Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

3

Check Valve At The Discharge Of Centrifugal Compressor

check valve at the discharge

6 replies to this topic
Share this topic:
| More

#1 chem55

chem55

    Junior Member

  • Members
  • 19 posts

Posted 15 September 2019 - 06:31 PM

Hello All,

 

In my application as per attached picture, I have one compressor which will not be in use and another compressor which will be working when plant in operation. As per current design, the compressor which will not be used has two check valves at the discharge line of the compressor A, and at the upstream of check valves it has PSV set at 100 psig. Another compressor B will be in operation and when plant will start it will have 600 psig discharge pressure. 

 

As per sketch the compressor A (which will not be in use) doesn't have any block valve at the downstream of check valves.

 

My concern is back flow as my understanding is check valve is not fully leak proofed. As the pressure of orange highlighted line will be 600 psig, the gas will go through the check valve and it will pressurize the line and it will pass through PSV located upstream of check valves.

 

I am thinking to install block valve at the downstream of check valve which will be normally closed. Please advise.

 

 

 

Attached Files


Edited by chem55, 15 September 2019 - 08:06 PM.


#2 breizh

breizh

    Gold Member

  • ChE Plus Subscriber
  • 4,338 posts

Posted 15 September 2019 - 07:33 PM

hi ,

No sketch!

Please remove the 2nd post ( same) .This is creating trouble for followers.

Breizh


Edited by breizh, 15 September 2019 - 07:35 PM.


#3 Chemitofreak

Chemitofreak

    Gold Member

  • Members
  • 156 posts

Posted 16 September 2019 - 01:28 AM

Hi,

 

My two cents.

 

Ideally when an equipment is not in operation or not in use in an operating unit shall be positively isolated. This can be done with valving arrangement, putting spectacle blind, spade etc etc.

 

If your compressor is not in used it is a good idea to positively isolate it.

 

Yes, check valves can leak, there would a flow leakage through the check valves. Since, there are back to back check valve in your system, I think those would be Class I check valves. Class I check valves are regularly/scheduled maintained, if that is the case you can consider 1% leakage flow from the check valve.

 

If those are not class I check valves then there can be full flow through the check valves.

 

Revert in case of any query.

 

Regards,



#4 breizh

breizh

    Gold Member

  • ChE Plus Subscriber
  • 4,338 posts

Posted 17 September 2019 - 01:27 AM

Hi ,

My experience with isolation of compressors has been to install spectacle blind (stand by , maintenance) , it's all depend of the size of the line , the access .

Probably good to talk to the maintenance crew in charge of the operation ( installing and removing blind) .You still have the possibility to call vendor for support.

 

I will not rely on check valves.

You also need to isolate the suction lines(2) and discharge lines(2) the same way to prevent back flow in case of leaks .

 

Your sketch should be reviewed accordingly .

 

 

My 2 cents

Breizh


Edited by breizh, 17 September 2019 - 01:32 AM.


#5 PhilippM

PhilippM

    Gold Member

  • Members
  • 81 posts

Posted 17 September 2019 - 03:41 AM

[...]

it will pressurize the line and it will pass through PSV located upstream of check valves.

[...]

It will not necessarily pass through the PSV, I would probably be more concerned about the backflow/reverse overspeed of compressor A and the overpressure protection of the pieces of equipment upstream of it. The same holds true for compressor B however, even if compressor A is completely isolated with e.g. spectacle blinds, as the compressor might fail (e.g. loss of electrical power), two check valves might not be acceptable as a backflow protection.



#6 chem55

chem55

    Junior Member

  • Members
  • 19 posts

Posted 19 September 2019 - 03:47 PM

Thanks for your expert advise. Yes it is better to positively isolate the compressor. It is better to add the blind flange and a block valve.



#7 Bobby Strain

Bobby Strain

    Gold Member

  • Members
  • 2,772 posts

Posted 19 September 2019 - 07:54 PM

None of this design makes sense to me. Maybe you are not telling us all.

 

Bobby






Similar Topics