Are you looking for an automatic air vent for steam systems capable of efficiently removing non-condensable gases, operating reliably under high pressure, and providing long service life in industrial environments?

The TLV LA21 Thermostatic Air Vent is a solution trusted by many factories worldwide thanks to TLV’s proprietary X-element thermostatic technology from Japan, which automatically discharges cold air and non-condensable gases during system startup while tightly closing when saturated steam reaches the valve.

With an all-stainless-steel construction, compact size, operating pressure capability up to 2.1 MPaG, and high air venting capacity, the TLV LA21 is particularly suitable for boilers, steam headers, heat exchangers, heating coils, autoclaves, food processing, pharmaceutical facilities, and many other industrial steam applications.

1. What is the TLV LA21?

The TLV LA21 is a Thermostatic Air Vent specifically designed for steam systems.

The primary functions of the device are:

• Automatically venting non-condensable gases.
• Removing cold air during startup.
• Preventing saturated steam from escaping.
• Improving the heat transfer efficiency of the entire system.

The LA21 uses the C22 X-element, which senses the temperature differential between steam and the environment inside the valve, allowing it to open and close fully automatically without any external power supply or control signal.

2. Why is an air vent necessary in a steam system?

In steam systems, air and non-condensable gases are commonly present in:

• Steam piping
• Steam headers
• Heat exchangers
• Heating coils
• Sterilization equipment
• Autoclaves

If these gases are not removed, they can cause:

Reduced heat transfer efficiency

Non-condensable gases form an insulating layer on heat transfer surfaces, reducing the steam heat transfer rate.

Increased heating time

Equipment requires more time to reach the target temperature.

Uneven temperature distribution

Hot and cold zones may occur within the same equipment.

Increased energy consumption

The boiler must operate longer to compensate for the lost heat transfer efficiency.

Corrosion

Oxygen contained in air can cause corrosion of steam piping and equipment.

The TLV LA21 is specifically designed to solve these problems.

3. Operating principle of the LA21 Thermostatic Air Vent

Startup phase

When the system is cold:

• Air and non-condensable gases accumulate in the piping.
• The temperature at the valve is low.
• The X-element contracts.
• The valve remains open.
• Air is discharged at a high venting rate.

When steam reaches the valve

When saturated steam contacts the thermostatic element:

• The temperature rises rapidly.
• The X-element expands.
• The valve disc is forced closed.

The valve prevents steam from escaping, thereby reducing energy loss.

When non-condensable gases reappear

If cold air or non-condensable gases accumulate again:

• The temperature at the valve decreases.
• The X-element contracts.
• The valve automatically opens to vent the gases.

This process is continuous and fully automatic.

4. Construction of the TLV LA21 Air Vent

Stainless steel valve body

The valve body is manufactured from high-strength cast stainless steel, providing excellent corrosion resistance and suitability for industrial steam environments.

Its compact design allows installation in locations with limited space.

C22 X-element

This is the most critical component of the LA21.

Key characteristics:

• High thermal sensitivity
• Fast response
• Accurate shut-off when exposed to saturated steam
• Long service life

The X-element technology is one of the key advantages of the TLV brand from Japan.

SUS630 valve seat

The sealing surface is made of SUS630 stainless steel with high hardness, providing:

• Reduced wear
• Long-term sealing performance
• Resistance to erosion caused by high-velocity steam flow

Stainless steel spring and internal components

The internal components are manufactured from stainless steel to ensure:

• High temperature resistance
• Corrosion resistance
• Stable long-term operation

5. Outstanding features of the TLV LA21

The TLV LA21 offers numerous advantages for steam systems:

• Automatic venting of non-condensable gases
• No external power supply required
• All-stainless-steel construction
• Compact dimensions
• High air venting capacity
• Tight shut-off when steam reaches the valve
• Reduced steam loss
• Improved heat transfer efficiency
• Shorter system startup time
• Long service life with minimal maintenance

6. TLV LA21 Technical Specifications

Based on the manufacturer’s datasheet:

Parameter	Value
Model	LA21
Type	Thermostatic Air Vent
Brand	TLV – Japan
Connection	Screwed
Size	10A, 15A
Maximum operating pressure	2.1 MPaG
Maximum operating temperature	220°C
Thermostatic element	X-element C22
Body material	Stainless Steel
Manufacturing standard	ISO 9001 / ISO 14001

7. Air venting capacity and operating performance

According to the TLV Air Venting Capacity graph:

• The higher the differential pressure, the greater the air venting capacity.
• At a differential pressure of approximately 2.0 MPa, the venting capacity can reach approximately 2000 L/min (equivalent capacity at 20°C and atmospheric pressure).

This demonstrates that the LA21 can:

• Vent air extremely quickly during startup.
• Reduce the time required to bring the system into operation.
• Perform particularly effectively in large-volume steam systems.

8. Dimensions and connection type

Overall dimensions

According to the dimensional drawing:

• Size: 10A / 15A
• L: 55 mm
• ØW: 47 mm
• Weight: 0.4 kg

Thread type

• Standard Rc (PT) thread.
• Other thread standards are available upon request.

The compact design allows easy installation at:

• High points of steam piping
• Heating coil inlets
• Tops of heat exchangers
• Steam headers

9. Practical applications in steam systems

Boilers and steam headers

The LA21 is installed at air accumulation points to:

• Vent air during startup
• Reduce air binding
• Accelerate pipeline heating

Heat exchangers

It helps:

• Remove non-condensable gases
• Increase the heat transfer coefficient
• Maintain stable operating temperatures

HVAC heating coils

Applications include:

• AHUs
• FCUs
• Drying coils
• Air heating systems

Food and beverage industry

Used for:

• Cooking vessels
• Pasteurization equipment
• CIP/SIP systems
• Food processing lines

Pharmaceutical industry

Suitable for:

• Autoclaves
• Sterilization equipment
• Clean steam systems

10. Selection and installation guidelines

Selection criteria

The following factors should be considered:

• Pipe size
• Operating pressure
• Steam temperature
• Air accumulation location
• Required venting capacity

Installation orientation

Recommended:

• Vertical installation
• Flow direction matching the arrow on the valve body
• Installation at high points where air tends to accumulate

Operating precautions

• Do not install in locations continuously flooded with condensate.
• Periodically inspect venting performance.
• Clean the valve if the system contains debris or scale.

11. Advantages of the TLV Japanese brand

TLV Co., Ltd. is one of the world’s leading manufacturers specializing in steam and condensate equipment.

Advantages of TLV include:

• Japanese technology
• Deep expertise in steam systems
• Products used in thousands of factories worldwide
• Strict quality standards
• Professional technical support

Selecting the TLV LA21 helps companies:

• Improve steam system efficiency
• Reduce energy consumption
• Increase operational reliability
• Lower long-term maintenance costs

12. Quotation and technical consultation

The price of the TLV LA21 Thermostatic Air Vent depends on:

• Size (10A or 15A)
• Thread standard
• Order quantity
• Project requirements
• Delivery schedule

For an accurate quotation and assistance in selecting the appropriate model, please contact our technical team. We supply genuine TLV LA21 products from Japan, complete with documentation and technical support for boilers, steam lines, heat exchangers, HVAC systems, food processing, pharmaceutical applications, and many other industrial steam systems, helping your system operate safely, efficiently, energy-saving, and reliably over the long term.