2 replies to this topic

[senthil13]

Dear All,

 

This is Senthil Kumar. I came across a serious concern on a recent PHA study done for one of our new compressors on site.

 

Service- Hydrogen gas

Inlet- 125 psig

outlet 600 psig

Compressor- 3 stage, Reciprocating type

 

I was not sure about the relief design of this compressor. I raised the question on protection devices for this equipment and found that the suction side of the compressor doesn't have a relief valve .

 

I talked to the Project engineers.  They considered the first stage relief valve (Set 300# sized for blocked outlet case) to take care of the whole suction side.

 

Mechanical Engineers considered that there is no obstruction to this relief valve from the inlet.  I'm still concerned that the check valve in the Suction/Discharge drums (8 Nos.) can stick in closed position to block the whole inlet to the relief and cause serious explosion/damage.

 

What are all your thoughts on this?  Can i consider that nothing can obstruct the flow path to this relief valve? (see the attached drawing for a basic flow scheme)

 

I have no idea how to make sure that the suction/discharge drums will not stick closed.

 

I'm trying to justify to have a relief at the suction line upstream of the suction drum to protect the system in case the discharge relief opens and pressurises the suction.

 

Please help me on this.

 

Thanks !

Attached Files

•  C 301 analysis.xlsx   14.65KB   45 downloads

[fallah]

senthil13,

 

The position of drums and check valves aren't shown in the sketch, Anyway, if the check valve is to be located in relief path toward the PSV wouldn't be accepted at all in safety point of view...

[senthil13]

Thanks a lot for reply, Highly appreciated...

 

 

Regarding the Suction/Discharge Drums- 

 

There are two cylinders associated with the first stage. Each cylinder has two suction valves that are “paired” with two discharge valves. Thus, there are four pathways for the gas that needs to get to PSV Inlet inorder to flow through.

The system differential pressure required to pass this gas flow is too small to detrimentally effect PSV's performance.

 

Both the suction and discharge valves of the drums are designed and constructed in a way that blockage of flow from any one of the eight valves is EXTREMELY unlikely. Furthermore, if the extremely rare event of one valve restricting flow were to occur, there would still be three other open paths to the PSV.

 

These are some of the comments i got from my Mechanical engineer who involved in the construction and design of this compressor.

 

But we are still debating to install relief valve in the inlet of the compressor ( first stage)

 

I will update when we come to a conclusion.

 

Other options thought about are 1. Routing 3rd stage cooler discharge to inlet of the relief valve 2. Route all the PSV to atmosphere

 

thanks in advance for any comments.