Control Valve

What is Trip-Throttle Valve? How does Trip-Throttle Valve works?

What is Trip-Throttle Valve?

Throttle/trip valves provide effective flow control and emergency shut-off operation in a single, highly reliable valve assembly.

In high-pressure pipe lines, such as the primary steam line serving a big, high-pressure turbine or a turbo-expander gas supply line, they are used as throttle valves.

They add a critical safety measure to these applications as trip valves, without the cost of a distinct trip valve.

Functions of Trip-Throttle valve:

Using a motorized operator or manual handwheel, the valve can be opened or closed to any required flow.

As the spindle is rotated, an essential pilot valve opens, releasing steam in the balancing chamber downstream

Through an air cylinder, petroleum cylinder, or solenoid, the trip valve mechanism is triggered. It is also possible to provide a manual lever.

The latch lever is automatically disconnected from the latch hook when broken. Working with the inner steam or gas pressure, a strong compression spring in the yoke forces against the seat the entire spindle system.

Trip-Throttle valve design:

The design concept of the standard trip throttle valve is basically that of a globe valve with a stem nut that is mounted in a frame or bracket that is free to move.

The basic designs of the trip throttle valve with respect to direction of travel can be placed in two categories:

  • those where the valve plug is pushed onto the seat by the closing force, and
  • those where the valve plug is pulled onto a seat by the closing force.

Because of the dual functions required of the valve-the tripping action and the throttling action-the stem must be in two pieces in both designs.

The stem of the valve’s steam shut-off part is not rotating ; it only slides to accomplish the necessary tripping action. In order to allow throttling, the actuator assembly stem has rotating motion so that it can be positioned within the spring-loaded, hydraulically positioned stem nut.

That it can be positioned within the spring-loaded stem nut, which is hydraulically positioned to allow throttling. Therefore, within the split coupling, there must be a change of direction and rotation.

The ends of the two stems are separated by a hardened steel button, commonly called a thrust bearing. It is difficult to maintain alignment between the two stems.


Instrumentation Engineer

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