1. Steam Piping (HTG Inlet)

This represents the most critical application location for check valves.

Function: Prevents backflow of steam and condensate.

During sudden unit shutdowns (especially emergency shutdowns) or abrupt interruptions in external steam supply, steam line pressure drops instantaneously. Meanwhile, the HTG maintains elevated pressure (potentially exceeding steam line pressure) due to high-temperature boiling of the solution. Without a check valve, high-temperature solution, uncondensed steam, and generated water vapor from the generator would backflow into the steam line. Lithium bromide solution is highly corrosive; such backflow would severely corrode and contaminate the steam piping and boiler system.

2. On Solution Piping

Check valves are sometimes installed at points where high-temperature solution flows from the HTG to the LTG, or at the outlet of solution pumps.

Function: Prevent solution siphoning and maintain the pump's starting head pressure.

When the unit shuts down, the concentrated solution in the HTG, located at a higher elevation, will attempt to flow back to the absorber or solution pump inlet, which are at a lower elevation, due to gravity. Installing a check valve blocks this backflow, maintains proper liquid levels in vessels, and prepares for the next startup.

3. Refrigerant Water Piping

Check valves may also be installed at the outlet of the evaporator refrigerant water pump or at the inlet of the throttling device between the condenser and evaporator.

Function: Prevents refrigerant water backflow and maintains pump outlet pressure.

Its principle is similar to that of solution pumps, primarily ensuring stable operation and rapid startup of the refrigerant water pump. It prevents the pump impeller from reversing or air ingestion caused by refrigerant water backflow when the pump stops.

4. Cooling Water/Chilled Water Piping

Although not directly part of the steam system, check valves are typically installed at the pump outlet in the unit's cooling water (inlet to condenser/absorber) and chilled water (outlet from evaporator) systems.

Function: Prevents backflow impact and impeller reversal during pump shutdown.

When large pumps abruptly stop, significant water volume in the network may flow backward due to inertia, potentially damaging the pump body through impact. Check valves effectively block backflow, safeguarding both the pump and piping system.