Bag infusion + Lite RTM : Plumbed vacuum system?

Discussion in 'Fiberglass and Composite Boat Building' started by KD8NPB, Mar 28, 2018.

  1. KD8NPB
    Joined: Mar 2018
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    Location: South Carolina

    KD8NPB Junior Member

    I've been tasked with converting a 28 ft hull which is currently hand laid, to bag infusion instead on an industrial basis. I have been finding widely conflicting information regarding the vacuum system...I'd like to bite the bullet, and just use a plumbed system rather than individual pumps which will likely get broken / neglected by the operators.

    • Is there a formula to calculate vacuum pump cfm based on the hull size?
    • Is it okay for me to run a 100% duty cycle rated reciprocating vacuum pump (IR Type 30 V-pump w/ 120gal tank), or should I investigate plunking down for a proper rotary screw vacuum pump?

    We are also looking to add lite RTM to our lineup this year as well, so if it is a plumbed vacuum system that can be used for RTM and bag infusion simultaneously, that would be fantastic.
     
  2. jorgepease
    Joined: Feb 2012
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    jorgepease Senior Member

    I bought two Welch pumps off Ebay for $600 each. Normally they run about $3000. CFM is not really that important, you want a pump that is continuous duty and can pull to full vacuum. The Welch pumps purr quietly and are extremely heavy duty.
     
  3. Steve W
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    Location: Duluth, Minnesota

    Steve W Senior Member

    What model pumps did you buy Jorge? Are these what you have been using all along? Just curious as to what others are using. To the OP I would suggest you visit the Vacmobile site, it gives a lot of info on pump selection. Basically they suggest mobile pumps rather than a large central system. While theoretically you don't need high cfm a pump with higher cfm will evacuate a larger bag much quicker. Another important thing to look for,for any kind of bagging operation is a pump that can handle rough vacuum well, such as a leaky bag. Sometimes on a complicated bag you can spend a lot of time chasing leaks before you can pass a drop test. Most industrial rotary vane pumps will handle this situation well, the little pumps used for refrigeration evacuation, not so much and spit out oil and vapors under rough vacuum. I like Jorge, bought my pump off ebay, in my case a NOS Busch R5 RC0025 which was one of the pumps recommended by Vacmobiles.
     
  4. jorgepease
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    jorgepease Senior Member

    Steve, I bought the 1397 which is a beautiful pump and quickly draws down any bag at 17 cfm and the much smaller 1402 duoseal which is a little less than 6 cfm and which is what I did all my infusing with. These are industrial pumps which are routinely are run for months and years without stopping. You can feel confident buying used because at worst, the electric motor needs replacing or the pump needs rebuilt which you can do yourself with a rebuild kit.

    The vacmobile is nice because its well thought out with their quick release connections and overflow tank with liner, sure beats an old pvc pipe. I will prob go that route and the next build but in all reality, it's not necessary.
     
  5. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Thanks Jorge, That's a good size pump at 17cfm, I think my Big pump is around 20cfm and it draws down, obviously much better than the 6cfm Robinair we use as a backup. I would like to replace the Robinair with another industrial pump as a backup. I don't have a Vacmobile but we do have a homebuilt equivalent which a friend with a machine shop built. To be honest it is not necessary but he had a big stainless steel pressure pot he was not using so installed 6 ports ,a thick glass viewing window in the top and a manifold. we can fit a 5 gallon bucket with a couple of the top rings cut off inside as a disposable catchpot. its a really nice unit but really overkill. We have the spare pump plumbed into the catch pot ready to go and if I were doing a big job I would also have the generator ready to go also. So, I am on the prowl for a second industrial pump, a friend has a german Rietschle pump that he bought many years ago when the Elite (Jeuneau) plant in Annapolis closed down and he was working there at the time. I don't think he has used it in 20 years so I'm going to see if he will sell it to me on the understanding that he can use it if he needed it which is not very likely.
     
  6. jorgepease
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    jorgepease Senior Member

    I should build one since I still have the fittings I bought from them ))
    vacfitngs.jpg
     
  7. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    Those are some nice fittings, mine came from Mcmaster Carr i think and are actually made as bulkhead fittings for electrical cables, we always check everything with the sniffer and have never had any leaks in the "bong". What is the thread on those?
     
  8. KD8NPB
    Joined: Mar 2018
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    Location: South Carolina

    KD8NPB Junior Member

    I like the vacmobile setup, but it is not really an industrial setup. There's a lot of potential for damage to pumps and equipment.

    My tentative plan:
    IR V255 reciprocating vacuum pump [100% duty cycle rated] = 60 cfm @ 29 inhg.
    80 gal reservoir @ full vacuum
    plumbed system with 2" steel pipe with many QD fittings near bag infusion station

    At RTM station:
    Regulator w/ 80 gal reservoir @ partial vacuum
     

  9. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    I'm not sure that its not an industrial setup, its just a more versatile setup. Multiple appropriate sized industrial pumps on wheels would be very versatile and be able to handle any size shop with better redundancy. That said we have a large Quincy compressor plumbed through about half of the shop at work but it is a lot less critical as if there is a leak its not a huge deal. My Busch pump is 20 cfm and a very reliable industrial pump and I could see having a few similar pumps if I were running a big shop. As it is I always have a second pump plumbed into the catch pot ready to take over if the primary pump were to fail and a generator on stand by should we have a power outage during an infusion. Neither has ever happened but I like to be as prepared as possible.
     
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