Shut-off valves are an integral part of any pipeline system. Without them, it is impossible to control the flow of liquid or gas, perform maintenance, or eliminate emergency situations. In this article, we will analyze what types of shut-off valves are available, where they are used, how to choose the right one, and what mistakes to avoid.
What is a shut-off valve and what is it used for?
Shut-off valves are a class of pipeline valves designed to completely block or open the flow of a working medium (water, steam, gas, petroleum products, etc.). Unlike regulating valves, which smoothly change the flow rate, shut-off valves operate in two positions: «open» or «closed.».
The main function of shut-off valves is to provide hermetic cut-off of a section of the pipeline. This is necessary when:
- emergency shutdown of the section;
- scheduled repairs or replacement of equipment;
- regulating the distribution scheme in the system.
The reliability of the fittings directly determines the safety and smooth operation of the entire system.
Where are shut-off valves used?
Pipeline shut-off valves are used at industrial facilities, in water supply, heating, gas supply systems, as well as in municipal and residential infrastructure.
Shut-off valves for water supply and heating
Water shut-off valves are the most common category. Water shut-off valves are installed at each responsible node of the network. They are installed at building inlets, on branches between floors, in front of water meters, pumps, filters and heating elements. The main requirement is corrosion resistance and compliance with sanitary standards for drinking water.
Shut-off valves for heating must withstand elevated coolant temperatures — from 90 °C and higher in some systems — as well as cyclic pressure drops. Gate valves, ball valves, and check valves are widely used here.
Shut-off valves for gas pipelines and industrial pipelines
Gas pipeline shut-off valves are a separate category with increased requirements for tightness. Even a slight gas leak is unacceptable. Therefore, special seals and materials are used here that do not allow micropores.
In industrial pipelines, shut-off valves operate in extreme temperatures (from −60 °C to +600 °C), aggressive environments, and high pressures. This requires industrial shut-off valves with reinforced casings and appropriate certificates.
Main types of shut-off valves
Depending on the design of the shut-off element, the following main types of shut-off valves are distinguished:
- Latch — the shut-off element moves perpendicular to the flow, completely blocking the passage. Has low hydraulic resistance in the open state. Designed for large diameter pipelines.
- Ball valve — a locking element in the form of a ball with a hole. A quarter turn of the handle opens or closes the passage. Compact, fast-acting, easy to maintain.
- Shut-off valve (valve) — the gate moves along the flow axis. Provides precise regulation, but has greater hydraulic resistance. Often used as a shut-off and control element.
- Rotary shutter (disc shutter) — the shut-off disc rotates around an axis inside the housing. Compact, lightweight, suitable for large diameter pipelines at low pressure.
- Check valve — not manually operated; automatically closes when the flow direction changes. Protects the system from water hammer and reverse flow.
- Cork tap — a closing element in the shape of a cone or cylinder. It is used mainly in low-pressure gas networks.
Classification of shut-off valves
The classification of shut-off valves helps to quickly navigate the types of equipment and choose a solution for specific operating conditions.
Classification by type of construction
| Type of reinforcement | Locking element | Course | DN range |
| Latch | Wedge or disc | Linear | DN 50–1200 |
| Ball valve | Ball | 90° swivel | DN 15–300 |
| Shut-off valve | Plate/disk | Linear | DN 15–300 |
| Rotary shutter | Disc | 90° swivel | DN 50–1400 |
| Check valve | Plate/ball | Automatic | DN 15–800 |
Classification by connection method
The following types are distinguished by the type of connection:
- Flange connection — bolted fastening through sealing gaskets. Most reliable for large diameters and high pressures. Easily dismantled for maintenance.
- Threaded connection — threaded fitting. Suitable for DN up to 50–65 mm, widely used in domestic systems.
- Welded connection — non-separable; used where leakage is unacceptable (gas pipelines, aggressive environments).
- Interflange (wafer) connection — the valve is clamped between two pipeline flanges. A compact and lightweight solution for rotary valves.
Classification by body material
The material of the case also matters:
- Gray iron casting (GIC) — budget option for systems with low pressure and temperature. Vulnerable to shock loads and water hammer.
- Ductile iron (GGG-40/50) — increased strength, more resistant to impacts than gray cast iron. Common in water supply and heating.
- Carbon steel — for high pressure and temperature, industrial applications.
- Stainless steel — resistant to corrosion and aggressive environments. Food industry, chemistry, hot water supply.
