.2.3 The sampling arrangement should be such that a representative homogeneous sample is obtained under all conditions of operation and under all operational proportions of oil content. The sample should be obtained from the full flow through the meter, but when this is impracticable, the sampling arrangements shown in figure 2 should be used. Special care should be taken in collecting and preserving the sample to ensure validity of the resultant findings.

Alternative sampling arrangement in test rig

  1.2.4 Should the oil content meter incorporate a filter or other device for removing solid contaminants from the mixture to be tested, such a device should be regarded as part of the oil content meter and be connected during all the tests. After completion of the contaminant, tests referred to in paragraph 1.2.10 the device used to remove solid contaminants from the mixture should be opened up and the residues inspected to ascertain that they do not contain significant amounts of oil.

  1.2.5 Calibration and zero test. The oil content meter should be calibrated and zeroed in accordance with the manufacturer's instructions. It should then be tested using the No.2 crude oil at the following concentrations in ppm 0, 15, 50, 100, 200 and at intervals of 200 up to the maximum of the meter's highest range. A complete calibration curve should be constructed. Each concentration test should last for 15 min. After each concentration test the meter should be run on oil-free water for 15 min and the reading noted. The instrument should not be re-calibrated in spite of any movement from zero.

  1.2.6 Response tests. Different oil types - After calibration in the previous test, the oil content meter should be tested at concentrations of 15 ppm, 150 ppm and 90% of the maximum full-scale with the following oils. Additional concentrations may be added if required to construct a complete calibration curve for each of the following oils:

 Notes

1 Reference for these parameters is Institute of Petroleum publication - Petroleum Measurement Paper No.8 - ISBN 0 85293 2.

2 This viscosity is recorded at 40°C due to this oil's high pour point which renders the kinematic viscosity not measurable at 20°C.

* Density in kg/m³ at 15°C; this parameter is reported by conversion using table 3 of the Petroleum Measurement Tables - ASTM D 1250-80.

** Kinematic viscosity (Cst) at 20°C.

*** Cloud Point in °C.

 Note

Other oils covering the range of properties shown may be substituted if those shown are unobtainable.

The characteristics of the oil and age of sample shall be recorded. Samples used for approval must be less than 12 months old.

 Following each test, the meter should be run on oil-free water for 15 min and the meter reading recorded. Should the meter reading at zero oil through put exceed the accuracy requirement, an automatic cleaning device should be fitted to the instrument as standard. If it is necessary to re-zero, recalibrate, or clean the meter between tests, this fact and the time required to recalibrate or clean the meter should be noted and recorded on the certificate.

  1.2.7 White petroleum products. If the meter is considered suitable for "white" petroleum products, it should also be tested with the following products in a manner similar to the tests set out in paragraphs 1.2.5 and 1.2.6:

• .1 Automotive gasoline;

• .2 Kerosene; and

• .3 Marine distillate fuel oil – DMA – ISO 8217:2010/Corr 1:2011 (tables 1 and 2).

If the meter is to be considered suitable for any of the category C and D oil-like noxious liquid substances referred to in the list contained in the unified interpretations to regulation 14 of Annex II of MARPOL 73/78, it should also be tested against each such substance for which approval is required, in a manner similar to the tests set out in paragraphs 1.2.5 and 1.2.6. The high shear pump shown in figure 1 should be kept in operation at high speed during this test to assist in dissolving the appropriate fraction of the substance in the water stream.

  1.2.8 If the meter is to be considered suitable for an individual biofuel blend containing 75 per cent or more of petroleum oil, it should also be tested against each such substance for which approval is required, in a manner similar to the tests set out in paragraphs 1.2.5 and 1.2.6. The high shear pump shown in figure 1 should be kept in operation at high speed during this test to assist in dissolving the appropriate fraction of the substance in the water stream.

  1.2.9 Individual Biofuel blends should be tested at 75 per cent and 99 per cent petroleum oil.

  1.2.10 Response times. The oil content meter should be run on oil-free water and zeroed. The oil injection pump, set to 100 ppm No.2 crude oil, should be turned on.

The following response times should be recorded and included on the certificate:

• .1 time for first detectable reading;

• .2 time to read 63 ppm;

• .3 time to read 90 ppm; and

• .4 time to read 100 ppm or for reading to stabilize at maximum, the value (ppm) of which should be recorded.

