State the precautions to be taken when changing the fluid in

State the precautions to be taken when changing the fluid in a hudraulic system from a mineral oil based hydraulic to a fire resistant fluid.

Solution

The unique characteristics of fire-resistant fluids make it necessary to carefully consider the modifications required before converting to a fire-resistant fluid or when converting from one type of fire-resistant fluid to another.

All of these fluids have a higher specific gravity than does mineral oil based fluid. As a result, the pump inlet may need to be enlarged to avoid cavitation. Long inlet lines must be avoided, and inlet fluid strainers should be no finer than 60 mesh.

It may also be necessary to design and install additional filtration circuits on the discharge and return lines because fire-resistant fluids tend to suspend contamination much more readily than mineral base oils.

Before installing the fire-resistant fluid, the entire system must be flushed thoroughly to remove any residual contamination. Adding Varsol to the system and operating all of the circuits before draining the original hydraulic oil can help to dislodge sediment and sludge, which should be removed prior to the installation of the new fire-resistant fluid.

Make certain that compatibility tests are performed to ensure that seals, packing material and hoses will not deteriorate prematurely after the conversion is completed.

Synthetic fire-resistant fluids, such as phosphate ester, are not compatible with most standard sealing materials. Also, keep in mind that water glycol fire-resistant fluid will attack components with aluminium, zinc or magnesium materials.

The most important thing to remember when considering a conversion to a fire-resistant fluid is to become aware of all of the potential problems that can occur. Then carefully investigate all of the available options before rushing into a decision that could prove to be very costly.