Types of expansion tanks

Expansion tanks and pressurization systems play a crucial role in maintaining system pressure within heating and cooling systems.

These components prevent pressure fluctuations, protect system integrity, and ensure efficient operation.

Understanding the types of expansion tanks—such as diaphragm and bladder models—along with pump-controlled systems and static solutions, is essential for selecting the right approach to pressure management. This guide explores the different tank types and their applications, providing insight into how each contributes to system stability.

Static expansion tanks

Static expansion tanks are available in a range of sizes to accommodate various system volumes and are supplied to order pre-charged with nitrogen to the pressure required for the intended installation. The pre-charged expansion tanks come in two types.

Diaphragm type, in which the diaphragm which spans the middle of the tank. The water in the tank is in contact with the tank’s metal inner surface and therefore is unsuitable for potable water.

Examples of diaphragm type expansion tanks include Reflex N Expansion Tanks and Reflex C Expansion Tanks.

Bladder type, which contains a replaceable butyl bladder. Because the water in the tank is completely contained inside the membrane, the risk of corrosion is avoided and the tank is suitable for systems containing untreated water.

Examples of bladder type expansion tanks include Duraflex Joule Expansion Tanks.

Regular maintenance required for pre-charged expansion tanks includes complete draining and pressure testing at least annually.

Diaphragm Type

BladderType

Pump-controlled Pressurisation Systems

Examples of pressurisation systems include Reflex Variomat and Reflex Reflexomat.

Pump-controlled Pressurisation Systems operate as pressure-maintaining stations with automatic water make-up and deaeration. Typically, a pump-controlled expansion tank comprises a tank fitted with a replaceable butyl bladder, a pump and a control panel. This type of system represents a superior method of system pressure management, provides close pressure control, degassing, and water-makeup with BMS interface capabilities.

Pressure control with this type of system is much more fine-tuned and up to 90% of the tank’s capacity can be utilized, compared to less than half that volume with a pre-charged tank (depending on system pressure). This saves a significant amount of plant room space and piping. One pump-controlled expansion tank can be substituted for four pre charge vessels.