We’ve talked before about the importance of valves to your building’s HVAC system. We’ve also highlighted six energy-wasting valve problems.
I think the next logical step in this series is to go through some inspection best practices to help you better identify these valve problems and keep your HVAC system running efficiently.
Let’s start with a checklist for a visual valve inspection. You can do these inspections either on a fixed yearly schedule or on an as-needed basis if you use predictive analytics tools.
Checklist for valve inspection
- Test for control loop stability by monitoring the control temperatures and valve positions over time, either at the plant room or from the BMS.
- Create a trend graph with available temperature (supply, discharge, and space) as well as valve and damper actuator positions, and then observe heating and cooling system functioning.
- Check the valve for leakage.
- Drive the valve closed and wait for the downstream temperature to stabilise. Then check with a temperature probe either side of the coil to ensure the temperature is the same, investigate any signs of let-by.
- Check for signs of weeping around the valve stem’s gland. If you see any, replace the gland kit or, if necessary, the entire valve.
- Look for any signs of galvanic corrosion on the valve body or pipe work, which can lead to leaks. If you find any, wire brush the area and use anti-corrosive paint, or in severe cases, remake the connection.
- Check your valve bonnets for evidence of scoring, which is sometimes caused by faulty actuator mounting. Tighten accordingly.
- Use an acoustic listening device to listen for rattling sounds, which may mean a plug has become detached from the stem. If there’s rattling, replace the stem and plug assembly, or the entire valve.
Assessing these eight points will help you ensure your valves are operating well. But don’t forget to check your valve and damper actuators! Here’s what to look for when inspecting actuators:
Checklist for valve and damper actuator inspection
- Cycle the actuator from open to close by changing the control signal from the BMS. Then check the fail return for correct operation.
- Check the wear and tightness of linkages and anti-rotation brackets.
- Look for any bending in the anti-rotation plate and replace if needed. This bending may be caused by excessive force used on manual override.
- Ensure the actuator linkage or anti-rotation bracket is touching the indicators. It may have come loose or it may be clogged with sediment. Make sure also that the actuator has enough force to close.
- Test the manual override’s performance and be sure to disengage it after the inspection.
- Check for fading colours on the position indicator. These may indicate high ambient or operating temperatures, which cause premature equipment failure.
- Listen for excessive noise in the actuator, which could mean it’s been operating too long. Overuse can cause premature failure.
- Assess whether the actuator is driving closed and repeatedly trying to close the valve. This would mean the actuator has dirt contaminants or simply needs recalibrating.
There you have it: Eight inspection best practices for your valves, and eight inspection best practices for your actuators. If these 16 recommendations have you thinking, ‘There’s no way I can do this for all the hundreds of valves in my building’, help is on the way.
Advances in building analytics tools are giving facility managers the ability to instantly check the actual status of each valve in real-time and into the future. These tools send monitoring data through cloud-based analytics to determine which individual valves have been overworking, underworking, and so on. Based on these data, the software will tell you which valves need servicing, and which ones don’t, so you can optimise your labor hours. By relying on a fixed schedule based on factory estimates, you may not catch premature failures and other issues before they eat into your bottom line.
If you’re curious about how to integrate predictive analytics tools into your maintenance regimen, ask me in the comments. And for a deeper dive into valve and actuator maintenance best practices, check out our new white paper.