Spirax Sarco TD Series Thermodynamic Steam Traps: Comprehensive Technical Guide ​

Introduced in 1950, the Spirax Sarco TD series thermodynamic steam traps represent over 70 years of engineering refinement. Designed to handle severe steam system conditions, these traps feature a robust construction capable of managing operating pressures up to 250 bar. With over 6,000,000 units supplied worldwide, the TD series is one of the most widely used thermodynamic steam trap families in the industry.

For model-specific product data and selection information, browse the Spirax Sarco thermodynamic steam trap catalog.

Core Features and Advantages ​

The continuous improvement of the TD series has resulted in an extremely durable trap suitable for virtually any demanding steam application. Key advantages include:

• Compact & Lightweight: Reduces installation costs and space requirements.
• Unique 3-Hole Outlet: Ensures perfect disk operation and even flow characteristics, extending product life and avoiding seat replacement hassles.
• Knife-Edge Seating: Requires no gaskets and effectively prevents leaks.
• Single Moving Part: An internal stainless steel disk ensures reliable operation with minimal maintenance.
• Resilience: Highly resistant to superheat, water hammer, freezing, and vibration. The distinct "click" sound during closure makes it easy to verify normal operation.

Optional Accessories ​

• Insulation Cover: Protects against excessive heat loss and rapid cycling caused by low temperatures, wind, or rain (especially in outdoor installations).
• Blowdown Valve: Allows for inline cleaning of the built-in strainer.
• Anti-Air Binding Disk: Prevents air binding during startup when large volumes of air are present.

Working Principle ​

1. Startup: Inlet pressure lifts the disk, immediately discharging cool condensate and air.
2. Flashing: Hot condensate flowing through the trap flashes into secondary steam. The high-velocity steam creates a low-pressure zone under the disk, drawing it toward the seat.
3. Closure: Secondary steam accumulates in the chamber above the disk, forcing the disk down against the inner ring (closing the inlet) and the outer ring (sealing the chamber pressure).
4. Recycle: As the secondary steam above the disk condenses, pressure drops. The disk lifts again, discharging condensate and repeating the cycle.

Model Overview and Specifications ​

TD16 ​

• Connection: Screwed (BSP/NPT) 1/2", 3/4", 1" or Flanged (DN15, 20, 25).
• Design: Built-in strainer, Stainless Steel ASTM A743 Gr. CA 40F body.
• Limits: PN25 design; Max Working Pressure (PMO) 16 bar g; Max Working Temp (TMO) 300°C.

TD25 ​

• Connection: Screwed (1/2", 3/4", 1") or Flanged (EN1092/ISO7005 PN25).
• Design: Built-in strainer, Stainless Steel body.
• Limits: PN40 design; Max Working Pressure (PMO) 25 bar g; Max Working Temp (TMO) 400°C.

TD42 Series (TD42L, TD42LA, TD42H, TD42HA, TD42S2) ​

• Connection: Screwed or Socket Weld (BS 3799 Class 3000).
• Design: Built-in strainer. Features electroless nickel plating (ENP) on specific models. "A" suffix models indicate an anti-air binding disk.
• Limits: PN63 / ANSI 300 design; Max Working Pressure (PMO) 42 bar g; Max Working Temp up to 400°C.

TDC46M & TDS46M ​

• Connection: Screwed, Socket Weld, or Integral Flange (EN1092 PN40/PN100, ASME Class 150/300/600).
• Design: Available with optional BDV1 integral blowdown valve. TDC46M features a carbon steel body; TDS46M utilizes a stainless steel body.

TD62M & TD62LM ​

• Connection: Screwed (NPT) or Socket Weld (ANSI B 16.11 Class 3000).
• Design: Alloy steel body (ASTM A217 Gr. WC 6) with 100-mesh stainless steel strainer.
• Limits: ANSI 600 design; Max Working Pressure (PMO) 62 bar g @ 482°C.

TD120M ​

• Connection: Socket Weld, Butt Weld (Schedule 160), or Flanged (up to PN250/ANSI 1500).
• Design: Extreme high-pressure capability with Alloy Steel ASTM A182 F22 body and sintered stainless steel strainer.
• Limits: PN250 design; Max Working Pressure (PMO) 250 bar g @ 300°C; Max Working Temp (TMO) 550°C @ 80 bar g.

Typical Applications ​

TD series steam traps are versatile and highly reliable across multiple applications:

Steam Mains Drainage: Effectively discharging condensate from steam distribution mains prevents water hammer and improves overall steam quality.

Pressing Machines & Process Equipment: Rapid and effective condensate removal ensures the required process temperatures are maintained continuously, reducing product waste and maintaining optimal heat transfer.

(Note: For atmospheric discharges, a DFI type diffuser can be installed at the outlet to reduce noise and discharge velocity.)

Downloads ​

• Spirax Sarco TD Series Thermodynamic Steam Traps.pdf