Balanced Piston Valves
A balanced piston valve is a flanged piston valve that counters the line pressure acting on the piston through a balancing arrangement inside the body, lowering the force needed to turn the handwheel. Thanks to this pressure balancing, sizes from DN65 to DN200 can be opened and closed comfortably by hand even under high differential pressure.
The stem rises without rotating; a stroke indicator shows the valve position from outside and bearing-mounted guidance reduces the handwheel torque further. It is offered in two pressure classes, grey iron PN16 and ductile iron PN40, with EN 1092-2 flanges and EN 558 Series 1 face-to-face.
Main Applications
- Main steam boiler outlet valve
- Main branches of steam distribution headers
- Large-bore superheated water and hot water lines
- District heating main supply lines
- Main process steam distribution lines
Technical Data
| Design | Pressure-balanced piston, rising non-rotating stem |
|---|---|
| Size range | DN65, 80, 100, 125, 150, 200 |
| Pressure class | PN16 (grey iron) · PN40 (ductile iron) |
| Temperature | PN16: −10 / +300 °C · PN40: −20 / +350 °C |
| Pressure–temperature (PN40) | 40 bar / 120 °C · 32 bar / 300 °C · 28 bar / 350 °C |
| Connection | Flanged, EN 1092-2 |
| Face-to-face | 290 mm (DN65) · 310 · 350 · 400 · 480 · 600 mm (DN200) |
| Height when open (H) | 395 mm (DN65) … 695 mm (DN200) |
| Handwheel diameter | 260 mm (DN65–80) · 300 mm (DN100) · 350 mm (DN125) · 400 mm (DN150–200) |
| Kv value | 70 · 105 · 165 · 255 · 360 · 590 m³/h (DN65 → DN200) |
| Weight | PN16: 23.8 kg (DN65) … 181 kg (DN200) · PN40: 25.3 … 190 kg |
| Lubrication | 3/8″ grease nipple on the bonnet |
Material Options
| Part | PN16 · grey iron body | PN40 · ductile iron body |
|---|---|---|
| Body | Grey iron EN-GJL-250 (5.1301) | Ductile iron EN-GJS-400-18-LT (5.3103) |
| Bonnet | Grey iron EN-GJL-250 (5.1301) | Ductile iron EN-GJS-400-18-LT (5.3103) |
| Balanced piston | Stainless 1.4086 / 1.4104 | Stainless 1.4086 / 1.4104 |
| Piston bush and washer | Stainless 1.4021 (AISI 420) | Stainless 1.4021 (AISI 420) |
| Stem | Stainless 1.4021 (AISI 420) | Stainless 1.4021 (AISI 420) |
| Lower / upper ring | Graphite T1 / graphite T1 | Graphite T1 / graphite T1 |
| Autoseal ring | Graphite T3 | Graphite T3 |
| Stem bush | Brass Ms58 | Brass Ms58 |
| Bearing | Alloy steel rolling bearing | Alloy steel rolling bearing |
| Lantern and handwheel | Grey iron 5.1301 | Grey iron 5.1301 |
| Stud / nut | Steel 5.6 / 5.2 | Steel 5.6 / 5.2 |
Which class? On saturated steam lines up to 16 bar and superheated water lines below 300 °C, grey iron PN16 is sufficient. On boiler outlets above 16 bar and superheated steam lines up to 350 °C, ductile iron PN40 should be selected. On large-bore lines, remember to absorb thermal expansion with metal bellows expansion joints.
Advantages
Low Handwheel Force
- The balancing arrangement reduces the pressure load on the piston.
- Large sizes are operated by hand without a gearbox.
Visible Position
- The stroke indicator shows the opening from outside.
- Open or closed status can be seen from a distance.
Non-Rotating Stem
- The stem moves only axially.
- Less wear on packing and rings.
Bearing Support
- Alloy steel bearing at the stem nut.
- Low torque with frequent operation.
High Kv
- Flow coefficient of 590 m³/h at DN200.
- Low pressure drop on main lines.
Construction and Design Features
- Pressure-balancing piston and piston bush
- Self-sealing graphite T3 autoseal ring
- Non-rotating rising stainless stem and brass stem bush
- Bearing-mounted stem nut and stroke indicator
- Travel stop segment and safety nut
Send the line size, pressure class, steam or water temperature and differential pressure through the Request a Quote form; we will quote the right balanced piston valve together with the flange set.
How to Choose?
- Determine the differential pressureCalculate the pressure difference across the closed valve.
- Choose the pressure classMove to ductile iron PN40 above 16 bar and 300 °C.
- Verify the size against KvCheck the pressure drop for the main line flow in the Kv table.
- Check the installation heightLeave room for the open-position H dimension and the handwheel diameter.
- Plan hangers and supportsPrepare pipe supports for the 94–190 kg weight of DN150–DN200.
Complementary Products
Why ORFA?
Other Piston Valves
Our Balanced Piston Valves
ORFA supplies balanced piston valves in a range of pressure classes, sizes and connection types to suit your application. Descriptions, technical specifications, materials and dimension tables are available on each detail page.
Get a quote for your project
Our sales team will prepare the best solution for your needs.