In industrial steam systems, efficiently discharging condensate without allowing live steam loss is essential for maintaining heat transfer efficiency and ensuring safe system operation. The TLV Balanced Pressure Thermostatic Steam Trap, models L21S and L32S, is designed with a precise temperature-controlled operating mechanism utilizing the proprietary X-element together with a Fail-Open safety design. This enables optimum condensate removal, minimizes water hammer, and protects system equipment under high-pressure and high-temperature operating conditions.

As a leading Japanese manufacturer specializing in steam engineering and energy-saving solutions, TLV developed the L21S and L32S series to satisfy the demanding requirements of modern steam systems. Featuring a durable forged steel construction, outstanding air venting capability, and high operational reliability, these steam traps are widely used in steam mains, steam tracing systems, heating equipment, and numerous industrial process applications.

1. Overview of the Balanced Pressure Thermostatic Steam Trap

The TLV Balanced Pressure Thermostatic Steam Trap is an automatic condensate drainage device designed to discharge condensate from steam systems while preventing the loss of live steam.

The TLV L21S and TLV L32S models are designed for a wide range of industrial steam applications, including:

• Steam mains.
• Steam tracing systems.
• Industrial dryers.
• Heating equipment.

Featuring a high-strength forged steel body, the steam trap operates reliably under high-pressure and high-temperature conditions while maintaining optimum condensate drainage performance throughout system operation.

2. Operating Principle of the Balanced Pressure Thermostatic Steam Trap

The TLV L21S/L32S operates based on the temperature difference between saturated steam and condensate.

Inside the steam trap is a C6 X-element filled with a specially formulated expansion fluid.

Its operating principle is as follows:

• When relatively cool condensate enters the steam trap, the X-element contracts, causing the valve to open and discharge the condensate.
• As hot steam approaches saturation temperature, the X-element expands, forcing the valve to close tightly and preventing live steam from escaping.

This temperature-responsive opening and closing mechanism allows the TLV Balanced Pressure Thermostatic Steam Trap to maintain a consistent sub-cooling level of up to 6°C below saturated steam temperature, ensuring efficient condensate discharge while maximizing steam utilization.

3. What Is the “Fail-Open” Design? Benefits in Practical Operation

One of the distinguishing features of the TLV L21S/L32S is its Fail-Open design.

This means that if the X-element becomes damaged or fails, the valve automatically remains in the open position rather than closing.

This design offers several important advantages:

• Prevents condensate from being retained in the steam piping.
• Prevents water hammer.
• Minimizes corrosion and damage to heat exchange equipment.
• Improves overall system safety.

This is a significant advantage of the TLV Balanced Pressure Thermostatic Steam Trap compared with steam traps featuring a Fail-Close design, which may allow dangerous condensate accumulation within the steam system.

4. Key Features of the L21S / L32S Models

The TLV L21S and TLV L32S are engineered to satisfy demanding industrial steam applications with numerous outstanding features, including:

• High-strength forged steel body.
• Stable operation throughout the entire operating pressure range.
• No condensate retention within the steam space.
• Excellent automatic air venting capability during system start-up.
• Resistant to superheated steam and water hammer.
• Compact construction with high condensate discharge capacity.
• Hardened stainless steel valve seat for extended service life.
• Built-in large-area strainer to minimize clogging.
• Easy inspection, cleaning, and maintenance.
• Optional integrated check valve.

5. Detailed Technical Specifications

Specification	TLV L21S	TLV L32S
Size	15, 20, 25 mm	15, 20, 25 mm
Connection	Threaded, Socket Weld, Flanged	Threaded, Socket Weld, Flanged
Maximum Operating Pressure (PMO)	2.1 MPaG	3.2 MPaG
Minimum Operating Pressure	0.01 MPaG	0.01 MPaG
Maximum Back Pressure	90% of inlet pressure	90% of inlet pressure
Sub-cooling	Up to 6°C	Up to 6°C
Thermostatic Element	C6 X-element	C6 X-element

These specifications enable the TLV L21S/L32S to perform efficiently under a wide variety of medium- and high-pressure steam system operating conditions.

6. Operating Conditions and Pressure–Temperature Limits

The TLV Balanced Pressure Thermostatic Steam Trap is designed for demanding industrial applications with the following operating limits:

• Maximum Allowable Pressure: 3.2 MPaG
• Maximum Allowable Temperature: 300°C
• Operating temperature curve corresponding to saturated steam pressure.

Its ability to withstand high pressure and elevated temperature ensures reliable operation in medium- and high-pressure industrial steam systems.

7. Construction Materials and Equipment Durability

The primary components of the TLV L21S/L32S are manufactured from high-quality materials to ensure long-term reliability under severe steam service conditions.

Body and Cover

• Forged Carbon Steel A105

Valve Seat

• SUS420F Stainless Steel

X-element

• SUS304 Stainless Steel

Gasket

• Graphite / SUS316L

Strainer Screen

• SUS304 / SUS430

The use of these premium materials provides numerous benefits:

• Extended service life.
• Excellent corrosion resistance.
• High pressure and temperature resistance.
• Reduced maintenance costs throughout the product life cycle.

8. Applications in Industrial Steam Systems

The TLV L21S/L32S is widely used in numerous industrial steam applications, including:

• Steam mains.
• Steam tracing systems for freeze protection.
• Heat exchangers.
• Industrial dryers.
• Tank heating systems.

Its excellent automatic air venting capability during start-up makes it particularly suitable for applications requiring rapid and stable heat transfer.

9. Comparison with Other Types of Steam Traps

Criteria	TLV Balanced Pressure Thermostatic Steam Trap L21S/L32S	Mechanical Steam Trap	Thermodynamic Steam Trap
Start-up Air Venting	Excellent	Moderate	Poor
Temperature Sensitivity	High	Low	Low
Resistance to Superheated Steam	Good	Moderate	Good
Safety During Failure	Fail-Open	Depends on Design	Not Guaranteed
Suitability for Steam Tracing	Excellent	Not Optimal	Not Optimal

With its temperature-responsive operating mechanism and Fail-Open safety design, the TLV L21S/L32S provides superior performance and operational safety for a wide variety of industrial steam applications.

10. Benefits of Using the L21S / L32S in Your Steam System

Installing the TLV Balanced Pressure Thermostatic Steam Trap L21S/L32S provides numerous operational benefits, including:

• Improved heat transfer efficiency.
• Reduced risk of water hammer.
• Minimized live steam loss.
• Enhanced system safety.
• Extended equipment service life.
• Reduced long-term maintenance and operating costs.

Its precise temperature-controlled operation optimizes steam utilization while improving the reliability and efficiency of the entire steam system.

11. Conclusion & Selection Recommendation

The TLV Balanced Pressure Thermostatic Steam Trap, models L21S and L32S, is a highly reliable condensate drainage solution for industrial steam systems requiring:

• Precise temperature-controlled condensate discharge.
• Excellent automatic air venting capability.
• A safe Fail-Open design.
• Outstanding durability under high-pressure and high-temperature operating conditions.

Featuring TLV’s proprietary X-element technology, robust forged steel construction, and dependable performance under demanding service conditions, the TLV L21S/L32S is an ideal choice for food processing plants, textile mills, chemical plants, power generation facilities, and numerous medium- and high-pressure steam systems. The steam trap helps improve heat transfer efficiency, reduce energy consumption, and ensure long-term safe and reliable system operation.