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I work in CDU with a capacity of 70000 barrels \ day I have a problem. when we introduced desalter to work, the amount of feed unit quantity decrease to 85%, especially when the introduction of washing water to work by 17000 kg \ hour DIFFERENTIAL PRESSURE on the mixing valve set to 0.35 kg \ cm2,desalter pressure is 11 kg \ cm 2 When trying to increase the unit capacity, the desalter press. Increased and send a signl to the pressure valve that is installed on the charge pump discharge to derease it’s open to reduce the increasing pressure.

Additional information:
Crude oil is taken by gravitation flow from storage tanks. The crude oil is fed pump P01 to the first part of one route heat exchanging system, where is preheated in the train of exchangers E01, 02, 03, 04 and 05 to temperature 125-130 °C. The crude oil with this temperature enters the single stage electrostatical desalting. Desalting process operates with pressure 10-12 kg/cm2g and Desalted crude is fed by means of pumps P02 to the second part of one route heat exchanging system (exchangers E06, E07, E08, E09, E10), where is heated to temperature 244-252 °C. Crude oil is dividing into four equal streams. Each of the four streams is controlled by a flow controller and enters the convection section of heater H01. In the heater (convection and radiation section) it is finally heated to temperature 342-348 °C
28/07/2010 A: Satyalal Chakravorty, Sr Consultant, satya1354@yahoo.co.in
Either or combination of following is happening:
1) The P02 capacity/head limiting
2) There is blockage at D/S section of desalter
3) Higher Press drop in post desalter Heat exchangers
Carry out pressure survery to pinpoint the concern
20/07/2010 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It appears that it is pump P02 that is at capacity. In addition to checking the pressure profile and control valve % open as suggested, try running both the regular pump and the spare pump at the same time. If the unit operates smoothly with both pumps running, and you have found no restrictions from your pressure survey, pumps P02 are too small. A larger impeller may be possible with the existing driver. If the driver is too small for a larger impeller, but was specified for end-of-curve protection, it may work fine without end-of-curve protection at the higher pumping rate.
19/07/2010 A: Jayaraj Jayam, Chennai Petroleum Corporation Limited, njayaraj@gmail.com
For the said unit capacity the desalting water flow admitted by you is normal or little less than normal. I assume that you are facing the problem only now, that is I don't doubt the design flow handling capacity of your desalter vessel.
Before start to trouble shoot, check the actual valve opening of your desalter mix valve. I also assume that your desalter outlet is immediately going to a booster pump to send flow through pre heat train and furnace. In that case, you check for your booster pump discharge valve opening, open the valve fully. Check the preheat train exchangers crude side valves. If you find any valve in pinched condition open it fully. Check your furnace pass flow control valves opening. Check for matching the valve opening with panel indication. If the valves are fully opened, conduct a pressure survey of your preheat exchangers. If delta pressure is high across any exchanger open the bypass valve of the exchanger. Check the pressure drop across your furnace and compare the value with the period at which you didn't experience such problem. Observe the skin temperature of your furnace tubes also. If the indications are high, think of going for a decoking. Before doing all these exercises, don't forget to check the strainers of your booster pumps and its discharge pressure. Hope I am to the point only.
19/07/2010 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
It appears that one of the pumps is at capacity. Which pump controls the desalter pressure? Which pump flow controls the crude rate?