An Untrained Mechanic, And An Untrained Hydraulic Hose Assembly Fabricator - A Lethal Combination!

A mechanic that worked for a construction company stopped by his local hydraulic hose and coupling supplier to have them duplicate a damaged hose assembly, which he had removed from a machine. He handed the hose assembly to the fabricator who disappeared into the warehouse, sample in hand, to fabricate the hose assembly.

He returned a few minutes later and advised the mechanic that the store was out of stock of SAE100R2 type hydraulic hose, which was the direct replacement for the sample hose. Then he asked the mechanic if he knew the setting of the pressure relief valve in the circuit in which the defective hose operated. The mechanic apparently replied that, to the best of his recollection, it was 2000-PSI. The hose technician advised him that if the system’s pressure relief valve setting is indeed set at 2000-PSI, he could substitute the SAE100R2 type hose for SAE100R1 type hose; a hose with a lower pressure rating. The mechanic obviously trusted that the hose technician knew what he was talking about, and gave him the go-ahead to change the specification of this vital component. A short while later the mechanic left the store; new hose assembly in hand.

Upon his arrival at work, he installed the new hose assembly on the machine, and handed the machine back to the operator. Shortly after the machine was put back into service the new hydraulic hose assembly burst.

The mechanic promptly removed the defective hose assembly and returned to the store. The hose assembly fabricator opined that he may have made an error while assembling the hose (hence the need for testing), and he promptly constructed a replacement hose assembly using the same substitute hose. Needless to say, it too burst shortly after the machine was returned to service.

With two successive "accidents," the construction company's mechanic asked the hydraulic hose manufacturer to intervene. The hose manufacturer determined that the design of the machine’s hydraulic system was such that this particular hydraulic hose had to carry a higher pressure rating than other hoses in the system, thus SAE100R2 was only type of hose that could safely handle the pressure in that part of the machine's hydraulic system.

And now to my point: I hate to sound like a broken record but, had the hose assembly fabricator undergone training in fundamental hydraulics alone, he would have been empowered to know the following:

? No person has the right to modify a manufacturer’s hydraulic system without written permission from the respective manufacturer. Safety should be the very first topic students cover when learning fundamental hydraulics.

? A double acting, single rod cylinder can, under certain conditions, amplifies a hydraulic system’s pressure far beyond the system’s main pressure relief valve setting (see illustration)

Moreover, had the company’s safety manager got involved with the first “near-miss” accident, he/she would have prevented a second "near-miss" accident, which could have had a very different outcome.

Safety professionals do not get involved with matters pertaining to hydraulic safety, or accidents related to hydraulic systems, because hydraulic safety is nowhere to be seen on their safety radar screens. Less than 1% of corporate safety professionals fully understand all facets of safety as it relates to hydraulics; this includes lockout and tagout. Even companies with vigorous “near-miss” reporting programs, generally don’t “near-miss” hydraulic transmission line failures.

Untrained hose assembly fabricators routinely make a host of additional errors, which could compromise the integrity of the hydraulic hose assemblies they fabricate, and leave end users susceptible to a host of accidents that could cause severe injury, death, and/or substantial property damage. Here are a just a few examples:

? Untrained hose assembly fabricators cut hydraulic hoses with “chop-off” saws fitted with aluminum oxide cutting wheels, which are designed for cutting steel and steel alloys. These types of saws should never be used to cut hydraulic hoses. The debris left in the hoses cause or contribute to accelerated hydraulic component wear, which is seldom, if ever, traced back to the hose supplier.

? Untrained hose assembly fabricators cross-brand hoses, crimp fittings, and crimping machines. While hydraulic hoses and fittings are supposedly built to strict SAE specifications, reputable hose and connector manufacturers like Gates, Parker, et al., provide strong warnings about potential failures due to the practice of cross-branding.

? Untrained hose assembly fabricators don’t know how to properly clean, inspect, or test assemblies post fabrication. Contamination is the leading cause of hydraulic component failure. Contamination, which is routinely left in hydraulic hose assemblies, can lead to systemic failures, which can cause accidents, loss of production, and exorbitant repair costs.

? Untrained hose assembly fabricators routinely make hose assemblies, which are the main arteries that provide hydraulic power for machines that people’s lives depend on: aerial platforms, scissor lifts, bucket trucks, and amusement park rides. Here is a daunting thought! It is highly likely that the technician that installed one, or more, of the vital oil transmission lines on the aforementioned machines, had little or no training in hydraulics, and/or hydraulic hose fabrication techniques.

Since the fluid power industry seems to be more than happy with the status quo, and, there is overwhelming evidence that OSHA and MSHA have absolutely no interest in getting involved, please allow me to give you some very important advice as to how you can avoid becoming a victim of an accident related to sub-standard hydraulic hose assemblies:

? If you work for a hose and coupling dealer, or if you work for a company that makes hose assemblies in-house, and you have had no formal training in making hose assemblies, or have only been exposed to training in fundamental hydraulics, you should inform your supervisor immediately. If your supervisor ignores you, take the matter to your company’s safety department. If your requests for proper training are still ignored it is imperative that you make a note of the date of your request(s), your supervisor’s name, and the outcome of your request for training. This information will serve you well should a hose assembly you make fail unexpectedly, and cause an accident. Your supervisor will have to convince a jury of his/her or her peers, why he/she declined your much needed.

? Hose and coupling dealers MUST NEVER make hose and/or connector substitutions of any type without written permission from the original equipment manufacturer. In other words, never take the engineer out of the loop.

? Before you conduct business with a local hose fabricating company, inspect their facilities, and chat with their fabricators. If the place looks like a pig’s breakfast, that’s what the inside of the hose assembly will look like when you install it in your $100K hydraulic system. Also inspect the crimping machines and cut-off saws. Note how the hoses are stored. Ask what they use to clean the finished assemblies, and ask if the assemblies are tested.

? If you cannot write a “terms of business” with your hose supplier, let me help you. You must put the company’s management on notice that cross branding will only be permitted if authorized by the respective hose, connector, and crimping machine manufacturer. Moreover, put the company on notice that if a hose assembly they supplied fails the matter will be handled as an accident, which, of course, it is. Inform them that your company will conduct its own internal investigation into the root cause of the failure. If necessary, have a third party analyze the failure so that the root cause is not swept under the mat. Inform them that once you have completed the internal investigation, they will be invited to send a qualified representative to your company to explain why the failure occurred. No more Mr. nice guy!

All companies that provide hose assembly fabrication services have a duty of care to insure the product (s) they deliver to you are consistent the hose and connector manufacturer’s specifications – absolutely no deviations allowed!  

? If you hire an outside hose and connector contractor to perform work on your hydraulic equipment, make it a condition of contract that the technician assigned to the task brings his/her certificate(s) of training with them. If the technician does not have a certificate of training in fundamental hydraulics, DO NOT allow that person to work on your equipment. You are responsible for their safety while they are working on your premises.

? The same applies to companies that provide on-site hose replacement services. Unless their technicians have certificates to prove that they have received the proper training, don’t let them go anywhere near your machinery or equipment.

? If you rent a scissor lift, bucket truck, aerial platform, etc., have the rental company sign a contract stating that all hydraulic hose assemblies on the equipment you are renting have been constructed by people that are trained and certified in making hose assemblies. The vast majority of mechanics that repair, service, and maintain personnel lifting devices, amusement park rides, and cranes, have no formal training in fluid power.

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