SafeBoilerRoom

The tightening of a bolt flange connection is a relatively simple operation, but certain practices must be followed to get a leakproof connection. In boiler rooms across the state, we've seen costly pipe and valve replacements caused by water and steam cuts that could have been avoided if the flange had been assembled correctly.

To ensure that your bolt flange connection is assembled correctly, follow these nine steps:

1. Select the right gasket size and material for the connection.
2. Ensure that the gasket lines up evenly with the inside bore of the flange face with no portion of it extending into the bore.
3. Use properly sized bolts in the assembly. Boiler inspectors tell us that they often find pipe flanges that don't meet code or engineering requirements because the bolts aren't long enough.
4. Keep the flange faces parallel by tightening the bolts uniformly. Don't work through the bolts in a circular pattern. By the time you reach the last few bolts, the flange will be out of parallel.
5. Depending on the bolt hole arrangement, follow the numbered tightening sequence shown in the diagram above.
6. Start with bolt #1 then move to bolt #2, then #3, and so on. Complete the sequence, but only partially tighten the bolts.
7. Do not snug up the bolts on the first go around. This can tilt the flanges out of parallel. If using an impact wrench, set the wrench at about 1/2 final torque for first go around.
8. On the second go around, tighten the bolts in the same sequence. Pay particular attention to hard-to-reach bolts to ensure that the flanges are not tilting out of parallel.
9. A third go around may be required.

This procedure should help extend the service life of your flanges by reducing or eliminating steam and water cuts. We hope this information helps you. If have questions about installing the pipes, pumps, or valves you've purchased from us, give us a call. We're able and willing to help you. (919) 832-1665