Holdfast Training Services Trial Blog

This blog will focus on preparing for pre-commissioning flushing of one of the LTHW and CHW systems at Battersea. As a means of introduction and for those that aren’t sure, flushing is the cleaning of pipework to ensure that it is free from debris, settled solids, suspended solids and certain bacteria. This is to ensure that sensitive equipment isn’t damaged (plate heat exchangers and terminal units) when incorporated into the system, that commissioning valves can operate correctly and that microbiologically induced corrosion doesn’t occur.

The contractors involved are:
Skanska Rasleigh Weatherfoil (SRW)- Main MEP contractor
Price Building Services (PBS) – Pipework trade contractor
PH Water & Air Technologies (PH) – Flushing trade contractor
Wyse Power (WP) – Temporary services

When looking at flushing a system there are four basic elements that need to be in place (I’ve annotated who is responsible for each element):
1. A water supply – Down to Carillion to supply
2. Electrical supply (for pumps to get up to required flushing velocities) – Carillion to supply
3. Drainage – Carillion and SRW to supply
4. A complete system – SRW to supply via PBS

I have been managing the preparation for flushing from Carillion’s point of view. This has meant ensuring that points 1 to 3 are in place to meet SRW’s requirements and also ensuring that the approach SRW will take complies with the employer’s requirements which essentially means complying with BSRIA’s BG 29/2012. In reality my main focus hasn’t been on the technical detail and has been on the simple task of trying to prevent SRW from flooding 6 floors of semi-fitted out apartments. The following is worth noting:

Water supply – The permanent Boosted Cold Water Supply (BCWS) on site was not yet installed, therefore a temporary supply was required. This was fairly simple to sort out. I gained confirmation from PH on what their requirements were (a 50mm supply) and then arranged for WP to install a spur from our site temporary supply (50mm) into the plant room where flushing would be taking place with a double check valve fitted to the end for PH to connect onto. If I’ m honest this was a bit of a gamble on my part. As I’ve come to learn this is just a game. Points 1 to 3 above were down to me to sort out. The target start date for flushing the system was 17 Aug 15 therefore in order to avoid a relevant event occurring (JCT term for something which causes delay) and delay notice being issued by SRW I has to ensure we had a water supply. The reason why this was a gamble is that although I was tapping into a 50mm site supply, this supply comes from 2no 5000l break tanks which back in Aug were supplied by a 25mm pipe. PH had a discharge license for 10000l a day and therefore there was a risk that PH’s activities could disrupt the water supply to site. Why did I take this gamble? I knew SRW would not have their system complete in August and I knew a larger water supply was coming to site in the near future. By putting my supply in I protected Carillion contractually – it’s much harder to prove a supply isn’t up to the job than it is to highlight that there isn’t a supply in place at all. What is more frustrating is that I needn’t have taken this gamble at all. I have subsequently read BSRIA’s BG 29/2012, which gives clear guidance on the size of supply required in Table 3.

An extract from Table 3 of BSRIA’s BG 29/2012:

less than 2000l system = 25 mm supply
2000 to 10000l system = 40mm supply
greater than 100000l system = 50mm supply

PH were simply asking for the largest supply they could possibly need, without looking in detail at the size of the system, in order to cover their bases. Assuming that our riser pipework remains at it’s largest diameter and the horizontal distribution pipework is the same as the largest size then the volume of the system comes out at 1959l – I only needed to provide a 25mm pipe which would have been met by our 25mm site supply leaving 10000l a day for site use (more than enough). An easy lesson learnt.

That’s just over 700 words, so I’ll leave it there for this blog and provide comment on my part in confirming SRW have completed the system (visual inspections, air test witnessing and NCRs) at a later date.

As an aside I’ve only got two weeks left on site. If anyone on phase 1 knows that they are coming to Battersea Power Station Phase 1 let me know and there may be scope to arrange a visit to site before I depart and switch focus to phase 3.