Industrial shut-off valves: types and applications

Classification by function

• shut-off — opens or blocks flow;
• control — adjusts flow rate or another process parameter;
• check — prevents reverse flow;
• safety — protects equipment from unacceptable pressure conditions;
• breather and vacuum — manages the gas space in tank systems;
• special-purpose — performs sector-specific functions defined by the equipment design.

Ball valves

The closure element is a ball with a through-bore. A quarter-turn moves the device between open and closed positions.

This valve is normally used for isolation. Whether prolonged operation in an intermediate position is permitted depends on its design and must be confirmed by the manufacturer.

Butterfly valves

A rotating disc blocks flow in a butterfly valve. The compact design is convenient for large nominal sizes.

Performance depends on the seal type, disc material, connection and actuator, so identical DN values do not imply identical suitability.

Check and safety valves

A check valve automatically prevents flow in an unwanted direction. A safety valve provides protection and forms part of the equipment’s engineered safety system.

These devices cannot be selected by connection size alone: their characteristics must meet the design and applicable standards.

What DN and PN mean

DN is a nominal size used to standardise connections. It need not equal the measured internal bore diameter. PN is nominal pressure within a standardised designation system; it does not permit operation at that pressure at every temperature.

GOST 4666-2015 requires key valve markings, including DN, PN, body material and manufacturer. Valves with a specified one-way flow must indicate flow direction. Where required, marking also includes allowable or design temperature.

Compare body markings with the product documentation: matching DN and PN values do not guarantee the same material, temperature range, leakage class or function.

Leakage class is a separate characteristic

GOST 9544-2015 establishes closure leakage limits and testing requirements. A closed valve therefore does not always imply absolutely zero leakage: allowable leakage depends on the specified class, valve type and test conditions.

The leakage class must suit the process. Isolating hazardous media, vacuum lines, water or auxiliary circuits can require very different performance. An unnecessarily high class may raise cost and maintenance requirements; an insufficient class may make the valve unsuitable.

• test medium and differential pressure must follow the specified method;
• compare results with the limit for the assigned class, rather than the subjective criterion of no visible leakage;
• after closure repair, leak-tightness must be confirmed by the prescribed tests.

Safety requirements added by GOST 12.2.063-2015

Valve safety involves more than body strength. GOST 12.2.063-2015 covers operational risks including pressure, temperature, actuation and personnel contact with hazardous surfaces.

For valves in accessible rooms with medium temperatures above 50 °C or below −40 °C, the standard provides thermal protection measures such as insulation, guards or protective equipment. Where accidental contact is possible, the design seeks to keep accessible metal surface temperatures within a safe range.

Selection therefore considers not only DN/PN, but also personnel access, actuation method, the risk of medium release during maintenance and the need for remote control.

Sespel’s industrial experience

Sespel’s spare parts catalogue includes valves, ball valves, filters and fittings. For example, a fuel tanker breather valve has DN 32 and operates at small positive and negative pressure differences, while a DN 80 ball valve is rated at PN 1.6 MPa.

These examples illustrate engineering selection: function, DN/PN, body material, connection, medium temperature and required leak-tightness are considered together.

Data needed for engineering selection

Engineering selection begins with valve function, working medium and design parameters. Body and seal compatibility, pressure-temperature range, leakage class, connection and actuator are then checked.

After selection, verify documentation and markings against GOST 4666, leakage requirements against GOST 9544 and safety requirements against GOST 12.2.063. Critical systems also use sector-specific standards and test methods.

• function and required safe position;
• working medium and material compatibility;
• working and design pressures, and temperature range;
• DN, connection type and standard;
• closure leakage class;
• control type, fail-safe behaviour and cycle frequency;
• maintenance conditions and personnel protection requirements.