Molten sulphur pump

[sinectica]

Hello guys,
which is the best API plan for a mechanical seal of a overhung single stage centrifugal pump which works with molten sulphur?
We are not sure of which is the best plan to use with a single mechanical seal.
If anybody has experience in sealing this product I would be very grateful of receiving some help about this issue.

Thank you so much,
Marc

 

[longeron]

A Plan 02/62 is your best bet. Make sure that you have steam traced the piping to and from the pump and a steam jacket for the pump itself.

Plan 02- for the seal chamber/seal. Your seal mfg should be able to design a seal with a jacketed gland plate- a gland plate with an annulus for steam and connectons in and out.

Plan 62- steam on the atmospheric side of the seal

Remember that you have to keep the sulfur within a certain temperature range to keep it in a liquid state. If I remember correctly, 275F is the lower limit.

A single rotating metal bellows seal is a good choice. This is a very difficult application.

I've heard of some Lewis pumps with a pair of bushings and a Nitrogen buffer- but I'm not convinced it works. Give them a call to see what they think.

 

[JJPellin]

We have about 10 pumps in molten sulfur service. But only two of them are single stage overhung pumps with mechanical seals. Those pumps were originally built with single spring pusher seals with Viton U-cups as the dynamic elastomer. A few years ago, they were converted to low temperature rotating metal bellows seals with Viton o-rings. All of the seal glands have steam jackets as longeron suggests. There is no steam quench on our seals and they tend to run quite well. We use 50 psi saturated steam on the jackets to try and keep the seals just above 275 °F as longeron suggests. All of the rest of our sulfur pumps are vertical volute pump with no seals. These pumps have grease lubricated packing at the top of the line shaft to keep the vapors in. But there is no need for a liquid seal. An product that comes up the column to lubricate the line shaft bushing runs out through slots and right back into the pit.

Johnny Pellin

 

[sinectica]

Thank you for your replies, I am discussing the issue with the seal manufacturer and his opinion is to install a plan 01/62, as he says that plan 02 is not good to vent the stuffing box.
We are still on it, if I could grasp more information I would let you know.

Thank you so much for your kind help!
Marc

 

[JJPellin]

Coincidentally, one of our only two sealed sulfur pumps was in the shop this week. The seal had lasted for over 4 years. But, there was a ball of solidified sulfur from the seal gland to the bearing housing. It didn't come our for a seal leak, but for a bearing failure. We don't reseal these pumps very often, but I am told that they tend to seep a little bit of sulfur almost continuously. Perhaps a steam quench would be a good idea after all. If you are concerned about venting the seal chamber, we drill a small hole at the top of the stuffing box that breaks through just inside the head wear ring. This way, the seal chamber tends to vent liquid full as soon as it is flooded, even with no flush flow.

Johnny Pellin