A new low pressure gas supply capable of delivering a gas load of 5,850 kWh to feed the offices in Heron Tower and the restaurant Sky Bar situated on the 40th Floor.
This project presented a number of challenges due to the site location and the gas pressure required at the boilers:
- The gas meter was to be located in the basement of the new building, 6 metres below ground level, giving rise to concerns over ventilation and pipe routes through supporting walls
- The connection point for the incoming new gas supply was an existing low pressure 355mm MDPE gas main operating at a maximum pressure of 23 mbar, owned by National Grid, located in the centre of Bishopgate. This gave rise to concerns regarding traffic management and minimising disruption to the public during the construction stage
- The required gas pressure at the plant within the building was 21 mbar.
As this is a higher pressure than that which can normally be guaranteed from a low pressure supply, the developer intended to install a Secomak GB 535 gas pressure booster. This needed to be taken into account when designing the incoming low pressure service to ensure gas was not drawn out of the low pressure network in Bishopsgate when the booster started up.
To meet our customer’s requirements we installed a low pressure gas supply comprising of:
- 15m x 250mm MDPE to GIS / PL2 from the National Grid network in Bishopgate to the new site
- 4m x 180mm MDPE to GIS / PL2 within the site to the building
- 5m x 150mm Welded Steel to T/SP/P1 within the building to the meter location in the building
- Connection to existing network by inserting a 355mm x 250mm MDPE tee into the existing gas mains network in Bishopsgate.
As usual, all Fulcrum design and construction works were carried out to comply with the latest gas industry standards, these being principally:
- IGE/TD3 Mains
- IGE/TD4 Services
- IGE/GM/6 Meters and meter locations.
For this particular project we gave special consideration to:
- Liaising with National Grid to ensure that the pressure loss from the main to the meter was kept a minimum in order to reduce the operating range of the booster and the potential impact on the existing network. It was agreed that the boilers would operate in series and fire up in three stages in order to prevent pressure surges in the pipework, which could occur should the full gas load be taken instantaneously
- Liaising with Transport for London to ensure disruption was kept to a minimum by developing a suitable traffic management plan for a site in the centre of London
- Calculation of the thermal expansion of the steel pipe work to ensure that the system integrity is not compromised over a variety of climatic conditions
- Ensuring that the basement meter position had sufficient ventilation in accordance IGE/GM/6 such that any vented gas would pass harmlessly to the atmosphere.
Kevin Walling, Senior Project Engineer (Mechanical) for Skanska said:
"Correspondence with the design office was exceptional. We were kept fully informed of the current progress with the design and delivery of requirements. Liaison with the site agent was good, and initial site discussions on dates and install were progressive."