The Steam Liquid Two Phase Flow Trap is an energy-saving and environmentally friendly device based on two-phase flow theory, widely used in steam systems and heat exchange equipment. It removes condensate and air from steam, maintaining the efficiency and safety of the steam system and improving steam quality. This valve has no moving mechanical parts, a fully enclosed stainless steel structure, is maintenance-free, has a long service life, can withstand high temperatures and pressures, and can also reduce cavitation vibration, reduce steam consumption during regulation, and improve the thermal efficiency of the steam system.
Working Principle of Steam Liquid Two Phase Flow Trap
The core idea of the Steam Liquid Two Phase Flow Trap is to “directly control the condensate flow rate using the liquid level signal.” The entire process is completely self-powered and requires no external energy or moving parts. Its workflow can be broken down into three steps:
Step 1: Signal Acquisition
A “phase change tube” (signal tube) is led out from the side wall of the controlled container, with the horizontal section located in the vapor space and the downward-bending section extending into the liquid space. When the liquid level in the container rises to the set height, the inlet of the phase change tube changes from “pure vapor phase” to “vapor-liquid two phases.” This phase change becomes the signal that the liquid level has reached the target.
Step 2: Mixing and Throttling
Drainage enters the valve chamber from the bottom of the container, mixes with the two-phase flow from the phase change tube, and flows together through a “throat”—a gradually expanding channel formed by a segmented valve core. The throat area is fixed, but the effective flow area automatically changes with the vapor-liquid ratio:
• High liquid level → reduced vapor flow → larger effective flow area → larger drain flow;
• Low liquid level → increased vapor flow → smaller effective flow area → smaller drain flow.
Step 3: Self-Balancing Regulation
Since there are no moving parts, the entire regulation process is completed by the redistribution of the fluid’s dynamic and static pressures. Liquid level fluctuations can be controlled within ±50 mm, the load adaptability range is 30%–100%, and there is no mechanical wear, no cavitation jamming, and a service life of up to 10 years.
Differences between Steam Liquid Two Phase Flow Trap and Thermodynamic Steam Traps
| Comparison Projects | Steam Liquid Two Phase Flow Trap | Thermodynamic Steam Trap |
| Driving Method | The fully self-regulating type directly adjusts the throat opening by utilizing the pressure difference generated by the vapor-liquid two-phase flow, with no moving parts. | The valve plate is driven to open and close by relying on the density difference between steam and condensate and the pressure difference across the valve plate. |
| Moving parts | No moving parts | It has a movable valve plate that operates frequently. |
| Back pressure limitation | Up to 50% | No more than 80% of import pressure. |
| Steam leakage | There is virtually no continuous steam leakage. | Periodic steam leakage is approximately 3%. |
| Subcooling | Near-saturation temperature drainage | 8℃–15℃ subcooling |
| Maintenance Requirements | Maintenance-free, 10-year lifespan | Valve plates wear quickly and require regular replacement |
| Applicable Operating Conditions | Suitable for high and low pressure heaters and boiler continuous blowers with large load fluctuations and high flow rates | Medium and low pressure steam transmission pipes, heat tracing pipelines, etc. |
| Installation Requirements | No electrical or pneumatic control system required, simplified structure | Minimum inlet pressure of 0.25 bar g must be maintained. |
In simple terms, the Steam Liquid Two-Phase Flow Trap replaces the moving valve plate of a thermodynamic valve with a self-adjusting throat without moving parts, thus achieving comprehensive superiority in maintenance-free operation, low steam leakage, and high back pressure adaptability.
Steam Liquid Two-Phase Flow Trap Applications
The scenarios where the Steam Liquid Two-Phase Flow Trap excels can be summarized into four types of operating conditions:
1. High-parameter heaters
Low-pressure heaters, high-pressure heaters, shaft seal heaters—large load changes (100%→60%), water level fluctuations are suppressed to 50–100 mm, ensuring stable operation.
2. Key equipment on the boiler side
Boiler drums, continuous blowdown expansion tanks—high steam and water loads, frequent start-ups and shutdowns, the absence of moving parts avoids jamming.
3. Heat Network and Waste Heat Recovery
Heat network heaters, flash tanks, evaporators—direct recovery of condensate via vapor-liquid two-phase flow, maintaining a constant water level, increasing feedwater temperature by approximately 5°C, and saving nearly a thousand tons of coal annually.
4. Applications with Low Flow Rates, Low Pressure, or Drastic Operating Conditions
Continuous blowdown expansion tanks, shaft seal heaters, heat exchangers in the petrochemical and metallurgical industries—maintaining precise water levels even under low loads, avoiding the risks of flooding or dry burning associated with traditional float valves.
If you are looking for a high-quality Steam Liquid Two-Phase Flow Trap, consider Newton‘s QYL Automatic Level Control Device for Vapor-Liquid Two-Phase Flow Trap; it will surely impress you.
