API 682 (3rd edition) mechanical seal temperature limit 1

[nihili]

I have a C2A3A235261 flowserve mechanical seal: Category 2--Arrangement 3--Type A. Do someone know the temperature limit for this kind of seals? I have done some research through the internet and apparently Category 2 can work up to 400 ºC (750 ºF). However when it is type A... the temperature limit can be 250 ºC (480 ºF)

 

[flexibox]

The temperature limit is dependant on the material of the Orings or if it a high temp metal bellows then it will use Graphoil. What is the construction of the seal? different Oring materials are limited to their max temp limit. If you have Graphoil then 400C is OK.

 

[PumpSmart]

nihili,
Depends of materials and design (model).
What model you have? QB, QBQ, BX, BXH, BXRH, etc?
What materilas are components made? o-rings, faces, bellow or spring..

 

[bk19702]

Type A should be a pusher seal with o-rings, which depending on the o-ring material may or may not be good up to 250C. Do you know the o-ring material? The API pipng plan you listed indicates a Plan 23 and 52, with provisions on the gland for a future quench (61). What temperature are you currently operating at? Also, Arrangment 3 should be a pressurized seal; you indicated a Plan 52 in the piping plan which is unpressurized (arrangement 2).

 

[nihili]

I attach a drawing where you can see the materials. Mainly:
316 SS, SIL CAR, C-276, 304 SS... most of them correct for high temp, except for the gaskets which are FFKM... am I right?

The seal is Flowserve QBQ

 

[nihili]

By the way, seal faces are: SIL CAR and Carbon. Is carbon suitable for high temp?

 

[flexibox]

You have FFKM which is a Perluoroelastomer. These Orings can do between 316C & 327C depending on which grade you are using but I see that you have API Plan23 which should cool the primary seal. The reason you have Plan 23 is because you are using a Pusher seal and you are operating at the limits of the Orings. Yes you can use Carbon on high temperature applications but you need to check if what you have is a suitable grade. I assume that you have asked about the temperature limits of the seal because you may be experiencing temperature issues? It would be good if you can explain what the site issues are that prompted you to submit this posting. As the speed is 3200RPM and 80mm shaft, there is a lot of heat generated. Does the Plan 52 Vessel get hot? What is the Buffer Fluid? If you are experiencing problems with gasket item 13 & 13.1 it may be related to heat soak by the Silicon Carbide. As the seal generates heat it is diappated through the silicon seat as Silicon has a High Thermal conductivity. You may also experience some coking on the outboard seal but this depends on the buffer fluid used. I suggest that you provide more details of the problems you have and someone will point you in the right direction. I have used Single seals with N2 quench on these applications successfully.

 

[nihili]

Hi all,


First of all I answer your questions:
1.- We do not have temp measure in Plan 52.
2.- Same as the process fluid: Dowthwrm A.

The fact is that we are observing that the seal faces are degrading themselves very quickly (at least much faster than expected). Some more comments:

1.- It is true that our barrier fluid can degrade to create coke. However, for this, it is needed O2... but our system is blanketed with N2 and inside the seal the pressure is always much higher than the atm... So no O2 inside the seal...

2.- I am trying to investigate the Carbon grade so that to know the suitability as you said in your post.

3.- Independtly of all of this, I have a huge doubt... If my seal is type A and according to API 682, type A is only recommended for temperatures up to 176 ºC... I guess this is the max allowable temperature inside the seal. am I right? I ask this because in the pump suction the nominal temperature is 300 ºC. However, inside the seal we have on average:

- Seal outlet (towards plan 23 cooler): 140. (since august we are observing: 250 ºC)
- Seal inlet 80. (since august we are observing: 150 ºC)

I do not know if the temperature increase is due to that the degraded faces allow higher flow from the pump to the seal and the cooler is not able to cool it down...

Finally, in the documentation I uploaded, the supplier stated the max allowable temp inside the fluid is 327 ºC... This contradicts API 682. Am I right?

Why Type A is not valid for temps over 176 ºC taking into account that al materials are suitable to withstand temp over 176 ºC?

 

[sureshpksk]

Pl check the seal arrangement again. In drawing it is given as C2A2A2353B61.

 

[tesser]

I'm with sureshpksk. The 682 coding on the drawing is C2A2A2353B61 as he says, but the fluid details bit gives 23 & 52.

Arrangement 2 (A2) is a dual unpressurised (tandem)seal. But 53B is for an arrangement 3 (A3) dual pressurised seal with a pressurised barrier fluid, pressurised via a bladder accumulator.

Perhaps I'm missing something

 

[Airsporter1st]

I seem to recall a previous job involving Dowtherm and that oil can degrade to form cokes without the presence of oxygen at a surprisingly low temperature. I would check your datasheets again if I were you.

The material code 5AKX on the drawing tells you that the carbon grade is resin bound.

The title block clearly indicates that this is a non-pressurised seal - as does the terminology "buffer" as opposed to "barrier".

If the faces had degraded to allow higher flow through the inner seal, you should get a high level/high pressure alarm in your Plan 52 system. However this depends on how it is set up - do you have a system drawing?

If there is no indication of increased leakage through the inner seal, I would suspect your cooler is fouled/blocked on the CW side.