Industrial valves can be divided according to their function, material, construction, etc.

Based on their function, industrial valves can be divided into: shut-off, control and safety valves.

The most common classification of industrial valves based on their construction: ball valves, gate valves, poppet valves, butterfly valves (throttle valves), non-return valves, diaphragm valves and safety valves.

The valves in each of these groups can be further divided according to the material they are made of: stainless steel, brass, cast iron, cast steel, plastic.

The nominal pressure for typical valves is usually specified at room temperature (about +20°C).

There is often a relationship between working pressure and working temperature for industrial valves. As the working temperature increases, the allowable working pressure for the valve decreases.

To determine the value of the allowable working pressure, tables or diagrams showing the dependence of the working pressure on the working temperature are used.

The most common seal material used for ball valves is pure PTFE (high chemical resistance), or PTFE with glass fibre filler (increased abrasion resistance), graphite (high temperature resistance) and even stainless steel (abrasion and high temperature resistance). There are also seals made of PEEK (high strength and temperature resistance), and PA or POM used in valves for hydraulic oils. Specialized ball valves come with pure graphite or all-metal seals.

Concentric butterfly valves and diaphragm valves are sealed with NBR, EPDM, FKM and VMQ elastomer seals or plastic seals such as PTFE bonded to an elastomer.

Eccentric butterfly valves, on the other hand, often have metal (lamellar) seals, or metal and PTFE+graphite laminated seals.

In industrial poppet valves and gate valves, a metal-to-metal seal is often implemented, where the closing element (poppet, gate), seals on a metal seat. Such a combination, however, may not ensure 100% valve tightness.

In simple industrial butterfly valves the shaft is located in the centre of the disc. The disc in high performance butterfly halves is eccentric: the shaft is offset from the centreline of the valve body, the geometry of the disc/seat sealing surface is altered (conical profile). These valves are used for more challenging applications, or larger diameters. This design alternations lower the torque required to reverse the valve.

Weld a two-piece valve (with extended connections) directly into the piping system, taking care not to overheat the valve (seal may get damaged), by cooling the valve during welding.

A three-piece valve is first pre-assembled between the connections (tack weld), and the connections are welded after the body with seals is removed. After the connections are cooled, the valve body is assembled, making sure that the ball is in the closed position when the body is screwed together with the connections. The entire unit is screwed together with the correct torque.

When welding valves, it is important to align both connections of the piping system and to prepare their ends for the chosen welding technology.

ATEX Directive 2014/34/EU (Article 2, §1) and ATEX Guide (§38) specify that equipment and simple pipe components, such as manual valves, check valves, mesh filters, pressure regulators, safety valves, are not covered by the directive, as they do not have their own potential source of ignition. Therefore, these components do not require certification to be installed in hazardous environments, but still, the components with antistatic protection should be used.

Only the valves with an actuator (electric or pneumatic) are subject to ATEX Directive.

Valves for natural gas installations for buildings should comply with EN 331 standard. In Poland, the valves with a maximum operating pressure up to 20 bar are to be used for these applications (designation MOP5-20), for continuous operation under normal operating conditions.

The valves designed for oxygen service, which are degreased at the production stage and properly secured by the manufacturer, until installation in oxygen pipelines, can only be used in oxygen systems. The installation process needs to be performed with due cleanliness, as lubricants can self-ignite in a pure oxygen atmosphere.

If valves are to be used for steam, their seals must be resistant to high temperature. Graphite filled PTFE (up to +260°C), or stainless steel reinforced PTFE (up to +260°C), are the most common materials for ball valve seats. PEEK also has good resistance to high temperatures and is used for ball valve seats intended for operating temperatures up to +250°C. For extreme temperatures, pure graphite (up to +500°C) or metal (up to +500°C) is used for ball valve seats.

The optimum choice for steam applications are steam globe valves (shut-off, shut-off/control, or shut-off/non-return) and gate valves with high operating parameters (up to +425°C) and a relatively low price.

Diaphragm valves (pneumatic, mechanical), or butterfly valves are commonly used for abrasive media such as gravel, sand, cement, limestone grit. The type of elastomer used for the sleeve or cuff is important in these two types of valves. Natural rubber, SBR, or HNBR have higher abrasion resistance.