Following this upscale test, the oil injection pump should be turned off and the following response times should be recorded and included on the certificate:

• .5 time for the maximum reading to drop detectably;

• .6 time to read 37 ppm;

• .7 time to read 10 ppm; and

• .8 time for reading to stabilize at minimum, the value (ppm) of which should be recorded.

The response time of the meter, which should be taken as the average of the response time recorded to read 63 ppm and the response time recorded to read 37 ppm, should be less than 20 s.

  1.2.11 Oil fouling and calibration shift tests. Two tests using No.2 crude oil should be performed to determine the effect of oil fouling on calibration shift. The first test should be done with a 10% oil concentration and the second with a 100% oil concentration.

For the 10% oil concentration test, the meter should initially be running on oil-free water. The high capacity oil injection pump, set to give 10% oil in water, should be turned on for 1 min and then turned off.

For the 100% oil concentration test, the meter should be running on oil-free water. The water should be turned off and 100% oil turned on for 1 min. The oil should then be turned off and the oil-free water flow resumed.

Care must be taken in the design of the test equipment to ensure that the oil fouling test results are not degraded by fouling of the sample piping external to the meter.

The following response times should be noted for both tests and recorded on the certificate:

• .1 time for first detectable reading;

• .2 time to read 15 ppm;

• .3 time to read 100 ppm;

• .4 time for reading to go off scale on the highest range;

• .5 time for reading to return back on scale on the highest range;

• .6 time for reading to return to 100 ppm;

• .7 time for reading to return to 15 ppm; and

• .8 time for reading to return to zero or stabilize at minimum ppm reading.

If it is necessary to clean the meter after each oil fouling test for it to return to a zero reading, this fact and the time required to clean and recalibrate the meter shall be noted and recorded on the certificate.

After successful completion of both oil fouling tests, a 100 ppm mixture of No.2 crude oil should be introduced and any calibration shift noted and recorded on the certificate.

  1.2.12 Contaminant tests. The meter should be run on contaminant test as follows:

• .1 the contaminants should be mixed in the mixing tank with clean water as follows:

  not less than 270 ppm by weight of attapulgite (see note (a)) and 30 ppm by weight of iron oxides (see note (b)). Each material should be mixed sequentially in the mixing tank to the following criteria:

  • 1.1 attapulgite for a period of not less than 15 min so that a homogenous suspension is formed; iron oxides for an additional period of not less than 10 min. The mixing process should maintain the contaminants in suspension throughout the test period;

• .2 the meter should be run on a mixture of clean water and No.2 crude oil of 15 ppm;

• .3 the water supply should be changed from clean water to contaminated water;

• .4 any shift in the meter reading should be noted in the certificate. The meter reading should be within the accuracy limits specified in 1.2.1;

• .5 the test specified in .2, .3, and .4 above, should be repeated with oil concentrations of 100 ppm and 300 ppm; and

• .6 sufficient water should be available in the mixing tanks to ensure an effective test period of not less than 15 min.

Notes:

(a) Attapulgite is a clay mineral with the chemical formula (MgAl)₅Si₈O₂₂(OH)₄4H₂O and is stable in both fresh and salt water. The test contaminant should have a particle size distribution with about 30% of 10 microns or less and a maximum particle size of 100 microns.

(b) The term "iron oxides" is used to describe black ferrosoferric oxide (Fe₃O₄) with a particle size distribution of which 90% is less than 10 microns, the remainder having a maximum particle size of 100 microns.

  1.2.13 Air entrainment test

• .1 The meter should be run on a mixture of water and 15 ppm No.2 crude oil.

• .2 Air should be injected into the test circuit immediately before the sample pump or, in the absence of such pump, immediately before any conditioning unit used to prepare the mixture for measurement. Injection should be by needle having an orifice dimension not exceeding 0.5 mm in diameter arranged in line with the sample flow. The quantity of air injected should be 1% of the designated flow rate of the sample pump or conditioning unit at the point of injection. Air should be delivered to the system by direct injection or pump via a suitable measuring device designed to permit a constant controllable flow rate within ±10% of the required rate of injection for an uninterrupted effective test period of not less than 15 min.

