What is the difference between “flushing” and “quenching” i terms of a pump’s mechanical seal?

Posted by 6 January, 2011

Question by Sid: What is the difference between “flushing” and “quenching” i terms of a pump’s mechanical seal?
Are these two terms same????

Best answer:

Answer by alpha b
*No, “flushing” and “quenching” are not the same.

*Flushing – liquid is circulated through the stuffing box to carry heat away and prevent temperature rise and possible liquids flashing at seal faces.Flushing also prevents solids from settling out of suspension and prevents solidification in the box of liquids that might crystallize with a slight change in pumping temperatures.The flushing liquid may be the product pumped or a solvent liquid from an independent source.

*Quenching – utilized to cool the outside seal or remove any leakage that may crystallize on the faces when in contact with the air.On vacuum service, the quenching liquid acts as a lubricant and seal between the mated faces.If it were not used, air would be pulled across the faces with the result that they would run dry and fail.

*FLUSHING :
To introduce clean liquid into the stuffing box, to remove solids or any problem fluid.
Cool a hot liquid by flushing in a cold one.
Remove a liquid that is sensitive to changes in either temperature and/ or pressure.
You can use this connection to cross connect the stuffing boxes in a double ended pump application, and thereby equalize the pressures in the stuffing boxes.

*QUENCHING OR VENT & DRAIN – plus the disaster bushing:

The disaster bushing will protect the seal from hitting the inside of the stuffing box if you have a bearing failure. This is a very important feature in those applications where the product will burn or explode if overheated.
The disaster bushing will protect personnel if there is a massive seal failure. The majority of the leakage can be directed, down the drain connection, to a collecting tank or vent.
To wash away solids from the outboard side of the seal that will prevent “hang up” as the seal face wears and the seal moves forward.
To wash away toxic or corrosive vapors that might leak across the seal faces.
To control the temperature in the seal area.
As a back up to a heating/ cooling jacketing failure.

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