Selection of seal plan

[Mitesh87]

Hello,

While selection of seal, if my process fluid is toxic and i want that fluid shall not come out to atmosphere. so whether i should go for 3CW-FB or 3CW-BB ?

Normally i have seen 3CW-FB because in this case in board sealing by primary plan 11 or 21 and out-board sealing by 53B. and if i go for 3CW-BB in that case both the sealing(inboard and outboard) by 53 B only.

So when and where i should go for primary plan 11,21+53B and when i should go for 53B (back to back)?

Regards,
Mitesh.

 

[Chpal1984]

Hi Mitesh,

With a plan 53B system the seal is running on the barrier fluid, so you don't have to use re-circulation plan. Now there are alot of good reasons you might prefer to have circulation in the seal chamber, for example if you process is very hot a plan 21 could help extend seal life. Regarding BB or FB, I think its personal preference, FB can be easier to clean and less likely to get clogged with particles in the fluid. API 682 offers a seal selection process, which I would advise looking at. However even they leave the final decisions down to the user, as it does vary with the process fluid.

 

[Mitesh87]

Hello Chpal1984,

Thank you for your reply. Sorry but I can not understand much with this. What i understand is if my process fluid temp is very high and if i go with plan 21 & 53B means FB than i get extend seal life.

As per my knowledge if my temp is very high i can not cool because if i use plan 21 than cooler size will be high. so yes if my temp is high and plan 21 have limitation than i can go for Plan53B BB arrangement.

I want to know that if i use 53 B in BB all the time than is it ok. ? Why and when should i go for FB means 11 ,53B or 21 , 53B?

Regards,
Mitesh

 

[georgeverghese]

Go for plan 53B for both primary and sec seals - hot resid is not a good lubricant and may be fouling also; when it is cooled down, it may be too viscous. Cooling may also be a problem with all sorts of waxy and polymerising components fouling up the cooling HX surfaces.