Hydraulics Glossary – A

External damage (to the hose assembly) caused by rubbing on a foreign object, wearing away by friction.

A measure that at its zero or base point, has a complete absence of the entity being measured.

The indicated value of the weight of the earth’s atmosphere. At sea level this value is approximately 14.65 pounds per square inch (psi). Absolute pressure is zero-referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure.

The ratio of shear stress to shear rate. It is a hydraulic fluid’s internal resistance to flow.

The integration of one material into another.

A container or vessel, normally cylindrical, which stores hydraulic fluid or gas under pressure for future release. Used as an energy source or to absorb hydraulic shock. Designed to increase or relieve pressure in the hydraulic system. Common types of hydraulic accumulator are: piston, bladder and diaphragm. Click here for more information on hydraulic accumulators.

The ability of the system to achieve the desired output.

A device in which power is transferred from one pressurized medium to another without intensification; the hydraulic components such as hydraulic cylinders, hydraulic motors and hydraulic rotary actuators that directly help convert hydraulic energy into mechanical energy.

A device used to align the shaft of a rotary device (e.g. and electric motor) with the shaft of a hydraulic pump to maintain radial and parallel shaft alignment. Fittings can vary in size and material to change an end fitting from one type or size to another.

A chemical added to a hydraulic fluid to impart new properties or to enhance those which already exist.

Air trapped in the hydraulic fluid. Excessive aeration causes the hydraulic fluid to appear milky and can lead to erratic systems performance. See our article on air contamination in hydraulic systems.

A device (either manual or automatic) for the removal of air trapped in the pipeline.

A device permitting air movement between the atmosphere and the hydraulic component in which it is installed, containing a fine mesh filter element to prevent contaminants from entering the hydraulic component. Normally attached to the top of a reservoir or tank to allow air to pass in and out.

Air at any pressure greater than atmospheric pressure.

The ambient atmosphere forced or trapped into the hydraulic system during connection of quick-release coupling halves.

A hydraulic component in a hydraulic system that relieves excessive heat with cool air.

A hydraulic component used to store hydraulic fluid. The air-operated accumulator increases and relieves hydraulic pressure through the use of an inflatable bag. Also called a gas-loaded accumulator.

A hydraulic component that is powered by compressed air. Compressed air exerts force on a piston, which magnifies pressure as the hydraulic fluid escapes to smaller conductors and actuators.

Of or relating to the immediate surroundings. The current condition of temperature, humidity and atmospheric pressure.

The noise level in the surrounding area while the machine or component concerned is not operating. Background noise.

An electronic device used to increase the strength of the signal or input voltage fed into it to modify the signal into a driving voltage or current at a different level.

The magnitude or volume of sound.

An electronic device that requires or produces an infinitely variable signal (voltage or current) in response to a state change within the device.

An AC or DC voltage or current signal that represents continuously variable physical quantities (e.g., voltage, current, pressure, temperature, or speed). Any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e. analogous to another time varying signal.

One of two types of additives used to reduce foaming in petroleum products.

A ring shaped area, often referring to the net effective area of the rod slide of a cylinder piston, i.e. the piston area of the rod.

An electrolytic process used to increase the thickness of the natural oxide layer on the surface of metal parts; to deposit protective or cosmetic coatings in a variety of colours on metal. Primarily used on aluminium.

Microscopic projections on metal surfaces resulting from normal surface-finishing processes.

The weight of the atmosphere. Atmospheric pressure refers to the amount of pressure exerted by the air at any specific location. Sea level pressure is approximately 14.7 pounds per square inch (psi) which equates to 1.01 bar.

The gradual loss in intensity of any kind of flux (current) through a medium.

A variable resistive device used to reduce current or voltage.

Testimonial: Rayne Precision Engineering

I have passed your cards onto a couple of our maintenance contractors and have given you a high recommendation to them both, so hopefully they too will be using in the future. Thanks for helping to get our repair solved so promptly.

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Testimonial: Engineering Solutions

The valve arrived about 9:00am this morning. The service from you and Steve has been first class, so thank you very much. I shall certainly use your services again and recommend you to others. Thanks again and best regards.

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Testimonial: Philippines

We would like to confirm receipt of your shipment for our initial order: PO# 07623. It was a pleasure having started working with you and we hope this is just the start of a good business relationship between our companies. Again, thank you very much and we look forward for more future business opportunities with you.

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Testimonial: The Netherlands

Thank you for your service with selecting the proper pump. Pumps have arrived this morning and they completely conform with the old pumps.

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Testimonial: Abernethy Trust

Please pass on my thanks to Steven for great customer service and his product knowledge; our gang mowers are back up and working.

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Testimonial: Virginia

Please thank your team very much in helping me solve a pump issue. I needed a pump that was manufactured by a company no longer in business, and Steven was able to locate a duplicate that was manufactured by Parker.

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Testimonial: Gwynedd

Thank you, Joanna. Mark’s quote was from a technical discussion which answered many questions that I have been trying to get without success from other suppliers. Please thank Mark for his time and expertise; it was so refreshing to have a knowledgeable person rather than a sales assistant.

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Just wanted to tell you that the pump fits and works perfectly. You were a big help, thank you.

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Testimonial: Lift Company

Hi Mark, Thanks for sorting this out for me so quickly. Absolutely brilliant service… In this day and age it is so rare to come across a company with customer service to this level. Much appreciated.

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Testimonial – Perth

Can you let the boys know that they are providing us with great service, parts and information in all our locations. Your service is prompt and reliable; you’re our “go to” guys when it comes to hydraulics.

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Multi award-winning Alsager firm Hydraulics Online is gearing up for more success this year having recently been shortlisted as a [...] Read More
New Monday, new week, new website! Today is the day we are launching our fresh and updated online experience. We’re [...] Read More
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It’s official! We’ve got the vision! Hydraulics Online Co-founder, Helen Tonks has been shortlisted in the 2018 Enterprise Vision Awards […]

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As their North West Business Exporter of the Year, the Federation of Small Businesses asked Hydraulics Online to speak at the 2018 […]

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Hydraulics Online founders Mark and Helen recently had one of their most exciting interviews to date – with the radio […]

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We did it again! Hydraulics Online is delighted to announce that we have been recognised as the North West Business Exporter […]

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Mark’s entry into the fluid power industry was more than a little by chance but he now finds himself leading a […]

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