HYDRAULICS When maintaining safety-critical machinery, the advantages of zero-leak rotary shear directional control valves featuring Pressure Decay Proof (PDP) technology are not always widely recognised. These valves can resolve issues linked to leakage, pressure retention, and reliable control. Webtec, a manufacturer experienced in this specialised technology, has supported numerous hydraulic equipment OEMs and operators in overcoming such challenges through the use of these valves. 20 HYDRAULICS & PNEUMATICS February 2026 www.hpmag.co.uk The tangible benefits of zero-leak rotary shear valves Zero-leak rotary shear valves with Pressure Decay Proof (PDP) technology offer major advantages for safetycritical hydraulic systems, eliminating leakage, improving pressure retention and enhancing reliability. By simplifying circuits, reducing maintenance demands and enabling customised configurations, they provide robust, long-term solutions for ageing machinery, demanding environments and essential equipment where dependable control is vital. H&P spoke to Martin Cuthbert, Managing Director at Webtec. Fig. 1 – Rotary Shear Directional Control Valve To illustrate the real-world benefits of zero-leak rotary shear valves, Martin Cuthbert, Managing Director at Webtec, highlights an application involving a company that supplies oil well safety equipment and mobile drilling rigs. Despite long industry experience, the business was struggling with an ageing machinery fleet, rising reliability problems, and increasing difficulty sourcing spare parts. Cuthbert explains that the company’s technical staff play a central role in tackling such issues, but in this case the design engineer and service manager each had distinct requirements. The design engineer needed to develop a simplified the accumulator, and another valve to control flow direction. Cuthbert notes that reducing this to a single valve required a more innovative approach than a conventional 3-position, 4-port sliding spool valve. These tend to leak in the closed position due to the typical 5–10 µm gap between the spool’s outer diameter and the honed bore. This can lead to leakage of around 0.5–1.0 l/min at rated pressure. While acceptable in many hydraulic circuits, this leakage rate is unsuitable for safety-critical systems. Moreover, leakage can carry particulates that may accumulate and prevent reliable actuation. A rotary shear valve uses a different design incorporating pressure-loaded seats and a rotor. Cuthbert explains that these hardened, lapped components have optically flat, mirror-finish surfaces that provide metal-to-metal contact with zero or near-zero leakage depending on flow. The higher the pressure, the tighter the sealing surfaces press together. With one valve providing both zeroleak and directional control, the design engineer could eliminate the separate isolating valve, saving space, inventory, and cost. Pipe dreams come true Cuthbert adds that simplifying the safety Fig. 2 – Leakproof arrangement with sliding spool directional valve and isolating valve valve that could enhance the control of safety equipment. The service manager, meanwhile, required a dependable replacement valve for winch control on mobile drilling rigs—one that would help extend machine life and reduce maintenance costs. Both required a hydraulic valve tailored to their needs, so they approached Webtec. Using the company’s Make it BLUE (Begin, Listen, Upgrade, Engineer) custom-development process, Cuthbert says each project resulted in an effective solution that met its intended operational goals. Four key challenges The design engineer reduced the task of simplifying the oil well safety equipment circuit into four key challenges: reducing the valve count from two to one; minimising piping requirements; introducing high-pressure capability; and improving safety through a tamperproof design. Preference was given to an accumulator-fed safety system with a blow-out preventer. However, avoiding leakage from the accumulator when the cylinder is idle was essential in order to guarantee the availability of stored power in an emergency. Typically, such systems use two valves: a shutoff/isolating valve to retain pressure in
RkJQdWJsaXNoZXIy MjQ0NzM=