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TitleWall Wash Test
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Page 1

Wall-Wash tests on Chemical Tankers



Wall Wash Test Procedures on Chemical Tankers


Preparation
-Reagent-

 Pure Methanol (500 ml/bottle)
 Pure Water (DI Water)
 2% Silver Nitrate Solution (500 ml / bottle)
 20% Nitric Acid Solution (500 ml / bottle)
 10 ppm (0.01 mg/ml) Chloride Standard Solution (500 ml / bottle)
 0.02% Potassium Permanganate solution (100 mg in 500 ml of DI Water) – to be stored

in a dark bottle in a dark bottle and cool temperature.
 Concentrated Hydrochloric Acid (500 ml / bottle)



-Instrument-

 Funnel x 1
 Plastic Bottles (500 ml x 2 bottles for collecting wall wash samples)
 Nessler Tube (100 ml x 6 nos.)
 Pipette (5 ml x 4 nos. for Nitric Acid / Silver Nitrate/Chloride Solution / KmnO4
 A petridish or Shalle x 2 nos. (for testing Non-volatile matters)
 Disposable Vinyl gloves (200 sheets / case)
 Disposable Shoe covers
 A.P.H.A. Color Standard (No. 3, 5, 8 & 10) for color test.
 Black colored plate (for testing turbidity of Hydrocarbon / Chloride)
 White colored Plate (for testing of turbidity of color)
 Flash Light.



Wall Wash Sample Collection
 Before entering into the tank for sampling, ensure that the tank has dried up completely

and has no humidity on the wall and gas freed.
 Check for toxic gas /combustible gas / oxygen prior entry.
 One man standby – in attendance
 Carry the test kit for WWT in a closed bag or wooden box and keeping in mind not to

drop the same in the tank while going into and coming out of tank.
 Put the shoe covers and wear the vinyl gloves.
 Wash the equipment to be used for WW sample collection by methanol.
 A sample of test methanol is sprayed on the bulkhead and collected in a sample bottle

by using half cut funnel.
 Take sample from four parts of forward / aft / port / Stbd bulkheads and in the area of 1

meter in height x 30 cm in width at the position of 1.5 m from the bottom by methanol
wash on the wall.

Page 2

 The necessary quantity of sample from each tank is about 200 to 250 ml (50 ml for
color, 50 ml for Hydrocarbon, 50 ml for Chlorides & 50 ml for PTT).


Sample Analysis


Colour
This is represented by APHA from 1 to 30 where >APHA5 is the most stringent. The
number is determined in the lab by passing light through the sample. Most ships do not
have this equipment but if you hold the sample against a white sheet of paper and it
appears absolutely colorless you can be quite sure that the number is less than 5. For
this fill up sample about 50 ml and add 50 ml methanol into a 100 ml Nessler Tube.


Suspended matter
Switch of all light and hold torchlight at the bottom of the tube containing the sample.
Any suspended matter will be clearly visible.


Hydrocarbon Test
Hydrocarbons together with water will form a milky solution. To 50 ml of wall wash
methanol add 50 ml of DI water. The mixture is shaken and allowed to stand for 20
minutes. Initially turbidity will appear and the same will reduce in a few seconds.
Compare this to a nessler tube containing 50 ml of pure distilled water and 50 ml of
pure methanol (as a standard solution for comparison) on the black plate or
background. Switch off the lights and using a flashlight shine the beam first from one
side and then from other. Look into the tubes from the top for turbidity. If the sample
appears cloudy or not completely clear then hydrocarbons are too high and the tank
needs to be washed with methanol.
NOTE :- The proportion of methanol to distilled water for testing will depend on the
terminal where the product is to be loaded. Includes, where available, the required wall
wash specifications of terminals. If a terminal's required specification reads
"hydrocarbons pass (10/90)" this means that the surveyor conducting the wall-wash
test will use a mixture of 10ml of methanol to 90ml of distilled water. The responsible
officer conducting the test onboard his vessel may then use the same proportion of
methanol to distilled water, however the proportions of 30/70 will provide a more
accurate picture of the tank wall.


Chloride Test
Normally 10ppm standard chloride solutions are available on board:

 To make a 2 ppm standard solution add the following:
 Pure methanol 50 cc
 10ppm standard chloride solution 8 cc
 Distilled water 38 cc
 20% nitric acid solution 2 cc
 2% silver nitrate solution 2 cc
 To make a 0.5 ppm standard solution add the following:
 Pure methanol 50 cc
 10ppm standard chloride solution 2 cc

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