Orientation, support and accessibility for industrial valves

Gate valves and globe valves can generally be installed in any stem orientation: horizontal pipe with stem horizontal or vertical, or vertical pipe with stem in any direction. However, a horizontal stem (stem pointing sideways) in a large gate valve means the weight of the gate hangs on one side of the stem, accelerating stem wear and making the valve harder to operate over time. Vertical stem-up is preferred wherever possible for large-bore gate valves.

Avoid stem-down orientation for gate valves where sediment can accumulate in the bonnet: the stem packing gland becomes contaminated and the stem thread corrodes if moisture or process fluid reaches it. Stem-down butterfly valves collect debris at the bottom of the disc pivot, accelerating wear. Check the manufacturer's installation guidance for the specific product.

Check valves have strict orientation requirements. Swing check valves must be installed in horizontal pipework or in vertical pipework with upward flow. Installing a swing check in downward vertical flow will not work — gravity holds the disc open and backflow is not checked. Silent (spring-loaded) check valves can be installed in any orientation including vertical downflow.

Valves are heavier than the equivalent length of pipe, and large valves with actuators are substantially heavier. The pipe flanges are not designed to carry the bending moment of an unsupported heavy valve: supporting the valve from the pipe alone will crack flanges, deform flange faces and introduce unacceptable stress into the pipe.

All valves above approximately DN200 and all actuated valves regardless of size should be independently supported from the structure. The support should carry the valve weight without relying on the pipe flanges for vertical load, and should allow the pipe flanges to be disconnected and the valve removed without the support collapsing or the pipe moving excessively.

For outdoor or elevated installations, wind load on large actuators must be included in the support design. A top-mounted electric actuator on a large butterfly valve presents a significant sail area and lateral load in strong wind.

Every valve that will be operated by hand requires clear space for the operator and the handwheel or lever. A 300 mm diameter handwheel requires 300 mm of clear diameter around it, plus room to stand and apply force. In compact pipe racks, this is often forgotten at the design stage and corrected at substantial cost during construction.

Gear-operated and actuated valves require additional maintenance space: room to remove the actuator or gearbox with a chain hoist, access to the limit switch compartment, and space to remove the top cover or bonnet for repacking the stem. Include these requirements in the valve installation drawings at the engineering stage, not as a construction afterthought.

Buried valves need a valve box or access pit sized for the operating nut key and, if the valve will need repacking or inspection, large enough to allow work without confined-space entry requirements. Underground chambers should be treated as confined spaces for safety purposes regardless of their actual dimensions.

In high-temperature pipework, thermal expansion of the pipe during heat-up moves the valve flanges relative to each other. If the valve is independently supported from a fixed structure, the pipe and valve will fight each other as the pipe expands — either deforming the pipe, stressing the flange joints or damaging the valve body.

The support design must accommodate thermal movement. In high-temperature systems, guides and sliding supports allow the pipe to move axially or laterally while maintaining vertical support. The valve support should move with the pipe rather than restraining it. This is a piping engineering matter that should be resolved at the design stage with reference to the piping stress analysis.