If you throttle with a Check Valvesgate valve, a swirl is set up that scrubs the back side of the gate. The gate can be eroded. How much damage and how fast it occurs depends on the fluid and pressure drop across the Plug Valvesvalve. If nothing else, you have really terrible control with a gate valve. I see throttled gate valves most often ahead of Safety Valvescontrol valves to prevent hunting. Many control valves are seriously oversized, and hunt even at what is a high process load. Throttling the upstream isolation valve provides aSafety Relief Valves pressure drop ahead of the control valve, and the reduced inlet pressure has the effect of Balance Valves"making the control valve smaller", often eliminating the hunting. However, when the time comes to work on the control valve, the upstream gate valve typically won't hold, because it's been damaged due to throttling.

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