Types of Valves used in Piping

What is a valve?

A valve is a mechanism that opens and closes to control the flow of fluids. In a scientific context, fluids include both liquids and gases.
It is a device that is able to control, shut off, direct, or regulate the flow inside a pipeline by obstructing its flow direction, partially or completely, depending on the type of application.
Valves can also work through pressure or temperature and maybe run by a motor or operated manually.

The simplest valves are one way-flap mechanism that allows flow in one direction and shut with back-flow pressure to stop flow in the direction of origin.

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Different Types of Valves

In piping systems following types of valves are used depending on the requirements. The cost of Valve in the piping system is up to 20 to 30% of the overall piping cost. And the cost of a given type and size of the valve can vary 100%.

BALL VALVES

A Ball valve is a quarter-turn rotary motion valve that uses a ball-shaped disk to stop or start the flow. Most ball valves are of the quick-acting type, which requires a 90° turn of the valve handle to operate the valve.
Our company makes exact designed ball valves which are accessible in two ways, three-way and four-way ball valves. All our ball valves have a high steam execution level without steam spillage and are intended for better outflows control.

CHECK VALVES

The check valve prevents backflow in the piping system. The pressure of the fluid passing through a pipeline opens the valve, while any reversal of flow will close the valve.
Check valves, which is a mechanical gadget that typically permits liquid to move through it in one direction. There are two port steel check valves that have two openings in a body one for the liquid to enter and the other for the liquid to take off. We give shifted scope of the cast steel check valves which are very tough and practical

GATE VALVES

A gate valve is the most common type of valve in any process plant. It is a linear motion valve used to start or stop fluid flow. In service, these valves are either in a fully open or fully closed position. Gate valves are used in almost all fluid services such as air, fuel gas, feedwater, steam, lube oil, hydrocarbon, and most any other services.
Gate valves consist of flat closure element which slides into the flow stream to provide the shut-off and these are linear motion valves. Gate Valves is also known as the knife valves and slide valves. The door valves minimize the weight drop over the valves in the completely opened position and it totally stops the stream of the fluid. The benefit of the gate valves and the knife valves is that their application in slurries permits the entryways to slice directly through the slurry.
A gate valve functions by moving a wedge-shaped disc obstructer up and down to open and close the flow path through the valve. This linear motion is provided by a threaded rising stem. Turning this threaded stem requires multiple revolutions (multi-turn) to travel from open to close.
Ball and Gate valves are commonly used in home water pipelines. Note that the type of handle (green lever or red hand wheel) may change; however, lever handles are normally only used with quarter-turn valves. Garden hose valves are typically gate valves, so the flow of water can be controlled.

GLOBE VALVES

Globe valve is used to stop, start, and regulate the fluid flow. Globe Valves are used in systems where flow control is required and leak tightness is also necessary.
Globe valves operate by having a convex disc-shaped plug raise and lower via a rising stem into a circular seat around the inside of the globe-shaped body at the “equator”.
These globe valves are useful for flow control or on/off isolation of fluids and these are manufactured from the superior quality of the raw material.

PLUG VALVES

Plug valves that allow the attachment to turn all through its position lessening the scrapping or rubbing. It obliges the varied commercial enterprises which comprise of food and pharma, paper, material, sugar, power, oil and gas. Some of its features are highly durable, low maintenance cost, resistant to corrosion which makes its best utility in industries.
Plug valve is a Quarter-turn rotary motion Valve that uses a tapered or cylindrical plug to stop or start the flow. The disk is in a plug shape, which has a passage to pass the flow. Plug valve used as on-off stop valves and capable of providing bubble-tight shutoff. Plug valve can be used in a vacuum for high-pressure & temperature applications.
The basic construction of a plug valve is practically identical to that of a ball valve with the exception of the shape of the obstructer used.

NEEDLE VALVES

Needle valves are similar to a globe valve in design with the biggest difference is the sharp needle-like disk. Needle valves are designed to give very accurate control of flow in small diameter piping systems. They get their name from their sharp-pointed conical disc and matching seat.

BUTTERFLY VALVES

A butterfly valve is a shut-off valve with a relatively simple construction. In the closed position, the disc blocks the valve bore while in the open position, the disc is turned to allow flow. A quarter turn takes the valve from fully open to the fully closed position or the opposite, and thus the butterfly valve allows for quick opening and closure.
The “butterfly” is a disk connected to a rod. It closes when the rod rotates the disc by a quarter turn to a position perpendicular to the flow direction. When the valve opens, the disk is rotated back to allow the flow
Butterfly valves, which can be used for special applications like isolation, throttling and control. Butterfly valves are suitable for fluids like air, water, toxic gases, vacuum, acid, chemicals, LPG, slurries & a combination of gases and solid.
Butterfly valves can be used to limit flow; they are typically used as on/off valves.

How to evaluate valves

When selecting valves, the most important factors to consider are safety and reliability. The pressure required for the process, the temperature at which it operates and the materials involved all have an impact on valve selection.
The size of a valve is measured in terms of its diameter, which is usually expressed in inches or millimeters. The smaller the diameter, the more precise control you have over flow rates; however, smaller valves are also more expensive per unit of flow. Larger valves cost less but offer less precision.
Valve types include those that regulate flow by controlling pressure loss (pressure-based) or those that allow full flow through a restriction (flow-controlled). A pressure-based valve allows a constant rate of flow regardless of how much pressure is lost between input and output streams. Flow-controlled valves restrict flow based on how much pressure is lost between input and output streams — they let more fluid pass when there’s less pressure drop across them.

Because piping systems rely on valves to control flow and often restrict it when needed, valve selection is critical. With dozens of types, materials, manufacturers and models to choose from, evaluate each one on the basis of simplicity, efficiency and safety.

Simplicity

Simple design can reduce maintenance time by making it easier for an operator to understand how the valve operates. A simple design also decreases training requirements — a big plus for those who operate valves on a regular basis.

Efficiency

Efficiency means that an operator must be able to easily open or close a valve according to its intended use. Efficiency also means that there are no unnecessary parts in the design that could cause wear and tear over time.
It is easy to know what the system can handle at the time of installation, but corrosion and erosion of the valve from wear can make it the weakest link in the system.
When considering various valve types and materials, choose the valve that best maintains the temperature, pressure and compatibility of the system piping and fittings.

Safety

Safety refers to whether or not a component could break off during operation or cause injury if it were improperly used or maintained.

Most importantly, maintaining safety is the fundamental role of valves. If one of them leaks or sticks, a number of problems may arise.

If a reaction is dosed, the reaction chemistry can change, or last longer than necessary.
If the valve does not properly seal the tank when disconnecting the piping from the tank, a massive leak can occur.
If an unexpected backflow occurs, the check valve is the first line of defense.
If a failure occurs downstream, the valve must be engaged to prevent further leakage and to limit access to the chemicals being transported.
An inoperable valve may inadvertently allow two chemicals to mix, which can often become dangerous in industrial installations.
In each case, the leak can cause an unsafe spill or airborne toxin to workers, depending on the contents of the pipeline. In addition, accidental mixtures or chemical concentrations can create dangerous byproducts or accelerate wear and tear on the piping.

Conclusion

In this blog, I have tried to explain the term Valve. and their different types of valves with their functions.

Source: China Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.sfutube.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Stainless Steel Valves, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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