Design Engineering

Get What You Spec’d

By Pat Jones, P.Eng   

Fluid Power commentary hydraulics maintenance

Following a few simple procedures will ensure you get the hydraulic system you paid for.

The silver lining of an economic slowdown is that it gives us an opportunity to focus on areas that will affect the bottom line; when things turn around, we can move ahead as cost effectively as possible. When it comes to hydraulic systems, however, known practices proven to increase hydraulic system reliability are too often short-circuited to cut up-front costs. A lot of times, hydraulic systems arrive as part of a bigger machine and, although the specifications for the machine operation have been met, the design/maintenance aspects of the hydraulics are left up to the equipment supplier.

In my experience, very few end-user companies have a document that clearly defines how they deal with their fluid power systems. The fact is, if you don’t have in-house standards in place to insure the equipment you purchase is properly built, you are exposing yourself to unnecessary cost in the short and long term. The following practices/procedures will guarantee that new purchases start out and continue to be reliable.


Establish a minimum ‘roll-off’ cleanliness
Everyone who deals with hydraulic systems knows contamination is still the No. 1 cause of component/systems failures. This problem can be handled effectively by selecting a hydraulic system cleanliness level that must be achieved by suppliers of your equipment. Add a statement to the purchase order such as “Before delivery of a hydraulic system, the manufacturer must demonstrate an ISO cleanliness level of 18/16/14 for any system and 16/14/12 for servo and proportionally controlled equipment.”

In addition, verify your request has been met with oil analysis documentation as part of factory acceptance testing and also during on-site commissioning and final acceptance.
Simply specifying a “roll-off” cleanliness (as in “off the end of the production line”) as part of the delivery requirement will insure all necessary preventive measures were used in assembly and commissioning.

System specs
Most end users don’t specify the type of components/system they prefer. Purchase specifications should clearly spell out desired and unacceptable features/practices. Some features that are standard within some industries and should be included in the spec of production hydraulic systems are:

•  Flooded pump inlets (pumps mounted below fluid level): This insures the pump is in the best possible location to receive fluid and eliminates most priming issues on start up.


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