AHG Solutions Guide_Edition 2.7

Contents
Expansion Tanks & Pressurisation Systems
Types of Expansion tanks
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 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.
• Bladder type, which contains a 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.
Regular maintenance required for pre-charged expansion
tanks includes complete draining and pressure testing at
least annually.
Diaphragm Type
Bladder Type
Pump-controlled Pressurisation Systems
Pump-controlled Pressurisation Systems operate as
pressure-maintaining stations with automatic water makeup
and deaeration. Typically, a pump-controlled expansion
tank comprises a tank fitted with a replaceable butyl (bag
type) diaphragm, 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 precharged
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.
Examples of this type of expansion tank include Duraflex
EcoPress and Duraflex EcoPress Compact.
EXPANSION &
DEAERATION
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