Page 201 - Petroleum and Gas Field Processing

Table 4 Average Desalting Conditions

Crude gravity Desalting temperature Minimum water ratio

( API) ( C) (vol%)

> 40 110 2–4
30–40 110 4–8
120 4–7
< 30 130 8–10
140 >10

Table 5 Problems, Causes, and Solutions

Problems Causes Solutions
1. A high salt content (a) Feed salt content high (a) Increase the wash
in the desalted (b) Wash water injection water rate
crude oil low (b) Reduce the crude
(c) Crude oil flow rate oil flow rate
exceeds the design (c) Increase the mix value
flow rate pressure drop
(d) Insufficient mixing of
the crude oil and
wash water
2. Oil in the desalter (a) ‘‘Interface’’ level (a) Increase the interface
effluent water too low level
(b) Wide emulsion band at (b) Inject a chemical or
the ‘‘interface’’ dump the emulsion
(c) Excessive crude oil wash (c) Reduce the mix valve
water mixing pressure drop
(d) Poor wash water quality (d) Check for any waste
(e) Crude temperature in the wash water
too low source
3. High water carry (a) Wash water flow (a) Reduce the wash water
over in desalted rate too high flow rate and commence
crude oil (b) Excessive formation or increase chemical
water in the crude oil injection
(c) Interface level too high (b) Reduce the interface
(d) Disturbance in the level and check the
desalter vessel effluent water valve
(c) Check for an excessive
cause and allow the unit
to settle down

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