7 replies to this topic

[Zaki Arif]

Currently i am studying the possibility to routing the vent gas from sour seal oil trap to the flare. In the Original design, the vent gas is routed to the atmospher. However, by the safety reasons, the vent gas need to be re-routed to the saver area.

 

In normal condition, the pressure in the seal oil trap is 1.5 kg/cm2g, whereas the flare header is 0.2 kg/cm2g. This differential pressure is considered enough as driving force for vent gas to flow from the trap to flare header at normal rate. However, in some case, the flare header pressure could increase to 1.3 kg/cm2g. My question is : What problem that can be happened in seal oil system if the flare header pressure significantly increase? Is there any possibility seal oil ingress to process side of compressor? Do I need to do something with the restriction orifice on the seal oil trap vent? like resize the hole size of the restriction orifice?

 

Hope someone has experience with my problem above.

 

Thank you 

Edited by Zaki Arif, 29 July 2015 - 09:35 PM.

[shan]

A check valve may prevent the possible reversed flow not an orifice.

[fallah]

Zaki Arif,

 

Please provide a simple sketch of the system...

[Zaki Arif]

Zaki Arif,

 

Please provide a simple sketch of the system...

 

 Please find enclosed the simple sketch of the seal oil trap system

 

 Figure-1 Compressor Oil System.jpg   30.8KB   2 downloads

[Zaki Arif]

A check valve may prevent the possible reversed flow not an orifice.

 

Dear Shan,

 

Thank you for your answer. Yes agree with you, additional of check valve will prevent the possibility of backflow. However, my point is, when the flare header pressure increase, but still below the seal oil trap pressure, it will just cause lower flow of vent gas from seal oil trap compare to the normal condition due to lower pressure drop. What will happened in the seal system if there is some restriction in the vent line which then cause lower vent rate?

 

Thank you

[fallah]

Zaki Arif,

 

In the case the flare header pressure increases to 1.3 kg/cm2g, regardless of being restriction orifice and check vale or not being, the pressure would build up in the seal oil system. You can calculate the amount of build up pressure in mentioned case and consider the higher pressure limitation of seal oil system; then if the pressure of seal oil system after pressure build up would be higher than pre-specified limitation, seal oil ingress to process side of compressor might be possible...

[Zaki Arif]

Zaki Arif,

 

In the case the flare header pressure increases to 1.3 kg/cm2g, regardless of being restriction orifice and check vale or not being, the pressure would build up in the seal oil system. You can calculate the amount of build up pressure in mentioned case and consider the higher pressure limitation of seal oil system; then if the pressure of seal oil system after pressure build up would be higher than pre-specified limitation, seal oil ingress to process side of compressor might be possible...

 

Dear Fallah,

 

Thanks for your advice. However, could you explain more about the maximum limitation of seal oil system pressure? Is this number directly correlated with the possibility of oil ingress? where this number tipically could be found, because i didn't find this kind of number in compressor operating manual book.

 

Thanks.

[fallah]

 

 However, could you explain more about the maximum limitation of seal oil system pressure? Is this number directly correlated with the possibility of oil ingress? where this number tipically could be found, because i didn't find this kind of number in compressor operating manual book.

 

 

Zaki Arif,

 

The seal oil system normally supplies oil at a slightly higher pressure than the compressor's internal gas pressure as reference gas pressure. If no pressure limitation found in compressor manual, it might the seal oil system equipped with high pressure protection prevents relevant loop to be over pressurized. Relevant vendor would be best reference to provide the answer to this matter...