Breakaway Shear Valves

Shear valves are an important part of the safety of any fuel dispensing system, stopping product flow in the event of collision or damage at the dispenser. In case of a collision, they work by a specially designed section of the shear valve body separating cleanly upon impact, causing poppet valves to seal on the valve body and prevent fuel spillage. Additionally, if a fire was to occur at the dispenser, a fusible link releases the fulcrum arm, engaging the poppet valve and stopping fuel flow.

However, emergency shear valves can only provide compliance if they are installed correctly according to the recommended procedures. When breakaway shear valves are installed incorrectly, as in the images above, it can cause the valve to fail to shear in the event of a dispenser accident. To ensure that shear valves will function properly in case of an accident they must be securely mounted at the correct level. There should be at least 3-5/16″ of clearance from the center line of the inlet pipe during the installation of the valve to prevent damage to the fulcrum arm when the valve is tightened, and to prevent the valve from striking against the side of the pit as the valve closes.

For optimal performance, Franklin advises all installers to follow the recommended procedures when installing any FFS petroleum equipment. When installing the shear valve, remember:

  1. The shear valve should be oriented so that the arrow points up (flow direction). Thread the valve hand tight. Finish tightening the valve by applying a wrench. Do NOT use a wrench on the valve above the shear section.
  2. The valve body must be rigidly anchored to a structural member within the island to ensure that the shear section breaks in the event of a severe impact.
  3. Do NOT over-torque any of the connections, as this may damage the valve, resulting in improper operation.

The correct installation of the shear valve enables compliance with the National Fire Protection Association (NFPA) NFPA 30A guidance to “mitigate fire and explosion dangers by providing safeguards for dispensing liquid and gaseous motor fuels into the fuel tanks of automotive vehicles”.

shear valves 2Resources:

NFPA 30A Code for Motor Fuel Dispensing Facilities and Repair Garages (2015 edition), National Fire Protection Association

Model 662-AGB Emergency Shutoff Valve Installation Instruction

Model 662 Top Adaptor Replacement Instructions