Gate valve installation: orientation, flanges, bolting and start-up
Most complaints about leaking gate valves come from installation rather than manufacturing: misaligned flanges, debris on the seats or the wrong stem orientation. These errors are easy to prevent. This is the sequence for flanged gate valves.
TAZ Engineering Team · · 7 min
Before installation
Check the marking and datasheet against the design: DN, PN, material, temperature and flange drilling. Inspect the body, handwheel and flange faces, and operate the valve through its full stroke by hand. Remove end protectors only immediately before installation. Store and install according to the manufacturer’s manual; resilient-seated valves are often kept slightly open so the rubber does not take a set.
Orientation
The preferred position is stem vertical and upwards on a horizontal pipe, with tilt allowed down to a horizontal stem. Stem-down installation is not recommended because dirt and condensate collect in the bonnet. Wedge gate valves are normally bidirectional; if the body carries a flow arrow, for example because of a pressure-relief hole in the wedge, follow it.
Flanges, gaskets and bolts
Pipe flanges must be aligned and parallel; never pull misalignment together with bolts, as this loads the body and distorts the seats. Choose the gasket for the medium, pressure and temperature and centre it. Tighten bolts in a cross pattern over several passes up to the torque calculated for the gasket and bolting, using a torque wrench on large sizes.
Supports and loads
The valve must not carry pipe weight. Support the body on DN 300 and larger, especially with electric actuators, and take thermal expansion with expansion joints rather than through the valve.
Flushing, testing and start-up
Flush the line with the valve fully open so scale and weld spatter do not reach the seats. System test pressure across a closed valve must not exceed the valve rating. Operate the valve gently at first, and if the gland weeps after the first heat-up, tighten the gland nuts evenly by a small amount.
Checklist
- marking and datasheet check
- full-stroke check
- flange alignment
- stem orientation
- flow arrow
- gasket selection
- cross-pattern bolting
- body support
- flush with valve open
- gland adjustment after heat-up