The contents of the German proposal cannot be applied to the testing of all kinds of skimmers. For example, the test method of this proposal cannot be applied to a skimmer which has no capability of functioning in the absence of the propulsive force of the ship carrying the skimmer. As we proposed last year, our opinion is, therefore, that the scope of the application of this test standard be clearly defined. The following contents, therefore, should be added, as proposed before.

　

This test standard shall be applied to the stationary type of skimmers which is possessed of the purpose of recovering oil spread on the surface of the water, provided that the skimmer incorporates a pump into the skimmer itself or is designed to work in combination with other means of fluid transfer.

The equipment of collecting oil on water surface, which operates utilizing the ship's propulsive force when carried onboard an oil-recovery exclusive ship or vessels-of-opportunity is outside of the scope of this standard.

　

Necessity exists for having a reason when laying down any requirement for the shape of the water surface of test tank. However, the reason for the necessity of having the equilateral triangle as the shape of the water surface cannot be found from this test method.

It is anticipated that the skimmer to be tested would have disadvantage if the test area has the shape of an equilateral triangle. In the case of the test area having the shape of an equilateral triangle, when performing tests with high viscosity oil, the corner angle of a triangle being less than a right angle, some amount of oil scattered inside the angle would not be able to move toward the skimmer due to the viscosity and adhesiveness.

Though weir type or adhesion type skimmers, which have excellent performance, will be capable of collecting almost all the oil floating over the test area, they will not be able to collect and recover the oil attached to the inside corner of the triangle. For this reason, the quantity of the oil spread at the beginning of the test will become meaningless and the performance results of the skimmer will be influenced unfavorably.

As the effect of the wall forming the test area has nothing to do with the performance or efficiency of the skimmer, it should be disregarded to the maximum extent.

　

The skimmer is assessed for its performance by finding how fast the speed of the oil recovery at the surface of the water is made, so the test time should not be specified.

Some skimmers of high performance may complete the recovery of the recoverable oil in far shorter a time than that laid down. Then, the remaining time will be left for the high performance skimmers to continue to operate meaninglessly (i.e. operating at the no-oil water surface), resulting in no more oil recovery. This result will be recorded as the skimmer's performance. While there is no significant impact comparatively for the adhesion-type skimmers, the weir type skimmers recover only water at the water surface which has no oil, thus resulting in the "reduction in oil recovery efficiency".

As an example, when a low viscosity oil test (subparagraph 4.2) is carried out, using a skimmer labeled with a nameplate showing a recovery rate of 10m³/h, the amount of oil spread is 20 liters and the amount of oil and water (recovered by the sample skimmer) per 1 minute is about 167 liters. The test time is 20 minutes for this group, so the total recovery amount is 3 330 liters. Even when all the oil spread at the beginning is recovered by this skimmer, the oil recovery rate is as low as 0.6 %, which is extraordinarily low. In general, the oil recovery efficiency is not less than 70 % for mop skimmers or disc skimmers which are relatively low in water collection, and the weir skimmers reach 40 to 50 % of RE. When compared with these results, the value of 0,6 % is considered to be exceptionally low.

By this test method, such a result is feared to underestimate the skimmer in its performance. In the case of a test using a skimmer, the test time would be the result and is not a parameter.

　

In Table 1, the recovery amount obtained at the recovery test carried out for a specified time when the skimmer of the greatest performance among those in each group is put to the test, becomes 8 m³ at the maximum. If it is assumed that the size of the recovery tank which is sufficient to receive and store the same amount is 10 m³, and that the tank form takes a cube, then the length of one side would be 2,15 m and its surface area 4,64 m².

In addition, the amount of the oil spread is 20 liters when a low viscosity oil test is carried out for a skimmer of Group 0 or Group I. When all the spread test oil is collected in the same recovery tank, the oil thickness at the surface is 4,3 mm.

The oil recovery performance varies in accordance with the performance of a skimmer put to the test, so the thickness of the oil recovered into the tank varies within a range of from 0 (minimum) to 4,3 mm (maximum). It is difficult to measure the oil layer by thickness at this test, with satisfactory accuracy. Therefore, it is necessary to consider separately a method of measuring the recovered oil amount.

　

Subparagraph 4.1 contains the statement "as shown in Table 1", so the Table number and title should be given.

The categorization of recovery rate is not made by a scientific method. It should be identified clearly by means of the categorization method as proposed by Japan last year, because the categorization of the recovery rate is a basic parameter in this table.

　

Germany proposed a requirement for a test under calm water only. There is a probability of the skimmer performance being different when measured in the calm water and wavy water.

Therefore, it is proposed that the wave test be added.

　

The last four lines of this subparagraph state the method of testing, so this part should be moved to the beginning of paragraph 5).

　

Two sentences appear in succession at the beginning of the subparagraph having the same contents with subjects of "applicant " and "maker". The latter sentence should be deleted.

　

It states "oil and water temperature have to be +20℃ (± 5 %)". However, this test condition is dependent on the capability of the test facility. For the test facility built outdoors, controlling the required condition is impossible.

It must be ideal to perform the tests always by keeping the test condition at constant parameters and assess the skimmers, but due to the season in which the application is made, there must be some difficulty for some test facilities to attain this condition due to the capability of the test facilities.

From this consideration, it is proposed that oil and water temperatures be measured, that conversion on viscosity of the test oil at the test temperature be made from the "Temperature-Viscosity diagram", and, furthermore, that the report clearly mention this matter.

　

This subparagraph does not specify the "kinds" of test oils, but it is preferable to specify the lubricating oil, which always has stabilized quality and which is easily obtained. Petroleum products, such as heavy oil, will show variation in quality and character depending on the crude oil production site and production time of the year, and since they make adverse impact on test facilities and human health, their application should be avoided.

　

A number and a title should be given to Table 2.

　

The items of measurement are shown. However, in order to clarify the test report better, it is proposed that the following be added to the end of this paragraph.

　

The recovery capacity of a skimmer shall be calculated from the recovered oily-water and test period of time using the following formula.

　

i) Oil Recovery Rate without Emulsion (ORR)

　

ii) Recovery Efficiency without Emulsion (RE)

　

iii) Recovery Rate of Emulsion (RRE)

　

Subparagraph 6) is missing.