How to Choose the Best Barrier Fluid for Dual Seals?

A double mechanical seal has a cavity between the inner and outer faces where the liquid resides. In its unpressurized form, this liquid acts as a buffer between the contents pumped by the equipment and the outer environment, whereas the pressurized form creates a barrier between the two.

Here’s what to consider when selecting a barrier fluid for your mechanical seal.


There must at least be one thin layer of fluid between the moving seal faces at all times to minimize fretting, which can only happen if said fluid can withstand the level of pressure and temperature inside a pump during start-up and standby.

In cold weather states, standby temperatures can affect the viscosity of a liquid, causing it to coagulate to the point where a sufficient amount is not dispatched during operation, causing premature system breakdown.

Heat Resistance

If a barrier fluid is liquid, it’s bound to change under operating conditions. It’s the same case of a state of matter going either way. In colder environs, the liquid might grow viscous whereas, in hotter climes, it may easily be turned to steam, eroding the mechanical seals and causing leakage.

However, a user can select a barrier fluid by finding out how it would react to different extremes. For instance, they might want to examine the state of a liquid during standby while it’s undergoing a seal repair and when it’s operating to predict when the pump may run out of it and top it off at the right time.



Barrier fluid is not safe to use because it works for a mechanical seal application. A fluid sealing solution isn’t perfect until it agrees with the health of the workers operating those systems and the environment.

Therefore, the end-user must always weigh airborne contamination caused during operations, seal breakdown, and seal repair. Thus, only after making sure that a liquid can absorb heat without turning into hazardous steam itself should they employ it in their mechanical seal.


Last but not the least, the components of the barrier fluid must not react with the components of the processing fluid, nor should they react with the construction materials of the sealing system, including all gasket solutions and additional mechanical seals used by the arrangement in operation mode.

Engineered Sealing Solutions for Every Barrier Fluid

You wouldn’t have that hard a time finalizing a barrier fluid for our assembly and double cartridge seals, which come with a bigger radial wall thickness on the inside. This helps create fewer vibrations caused in extreme pressure and temperature points.

Reach out to us at 1-800-662-0585 to learn more about our mechanical sealing solutions.

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