Ladies and Gentlemen,
Any advice on this querie would be most welcome. Let me set the scene.
3 x 33 WI (Water Injection) Pumps in parallel with each other, 330m3/hr, discharge pressure 330 bar.
Each Pump has an overboard dump line consisting of a HCV choke valve and Emergency trunion mounted ball valve. (It is meant to open in 2 seconds). In this order.
Each discharge line has a WI isolation valve(Slow closing trunion mounted ball valve).
On the combined header prior to going to subsea choke, there is a PCV valve which has been designed around a 2.5 bar dp.
Now let me describe the problem.
The PCV valve was having to burn 30-60 bar so was cranked down to 13% closed to handle 660m3hr.
An operator inadvertently closed the PCV valve by accident. The Overboard dump valve did not react quickly enough and the Seals of the pumps were damaged. Pumps were down along time.
The overboard dump valves are tripped to open on low low flow (113m/hr).They had about 0.5s to react prior to the seals being damaged.
Operators have asked for a FCV valve on the overboard dump line to replace the hand operated choke valve.
Now my diagnosis:
1. Change the LL trip to a PAH trip on the discharge line.
2. Potentially change the HCV to a FCV. This will be expensive. It is in stagnant sea water service and a high dp application
3. Replace the PCV valve downstream and design it correctly.
4. Select the correct valve for the emergency opening function on the overboard dump line.
Options that have been deemed not to be appropriate are:
1. Restriction Orifice on recirculation line - 3 x 300%. All water needs to be injected.
2. PSVs on the discharge line. Deemed to be expensive solution.
Ideas investigated/investigating are:
1. Actuators on ESD valves on overboard line have been confirmed as fit for purpose.
2. Piping is CS and fit for purpose.
3. Replacing PCV valve with correctly designed valve fit for the dp. (This valve will be designed never to close its last stroke more than 25 seconds no matter how closed it is.
4. Investigating a combined FCV / ESD angle valve instead of the HCV. This will have two separate quick air exhaust valves and associated piping.
Now my questions to you...
Do you have any recommendations for valve piping configurations for water injection systems beyond what I have described above?
Any comments on any of the information above? Any suggestions.
Any comment on a combined FCV / ESD valve function with two different air supplies and soleniod functions?
Any comment on the placement of a bursting disk dump to overboard with a restriction orifice?
Regards,
Alex Chatwin
Any advice on this querie would be most welcome. Let me set the scene.
3 x 33 WI (Water Injection) Pumps in parallel with each other, 330m3/hr, discharge pressure 330 bar.
Each Pump has an overboard dump line consisting of a HCV choke valve and Emergency trunion mounted ball valve. (It is meant to open in 2 seconds). In this order.
Each discharge line has a WI isolation valve(Slow closing trunion mounted ball valve).
On the combined header prior to going to subsea choke, there is a PCV valve which has been designed around a 2.5 bar dp.
Now let me describe the problem.
The PCV valve was having to burn 30-60 bar so was cranked down to 13% closed to handle 660m3hr.
An operator inadvertently closed the PCV valve by accident. The Overboard dump valve did not react quickly enough and the Seals of the pumps were damaged. Pumps were down along time.
The overboard dump valves are tripped to open on low low flow (113m/hr).They had about 0.5s to react prior to the seals being damaged.
Operators have asked for a FCV valve on the overboard dump line to replace the hand operated choke valve.
Now my diagnosis:
1. Change the LL trip to a PAH trip on the discharge line.
2. Potentially change the HCV to a FCV. This will be expensive. It is in stagnant sea water service and a high dp application
3. Replace the PCV valve downstream and design it correctly.
4. Select the correct valve for the emergency opening function on the overboard dump line.
Options that have been deemed not to be appropriate are:
1. Restriction Orifice on recirculation line - 3 x 300%. All water needs to be injected.
2. PSVs on the discharge line. Deemed to be expensive solution.
Ideas investigated/investigating are:
1. Actuators on ESD valves on overboard line have been confirmed as fit for purpose.
2. Piping is CS and fit for purpose.
3. Replacing PCV valve with correctly designed valve fit for the dp. (This valve will be designed never to close its last stroke more than 25 seconds no matter how closed it is.
4. Investigating a combined FCV / ESD angle valve instead of the HCV. This will have two separate quick air exhaust valves and associated piping.
Now my questions to you...
Do you have any recommendations for valve piping configurations for water injection systems beyond what I have described above?
Any comments on any of the information above? Any suggestions.
Any comment on a combined FCV / ESD valve function with two different air supplies and soleniod functions?
Any comment on the placement of a bursting disk dump to overboard with a restriction orifice?
Regards,
Alex Chatwin
