9 replies to this topic

[engineer54]

Dear Gentlemen,

 

I'm seeking your excellent experience in this subject, one of the hazop recommendation is generated for provision of interlock for tripping the pump whenever UV is provided in suction line of the pump .

 

My questions here :

 

- Is this provision is advisable ?

- Is there is any international standard like API that recommend such scenario ??

 

Kindly share with me your views & experience.

 

Thanks & Best Regards

[fallah]

engineer54,

 

Appears by "UV" you mean shut down valve. If so, it's not uncommon having interlock for pump trip simultaneous with closing mentioned valve due to, let say, LL level in suction drum. Please upload the sketch of the system to get better reply...

[engineer54]

Dear Mr.fallah,

 

Appreciate your response ,You are correct what we mean by "UV" is ON OR OFF Valve (Fully open or Fully closed only)

 

Actually its simple vessel having downstream line going to the suction of the pump where there is UV in the suction line of the pump, but there is no interlock to trip the pump in case of low level in the suction vessel as you mentioned it may lead to cavitate the pump.

 

Could you please support us if there is any International standard e.g. API Standard recommending this interlock as a protection ?

[engineer54]

In the other hand incase of the "UV" closed during normal operation it will lead to Shutdown the valve and maybe damage for the pump.

 

Is there is any precaution for this regard??

 

Appreciate your cooperation

[fallah]

engineer54,

 

You fail to upload the sketch of the system; then can't present further advise...

 

As far as i know API RP 14C contains some recommended safety devices for various equipment but in the field of offshore production platforms might be applied to other fields; but i think there isn't a general standard to specify the required protection layers in a plant same as you did describe. A proper risk analysis/assesment will dictate the required safety devices and protection layers...

Edited by fallah, 24 February 2015 - 01:18 PM.

[Zauberberg]

The shutdown valve can be equipped with a simple limit switch. Each time when the switch signals "closed" or "error" (anywhere between open and closed position), the interlock can trip the pump. This could be one option.

 

We don't know how critical is this pump, so this might not be so good idea - it all depends in which service is the vessel upstream, and what are the consequences of uncontrolled level rising. As Fallah says, more details about this particular application is needed before we can suggest something better.

[fallah]

In the other hand incase of the "UV" closed during normal operation it will lead to Shutdown the valve and maybe damage for the pump.

 

Is there is any precaution for this regard??

 

 

engineer54,

 

Interesting point...yes there is the possibility of mentioned UV malfunction to close during normal operation leading to pump damage...and again yes...there is protection facility in this regard as follows:

 

"Considering an dedicated interlock to trip the pump on loss of open condition for mentioned suction UV..."
 

[engineer54]

I really appreciate your valuable points & comments , its a healthy discussion .

 

Thanks all of you

[kiansafaie]

You could use UV upstream of pumps this UV will be close with tripping the pump. And for protection of pump use of shutdown action with LL flow after UV is advised this protect the pump from any blockage due to fail of UV.
But as general i didnt see this configuration for pumps, this is seen for compressors not for pumps.

[Babu Prasad]

In hydrocarbon industries, higher capacity pumps equipped with emergency shutdown valves (ESV) on suction lines to prevent toxic liquid hydrocarbon release to atmosphere due to pump seal system fails.  Higher capacity pump obviously need higher capacity suction vessel and large quantity of hydrocarbon can release which is high potential hazard for the human and plant. Therefore these emergency valve will isolate feed to the pump in case of any hydrocarbon leak based on field gas detector activation under cause & effect logic.( pump discharge will be isolated by non return valve) Further on low level of suction drum, ESV will also isolate the pump to prevent cavitation or loss of suction to avoid pump/seal damage. .

 

Due to malfunction of ESV closure, pump will trip automatically either based on ESV close indication or open indication disappears by timer logic. Same way pump will not be allowed to start if it is close signal prevails. By this method pump will be protected to run safe and it will get isolated by ESV in case of any leak by ESD logic... It is common in Natural gas extraction/ NGL fractionation   plants where large quantity of toxic liquid hydrocarbon being handled.