Model 33ATD
Combination Air and Vacuum Valve with
Throttling Air Control Device
Description
DescriptionDesigned to protect pipelines from air lock
and vacuum collapse, the CLA-VAL Model 33ATD Air
Release and Vacuum Breaker Valve eliminates air and
prevents vacuum formation in pipelines. A large venting
orifice and large float clearances freely exhaust or
admits air during pipeline filling or draining.
During normal pipeline operation, air accumulation
and buoyancy cause the floats to lower or lift. As the
water level lowers inside the valve, small amounts of
accumulated air are released through the small orifice.
Once air is released, the patented float poppet system
closes drip tight. Valve servicing is simple because the
entire float poppet system, can be replaced without
removal of the valve body from the pipeline.
Main Valve Features Listings and Approvals
• Automatically Eliminates Air Pockets
• Easily Serviced without removal from pipeline
• Simple, Effective Patented Design
• Corrosion Resistant Internal Parts
Typical Applications
• Vertical Turbine Pumps
• Split Case Pumps
• High Points of Piping Design
Model 33ATD
Combination Air and Vacuum Valve with Throttling Air Control Device
2 Part No. Description
1 33A Body
1 2 TD Throttling Device
4 3 TD Adjustment Screw
4 Float Assembly
Cla-Val Model 33ATD combination air and vacuum valve operates until 2 Series 33ATD is often installed upstream of check valves in
vertical pump discharges to throttle air out during start-up and to allow full air reentry when the pump stops.
Air Release Mode - Valve is normally open: When line is filled or pump started, air is throttled through the air control device TD. As
liquid fills the valve, float ball rises to form a drip-tight closure and remaining air is exhausted through small orifice. Air throttling can be
adjusted by means of adjusting the screw.
Vacuum Prevent Mode: When line pressure drops below positive pressure and the liquid level lowers, the float drops, unseating the
valve and allowing air into the line, thus preventing a vacuum. The spring loaded disc in the TD throttling air control device is moved to
the air intake position due to the negative pressure.
Main Valve Specifications Materials
Optional UL Listed Materials for
UL APPROVED SIZES Main valve body & cover: Seawater and Severe Service
1", 2", 3", 4", 6" Standard Epoxy Coated Ductile Iron Applications:
ASTM A-536* • N
ickel Aluminum Bronze (NAB)
Inlet: NPT or Flanged
ASTM B148 Alloy C95800
Float:
Outlet: NPT • M
onel - QQ-N-288 Comp B
316 Stainless Steel Standard
ASTM A494 Grade M30H
PRESSURE RATINGS Monel
• C
ast Steel
150 class, 250 psi maximum (Ductile Iron) Super Duplex ASTM A216 Grade WCB
150 class, 285 psi maximum (All other materials)
Rubber Parts: • 3
16 Stainless Steel
300 class, 300 psi maximum (All materials) ASTM A743 Grades CF3M and CFM8
Buna-N® Synthetic Rubber
TEMPERATURE RANGE • S
uper Austenitic Stainless Steel
Water: to 180° F. Max ASTM A351 Grade CK3MCuN (SMO 254)
uper Duplex Stainless Steel ASTM A890
• S
Grade 5A (CE3MN)
Pressure Ratings
Standard Maximum
Valve Size Orifice Diameter
Pressure
1" .076" 300 psi
2" .076” 300 psi
3" & 4" .076” 300 psi
6" .076” 300 psi
Optional upon request
3" & 4" 300 psi
.125"
Model 33ATD
Combination Air and Vacuum Valve with Throttling Air Control Device
Typical Applications
• Vertical Turbine Pumps
• Split Case Pumps
• High Points of Piping Design
Valve Sizing Selection
Air-Vacuum Flow Capacity Air Release Capacity
Determine anticipated water flow and allowable pressure During pressurized pipeline operation, small pockets of
differential for the pipeline application. Select valve from entrapped air will be released through the float actuated
chart to exhaust or admit air at the same rate as water filling 0.076 or .125 inch orifice. Use chart to determine discharge
or draining (in CFS). For larger flows, two or more Model capacity.
33ATD’s may be installed in parallel
Pressure (psi)
Air Flow Rate (scfm)
Model 33ATD
Combination Air and Vacuum Valve with Throttling Air Control Device
Dimensions (In Inches) MODEL 33ATD - 1”, 2”, 3”, 4” and 6” Sizes
33A Pressure Class 300 Lb 33A Pressure Class 150 Lb 33A Pressure Class 300 Lb
Threaded Flanged (INLET) Flanged (INLET)
Valve Size 1"* 2" 3" 4" 1" 2" 3" 4" 6" 1" 2" 3" 4" 6"
A 12.50 16.50 18.50 20.00 13.00 17.75 21.75 23.50 26.75 15.00 18.00 22.00 23.75 27.25
B 6.25 7.50 9.25 9.25 6.25 7.50 9.25 9.25 11.50 6.25 7.50 9.25 9.25 11.50
Inlet (ANSI) 1" NPT 2" NPT 3" NPT 4" NPT 1" 2" 3" 4" 6" 1" 2" 3" 4" 6"
Outlet (NPT) 1" NPT 2" NPT 3" NPT 4" NPT 1" NPT 2" NPT 3" NPT 4" NPT 6" NPT 1" NPT 4" NPT 3" NPT 4" NPT 6" NPT
Number of Holes — — — — 4 4 4 8 8 4 8 8 8 12
Diameter of Bolts — — — — 0.50 0.63 0.63 0.63 0.75 0.63 0.75 0.75 0.75 0.75
Approximate calculated
33 29 38 40 30 39 48 50 126 34 41 55 58 140
shipping weight (lb.)
B B
Throttling
Adjustment
A
A
ØB
Threaded
Flanged
A
(MAX)
A1
WASHER
HEX
SPRING
NUT Throttling Device Dimensions (In Inches)
TD A D
E
D ASSEMBLY A1 ØB C E
SIZE (MAX) (NPT)
1" 4.25 3.00 1.61 3.00 1"-11-1/2 M10X1.00
THROTTLING C 2" 5.50 4.81 2.67 3.82 2"-11 1/2 M12X1.75
DEVICE
ADJUSTING HEX PLUNGER 3" 9.00 6.45 4.06 6.20 3"-8 1/2-13 UNC
SCREW NUT
4" 9.05 7.33 5.20 7.72 4"-8 M12x1.75
THROTTLING 6" 12.75 9.75 7.63 11.38 6"-8 5/8-11 UNC
DEVICE BODY
D
SECTION
Model Number Codes
Size Main Valve Body Float Elastomer Inlet Face
1" 33ATD D Ductile Iron T 316 SS (F) B Buna NPT RF
2" C Cast Steel M Bronze /Monel E EPDM ANSI 150# FF
3" T 316 SS U Super Duplex V Viton ANSI 300# X Other
4" N N.A.B. X Other
6" U Super Duplex
X Other
CLA-VAL ©
1701 Placentia Avenue • Costa Mesa CA 92627 • Phone: 949-722-4800 • E-mail: info@cla-val.com • Website cla-val.com
Copyright Cla-Val Printed in USA Specifications subject to change without notice. 33ATD (R-02/2023`)
