Preventing Corrosion: Pressurisation in Closed Loop Systems | BSRIA Guide BG 82/2022

16th February 2023

Oxygen ingress is the leading cause of corrosion in closed loop HVAC systems and in 50% of cases, it is caused by incorrect pressurisation.

To help building owners maintain acceptable pressures in their HVAC systems while accommodating thermal expansion, BSRIA has published new guidance – Pressurisation of Closed Heating and Cooling Systems (BG 82/2022).

The document explains the principles of pressurisation, the different types of equipment used, and the calculation procedures following both British and European standards.

The guide has been developed with a steering group of industry experts, following discussions on the importance of pressurisation in closed heating and cooling systems.

Why is pressurisation important?

Correct pressurisation prevents corrosion, costly remediation and system failures and saves building owners time and money.

When detected through a remote monitoring system, changes in pressure indicate often lead to air ingress, meaning oxygen is entering the closed loop. We know that dissolved oxygen (DO) is the precursor to all corrosion in closed heating and cooling systems; either directly damaging pipework and components or by creating the perfect conditions for bacteria to thrive.

Remotely monitoring a range of parameters, including pressure and DO, is the most important action building operators and FMs can take to keep their HVAC systems healthy and operational.

Contact us today to discuss your remote monitoring requirements.

What causes incorrect pressurisation?

Incorrect pressurisation occurs when there are leaks within the system and/or general degradation of pipework and components. This can be caused by planned maintenance activities, neglect of monitoring and maintenance, or heavy-handed water treatment practices.

If the pressure drops too low, oxygen can penetrate the system through automatic air vents.

Conversely, if system pressures become too high, water will disperse through safety relief valves and increase the intake of fresh make-up water, contributing to increased DO levels and dilution of inhibitors.

How can remote monitoring help?

Early intervention is crucial to preventing the problems caused by incorrect pressurisation.

Rather than waiting for a physical sign of distress, Hevasure’s real-time monitoring technology continuously monitors pressure to ensure the system is air-tight – something that is particularly important following planned maintenance activities, such as flushing or repairs.

We use Hevasure’s system because it is the most comprehensive available on the market. The unit tracks a range of parameters that can be indicative of corrosive conditions, including:

  • Dissolved oxygen
  • Pressurisation
  • Make-up water
  • Conductivity
  • Temperature
  • pH
  • Galvanic current
  • Crevice corrosion

Readings are taken every 15 minutes, providing a ‘live’ picture and allowing any deviations from specified parameters to be immediately rectified before damage occurs.

If you would like to find out more about our maintenance and monitoring services, contact our expert team today.

BSRIA 82/2022 is available to buy or download from the BSRIA Bookshop (free for BSRIA members)