13 replies to this topic

[Ankit_Kumar]

I require advice as I need to evaluate the need of RD or PSV at the outlet line of CW (tube side of) exchanger. After searching out, I came to know there are two basis for CW;

1. Tube Rupture Case

2. Thermal expansion due to blockage in line.

 

1. For tube rupture case, shell side fluid inlet pressure will be higher than the design pressure of CW outlet line. Kindly correct me if I am wrong.

 

2. For thermal expansion, PSV(which is sometimes referred as TSV) can be provided almost on all exchangers. But if you want to know the basis, inlet temperature of shell (hot) fluid should be high enough to bring CW near to its saturation temp which is almost impossible for CW exchangers. Kindly correct me if I am wrong.

 

 

Regards

[Bobby Strain]

1. maybe

2. wrong

 

Bobby

[Ankit_Kumar]

can u tell what is the reason behind your answers? Appreciate if you can provide some data for your justification.

[fallah]

Ankit_Kumar,

 

Please specify design pressure of shell/tube side and furnish a simple sketch of the system you described...

[Ankit_Kumar]

I am evaluating the need of RD or PSV at the outlet line of CW side of exchanger. All heat exchangers are of shell-and-tube type with 1 shell & 2 tube paths. Details of temp/pressure at tube & shell side are below 

 

http://s28.postimg.o...gvf2l/image.jpg

[Ankit_Kumar]

I am still looking for answer. Kindly help

[fallah]

Anit_Kumar,

 

I can't open the link you provided...

[Ankit_Kumar]

Edited by Ankit_Kumar, 26 August 2015 - 01:38 AM.

[Ankit_Kumar]

Kindly provide guidance

[gegio1960]

iIf I understand your data...

- you never need the TSV, unless your water tubes can be blocked-in and are exposed to external heat input (eg sun). That's because your shell side temperatures can't evaporate water in the tube side;

- you should put the PSV for tube rupture in all cases except case 6, since the design pressure of shell side is higher. you can avoid the psv if the CW system is big enough to not get pressurized by the tube rupture event (you have to prove that by calculations). you could also avoid the psv by increasing the design pressure of the tube side up to the same value of the shell side.

other things could be considered... but more details/knowledge of the system would need.

good luck!

Edited by gegio1960, 27 August 2015 - 05:22 AM.

[Ankit_Kumar]

Thanks for ur response. If i am not wrong, the criteria for Tube rupture case is 

"The low pressure side of heat exchangers should be protected from the overpressure caused by the tube rupture, if the test pressure of the low pressure side is lower than the design pressure of the high pressure side."

 

Can u share the caculations tht either cooling water can be pressurized or not? Shell side is mostly amine that can't b allowed to expose in atmposhere. However, can u tell how design pressure of tube side can be increased? Remember these exchangers are already installed.

 

What are the more details required to consider other things?
 

[gegio1960]

ankit,

- you can use that criterion

- if relieved material can't go to atmosphere (thru the cooling tower, for instance) you've to provide the PSV connected to flare

- design pressure can be increased by a mechanical rerating calculation

[Ankit_Kumar]

Thanks Geogio

 

If i use criteria wht i mentioned in my last comment, then PSV is not required on tube rupture base except for 1st and 9th exchanger

 

why? bcz test pressure of tube side is 15(1.5 x design P) which is almost equal or higher than design pressure of shell side.

 

Please correct me i am wrong. 

[gegio1960]

yes, if you mean 7th instead of 9th :-)