airvents_steam.ppt

Thermostatic air vents

for steam systems up to 45 bar

www.SpiraxSarco.comwww.SpiraxSarco.com

The thermostatic air vent (AVC32 shown)

Patented design of balanced pressure capsule

manufactured using advanced technology to

exacting quality standards

All 316L capsule construction for high corrosion resistance

High integrity trapped graphite gasket

Forged body and cover for robustness and long life (AVC32

and AVS32)

Fully complies with the requirements of the European Pressure Equipment Directive 97/23/ECChoice of brass,

steel or stainless steel construction

Stainless steel strainer screen to protect internals

Two bolt cover design for ease of maintenance (AVC & AVS only)


How it works (AV13, AVC32, AVS32)

Thermostatic air vents contain a liquid filled capsule. The liquid boils at a temperature slightly below that of saturated steam, so when pure steam surrounds the capsule the resultant vapour pressure keeps the valve closed.

When air is present in the steam the temperature at the capsule is lower than that of pure steam, so the valve automatically opens to release the air. It will close again when the surrounding temperature corresponds to the steam pressure saturation temperature.


How it works (AV45)

• The AV45 has a bimetal element

• It operates in a similar way to the balanced pressure thermostatic air vent.

• It is offered for pressures up to 45 bar g

• It is also recommended for all superheated steam applications.


Air – the enemy of good heat transfer

Vacuum breaker

Air vent

Drain to a safe place

Safety valve to vent and drain to a safe place

Condensate

Steam heated jacketed pan

Steam

See next slide


Temperature profile

Su

bs

tanc

e b

eing

he ated

Stag

nan

t film

Metal tan

k wa

ll

Sca

le film

Co

nd

ensate

film

Air film

Air – the enemy of good heat transfer

The diagram shows the three primary barriers to heat transfer – films of water, air and scale. The greatest barrier of all is air. Its presence on the heat transfer surface can cause cold spots and at worst prevent the required heat transfer

taking place at all. At best, the result is erratic and uneven heating. Air is in fact more than 1500 times more resistant to heat transfer than iron and steel, and

13000 times more resistant than copper!


Terminal end of distribution main


Condensate

Steam

AV13 air vent


Autoclave

AV13 air ventAV13 air vent



Steam

Condensate


Typical inverted bucket trapping arrangement with air vent

AVC32 air vent

Condensate

Steam


Steam moisture separator


AVC32 air vent

Condensate

Steam


AV13

• The AV13 is a brass bodied air vent with balanced pressure thermostatic element

• It is available in the following sizes: 3/8”, ½” and ¾”

• Connections: Screwed BSP or NPT

• Suitable for pressures up to 13 bar


AVC32

• The AVC32 is a carbon steel bodied air vent with balanced pressure thermostatic element

• It is available in the following sizes: ½”, ¾” and 1”

• Screwed, flanged, socket weld or butt weld connections

• Two bolt design for ease of maintenance

• Suitable for pressures up to 32 bar g


AVS32

• The AVS32 is a stainless steel bodied air vent with balanced pressure thermostatic element

• It is available in the following sizes: ½”, ¾” and 1”

• Screwed, flanged, socket weld, or butt weld connections




AV45

• The AV45 is an alloy steel-bodied air vent with bimetallic thermostatic element

• It is available in the following sizes: ½”, ¾”, 1” and 1 ½”

• Screwed, socket weld or butt weld connections




Features and benefits

• Improves heat transfer whilst saving energy and productivity

• Maintains process performance where temperature is critical

• Reduces corrosion and maintenance costs

• Promotes even heating and improves product quality

• Ease of maintenance with two bolt cover design (AVC32, AVS32)

• Fully complies with the requirements of the European Pressure Equipment Directive 97/23/EC


Installation

• Air vents should be located at a point furthest away from the steam inlet because this is where air tends to collect

• They should be fitted where possible at all high points in the system and to all ‘critical’ plant

airvents_steam.ppt

Documents

carbon steel bodied

alloy steelbodied air

avs32 thermostatic air

installation air vents

pure steam

safe place condensate

safe place steam condensate

saturated steam