Does the best tool change-over procedure involve servo-valve removal?

  1. Firstly, keep the servo-valve on the parison programming cylinder. If the tool change also involves a head change (Single to Twin, PE to PVC for example) then you do need to take some precautions. The only justification in removing the servo-valves is to avoid inadvertently damaging the valve.
  2. Disconnect the pressure and tank hoses.
  3. Plug up the open ports on the valve block.
  4. Plug up the open hose ends.
  5. Do the head change.

The goal here is not to introduce dirt into the hydraulic system. Some servo-valves are more dirt sensitive than others, do not believe the valve manufacturers claims. Moog 76 or 760 series are more sensitive than Moog 62 or 631 series.

If carefully done, you will not have problems.