Saturday, September 1, 2012

Globe Valve vs Gate Valve

  • Both flow valves,Globe valve and gate valve have similar external housing but operational functions of both differ little. The main difference between globe and gate valve  is in the form of the inner elements and the form of the flow inside the both valves . Globe valve has very good throttling ability while gate valve is not used for throttling.Gate valve is best suited for isolation and globe valve is best suited for regulating or throttling the flow.
  • Globe valve cannot seal tight as compared to gate valve.Gate valve has tight shut-off ability in pipe lines.Because of this tight shut-off ability of gate valve,it is used upstream of globe valve.You might have seen this gate and globe valve combination at the discharge pipe of pumps.
  • Globe valve requires greater torque to operate as compared to gate valve.This greater power requirement for globe valve is also considered when designing automatic and motor operated actuators for valves.
globe valve vs gate valve
  • Gate valve is not designed to regulate flow ,and if done so then we observe noise ,vibration and seat / disk damage in gate valves.While globe valve can be sometimes used for stop start of flow in case of unavailability of gate valve.Gate valve is generally used for isolation .
  • Gate valve can be used in both directions as designs are available for both directions of flow.Same gate valve can have flow in both directions.While globe valve has flow direction usually indicated on it and is used in compliance with that.
  • Valve Opening and closing geometry of disk and seat is also a difference between globe and gate valve. In a gate valve, the closure element is a plate or disk which travels parallel to the plane of the seat. The gate in a dam is a well known example. In a globe valve, the closure element is usually called a "poppet", and it travels perpendicular to the plane of the seat.
  • The globe valve can be repaired in place while nearly all gate valves need to be removed from the piping system to have leakage problems repaired.
  • A globe valve can be opened against a high differential pressure, while a gate valve will bind and cannot be opened. If you try to open against a high DP, the seat will score and leak.
  • A globe valve has a near linear  characteristics of Cv vs. % open, while a gate valve has a severe parabolic characteristic and thus cannot be used for throttling.
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