Early in my career, I was a railway mechanic. Equipment has always fascinated me. The integrated electronic equipment enables the advanced hydraulic system on the track pads, the tie rod plug-in crane-all types of equipment to work together! This metal ballet is a beautiful thing. Then, with a rainbow-like spray of hydraulic oil, the performance came to an abrupt end. I would watch the robot assistant pull out a large three-quarter inch hydraulic hose and quickly spin a slightly clean fitting. I remember an idea that if the hose and fittings were cleaner, and if the assistant had installed the hose so that it would not rub, it might last longer (MTBF). I made a suggestion that the hose and accessories should be contained in a sealed box with one end on each size roll (MTTR). At this point, I became obsessed with finding better equipment maintenance methods. I didn't realize that there was a reliability industry, but who did it in 1980?

Hydraulic hoses are the nemesis of any heavy mechanic. In most cases, new equipment will hardly leak a drop of water, but outdated equipment may look like a sprinkler system. So what happens in the life cycle of the asset to achieve this transition, and can we avoid it? What are the best practices to avoid "cannot contain" failure modes?

Let us first consider a new asset. It arrives at the site with all hoses in a precise design length. It does not twist the hose during installation, and any angled fittings are positioned in the correct way. All clamping hardware is new and firmly fixed. The senior operator claimed the unit and entered the cab with pride. The mechanic lined up to admire the clean iron and glare from the previous unit as it headed to the junkyard.

The new device worked well, but there was a one-minute problem. A small piece of slag was left on the weld... The slag flowed through the hose and found a home in the spool of the safety valve. It sat there satisfactorily until the pressure in the system was too high, and when the safety valve opened to complete its job of managing pressure peaks, the evil nature of the slag was revealed as it quickly blocked the spool open and the system began to overheat. As the system gets hotter and the alarm starts to sound, the mechanic will take immediate action and clean the cooler, which is not helpful to someone suggesting a larger cooler. Production requires the unit to continue working. The alarm was bypassed and the device was running until the weekend. Businessmen who had not received the device training began to struggle with the schematics and invited the supplier. The young CBM guy who uses thermal imaging sees the safety valve as a heat source, but because no one has time, he gives up trying to convey this for him. The expert arrived at the site and replaced the safety valve. The warranty was invalidated due to heat problems during the operation of the unit. Everyone was happy because the problem was solved and the unit resumed work.

So what will be the remaining damage? Heat will harden the seal and make the hose brittle. On the pipe, the heat can deteriorate the neoprene retainer, causing the pipe to move with vibration, causing wear. Since the gap is minimized by heat, the valve may be scratched and cause other problems. We have now positioned the unit as requiring intervention.

Organizations that invest in high-quality training and allow sufficient time to intervene will not complicate the problem. So let us follow another clue that led to a thousand leaks and deaths.

It was noticed on the PM that the seal was leaking, so the flange was opened and a new O-ring was installed, but the 45-degree hose end was reinstalled at a slightly incorrect angle. The hose no longer bends with the movement, but has a slight twisting movement. Eventually, the movement weakened the wires and the hose failed. Contacted the warehouse and provided them with the measured value of the new hose, but did not realize that the mechanic had given them the length of the fitting, they interpreted it as the length of the hose. The longer hose has been installed and started to rub the components, but the equipment has resumed normal operation. At the same time, the pipe with the melted neoprene holder started to move and wear a hole in the pipe. The pipe was replaced by a hose...so a death spiral began.

Pipes and hoses, like fasteners, usually do not achieve the quality of workmanship they require. They also did not get the consideration of the supply chain project that they deserved. Hydraulic system leaks should not be normalized, and if several things are done right, it is not difficult. Here are some key things to consider.

Before working on any hydraulic system, make sure that all working accessories are on the ground or locked. Release any energy stored in the system. Some systems have accumulators that need to be deflated before disassembly. And don't feel that there is a leak in the energized system; if there is a pinhole leak, the pressure can easily cut off the parts you would miss.

If the listed items are followed, there is no reason for the asset to be a leaker. According to my experience, it is mainly the hasty work done with the wrong parts that can cause the machine to bleed. When I see an industrial organization with equipment leaking, it is easy to assume that they have a passive culture. High-quality workmanship and correct inventory require the support of executives and a culture that believes things can and should be done correctly. Precision maintenance is the main factor in achieving reliability and cost control. Apply it to your hoses and fittings.

This article was published in the June 2017 issue of "Machinery and Equipment MRO".

Jeff Smith is the owner and reliability subject matter expert of 4TG Industrial. To our sister publication Machinery and Equipment MRO. His work spans multiple industries, including oil sands, mining, pulp and paper, packaging, petrochemicals, shipping, brewing, transportation, and synthetic fuels. Contact him at jsmith@acuren.com.

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