Mobil Pyrotec HFD 46

Fire-Resistant Hydraulic Fluid

Mobil Pyrotec HFD 46 is a high performance fire resistant hydraulic fluid. It is designed for use in electro-hydraulic governor control systems of steam turbines, including systems using fine tolerance servo valves. It is also recommended as a fire resistant lubricant in, for example, steam and gas turbines as well as fire resistant hydraulic systems. Mobil Pyrotec HFD 46 is FM approved as a fire resistant industrial fluid.


Mobil Pyrotec HFD 46 is formulated to provide good oxidation stability. Physical properties such as foaming, air release and demulsibility are controlled to meet the limits specified by turbine manufacturers.


Mobil Pyrotec HFD 46 has been evaluated in stringent tests for fire resistance. It will burn if the bulk fluid temperature reaches 368ºC and is exposed to an open flame.  However, in the spray ignition hot manifold ignition test there is no flashing or burning at 704ºC.



Features and Benefits

Mobil Pyrotec HFD 46 has the following benefits:

•  Inherent resistance to fire hazards

•  Long component life due to excellent anti-wear properties

•  Long fluid life due to high oxidation resistance

•  FM approved



Mobil Pyrotec HFD 46 is recommended for use in:

     •  Electro-hydraulic governor control systems of steam turbines, especially where a high performance fluid is required

     •  Hydraulic and oil circulation systems operating in conditions subject to fire hazards


Mobil Pyrotec HFD 46 is unsuitable for:

     •  Hydraulic systems subjected to low temperatures. The normal operating temperature should normally be up to 65ºC to minimize thermal degradation. However, it is possible to operate with fluid temperatures up to a maximum of 150ºC.

     •  Use with Neoprene, nitrile and silicone rubber materials. Mobil Pyrotec HFD 46 is compatible with seal and hose materials such as butyl rubber and Viton.

     •  Use with petroleum oils, conventional soluble emulsions, water in oil emulsions or water glycol fluids. ExxonMobil will be pleased to give advice on flushing procedures.

     •  Use on most paints (other than two part epoxy paints), enamels and varnishes. Because of the solvent properties of Mobil Pyrotec HFD 46, it is necessary, therefore, to consider treating all internal surfaces likely to come into contact with it.


Specifications and Approvals

This product has the following approvals:

FM Global Approvals Class 6930


Properties and Specifications



ISO 46

Appearance, AMS 1738


Flash Point, Cleveland Open Cup, °C, ISO 2592


Kinematic Viscosity @ 40C, mm2/s, ISO 3104



Health and safety

Health and Safety recommendations for this product can be found on the Material Safety Data Sheet (MSDS) @