Stimuli are signals that trigger the senses. Receptors detect the stimuli and neurons send the signals to the brain where they're interpreted. Each sense organ includes receptors that capture relevant stimuli for transmission to the brain. The receptors in the skin are mechanoreceptors and thermoreceptors.
AWWA Butterfly valves are quick opening valves that consist of a metal circular disc or vane with its pivot axes at right angles to the direction of flow in the pipe, which when rotated on a shaft, seals against seats in the valve body. They are normally used as throttling valves to control flow.
Piston & Ball Check Valves. Piston and ball check valves, like all check valves, are used to prevent back flow in the line. Standard valve design has no spring in order to minimize cracking pressure and pressure drop, it will only function properly when installed in a horizontal line.