- Brass — common in domestic and utility systems DN 15–50. Good corrosion resistance when used with water.
- Polymers (PVC, PP, PVDF) — chemical industry, aggressive environments, low temperatures.
Valve materials for different operating conditions
The choice of body and seal material directly affects the reliability and service life of the valve. Let's consider the main combinations:
- Water (cold and hot): Malleable iron or brass for DN up to 50 mm; malleable iron or steel for larger diameters. Seals — EPDM or NBR.
- Pair: Carbon or stainless steel. Metal or graphite seals - rubber cannot withstand temperatures above 120–150 °C.
- Gas: steel or ductile iron with special seals. Mandatory certification for gas systems.
- Aggressive chemical environments: stainless steel (316L) or polymer materials (PVDF, PP). PTFE (Teflon) seal.
- Oil and petroleum products: carbon steel, NBR or FKM (Viton) seals.
Key parameters for selecting shut-off valves
When selecting shut-off valves, it is important to consider not only the diameter of the pipeline, but also the conditions in which the equipment will operate daily. It is the pressure, temperature, type of working medium, body material and connection method that determine the reliability of the system and the service life of the valve.
How to choose valves by pressure and temperature
Each product is marked with a nominal pressure PN (Pressure Nominal) is the maximum pressure at which the valve can operate continuously at a temperature of +20 °C. As the temperature increases, the permissible pressure decreases.
For example, PN16 fittings at a temperature of +120 °C may not withstand PN16, but a lower pressure - this is indicated in the temperature-pressure reduction tables in the technical documentation.
Selection rule: The PN of the valve must be equal to or greater than the maximum operating pressure in the system, taking into account water hammer.
Selection of fittings according to the working environment
Before choosing, you need to clearly determine:
- composition of the medium (water, steam, gas, chemical solutions);
- presence of abrasive particles (sand, sludge);
- pH of the environment (acidic, alkaline, neutral);
- degree of pollution.
For clean drinking water, most types of fittings are suitable. For wastewater and sewage, rubber-coated wedge valves or elastomer disc rotary valves are suitable. For chemical media, stainless steel or polymers are suitable.
Selection of connection type and pipeline diameter
DN (Nominal Diameter), nominal bore is the approximate internal diameter of the pipeline. For fittings, DN must match the DN of the pipeline on which it is installed.
The connection type is selected depending on:
- pipeline diameter (DN ≤ 50 - thread, DN > 50 - flange);
- the need to dismantle the fittings;
- operating conditions (temperature, pressure);
- requirements for tightness.
When is an electric actuator needed for shut-off valves?
An electric actuator for shut-off valves is used in cases where:
- the fittings are located in a hard-to-reach place;
- remote control from the automation panel is required;
- fast response is required (emergency shutdown);
- The system is fully automated and manual intervention is undesirable.
The electric actuator transmits torque to the valve spindle or shaft. For multi-turn valves, high-speed gear actuators are used; for ball valves and butterfly valves, quarter-turn actuators are used.
When choosing an electric drive, the following factors are taken into account: the required torque, supply voltage, IP protection degree, climatic design, and the presence of limit switches.
Symbols of shut-off valves and markings
The marking of shut-off valves allows you to quickly determine their main technical characteristics without a detailed study of the documentation. Most often, the designations indicate the nominal diameter, nominal pressure, body material, type of seal, connection method and design features.
What do DN and PN mean?
DN (Nominal Diameter / Conditional pass) — dimensionless number corresponding to the approximate internal diameter of the pipeline in millimeters. Standard series: DN 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, 150, 200, 250, 300…
PN (Pressure Nominal) — maximum allowable pressure in bars or MPa at a temperature of +20 °C. Common values: PN 6, PN 10, PN 16, PN 25, PN 40, PN 63, PN 100, PN 160.
How to read the marking of fittings
Typical example of marking: Wedge valve f/f DN100 PN16 GGG-40 EPDM
- f/f — flange/flange (connection type on both sides);
- DN100 — conditional passage 100 mm;
- PN16 — nominal pressure 16 bar;
- GGG-40 — housing material (ductile iron);
- EPDM — sealing material.
The valve body is also marked with: a flow direction arrow (for valves and check valves), the manufacturer's trademark, year of manufacture and the casting number (for valves in systems with increased responsibility).
