About our Mini Vessels

Mini-vessels are the ideal solution for protecting heating system components from damage.

Mini Expansion Vessels / Shock Arrestors

About our Mini Vessels / Shock Arrestors

Altecnic’s range of mini expansion vessels and shock arrestors offer the ideal solution for protecting system components from damage, as well as preventing water hammer. Most of the mini expansion vessels we offer can be used as either a vessel to be installed on the cold feed to a boiler or unvented cylinder to allow for the expansion of hot water in a small system, or as a shock arrestor to be installed near appliances to combat water hammer.

What does a mini expansion vessel do?

Mini expansion vessels accommodate small increases in system volume and can also be used as a shock arrestor to prevent water hammer in plumbing systems. They are the ideal solution for protecting system components from damage.

How does a mini expansion vessel work?

In a closed hot water circuit the water cannot be compressed so any increase in volume, created by an increase in temperature, has to be accommodated by an expansion vessel. As the temperature in the system increases, with the associated increase in pressure and volume, the expanded water enters the bladder creating additional volume and lowering the pressure. When the temperature decreases, the pre-charge pressure forces the water from the bladder and back into the main water circuit.

Where should a mini expansion vessel be installed?

Mini expansion vessels should be installed close to the boiler or unvented cylinder, usually in a vertical position with the air chamber at the top. Alternatively as close as possible to the source of shock, i.e the solenoid valve/washing machine.

How does a shock arrestor work?

Mini expansion vessels can also be used as a shock arrestor to prevent what is known as water hammer. This is an effect that occurs in enclosed piping when water flow is turned on or off suddenly. This causes shock waves to run through the pipes which can lead to extensive damage to the system as well as creating noise.

To combat this, a mini expansion vessel or shock arrestor will absorb any excess pressure and dampen any adverse effects.

Altecnic also offers a mechanical shock arrestor which consists of a cylinder divided into two chambers and a piston with two ‘O’ ring seals. The closed chamber acts as a damper due to the compressibility of the air trapped inside. The open chamber is connected directly to the system and is filled with water. When a pressure surge occurs, the force from the spring and the compression of the air counteracts the thrust on the piston allowing a small change in volume which absorbs the excess pressure and starts to operate at pressures >3 bar.

This type of shock arrestor is designed for a single outlet, such as a tap or washing machine, or a small group of services, such as a bathroom supplied via a manifold.