Cla-Val 81-02 No-Slam Hydraulic Check Valve

A check valve that opens and closes under control

The Cla-Val 81-02 is a hydraulically operated no-slam check valve. It opens when the pressure at the inlet exceeds the discharge pressure, and a controlled rate of opening prevents sudden opening surges. When pressure reverses, the higher downstream pressure is applied to the cover chamber through control tube lines and the valve closes drip-tight.

It is suited to services that need positive shut-off. The rubber disc seals tightly even when the fluid carries grit or small particles, and the simple packless design avoids leaks. The datasheet notes that the valve is optimized using Cla-Check software.

Technical specifications

Velocity and surge guidance

The effectiveness of this valve is related to pipeline velocity. Cla-Val recommends a maximum flow based on a pipeline velocity of 6 feet per second, and the suggested flow table on the datasheet uses that value; velocities can be increased to 10 fps if required, but a surge valve is recommended above 6 fps. Where velocities exceed 6 fps, consideration should be given to adding a Cla-Val Model 50-01 pressure relief valve or a 52 Series surge control valve to the system.

The standard arrangement is a single closing line on 100-01 bodies of 8 inch and smaller; larger valves use a dual closing line configuration. Optional features are CV flow controls for the closing and opening speed, an X141 pressure gauge assembly and an X101D valve position indicator.

Typical installations

Cla-Val shows the 81-02 as an integral part of a well designed pumping system, preventing damaging and sometimes expensive flow reversal. Applications on the datasheet are a deep well pump discharge and a booster pump discharge, where it stops return flow into the tank while the pump is off; a relief valve is good practice to minimize surges when the pump stops.

Suggested maximum flow at 6 fps is 63 gpm at 2 in, 138 gpm at 3 in, 240 gpm at 4 in, 550 gpm at 6 in, 950 gpm at 8 in, 2,100 gpm at 12 in, 3,400 gpm at 16 in and 7,700 gpm at 24 in.

Key features

• Hydraulically operated main valve based on the Cla-Val 100-01 Hytrol, with the 81-01KZ check valve in the pilot system.
• Controlled opening to avoid surges when the pump starts, and drip-tight closing when pressure reverses.
• Resilient rubber disc that seals tightly even with gritty water.
• Packless design with a single moving part in the main valve, avoiding stem leakage.
• Wide size range from 2 to 36 inch, globe or angle pattern, in ductile iron, cast steel or bronze.
• Options for opening and closing speed control, pressure gauges and a valve position indicator.

How it differs from a swing or spring check valve

A conventional swing check closes when flow has already started to reverse, and the sudden stop of the reverse column can cause a slam and a pressure surge. The 81-02 uses line pressure to drive the valve closed, with the closing pressure applied to the cover chamber through the control tubing. Because opening is controlled and the main valve has a full diaphragm-operated stroke, it is better suited to pumping stations where reliable sealing and reduced surge matter. It is still not a complete surge protection system on its own; on long or high-velocity lines it should be combined with relief or surge control valves, as Cla-Val recommends above 6 fps.

Selection guidance

Applications in Oman and the GCC

Water transmission and distribution networks in the region often pump over long distances and high elevation differences, from desalination plants and well fields to reservoirs. In these systems, check valves at pump discharges must close reliably without adding to transient pressures. The 81-02 suits deep well pump discharges, booster stations and transfer pump stations in municipal water, irrigation, district cooling and industrial water systems. Sand and silt in well water are a known challenge, and the resilient disc helps maintain a tight seal. Note that the pilot system is rated for water up to 82 °C.

Installation and maintenance

• Install isolation valves upstream and downstream so the valve can be serviced without draining the line.
• Protect the control tubing from mechanical damage and, outdoors, from long-term sun exposure.
• Set speed controls during commissioning and record the settings.
• Inspect the diaphragm, disc and pilot strainer during planned maintenance, especially on sandy well water.
• Check the valve closes tightly by monitoring pressure after the pump stops.

Documents and quotation

The engineering data sheet E-81-02 is attached, with the pattern and end connection selection chart and dimensions. Supply the size, flow, static pump pressure, pressure class and trim material when requesting a quotation, and say whether the pilot system should include speed controls. The same product page lists the reduced-port 681-02. More valves are shown under Fittings & Valves.