If you’ve been following my posts here and in other places for any length of time you’ll be aware that I’m a loud and enthusiastic advocate of NOT installing suction strainers, and in the majority of applications, removing and discarding them when they are installed.
Which is why I’m always interested in any new information on this issue, especially if it’s anything ‘official’ from a pump manufacturer. On this note, recently brought to my attention by one of our members, is the data sheet for Nachi piston and vane pumps, in which Nachi does recommend the installation of a suction strainer.
The people at Nachi obviously haven’t read my books Insider Secrets to Hydraulics and Preventing Hydraulic Failures, although to be fair, neither has been translated into Japanese at this point in time. Seriously though, to the best of my knowledge, Nachi is in a minority of pump manufacturers who actually recommend the use of a suction strainer.
Contrast Nachi’s recommendation, with Bosch Rexroth’s. The data sheet for their SV series variable vane pumps states: “Bosch Rexroth does not recommend the use of inlet suction strainers.”
That’s one for and one against. Here’s another, Eaton-Vickers, sitting on the fence, from their Mobile Hydraulics Manual, (2010) p.388:
“[Reservoir] Outlet line strainers, also called [pump] inlet filters or inlet screens are very common. This may be more traditional than functional… They are intended to keep larger solid contaminants from entering the hydraulic system. A drawback is that they are quite inaccessible for service and cleaning. If they become restricted due to excess contamination, they can cause cavitation and damage to system pumps. A more current approach is to ensure clean fluid is maintained in the reservoir, precluding the need for an outlet line strainer.”
It seems Eaton want you to make up your own mind. But at least they acknowledge that the tradition of always installing of a suction strainer is outdated. Then there’s this from Stauff, a company that does not manufacture pumps, but does make suction strainers:
“WARNING: It is advisable to check with the pump manufacturer before any type of filter is fitted to the pump inlet line… In general, suction strainers do not contribute to system cleanliness. The difficulty associated with changing strainers, and knowing if and when they are clogged [may result in pump damage].”
So if you take Stauff’s advice and check with the pump manufacturer, one says ‘yes’, another says ‘no’ and a third says ‘you decide’. For anyone who seeks ‘black and white’; who can’t cope with ‘gray’, this issue could drive you quietly mad.
The fact of the matter is, in the majority of hydraulic applications, installing a suction strainer is a mistake. And to discover six other costly mistakes you want to be sure to avoid with your hydraulic equipment, get “Six Costly Mistakes Most Hydraulics Users Make… And How You Can Avoid Them!” available for FREE download here.
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