• .3 Any shift in the meter reading should be recorded on the certificate.

• .4 The tests specified in points 1, 2 and 3 should be repeated with an oil concentration of 100 ppm and 300 ppm respectively.

  1.2.14 Oil particle size - shear pump test. The meter should be run on a mixture of water and No. 2 crude oil of 100 ppm. The high shear pump, shown in figure 1, should be run at various speeds to provide a range of oil particle size to the meter and on completion of this test the pump should be stopped. Any effect of particle size on the meter reading should be noted and recorded on the certificate. The purpose of this test is to demonstrate that the meter's accuracy is not significantly affected by the oil droplet size or by the degree of oil and water mixing.

  1.2.15 Temperature test. The meter should be run on a mixture of water and No.2 crude oil of 100 ppm. The water temperature should initially be set at 10°C and then at 65°C. If the manufacturer's specification lists an operating maximum water temperature of less than 65°C,the meter should be run at that maximum temperature and this fact, together with any effect of water temperature on the meter reading, should be recorded on the certificate.

  1.2.16 Sample pressure or flow test. The meter should be run on a mixture of water and No.2 crude oil of 100 ppm. The water pressure or flow rate of the mixture should be adjusted from one-half normal, to normal and to twice normal. Any effect of these changes on the meter reading should be recorded on the certificate. This test may require modification, depending on the flow characteristics of the meter.

  1.2.17 Shut-off test. The meter should run on a mixture of water and No.2 crude oil of 100 ppm. The water and oil injection pumps should be shut off and the meter left on with no other changes made. After eight hours, the water and the oil injection pumps should be turned on and set to provide a mixture of 100 ppm. The meter readings before and after each test and any damage to the meter should be recorded on the certificate. This test also determines the proper functioning of the low flow shut-off and alarm.

  1.2.18 Utility supply variation test. The meter should be run on a mixture of water and No.2 crude oil of 100 ppm. The supply voltage should be increased to 110% of the nominal value for one hour and then reduced to 90% of the nominal value for one hour. Any effect on meter performance should be recorded on the certificate.

If the operation of the meter requires any utilities besides electricity, it should be tested with these utilities at 110% and 90% of the design figures.

  1.2.19 Calibration and zero drift test. The meter should be calibrated and zeroed in accordance with the procedures in the manufacturer's instructions manual. A mixture of water and No.2 crude oil of 100 ppm should be run through the meter for eight hours and any calibration drift recorded on the certificate. Following this, the meter should be run on oil-free water and any zero drift recorded on the certificate.

  1.2.20 Shut-down and re-energization test. The meter should be shut down and de-energized for one week. It should be turned on and started in accordance with the manufacturer's instructions. After the suggested warm-up and calibration procedures, the meter should be run for a period of eight hours, operating alternatively for one hour on a mixture of water and No.2 crude oil of 100 ppm and for one hour on oil-free water. After each step in the operation, any zero or span drift should be recorded on the certificate. The total time required to perform the manufacturer's suggested warm-up and calibration should also be recorded on the certificate.

  1.2.21 Reporting of test results. A specification of the instrument concerned and a diagrammatic presentation of the test arrangements should be provided to the Administration by the manufacturer when applying for type approval and the following data should be reported in the international metric system of units:

• .1 types and properties of oils used in the tests;

• .2 details of contaminants used, in the form, for example, of a supplier's certificate or laboratory test protocol; and

• .3 results of tests and analysis of grab samples.

The recommendations of the manufacturer of the oil content meter concerning the choice and application of cleansing agents used for cleaning purpose should be recorded in the appendix to the type approval certificate.

The size of the mixing tank should be specified so as to allow a minimum "once through" effective test period of 15 min. Adequate arrangements should be made for in-tank mixing or recycling to ensure a homogeneous mixture.

 The determination of the oil content will be performed according to the International Standard ISO 9377-2:2000 "Water quality - Determination of hydrocarbon oil index - Part 2: Method using solvent extraction and gas chromatography" that specifies a method for sampling and subsequent determination of the hydrocarbon oil index in water using solvent extraction and gas chromatography. This method should be used for the determination of oil content requirements outlined in these Guidelines and Specifications.