The following occurrences would justify a process shutdown either separate equipment items or a complete system.
1 Change in production requirement involving the removal of an item of equipment or system from the process.
- Control problems on an individual item of equipment.
An automatic process shutdown of an equipment item or system will occur when process upsets or control problems result in an item of equipment operating outside its design operating ranges.
A full matrix of PSD action (manually and automatically initiated) can be refered to P & I Diagrams from the specific operating mannual.
A PSD of the separator initiated on high pressure or high level causes the inlet ESD valve and liquid outlet ESD valve to close. A PSD on low oil and water levels(Test)cause only the liquid outlet valve to close.
Bulk separator PSD can effect the other running facility, a test separator PSD does not affect any other part of the station. All these valves will remain in their PSD position until the operating deviation that caused the PSD is corrected and the re-set is operated.
Separator may be shutdown by operator intervention by means of the control room mounted PSD switch.
ESD comes into effect when any of the incidents shown in the above picture takes place. ESD can be activated manually also. ESD shuts down the complete unit.
Shutting down a vessel or whole plant for a planned maintenance comes under a manual shutdown.
9. Isolation of separators
Following procedure is only an outline. Plant operating manual is to be referred for actual isolation.
Before isolating a separator all coonected sections( production stations, CCR) are to be informed and any rwritten procedure aavilable is to be followed.
- Divert all the wells to other separator.
- Change the gas lift selection(if the well is gas lifted).
- If condensate from compressor knock-out vessels is lined up to the separator then it is to be redirected to another separator.
- Initiate separator shutdown.
- Close separator inlet valves, bypass valve and inlet ESD.
- Close liquid outlet valves.
- Close other inlet lines, if any ( condensate from compressor, etc).
- Close gas outlet valves.
- Install tags ` ISOLATED NOT TO OPERATE , and chains on all block valves on inlet and outlet lines to the separator
- Close relief and safety valves.
- Drain the liquid.
- Depressurise the vessel to flare.
- Purge the separator with Nitrogen. Purging is to be carried out in such a way that nitrogen reaches the all corneres inside the separator. The points toinject Nitroge to and purge outlet from the separator is to be selcted accordingly.
14. Install or reverse the blinds for positive isolation. If installation of spades is difficult in some lines, positive isolation is to be done by dropping spools or block valves.