(Ref. No: MSB-004)

What's this Maintenance Safety Bulletin about? A number of people have informed the FPSI™ that untrained maintenance personnel have inadvertently installed check valves in reverse - we are deeply concerned for their safety!
To whom is this bulletin directed? To untrained people who do not understand fluid power symbols, their supervisors, and their managers.
What's the problem? Numerous check valve manufacturers stamp the ANSI (American National Standards Institute) symbol on the side of a check valve for identification purposes. In some cases a check valve is marked with the words "free-flow" and an accompanying arrow indicating the "free-flow" direction. However, untrained personnel identify the symbol with a "weird" looking arrow, and thus, are inclined to install the check valve with the "arrow" facing the direction of flow - the direction in which the flow path is totally blocked!
What could happen if a check valve is installed incorrectly? If a check valve is located between a fixed-displacement pump and a relief valve, the result will be a catastrophic (fragment) failure of the pump, check valve, transmission line, or associated component(s). This type of failure can lead to severe injury or death. If a check valve is located downstream of a fixed-displacement pump, and a relief valve, the system will remain at maximum pressure while the pump is operating.
What is the correct way to install a check valve? This illustration shows the correct way to install a check valve.
This illustration shows the incorrect way to install a check valve.
What immediate action must I take? 1. Stop untrained personnel from working on and around fluid power systems with immediate effect, until they are properly trained. If the problem associated with this bulletin doesn't hurt them, another one, sooner or later, will! 2. Incorporate fluid power safety into your company's overall safety program. 3. Discuss this safety bulletin with ALL untrained personnel who work on fluid power systems. 4. If you are not sure - ask! Always err on the side of safety!
Conclusion - Installing fluid power components incorrectly is a serious safety hazard. People who work on and around fluid power systems MUST BE empowered to make sound safety decisions - we owe them and their families that right - let's help them!

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