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Moog servo valve repair service ¦ Moog proportional valve repair service

Over 25 years experience of fast Moog servo valve and moog proportional valve repair

We have been repairing Moog Servo and Proportional valves for over 25 years. Over this period we have achieved an average turnaround of 2 days. In the thousands of repairs we have carried out, we have declared less than five of these as ‘unrepairable.’ There is NO OTHER UK servo repair company that can come anywhere near to this level of service. We do not even charge a premium for ‘while you wait’ or ‘out-of-hours’ repairs.

What will we do to your Moog proportional or servo valve?

Typically, the initial inspection of a Moog valve's condition shows the level of work required. For example, if the valve is very clean with no visual contamination of the pilot filter and all ‘O’ rings are in excellent condition the valve may not require a full strip and clean. This however is very rare, and virtually all valves sent to us are subjected to a full strip and clean. Note: we also fully strip the pilot stage, which some company's charge extra for. Unlike other repairers, our technicians have application experience that enables us to understand what the valve does on your machine. In some instances our understanding of the application allows us to relax any specifications that we know are not critical. This avoids the replacement of parts that have no effect on the performance of your system. One example is the increased internal leakage over a slightly worn spool. In some applications this particular specification may not be critical, so there would be no need to replace the spool.

‘Viton’ ‘O’ rings for much better temperature rating and free advice

All tests are carried out to the original manufacturers published specifications. Our Moog servo and Moog proportional valve spare parts meet or exceed original manufacturers specifications. Many Moog proportional and servo valves sent to us have been damaged by excessive heat, and therefore we fit ‘Viton’ ‘O’ rings wherever possible as these have a much better temperature rating. In the event we discover that oil temperature was the cause of the problem we always advise you so that action can be taken to prevent a reoccurrence. We do not just repair valves, we try to help you improve your machines reliability. If you have already sent us valves for repair it is very likely you will have experienced the advice we give on contamination control, valve sizing etc...

Direct drive servo valves - More tolerant to dirt

We recommend the latest ‘Direct Drive servo valves’ for all new applications as they are more accurate and much more tolerant to dirt than traditional designs. Our test rigs have recently been equipped with facilities for testing these new types of valve. High performance servo valves for high performance applications. We take great care to ensure this type of valve is tested to meet the original manufacturers specification.

Size ‘3’ and ‘5’ valves

Size ‘3’ and ‘5’ valves are the mainstay of our valve repair service. We also stock many versions of this series. Based on the original nozzle-flapper pilot stagethese valves are used on machinery all over the world.

High flow multi-stage proportional valves

We repair high flow multi-stage proportional valves. Pilot stages are stripped, cleaned and recalibrated. Integral loop closing electronics repaired.

Things to keep in mind when having servo and proportional valves repaired

1. Recurring Damage: A servo valve may be blocked with dirt or damaged by excessive heat. Unless you have done something to prevent this from happening again (changed system filter element and used a ’flushing plate’) then you risk doing the same to the repaired servo valve. Please bear this in mind should you phone and say "you repaired this valve and it only lasted five minutes”
2. Shipping Damage: Servo valves shipped for repair to BMC may arrived damaged because they may fall out of an oil compromised box during shipping. You must fit a cover plate on the valve otherwise the internal oil may make the shipping box soggy. Shipper will state your soggy packing is not covered by their insurance. Remember a replacement valve can cost £1300 - £3500 quite painful if deducted from your personal salary by management.
3. Oil Damage: All servo valves need clean oil. Some are a little less dirt sensitive than others, but if you do not replace the machines filters when they indicate blocked then you will have problems with servo valves failure.
4. Heat Damage: Many servo valves sent to us have been damaged by heat. We know this because the oil in the valve is dark brown and smelly. When we remove the rock hard ‘O’ rings from the valve we often think "Wow - every bit of rubber that the hot oil came into contact with is damaged (hoses, cylinder seals, pump seals everything! Wow
5. Moog valves come in dozens of different flow rates. Generally low flow goes on a very small machine and high flow on big ones. Its not always obvious if you have fitted the wrong flow rate, but it may cause a slight reduction in repeatability. Don’t hesitate to ask our advice on this.

Reasons for servo valve failure/faults

In blow moulding, the commonest cause of servo valve failure is HEAT.

Possible reasons are:

• the hydraulic cooling water was shut off
• the valve sat “cooking” on the head with the “heats” on, and the hydraulic supply turned off. The oil inside the servo valve turns to a thick gummy mess, and the servo valve cannot operate.
• additionally heat turns the “O” rings brittle and the servo valve will then leak.

Hydraulic filtration is also important and we recommend that the pressure line filter element is changed at least once a year.

Always ‘cap off’ hose ends and open ports when performing head changes.

Reasons for proportional valve failure/faults

Most machines have a separate filter in the pressure supply to the pilot stage of the proportional valve. It is very important that the filter element is changed whenever the dirt indicator switch is energised. This is particularly true with older valves that were of a more dirt sensitive design.

Unlike servo valves which are virtually always have a ‘closed centre’ ‘zero dead-band’ characteristic, there are numerous different types of proportional valves.

Cllick here for Rexroth servo valves repair and service.

Cllick here for Rexroth servo valves repair and service.

Phone 01242 604040
Fax: 01242– 603987
Email: robin@bmc-controls.co.uk
Blow Moulding Controls Limited