'Dms' Type Mechanical Seal

IN MOST CASES PROCESS LIQUIDS AND GASES CONTAINING HAZARDOUS VAPOURS, DANGEROUS CHEMICALS OR INFLAMMABLE PETROLEUM MUST NOT BE ALLOWED TO LEAK INTO THE ATMOSPHERE. IN THESE APLICATIONS A SECOND a CONTAINMENTa 'DMS' Type Mechanical Seal IS PLACED AFTER THE PRIMARY SEAL ALONG THE PUMP SHAFT.THE SPACE BETWEEN THE TWO SEALS IS FILLED WITH A NEUTRAL LIQUID OR GAS CALLED A a BUFFERa OR a BARRIERa FLUID.
IN A TANDEM SEAL, THE SEAL WILL LEAK INTO THE BUFFER FLUID CONTAINED IN THE UNPRESSURIZED CAVITY.IF THE CAVITY REGISTERS A DYNAMIC INCREASE IN PRESSURE, THE OPERATOR WILL KNOW THAT THE PRIMARY SEAL HAS FAILED.IF THE CAVITY IS DRAINED OF LIQUID, THEN THE SECONDARY SEAL HAS FAILED. IN BOTH THE CASES MAINTENANCE WILL NEED TO BE PERFORMED.THIS ARRANGEMENT IS COMMONLY USED WHEN SEALING FLUID THAT WOULD CREATE A HAZARD OR CHANGE STATE WHEN CONTACTING OPEN AIR.

IN A DOUBLE SEAL, THE BARRIER LIQUID IN THE CAVITY BETWEEN THE TWO SEALS IS PRESSURIZED.THUS IF THE PRIMARY SEAL FAILS THE BARRIER FLUID WOULD LEAK INTO THE SYSTEM INSTEAD OF THE DANGEROUS SYSTEM FLUID LEAKS TO THE ATMOSPHERE.THIS IS USUALLY USED IN GAS, UNSTABLE,HIGHLY TOXIC,VISCOUS AND CORROSIVE FLUIDS.

TANDEM AND DOUBLE SEAL NOMENCLATURE IS CHARACTERIZED BY ORIENTATION OF SEAL, i.e TANDEM SEALS ARE MOUNTED FACE TO BACK AND DOUBLE SEALS ARE MOUNTED FACE TO FACE OR BACK TO BACK.