Aquaflex Expansion Vessels
Aquaflex Expansion Vessels incorporate a bladder arrangement which provides a flexible barrier between the system fluid and the precharged air in the vessel.
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As the system water expands, the bladder also expands pushing against the precharged air cushion. This is how the expansion is accommodated in a closed-loop system.
Standard construction is carbon cold-pressed steel with natural rubber or EPDM membranes. Temperature limits are 10°C to 99°C. Working pressures vary from 3 Bar to 10 Bar depending upon which vessel is selected. Higher pressure ratings of 16 and 25 Bar are available if required.
Standard nominal tank capacities range from 8L up to 10,000L.
Features typically include:
- Replaceable bladder
- Threaded connections – stainless.
- Pre-set pressure 400 kPa – variable.
- Wall mount bracket available for 8-25 litres.
- Also available in stainless steel.
- Relief valve supplied loose to suit system pressure – please specify.
For more information, download the brochure.
WE CAN HELP YOU CHOOSE THE RIGHT Aquaflex Expansion Vessels FOR YOUR PROJECT
Sizing for Expansion Vessels
In order to select a suitably sized expansion vessel, the following information is required:
- Total system water volume in litres.
- Temperature of water when system is filled (in oC) and average maximum operating temperature (in oC).
- Minimum operating pressure in kPa and maximum operating pressure (10% below relief valve, in kPa).
- Which level of the building it will be installed and number of levels there are above it?

Case Study
View the complete project
PIPE MOUNTED TANKS | |||||||
PART NO. | NORMAL VOLUME (L) | EXPANSION CAPACITY | PRESSURE MAX (KPa) | WEIGHT (KG) | A BSP (INCH) | H (MM) | Ø D (MM) |
6AF2 | 2 | 1 | 300 | 1.1 | 1/2 | 270 | 100 |
6AF8 | 8 | 4 | 300 | 1.9 | 1 | 330 | 200 |
6AF12 | 12 | 6 | 300 | 2.6 | 1 | 310 | 240 |
6AF19 | 19 | 10 | 300 | 3.6 | 1 | 370 | 300 |
6AF24 | 24 | 12 | 300 | 4.8 | 1 | 430 | 300 |
6AF24S | 24 | 12 | 300 | 4.8 | 1 | 325 | 350 |
6AF35 | 35 | 17 | 300 | 5.5 | 1 | 450 | 350 |
PIPE MOUNTED TANKS | |||||||
PART NO. | NORMAL VOLUME (L) | EXPANSION CAPACITY | PRESSURE MAX (KPa) | WEIGHT (KG) | A BSP (INCH) | H (MM) | Ø D (MM) |
6AF2 | 2 | 1 | 300 | 1.1 | 1/2 | 270 | 100 |
6AF8 | 8 | 4 | 300 | 1.9 | 1 | 330 | 200 |
6AF12 | 12 | 6 | 300 | 2.6 | 1 | 310 | 240 |
6AF19 | 19 | 10 | 300 | 3.6 | 1 | 370 | 300 |
6AF24 | 24 | 12 | 300 | 4.8 | 1 | 430 | 300 |
6AF24S | 24 | 12 | 300 | 4.8 | 1 | 325 | 350 |
6AF35 | 35 | 17 | 300 | 5.5 | 1 | 450 | 350 |
VERTICAL TANKS WITH LEGS | |||||
MODEL | CAPACITY (L) | PRESSURE (BAR) | DIAMETER (D) | HEIGHT (H) | CONNECTION (H) |
10AF35 | 35 | 10 | 350 mm | 610 | 25 mm MALE |
10AF50 | 50 | 10 | 350 mm | 760 | 25 mm MALE |
10AF80 | 80 | 10 | 425 mm | 930 | 25 mm MALE |
10AF100 | 100 | 10 | 480 mm | 990 | 25 mm MALE |
10AF150 | 150 | 10 | 480 mm | 1080 | 25 mm MALE |
10AF200 | 200 | 10 | 500 mm | 1120 | 32 mm FEMALE |
10AF300 | 300 | 10 | 640 mm | 1250 | 32 mm FEMALE |
10AF500 | 500 | 10 | 750 mm | 1490 | 32 mm FEMALE |
10AF750 | 750 | 10 | 800 mm | 1920 | 50 mm FEMALE |
Frequently asked Questions
A diaphragm type tank has air in the diaphragm and water between it and the vessel. A bladder tank is in the reverse of this, that is water in the bladder and air between it and the vessel. This means there is no contact between the water and mild steel vessel, thus eliminating the potential for rust. Furthermore, the partial acceptance, that is the expansion capacity, of a diaphragm tank is 50%. So for a 100L tank for example, expansion capacity is only 50L. However on a bladder tank, the partial acceptance is 65-80%, depending on the model. This means more expansion capacity out of tank the same size.
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Masterflow is and has been a trusted name among Australia’s HVAC suppliers for over 20 years. We supply a wide range of pump types and can provide the ideal solution to the many and varied fluid requirements that face the industry. We pride ourselves on remaining agile, innovative, and having fast turn arounds. We are local! All our pumps are locally designed, built and manufactured here in Australia.
