Flow Control Technology Valve

Wedge gate valves differ from parallel gate valves in that the closure member is wedge-shaped instead of parallel, as shown in Figure. The purpose of the wedge shape is to introduce a high supplementary seating load that enables metal-seated wedge gate valves to seal not only against high, but also low, fluid pressures. The degree of seat tightness that can be achieved with metal-seated wedge gate valves is therefore potentially higher than with conventional metal-seated parallel gate valves.

These valves are provided with floating seats that are forced against the disc by the fluid pressure. These halves are interlinked so that they wedge apart when being moved into the fully open or closed positions, but relax in the intermediate position to permit the disc to travel.

Parallel gate valves are slide valves with a parallel-faced gate-like closure member. This closure member may consist of a single disc or twin discs

Piston valves are closing-down valves in which a piston-shaped closure member intrudes into or withdraws from the seat bore

Globe valves are closing-down valves in which the closure member is moved squarely on and off the seat. It is customary to refer to the closure member as a disc, irrespective of its shape.

Manual valves serve three major functions in fluid-handling systems: stopping and starting flow, controlling flow rate, and diverting flow. Valves for stopping and starting flow are frequently employed also for controlling flow rate, and vice versa, while valves for diverting flow are designed for that single purpose.

Compression packings are the sealing elements in stuffing boxes. They consist of a soft material that is stuffed into the stuffing box and compressed by a gland to form a seal around the valve stem. The packings may have to withstand extremes of temperature, be resistant to aggressive media, display a low friction factor and adequate structural strength, and be impervious to the fluid to be sealed. To meet this wide range of requirements, and at the same time offer economy of use, innumerable types of packing constructions have evolved.

Flat metallic gaskets adapt to the irregularities of the flange face by elastic and plastic deformation. To inhibit plastic deformation of the flange face, the yield shear strength of the gasket material must be considerably lower than that of the flange material.

One of the duties of most valves is to provide a fluid seal between the seat and the closure member. If the closure member is moved by a stem that penetrates into the pressure system from the outside, another fluid seal must be provided around the stem.

In this article, we try to demonstrate control valve design and sizing calculation.

The function of the shutdown valve is to shut-off the fluid flow inside the fluid flow line or pipe when an emergency that leads to a hazardous situation comes. It is an actuator operated valve mainly used for safety purpose that is why it is called Emergency shutdown valve. It is also known as the shutdown valve or SDV, ESDV, ESV, ESD.

A control valve is used in the oil and gas industry to regulate the flow rate of the fluid in a pipeline or process (and the related process parameters as pressure, temperature, and level) according to signals managed by a controller. The role of a flow control valve in the complex petrochemical process is key, as the multiple loops involved in the process should be kept under strict and dynamic control to make sure that the process, as a whole, works as intended and produces the desired output in terms of quantity, quality and time.