A gas seal (non-contacting) is a type of double mechanical seal with two primary seals which has a gaseous phase fluid as the barrier fluid and in which the barrier fluid acts to separate the seal faces during operation of the equipment. The barrier fluid is a gas, there are designs for steam seals which also operate on this principle. In a gas lift-off seal the faces are not in contact while the machine is running, resulting in little to no wear of the faces. They are separated by a thin gas film (flow). The proper equipment and correct operation of these seals and the equipment is necessary for good seal life.
Some factors to take into consideration when using a gas seal (non-contacting) to pump liquids are;
-Barrier fluid is a gas
-Gas Usage rates are higher than contacting (issue for hard vacuum)
-Strict run-out tolerances – suitable for your machine?
-Fast rotation machinery (pumps, blowers, compressors) seals operate on hydrodynamic lift
-Slow rotation machines (mixers) operate on hydrostatic lift.
-No contact between faces, no wear during normal running
-Atex limits are much higher
-General speed limits are much higher
-Failure mode is generally catastrophic for inboard seal, quick shut off required.
-Beware of powders on mixer applications.
-Very good with solids, difficult-to-seal liquids & all gases.
-Highest temperature and pressure running limits
-Can be SIP’d but MUST be dried in place.
What is a dry gas seal?
A dry gas seal, is a subset of the family of gas non-contacting seals, a scion, if you will.
The term “Dry gas” refers to the conditioning (drying) of the gas to prevent all sorts of issues with vapour in the gas which effect seal operation and life. These refer specifically to high speed rotating equipment (turbomachinery). These seals have to cope with high pressures and face speeds.
Dry gas seals are gas lift-off or non-contacting double seals i.e. during operation the seal face pairs do not contact each other, leading to minimal wear (there may be some contact at start-up) and allowing the high speeds required (no heat build-up due to contact friction).
Flexachem offer a full range of Flowserve gas seal (non-contacting)/ gas lift off seals.
If you have any query around how to install a gas lift off mechanical seal for pumps or have some concerns around the seal failures, why not contact one of our mechanical seal specialists below to discuss it in more detail and find out how we can help solve your issues and get your process back up and running reliably again.
Contact our Mechanical Seal Team:
Chris Sheeran (External) – mob: 087 755 9936
Dave O’Connell – tel: 021 461 7233
Fiona Foley (Service Support) – tel: 021 4617240
Tel: 021 461 7200