Variant Anti theft Air Valves

Variant Anti-theft valve

General

Variant combination air release and vacuum break valves protect pipelines from damaging vacuum conditions while ensuring that the system maintains design efficiency. The integral anti-shock feature provides protection against the damaging effects of uncontrolled filling and pump stoppages.

Functions

  • High capacity air discharge
  • High capacity air intake
  • Pressurized air release
  • Surge alleviation

Features

  • Optimum flow characteristics
  • Low pressure sealing
  • Compact design
  • No dissimilar metal corrosion

Operation of Variant Air Valves

Large orifice air discharge

During initial filling the pipeline is filled with air. As water is introduced into the pipeline, the air flows naturally towards the highest points along the pipeline. Air valves, positioned at these high points, allow air to pass freely through the large orifice to atmosphere.

Vacuum break

During scouring or when a pipeline ruptures, it is imperative that the pipeline is protected from damaging negative pressures. Variant air valves provide a full bore, unimpeded flow path that maximises the valve’s air intake capacity. The rapid inflow of air effectively prevents damaging vacuum conditions.

Pressurized air release

During normal operating conditions, air accumulates in the air valves, located at the high points along the pipeline. Once sufficient air has collected in the valve, the automatic float drops, opening the automatic orifice and allowing the air to escape to atmosphere.

Surge protection

Should pump stoppages cause water column separation within the pipeline, air is admitted rapidly through the air valve’s large orifice to protect the pipeline. As the water column returns, this air is then gradually discharged through the air valve’s anti-shock orifice. By restricting the discharge through the anti-shock orifice, sufficient air is retained in the pipeline to create a temporary surge accumulator. In instances where pipelines are filled too quickly, the anti-shock mechanism is blown shut by the excessive air flow. Air is now only released through the anti-shock orifice in a controlled manner, creating an air cushion in the pipeline. This air cushion slows down the approaching water column and absorbs any potential surges.

Anti-theft

Air valve theft adversely affects the reliability and efficiency of pipelines. This problem is compounded when multiple air valves are stolen from the same pipeline. The Variant models LN and LT were developed to prevent the theft of air valves thereby ensuring that the pipeline maintains it’s design and structural integrity.

Air Valve Selection

Sizing

The overriding criteria for air valve sizing is the intake requirement under vacuum conditions. To protect the pipeline and joints, it is necessary to limit the system negative pressure to 3.5m by admitting sufficient air into the pipeline as it empties. One needs to consider the pipeline diameter and gradient when calculating the required flow rate. Scour valve sizes and the rupture percentage of the pipeline are additional factors which need to be taken into account. Once the required intake flow rates have been calculated, the appropriate air valve can be selected from the following table.

 

Intake flow rates at 3.5 meters vacuum VALVE

VALVE SIZE MODEL LN MODEL LT
 25mm 58 L/S
 32mm  215 L/S
 50mm 573 L/S
 80mm 792 L/S 540 L/S
 100mm 735 L/S
 150mm 1865 L/S
 200mm 3135 L/S

Although the air valve size is determined by the air flow required under the vacuum conditions, the flow rate (switching rate) at which the anti-shock mechanism is activated, needs to be considered to ensure that your pipeline will be adequately protected.

Orifice sizes and switching rates

SIZE MM 25mm LN 50mm LN 80mm LN 100mm LN 80mm LT 100mm LT 150mm LT 200mm LT
Anti-shock orifice 4 9 14 17 14 17 25 34
Inlet 25 50 80 100 80 100 150 200
Outlet 25 50 80 100 80 95 150 200
Switching Flow L/S 12 30 119 161 48 130 350 500

The LT can be supplied with a range of switching rates for each size.

Model LN Specifications

NOMINAL SIZE MODEL NO PRESSURE RATING HEIGHT DIAMETER
25mm Flanged * 025LN16 1600KPA 280mm 165mm
25mm Flanged * 025LN25 2500KPA 280mm 165mm
25mm Flanged * 025LN40 4000KPA 340mm 165mm
50mm Flanged 050LN16 1600KPA 275mm 165mm
50mm Flanged 050LN25 2500KPA 275mm 165mm
50mm Flanged 050LN40 4000KPA 316mm 165mm
80mm Flanged 080LN16 1600KPA 345mm 200mm
80mm Flanged 080LN25 2500KPA 345mm 200mm
100mm Flanged 100LN16 1600KPA 345mm 240mm
100mm Flanged 100LN25 2500KPA 345mm 240mm

*The 25mm valve has a 50mm mounting flange and should be installed above a 50mm isolating butterfly valve.

Working temperatures

  • 4 – 75 Degrees Celsius.

Standard factory tests:

  • Automatic orifice operation.
  • Hydrostatic – 1.5 times working pressure.
  • Low pressure sealing – 20kpa.

End connections:

  • Flanged Valves:  SANS 1123 studded

Type

Triple acting three stage

Material specification

BODY : Molybdenum Reinforced Nylon 11
AUTOMATIC FLOAT : High Density polyethylene
KINETIC FLOAT : High Density polyethylene
ANTI SHOCK FLOAT : High Density polyethylene
AUTOMATIC SEAL : EPDM
KINETIC SEAL AND O RINGS : Nitrile
SPACERS, STUDS, NUTS AND BOLTS : 304/316 Stainless steel

Model LT Specifications

NOMINAL SIZE MODEL NO PRESSURE RATING HEIGHT DIAMETER
80mm Flanged 080LT16 1600KPA 360mm 235mm
80mm Flanged 080LT25 2500KPA 360mm 235mm
80mm Flanged 080LT40 4000KPA 450mm 235mm
100mm Flanged 100 LT16 1600KPA 360mm 235mm
100mm Flanged 100LT25 2500KPA 360mm 235mm
100mm Flanged 100LT40 4000KPA 450mm 235mm
150mm Flanged 150LN16 1600KPA 510mm 370mm
150mm Flanged 150LN25 2500KPA 510mm 370mm
150mm Flanged 150LN40 4000KPA 575mm 370mm
200mm Flanged 200LT16 1600KPA 590mm 410mm
200mm Flanged 200LT25 2500KPA 590mm 410mm
200mm Flanged 200LT40 4000KPA 650mm 410mm

*The 25mm valve has a 50mm mounting flange and should be installed above a 50mm isolating butterfly valve.

Working temperatures

  • 4 – 75 Degrees Celcius.s.

Standard factory tests:

  • Automatic orifice operation.
  • Hydrostatic – 1.5 times working pressure.
  • Low pressure sealing – 20kpa.

End connections:

  • Flanged Valves:  SANS 1123 studded

Type

Triple acting three stage

Material specification

BODY : 304/316 Stainless steel
AUTOMATIC FLOAT : High Density polyethylene
KINETIC FLOAT : High Density polyethylene
ANTI SHOCK FLOAT : High Density polyethylene
AUTOMATIC SEAL : EPDM
KINETIC SEAL AND O RINGS : Nitrile
SPACERS, STUDS, NUTS AND BOLTS : 304/316 Stainless steel

Installations

Exploded view of
optional installation

Variant LTI Series

 

The LT series has been expanded to include an integral isolation valve. Closing the isolation valve
allows maintenance staff to service the air valve in situ.

Any attempt to remove the air valve completely will result in a discouraging leak rendering the valve difficult, if not impossible to steal.

Assembly drawing
for the LTI Series

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