A Guideline About Manual & Automated Valves

Valves are mechanical devices used to start, stop, and regulate the flow of liquids, gases, gels, powders, and other substrates by opening, closing, or partially obstructing one or more passageways in piping systems. A manual or automatic method can be used to accomplish this.

Manual valve actuation involves direct, physical contact with its hand wheel, lever, or gear operator, while power automated valve actuation uses air pressure, electricity, or hydraulic pressure controlled by flow conditions, monitoring systems, or other means that do not involve physical contact with the valve. Actuators allow valves to be opened and closed as well as throttled. In some valve actuators, switches or other means are provided to remotely indicate the valve position.

Among the materials used for valve construction are cast iron, carbon steel, stainless steel, chrome alloys, brass, bronze, Hastelloy, Inconel, monel, titanium, alloy 20, and PVC.

End connections of valves include flanges, buttwelds, threads, socket welds, lugs, and wafers.

Depending on its purpose, every piping system has unique features. When you understand the five common types of valves, how they work, and their different configurations, you will be able to select the right option for your system.

Ball Valves

In ball valves, a spherical, perforated, pivoting ball controls flow on and off. Their operation requires only a 90-degree movement to accomplish their objectives, so they are classified as quarter-turn valves. A hole is bored through the ball it uses to accommodate the flow. This hole matches the inside diameter (ID) of the installed pipe, which allows flow through the ball when the valve is open and closed when the valve lever is shifted 90 degrees. Despite many cycles, ball valves close securely even after long periods of inactivity. As a result, they are an excellent choice for shut-off and control applications. In ball valves, various seats and seals are used based on their service, pressure, and temperature. The materials used for seats and seals include virgin Teflon, TFM, reinforced Teflon, peek, nylon, Delrin, Kel F, graphite, 50-50, and metal.

Configuration Types

Ball valves are distinguished by their design into several types:

• Single Body

• Three-Piece Body

• Split Body

• Trunnion

• Top Entry

• Floating

A ball valve can also be classified based on its shape and function, such as:

• Full-Port

• V-Port

• Reduced-Port

• Multiport

• Cavity Filler

• Sanitary

Applications

Gas processing, transmission, storage tanks, steam, high pressure, high temperature, air, liquid, and other fluid applications are all common uses for ball valves.

Butterfly Valves

They are also classified as quarter-turn valves. There are three main components to a butterfly valve: a disc, a stem, and a seat. Their simple design allows them to be shut off by rotating the stem 90 degrees until the disc contacts the seat. The media flows past the disc on either side when it is opened.

Configuration Types

Depending on the location of the stem's connection to the disc, butterfly valves have two configuration types. Centrifugal valves have stems that pass through the center of the disc, creating equal flow on either side when the valve is opened. In eccentric designs, a stub shaft is offset from the center of the disc. Eccentric butterfly valves can be classified as single, double, or triple offset based on the number of stub shafts included in their design. Among the typical materials for seats and seals are Teflon, reinforced Teflon, EPDM, buna, and metal.

Applications

Among the many applications of butterfly valves are water supply, wastewater treatment, fire protection, gas supply, chemical and oil industries, fuel handling systems, and power generation.

Gate Valves

Contrary to quarter-turn valves, gate valves do not open and close with a 90-degree rotation of the stem. Gate valves require multiple turns in either a clockwise direction to open (CTO) or a clockwise direction to close (CTC). When the valve stem is turned, the valve disc is raised to open or lowered to close. A gate valve is only for on/off control, and should only be used fully opened or fully closed.

Configuration Types

Among the most common valve configuration types, gate valves differ based on the type of gate, how they rise on the stem, and how they are seated. Here are a few examples:

• Parallel slide

• Wedge

• Pressure seal

• Knife

• Bolted bonnet

• Welded bonnet

• Rising stem

• Non-rising stem

• With warm-up bypass

• Outside screw and yoke

Applications

Gate valves are often used in situations where pressure loss and free bore are required, and they prevent water hammering damage by opening slowly. Potable water, wastewater, irrigation, gas, and oil are among the industrial uses of these valves.

Diaphragm Valves

Instead of solid materials (plugs, discs, or balls) in various configurations to regulate flow, diaphragm valves use flexible, or elastomeric, discs, which add a pressure response element to opening, closing, or varying the valve's control. Linear motion valves are actuated by pushing the diaphragm into the seat at the bottom of the valve to shut off flow or lifting it to let it pass.

Configuration Types

There are various types of diaphragm valves based on the disc material (butyl, Teflon, EPDM, neoprene, etc.) and connection types (threaded, compression-fitted, bolt flange, clamp flange, butt weld). Alternatively, they can be lined with plastic, rubber, or glass.

Applications

Because these valves have minimal contact surfaces, they are the cleanest type of valve used in applications in pharmaceutical, food processing, and water treatment industries, as well as electronics, pulp and paper, power, and high-purity water applications.

Globe Valves

Globe valves are used to control flow isolation and throttling. With a disc valve, the disc is moved against the flow stream rather than across it as with a gate valve. As a result, vibration, wear, and abrasion are reduced. Through a globe valve, the flow pattern changes direction, resulting in a higher resistance than through a gate valve. As indicated by the flow direction arrow on the valve's body, valves must be installed in proper relation to media flow. There are bolted, pressure seal, welded, and screwed bonnet designs available for these valves.

Configuration Types

There are three basic types of discs for globe valves: metal plugs, renewable discs, and V-ports. The stem can also be positioned in either a 90-degree or 45-degree Y pattern angle to the valve.

Applications

It is used in boiler vents, drains, steam vents drains, turbine lube oil systems, seals, drains, feed water, chemical feed, fuel oil, and cooling water systems.

Check Valves

A check valve prevents backflow in a pipeline. As a result of a straight line flow through the valve, there is a minimum pressure drop. As media flows through the valve, the disc swings or lifts into an open position. The disc is held in place by back pressure in the pipeline and/or gravity. A check valve may be installed horizontally or vertically, but it should be oriented in the direction of media flow as indicated by the flow direction arrow. The covers of the valves can be threaded or bolted, while the discs can be made of metal or renewable material.

Configuration Types

There are swing, piston, ball, silent, dual disc, spring loaded, and stop check valves available.

Applications

In chemical, industrial, and power plants, check valves are used in many fluid systems.