FAQs: Hydraulic filters
1 June 2010
What are duplex filters and why should I consider using them?
According to a Donaldson Filtration Solutions spokesperson, “Because they are so convenient. One can accomplish filter change-out without having to shut the system down.”
The swap-out procedure is as follows:
1. Divert the flow from filter A to filter B.
2. Change filter A.
3. Then reconnect the flow to A.
Typically, a valve is required for duplexing two filters. For three or more filters, a manifold and two valves are normally required.
Donaldson’s HMK series Duramaxo filters are particularly well-suited to duplexing because, despite them being spin-ons, they can still handle high pressures.
Should I use synthetic or cellulose filter media?
While cellulose is appropriate for some applications, synthetic media typically offers the lower differential pressure, higher temperature resistance, and longer shelf life.
Synthetic filters can also be used with a greater variety of fluids and are more chemically stable.
Cellulose elements are usually less expensive, but will probably have to be changed out more often.
What is the difference between 'static' pressure and 'working' pressure?
Static pressure is the maximum rated pressure that the filter assembly can handle before it bursts apart.
Working pressure is the reasonable pressure the filter can handle for a sustained length of time under controlled cycle fatigue conditions.
What factors do I need in order to calculate filter size?
Flow rates, pressures, and the type of oil used.
For more information contact Taryn Ternent, Donaldson Filtration Systems, +27 (0)11 997 6078, marketing.sa@donaldson.com, www.donaldson.co.za
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