MECHANICAL SEAL

                            MECHANICAL SEAL 

 

MECHANICAL SEAL

MECHANICAL SEAL

Mechanical seals provide a leak-free operation of a pump.  It is more dependable and efficient than the conventional stuffing box and is suitable for both pressure and vacuum service.  Modern process plants have mechanical seals for most of their pumps. 

 

A mechanical seal consists of a set of two anti-frictional mating rings. One rotates with the shaft while the other is stationary in the gland.  They are held together by compression.Normally the one affixed to the shaft is carbon while the stationary member of most seals is Tungsten carbide. Cast iron and ceramic seats are also used in mechanical seal manufacture instead of Tungsten carbide.  Seal flushing liquid cools, lubricates and cleans the seal unit 

  

Heat from the mating seals can be dissipated by circulating a small volume of the liquid being pumped through the seal.  The liquid from the discharge of the pump enters the seal via the seal-cooling nozzle and flows out of the seal housing to the pump suction. 

 

Seal flushing liquid is cooled externally by means of water or air coolers in the service of hot pumps. Seal liquid, besides cooling, provides lubrication of the mating faces and flushes out any small solid particles that might get lodged between the seat and the carbon. Never run a pump dry mechanical seal fails. Mechanical seals fail if there is no seal flushing liquid. 

 

Before starting up a pump make certain that the seal flush connections are in proper order and lined up.  When the seal flush line is provided directly from the pump discharge (before the discharge valve), there will be no valve on this connection, but restriction orifices may be provided. In some modified systems, the seal flush lines may be taken from different equipment in the system such as a cooler and/or a filter.  In such cases, checking of the seal line- up is very important.