Atmospheric valve · Pressure and vacuum
ALPER atmospheric valves
Pressure and vacuum
Single- and double-regulation atmospheric valves that let air into or out of sealed vessels. With a double spring, they set vacuum and positive pressure separately, within very small pressure ranges.
- Sizes½″ to 4″ threaded · DIN flanges
- RegulationSingle (vacuum) or double (pressure/vacuum)
- Positive pressure+0.080 to +8 bar
- Vacuum−0.050 to −0.650 bar
- OpeningProgressive
- Max. temperature280 °C stainless
Questions about the pressure or vacuum setting? Call 933 720 888 or email valfonta@valfonta.com.
- Double spring: vacuum and pressure set separately
- Outlet protected with stainless steel mesh
- Bronze or stainless steel versions
- 90° piped discharge
What ALPER atmospheric valves are used for
They protect sealed vessels by balancing their internal pressure with atmospheric pressure. Single-regulation valves control vacuum only; double-regulation valves also control positive pressure. The outlet has a stainless steel mesh that keeps out impurities. They are part of the Valfonta range of safety valves.
ALPER atmospheric valve technical specifications
| Type | Single-regulation (vacuum) or double-regulation (pressure / vacuum) atmospheric valve |
|---|---|
| Opening | Progressive |
| Positive pressure | From +0.080 to +8 bar |
| Vacuum | From −0.050 to −0.650 bar |
| Discharge | Piped at 90°, with stainless steel mesh |
| Connections | Inlet: BSP male thread or DIN flanges · Outlet: BSP female thread from ¾″ to 4″ (flanges on request) |
| Materials | Hood, base, and plug in RG5 bronze or stainless steel (CF-8M hood, AISI 316L base and plug) |
| Maximum temperature | 280 °C (stainless) |
| Fluids | Liquids, compressed air, inert gases, and steam |
| Other options | AISI 302/316 stainless spring · ANSI inlet flange · NPT thread |
Available figures
| Figure | Regulation | Material | Inlet | Finish |
|---|---|---|---|---|
| 334 | Vacuum | Stainless (bronze hood above 1¼″) | BSP thread ½″–4″ | Natural / polished |
| 335 | Vacuum | Stainless (bronze hood above 1¼″) | DIN flanges DN15–DN100 | Natural / polished |
| 350 | Vacuum | Bronze | BSP thread ½″–4″ | Nickel-plated |
| 351 | Vacuum | Bronze | DIN flanges | Nickel-plated |
| 336 | Pressure / vacuum | Stainless (bronze hood above 1¼″) | BSP thread ½″–4″ | Natural / polished |
| 337 | Pressure / vacuum | Stainless (bronze hood above 1¼″) | DIN flanges DN15–DN100 | Natural / polished |
| 352 | Pressure / vacuum | Bronze | BSP thread ½″–4″ | Nickel-plated |
| 353 | Pressure / vacuum | Bronze | DIN flanges | Nickel-plated |
How they work
- Vacuum breaking. If the internal pressure drops below the vacuum spring setting, the valve opens inward and lets in atmospheric air.
- Pressure relief (double regulation). If the internal pressure exceeds the pressure spring setting, the valve opens outward and releases the excess air or gas.
ALPER atmospheric valve technical documentation
Frequently asked questions about the ALPER atmospheric valve
What is the difference between single and double regulation?
Single regulation (figures 334, 335, 350, and 351) acts only against vacuum. Double regulation (336, 337, 352, and 353) has two springs and also acts against positive pressure.
Where is it installed?
In a vertical position, on top of the tank or pipe. Check periodically that the outlet mesh is clean.
Do they carry CE marking?
No. According to the catalog, none of the atmospheric valve figures carries CE certification.
Other Valfonta safety valves
ALPER safety valveFull, instantaneous opening, up to PN25 and 280 °C.
JAS safety valveFull opening in brass, from ¼″ to ¾″ and PN16.
368–371 safety valveProgressive opening, set pressure from 0 to 16 bar.
Pressure relief valvesS1–S4 and PRV53–55 range, from DN15 to DN150 and set pressure up to 20 barg.
Request a quote for the ALPER atmospheric valve
Give us the details of your tank and we will recommend the right figure and size.
- Tank fluid and temperature
- Set pressure and/or vacuum setting
- Material: bronze or stainless
- Size and connection (threaded or flanged)
You can also call 933 720 888.
