Excess pressure regulator / back pressure sustaining valve - PREDEX | ARI

ARI-PREDEX® – Inlet Pressure Retaining Valve

The ARI-PREDEX® is a self-acting, straight-through pressure relief valve designed for upstream pressure regulation. It opens when the inlet pressure exceeds the set value and closes when the pressure falls below the set point, operating without auxiliary energy.

Technical Specifications

• DN 15–150
• PN 16, PN 25, PN 40
• Inlet pressure range: 0.2–16 barg
• Body materials: EN-JL1040, EN-JS1049, 1.0619+N
• Flanges according to DIN EN 1092-1/-2
• Face-to-face according to DIN EN 558
• Kvs: 3.2–280 m³/h, with reduced Kvs options for smaller diameters
• Leakage class I according to DIN EN 1349 / EN 60534-4
• Seat with metal or soft PTFE sealing up to 200°C

Media and Operating Conditions

Suitable for Group II fluids according to PED 2014/68/EU: steam, neutral gases, vapors, and liquids. For temperatures exceeding diaphragm limits, a water-sealed vessel is required in the impulse line. Actuator diaphragms available in EPDM up to 110°C and NBR up to 100°C.

Selection and Installation

Selection is based on set pressure, flow rate, Kvs, PN, body material, and temperature. In overlapping pressure ranges, the smaller range is preferred for reduced regulation deviation. Upstream pressure tapping should be placed at a distance of 10 × DN or at least 1 m before the valve. A filter is recommended before the valve, along with upstream/downstream pressure gauges and a safety valve sized for the full source flow.

Applications

• Steam and condensate networks
• Protection of pumps, compressors, and exchangers from pressure increase
• Bypass lines in boilers or thermal stations
• Industrial liquid and neutral gas lines

FAQ

Does it require instrument air or electrical signal?
No. The valve operates mechanically via upstream pressure and spring.

What affects sealing integrity?
Contaminants, welds, and blocked control lines can cause leakage or unstable regulation. Regular filter cleaning and impulse line inspection are advised.