Thermostatic steam traps are valves used in steam piping and equipment to automatically discharge condensate, air, and non-condensable gases and prevent steam leakage. They feature automatic discharge temperature adjustment, with a subcooling range of 15°C to 40°C. They can be installed horizontally or vertically and are commonly used in steam mains and jacketed vessels in the chemical, food, and pharmaceutical industries.
Before understanding the working principle of a thermostatic steam trap, we must first understand its components.
Thermostatic steam traps primarily consist of the following components:
Valve body: This is like the trap’s “housing,” serving as the basic framework of the entire valve.
Thermostatic element: This is the “brain” of the thermostatic steam trap and can be of various types, including bimetallic, bellows, and metal diaphragm.
Disc and seat: The disc acts as the “opening and closing actuator,” while the seat forms the sealing surface. The filter acts as a “guard,” installed before the valve to prevent impurities in the piping from entering the valve cavity and affecting the normal movement of the valve disc, ensuring stable operation of the trap.
The drain pipe serves as the condensate outlet, directing condensate discharged from the trap to a designated location to ensure the normal operation of the steam system.
Operating Principle
Thermostatic steam traps operate by utilizing the temperature difference between steam and condensate to actuate the valve opening and closing via the thermal expansion and contraction of a temperature-sensing element, thereby preventing steam from leaking out. Common temperature-sensing elements include bellows, diaphragms, or bimetallic strips. These elements are filled with a low-boiling-point, volatile liquid or utilize the thermal expansion and contraction properties of metals.
When the equipment is started up or the condensate temperature is low, the temperature-sensing element contracts or deforms, causing the valve disc to open and discharge condensate and air. As steam enters, its temperature rises, causing the liquid in the temperature-sensing element to vaporize and expand, or the metal strip to deform due to heat, pushing the valve disc closed and preventing steam from leaking out. When the condensate accumulates again and cools down, the temperature-sensing element returns to its original position, reopening the valve, and the cycle continues for automatic drainage.
Thermostatic Steam Trap Function
Energy Efficiency: The valve opens only when the condensate cools to a certain temperature below the saturation temperature. As a result, the discharged water temperature is lower (typically 10-30°C below the saturation temperature), minimizing “steam carryover losses” and significantly saving energy.
Resistant to Water Hammer and Frost Cracking: The valve components are typically all-metal, providing a robust structure that withstands water hammer. In cold environments, a valve designed to vent can prevent frost cracking due to ice formation.
Strong Air Discharge Capacity: The valve opens fully during startup, quickly purging air from the system and ensuring rapid and even heating of the equipment.
Small Size and Low Noise: The valve is compact and relatively quiet during operation.
Of course, not all valves are perfect, and thermostatic steam traps have their limitations. For example, the drain response is relatively slow because it waits for the condensate to cool to a certain temperature before opening. This makes it unsuitable for applications with drastic load fluctuations or where rapid draining is required, such as heat exchangers and tumble dryers. It can also cause water accumulation in equipment, as it discharges supercooled condensate, which can lead to water accumulation within the heating equipment, affecting heat transfer efficiency. Its backpressure resistance is relatively poor. In actual use, it’s important to choose the right one based on the specific situation.
Newton‘s thermostatic steam traps are made of A105 material and are designed with full consideration of corrosion tolerance, minimum shell wall thickness, and pressure and temperature ratings. They effectively prevent pipe impurities from entering the valve, ensuring proper function and preventing water hammer damage to internal components. Imported bimetallic strips guarantee a specific bending value. The temperature structure is adjustable for precise temperature control. The unique linear sealing system and micron-level precision valve seat and valve core ensure reliable closure and no steam leakage.
If you’re interested in purchasing a thermostatic steam trap but aren’t sure which one to choose, take a look at Newton’s products and we guarantee you’ll find the perfect solution.
