3 replies to this topic

[Sharma Varun]

While evaluating a FEED package, I just witnessed this case where gas breakthrough is considered via. bottom pump just like considering bottom control valve failure.

In this case pump is pumping from high pressure vessel to low presure vessel, also pump suction has an SDV linked with level.

The designer has considered rated mass flow through the pump for relief purpose.

I have never seen this case, nor do I remember reading this in any standards say API, SHELL etc.

 

I do not expect comments on wheather what designer has considered is right or wrong?

But I wish to know weather this type of gas blow by is an established practice & if anybody has designed the system for same?

Also does type of pump make any difference?

 

Thanks regards,

Varun

Edited by Sharma Varun, 17 September 2013 - 01:07 AM.

[Propacket]

Pumping from high pressure to low pressure?  

 

Soon we will here that someone in skies is using a missile to come to earth instead of coming down by gravity with a parachute. Ha  

 

May be you are overlooking the scheme. Any PFD / P&ID you can attach?

Edited by Propacket, 18 September 2013 - 07:38 AM.

[curious_cat]

Pumping from high pressure to low pressure?  

 

Soon we will here that someone in skies is using a missile to come to earth instead of coming down by gravity with a parachute. Ha  

 

.......low pressure vessel is placed at a height really, really high up. 

[Sharma Varun]

 

Pumping from high pressure to low pressure?  

 

Soon we will here that someone in skies is using a missile to come to earth instead of coming down by gravity with a parachute. Ha  

 

May be you are overlooking the scheme. Any PFD / P&ID you can attach?

 

 

 

Pumping from high pressure to low pressure?  

 

Soon we will here that someone in skies is using a missile to come to earth instead of coming down by gravity with a parachute. Ha  

 

.......low pressure vessel is placed at a height really, really high up. 

 

Hahaha very well said, its weird but I am sharing what I have witnessed, what more to say, the FEED includes a fire case psv given for a vessel floating with flare (that too with a 10” vent header) and to top of it -vessel is on a grated platform where there is no chance for pool fire & fire case doesn’t apply.

 

To give you one more funny dose, in another FEED that too for a big name & by a big consultant, I have seen a PSV placed on a compressor suction scrubber with PSV datasheet specifying fire case with 0 kg/hr load, and a 2” nozzle in the vessel for the purpose. Reason being the vessel is filled with gas & with selected set pressure vessel wall fails before relieving conditions arrive. Some moron had calculated design pressure as 72 barg (which was not based on settle out also) against an operating pressure of 34 barg & temp. 60 degc.  Thus @ relieving conditions temperature exceeds material failure temp.

 

In one of my very first posts, http://www.cheresources.com/invision/topic/18676-flow-orifice-in-drain-system/ I have discussed about RO for lg/lt drain lines.

 

So ppl in process industry are using their wild imagination particularly when they talk about safety.

 

Now coming back to this scenario, the vessel in question is a waste gas KOD, traces of liquid drains from this are being sent to a downstream drain vessel via. pump, please note its an existing system & I thought   pumping is done after vessel is depressurised. Pump discharge is directed to drain vessel via an elevated header. I admit, I sounded confusing by saying that "pump is pumping from high pressure vessel to low presure vessel", but I got such a shock by the idea that I was eager to discuss. In this case designer has considered gas blow by through pump in spite of an SDV available in pump suction. Now after looking at complete picture, I could conclude that designer was trying to calculate load for sizing drain vessel vent & he considered pump flowrate for the purpose, but in his calculation he has termed this as gas breakthrough via pump . So now the situation is clear to me .

Edited by Sharma Varun, 18 September 2013 - 11:45 PM.