The challenge
It was recognised early in CHt’s assessment that plant replacement would be one of the key drivers for the project, and would require considerable planning input. During one of the initial programming meetings, the site team identified that a large element of enabling works would be required to the existing boilers and natural gas systems to enable their phased removal and replacement.
In addition, survey works established that there was insufficient capacity in the medical gas infrastructure to support the new development, and the original riser and distribution network did not have sufficient isolation valves to enable the future phases of asbestos strip out to proceed without causing significant disruption.
CHt’s challenge therefore was to provide a new gas supply to the existing steam boilers to enable the facade of the boilerhouse to be removed, to allow for removal of the existing boilers and the positioning of the new plant. The hospital was served by three large steam boilers which generated the process steam for the various departments, and the low temperature hot water ( LTHW) for distribution throughout the estate was delivered via an underground service duct and riser network, with the hot water service (HWS) distributed along similar lines to the LTHW. The existing steam generation plant was manufactured and installed in the early 1970’s and was approaching life expiry. The existing steam generation plant had an installed load of 19.5 MW and a demand of 9.5MW of which 3.5MW was associated with the process steam.
CHt was also required to install new isolation valves into the existing steam distribution pipework from the three steam boilers, to enable them to be removed and replaced one at a time.
Our approach
Our proposal was to upgrade the energy generation plant and install two new steam generators, four new LTHW boilers, and two plate heat exchangers and storage vessels to provide the HWS generation and distribution, complete with renewed and upgraded interconnecting pipework systems, and automatic controls systems.
This involved an installed heating load 8MW with the steam generators providing the process load independently. The upgrade of the hospital's medical gas infrastructure required additional mains supplies to be installed in the existing service risers. In addition, the existing medical gas riser systems had insufficient isolation valves to allow the isolation of the ward areas for the future asbestos strip out works. To counteract this, we installed isolation valves into the existing medical gas infrastructure and connected floors 2, 3 & 4 to the new mains.
The engineering behind our delivery
Medical gas infrastructure
To enable the isolation valves to be installed, the medical gas systems, Oxygen, Entenox, Nitrous Oxide, surgical & medical air and vacuum systems were shut down one by one over the course of a weekend, and the wards and theatre areas were supplied with medical gas via a system of bottled gas supplies.
The new isolation valves enabled the later phases of the asbestos removal to be carried out in a much safer manner, with the medical gas services to the areas isolated. The new infrastructure mains allow additional capacity and flexibility to the hospital as the redevelopment progresses.
Boilerhouse upgrade
The works were completed over three phases, initially with the installation of the new gas header and associated boiler connections, followed by the installation of the new steam header, condensate lines and associated enabling and isolation valves and finally the connection of the new gas header to the site wide gas distribution network.
The new gas header was assembled off site at CHt’s manufacturing facility in Oldbury. The philosophy behind its installation was to give flexibility to isolate and remove the existing steam boilers in a phased manner.
To achieve this, we installed a new 250mm gas header, and provision was made to feed the gas supply to the two new steam generators and the four new LTHW boilers from the new gas header, as well as the three existing steam boilers.
CHt Enterprise Solutions was employed alongside CHt to install the BMS services to the pump skids, steam generation plant and LTHW boilers.
Following successful plant commissioning, the boilers were brought onto line and provided the LTHW load for the hospital from the first week in September, with the steam generation plant being brought on line to deal with the process load one week later.
The completion of phases one and two, and the hospital’s conversion to the new LTHW boilers and steam generation plant allowed the removal of the second of the three existing steam boilers, and the positioning of the new HWS plate heat exchangers ( HWS PHX’s).
The final phase of the boilerhouse upgrade involved the removal of the final steam boiler and the positioning of the remaining two LTHW boilers and the final two flues. The final plant positioning allowed the remaining two boilers and associated pre-manufactured pipe spools to be completed along with the associated flues, power supplies and building management systems.