Expansion Pressure Vessels

TerNPH – low-carbon steel
TerNPH-S – high-alloy steel


Designed for stabilizing medium pressure and maintaining required medium level. Rubber diaphragm separates air chamber from the medium to prevent air from dissolving in the medium and eliminate the need for constant topping-up. Preventing air access significantly reduces system susceptibility to corrosion.

TerNPH vessels do not require additional air with deep well pumps or submersible pumps.


  • separate gas and medium chamber
  • eliminate frequent air top-up
  • compensate system pressure increase
  • higher working capacity compared to water/air vessels
  • sanitary certificate
  • replaceable diaphragm
  • compact design
Expansion pressure vessel TerNPH


The expansion pressure vessel is designed as a cylindrical steel tank (1) with a rubber diaphragm (2). The diaphragm is connected to the water system with K1 and K2 port in the bottom cover (4). The expansion tank is vented with an automatic air vent (10) installed in the top cover (3). The tank shell is fitted with a pressure gauge (5) and pneumatic valve (6) for filling the gas chamber. The bottom heat is fitted with a port (7) for checking diaphragm integrity. Compact design allows to install large capacity vessels in rooms with standard door openings. The extension pressure vessels can be dismantled to replace the diaphragm (2).

Principle of operation

Chamber (A) is connected to the water system with two ports (K1 and K2). The pump draws in the medium and fills the chamber (A). Chamber (B) is filled with air, and the air pressure increases with the volume of medium discharged. If the pressure in the expansion pressure vessel reaches a specific value, the pump is activated and when the water is used, the air replaces it in the tank. If the large volume of water is discharged, the system pressure drops below the preset value, the pump is activated and automatically fills the tank. By releasing or adding air with a pneumatic valve (6) the initial working pressure is adapted to the system requirements. The pressure in the gas chamber can be read on a pressure gauge (5). Chamber (A) is vented with an automatic air vent (10) installed on the top cover (3).

Construction of TerNPH
Construction of TerNPH

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