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Brand: Cla-Val
Cla-Val Series 34 Air Release Valve, 1/2 to 3 in
Description
Venting air at pipeline high points before it can collect
The Cla-Val Series 34 air release valve vents entrained air that collects at high points in a pipeline. It continuously releases small quantities of air before large pockets can form. Cla-Val explains why this matters: accumulating air slowly cuts flow capacity and raises power consumption, and large air pockets greatly increase the pressure surges that occur when flow stops and starts, which can end in pipeline rupture.
The body is ductile iron with stainless steel trim and float. The valve is easily serviced without removal from the pipeline and is engineered for a drip-tight seal at low pressures, with working pressures up to 800 psi.
Technical specifications
| Parameter | Specification |
|---|---|
| Model | Cla-Val Series 34 air release valve (float-operated, simple or compound lever) |
| Inlet sizes | 1/2, 3/4, 1, 2, 3 in NPT |
| Pressure ratings | 150, 175, 300, 600 and 800 psi, depending on orifice and model |
| Body and cover | Ductile iron ASTM A536 65-45-12 |
| Float, internal parts | Stainless steel |
| Seal | Viton or Buna-N, standard |
| Temperature | Water to 180 °F |
| Orifice and MWP, Figure A | 3/32 in at 175 psi; 1/16 in at 300 psi (inlet 1/2, 3/4, 1 in; pipeline flow 200 to 2,200 gpm) |
| Orifice and MWP, Figure B | 3/16 in at 150 psi; 5/32 in at 300 psi; 3/32 in at 600 psi (inlet 1, 2 in; 2,200 to 15,000 gpm) |
| Orifice and MWP, Figure C | 3/8 in at 150 psi; 7/32 in at 300 psi (inlet 2, 3 in; 15,000 to 50,000 gpm) |
| Orifice and MWP, Figure D | 7/32 in at 500 psi; 1/8 in at 800 psi (inlet 2 in; 2,200 to 50,000 gpm) |
| Dimensions (Figures A to C) | 5-7/8 x 3-3/4 in, 6 lb (A); 10 x 7 in, 20 lb (B); 12-1/2 x 9-1/2 in, 45 lb (C) |
Operation, installation and sizing
During normal operation, air accumulating at the high point displaces liquid in the valve and lowers the level relative to the float. When the float is no longer buoyant it drops and opens the orifice seat, exhausting air to atmosphere. After the air is released the level rises, the float closes the orifice, and the cycle repeats.
The valve should be mounted vertically on top of the pipeline, with an isolation valve below each unit for servicing and a vault with adequate air venting and drainage. On uniform-grade line, Cla-Val suggests units at regular intervals of approximately half a mile. A vacuum check valve can be supplied on the discharge to prevent air re-entry under negative pressure. Because the Series 34 mainly releases pockets as they develop, the exact volume of air does not have to be determined; the sizing chart is based on venting capacity.
Choosing the orifice and model
The orifice diameter must suit the operating pressure range, and the order should state any operating pressure below 10 psi. The datasheet chart is arranged by body figure. Figure A (models 3450, 3475 and 3410 with inlet 1/2, 3/4 or 1 inch and 1/2 inch outlet) uses a 3/32 inch orifice at 175 psi or a 1/16 inch orifice at 300 psi, with the first listed UL and FM approved. Figure B (1 and 2 inch inlet) offers 3/16 inch at 150 psi, 5/32 inch at 300 psi and 3/32 inch at 600 psi. Figure C (2 and 3 inch inlet, 1 inch outlet) offers 3/8 inch at 150 psi and 7/32 inch at 300 psi, and Figure D (2 inch inlet) offers 7/32 inch at 500 psi and 1/8 inch at 800 psi.
Documents and quotation
The engineering data sheet for the Series 34 is attached, including the venting capacity graph and purchase specification wording based on ANSI/AWWA C512. State the pipeline flow, pressure range, inlet size and model number when requesting a quotation. See also the Cla-Val 33A combination valve and other valves under Fittings & Valves.
Datasheets & Documents
- Datasheet Cla-Val Series 34 Air Release Valve Engineering Data Sheet E-34 Series (manufacturer) Download
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About brand
Cla-Val is an American manufacturer of automatic control valves for water distribution, fire protection, aviation fuelling and industry. It was founded in 1936 in South Pasadena, California, with five employees, introduced the industry's first hydraulically actuated globe valve in the late 1930s, and moved to its present headquarters in Costa Mesa, California, in 1954. The company has been led by three generations of the same family.
Cla-Val company profile
| Founded | 1936, South Pasadena, California, USA |
|---|---|
| Headquarters | Costa Mesa, California, since 1954, with in-house foundries |
| Ownership | Family-led for three generations |
| Technology | Hydraulically operated, diaphragm-actuated globe and angle main valves controlled by pilot systems |
| Product families | 100-01 Hytrol main valve, pressure reducing, pressure relief and sustaining, level and float control, check and surge anticipating valves, air release valves, aviation fuelling valves |
Milestones
- 1936: Cla-Val starts in South Pasadena with five employees.
- Late 1930s: Cla-Val introduces the first hydraulically actuated globe valve in its industry.
- 1954: The company moves to Costa Mesa, still its worldwide headquarters.
Control valve and air valve range
The range is built around the Hytrol 100-01 main valve. Pilot systems on that body create pressure reducing and sustaining valves such as the 90-01 and 92-01, rate of flow valves, solenoid valves, pump control valves, check valves, and altitude and level control valves. Cla-Val also lists air release and vacuum valves and silent or two-door wafer check valves, each with an engineering data sheet that gives sizes, materials and pilot ranges.
Markets and materials
Cla-Val addresses waterworks, fueling, marine, mining and industrial applications. Its data sheets state that valves are manufactured in more than 50 different alloys, with ductile iron, cast steel and bronze as the standard body materials and fusion-bonded epoxy coating as an option.
Sourcing through Seven Star LLC
Seven Star LLC is an independent supplier in Muscat and quotes Cla-Val valves against the model number, size, pressure class, materials and pilot settings shown in the data sheet.
Cla-Val products we list
Facts checked against Cla-Val's own company pages (cla-val.com), October 2026.
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Frequently Asked Questions
What does the Cla-Val Series 34 do?
It automatically vents small quantities of entrained air at pipeline high points, so large air pockets do not form.
What pressure ratings are listed?
150, 175, 300, 600 and 800 psi, depending on the orifice size and valve figure.
How should the valve be mounted?
Vertically on top of the pipeline, with an isolation valve below it and a vault with adequate venting and drainage.
Can air re-entry be prevented?
Yes. Vacuum check valves can be supplied on the discharge of all sizes to stop air re-entering during negative pressure.
What happens below 10 psi?
The datasheet asks that operating pressure below 10 psi be specified when ordering so a suitable orifice is selected.
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