Don't Wait for a Shutdown to Find Out Your Valves Won't Hold

Valves have no run hours and no obvious wear schedule, yet they do several critical jobs across a refrigeration system:

Most operators treat a valve that isn't leaking as healthy.

A stem can seize, packing can wear down, and a seat can stop sealing, all without a drop of oil or refrigerant showing.

That wear usually surfaces only when a valve finally has to do its job. David Fauser, Director of Sales at CIMCO, calls valves unsung heroes that sit quietly in the system until "all of a sudden you want to use it after 15 years, and it doesn't hold anymore."

Contractors run into this regularly. "We go to isolate a system, and the valves don't hold. It happens all the time," Fauser says. Closing valves further back means a bigger pump-out and more of the system offline. A technician without industrial refrigeration experience can lose half a day or more just finding the culprit, and in a production facility, that time is expensive.

Sometimes no one finds out until a major project. Bell once worked on an older facility that wanted a safer system with a lower ammonia charge. The owners believed its redundant piping was isolated. When the team pumped out the system and opened those valves, they found the valves had leaked for years, filling that piping with ammonia. The system held far more refrigerant than the owners had assumed.

Before you can inspect your valves, you need to know where they are. Bell advises starting with the system drawings, tracing the lines, locating each valve, and learning the legend so you can read each valve type's symbol. Valves often sit in interstitial spaces, near ceilings, or on the roof, and you don't want to search for one in an emergency.

No drawings? A team can audit the system and produce a set, or the contractor that installed it may still have them on file. If management pushes back on the cost, Bell suggests escalating through your health and safety committee. Fauser points out that a single misstep while isolating part of the system would cost more than a new set of drawings. Valve tags cost little, and they let anyone match a valve in the field to its place on the drawing.

Day to day, look for oil around valves on an ammonia system and any sign of refrigerant leaking, especially at the packing around the stem. On an uninsulated line, a valve leaking when it's closed can give itself away by temperature, because the pipe downstream turns cold. If you have automation, trend each area. When a zone starts losing temperature control, a worn valve is often the cause.

A visual check only goes so far. On a running system, you can't see inside a valve, so the only real test is to exercise it (opening and closing it fully), and that's where operators can get into trouble. For the most part, leave valves alone while the system runs. At an ice rink, closing the suction valve while the compressors run will shut them down, often into a locked-out alarm. Close a compressor's discharge valve, and it trips on high pressure, provided the safety controls work. If they don't, pressure builds until relief valves lift. Regulators and control valves hold the pressures that set your temperatures. Adjust one without restoring its exact setting, and the system won't run correctly.

Regularly exercising valves makes them last longer, Bell says. The key is doing it while the system, or the part you're working on, is down. For an ice rink, he advises building valve exercising into the service contract so technicians handle it during seasonal shutdowns.

Larger plants take more planning. Industrial systems can have hundreds of valves, sometimes close to a thousand, and on a system that size, Bell estimates a day a month of maintenance time is reasonable. Schedule it around operations. A production facility that's down one day a week should use that day. A cold storage facility may need to shut down one area at a time, exercise its valves, and bring it back online before moving to the next. Expect to cycle through those areas less often.

Exercise the valves ahead of any major shutdown so the service team doesn't spend billable hours finding the ones that won't close.

Beyond exercising, a few routine tasks keep valves working. Most valves are built around a stem, a seat, and packing, and for a stop valve, those tasks are:

Keep packing material, gaskets, and spare valves in inventory, so you can fix a leak on the spot when maintenance turns one up.

Bell rejects the idea that you should replace a valve only when it fails. The right approach depends on the valve type.

Valves that move constantly, whether driven by pressure, a solenoid, or a motor, wear out fastest. On an evaporator, a motorized valve keeps adjusting to deliver the right amount of liquid. Thermostatic expansion valves respond to suction, spring, and bulb pressure, while back-pressure regulators shift every time temperatures change or units cycle.

These control valves rarely announce that they're failing. On a large cold storage plant, Bell says, it's very difficult to tell. The signs show up elsewhere, as an evaporator that freezes up or stops cooling, gets too much or too little liquid, or goes into hot-gas defrost and won't come out. If you're always chasing temperature in one area, check its valves.

In a freezer, a hot-gas solenoid valve should be cold whenever the unit isn't in defrost.

Even a small leak sends hot gas into an evaporator that should be cooling, and Bell ranks it as probably one of the biggest drains on a system's efficiency.

Stop valves rarely need replacing whole. Bell recommends rebuilding them during a system pump-out and replacing only those with damaged seats.

Relief valves are the one type you replace on a schedule rather than by condition. Bell says they must be changed every five years, so confirm the requirement in your jurisdiction. You can recertify them instead if you have a second set to install while the first is out for service.

Each relief valve's tag shows its installation date, so walk the plant, note the dates, and budget accordingly. Order about six months ahead, since some models have long lead times, but don't stockpile spares, because relief valves are date-stamped and can expire on the shelf. Always replace a relief valve that has blown. Those mounted on a three-way valve are easy to change, while others may need a pump-out. Don't let them lapse. Relief valves are the easiest thing for an inspector to shut you down on.

A major equipment replacement is the best time to address valves because the system is already pumped out. When you replace an evaporator that's been in service for decades, Bell's view is that you should replace its valves too.

Old valves disturbed during the work tend to leak after start-up, and that means another pump-out. Staff can help keep the job short by staging the new valves at their locations before the crew arrives.

The same project is a chance to add isolation valves where they're missing. Bell describes a site where corroded condenser piping needed replacing, but the only isolation valves sat at the oil coolers. A small piping repair turned into a full-day high-side pump-out. A couple of main isolation valves, costing a few thousand dollars at installation, would have made it a much smaller job.

Gaps like that can start with the original quote. Fauser notes that contractors often cut valves first to lower a project's price. Undersizing them is a common shortcut, and on a main line, a valve smaller than its pipe can become a restriction as loads change. When you compare quotes, confirm each one specifies the right valves at the right size.

Newer valves usually perform better, with more precise evaporator control and lower energy use, so ask your contractor what's available for your design.

Fauser recommends building an asset plan. Record where every valve is and its condition, along with relief valve dates, then fold replacements and upgrades into your budget cycle so the money is there when equipment comes due.

A valve can pass every visual check and still fail the one test that matters. Map your valves, exercise and lubricate them on a schedule, rebuild them before they fail, and renew them whenever you replace the equipment around them. A valve you've recently tested is one you can rely on.