Throttling means using the valve as a variable restriction rather than a simple on-off device. Globe, needle, butterfly and control valves throttle well; gate valves and most soft-seated ball valves do not, because a partly open gate vibrates and its seats are cut by high-velocity flow. Throttling service also raises the risk of cavitation, noise and erosion.
Throttle the discharge back until the pump amps come down to nameplate, then lock the handle there.
Also heard as
- throttling
- modulate
Related terms
Globe valve
A linear-motion valve that throttles well because its disc moves straight onto a seat across an S-shaped flow path.
Pinch back
To close a valve partway to cut flow or pressure, without shutting it.
Wire drawing
Erosion of thin grooves across a valve seat by a high-velocity jet leaking through a tiny gap.
Control valve
A power-operated valve that modulates flow on a controller signal to hold pressure, level, flow or temperature at setpoint.