Control Improvement on Centrifugal Pump System
Exploration business is still facing challenges on its facility operations. There are many gaps of reliability improvement that will take big attention to be handled in order to reduce Loss Production opportunity (LPO) because of unreliable operation system. Casing Vapor Collection (CVC) Station is one of facility in exploration business that has function to condense vapors from casing line header which is separated inside CVC separator, after which the condensate is pumped to a production line heading to Crude Oil Gathering Stations. The sketch below is showing the produced fluid flow process in onshore oil field.
The transfer pumps are critical equipment on produced fluid flow process, because if the unplanned down is happening on transfer pumps, there will no fluid is able to be delivered to gathering station and requires the CVC station shut down. So that the availability of these pumps have to be monitored and take big attention on its daily performance in order to extend Mean Time Between Failure (MTBF).
Once upon a time, there was a transfer pump repetitive faliure problem in surge vessel system. The current configuration of this system is shown below;
Transfer pumps have experienced an unacceptable number of repetitive mechanical seal failures which often have resulted in oil spills. The investigation has been conducted in order to find out the bottom causes of this problem. One clearly identified cause is repeated start/stop pump frequently within 10 minutes has caused damage on mechanical seal. The frequent start/stop pump condition is caused by level system itself which is to set lead pump “OFF” at 20% and restart at 40%. This happened on lag pump as well, which requires lag pump automatically “ON” at 60% and “OFF” at 40% liquid level.
The level control loop does not work as well as the level control signal which is routed to recycle valve (LCV 09001) in maintaining liquid level but it almost no effect on level. The current system attempts to control level by interaction between the recycle valve control (“level”) and the product valve control (“pressure”). The interaction is too slow to be effective in controlling the vessel level, so the back up control (pump’s safety device) of auto-starting/stopping pumps is used.
In order to eliminate this repetitive mechnical seal failures and reduce misting by providing reliable system which will control the level appropriately as dedicated. The current control scheme will be changed with control type as mentioned below;
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Label: Chemical Engineering
