The drawing indicates a shut-off valve, the application says «valve», and the supplier offers several similar products. To select valves for a specific area, you need to check the structure, stem sealing and permissible operating parameters. In this article we will compare UKSPAR Fig.V101, Fig.V103 and Fig.V113. The purpose is similar, the capabilities are different.
Valve and shut-off valve: is there a difference in terms?
In pipe fittings catalogs, these names often refer to the same product. The term "valve" describes a design in which the plug moves along the flow axis through a seat. The word "vent" is traditionally used for such a device with manual control via a handwheel and threaded spindle.
When the specification states a shut-off valve, the main task of the product is to block the passage of the medium. The name itself does not yet allow it to be used for constant flow regulation. To throttle the flow, an appropriate valve shape and manufacturer's approval are required.
Valve design: spindle, disc, seat, seal
The principle of operation of the product is very simple:
- The flywheel rotates the spindle, the thread converts the rotation into translational motion.
- The shutter, which is called a disc or spool depending on the design, approaches the seat and closes the opening.
- When opened, a passage appears between them.
This is how both steel versions and cast iron valves with a similar internal structure work.
Seals perform various tasks:
- the contact of the plate with the seat is responsible for blocking the flow;
- cover gasket - for the tightness of the fixed connection;
- spindle seal - for no leakage outward along the moving part.
Therefore, a wet stem and water passing through a closed gate require different diagnostics.
Changing the direction of flow in the housing creates hydraulic resistance. It is taken into account in the calculation of the pipeline. It is forbidden to tighten the flywheel with an extension pipe: excessive force damages the thread and sealing surfaces.
Three-way valve versions UKSPAR
For preliminary selection, it is convenient to compare valves by body, seal and nominal pressure. The final suitability is determined by the passport of a specific size: a single series name does not replace technical data.
Fig.V101 — cast iron flanged bellows valve PN16
The feature of Fig.V101 is the bellows seal of the spindle. The metal corrugated element changes length with the movement of the stem and separates the medium from the outside air. The UKSPAR card states PN16, maximum temperature up to +350 °C and application for water, steam and oil. These limit values must be checked in the permissible combination.
For a site with demanding conditions bellows shut-off valve are selected taking into account the cyclicity. Such a shut-off valve has a limited resource of bellows strokes; the opening frequency is agreed in advance.
Fig.V103 — cast iron flanged shut-off valve, disc-nzh, PN16
The Fig.V103 model has a cast iron body. UKSPAR specifies PN16, temperature up to +300 °C and media «water, steam, oil, petroleum products». Compatibility with a specific substance is checked by its composition and temperature.
For the project cast iron valve for pipeline are also selected according to the design of the plate. Our catalog page indicates EN-1.4021 / EN-GJS400-15; the composition of the assembly for the required DN is specified according to the drawing.
Fig.V113 — flanged steel shut-off valve, disc-nzh, PN40
Fig.V113 has a body made of EN-1.0025 steel, a plate made of EN-1.4021 stainless steel and PN40. This is an option for applications where a steel body and a higher pressure rating are required. The maximum temperature is up to +425 °C, but the permissible pressure for it is checked separately.
In responsible areas flanged steel valve must also comply with the parameters of flanges, gaskets and fasteners. A stronger body does not compensate for a weaker adjacent part. The list of UKSPAR media includes water, steam, gas, oil and petroleum products; specific applications are agreed on the passport.
Bellows seal vs. stuffing box seal: what's the difference?
In the stuffing box, the packing surrounds the spindle and is compressed by a clamping piece. During operation, its condition is checked, and the need for maintenance is determined according to the instructions. If the valves operate with hot media, even a small leak near the flywheel becomes a cause of losses and a danger to personnel.
The bellows creates a metal barrier around the stem. It reduces the dependence of external tightness on the condition of the stuffing box, but requires compliance with the permissible stroke and operating mode. In some designs, the stuffing box remains a reserve seal. The presence of such a reserve should be confirmed by documentation, as well as the type of seal Fig.V103 and Fig.V113.
Cast iron or steel: how the housing material affects the application
For compatible media and permissible operating conditions, cast iron valves can be a practical solution. However, different grades of cast iron have different properties. Similarly, a steel body should be evaluated for a specific grade and design parameters.
Carbon steel offers other options for temperature and mechanical loads, but is also subject to corrosion. Stainless steel in the plate increases the resistance of this particular part in the compatible environment. It does not automatically protect the housing, mounting or spindle. For aggressive fluids, all wetted materials and gaskets are tested, including their resistance at operating temperature.
PN16 or PN40: when a working pressure reserve is needed
The PN designation characterizes the nominal pressure class. To ensure that the shut-off valve can withstand the pressure in a given mode, it is checked according to the manufacturer's pressure-temperature diagram. PN16 does not guarantee 16 bar at any temperature.
The valve drop, starting modes, and water hammer are taken into account. If there are problems with switching or condensate accumulation, the operating mode and pipeline diagram are corrected.
Comparison table of three valve options
The table shows UKSPAR data.
| Parameter | Fig.V101 | Fig.V103 | Fig.V113 |
| Corps | Cast iron | Cast iron EN-GJS400-15 | Steel EN-1.0025 |
| Nominal class | PN16 | PN16 | PN40 |
| Maximum on the card | +350 °C | +300 °C | +425 °C |
| Feature | Bellows seal | Cast iron body, plate with stainless steel component | Steel body, no plate |
| Accession | Flanged | Flanged | Flanged |
When comparing valves, check the installation length, DN and design of the connecting surfaces. Matching nominal diameter does not guarantee interchangeability.
Areas of application: water, steam, heating, industrial environments
In water supply and heating, such fittings cut off areas for maintenance. In steam lines, requirements are added for heating, condensate drainage and seal stability. For industrial environments, its precise composition and characteristics are required.
The valves are mounted on the pipeline taking into account the flow direction arrow and the permitted spindle position. Leave room for a hand near the handwheel, and for maintenance above the cover. The flanges must converge without forcibly tightening the skewed pipes. Otherwise, the new fittings will operate under excessive mechanical load from the first day.
How to choose the right valve design
Start with working data that you can pass on to the supplier and check against the passport:
- composition of the medium, operating and maximum temperature;
- working pressure, possible jumps and drop at the gate;
- DN, installation length and flange parameters;
- switching frequency and external tightness requirements.
According to this data, the shut-off valve is selected individually: Fig.V101 - for the bellows version, Fig.V103 - for compatible modes of the cast iron model PN16, Fig.V113 - for the steel body PN40. Next, the passport and the complete set are checked. This is faster than reworking the finished unit due to a missing characteristic.
