Tackling Butterfly Valve Leaks and Corrosion

Customer Testimonial

“The site’s maintenance and performance records showed that the most common issues across installed valve assets were stem seal leakage and excessive torque during operation… After evaluating a range of alternatives under operational conditions, GEMÜ valves consistently demonstrated superior reliability, lower maintenance demands, and improved overall performance compared with other products previously used in these systems."  - Membrane Manager at the Water Treatment Works

GEMÜ Great Britain helped eliminate persistent stem seal leaks, corrosion and high operating torques affecting butterfly valves within an ultrafiltration (UF) membrane plant. 

Following a detailed site assessment, GEMÜ identified the root causes and supplied the D480 butterfly valve series, delivering improved reliability, reduced maintenance requirements and enhanced long-term performance, backed by ongoing technical support.

The Challenge

GEMÜ Great Britain supported a large water treatment works in addressing prolonged downtime caused by valve failures within its ultrafiltration (UF) membrane plant. The site produces up to 8.5 megalitres of drinking water each day, making reliability essential. The valves within the membrane process perform frequent operating cycles and play a critical role in maintaining plant performance. The site had been experiencing recurring failures with installed butterfly valves from another manufacturer, resulting in increased maintenance requirements and unplanned downtime.

The primary issues included:

• Stem seal leakage causing water ingress into pneumatic actuators.
• Air system contamination leading to actuator failures.
• Corrosion and liner deterioration affecting valve performance.
• Excessive operating torque placing unnecessary strain on actuators.
• Leakage and reliability concerns impacting day-to-day plant operation.
• Increased health and safety risks for maintenance personnel.

The Investigation

GEMÜ Great Britain carried out a detailed site survey with the operations and maintenance teams to identify the root causes of the failures. The investigation found that the existing butterfly valves featured a single ‘U’-cup seal design, which struggled to retain media when installed horizontally, resulting in stem seal leakage. The valves were also over-specified at 16 bar for a process operating below 6 bar, thus requiring larger actuators, increasing operating torque and placing additional strain on the seals.  

Material compatibility was another issue, with nylon-lined discs and EPDM liners unsuitable for the site’s CIP chemicals, contributing to corrosion and premature deterioration. The loose liners were also displaced under vacuum conditions, leaving them vulnerable to damage during valve operation. The investigation reinforced the importance of understanding each individual application before specifying a valve solution, particularly as operating conditions and cleaning chemicals can vary significantly between water treatment sites.

The Solution

Following the site assessment, GEMÜ recommended the D480 butterfly valve series, selected to suit the application’s operating and vacuum conditions.

The supplied solution included:

• A two-piece stem seal design to improve sealing integrity and minimise leakage.
• Undercut discs rated for 6-10 bar, reducing operating torque and allowing smaller, lighter actuators.
• An integrated leak channel to protect pneumatic actuators should a seal failure ever occur.
• Stainless steel discs combined with WRAS-approved EPDM liners for improved corrosion resistance and potable water compliance.
• Bonded liners designed to withstand repeated vacuum conditions without becoming displaced.
• Ongoing technical support throughout installation and commissioning.

By selecting materials appropriate for the process and optimising the valve specification for the actual operating conditions, the site received a solution designed to improve both reliability and long-term performance. Through close collaboration with the site team, GEMÜ was able to eliminate the issues affecting the UF membrane plant.

Conclusion

Reliable butterfly valves are essential to maintaining efficient membrane treatment processes. By combining application expertise, detailed site assessments and correctly specified valve technology, GEMÜ helped the site eliminate recurring reliability issues and improve the long-term performance of its UF membrane plant.

At GEMÜ, providing expert advice and taking the time to understand each application and priorities are central to how we work. By considering operating conditions, installation requirements and chemical compatibility from the outset, we can recommend solutions that not only address immediate challenges but also support greater reliability, reduced downtime and improved performance over the long term.  

GEMÜ D481 pneumatically operated butterfly valve with bonded liner.

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