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Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

(OP)
Hi guys,

When the process fluid is specified as TOXIC in the data sheet, it is required to use Dual Mechanical Seals? Could you explain the degree of toxicity of the process fluid for it to require dual seals rather than just a single seal.

Currently I am working on data sheets where it currently specified Single cartridge Mechanical seal but the process fluid is also specified as toxic.

Thanks!

Regards,
Virata

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

not being a mech seal expert, actually knowing very little about applications outside of pumping water - for toxic I would go with double mech. seal with barrier fluid between.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

Automotive antifreeze is toxic. Methanol is toxic. In high concentrations, Vitamin D is toxic. Just saying that the fluid is toxic is not sufficient to understand the risk of a release. Knowing only that a datasheet lists the fluid as toxic is not enough for me to make a recommendation for the seal configuration.

Johnny Pellin

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

Would a mag drive pump be acceptable for this service?

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

Toxic is not the same as "lethal" in B 31.3 and as said, doesn't give you much to go on.

you really need to talk with someone from Tech safety to establish what is required.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

API seal flush plans you can select from are plans 52A and B, and plan 53. Also note that driver speed turndown range, volatility and viscosity range of the process fluid have some bearing on the plan selected. Talk to the rotating machinery specialists and process safety engineers in you company to see which ones are suitable. A generic solution to a particular service application subset would be ideal, but not always possible.

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

(OP)
Thanks guys. I will coordinate with tech people and see what I can do.

RVAmeche - We currently looking at API 610 pumps only.

RE: Pump Mechanical Seal: Single Seal vs Double Seal for Toxic Process Fluid

Many specifications within companies will drive a toxicity rating that will lead the required specification of the machinery, seals and protective systems.

Magnetically driven seal less pumps, or Magdrive pumps are often an excellent choice for toxic fluid, and offer a sizable benefit on through life costs in application.

If the fluid is below 200cP, less than 260C and with a solids content below 2-5% by weight and 150micron particle size then a magnetically driven centrifugal pump should be considered.

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