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flange union bolt torque

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rtv
rtv Member Posts: 73
I'm replacing a gasket on a flange union (3" pipe, 4 bolt, 1/8" buna gasket)
finding all sorts of torque values on the web. from 35 to 110 ft lbs. anyone know what is correct? Thanks!

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  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 2,020
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    FWIW, I have installed these unions without any gasket at all. Fill the grooves with dope and tightened until it was nice and snug. I have gone back many years later and all is still doing well. Horizontal pipes, gasket has a nasty habit of moving out of place. Even when glued or caulked into place.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,732
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    I wouldn't worry about torque. Just snug it up tight. But not too tight they are made of Cast Iron. I would say as tight as you can get it with an 8" adjustable should do it.
  • Big Ed_4
    Big Ed_4 Member Posts: 2,818
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    You will need to torque it down again after the bolts stretch from the heat expansion .

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