Category: Troubleshooting the press
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Vacuum pressure on a Heidelberg Platen

We’re trying to get our Heidelberg dialed in and having a tough time with it. Our hypothesis is that the pump is creating too much vacuum - we put a gauge on it and measured 21 psi of vacuum. Online we found references to 7psi being the spec - but we can’t find anything official so two questions:
1) does anyone know for sure the vacuum pressure that it should run at
2) if it’s NOT 21psi - anyone have any theories for why it would be that high. We have checked and cleaned the dump valve and there’s no junk in it and it works fine on the bench.

Thanks in advance.

Log in to reply   7 replies so far

  • ericm
  • on 24 Sep 26 (08:53)

By “Heidelberg Platen” i assume you mean one of the “Windmills”? If so, can you open some of the unused pickup suckers to knock down the vacuum? BTW, do you mean 21 In/hg? Vacuum is not normally measured in PSI.

Don’t forget the clip on the sucker bar that covers a control hole to reduce the suction. Also paper pick up is not only suction, but table height, the amount of blow going into the top of the pile and last the sucker tilt which all combined makes for ¹a smooth running feed.

  • bppayne
  • on 24 Sep 26 (19:02)
  • Updated 25 Sep 26 (06:21)

Besides the clip on the sucker bar, there are ‘sucker bar slides’ which have smaller holes that reduce vacuum. There is a pink bar for onionskin, another red bar for light weight papers, and a yellow bar for heavier papers. See page 65 in your operating manual. Look for ‘Sucker Bar Slides’. Per Franks comment, you may need to reduce the amount of blow, and increase tilt.

I did mean 21psi. The gauge we have measures PSI. All the specs I’ve found say 15in/Hg which I converted to 7.5psi based on a table I found online.

We’ve manipulated all the “holes” we could find to try to reduce the vacuum - but I’m not sure if we found the “sucker bar slides”.

Something to investigate…thanks.

  • ericm
  • on 26 Sep 26 (20:08)

Wow! Ok, 21psi is 42in/hg. That is an incredible amount of vacuum for that old pump.

Here’s a thought I have bleeder valves on my verticals to trim the suction.best james

NA Graphics and printerspartsusa.com has the red slide for sale.
You can also bleed off suction and overall air pressure on the pump itself. There’s a knob near the top, try backing it off a partial turn.