Relief Valve DN15/0

Export-Ready for Water Transmission & Municipal Projects Worldwide

origin Mumbai (JNPT) | CIF worldwide | AWWA C512 compliant | SS304 floats

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Air Relief Valve — DN150 Two-Chamber Double Flange

Supreme Valves India manufactures two-chamber combination air relief valves (also called kinetic air valves or combination air valves) in sizes DN50 to DN300 with double flange connections. The DN150 two-chamber air relief valve combines an air relief chamber (large orifice for filling/draining) and a vacuum relief chamber (large orifice for vacuum protection) in a single cast iron body. It is installed at high points in water transmission mains to automatically: (1) Release accumulated air during pressurized operation to prevent headloss and flow restriction; (2) Admit air during pipeline draining to prevent vacuum formation that could collapse the pipe; (3) Discharge large air volumes during filling and draining operations. The double flange design allows controlled discharge of air/water mixture to a collection gutter. Standard with SS304 floats and EPDM seat seals for bubble-tight closure in water service.

How the Two-Chamber Air Relief Valve Works

Air Relief Chamber

When accumulated air pushes the water level down in the air relief chamber, the float drops and opens the large orifice. Compressed air escapes through the discharge outlet. When water rises, the float lifts and seals the orifice. This cycle repeats automatically during pipeline operation, preventing air pockets from restricting flow.

Vacuum Relief Chamber

When the pipeline pressure drops below atmospheric (vacuum condition), water drains from the vacuum relief chamber, causing its float to fall and open the vacuum breaker orifice. Atmospheric air rushes in through the inlet to equalize pressure, preventing pipe collapse. The vacuum relief chamber closes automatically once the pipeline refills.

Materials of Construction (MOC)

Component Material Specification
Body & Bonnet Ductile Iron (ASTM A536 / EN-GJS-400-15)
Stem / Spindle SS 410 / SS 420
Seat / Trim EPDM / NBR / Bronze

Technical Specifications

Parameter Specification / Standard
Manufacturing / Design Standard EN 1171 / AWWA C509 / BS 5163
Testing Standard API 598 / EN 12266-1
Pressure Rating PN16 / PN25

Frequently Asked Questions

What does a two-chamber air relief valve do?

A two-chamber air relief valve combines two functions in a single valve body: (1) Air Relief Chamber — automatically releases accumulated air from a water pipeline during operation. When air collects in the upper chamber (due to being denser than water), the float drops, opening the air release orifice. Compressed air escapes to atmosphere, and the float then rises to close the orifice once water fills the chamber. (2) Vacuum Relief Chamber — prevents vacuum formation (negative pressure) inside the pipeline. When the pipeline drains or experiences rapid shutdown, vacuum can form as water column separates. The vacuum relief chamber opens to admit atmospheric air into the pipeline, preventing pipe collapse, infiltration of contaminated water through joints, and protection of downstream equipment. The DN150 two-chamber valve is the standard size for DN300–DN600 trunk mains.

Why is a two-chamber design better than two separate valves?

A combined two-chamber air relief/vacuum relief valve offers three advantages over installing separate air release valve and vacuum breaker valves: (1) Single body, single flange connection to the pipeline — reducing installation cost and potential leak points by half; (2) Space savings — critical in chambers with limited headroom (e.g., under highway crossings); (3) The two chambers work independently inside a shared cast body, so one function can operate while the other is sealed. This is the standard specification for water transmission projects globally. For DN150 connection to DN300–DN600 mains, the two-chamber valve is the most cost-effective and hydraulically efficient solution.

What is a 'double flange' air relief valve and when is it required?

A double flange air relief valve has flanges on both the inlet (pipeline connection) and outlet (discharge) sides of the body. The inlet flange connects to the pipeline air chamber or tee. The outlet (discharge) flange directs the discharged air/water mixture to a collection gutter or drainage channel. Double flange valves are used where the discharge must be captured and channeled away — particularly in pressurized pipelines where the discharged air could otherwise spray or cause flooding in a chamber. Single flange valves (with a threaded discharge port) are used where discharge can drip freely. For DN150 trunk mains in municipal water projects, double flange is the standard specification.

What causes air to accumulate in water transmission pipelines?

Air enters water pipelines through several mechanisms: (1) Dissolved air coming out of solution when water temperature increases or pressure decreases along the pipeline profile; (2) Air pockets formed during pipeline filling or emptying procedures; (3) Air drawn in through joints and seals when vacuum forms; (4) Air intentionally or accidentally introduced during maintenance (pigging, filling operations). Air pockets reduce effective pipe cross-section (causing headloss and reduced throughput), cause water hammer when they pass through valves or fittings, can cause corroded pipe surfaces above the waterline, and in extreme cases can block flow entirely at high points. Air relief valves at high points are essential for efficient pipeline operation.

What is the difference between an air release valve and an air relief valve?

The terms are often used interchangeably, but there is a technical distinction: (1) Air Release Valve (ARV) — has a small orifice (2–6mm) that releases small volumes of compressed air during pressurized pipeline operation. It operates when the pipeline is under pressure, releasing air that has come out of solution. (2) Air Relief Valve (also called Air Vent Valve) — has a larger orifice that opens when the pipeline is being filled or drained, releasing or admitting large volumes of air at low pressure. The two-chamber design combines both functions: the small-orifice chamber handles continuous air release during operation; the large-orifice chamber handles filling/draining and vacuum relief. Some specifications call the combination 'Kinetic Air Valve' or 'Combination Air Valve'.