Mechanical seal for a molten sulphur application. 1

[LightBands]

Hi all,

i am right now working on a mechanical seal for molten sulphur application.

what is the best seal and environment you would recommend?

i am thinking of a rotating metal bellow seal with steam heated seat. Pump has jacketed stuffing box , so steam can be circulated continuously.

Has anyone experienced with pusher seal ? please suggest your views.

Thanks, Ramesh babu

 

[JJPellin]

I work in an oil refinery. We have four sulfur plants with a total of 8 pumps in molten sulfur service. Unfortunately, none of our pumps have mechanical seals. We only use vertical wet-pit pumps (sometimes called vertical volute pumps). These pumps have a separate discharge line cuming up from the impeller in the bottom of the pit, so the collumn is not flooded with sulfur to the top. At the surface, we have grease lubricated packing to contain any vapors. This configuration would be my first choice. If you have no seal, it cannot fail. If you have a horizontal pump or a vertical turbine pump and have no choice but to use a seal, I think you have the right idea. I would use a rotating bellows to take advantage of the self-cleaning feature. I would use a steam jacketed gland and insulate to keep the seal as hot as possible. I would have a particular start-up proceedure that ensured that the seal was fully hot and the sulfur around the seal was liquified before the pump was started. I would use a plan 11 or 13 to carry away the heat from the seal faces. I would use a hard face combination. I am not sure if tungsten carbide or silicon carbide would be better. The toughness of T-C might have advantages in this service. Your seal supplier may have a recommendation and references from other users. This sounds like it could be a tough service. Good luck.

 

[ciddik]

dear Ram babu

using metal below seal is quite good idea, but it will cost 4 times than the other selection. we have provided mechanical seals in sulphur where only the seal faces comming in contact with the media the rest of the seal parts (spring etc.) completely isolated from the pumping media.

these seals are of burgmann HR series double mechanical seals type with steam circulation in stuff box & in the seal chamber externally

sic/sic(IB)/Carbon/TC(OB) will be better, we have experienced good results using this types.

bye

siddik




siddik

 

[longeron]

I'd agree that a metal bellows seal is probably the best choice for most sulfur sump applications. The bellows should be rotating to knife though possible solids, and as mentioned before should be in a jacketed box, or at the very least the gland plate should be both jacketed and have provisons for a steam quench.
I'm not so sure that the cost factor mentioned above applies. I'd suggest contacting your vendor for a better idea.

Sulfur has be be above something like 260 F to stay molten...

There are some pumps like those made by Lewis where the stuffing box will see little to no product during operation. In those kinds of pumps you could also choose to use a kind of restriction device like a pair of segmented bushings purged by plant N2.

 

[Milkboy]

Personally, I'd also go with the Rotating Bellows Design with a Heated Box to keep the Sulfer mobile.

A Burgmann HR can be used as stated in the thread but a double seal is not be required in my opinion.

I'm thinking adding a plan 11/13 may not do much in the way off cooling as the temps will be high thru out the system so you may be able to go dead ended.
Either that or you could remove heat from the box you are trying to put in with the heated box.

Antimony Filled (Carbon for Strength) v SiC Faces.

HTH

-
Milkboy

 

[lgoochy]

Whilst edge welded bellows will handle the temperature, they are quite fragile if the temperature of the sulphur drops. They can be quite prone to fracture especially if you dont look after the heating side of the equipment.
I would recommend a pusher with Tungsten Carbide faces with either an integral heating jacket in the seal gland plate or as part of the pump. Also be careful in getting sulphur too hot as the viscosity inreases and again can lead to problems if you use bellows.

Steam quench is a good idea however you will need a fair amount of superheat to keep it hot (from memory anyway)