TO: All fluid power engineers and designers. FROM: The Fluid Power Safety Institute™. SUBJECT: The FPSI™ wants to propose an engineering safety "standard". What's the problem? - The FPSI™ wants to propose an engineering safety "standard" to prevent the potential hazard caused by the lack of a defined point of connection for a pressure gauge, or any pressure-sensing device, in a liquid pressure transmission line wherein a check valve is used to isolate a pump from an accumulator. With the absence of a safety "standard," designers are using discretion when choosing where in the vicinity of a pump, to locate the point of connection in the circuit of a pressure-sensing device. Consequently, the point of connection in some circuits is located between the pump and the check valve, while in others, it is located between the check valve and the accumulator. Pressure-sensing device located between the pump and the check valve. Pressure-sensing device located between the check valve and the accumulator. Why is this a problem? - It creates an extremely hazardous situation when the pump is shut down and the accumulator circuit is not equipped with an automatic de-energization mechanism. If, for example, the point of connection in the circuit for the pressure-sensing device is located between the pump and the check valve, when the pump is shut off, the pressure between the pump and the check valve will immediately dissipate. Thus, the pressure gauge will indicate that there is no pressure in the circuit. However, an accumulator is a storage device for energy. Consequently, if the accumulator circuit is not equipped with an automatic de-energizing mechanism, the part of the circuit to which the stored energy in the accumulator is exposed remains under full system horsepower (pressure and flow). This leaves an unsuspecting person in a perilous situation. If, for any reason, a person, in the course of his/her work, needed to disconnect a transmission line, or remove a component, the pressure gauge would indicate that the system is safe to work on. Needless to say, the outcome could be devastating. It could lead to severe injury, death, or substantial property damage. If, on the other hand, the point of connection of the pressure-sensing device was located somewhere in the circuit between the check valve and the accumulator, the pressure gauge would provide an accurate and reliable status of the pressure in the circuit. What immediate action must I take? - We at the FPSI™ strongly urge engineers and designers to compose a "standard" for the location of a pressure-sensing device in the aforementioned application. Your assistance in this matter will help preserve the lives of the people who work on and around fluid power systems. It will also aid in preserving property and the environment. Conclusion - There are a few additional critical safety issues with regard to this bulletin: 1. A person should NEVER depend on an "on-board" gauge for reliability and accuracy. All fluid power systems should be designed with the capability of accepting a master gauge, under full system pressure. 2. All fluid power systems should be designed and built to conform to OSHA's standard 3120 "Control of Hazardous Energy (Lockout/Tagout). Download an excerpted copy here (in .pdf format), or send us a check for $10.00 (S/H, payable to FPSI) and we will gladly send you a complete copy. 3. Before working on any fluid power system follow your company's policy with regard to lockout and tagout. 4. Any fluid power system that is equipped with an automatic de-energizing device MUST have de-energization and verification capability. 5. NEVER, NEVER, NEVER, rely on sound as the means of determining that an accumulator(s) are de-energized. 6. A ball valve should NEVER be used as an accumulator-unloading device unless there is a means of verifying de-energization with a master gauge.