36 TECHNICAL
This issue Patrick looks at the expansion vessel
By Patrick Gordon of Calafrica ( technical @ calafrica . co . za )
This issue Patrick looks at the workings of an Expansion Vessel
Q – How does an Expansion Vessel work ?
A : Expansion vessels are devices designed to accommodate the increase in the volume of water due to the raising of its temperature , both in heating systems and in domestic hot water production systems . They are also used as a “ Hydro-pneumatic Well ” in domestic water distribution systems . the system , the bladder is filled with water and the air surrounding it is compressed ( fig . 1 ). When the vessel has reached its maximum capacity , the system set pressure will be attained and the pump will switch off . When the consumer opens a terminal fitting and the system pressure drops , the compressed air in the vessel will expel the water in the bladder to supplement the pressure drop in the system downstream ( fig . 2 ).
But how do they work ?
Expansion vessel for heating and domestic water circuits An expansion vessel is a closed expansion vessel that is divided into two parts by a membrane which separates the water from the gas ( usually nitrogen ) and acts as an expansion accommodator . Due to an increase in temperature , there is an increase in pressure that takes place in the vessel . In comparison to the pre-charge pressure when cold , ( fig . 1 ) it reaches full compression when the pressure is at the maximum expansion ( fig . 2 ).
Images supplied by Calafrica
Installation It is advisable to install an expansion vessel on the pipe containing the lowest water temperature . For heating systems , the correct installation should be on the return pipe .
For any further information regarding this topic please feel free to contact : Patrick Gordon on + 27 ( 0 ) 83 303 1437 . PA
Hydro-pneumatic well A “ Hydro-pneumatic Well ” consists of a closed container divided into two parts by a bladder . The aperture between the bladder and the tank is pressurised by air / nitrogen and thus constricts the bladder . The pump , activated by the pressure switch , starts up and the vessel starts to fill with water . As the water pressure increases in
“ designed to accommodate the increase in the volume of water due to the raising of its temperature ”
AS AN IOPSA MEMBER , GET YOUR FREE PLUMBING AFRICA SUBSCRIPTION NOW
Take a break from your work and send a message with your email address to 061 809 6254 with PA02
Distribution department : + 27 ( 0 ) 11 579 4940 Email : distribution @ interactmedia . co . za
* Controlled free distribution to relevant plumbing industry role players . | Print copies available in South Africa only .
www . plumbingafrica . co . za @ plumbingonline @ plumbingonline @ PlumbingAfricaOnline November 2023 Volume 29 I Number 9