Q & A > Question Details
We have a problem at our CDU. It is observed that when we examine salt content at the start of crude charging tank after giving it 24 hour settling time, salts are in yhe range of 2 to 5 PTB. But when same tank is charged and sample is taken at CDU upstream, salt content is higher... Up to 50bPTB... What could be possible reasons?
17/07/2019 A: Joel Kaye, Retired from UOP & Tesoro, kaye13@gmail.com
A likely scenario is that you have water pockets in the tank bottoms that are not being drawn out from the sump or showing up in your tank samples. This can happen when you have solids build up on the tank bottoms. The briny water then gets drawn out in the turbulance when the take is being fed.
03/07/2019 A: Muhammad Faisal, Oman Oil Refineries & Petroleum Industry (Orpic)-Oman, engr.faisalfraz@gmail.com
1. sampling to be reviewed. (top, mid and bottom sample to be taken representative) and analyze for salt, BSW.

2. water draining is important. focus more and ensure draining from all side of draining sump (not from one side).

3. tank stratification issue to be check-mixer problem.
28/05/2019 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
There are many possibilities; 1) Error in sampling/ testing, 2) layering in tank due to sludge, 3) Timing of sampling vis a vis Tank mixer operation, 4) migration from other tank .
25/05/2019 A: MUKTESH KULKARNI, TOYO ENGG INDIA LTD, kulkarni.muktesh@gmail.com
You may check the salt content of slop line feeding to CDU among other possibilities such as flow reversal from any of the connected lines.
25/05/2019 A: Ingemar Quintero, PETROSINOVENSA, idavidqs@gmail.com
What do you mean bu CDU Upstream??? Where are you taking these samples? Please, be more specific.
Salt content in crude oil is directly proportional to the water content. If the water content is high, it is probably that you salt content will be also high (depending on the type of crude, etc). These salts are dissolved in the aqueous phase of the emulsion.
25/05/2019 A: keith bowers, B and B Consulting, kebowers47@gmail.com
The most likely cause for different salt content test results is stratification in the tank (inadequate settling time, not enough mixing in the tank.) This results in non-representative spot samples. The 'draw' connection to the charge tank is probably near the bottom, where heavier (higher salt content) crude will be if the tank is not well mixed. Taking a good, representative sample of a tank with poor mixing is not possible. Sample taking technique IS IMPORTANT.
A 'corked', weighted bottle positively dropped to the bottom, cork pulled out, bottle pulled up at a UNIFORM speed that results in sample bottle only PARTIALLY full upon reaching the top.
24/05/2019 A: James Chacko, Suez Water Technologies & Solutions, james.chacko@suez.com
Tank Draining and or the heel quantity sludge could be the most probable reasons