TO: All fluid power engineers and designers. FROM: The Fluid Power Safety Institute™. SUBJECT: Product Safety Alert - Pressure Relief Valves. Introduction - The FPSI™ is concerned that a number of pressure relief valve, and pressure-compensated pump manufacturers have inadvertently created a safety hazard in the design of their respective pressure-adjusting screws. What's the problem? - The adjusting screws on a number of pressure-compensators and pressure relief valves can screw all the way out of their respective housings (diagram A) when being adjusted to their lowest pressure settings (backed all the way out). In this design, there is nothing to stop the adjusting screw from coming out of the valve housing. Therefore, pressure will propel small parts out of the housing at high velocity when the adjusting screw is backed-out all the way. This design stops the adjusting screw from coming out of the housing, and therefore makes it safe to back the adjusting screw all the way out while there is pressure in the system. diagram A and diagram B This "design oversight" leaves unsuspecting personnel highly susceptible to a number of extremely hazardous situations, if they are making adjustments while the system is in operation: 1. The pressure can propel the small parts out of the housing at high velocity. These parts can strike the person doing the work, and/or bystanders, and cause severe injury or death. 2. The ensuing "blast" of hot oil discharging from the vacant housing could spray in the direction of the person doing the work, or bystanders, and cause severe burns that could lead to injury or death. It could also lead to severe eye injury or blindness. 3. The oil spray could come into contact with an ignition source, and cause a fireball that can result in severe injury, death, and/or substantial property damage. What can I do to solve the problem? - 1. If you currently have products that fit this profile, make everyone aware of the problem immediately. 2. Tell personnel to turn the power-unit off, whenever backing a relief valve (of any type) adjusting screw, or pressure-compensator adjusting screw, all the way out. 3. Make the people who design and build these products aware of the problem. 4. When you are specifying components inspect them for safety. If the pressure and/or flow adjusting screws can come out of the housing during routine service, maybe, that's not the product you want to purchase. The valve design shown in diagram "B" might be a better alternative. 5. When you design and specify pressure-compensated pumps, and relief valves of any type, ask the salesperson the status of the adjusting screws. If you have no alternative but to purchase that type of pump or relief valve, you MUST add the necessary cautions and warnings in the service literature, and on the machine. 6. Remember, while the first order of business is to protect the life and limb of people, liability is an important issue. Don't let someone else's design-oversight cause your company to have to spend the next ten years defending itself in court. 7. Write a job safety breakdown (JSB) for setting pressure relief valves, and pressure compensators. Conclusion - Be aware, that there is no standard for relief valve or pressure-compensator adjusting screw design in the industry. Consequently, maintenance personnel, and others, are subjected to unnecessary risks because some manufacturers choose to design pressure-adjusting screws that operate safely, and others don't. In this case, it is wise to error on the side of safety! When re-adjusting a pressure relief valve or pressure-compensator follow this procedure (guideline only): 1. Turn the power-unit off. 2. De-energize the system, and verify that the system is safely de-energized. 3. Back the pressure relief valve or pressure-compensator adjusting screw all the way out. 4. If it comes all the way out, screw it back in until it comes into contact with the spring, or it is sufficiently deep enough in the housing so it won't come out under pressure. 5. Install a master (test) gauge. Never use permanent-mount gauges when making pressure adjustments. 6. Start the prime mover, and set the pressure relief valve or pressure-compensator at the specified pressure. 7. Lock the jam nut (if equipped). 8. Turn the power unit off, and remove the master gauge. 9. Tighten all connectors in accordance with the respective connector manufacturers torque specifications. WARNING! Only trained, authorized personnel should be permitted to make pressure and flow adjustments. Untrained personnel can expose themselves to hazards that can result in severe injury or death.