To repair or replace?

Sept. 26, 2010

Solenoid valve maintenance & troubleshooting strategy

The small yet robust solenoid valve is a powerful electromechanical gatekeeper. It has the important task of controlling the flow of liquid, air, gases or particles for a larger system. Yet even the most reliable of valves can fatigue or become inoperable, thus shutting down or affecting a system’s performance. As with any mechanical apparatus, proactive maintenance of a solenoid valve can extend life and ensure consistent operation.

With regular maintenance, users can extend the lifespan of their valves and keep operations on track. In this image, an engineer is completing a valve maintenance check by taking apart the valve and reviewing the internal and external components for wear or damage, foreign particles, leaks and corrosion.

Often, a valve’s issue may be simple enough to identify and fix on your own. The nemesis could be the valve’s environment, the media or even the application. Valves that have to work harder often have a shorter lifespan — about 1-3 years. Through regular maintenance, users can extend the valve’s lifespan and keep operations on track.

Solenoid valve maintenance first focuses on identifying areas of wear and tear, and then replacing the affected components. In addition, the valve’s components are checked to ensure they are clean and free of material buildup that can affect the energizing and de-energizing of the valve system as a whole.

Some users wonder how maintenance of such a small component can be worthwhile, or what difference upkeep can make to the system. There are also questions regarding the appropriate time to repair versus replace a valve. This article will shed light on these topics, as well as the maintenance and troubleshooting processes for solenoid valves.

When to maintain a solenoid valve

Two-way, three-way and four-way solenoid valves are used in a variety of applications to control the flow of air and other media. Simpler valve designs are easier to maintain and more cost-effective to replace than complicated, high-end designs, particularly those built to suit the needs of a specific application.

One of the most common questions we receive at Parker Fluid Control Division is: When is the best time to service a solenoid valve? To help guide users in this regard, the following is a checklist of exploratory questions to consider:

• If the valve fails at an inopportune time, what is the opportunity cost?
Is there a risk for safety hazards when a valve fails?
• What is the financial cost of a total valve failure? Figure into the equation the costs for lost productivity and any work that requires replacement.
• What is the cost for servicing a valve? Include time and resources.

As a rule of thumb, when machinery is being taken apart for servicing, this is the best time to complete a valve maintenance procedure. A proactive approach can extend product life and create the best possible performance of both the valve and overall system.
How often a solenoid valve should be serviced depends upon its design and application. Certain applications are particularly damaging to the valve’s internal and external components and therefore require more attention. For example, without lubrication, components can wear quickly and may need to be replaced at 100,000 cycles or less. However, if the media flowing through the valve is lubricated or provides lubrication, it can provide component life up to millions of cycles.

In another example, a solenoid valve’s design may have small clearances between moving parts and/or small orifices through which media must travel. If the valve controls unfiltered, corrosive or viscous media, the liquid substance may have difficulty traveling through the valve, substantially increasing the likelihood of premature failure.

Valves can easily be disassembled to inspect and repair internal components. Here is an example of a valve used primarily in car washes. The nut and washer are removed, and the sleeve is unscrewed from the valve body. From the sleeve assembly, the plunger and return spring can be easily removed for inspection.

For standard valves, it can also be a challenge to control media as common as air and water. Applications that involve dry air and rapid cycling can be among some of the most damaging to the valve’s operation. The lack of lubrication combined with the constant pounding of the internal parts can cause component deterioration and warping. Alternatively, valves that control water may have the lubrication to operate but can experience mineral buildup, which can worsen when the water sits idle in the valve for extended periods of time.

In these situations, building a maintenance regimen can extend the valve’s life as well as keep the application’s functionality running smoothly. It is best to create a maintenance schedule and consider the cost as necessary to avoid expensive repairs or replacements in the future.

Repair or replace?

