Buffer Fluid for -215 F Process (Plan 52 Seal Arrangement)

[rave426]

Hello All,

Does anyone have any success with running a certain type of buffer fluid on a Plan 52 (unpressurized tandem seal) @ -215 F? We are running liquid and liquid lower as of now. Yes I know we should be running a gas seal somewhere....we're working on that.

The process fluid is Methane @ -215F. We are currently using Royal Purple GT22 buffer fluid, but its rating isn’t near what we need. I think that the buffer fluid is sufficient at run time, but the start up is what has me worried.

On start up our seal pot immediately freezes up and after a few mins its calms back down to normal temperature. This is what usually happens, but sometimes the seal pot never thaws out. I think the buffer fluid is freezing around and between the primary seal faces on cool down and causing face gap. This is allows process to leak by into the seal pot or simply damage the faces on startup.

So again...

Does anyone have any success in running a buffer fluid @ -215 F? If so, what type and what brand?

Thanks!

 

[flexibox]

have you thought of using 50% Glycol 50% water mix? Also why dont you electrically heat trace the pot?

 

[JJPellin]

Correct me if I am wrong, but won't 50/50 glycol freeze solid at -215 °F? And, heat tracing the seal pot won't do anything for the barrier fluid within the seal and between the seal faces at start-up. I have never heard of a barrier fluid suitable for this service. I would suggest stepping up the schedule and getting the gas seal installed.

Johnny Pellin

 

[flexibox]

You are correct Johnny, I screwed up on the conversion F to C. I will check what is used in cryogenic services, I am sure that I have done some work on this many years ago!

 

[rave426]

Thanks all!

I'm not sure about that 50/50 mixture, but my initial thought is that it would freeze. I'll look into it. As of now gas seals sound like a must!

 

[rave426]

Does anyone happen to have recommended direction for a fluid?

 

[someguy79]

I assume the process is liquid methane or LNG at pressure above atmospheric. It sounds like you might be getting autorefrigeration (a tiny bit of methane leaking by the seal and driving temperature down locally before startup).

I don't know anything about the Royal Purple product you're using. You should check that your buffer fluid has a cloud point or at least a waxing point below -260°F, or whatever your bubble point temperature is at 0 psig.

Sorry, I don't have the answer on what buffer fluid to use.

 

[justabitconfused]

No recommendation for fluid from me, sorry, but I suggest you look at using a canned motor pump?

 

[QPAini]

Dear rave426,

I have been maintenance plan 52 seal type running for C1 product with themprature about -45 deg C, we are using shelll tellus morlina 10, as long as there are no liquid leakage from your seal i believe your seal will never freeze were freeze indicated liquid passing to atmosphere.

 

[nfinit]

I can't think of a single fluid that will do what you need, not that there isn't one. I would be looking into an immediate replacement with a dry gas seal.

I would also contact your seal vendor for a more detailed approach.