6 Test Methods on Fire Resistant Hydraulic Fluids

Over the years, test procedures for mineral hydraulic oils have been standardized and agreed to by user and manufacturing industries as well as by the various standardization bodies. But common test standards to evaluate the fire resistance of hydraulic fluids are still a distant goal. The fact that there are approximately 50 test methods [1] and more than a dozen standardization bodies involved indicates the complexity of the problem. In fact, agreement even on the terminology related to “fire resistance” is still in the evolving stage. The reasons are not far to seek. A wide variety of ignition sources—for example, the many combinations of fluid leakage and ignition in industrial practice—have brought about many types of ignition tests. Also, it is difficult to simulate the exact fire conditions encountered in different applications. Fire hazard conditions in mining industries differ considerably from those in, say, metalworking or aerospace industries; molten metal ignition tests meant for hot metal casting operations may not adequately represent the operating conditions of metalworking industries. In other words, each industry has its own particular fire hazards that require their own set of test conditions, and hence it is difficult to develop a universal test procedure. These tests, therefore, at best can be used to compare the relative flammability of different fluids; they cannot fully ensure the performance of a fluid in actual fire conditions, which can differ very much from those of the test.

Given the complex nature of the problem, the efforts to develop more reliable and acceptable methods are still continuing. Extensive work on test methods has been done at various centers [1–13], and we can be optimistic that, in the near future, the number of test procedures will narrow, signifying that users, manufacturers, and standardization bodies have reached a consensus on fire resistance.

It is beyond the scope of this book to give an account on all the test procedures that are available; only those that are important and commonly used in industries are outlined here. Most of the tests are qualitative, i.e., the results they give are pass/fail. Quantitative assessments, of course, would help users discriminate among available fluids and select the one that is most suitable for the given operating conditions. Summaries of common test procedures are given in references [1–4].