No announcement yet.

adding a Knuckle valve to a 47 blower truckmount

  • Time
  • Show
Clear All
new posts

  • adding a Knuckle valve to a 47 blower truckmount

    Question: What size holes do I drill in the 2" PVC cap for the knuckle valve if I have a 47 two lobe blower and how many holes do I drill. I guess I'm looking for size holes to drill and how many do I drill

    Answer: I really do not know, but here are the instruction on where to start:
    The 45 blower uses: "Cap is drilled with four 5/16" holes plus on 13/32" hole in center when used with a 45 truckmount blower. Adjust hole sizes based on cfm rating of your blower."
    I have not had any local customers ask us for this installation so I have not had to play with these numbers yet.
    Here is what we do know: Performance curve for the 45 blower is located at[1].pdf
    The performance curve for the 47 blower is located at

    We want to look at the cfm at 14" HG of lift, at 3400 rpm on the 'vacuum curve' chart of each blower.
    47 blower is 425 cfm and 45 blower is 325 cfm.
    This is about 31% more cfm so I would start off with one extra 5/16" hole. Install and test. If vacuum is going over 14 Hg, I would upgrade each hole one at a time from 5/16" to 3/8" until the vacuum falls back to 14". Test between each time you upgrade each hole from 5/16" to 3/8".
    Please let me know what you find out for your machine. The other issue is some customer still leave the original vacuum relieve system installed but just tighten it up and it still might be opening at the upper vacuum levels so each machine could be different.