Why Two Filters Upstream of Servo Valve?

Maybe the filters reduce the flow too much, so two were needed in parallel to get the required flow.
Maybe someone just forgot to close one?
The flow will split between the valves depending on how clogged they become, but one would expect it to be similar.
Del

In a setup of this kind, only one of the filters should be in operation at a time. If one filter is thought to be plugged (either by pressure gauges that show this or by some predetermined time interval), switch to the second and replace the first.

If you leave both filters in line, and one of them plugs up, than chances are that other is plugged up as well. That is why both shouldn't be run at once.

To provide a means of replacing the filters with out stopping the operations the hydraulic fluid is providing. So the filters can be changed. It maybe that in a change of filters someone left both on. The filters should have been selected to handle the volume of oil so there should be no need to used both at he same time.

This someone may have thought to cut down the intervals in which he would have to check and change the filters. Instead of say changing one every month changing both every two months.

IF they have a replacement indicator (e.g., the little red button or some such thing), that allows you to replace the clogged one without shutting down. This is known locally as the TVP45 system of preventive maintenance - wait till it clatters, then service it. The reason for leaving both open is so you don't starve the valve when one filter clogs. Now, you must pray and hope you check these often enough that both don't clog.

Notwithstanding comments by others that are all relevant, it just shows how critical it is to supply your servo valve with VERY clean oil. A typical problem that servo valves can have is a balance jet blocked by a small amount of debris (commonly rubber internal lining of flexible hose) that will result in a 'hard over' situation with possible dire consequences!

You should also be aware that the servo valve itself will probably have either one, two or even three very small disc filters about the size of a small coin (found inside the body of the valve) that should be checked if ever a filtration problem is discovered.

Good luck with it!

I completely agree with u. But don't u think one filter to the upstream of servo valve would have done its job of supplying fluid of required cleanliness level. And if is it like, two filters are provided because even if one gets clogged other filter may open and hence the fluid will not reach servo valve without filtration, then why is that both the shut off valve are kept in open position initially ?

I think that the reason to install two filters in your system is due to the OEM quite correctly fitting units with no bypass check in the filter body however, I would have expected to have found a differential pressure gauge fitted so that the filter elements themselves could be monitored. I would assume that the first filter would be changed on a fairly regular time frame and the second filter would be just for insurance (bib and brace). However, this would require the filters to be mounted in series. In parallel it would be more logical to have one filter 'live' at any given time and with the aid of the isolation valves, a filter could be changed while the system was operating

As yet, you have not informed this forum of what onerous task that the servo valve performs and what, if any, are the consequences of 'failure mode'. A 'hard over' failure of the servo valve resulting in an un-commanded motion could, maybe, possibly cause injury or DEATH!

Remember that replacement filter elements are cheap and as you already have two of the expensive filter body/housings, it seems unwise to compromise the system on a cost saving basis!

It is a routine thing now to tag the valves with an ident number. Why suppliers can't add basic maintenance in clear language is beyond my ken. We recently had a 6ton batch of conc sulphuric acid dumped because of a valve not closed before another was opened. A label would have saved a dangerous discharge. Likewise your situation would be much clearer if the filters had a simple plate saying 'Both to be in use' or 'One only in normal service' OEM's provide (sometimes) O&M Manuals that are too precious for fitters to see. They are kept in an office and gather dust.

One is a spare that should have been valved off. A setup such as this is common in many filter applications so you can block in a dirty filter and change it out without a system shutdown

two filters parallel to each other, both inline at a time means the single filter flow capacity may not be suffiecint to the servo valve. If single filter flow capacity is sufficient, the second filter must be a standby. There must be communication gap between the designer and the commissioning engineer.

Good day. I essentially agree with those who suggested that the flow through one of the filters should normally be blocked off and the valves provide a means of changing over to the un-used filter when the other becomes clogged. Obviously some means of evaluating the filter condition while operational would be required as previously suggested. It is not clear whether there are dedicated shut off valves fitted both upstream and downstream of each of the filters. If there are not it is a strange set-up, as this would be a necessity in order to do a filter swap while your equipment is running. WR