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May 2003: Hydraulic Fluids - Part 2

While they can be found in various occupancies including plastic injection molding, petroleum based hydraulic fluids are often used in metal working facilities. In most metal working operations, combustible loading is normally very low. The level of fire suppression needed in the building is usually a variable of how much hydraulic fluid is in use. If equipment reservoirs are small and the building is noncombustible, automatic sprinklers may not be needed. However, when the quantity of fluid increases, sprinkler protection is needed regardless of building construction or the overall combustible loading throughout.

Most petroleum based hydraulic fluids have a flash point in excess of 300°F, which classifies them as a combustible liquid. Combustible liquids will burn. According to the May 2000 edition of FM Global Data Sheet 7-98, "Hydraulic Fluids," automatic sprinkler protection is needed over and 20 ft. beyond the equipment if the reservoirs are greater than 100 gallon aggregate capacity (adjacent machines within 20 ft. of each other) or individual machines. Complete building protection is needed if the building and/or the surrounding occupancy are combustible.

In past editions of Data Sheet 7-98, the recommended ceiling sprinkler design density was .15 gpm/sq. ft. over 7,500 sq. ft. This large operating area often required major reinforcement to an existing sprinkler system and was based on the idea that the fluid, being under several hundred pounds of pressure, would spread well beyond the equipment if an oil line were to rupture (see Risk Logic, September 1999 article).

Loss experience has shown over the years that a design of .2 gpm/sq. ft. over 3,000 sq. ft. with high temperature sprinkler heads will control a fire, as indicated in Table 2 of Data Sheet 7-98. However, sprinklers may be omitted over a single hydraulic system or multiple adjacent systems within 20 ft. of each other if all of the following criteria are met:

1.The aggregate oil capacity does not exceed 100 gallons.

2. The construction and adjacent occupancy is non-combustible.

3. Business Interruption (BI) potential is low.

4. Provisions exist for automatic or prompt manual shutdown of the equipment.

Another requirement in Data Sheet 7-98 is the provision of an automatic shutoff device for machines with reservoirs greater than 100 gallons. Equipment shutoff can be triggered by a sprinkler waterflow alarm, a thermal sensor or a fluid level switch interlocked with the power supply for the oil pump. These shutoff devices are not needed, however, if the following criteria are met:

1. Automatic sprinklers, based on Table 2 of Data Sheet 7-98, adequately protect the equipment.

2. There is no significant BI potential from the machine in question or, if there is a large BI potential, at least one manual remote shutoff is accessible and the area is constantly attended by trained operators who:

a. Know the location, function and operation of emergency shutoff switches.

b. Know the location, function and operation of fire extinguishers and fire hose equipment.

c. Understand the necessary precautions to avoid accidental rupture of hydraulic piping.

d. Are trained in the procedures for prompt cleanup of spills or leaks.

As an alternate solution to above protection measures is to consider FM approved less flammable hydraulic fluids. These fluids are water based and do not require sprinkler protection or emergency shutoff devices. New equipment can usually be designed for use with the water based fluid, but there may be operational problems with equipment initially designed for petroleum fluids. The manufacturer of the equipment would be the best source to pursue before changing fluids (see Risk Logic, April 2001 article).

Determining the level of protection required for an occupancy using petroleum based hydraulic fluids can be challenging. It requires accurate data on reservoir size of all equipment in the facility and information on any installed shutoff devices.

For details concerning emergency shutoff devices, equipment maintenance and the required sprinkler protection, contact Risk Logic.