6.2.3 Methods of manufacture and construction - part 1
The methods used in the manufacture and assembly of large condensers are outlined, and the factors influencing the extent of manufacture carried out at works and site are discussed.
Traditionally, condensers for British turbines of 120 MW rating and above have always been shop manufactured as a multitude of components which are transported to site for final assembly and tubing. As already highlighted in Section 3 of this chapter, however, economic considerations have recently led to a preferred arrangement in which each LP turbine is combined with its own transversely-tubed underslung condenser. This has allowed the development of a modular condenser design so that one, two or three modules can be combined to cover a large range of possible turbine ratings. This modular concept has a high attraction for turbine manufacturers, particularly where they are competing in world markets. Now, before dispatch from the works, the condenser shell sections, tubeplates, support plates, baffles and waterboxes are temporarily assembled and carefully aligned so that final welding of the shell sections can proceed rapidly and efficiently in the power station prior to tubing.
There are a number of advantages to be gained from maximum fabrication and assembly of condensers at the manufacturer's works:
It enables fabrication and erection to be carried out in favourable environmental conditions, with ready access to specialised machinery, welding, fitting, inspection and test facilities.
It provides a location where there is a high density of skilled labour and supervision in the various disciplines.
Conflicting requirements between contractors for space, access, cranage, etc., do not exist. These can lead to reduced productivity which is detrimental to the overall station construction programme.
Manufacturers have not only lifted workshop limitations, which once restricted a modular method of manufacture, but have also overcome problems concerning transport to site. Figure 4.24 shows an example where the modular concept of condenser design has been successfully employed at Heysham 2 power station.