TO: All maintenance personnel. FROM: The Fluid Power Safety Institute™. SUBJECT: All cartridge valves are not created equal! Introduction - A maintenance technician, with no formal training in fluid power, narrowly escaped serious injury after installing a new cartridge valve when the cartridge valve body fragmented when he started the machine. His mistake! He assumed that by the mere fact that the cartridge valve screwed into the body and fitted properly, that it was the correct cartridge valve. In another incident an untrained diesel mechanic suffered minor injuries when a driveline, multiple disc brake, fragmented when he started a machine, after installing a new cartridge valve and body assembly. His mistake! He assumed that the number "1" that was stamped in the valve body, adjacent to a threaded port, marked the inlet port (diagram 1). He also assumed that the port opposite to, and on the same axis as, the adjusting screw, offered further proof that port "1" was the correct port. He connected the transmission lines accordingly, not realizing that he had inadvertently reversed the inlet and outlet transmission lines! Tell me more! - Screw-in cartridge valves offer a wide variety of control functions in a lightweight, space-conserving package. Thus, they are extremely popular in both mobile and industrial applications. Typical control functions include pressure control, flow control, flow check, flow dividing, and others. There are numerous cartridge valve manufacturers worldwide. However, they DO NOT design and/or build their respective cartridges to interchange with one another's cartridge and/or body assemblies - this is important! What must I be particularly careful of with regard to cartridge valves? - There are two elements that you must be very aware of with regard to cartridge valves: 1. Body and cartridge interchangeability. 2. Port identification character markings. 1. Body and cartridge interchangeability - Flow rate generally dictates the physical size of the valve body, and in turn the "cavity" size. The cavity is the uniform, threaded opening in the valve body that is designed to accept a specific cartridge. For example, one body size might handle flow rates ranging from 0 - 25 GPM, and another, flow rates from 0 - 50 GPM, and so on. Flow rate also dictates the cartridge size, which corresponds directly with body size. For example, a 0 - 25 GPM cartridge fits into a 0 - 25 GPM body. NOTE: Any control function cartridge rated for 25 GPM (made by a given manufacturer), will fit into any 25 GPM body. WARNING! The fact that a cartridge valve fits into a body correctly, is no indication that the cartridge valve is correct (diagram 2). 2. Port identification character markings - Two types of characters are typically used to mark the various ports in a valve body: a. Numbers - usually ranging from 1 to 3. b. Letters - typically "P" for pump, "T" for tank, and "DR" for drain. While the letters are, for all intents and purposes, self-explanatory, the numbers can be misleading. Untrained people are vulnerable to a number of safety pitfalls when they are dealing with port numbering: 1. They assume that all cartridge valve manufacturers use the identical port numbering sequence - Wrong! The FPSI™ is unaware of any standard that cartridge valve manufacturers subscribe to for a common port numbering sequence. 2. They assume that the number "1" always corresponds with the inlet port - Wrong! A given manufacturer might use the number "1" to designate the inlet port for a body with a relief valve cartridge, for example. However, using the identical body for a pressure reducing valve cartridge, the number "2" marks the inlet port! WARNING! Never use logic, and/or guess, when you are dealing with fluid power components. One error could lead to severe injury, death, or substantial property damage. IF YOU ARE NOT SURE - ASK! What's the safest way to make the proper identification? - A cartridge valve will usually have its own identification number or part number. The number is usually stamped on one of the sides of the hex on the cartridge valve body (diagram 3). When replacing a cartridge, CHECK THAT THE NUMBER AND/OR LETTERS ON THE OLD CARTRIDGE CORRESPOND EXACTLY WITH THOSE ON THE NEW ONE. If there is a discrepancy in even one letter, or one number, DO NOT install the cartridge. Call the supplier/manufacturer for clarification! This advice also applies to the valve body (diagram 4). What must I do to correct the problem? - 1. Engineers and Designers - a. Show the relative port numbers or markings on all diagrams and schematics (diagram 5). This is critical information for assembly-line personnel, and maintenance personnel! This is extremely important! 2. Instructors - a. Take an actual valve into your classroom, and pass it around while you show your students where to find the appropriate markings on cartridges and bodies. b. If you have simulators that are equipped with cartridge valves in your classroom-let students get used to making the proper connections using the numbers or letters on the respective valve bodies. Let them learn how important it is to have the numbers or letters, marked on the diagram, correspond with the ones on the various valves. c. Prior to a simulator lesson, hand a valve to a student and let him/her tell the group how to install it. If he/she is unfamiliar with the number or letter reference, you will see a "mechanical mind" in action. The student will figure out the port connection using logic! They will invariably tell their colleagues to use the adjusting screw as reference - the port opposite the adjusting screw is the inlet port! In the case of pressure control valves, logic will not prevail, it will fail! 3. Maintenance Personnel - a. Take note of the port markings when removing and installing valves. If necessary make a drawing, and mark the transmission lines appropriately - you only have one opportunity to install a pressure control valve correctly! b. Take note of the markings on valve cartridges and bodies. If paint disguises the marking, clean it off. If the part number of a replacement valve is not absolutely identical to the new valve, DON'T INSTALL IT! CALL THE SUPPLIER/MANUFACTURER FOR HELP. c. If the replacement valve is purchased from a different manufacturer (not the same brand), you MUST get approval from your engineering department before making the substitution. 4. Safety Personnel - a. Bring this matter to the attention of the appropriate personnel. If necessary, read this safety bulletin in your safety meeting. b. It is your responsibility to make sure that untrained personnel DO NOT work on and around fluid power systems. Training empowers people to make safety-based decisions! 5. Students - a. Never hesitate to ask a question of your instructor. If you see a marking on a valve, ask the instructor what it/they mean. Remember the aphorism: "if you ask a question you might be a fool for a minute, if you don't, you might be a fool forever!" b. If you work on a simulator during the course of your instruction, and you are unsure about correct port identification, ask the instructor for guidance. If the instructor simply points to a port, ask him/her, "why that port?" 6. Technical Writers - a. When writing instructions/information about cartridge valves, ALWAYS use the numbers and/or letters as reference. b. Provide generic illustrations showing the proper identification markings on all components. c. Provide appropriate cautions and warnings about the consequences of a person failing to follow proper transmission line/port connection procedures. Conclusion - There are two ways to eliminate these types of hazards: 1. Training - We must do everything in our power to insure that every person who works on and around fluid power systems is properly trained. 2. Absence of standards - Let's encourage dialogue between manufacturers that will serve to create as many standards that are both realistic and feasible, yet, will eliminate these types of hazards.

Waiver of Liability -

The Fluid Power Safety Institute™ does everything possible to ensure that the information and drawings contained in this safety notice are accurate, and the suggested procedures are deemed safe and reliable. However, these are general recommendations only and might not be applicable to all situations. You MUST have your engineering department in conjunction with your safety department read these recommendations and make the necessary changes for your application. The Fluid Power Safety Institute™ is not responsible for actions taken by untrained and/or unauthorized persons. Trained, authorized persons only should do ALL fluid power system service, repair, and troubleshooting.