Manual Globe Valve

Control Valves: Plug and Seat Vs Disc and Cage

Wellsite separators and dehydration units require reliable valves to function correctly. Fabricators often use control valves and manual globe valves to manage the liquid flow in such devices. Let us look at them in detail for better understanding.

Types of Valves in Wellsite Separators & Dehydration Units

Control Valve

A control valve allows to check and direct liquid flow in the equipment by varying the size of the flow passage according to a signal from a controller. This provides direct control of flow rate and the monitoring of process quantities such as temperature, pressure, and fluid level. It is an essential component in most process systems in the petroleum industry. Control valves are available in a variety of configurations and styles. A sliding stem control valve is the most common type, derived from the manually operated globe valve.

Manual Globe Valve

Manual Globe ValveAs the name indicates, a globe valve has a spherical body shape. An internal baffle is used to separate the two halves of its body. It has an opening and a movable plug to close the valve. A plug or a disc in the globe valve is attached to a stem, which is controlled using a handwheel. Typically, automated globe valves use smooth stems, and an actuator assembly is used to open and close them.

Now, let us look at the main components of the valve, plug and seat, and disc and cage along with the differences between them.

Components in Manual Globe Valves & Control Valves

Plug and Seat

This is a simple configuration. The plug is a tapered or conical shape that seats or fits into an orifice hole the size of the largest dimension of the closed plug. The position of the plug, when fully up or open and down or closed, is proportionate to the flow through the valve. Depending on the flow characteristics required, there are many shapes of the plug.

Disc and Cage

This configuration is a more complex design. It offers more flow characteristics. The disc slides up and down inside a cage or a cylinder that has openings in the walls. As it moves, the holes in the cage are exposed and consequently, the flow changes. Depending on the flow characteristic required, the openings in the cage walls are of many shapes.

Difference Between Plug & Seat Vs. Disc & Cage

Basis of DifferencePlug & SeatDisc & Cage
ConfigurationIt is a simple design.It involves a more complex arrangement.
CostThe manufacturing cost is low due to the less complicated design.The cost involved in manufacturing may be comparatively higher.
UsesIt is typically used as a dump valve where the flow characteristic is not crucial.It is required where a precise flow is essential because the layout and shape of the openings have a direct effect on the flow of the liquid.
ApplicationDue to the quick reaction of pressure, they are mostly put to use as emergency pressure relief valves.They are often used where there is a high differential pressure across the valve.

We Can Help You Select the Right Valve

Can we help you find the right valve?Crimtech Services Ltd is a reputable supplier of oil and gas equipment, including wellsite separators and dehydration units. We also carry a large inventory of new and refurbished control valves in stock. Our designers have the experience and expertise to select the correct valve for every oil and gas package we sell.

As part of our design and fabrication services, we make sure that essential regulatory standards by the Alberta Energy Regulator (AER), the BC Oil and Gas Commission, and the Saskatchewan Ministry of Energy and Resources are followed.

For more information, please get in touch with us by calling 403-342-7579 or toll-free at 1-800-993-9958.

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