What seal plan is used for hot service residue pumps

[RE-ENGINEER]

Dears,
we are facing frequent seal failures in our hot service pumps. Their plans are 53B, 21
we observed coking in the barrier fluid so we have replaced it with another oil with higher flash point.
with regards to plan 21, we observed chocking in the lines even when the cooler is isolated.
my questions are bellow,

1-Do I expect the product to be chocked in the stuffing box and on the bellow? I think the liquid is hotter in the stuffing box than in the flush pipe and i don't think this is contributing to the failure?

2- Assuming the stuffing box temp is high since it is in hot standby. can remove plan 21 and only keep 53B with better quality oil?

The flush is used to cool down the seal, = alternative: I will use a heat transfer barrier that will cool down the primery faces. stuffing box will contain hot liquid so it will not be congealed

the products is crude residues with temperature of 350C

I thought of using plan 21M (flush from common discharge) in this case can I introduce the product to the cooler before it goes to the seal?
what are the risks associated with this plan?

Thanks

 

[JJPellin]

For that product, we would never use either a plan 53B or Plan 21. We would normally use an outside flush in our crude units and cokers (Plan 32) or a double seal with outside pressurized barrier if it was under vacuum (Plan 54). We would almost always use a steam quench (Plan 62). We have used Plan 23 with good success in hot gas oil service. But, this is tricky in our cold environment. The gas oil can set up in the cooler lines on the idle pump in winter. I am not familiar with plan 21M. Please describe what you mean. If I was unable to use any of these, I would start with a single seal with a simple discharge flush (Plan 11) and a steam quench (Plan 62).

Johnny Pellin

 

[RE-ENGINEER]

have you ever got the line of plan 23 chocked?
Plan 21M is 32 basically. 21M is taking the flush from the common discharge.

 

[JJPellin]

I do not understand your question. As I noted above, we have had problems with the heavy gas oil setting up in the lines to and from the cooler on a plan 23. In some cases, we have insulated those lines. In one case, we used electric tracing to keep those lines warm on the off-line pump. If you have the equivalent of a Plan 32, why do you need the Plan 53B? I would remove it and run with a single seal with Plan 62 steam quench.

I am not sure if I would agree that a Plan 21M is basically the same as a Plan 32. Our Plan 32 flush comes from downstream after the gas oil has been filtered and cooled. How do you cool the Plan 21M? A water cooler would lime up. An air-fin cooler would generally not provide as much heat removal.

Johnny Pellin