Ashford’s award-winning approach to flushing systems
Traditionally, vast quantities of clean, potable water are discharged to drain during the dynamic flushing procedure that is part of the pre-commission cleaning process of a closed pipework system. Up to 20 times the system volume may be required, which has to be discharged to drain.
Not only are vast quantities of water used, but the aggressive chemicals that are added as part of the cleaning process generate a chemical effluent which may require treating before discharging to drain.
Ashford Environmental Services has developed a different approach that uses much less water and brings a number of other benefits to the process of pre-commission cleaning. Called the minimal discharge process (MDP®) it has been used on a range of projects, large and small, and recently won an award from the Commissioning Specialists Association in the innovation in commissioning category.
The minimal-discharge process (MDP) is less aggressive and uses much less water, while still achieving the parameters required by BSRIA guidance BG29/2012 ‘Pre-commission cleaning of pipework systems.’ and without compromising water quality.
Roger Carlin, managing director of Ashford Environmental Services, uses as an example a comparison for a large hospital that was commissioned by the company. A conventional flush would have taken 32 weeks and required 1280 man hours. The potential water consumption was 1700 t. An MDP flush took a similar time and required the same number of man hours. However, the actual water consumption was 88% less — at just 200 t.
The conventional pre-commissioning cleaning process requires the following steps:
• initial dynamic flush
• biocide wash
• second dynamic flush
• addition and circulation of cleaning agents
• final dynamic flush
The MDP approach comprises the following steps:
• management of the filling process
• addition of cleaning agents during filling
• dynamic filtration according to the BSRIA guidance
• conventional back flush
The water and cleaning chemicals that are introduced to the pipework system remain in place and become part of the system water. The dosing rig and filtration system are removed.
Once the system has been filled, a water supply and drainage are not required until the final back flush, enabling flushing to start earlier in the programme.
The entry for the CSA awards highlights a problem of the traditional approach of cleaning closed systems using aggressive chemicals. They strip the pipe surface, rendering it ‘active’ and vulnerable to corrosion.
Roger Carlin summarises: ‘The main benefit, apart from the vast reduction in water consumption, is the ongoing management of the filling and pressure test process. We then “police” the system throughout the pre-commissioning and commissioning period using a “permit to drain” system if leaks and/or modifications are required. Ongoing site monitoring also ensures water quality is maintained.’
