Preface:

This is the second edition of CSA Standard CAN3-M423, now CAN/CSA-M423, Fire Resistant Hydraulic Fluids. It is written in SI (metric units and supersedes the previous edition published in 1984.

This Standard divides hydraulic fluids into three categories. The reasons for this are to recognize the present state of the art, and to permit upgrading of fluids and fluid systems to meet requirements for fire resistance. The categories are described as follows:
(a) Category 1: These fluids are the most fire resistant and show no measurable flame persistence in the flammability tests specified in this Standard.
(b) Category 2: These fluids are not as fire resistant as the fluids in Category 1 but still meet the flammability tests (with longer flame persistence) specified in this Standard.
(c) Category 3: These fluids are considerably more fire resistant than mineral oils but are only required to pass the spray flammability test in this Standard. They are usually compatible with systems designed to use mineral oil.

This Standard has been prepared as a result of a request from the Provincial Inspectors of Mines for a Standard to cover the safety aspects of hydraulic fluids, which are used extensively in the hydraulic systems of mining machinery.

The major changes from the 1984 edition of M423 consist of the following:
(a) Clause 4.3, Fluid Stability: The acceptable oil separation for water in oil emulsions has been decreased from 3% to 2%.
(b) Clause 4.4, Toxicity: This Clause has been expanded to include detailed criteria on acute toxicity, acute skin irritation, acute eye irritation, sensitization, and chronic toxicity.
(c) Clause 5.1, Preconditioning Test: The preconditioning test is now to be carried out only on non-aqueous hydraulic fluids.
(d) Clause 5.4.3, Freeze-Thaw Stability Test: The number of cycles of exposure completed in this test has been increased from two cycles to seven cycles.

Scope:

1.1
This Standard covers the fire resistance, toxicity, and stability with respect to separation of water-in-oil emulsions of hydraulic fluids intended for use at mines.

1.2
This Standard covers fluid in the following categories:
(a) Category 1 - fluid that shows no measurable flame persistence (ie, less than 1 s) in either of the flammability tests specified in this Standard;
(b) Category 2 - fluid that passes both the spray and wick flammability tests specified in this Standard;
(c) Category 3 - fluid that passes the spray ignition test specified in this Standard but may not be capable of passing the wick test.

1.3
This Standard does not cover products of combustion or products of thermal degradation from hydraulic fluids subjected to fire or heating.
Note: While the object of this Standard is to establish a reasonable level of fire resistance for hydraulic fluids, it is recognized that any hydraulic fluid may burn under conditions different from those described in this Standard.