VMU High Purity Metering Valve
Fine taper metering stem with Cv 0.019 for low-flow carrier gas, calibration and analyser sample lines.
Built for ultra high purity specialty gas service, the VMU belongs to the Metering & Needle Valves family covering isolation, switching and flow control.
VMU High Purity Metering Valve overview
The VMU is a high purity specialty gas valve specified with 1/4, 1/2, 6mm ports, a flow coefficient of metering stem 0.019, regulating stem 0.30 and a maximum working pressure of 700 PSI. Fine taper metering stem with Cv 0.019 for low-flow carrier gas, calibration and analyser sample lines. It is intended for the point in a high purity gas system where a clean, repeatable shut-off or switching function is needed without introducing a packed stem seal into the process stream.
The wetted flow path is kept short and smooth, with a metal or hard-polymer sealing element selected for the gas. Seats and closures are machined to a controlled finish so the valve can be purged quickly and will not hold up moisture between process cycles. A short, smooth flow path and low internal volume make purge cycles fast, which matters when a line changes between reactive gases. Available end connections are vcr face seal (male/female), butt weld, compression, socket weld, so the same body can be used on face-sealed tool hook-ups, welded distribution headers or field-installed instrument lines.
Key features and design benefits
- 1/4, 1/2, 6mm ports, Cv metering stem 0.019, regulating stem 0.30 — sized for high purity metering valve Cv 0.019 flow duty without excess dead volume
- 700 PSI maximum working pressure with a reinforced seat and helium-tested pressure envelope
- The wetted flow path is kept short and smooth, with a metal or hard-polymer sealing element selected for the gas.
- Electropolished wetted surfaces for fast dry-down and low moisture retention
- Manual or normally closed pneumatic actuation; pneumatic versions fail closed on loss of instrument air
- VCR, butt weld, compression or cylinder-standard end connections to match the installation
- Cleanroom assembly, double-bag packaging and per-valve leak records available
Technical specifications
| Port size | 1/4, 1/2, 6mm |
|---|---|
| End connections | VCR face seal (male/female), butt weld, compression, socket weld |
| Cv | metering stem 0.019, regulating stem 0.30 |
| Max working pressure | 700 PSI |
| Model code | VMU |
| Product family | Metering & Needle Valves |
| Body material | 316L VIM/VAR stainless steel, low inclusion |
| Sealing element | Metal seat with PCTFE / PTFE or hard-polymer sealing element by gas |
| Wetted surface finish | Electropolished, typical Ra 0.25 um (10 uin) or better |
| Leak testing | Helium mass spectrometer, inboard and across seat; typical 1 x 10^-9 mbar l/s |
| Operating temperature | Typical -10 C to +80 C manual, -10 C to +65 C pneumatic |
| Actuation | Manual handwheel or normally closed pneumatic, 60-90 PSI instrument air |
| Cleanliness | Cleaned, dried and assembled for ultra high purity gas service |
| Packaging | Cleanroom double-bag, sealed for installation |
| Documentation | Material certificate, helium leak record, certificate of conformance |
Values above describe the standard configuration of model VMU. Final materials, seat, actuation, test limits and certification are confirmed on the order-specific datasheet issued with your quote.
Model comparison within the Metering & Needle Valves family
Select the body by flow demand rather than by port size alone. The table below compares the VMU with its sibling models on the three parameters that drive a gas system design: port size, flow coefficient and maximum working pressure.
| Model | Port | Cv | Max. pressure |
|---|---|---|---|
| VMG | 1/4, 1/2, 6mm | metering stem 0.019, regulating stem 0.30 | 700 PSI |
| NV | 1/4, 3/8, 1/2 | - | - |
Construction and wetted materials
The wetted flow path is kept short and smooth, with a metal or hard-polymer sealing element selected for the gas. Seats and closures are machined to a controlled finish so the valve can be purged quickly and will not hold up moisture between process cycles. For the VMU, the wetted path is machined from 316L VIM/VAR stainless steel with low inclusion and controlled sulfur content, then electropolished. A nickel-based diaphragm or seat alloy can be substituted where halide or hydride gases demand it.
| Component | Standard specification |
|---|---|
| Body | 316L VIM/VAR stainless steel bar stock |
| Wetted finish | Electropolished, typical Ra 0.25 um (10 uin) or better |
| Sealing element | Metal seat with PCTFE / PTFE or hard-polymer sealing element by gas |
| Actuator | Manual handwheel or normally closed pneumatic piston, 60-90 PSI supply |
| Process connection | VCR face seal (male/female), butt weld, compression, socket weld |
End connections and port options
The VMU is normally ordered with 1/4, 1/2, 6mm ports. Connection choice affects both cleanliness and maintainability: VCR face seals give a repeatable metal-to-metal seal for tool hook-up, orbital butt welds suit permanent high purity headers, and compression fittings are used where a line must be assembled in the field.
