How well do YOU know YOUR hydraulic equipment?

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My wife often asks me why I still take on consulting work. She wonders why I happily leave the comfort of my office to crawl all over hot, dirty, smelly hydraulic equipment.

Well for one, I actually enjoy it. Two, it keeps my sharp. But perhaps most importantly, it keeps me in touch with the issues that hydraulic equipment users grapple with.

One thing I have learnt over the years is that in the initial stages of a consulting assignment, it's better to ask intelligent questions rather than dispense good advice.

A recent client had a set of pumps worth $50,000 fail after achieving only half of their expected service life. And they wanted some answers. At the initial meeting the client opened proceedings with a brief history on the machine, an account of the events leading up to the failures and then pushed a stack of oil analysis reports across the table.

After I finished taking notes on what I'd just been told, I fired off my first question:

"What is the system's normal operating temperature?"

Stunned silence. Client shrugs his shoulders.

"O-K ... what's the system's usual operating pressure range?"

Blank look from client. "Err dunno ... we don't monitor either of those things."

At the end of the meeting we took a walk through to the control room. Turns out, both operating pressure and temperature were displayed on the default PLC screen - albeit along with a lot of obviously more important production information. Say no more.

But could YOU answer these two simple questions about the "vital signs" of your hydraulic equipment? If not, I strongly recommend you make the effort to get to know your equipment better.

This information is easy to collect, can give valuable insight to the health of your equipment and is essential data if failure analysis is required. Here's how I recommend you do it:

First you need an infrared thermometer, also called a heat gun. If you don't have, you'll need to invest around $100 to get one.

Next, using a permanent marker, draw a small target on the hydraulic tank below minimum oil level and away from the cooler return. Label it 1. This marks the spot where you'll take your tank temperature readings. The idea behind these targets is that regardless of who takes the readings they'll be taken from the same place each time.

If the system is a closed-circuit hydrostatic transmission, mark a convenient location on each leg of the transmission loop and number them 2 and 3. Skip this step for open circuit systems.

Next, mark a target on the cooler inlet and outlet and number them 4 and 5. This records the temperature drop across the cooler. The benefit of doing this is explained in this article.

With that done, now draw up a table like the one below to record these temperatures and a few other essential parameters. Note that there is little point in recording the temperature across the cooler (4 & 5) if the fan isn't running. And charge pressure is only relevant to closed-circuit hydrostatic transmissions.

Date02-06-1208-06-12
Time16150640
Ambient Temperature1139
Operating Pressure30002900
Charge Pressure270250
(1) Tank Temperature3068
(2) Transmission A4160
(3) Transmission B4465
(4) Cooler In 64
(5) Cooler Out 53
Fan On Yes/NoNoYes

I recommend you take readings on the hottest and coldest days of the year and on a couple of average temperature days in between. This provides a baseline of data. Beyond that, taking readings at regular intervals - daily, weekly or monthly, can provide early warning of problems. And if the hydraulic system starts to give trouble, taking a set of readings will reveal if it's operating outside of its normal parameters.

Related articles:

Hydraulic equipment reliability - begin with the end in mind
Hydraulic press failure illustrates the importance of scheduling change-outs
How to tell if your hydraulic equipment is 'sick'

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