Comparison of different types of shut-off valves
Each type of shut-off valve has its own purpose, advantages and limitations, so there is no universal solution for all systems. To make the right choice, it is worth comparing not only the price, but also the operating conditions, opening frequency, tightness of the overlap, installation features and maintenance requirements.
Which is better: a gate valve, a valve or a ball valve?
|
Criterion |
Latch |
Ball valve |
Shut-off valve |
|
Hydraulic resistance |
Minimum |
Small |
Average |
|
Switching speed |
Slow |
Ambulance |
Medium |
|
Application diameter |
DN 50–1200 |
DN 15–300 |
DN 15–300 |
|
Adjustable |
Not recommended |
Not recommended |
Possible |
|
Compactness |
Big |
Compact |
Average |
|
Cost at large DN |
Lower |
Higher |
Medium |
The gate valve is optimal for large diameters and relatively infrequent switching. Low hydraulic resistance allows it to be used on main lines.
Ball valve is ideal for systems with frequent switching, where compactness and speed of operation are required. Indispensable in domestic systems.
A shut-off valve is a good choice where a combination of shut-off and the ability to slightly regulate flow is required.
Which fittings are suitable for high pressure?
For high pressure (PN 40 and above) steel gate valves and valves are best suited. Ball valves are also manufactured for PN 40–100, but their cost increases significantly in large diameters. Butterfly valves are usually used for pressures up to PN 16–25.
Typical mistakes when choosing shut-off valves
Below is a list of typical errors:
- Underestimation of PN. Installing fittings with a PN lower than the system operating pressure is a direct risk of accident. Always consider water hammer, which can be 2–5 times the static pressure.
- Not taking temperature into account. PN16 fittings for cold water are not suitable for hot water supply with a temperature of +90 °C without checking the temperature-pressure drop.
- Incorrect choice of seal material. NBR rubber seals are incompatible with steam, and EPDM with petroleum products. Mixing materials leads to rapid failure of the valve.
- Using the valve in a half-open position. The valve is not intended for flow control. Prolonged operation in an intermediate position will damage the wedge, leading to a loose closure.
- Ignoring the installation method. Some ball valves and valves have restrictions on orientation in space. Improper installation is a cause of premature leaks.
- Savings on seal quality. Cheap fittings with low-quality soft seals quickly fail at elevated temperatures or pressures.
Algorithm for selecting shut-off valves for specific tasks
The selection of shut-off valves should always begin with an analysis of the system: where it is installed, what environment it covers, what pressure it operates under, and how often it will be used. For domestic, commercial, and industrial facilities, the requirements can vary significantly, so the same valve is not always equally effective in different conditions.
Selection of fittings for apartments, boiler rooms and industry
For an apartment and a private house:
- Determine the DN of the pipeline - typically DN 15–32.
- Check the system pressure - usually 4–6 bar (PN 10 is sufficient).
- Choose the material: brass ball valves for cold and hot water, gas.
- Connection type - threaded.
For boiler rooms and heating stations:
- Determine the coolant temperature and operating pressure.
- For large DN (50+) - flanged valves or rotary valves.
- The material is malleable iron or steel.
- Seals - EPDM (up to 130 °C) or metal (over 150 °C).
For industrial facilities:
- Perform a hydraulic calculation of the system.
- Determine all the parameters of the environment: composition, pressure, temperature.
- Select the PN and housing material taking into account the aggressiveness of the environment.
- Consider the need for automation (electric drive, pneumatic drive).
- Check the availability of the necessary certificates (DSTU, PED for pressure objects).
Shut-off valves for aggressive environments
An aggressive environment is any environment that causes corrosion or destruction of standard materials. These include: acids, alkalis, chlorides, hydrogen sulfide, and seawater.
Recommendations:
- The body is made of 316L stainless steel or special alloys (Hastelloy, Duplex).
- Seals are PTFE (Teflon) or FKM.
- In the presence of abrasive particles - valves with a hard-coated shutter or ball valves with a reinforced ball.
- Regular inspection and replacement of seals depending on the aggressiveness of the environment.
Conclusion
Valves are a key element of safety and controllability of any pipeline system. The correct selection of valve type, material and PN/DN parameters guarantees reliable operation throughout the design life.
If you pick up industrial shut-off valves for critical facilities or looking for solutions for water supply or heating systems - contact UKSPAR specialists. We will help you choose the optimal fittings for your operating conditions.
