At High pressure HUNTER pgp's _________

Discussion in 'Irrigation' started by CAPT Stream Rotar, Jun 19, 2013.

  1. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,412

    I sure don't love systems with high pressure losses in the field plumbing. I can get surprised by 'extra' well capacity, when the time isn't there to spend hours on a flow test, and I instead follow the lead of the existing zone plumbing.

    One renovation turned into a Jekyll and Hyde system, as the well had more flow than existing zones were using, and I had to bring up the pressure switch settings to prevent cycling, so the zone nearest the supply runs like gangbusters at 60+ psi, and the one fed by 200 feet of one-inch poly is closer to 30 psi.
     
  2. Kiril

    Kiril LawnSite Fanatic
    Posts: 18,308

    Ahhhhhh, the booty special. :p
     
  3. HunterTekGeek

    HunterTekGeek LawnSite Member
    Posts: 242

    The PGP rotors are built to withstand operating pressure of up to 100 PSI without blowing apart, but there can be other external factors that create problems. For instance, if there are slopes or even slight elevation changes, then the lateral pipes drain out. So when the zone first starts there’s an excessive amount of water flowing through the empty pipes at a high velocity. When that water stops, sometimes it can blow off nozzle turrets or break body caps. To help prevent the low head drainage and start up damage, install drain check valves in the PGPs which hold back about 3-4’ of elevation change, or better yet, install the I-20 that comes with a stronger spring and check valve that holds back 10’ of elevation change.

    As for the nozzles themselves, they are designed to operate most efficiently at 40-50 PSI. If the pressure is higher, the water droplets are smaller and more misting and drifting will occur. And, if the nozzles are diffused to reduce the radius, that too may cause additional misting. How do you accurately check the dynamic pressure? Use a pitot tube shown below. Simply place the very small tube directly into the center hole of the nozzle and read the gauge. More importantly how do you reduce the pressure if it’s too high? One possible way is to turn down the flow control on the valve, then recheck the pressure.

    The leaking may be from caused from an old, deteriorated, hardened riser seal. That seal not only seals on the outside of riser that pops up, but it also seals against the inside of the body. Once the seal is old, it can shrink in size and harden, then it no longer is flexible enough to seal on the body, so water leaks below the cap. To return the sprinkler to nearly new condition, simply replace the riser seal and reinstall the head. For more information see the information below.

    http://www.hunterindustries.com/sup...m-there-something-i-can-replace-or-repair-fix

    Pitot Tube.jpg
     
  4. irritation

    irritation LawnSite Gold Member
    Posts: 3,225

    Bull crap, this has been going on for years. It's not that simple to replace the riser seal, it's easier to replace the head with a 5004.
     
  5. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,918

    If everyone would use 6" heads and learn to install them to the proper grade, I'd bet we'd see fewer problems with wiper seals.
     
  6. irritation

    irritation LawnSite Gold Member
    Posts: 3,225

    That would make no difference with PGP's. I've seen them leak no matter the circumstances.
     
  7. Mike Leary

    Mike Leary LawnSite Fanatic
    Posts: 21,918

    I know Boots thinks the guts are the same, but in 12 years, I've had zero problems with I-20 stainless 6".
     
  8. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,412

    Hunter always had a burden with the PGP seals. The head could use such tiny nozzles that flow-by had to be equally tiny. And of course, the best wiper seal is patented by their competitor.
     
  9. irritation

    irritation LawnSite Gold Member
    Posts: 3,225

    I used them for years with no problems. I think the rubber or plastic or both was changed at some point and ruined the head.
     
  10. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 47,412

    the seals were a headache through most of the PGP's first few years - not until the later 1980's did they come up with something workable
     

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