Chemical Tankers / Day 3 / Day 3 Topic 4 Wall-Wash & Analysis

Permanganate Fade Time:

The permanganate solution must be “fresh”, it is light sensitive, should be stored in an amber (brown) bottle, in a cool, dark place.

Permanganate crystals are supplied with the standard test kit, a solution is prepared by adding 0.1 gram of potassium permanganate to 0.5 litres of distilled water. The amount of water and crystals can be doubled if a large amount of solution is required for extensive testing during the three day period.

Permanganate Fade Time:

Before adding the permanganate solution, fill the tube to the 50 ML. Level with wall wash and place it in a water bath which is maintained at 15C (+ or – 1C) for ten minutes. Then add 2ML. of solution to each tube, stopper and invert “once” to mix, noting the exact time. The tubes containing wall wash to which the 2 ML. of permanganate solution is added should have their stoppers rinsed with methanol before inverting to mix the solution. A dirty stopper could affect the time test.

Permanganate Fade Time:

Place the tubes in the tubes in the bath in a dark place which is being maintained at 15C. Check the intensity of the pink color at 10 minute intervals. Record the minutes elapsed between the time the permanganate solution was added and the time the pink color matches the standard “end color”. That is the fade time and must be compared with the charterers requirements. Note that a thermostatically controlled “cool boxes” may be better for controlling temperature and excluding light during this test with a second box to pre-cool samples and store permanganate samples.

Permanganate Fade Time:

It is helpful to also test a standard sample solution at the same time. Use 50 ML. Of pure lab methanol and 2 ML. of permanganate solution, run test simultaneously with tank sample tubes. If standard fails in less time than you are testing for, it is an indication of a problem with either the lab methanol, the permanganate solution or dirty test tubes/stoppers. Under the very purest conditions, the standard sample will run on test for 120 minutes.

Permanganate Fade Time:

Permanganate Fade Time:

Permanganate Fade Time:

Permanganate Fade Time:

Wall Wash Techniques and Sample Analysis

Appearance:

Carefully examine the wall-wash sample against a good light. Ensure the outside of the bottle is clean. Check for matter, both suspended and settled, in the sample. Check also for general clarity, comparing to a sample of “good” Methanol

Wall Wash Techniques and Sample Analysis

Colour:

At the same time, compare the wall-wash sample and the good Methanol against a white background for any difference in color. You may also have an ASTM color standard chart to assist in quantifying the degree of color