Comparison of G-1 and Met-L-X Powder

Spontaneous Heating and Pyrophoricity

DOE-HDBK-1081-94

PYROPHORIC METALS

thin layer of agent is cautiously applied over the burning mass. Once control is

established, the nozzle valve is used to throttle the stream to produce a soft,

heavy flow. The metal can then be completely and safely covered from close

range with a heavy layer. The heat of the fire causes the powder to cake,

forming a crust which excludes air and results in extinguishment.

Met-L-X extinguishers are available for fires involving magnesium, sodium

(spills or in depth), potassium, and sodium-potassium alloy (NaK). In addition,

Met-L-X has been successfully used where zirconium, uranium, titanium, and

powdered aluminum present serious hazards.

Comparison of G-1 and Met-L-X Powder

Based upon their past usage and known value as extinguishing agents for metal

fires, the two agents previously discussed (G-1 and Met-L-X powders) are the

most notable. Continuous experience with these agents has provided sufficient

information to list, in Table 3, the capabilities and limitations of each when

applied to certain metal fires.

Na-X Powder

This powder was developed to satisfy the need for a low chloride content agent

that could be used on sodium metal fires. Na-X has a sodium carbonate base

with various additives incorporated to render the agent nonhygroscopic (does

not absorb moisture) and easily fluidized for use in pressurized extinguishers. It

also incorporates an additive which softens and crusts over an exposed surface

of burning sodium metal. Na-X is noncombustible, and does not cause

secondary fires when applied to burning sodium metal above temperatures

ranging from 649 to 816 C (1,200 to 1,500 F). No known health hazard results

from the use of this agent on sodium fires, and it is nonabrasive and

nonconductive.

Stored in 23-kg (50-lb) pails, 14-kg (30-lb) hand portables, and 68- and

160-kg (150- and 350-lb) wheeled and stationary extinguishers, Na-X is listed

by UL for fires involving sodium metal up to a temperature of 649 C

(1,200 F). Na-X has been tested on sodium metal (spills and in depth) at fuel

temperatures as high as 816 C (1,500 F). Stored in the supplier's metal pails

and extinguishers, Na-X is not subject to decomposition, so periodic

replacement of the agent is unnecessary.

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Pyrophoricity