7 replies to this topic

[invssse]

Dear Members,

I have a question on HIPS(high Integrity Protection System) and ESD. 

There is a C3/C4 splitter column of a chemical process unit (which is right now on a basic design phase). A SIL-3 level interlock to trip reboiler steam supply at a PSHH has been considered in SIS design and continued steam supply is the key reason for the overpressure at general power failure scenario. and it's required now to mitigate the relief load for this scenario. 

My question is: Can this interlock as a part of ESD be taken as HIPS if maintenance/test procedures comply with HIPS' requirements? or a HIPS must be a separate interlock and it's required to design/install another interlock to do the same thing as that in ESD? 

 

Thank you!

 

[Bobby Strain]

Maybe you should draw us a picture. I usually provide a set of solenoid valves on an isolation valve, (in addition to the control valve if there is one), air supply that is on the steam supply to the reboiler. This is usually good enough when you wish to mitigate relief sources to reduce the total flare load. The splitter PSV will provide overpressure protection.

 

Bobby

[fallah]

 

My question is: Can this interlock as a part of ESD be taken as HIPS if maintenance/test procedures comply with HIPS' requirements? or a HIPS must be a separate interlock and it's required to design/install another interlock to do the same thing as that in ESD? 

 

 

invssse,

 

With limited info provide:

 

ASME and API 521 have accepted using SIS as an alternative to pressure relieving devices. Relieving pressure devices provide overpressure protection through controlled relieving the inventory while SIS approach concentrates on deletion of overpressure cause itself; then SIS should have high integrity level such that to be considered as High Integrity Pressure Protection System (HIPPS).

 

Then, HIPPS should be a completely independent protection layer having dedicated UPS power, sensors, logic solver and final element. If the interlock you mentioned has such characteristics you can use it as HIPPS, otherwise try to provide one with mentioned specifications... 

[invssse]

Fallah,

 

Thank you for the reply! That's quite clear.

[Bhavinkumar]

@ Fallah

 

Would you please eloborate ....what do you mean by indipendent protection layor in terms of dedicated logic solver. I mean is HIPPS required indipendent controler as hardware. As I know...... normally there is only one controller which is working  and one stand by...... for all control logic or safety logic in one unit. Do you mean that if HIPPS is imlimented, it has dedicated controler for HIPPS action. Please correct me if my understanding for controler is wrong and throw some more light.

[fallah]

Hi,

 

Actually, the HIPPS is designed to measure the pressure using normally three identical, but separately mounted PTs. Each transmitter signal is read by Safety Instrumented System (SIS) tested against set point and majority voted. The SIS is composed of three input channels, three microprocessor/communication channels and three output channels, all fully integrated... 

[Bhavinkumar]

@ fallah

 

I heard this earlier also...... that HIPPS is high SIL level (3 or 4) require as to get more reliability, considering the extent of councequancies. and hence the requriement of independent layor. But I am not sure that controller is also required to be indipendent and dedicated for HIPPS. Is it so?

[fallah]

Hi,

 

Yes, the HIPPS requires independent and dedicated controller...