TO: All maintenance personnel and others who might be involved with hydraulic hose replacement. FROM: The Fluid Power Safety Institute™. SUBJECT: Hydraulic Hose substitution - What you don't know may hurt you! What's this Safety Bulletin about? - When a production machine is "down" and there are no direct replacement parts available, a maintenance professional will often-times have to "make a plan" to get the machine back into production. There is no problem with making a component substitution if a person removes an "apple," and substitutes it with an "apple." However, when a person removes an "apple," and substitutes it with an "orange," it could inadvertently create an extremely hazardous situation. This Safety Bulletin focuses on what you must know when substituting one diameter of hose for another. Tell me more! - To make our point, let's use the following example: The size of a hydraulic hose that transports oil from a directional control valve to a cylinder is 1/2" - SAE100R1. The hose develops a leak, and it is necessary to replace it. However, the direct replacement hose (1/2" - SAE100R1) is out of stock, and all that is immediately available is 1" - SAE100R1. There is also an abundant supply of 1" to 1/2" crimp-on connectors in stock. The 1/2" being identical to the connectors on the ends of the defective hose. So what's the problem? Let's get production underway! Not so fast, there is one important fact to consider: If the hose diameter increases, what, if any, effect does it have on the working pressure of the hose? This is a critical safety issue a person MUST take into consideration when making hose, or other, substitutions. It is vital that safety is taken into consideration when making any and all component substitutions. If not, it could lead to unexpected failures, which could result in severe injury, death, or substantial property damage. When the diameter of a hose increases, in the majority of cases, the rated working pressure decreases! In this case, the rated working pressure of the 1/2" hose is 2000 PSI (138 bar), while the 1" hose has a rated working pressure of 1000 PSI (69 bar) - a 50% decrease in the rated working pressure of the hose! Let's reverse the situation - a 1/2" hose is used in place of a 1" hose. The advantage: an appreciable increase in rated working pressure of the hose. The disadvantage: a significant increase in the velocity (speed) of the oil as it passes through the hose. An increase in oil velocity will cause an increase in resistance. The net result of increased resistance is an appreciable increase in oil temperature. Conclusion - NEVER make a component substitution without taking into account ALL the specifications of the substitute part(s). If necessary, share the information with your engineering and/or safety departments for their evaluation and approval. Also, if it is necessary to install a smaller diameter hose as a temporary measure to keep production up and running, make sure it is just that - TEMPORARY! Industrial plants across the nation are closing down because the costs associated with keeping them in operation are prohibitive. This is caused, in part, by the number of "temporary" repairs that became "permanent!" It is more cost effective to replace $250.00 worth of hoses today, than $25,000.00 worth of hoses tomorrow!

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.