KCL’s R5V Series is a pilot-operated pressure relief valve built to the Denison-type R5V design standard — the same design lineage that underlies our KT6/KT7 pump range. For system designers already working within Denison or Parker-compatible hydraulic architecture, the R5V gives you a verified, interchangeable relief valve that mounts directly onto pump or actuator flanges, without the need for a separate manifold block.

Why Pilot-Operated Relief Matters

A pressure relief valve’s job sounds simple — open when pressure exceeds a set point, protect the circuit, close again once pressure drops. But directly-operated relief valves, which rely on a single spring-loaded poppet to do this job at full system flow, often struggle with pressure override (the tendency for actual relief pressure to climb well above the set point as flow increases) and can react sluggishly or unstably under rapidly changing load conditions.

Pilot-operated designs like the R5V solve this with a two-stage architecture: a small pilot valve senses system pressure and controls a larger main-stage poppet, which handles the actual high-flow relief function. This arrangement gives you tighter, more consistent pressure control across a wider flow range, with better response to sudden pressure spikes — exactly the behavior a demanding industrial hydraulic circuit needs from its safety and pressure-control valve.

Flange-Mounted for a Genuinely Compact Circuit

One of the most practical features of the R5V design is its SAE flange mounting. Rather than requiring a separate valve body plumbed into your circuit with additional hose or pipe connections, the R5V mounts directly onto the outlet flange of a pump or the inlet flange of an actuator. This achieves a meaningfully more compact overall circuit design, reduces the number of fittings and connection points that can potentially leak, and — for circuits requiring multiple valve functions — R5V valves with SAE flanges can be bolted together to combine functions without needing a dedicated manifold block at all.

For OEMs designing compact hydraulic power units where every centimeter of enclosure space matters, this flange-mounted, stackable approach to valve integration is a genuine design advantage over subplate-mounted alternatives.

Multiple Sizes, Multiple Pressure Stages

The R5V Series is available across a range of body sizes to match different flow capacity requirements, from smaller SAE port sizes suited to more modest circuits up to larger SAE port sizes capable of handling substantially higher nominal flow rates. Within each size, multiple pressure stage options are available, allowing the valve to be specified precisely against your circuit’s actual relief pressure requirement rather than forcing an over- or under-rated valve into your design.

Both 2-port and 3-port body configurations are available. The 2-port design is suited to straightforward relief applications, while the 3-port body adds flexibility for circuits requiring an additional connection point — useful in more complex control schemes or where a vent function is being integrated.

Three Ways to Adjust

The R5V offers three distinct adjustment modes, each suited to different operational and security requirements:

Hand knob — for applications where operators or maintenance staff need quick, tool-free access to adjust the relief setting.

Acorn nut with lead seal — for applications requiring a tamper-evident adjustment, where the relief pressure setting needs to be locked in place and any unauthorized adjustment would be immediately visible.

Cylinder lock — for the highest level of adjustment security, where only personnel with the correct key can access and change the pressure setting.

This range of adjustment options means the same core valve platform can be specified appropriately whether you’re building equipment for a controlled industrial environment or a safety-critical application where unauthorized pressure adjustment poses a genuine risk.

Optional Vent Function

For circuits that need to unload to minimum pressure during idle periods — reducing energy consumption and heat generation when full system pressure isn’t required — the R5V is available with an optional vent function. This allows the valve to be remotely commanded into an unloaded, low-pressure circulation state, then returned to normal relief operation when the circuit resumes full duty. This is a genuinely valuable feature for equipment with distinct idle and working cycles, where minimizing energy use during idle periods has a real cumulative impact on operating cost.

Typical Applications

• Hydraulic power units requiring compact, flange-mounted pressure protection
• Circuits benefiting from stacked, manifold-free valve integration
• Applications requiring tamper-evident or lockable pressure settings
• Systems with distinct idle/working cycles that benefit from vent-function unloading
• Industrial machinery currently built around Denison or Parker R5V-compatible circuit design

Why Choose KCL’s R5V Relief Valve

Pressure relief isn’t a component you want to compromise on — it’s the safety margin between normal operation and a damaged pump, a burst hose, or worse. KCL’s R5V Series brings the same manufacturing discipline we apply across our pump and motor range to this critical safety component, giving you a pilot-operated relief valve engineered for stable, accurate pressure control, verified interchangeability with established Denison/Parker circuit designs, and manufactured under our ISO 9001:2015 certified quality systems.

Need help specifying the right R5V size and pressure stage for your circuit? Share your flow rate and relief pressure requirements with our technical sales team.