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Air Vent and Air Vent Assembly

UKL Air vents and assemblies are meant to automatically remove air from steam spaces.Air has to be removed because, Air acts as an insulator and severely hampers / restricts heat transfer.Air acts as an oxidizing agent and causes corrosion and weakening leading to damage and leakage in pipes and related equipment. In Boilers it can cause serious accidents.Air gets in the system through Boiler Feed water, at times through process related matters.

Also when steam condenses in long stoppages, in pipelines its volume shrinks tremendously causing a partial vacuum thus drawing in Air in the system from the atmosphere.

Air tends to accumulate towards the top/highest point, around changes in elevation / direction of pipes as also near Dead ends. So it is necessary to have Air vents at these points to vent the accumulated air and prevent any mal-effect on the system.

Removal of Air/O2 is achieved by mounting an Automatic Air vent in the form of a Thermostatic Trap, which in this case traps Steam but relieves Air automatically.

The Air vent assembly provided with Isolation valve, Air collecting Bottle and Temp/Pressure Gauge.

  • Sizes: 15,20mm
  • Ends connection: Socket Weld/Threaded
  • PMO: 32Bar
  • TMO: 240Deg C
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  1. UAV / UAVA

    UKL Air vent / Air vent assembly with Air bottle for Steam line in Forged carbon steel construction as per ASTM A105

    Size  (NB)          Max. Op. Pr / Temp (kg/cm2 / oC) End connections Optional /Additional information
    15, 20 & 2532 / 400Flanged #150/#300

    IBR/Non-IBR

    Screwed/SW connection

During start-up, air is already present within the steam pipes and steam process equipments. Gradually the complete system is steam charged. Later, steam starts condensing at few places and thus cause a vacuum and draw air into the pipes or equipments.

Another source of air is the boiler feedwater and the returning hot condensate. Both types of water can easily absorb various gases, viz Oxygen, Nitrogen and Carbon dioxide. When the water is heated in the boiler, the gases are released with the steam and carried into the distribution system.

During start-up, air is already present within the steam pipes and steam process equipments. Gradually the complete system is steam charged. Later, steam starts condensing at few places and thus cause a vacuum and draw air into the pipes or equipments.

Another source of air is the boiler feedwater and the returning hot condensate. Both types of water can easily absorb various gases, viz Oxygen, Nitrogen and Carbon dioxide. When the water is heated in the boiler, the gases are released with the steam and carried into the distribution system.
Please note that air is the most effective heat insulator and is 1500 times more resistant to heat than steel.

1. Air reduces the heat transfer efficiency
2. Air reduces the temperature of steam
3. Helps to increase the rate of corrosion
4. Can lead to Trap malfunctioning
Air is lighter than steam/air mixture so it will always try to rise to the top of the steam pipe/equipment

Considering this fact, Air vent module is strongly recommended to be installed at below mentioned locations:

1. Topmost(elevated) portion of the saturated steam pipe network
2. Piping dead end parts
3. Top part and opposite side of a jacketed vessel
Yes, air collection bottle is necessary on the upstream of air vent. This air bottle will help to collect the air and retain it inside. This will avoid sudden open and closure of the automatic air vent and thus helps for efficient working and extended service life too
It is explained stepwise as below: - Air accumulates in the Air bottle/pocket - Accumulated air cools down by releasing heat to ambient - At low temperature, trap will be in open condition, thus releasing the air - After releasing the air, steam reaches the trap, the capsule expands & trap closes to trap steam
The most prevalent sizes are 15NB and 20NB. Very seldomly, if the main pipe diameter is more than 350NB, then only does a need of 25NB sized is required.

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