Mr. 0 The Practical Problem Solver (February 01, 2009)
By Brendan Casey
Problem: "What is the most effective and efficient method to diagnose internal leakage on mobile construction equipment -- e. g. a backhoe or skid steer loader -- without the aid of diagnostic tools s...
By Brendan Casey
Problem: “What is the most effective and efficient method to diagnose internal leakage on mobile construction equipment — e. g. a backhoe or skid steer loader — without the aid of diagnostic tools such as pressure gauges and flow meters?”
Solution: It’s not a bad question, but upon deeper analysis it smacks of ‘silver-bullet’ seeking. The revealing phrases are “most effective and efficient method,” and “without the aid of … pressure gauges and flow meters.”
It’s human nature to seek maximum gain from minimum effort, even if it’s not realistic. And since my job here is to entertain as well as inform, I’ll give you my ‘silver bullet’ answer first.
I’ve developed and patented a special troubleshooting paint. So now when a hydraulic problem arises, all you have to do is shake said can well and spray any hydraulic component you suspect might be faulty. After a couple of minutes, faulty components turn red and serviceable components turn green.
It’s a nice fantasy.
So to qualify the question before I answer it, until I perfect my magic spray paint, the most efficient method of troubleshooting may not be the most effective, and the most effective not the most efficient, which I assume is the reason for excluding pressure gauges and flow meters when posing the question.
But there are other tools and techniques we can employ when troubleshooting. One of them is the infrared thermometer or heat gun. The equipment required is inexpensive, its application is quick and non-invasive, and the results can be very revealing.
It’s usefulness in hydraulic troubleshooting comes about because when hydraulic fluid moves from an area of high pressure to an area of low pressure (i. e. pressure drop) without performing useful work, heat is generated.
This means components with abnormal leakage generate abnormal heat. So a double-acting cylinder with a leaking piston seal or a relief valve that is passing usually become hotter than the rest of the system. An infrared thermometer will quickly reveal them to you.
But like most other tools, an infrared thermometer is only as good as the person using it. So you do have to be careful with false positives. The objective of every troubleshooting exercise should be to prove a component is faulty before it is changed out. This is normally accomplished through a logical process of elimination.
An infrared thermometer can certainly speed up this process, but if the data coming from it doesn’t make sense or is not conclusive, then other tools should be employed to eliminate any doubt.
For example, a recent client came to the conclusion that a solenoid valve was the cause of his problem — based on temperature measurement alone. But there were two problems with this diagnosis. Firstly, a solenoid valve tends to absorb heat from its coil when energized, which could explain its temperature rise. And secondly, in the context of the particular system, it didn’t really make sense.
I explained we should note his observation but continue the troubleshooting process — using other tools as necessary — to prove the diagnosis one way or the other. That’s because a false positive is just as bad as a blind guess — it results in the unnecessary change-out of serviceable components. That’s something you want to avoid.
This article first appeared on Brendan Casey’s website,www.hydraulicsupermarket.com,where many more bits of hydraulics advice can be found. Casey has more than 15 years experience in the maintenance, repair and overhaul of mobile and industrial hydraulic equipment.
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