Separator Control / Protection

Hello everyone,
 

I would kindly like to ask some questions about three phase separators that I am concerned about.
 
1- I have read in many topics about the unncessecity of an ESD Valve at Gas outlet, why so ?
    if in the case where Gas goes directly to an existing CPF : Do we not actually need ESDV at gas outlet ??

2- In case we have a pump at outlet of condensate, is the ESDV put on outlet of condensate or at inlet of Pump system (considering there is some distance between the pump and the vessel) ? is the choice made based on inventory volume ? 

3- Is the pump controlled by level control or flow control ?

4- Is the level / flow control sufficient for pump protection ? or is a minimum flow for pump needed ? Does the minimum flow go back to the separator ??

5- Is the pump working on ON / OFF (i.e. Pump goes ON after accumulation of condenstae level then goes OFF) OR is the pump constantly pumping and only goes OFF at Low Low level ?

Sorry for asking too many questions, But I am reading so many different answers and cant find the right ones.

Thank you in advance !

 

 

 
1- I have read in many topics about the unncessecity of an ESD Valve at Gas outlet, why so ?
    if in the case where Gas goes directly to an existing CPF : Do we not actually need ESDV at gas outlet ??

2- In case we have a pump at outlet of condensate, is the ESDV put on outlet of condensate or at inlet of Pump system (considering there is some distance between the pump and the vessel) ? is the choice made based on inventory volume ? 

3- Is the pump controlled by level control or flow control ?

4- Is the level / flow control sufficient for pump protection ? or is a minimum flow for pump needed ? Does the minimum flow go back to the separator ??

5- Is the pump working on ON / OFF (i.e. Pump goes ON after accumulation of condenstae level then goes OFF) OR is the pump constantly pumping and only goes OFF at Low Low level ?
 

 

Hi,

 

1-It might not mostly be needed because once the ESDV at the incoming line is closed; the outgoing gas from the gas outlet line will be interrupted, but it should be decided case by case.

2-At the inlet of the pump and as close as possible to the separator to avoid loss of inventory in the case of the pump failure or something like this.

3-Is mostly controlled by level/flow cascade control.

4-Needs minimum flow protection with flow go back to the separator.

5-Depending on the continuity of the incoming flow it could be continuous or intermittent with pump stop at low low level.

 

Fallah,

Thank you so much for your answers, it is clear except for some points :

1 - about SDV at outlet gas is not needed : this separator is part of Early production facility (only vessel separator and pumps) so is fire case not considered in this case ? If it is considered then I think we need SDV at outllet gas in order to blowdown the inventory ?

2- If SDV is at outlet of Condensate, do we need another SDV at inlet of pump (again, there about 100m between the vessel and pump)

5- Why is HH level not needed for pump protection ?

thank you in advance

Fallah,

Thank you so much for your answers, it is clear except for some points :

1 - about SDV at outlet gas is not needed : this separator is part of Early production facility (only vessel separator and pumps) so is fire case not considered in this case ? If it is considered then I think we need SDV at outllet gas in order to blowdown the inventory ?

2- If SDV is at outlet of Condensate, do we need another SDV at inlet of pump (again, there about 100m between the vessel and pump)

5- Why is HH level not needed for pump protection ?

 

1-Yes, by your description appears a SDV is needed along the gas outlet line; but it's not adequate for protection against fire case. In fact if there is no flare network there the outgoing gas should be conducted to safe location or/and a dispersion study should be performed to estimate the gas dispersion behavior...

2-I think no need to another SDV close the pump and the SDV close to the separator, which could remotely be closed in emergency case, is enough to prevent loss of separator inventory...

5- HH level alarm is needed to prevent liquid overflow by shutting down the SDV along the feed line not for pump protection...

 

Fallah,

Thank you so much for your answers, it is clear except for some points :

1 - about SDV at outlet gas is not needed : this separator is part of Early production facility (only vessel separator and pumps) so is fire case not considered in this case ? If it is considered then I think we need SDV at outllet gas in order to blowdown the inventory ?

2- If SDV is at outlet of Condensate, do we need another SDV at inlet of pump (again, there about 100m between the vessel and pump)

5- Why is HH level not needed for pump protection ?

 

 

1-Yes, by your description appears a SDV is needed along the gas outlet line; but it's not adequate for protection against fire case. In fact if there is no flare network there the outgoing gas should be conducted to safe location or/and a dispersion study should be performed to estimate the gas dispersion behavior...

2-I think no need to another SDV close the pump and the SDV close to the separator, which could remotely be closed in emergency case, is enough to prevent loss of separator inventory...

5- HH level alarm is needed to prevent liquid overflow by shutting down the SDV along the feed line not for pump protection...

 

Thank you Mr. Fallah, all is clear.

About point 1: I meant the SDV is there in order to block the gas outlet and then the BDV can blowdown the closed system volume. So I think it should be necessary in order to close the system and vent the volume ?

 

 

About point 1: I meant the SDV is there in order to block the gas outlet and then the BDV can blowdown the closed system volume. So I think it should be necessary in order to close the system and vent the volume ?

 

 

If the outgoing gas was normally conducted to downstream process facilities and there was a closed flare network, your above mentioned emergency isolation and subsequent blowdown by BDV to flare network was definitely logical, but in emergency case of your system you want to block the gas outlet which was conducting the gas to the atmosphere in normal operation and then vent the isolated gas volume to the same destination through a BDV. Could it still be logical?

 

 

About point 1: I meant the SDV is there in order to block the gas outlet and then the BDV can blowdown the closed system volume. So I think it should be necessary in order to close the system and vent the volume ?

 

 

 

If the outgoing gas was normally conducted to downstream process facilities and there was a closed flare network, your above mentioned emergency isolation and subsequent blowdown by BDV to flare network was definitely logical, but in emergency case of your system you want to block the gas outlet which was conducting the gas to the atmosphere in normal operation and then vent the isolated gas volume to the same destination through a BDV. Could it still be logical?

 

Mr. Fallah,

I think I might have misexplained, the gas outlet is defnitely going to downstream facility (even thought it is an EPF, there's a big quantity of Gas and thus can't be flared and must go to downstream facility). And there is a flare line for deppressurisation where a BDV must be put there. So I think we agree on the system's logic.

Thank you very much for your time.

 

 

 

About point 1: I meant the SDV is there in order to block the gas outlet and then the BDV can blowdown the closed system volume. So I think it should be necessary in order to close the system and vent the volume ?

 

 

 

 

Mr. Fallah,

I think I might have misexplained, the gas outlet is defnitely going to downstream facility (even thought it is an EPF, there's a big quantity of Gas and thus can't be flared and must go to downstream facility). And there is a flare line for deppressurisation where a BDV must be put there. So I think we agree on the system's logic.

Thank you very much for your time.

 

Hi,

Yes, if the gas is going to downstream facilities and there is a flare header to receive the isolated gas in emergency case, your system's logic to blow down the isolated gas by a BDV is reasonable...