To make the repair-versus-replace decision, consider the valve itself along with the overall application. Different solenoid valves have varying levels of durability. Simply designed and constructed valves enjoy a low replacement cost, making replacement the most simple and cost-effective choice. Valves with high-end designs, however, rely on the interaction of components and field maintenance may not replicate the valve’s original function. On top of that, replacements usually cost more than simple maintenance, especially custom-designed valves. Although a complicated choice, replacing a high-end design, though costly, is the best recommendation.

Of course, maintenance usually implies the replacement of the rubber parts and springs. However, any remaining parts showing wear or damage should also be replaced. Another issue to consider is the valve’s connection. If the connection has sweat fittings or its location makes removal of the valve difficult or dangerous, it may be best to leave the valve body in place and rebuild its components regularly. Extra caution should be made to verify the valve seat has not been nicked or worn, as this can result in seat leakage, even in valves with new seals.

Where cost is the primary criteria, replacement is most often the best choice. Generally, solenoid valves are inexpensive in comparison to the cost of service labor. The time and manpower it takes to disassemble the valve, replace the parts, reassemble, install and check for proper performance often outweighs the cost of labor to simply install a new valve.

Step-by-step solenoid valve maintenance

Sometimes, the top expert for proper valve maintenance is the valve’s manufacturer. Many offer replacement part kits, which can include replacement o-rings, springs, a plunger, and possibly diaphragms, pistons and a host of related components. Of course, make sure the replacement kit is appropriate for the particular valve. The valve may have been designed specifically for the manufacturer as a private label and might include parts from various other providers. To be sure, always look for the manufacturer’s name on the valve.For any valve maintenance regimen, there are four easy steps to follow:

Some valves are developed with serviceability in mind. The steam valve pictured above is designed with a threaded bonnet to allow for easy service and maintenance, which in turn reduces the application’s downtime.
  1. Safety first. Disconnect the power source and depressurize the system before repairing a valve. Also, be sure to properly and safely handle the unit based on the fluid it controls.
  2. Coil. Inspect the coil for cracks. In wet or humid environments, moisture might penetrate the coil and cause valve failure. While reviewing the coil, check its connections for damage or corrosion, which can also affect valve performance. When powering up an AC coil, ensure the coil is properly installed on the valve’s sleeve or stem. Otherwise, the resulting influx of current might result in a coil burn-out.
  3. Pressure Vessel. When the coil is removed, the remaining unit is called the pressure vessel. Its sleeve will have a feature that accepts a sleeve removal tool like a wrench. Try to avoid clamping onto the sleeve tube, as this may cause the tube to dent or bend. Once you have removed the sleeve, the valve body will expose the internal components of the valve operator, including the plunger with a seal, the plunger return spring, an O-ring, the sleeve and operator body. Systematically examine each for damage or wear, and replace as needed:
    • Take a look at the seal for any signs of swelling, cracking or deterioration.
    • The spring should be inspected for worn or broken coils.
    • The body orifice itself may have been nicked or the crest worn.
    When the plunger lifts, it normally makes contact with the sides and stop of the sleeve. As a result, the top of the plunger and the inside of the sleeve may show wear as well. For more complex solenoid valve types utilizing diaphragms, pistons, spools and levers, follow the manufacturer’s instructions for maintenance.
  4. Reassembly. Once all necessary parts are replaced and the valve is cleaned of build-up and grime, reassemble the pressure vessel according to manufacturer directions and reattach the coil. Then, reinstall the newly assembled valve back into the application. Once the parts are accurately installed, power up the valve again.

Now, with the information provided in this article, you should be able to determine whether to adopt a maintenance or replacement regimen for your solenoid valves, as well as how to maintain one. For problems and questions beyond those covered in this article, always contact your solenoid valve manufacturer. The manufacturer is your best source of information on its particular valve and can help you address any special needs you might have based on the specific application.

Michael D’Amato is a manager with Parker Fluid Control Division with more than 30 years experience in sales, engineering and applying solenoid valves to end-use applications, including industrial and process industries. Mr. D’Amato can be reached at [email protected] or 860 827-2300.

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