SMC VXZ230AA 2-Port Zero Differential Pressure Solenoid Valve

A zero-differential 2-port valve for air lines

VXZ230AA is a normally closed, pilot-operated 2-port solenoid valve from the SMC VXZ2 series in the For Air version. The VXZ is a zero differential pressure type: its minimum operating pressure differential is 0 MPa, so it opens even when the pressure on both sides is almost equal, which an ordinary pilot-operated 2-port valve needing a pressure differential cannot do. That matters on low-pressure compressed-air lines, vacuum-side duties (the catalogue says it can be used with low vacuum up to 133 Pa abs) and blow-down circuits.

The code VXZ2 3 0 A A decodes as: 3 means size 10A with N.C. valve type (A would be N.O.), 0 is the fluid code for air, the first A is an aluminum body with Rc 1/4 and a 10 mm orifice, and the final A is 24 VDC with a grommet electrical entry. Other final letters give 100, 200 or 230 VAC, DIN terminal, conduit and other entry styles. The catalogue lists seal material NBR, coil insulation Class B and Rc thread as common specifications.

Technical specifications

Choosing between zero-differential and ordinary pilot valves

A pilot valve normally uses the line pressure drop across the main seat to help lift the diaphragm, so it needs a minimum pressure differential. The zero-differential VXZ uses a different pilot arrangement and works at zero differential, but the catalogue notes that the operation of the valve may be unstable if the pressure supply source, such as a pump or compressor, has too small a capacity or if the pressure loss through the piping orifice is too large. In those cases the required valve size must be re-checked with SMC.

For a fixed pressure differential well above 0 MPa an ordinary pilot-operated valve from the same maker may be a more economical choice, while the VXZ avoids any risk of the valve failing to open at low differential.

Installation and wiring options

Valves are sealed with NBR (FKM is an optional seal material under other special options, with EPDM and low-concentration ozone-resistant versions also listed). The catalogue lists voltages of 24 VDC and 100, 110, 200 and 230 VAC across grommet, DIN terminal, conduit terminal, conduit and flat terminal entries, plus special voltages 12 VDC, 24, 48, 220 and 240 VAC. Brackets are available as an option.

Mount the valve with the coil upward, not downward, as the catalogue requires, support the piping so no load acts on the valve body, and fit a strainer upstream if the line carries scale or dust. Keep the dew point at -10 deg C or less as the catalogue specifies, particularly for air systems that cool the line below ambient.

Documents and quotation

The SMC VXZ catalogue linked at the end of this page covers air, water, oil, heated water and high-temperature-oil versions with how-to-order pages, flow data and dimensions. Please confirm fluid, voltage, entry type and options before ordering. For other valves see Solenoid Valves. Seven Star LLC is an independent supplier and quotes the exact code on request.

How the VXZ230AA Works

The VXZ series uses a diaphragm main valve controlled by a small pilot orifice, with an additional lift spring that makes zero-differential operation possible. The catalogue working principle describes three stages:

• De-energised: air enters from the IN side through the supply orifice and fills the pressure action chamber above the diaphragm. The main valve is held closed by the pressure in this chamber and by the return spring.
• Energised, pilot open: the coil attracts the armature, which opens the pilot orifice. Air in the pressure action chamber escapes to the OUT side through the pilot orifice.
• Energised, main valve open: as the chamber pressure falls, the force pushing the diaphragm down drops below the force pushing it up, and the main valve opens. The lift spring opens the main valve even when the pressure on the IN side is 0 MPa or very low.

Because the VXZ230AA is a normally closed valve, flow from port 1 to port 2 is blocked when the coil is off. The catalogue points out that if the pressure at port 2 becomes higher than at port 1, the valve cannot block the reverse flow; where reverse pressure is possible, fit a check valve downstream.

VXZ230AA Ordering Code Explained

The VXZ how-to-order page for air (single unit) uses exactly this code as its example, so each character of VXZ230AA can be confirmed:

Special options such as FKM or EPDM seals, oil-free treatment, G or NPT threads, a bracket, a DIN connector with light or a different entry direction are added as suffixes; refer to the special-options pages of the catalogue. Our team can help confirm the correct ordering code if you are replacing a valve with a worn or missing nameplate.

Installation & Maintenance

• Install an air filter close to the valve on its upstream side and drain it periodically. The catalogue recommends replacing filter elements after one year of use, or earlier if the pressure drop reaches 0.1 MPa.
• Do not apply external force to the coil; tighten with a wrench on the piping connection parts.
• Secure the valve with brackets except when it is held by steel piping and copper fittings.
• Do not cover the coil with heat insulation; freeze protection should be applied to the piping and body only.
• Keep the voltage within ±10% of 24 VDC. Switch the valve at least once every 30 days and carry out a regular inspection every six months.
• Below a differential of 0.01 MPa, operation may become unstable with low flow, many elbows and tees, or small nozzles at the end of the line. Consult SMC in these cases.

Typical Applications in Oman & the GCC

The VXZ230AA is used where an air line must open reliably at low or zero differential pressure: blow and purge lines, air supply to tanks or receivers that start at atmospheric pressure, low-pressure air knives, dust-collector and conveying auxiliaries, and low-vacuum lines down to 133 Pa abs. Typical users in Oman and the GCC include packaging and food plants, water treatment and desalination facilities, building services and general machine builders. Its IP65-equivalent enclosure (flat terminal is IP40) helps in dusty plant rooms, but hot and humid sites still need dry air within the –10 °C dew point specification.

Why Source from Seven Star LLC

Seven Star LLC supplies SMC 2-port process valves, including the VXZ series, across Oman and the GCC. Send the full code (for example VXZ230AA, or VXZ230BA for the 3/8 aluminium body) with quantity and any special options, and request a quote. Our team can help confirm the correct ordering code for your fluid, voltage and electrical entry.