Protecting Valves and Actuators from the Cold
Winter is here!
Stories from the Trenches
Before diving into how to protect valves, let’s look at some real examples of problems our technicians have encountered that have been caused by frozen valves.
Example 1: Water from below
Several years ago, we got a call from a company with an actuator on the fritz, or so they thought. After trying unsuccessfully to troubleshoot the problem over the phone, I drove to the job site to check it out. He performed an actuator test, and, as reported, it didn’t work. Then I lifted the actuator off and ran it independently of the valve. Lo and behold, it worked just fine.
The problem wasn’t the actuator. It was the valve. But since the valve was below ground, it was easier to pin the blame on what you could see.
What had happened?
Buried valves have a gap of about ½ to 1 inch between the valve extension and the torque tube. This gap can fill with water and freeze. In this case, the water had frozen and the gap was closing up about 36 inches below ground level.
This downtime could have been prevented. The gasket between the valve and the torque tube had broken, so the water egress was coming from the bottom up. If the company had winterized the valve before the freeze, they would have discovered the problem. This is a case where regularly scheduled maintenance would have saved a week’s worth of downtime.
Example 2: A lesson in hydrostatic testing
The second case had a similar result -- a week of downtime due to problems caused by freezing -- but the cause was much different.
Again, we got a call during winter about a faulty actuator. When our technicians got on site, they discovered that the actuator had turned into a block of ice. Here’s what had happened: The company had completed a commissioning project the summer before, during which they ran water in the pipeline to perform hydrostatic testing on the valves. During that testing, however, they failed to isolate the actuator from the pipeline by removing the power gas tubing. As a result, the actuator sucked up about 15 gallons of water. They didn’t do any preventative maintenance after the test, so they didn’t know the water was there. When the temperature dropped, the water in the actuator and the tanks froze solid.
The solution was to remove the actuator, take it to the workshop, heat it up, and drain the water. Another example of a week of downtime that could have been prevented by proper maintenance.
How Can You Protect Valves and Actuators From the Cold?
Protecting valves and actuators involves annual maintenance as well as using products designed for extreme temperatures. Here are four approaches we’ve found effective.
Problems start to happen after the ground frost. That’s why most valve manufacturers recommend winterizing on a yearly basis before the first freeze.
For buried valves, the basic winterization process is to drain any fluids from the stem extension and then fill the stem extension, including the torque tube hollow, with environmentally friendly antifreeze. For actuators, the process is different for each type, but the idea is the same: make sure there is no water that could freeze.
Winter lube is a valve lubricant specifically designed to work in sub-zero temperatures. At Allied, we use a winter lube for gate, plug, and ball valves that is good down to -40°F. In fact, we’ve had such good results with this product that we use it across the board, even in areas unlikely to see freezing temperatures. This offers greater flexibility because companies can use same products across all of their facilities and pipelines. It also reduces complexity because now you need to inventory only one product. Finally, using the same product for everything reduces the risk you’ll pick up the wrong piece and put it in a valve.
Another way to protect your systems is by using the proper hydraulic fluid in gas-over-hydraulic actuators. For colder areas (roughly Chicago northward), we recommend using high viscosity index (HVI) 15-weight oil to help with speed and freeze-off issues. Anything south of that, we recommend HVI 22-weight.
Pre-filters in wet gas applications
In the summer, moisture in natural gas areas isn’t a big problem. But in the winter it can result in water carryover, contamination, and freezing. In these areas, we’ve had success putting pre-filters on the power gas inlets. These filters remove the saturated water and other fluids from the gas to prevent these contaminants from being introduced into the system.
To ensure that equipment is properly protected, we recommend three courses of action:
- Perform regular preventative maintenance on all valves to catch any small problems (like a broken gasket) before they become big problems (like a week of downtime).
- Winterize valves annually before the first frost.
- Use a valve management system to track the maintenance and repair status of all valves along a pipeline.
Winterizing valves is pennies on the dollar compared to a valve replacement or a down pipeline. Literally. That $6,000 or $8,000 a company invests now in maintenance costs may save $600,000 or more in broken equipment and non-deliverable gas or oil.
If you haven’t done your annual maintenance yet, don’t worry. With El Niño currently bringing above average temperatures across the northern parts of the country, it’s not too late.
The issue is that assemblies are not currently treated as “engineered” items — they are often produced by slapping the actuator on the old (or new) valve specified by the piping requirements without much understanding of the specifics of the interactions between valve and actuator connections through the drive train (coupling).
All too often, the mounting kit is considered trivial, an afterthought deemed a commodity within all the other specified control components that comprise a complete automated valve package.
Since the early days of water and wastewater treatment plants in the U.S., municipalities and industries have continued to expand and upgrade existing plants and distribution infrastructure as well as build new facilities.