Damped Check Valves for Hong Kong Drainage Department

Our commitment to providing market-leading products secured our valve division, T-T Flow, an order for four large custom valves to Hong Kong; a region where we have an established installation base after many years of supplying high-quality flow control equipment.

The Problem

The Drainage Services Department of the Hong Kong Government commissioned our experts for four DN400 bespoke swing check valves with pneumatic dampers and flow sensing switches, forming part of a £1.6 million site refurbishment. As the only manufacturer of WRAS approved swing check valves with such a large diameter, T-T were specially qualified to meet the needs of the site.

The Solution

Self-acting swing check valves are crucial backflow inhibitors in pumped and gravity applications, without them uncontrolled returning flow can cause hydraulic irregularities, equipment damage and media contamination.

Designed to comply with BS EN12334 and EN1074-3, and having EN1092/PN16 flange drillings, these valves were made for reliable long-term installation. The valves feature:

• Weld overlay gunmetal precision machined seats for optimal sealing performance
• Ductile iron construction with a fusion bonded epoxy-coating for strength and corrosion resistance
• Acid-resistant, stainless-steel shafts that operate through supporting self-lubricating bronze bushes
• Elastomeric components conforming to BS6920, ensuring suitability for potable water applications

The valves also underwent rigorous independent evaluation by the Water Regulations Advisory Scheme (WRAS) to ensure they will not have any detrimental effect on the quality of potable water.

Due to the size of the valves and the scale of the application, the client requested that the valves include twin external weighted arms with pneumatic dampers and flow-sensing switches for local monitoring.

Pneumatic dampers, also known as cylinders, are often used with check valves to control and reduce the rate at which the valve closes. Abrupt closure causes a sudden change in fluid flow and consequently a rapid increase or decrease in system pressure – also known as water hammer. Water hammer can damage all aspects of a drainage system – including pipes, valves and pumps – and significantly reduce the lifespan of the equipment. Learn more about water hammer from our experts here.

Reducing the speed at which a check valve closes also serves to reduce operational noise, maintain system stability by preventing abrupt flow changes and provide more precise flow control to the operators.

Your Site, Our Facilities

T-T Flow offers a wide range of check valves – including ball check valves, axial check valves, dual plate check valves, recoil check valves, flap valves and more – supported by a variety of custom options, such as high-adaptable external weighted arms with various flange drillings configurations to suit your requirements.

Speak with a member of the team today to learn more or to order your own bespoke valve solution by emailing ttflow@ttpumps.com, calling +44(0)1630 647200 or completing an online enquiry form.