Do you understand the component that you are adjusting?

Is the technician above working safely and with adequate knowledge? It would appear to many as common sense, that one would not adjust a hydraulic component without knowledge of that component's function. But I find that it is actually quite common to witness a technician turning an unknown adjustment screw just to see what will happen.

Some pumps have several adjustable pressure controls and perhaps an adjustable minimum or maximum displacement stop. Adjusting the maximum displacement on a piston pump is one serious matter, while it is quite another critical matter to accidentally or incorrectly adjust the minimum displacement screw which prevents a pump swashplate from reaching the zero or near-zero angle.

Clockwise or Counterclockwise?

A basic screw-in style, cartridge valve may look just like another one that you know quite well, but it may have an entirely different function, as noted by the tiny letters and numbers on the model code. For some adjustment screws, clockwise turns result in lower pressure, where most technicians expect the opposite result.

In the case of some pressure valves, a one quarter turn will change the pressure value by 50 PSI, while in other cases that same quarter turn will cause a 500 PSI change. That's a big difference. Machinery damage or even worse, worker injury could easily be the result of ignorance.

Quality training is a "must" for hydraulic system maintainers and troubleshooters.

Some adjustment screws will back right out! 

It's true! Some hydraulic component adjustment screws can be backed right out of the component housing. Some screws have an internal stop to prevent this from happening. Do you know what to expect for each screw? The unexpected release of hot, pressurized hydraulic fluid could easily result in a serious injury.

I haven't kept empirical data, but I'd say that approximately two out of every five adjustment screws that I've worked with in the last year on a variety of hydraulic systems, were the type of screws that would back right out of the housing if turned too far.

Some of these components were several decades old. Some of these components I knew quite well, while others were models or brands that I had not previously encountered or worked with directly. If the system needs to be completely re-adjusted or re-commissioned and if I can't verify any other way, I shut the system down, achieve a zero energy state, note the current screw position (count the turns) and back the screw out to find out if there is a stop or not.

Reading data sheets pays off, for safety and for proper system work.

An important part of my solution when asked to help out with system issues or when providing training on a system where adjustments will have to be made, is to read and do research.

I study the system schematic of course. I also like to read system notes from the machinery manufacturer. Usually there are great insights to be found. In some cases, the insight is on the lack of detail and documentation that the manufacturer provided. A simple block-diagram style schematic, with overly simplistic explanations about system or component functions, as the only provided documents, leaves me worried for the maintainer or troubleshooter.

I read and re-read many component specification and data sheets every week. It's impossible to know them all or memorize them all. A trainee at a recent course that I conducted for heavy equipment mechanics said with humour, "You're trying to turn us into book mechanics". I kindly asked him to clarify his thoughts on this matter and he bravely offered leadership to his more junior colleagues in the classroom as he said "No it's OK, this is a necessary skill now, to read component and service data. The systems are more complex than they were in the past". I was grateful for how that discussion concluded.

Manufacturers improve component safety

Many manufactures are adding adjustment safety stops to adjustment screws where they did not have them in the past.

Manufacturers make changes with a new series of a component model that you may know quite well. This may mean that an adjustment screw that does not back out on a newer model, might back out on the same general model but in the older design series.

The maximum displacement screw became bent on an older model piston pump in our fleet of training models. I ordered a replacement part. When it arrived I noted that the new screw had a ridge after the threads that is intended to stop the screw from being backed out. Now our older pump has a newer generation adjustment screw. I had to take the pump apart and install it from the inside.

I like to keep track of data sheets from several design generations of the same general products line and product model. There are details in the information that are important to verify from time to time.

Get help and training!

This is a general discussion of how a simple adjustment screw can make significant changes to the operating state of a hydraulic system. The screw can even turn right out of the component housing in many cases. For both issues, human safety could be easily jeopardized. In conclusion, if you are not sure how to correctly and safely adjust a hydraulic component, simply don't do it. Get a knowledgeable hydraulics expert involved and pursue thorough component and system training as needed for your maintenance and troubleshooting work.

Carl Dyke resides in Central Alberta, Canada and collaborates daily with the team of very passionate individuals who create & deliver the products and services of CD Industrial Group Inc. 

Carl grew up looking after the machinery and equipment used in timber and lumber processing. After some early career years spent in public education, a unique enterprise was born. Carl and team spend their days demystifying complex machinery, creating interactive art and software that aids learning, and conducting instructor-led, hands-on hydraulics maintenance training for a wide range of heavy industries. CDIG has delivered hydraulics training to 1000's of technicians worldwide.

For the most complete, animated and highly interactive hydraulics e-Learning, see our LunchBoxSessions site. Get a hydraulics training boost with our popular YouTube channel.

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