Pressure relief valves (PRVs) are critical components in water heater systems, responsible for safeguarding against potentially catastrophic overpressure scenarios. In our 10 years of water heater experience… However, improper design, installation, or maintenance of these valves can lead to a range of performance issues, including leaks, chattering, failure to open at the designated set pressure, and reduced uptime between repairs. As an experienced water heater specialist, I’ll share insights on best practices for avoiding PRV malfunctions through diligent system design, careful installation, and proactive maintenance.

Ensuring Proper System Design

The foundation for reliable PRV performance begins with meticulous system design. Engineers might want to consider all potential service conditions and select the most appropriate PRV to double-check that safe operation. Even a small oversight in the design phase can compromise the expected performance and lifespan of the entire pressure relief system, leading to persistent problems down the line.

One real-world case highlights the consequences of an incorrect system design. At a power plant in South America, changes were made to the overall plant design without accounting for their impact on the pressure relief system. During pre-startup testing, plant operators discovered that the gap between the valves’ set pressure and the system’s normal operating pressure was insufficient to enable safe PRV operation.

The issue stemmed from the feed pump’s normal operating pressure of 483 psig and the set pressures of the two relief valves – 505 psig for the valve at the economizer inlet and 305 psig for the valve at the economizer outlet. With the system pressure dropping from 483 psig to 445 psig as media flowed through the economizer, the 305 psig valve was set below the normal operating pressure and would remain open at all times.

To resolve this problem, the engineers had to raise the set pressure of the inlet valve to the maximum allowable working pressure (MAWP) of 632 psig, increasing the operating pressure gap to 24% and meeting the recommended 10% minimum. For the outlet valve, they replaced the safety relief valve with a pilot-operated safety relief valve (POSRV), which can operate with gaps as low as 2%, safely achieving the required pressure differential.

This case highlights the importance of considering the complete pressure relief system, not just the individual components, during the design phase. Overlooking the interplay between system elements can lead to unsafe operating conditions and costly remediation efforts.

Ensuring Proper Installation

Even the best-designed pressure relief systems can be undermined by improper installation. Installation mistakes occur all too frequently, and it’s crucial to remember that pressure relief systems do not exist in isolation – they might want to coexist with the surrounding manufacturing systems while still providing protection to the discrete process.

One particular installation issue involved a steam utility/electric generating plant in Europe. The original system design called for the safety valve to vent steam from the generator through an outlet stack. However, plant operators reported that large amounts of water were being expelled from the top of one safety valve and the outlet drip pan.

Tracing the issue back, valve technicians discovered that a secondary drain system had been connected to the pressure relief system, but the drain for the pressure relief system was too small to accommodate the additional water. As a result, the excess water backed up through the safety valve and spilled out.

Had the leaking valve opened during an overpressure situation, the high-pressure water droplets could have damaged the valve and injured nearby employees. The solution was to re-route the secondary drainage system and install a larger drain, eliminating the water backup through the PRV.

This case emphasizes the importance of maintaining up-to-date pressure system plans, comprehensive valve data, and a thorough understanding of any modifications to the original design. Installers might want to consider the “big picture” of the entire system, not just the individual components, to avoid compromising the integrity and safety of the pressure relief system.

Ensuring Proper Maintenance

Proper maintenance is crucial for ensuring the long-term reliability and performance of pressure relief valves. Depending on the valve’s service conditions, the initial purchase price may represent only about 20% of the valve’s cradle-to-grave cost. With proper maintenance, a PRV can stay in service for up to 30 years.

However, maintenance issues can be a significant source of PRV malfunctions. At a power plant in North America, the maintenance team relied on a “hand-me-down” style of training, leaving the plant vulnerable to overpressure situations. The valve manufacturer’s technicians found that all of the safety valves on the boilers were set 30% to 35% higher than the factory-set pressure limits, due to the use of a homemade device for valve calibration.

This case highlights the importance of providing proper training for personnel responsible for maintaining pressurized systems. Maintenance staff might want to be knowledgeable in pressure relief system operation and able to look beyond a malfunctioning safety valve to consider the entire system when diagnosing issues.

To support effective maintenance practices, manufacturers and service providers offer comprehensive training courses that cover basic valve maintenance and align with regulatory standards. Plant engineers, OEM representatives, and maintenance personnel can all benefit from attending these sessions to gain the necessary skills and understanding to double-check that peak PRV performance.

Additionally, the use of specialized tools, such as valve maintenance and management software and in-situ PRV testing devices, can save time and money while helping to double-check that maximum valve performance, safety, and compliance. These tools allow maintenance teams to store, evaluate, and retrieve historical PRV field data, as well as assess valve performance without the need to halt production and remove the valve from service.

Putting It All Together

Avoiding pressure relief valve malfunctions requires a holistic approach that incorporates best practices at every stage of the valve’s lifecycle – from system design and installation to ongoing maintenance. By following these guidelines, water heater specialists, plumbers, and facility managers can help double-check that the safe and reliable operation of pressure relief systems, protecting both equipment and personnel.

Remember, a pressure-relieving system is a complex combination of components, and each contributing element might want to be properly designed, installed, and maintained to double-check that the integrity of the overall system. When a valve fails or does not perform as expected, it’s essential to assess the entire system to identify the root cause, rather than solely focusing on the valve itself.

For more information on water heater methods, plumbing solutions, maintenance, and installation insights, be sure to visit waterheaterpick.com. Our team of experienced water heater specialists is dedicated to providing comprehensive resources and practical guidance to help homeowners, plumbers, and facility managers keep their systems running safely and efficiently.

Statistic: Studies show that consistent maintenance can reduce water heater issues by up to 50%