The first Mersey road tunnel

Ventilation of road tunnels became of importance with the de­velopment of the internal combustion engine and the conse­quent carbon monoxide pollution. The Mersey road tunnel was conceived in the 1920s as an infrastructure improvement which, in a time of high unemployment, would give work to many. It was designed with a state-of-the-art ventilation system to reduce the carbon monoxide concentration and to maintain visibility. The fan stations still dominate the Liverpool skyline, Figure 1.29 a Liverpool fan building along with the Liver building, and the Anglican and Catholic ca­

Thedrals. Many claim that the fan buildings, are, however, of the greatest architectural merit (Figures 1.29 and 1.30).

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SECTION A. A.

Figure 1.32 Walker’s “Indestructible” fan

The nearest fan manufacturers to the tunnel, capable of con­structing units of an appropriate size were Walker of Wigan and Sturtevant with a head office in London, but, importantly, a main works at Denton near Manchester. Each made bids and were so unlike each other as to cause the tunnel authorities much an­guish. Walker offered its Indestructible design (Figures 1.31 and 1.32) — what else?

Sturtevant at that time had a French Chief Engineer named Lebrasseur. He designed a new backward curved bladed cen­trifugal fan which by appearance was the progenitor of today’s modern fans and which for performance was far in advance of those currently available (Figures 1.33 and 1.34). The design, known in Sturtevant parlance as the GV/M was in reality the Grande Vitesse-Mersey thus showing an early French predilec­tion for the use of these words. Unable to make up their minds, the authorities split the contract between the two companies, but not before the GV/M had proved its efficiency of greater than 80% on a test tunnel 46 metres long and with a cross-sec­tion 3.7 m x 3.7 m. The blowing fan tested had a capacity of 82 m3/s.

Thirty fans in total were installed, duplicated to give running and standby capacity. The total operating supplyflowrate was about 1917 m3/s and that for extract 1211 m3/s. It is of interest to note that the Walker Indestructible fans had impellers about twice the diameter of the Sturtevant GV/M type, but operated at a maximum speed of only 62 rev/min. All these fans have been operating almost continuously since 1934 and in 1994 cele­brated their 60th anniversary.

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