In any industrial fluid system, valves are essential components. They control and maintain ideal flow levels, and they must function reliably to ensure operational efficiency, profitability, and safety. Valve maintenance requires proper planning and attention. Understanding what could go wrong gives technicians an advantage when it comes to keeping valves in top working order.
By Sam McCulloch, Associate Product Manager – Swagelok Company
Operators of these complex valve systems must have short- and long-term maintenance protocols mapped out before problems arise so they can solve any issues quickly and cost-effectively.
Prepare for Effective Maintenance from the Beginning
It is possible that the reason a valve is not operating at peak performance is that it was improperly installed. Therefore, it is critical to ensure valves are installed correctly from the beginning to lower potential maintenance problems over the life of the components. To ensure proper installation, one should:
- Always follow the manufacturer’s installation instructions. Read the instruction manual, attend training sessions, or watch videos to understand the proper steps of assembly and disassembly, including proper tightening, see Figure 1.
- Be aware of the capabilities and operating parameters of the system. For example, a valve should never be placed into service where the temperature or pressure inside the system exceeds the ratings of the valve.
- Allow adequate space for access and future maintenance. Maintaining a valve is typically a hands-on activity. Make sure to place valves in locations that are easily accessible, when possible.
- Mount valves securely to a fixed location whenever possible. Use adequate supports for the tubing or piping where viable on both sides of the valve to minimize vibration, see Figure 2.
- Ensure the proper orientation of the valve to allow media to flow in the correct direction. Look for helpful indicators on the valve body or stem to get the orientation right.
- Check for leaks after installation. Consider ultrasonic monitors or liquid leak detectors to help here.
- Avoid contaminants. An operator can do this by adding filters to the fluid system to help remove particulates that may interfere with proper valve operation. Such particles can cause damage to valve seats, contaminate process fluid, and reduce overall flow throughout the system.
Adhering to these guidelines as valves are installed will offer the best chance for problem-free operation over the components’ lives.
Conduct Preventative Valve Maintenance
After proper installation is complete, the next step in keeping valves operating at peak performance is to develop a preventive maintenance (PM) schedule. By maintaining the valves before problems surface, reliable operation can be better maintained. Preventive maintenance can help operators avoid major problems down the road, saving companies time and money in the process.
PM schedules must be tailored to specific systems because no two systems are exactly alike. Several different factors could have a significant impact on how long a system will operate, including pressure, temperature, the chemical composition of the process fluid, and how many times a system will be turned on/off over its lifetime. In addition, it makes sense to discuss PM with valve suppliers who should have valuable insights into how best to keep their products working properly.
The goal of any PM schedule is to check the valves regularly to ensure they are working at peak performance. Often, the quickest way to tell if a system is working correctly is whether it is leaking. Sometimes, leaks are detectable when operators engage their senses. For example, a chemical leak may have an obvious odor before it is located visually. In other circumstances, it might re- quire external equipment, like ultrasonic monitors, Figure 3, or liquid leak detectors, Figure 4, to detect a leak. Catching a valve leak early can prevent a more serious problem.
Common leak causes include unreliable metal-to-metal seals, system contamination, poorly installed end connections, or improper tubing selection. In these situations, troubleshooting becomes paramount. Below are several key troubleshooting techniques.
Test the valve.
Make sure the valve is operating as intended and figure out the location of the leak. Frequently, leaks occur at one of two specific places within the valve:
- A seat leak, where the leak is contained inside the valve, but fluid passes through the seal and the valve is unable to stop the flow,
- A shell leak, where fluid leaks outside of the valve into the atmosphere, often through the stem or body of the valve.
Inspect the valve.
Perform a visual inspection of all the valves’ internal components to determine if the seats, O-rings, or stem tips are worn, or damaged.
Repair the valve.
If the leak is being caused by worn components, it may be possible to repair those components without the expense and downtime associated with replacing the entire valve. In some instances, that could require a complete rebuilding of the internal components, see Figure 5. Suppliers will often provide seal kits to do such repairs without an entire valve replacement.
Maintain the valve.
Once the repairs are completed, it may be necessary to adjust PM schedules to better reflect how the valves in the system are wearing. Using tags on repaired valves will allow technicians to quickly see indicators of what valves are designed to do and how often they should be inspected.
When to Replace a Valve
If a valve is damaged beyond repair, it may be time to replace the valve entirely. Some situations when complete valve replacement may be required (even if the internal components are not irrevocably damaged) include:
- Heavy corrosion that has deteriorated the valve body, compromised its pressure-retaining capabilities, and created a safety risk,
- Major contamination that cannot be cleaned,
- Overtightening a valve at its end connections causing damage, rendering it unusable for reinstallation.
In other situations, it may be necessary to replace a valve that has no damage to it. It is possible that the cost of a new valve is better than spending excessive money on repair, which could be costly if labor and testing are taken into account. Operators must also factor in the costs of potential production downtime when considering any maintenance on mission-critical fluid systems.
Why It Matters
Keeping valves operating at peak performance can be the difference between a functioning fluid system and one that fails. Having a better understanding of how to install valves from the beginning, troubleshooting valves once they are installed, and keeping effective PM plans in place will improve the safety, efficiency, and profitability of any operation.
Many suppliers offer training courses to improve overall valve knowledge for operators, and it may be advantageous to attend that training whenever possible. After all, understanding how valves operate and how to solve simple issues could save operations money and time in the long run.
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