Effective water treatment and the development of hydronic stability are vital to the performance of circulating pumps, says Martin Wilkinson.
Many people are aware of the link between water treatment and system performance, but they often rely on using corrosion inhibitor chemicals alone to achieve what they perceive as the best means of providing system protection.

Chemical dosing certainly has a role to play in system performance, but it is only one part of the treatment process and if used in isolation doesn't make a significant contribution to pump performance. Hydronics is the use of water as the heat transfer medium in heating and cooling systems. Good 'hydronic stability' is the foundation for a healthy system that will last.

Four key elements need to be addressed to provide optimal conditioning of the system water (and therefore help to ensure optimal pump performance). In order of importance, they are pressurisation, deaeration, dirt separation and chemical treatment. Pressurisation: Any pressurisation problems will increase problems arising elsewhere within the system.

Deaeration: Using a combined vacuum deaerator and pressurisation unit provides the opportunity to remove the air from the refill water before it
even enters the system.

System resistance

The presence of excess air in the system adds to the degree of system resistance and increases the amount of electrical energy required for the
pumps to operate effectively in order to move the fluid around the system.

This increases expense and can adversely affect the system parts and overall performance. Cavitation of pumps seriously reduces pump performance, resulting in a varying flow rate and pressure.

It also increases energy consumption and can impact negatively on the pump's performance, often damaging its internal parts or leading to additional pump vibration. Excessive vibration can, in turn, result in damaged pump parts such as seals and bearings.

System noise also increases in this scenario and cavitation can lead to catastrophic failure of the pump impeller, resulting in serious downtime issues and considerable cost implications. Effective deaeration procedures, both at the commissioning stage and throughout the life of the system will reduce electrical consumption and minimise corrosion.

Dirt separation: Effective dirt separation techniques speed up cleaning of the system at commissioning and work to achieve long term protection for major plant and equipment.

If you're encountering dirt problems in your system it is also important to consider the cause of the dirt in the first place to get to the root of system problems.

It is likely that poor pressurisation and a lack of adequate deaeration are responsible and this will need to be addressed before the pumps are allowed to fail due to 'aggressive and abrasive water' being present. Unlike traditional strainers that require considerable effort to clean, dirt separators are more likely to receive their annual maintenance as they only require a simple blow down of the unit, subsequently this is less likely to be ignored by the facilities companies.

Corrosion protection

Chemical treatment: Chemicals work in conjunction with other aspects of water treatment and their addition can help provide the best conditions for cleaning systems, whilst affording a degree of corrosion protection. However, the addition of chemicals can only be truly effective in the longer term by adhering to a strict maintenance regime.

All of the above have a role to play in hydronic stability and only by understanding all of them (and the interaction between them) can a satisfactory solution be achieved.

Hydronic stability ensures correct pressure throughout the system with air levels reduced to an absolute minimum. It also provides the benefit of system cleanliness and means that expensive chemical treatment can be kept to a minimum. Critically, it contributes to the efficiency of system components, including the pump(s).

When hydronic stability is achieved, operating and maintenance costs can be reduced and system life maximised.

An integrated approach to the design and procurement of all four elements is desirable and detailed, accurate specification is vital in this equation, as is a correct understanding and application of the current standards.

Within the commercial sector it's quite common for different companies to be responsible for the different elements detailed above, so this can lead to misunderstanding or disregard for the inter-relationship between these elements.

It is by understanding the system and the inter relation between the four key elements that we can solve the underlying issue and eradicate the air problem within the system.

• Martin Wilkinson is a director of Spirotech UK