| Parameter | Available option |
|---|---|
| Standard port | 1/4, 1/2, 6mm |
| End connections | VCR face seal (male/female), butt weld, compression, socket weld |
| Seal standard | VCR face seal / orbital butt weld / compression / CGA or DISS for cylinder service |
| Actuation | Manual, or normally closed pneumatic with 60-90 PSI instrument air |
| Optional documentation | Material certificate, helium leak record, certificate of conformance |
Gas compatibility and typical applications
Model VMU is selected for high purity N2, Ar, He, H2, O2, and corrosive hydride or halide mixtures when the wetted alloy is matched to the gas. Always state concentration, temperature and any moisture or oxygen limit so the wetted alloy and seat can be confirmed before release.
- Semiconductor tool hook-up and gas cabinet isolation branches
- Valve manifold boxes, changeover panels and purge / vent legs
- High purity laboratory, analytical instrument and calibration gas lines
- Photovoltaic, MOCVD and hydrogen distribution systems
- Related application guides:
- MOCVD & LED Process Gas
- Laboratory & Analytical Instrument Gas
Installation, purging and handling
Install the VMU with the flow direction and port orientation shown on the approved drawing. Keep the protective caps in place until the joint is made, tighten face-seal fittings to the specified torque, and purge with dry inert gas before introducing process gas. Because the internal volume is low, a short cyclic purge is normally enough to reach the required moisture level.
- Handle with clean gloves in a controlled area; do not open the double bag until installation
- Use orbital welding or certified face-seal glands on high purity headers
- Purge with dry N2 or Ar and verify moisture / oxygen upstream before process gas
- Helium leak check the assembled joint, then the inboard and across-seat envelope
- Record the serial number, leak result and gas service in the system dossier
Ordering and configuration
Quote the model code and the options below. Where a gas is corrosive or pyrophoric, include the concentration so the diaphragm or seat alloy can be matched to the service.
| Ordering parameter | Your selection |
|---|---|
| Base model | VMU — VMU High Purity Metering Valve |
| Port size | 1/4, 1/2, 6mm |
| End connection | VCR face seal (male/female), butt weld, compression, socket weld |
| Actuation | Manual handwheel / normally closed pneumatic (60-90 PSI) |
| Wetted alloy | 316L VIM/VAR standard, nickel-based alloy by gas compatibility |
| Documentation | Material certificate, helium leak record, CoC (state if required) |
Ready to specify the VMU?
Send the gas, pressure, flow and connection details — we will confirm the model, materials and lead time.
Related models and alternatives
Other valves in the Metering & Needle Valves family and adjacent groups that may suit a different Cv, pressure or port requirement.
VMGVMG Precision Metering Valve
- Port size1/4, 1/2, 6mm
- Max. pressure700 PSI
- Cvmetering stem 0.019
NVNV High Purity Needle Valve
- Port size1/4, 3/8, 1/2
- Max. pressureOn request
- CvOn request
VB-HPVB-HP Bellows Sealed Valve
- Port size1/4, 3/8, 6mm, 8mm
- Max. pressure350 PSI
- Cv0.3
VB8VB8 Low Pressure Bellows Sealed Valve
- Port size1/2, 3/8, 10mm, 12mm
- Max. pressure500 PSI
- Cv0.80
VB4VB4 Low Pressure Bellows Sealed Valve
- Port size1/4, 3/8, 6mm, 8mm
- Max. pressure500 PSI
- Cv0.3
Frequently Asked Questions
What are the key specifications of the VMU?
The VMU is supplied with 1/4, 1/2, 6mm ports, a maximum working pressure of 700 PSI and a Cv of metering stem 0.019, regulating stem 0.30. End connections are vcr face seal (male/female), butt weld, compression, socket weld. The full specification table on this page lists materials, leak testing, actuation and cleanliness requirements.
Is the VMU suitable for corrosive or toxic specialty gases?
It is used with high purity N2, Ar, He, H2, O2, and corrosive hydride or halide mixtures when the wetted alloy is matched to the gas. Compatibility depends on the wetted alloy and the sealing element, so state the gas and concentration when requesting a quote and we will confirm the material selection.
How is the VMU actuated and what is its safe state?
Standard configurations are a manual handwheel or a normally closed pneumatic actuator with 60-90 PSI instrument air. Pneumatic versions close on loss of air, which is the required safe state for most gas cabinet and tool hook-up isolation points.
How do I order the VMU?
Quote model VMU together with the gas list, operating pressure, required Cv, port size, end connection and actuation. Material certificates, per-valve helium leak records and a certificate of conformance can be supplied with the order.