(source of this article probably The Engineer)

HE Bryan Donkin Company’s principal business today is with the Gas Industry and reference has already been made to the supply of gas valves from 1847 onwards. Early rotary exhausters, such as the one patented by Joshua Beale of Greenwich in 1848, itself only an improvement on Rarnella’s design of 1588, suffered from the disadvantage that there was great friction between the slides. The speed of the guiding segments on a 38 exhauster running at 60 r.p.m. being as high as 600 ft. per minute. The segments had to run in circular grooves machined in the end plates of the machines.

In 1866 Beale patented (No. 1402) an improved type of exhauster of which the Bryan Donkin Company obtained sole manufacturing rights in 1870. They made about 100 of these in which the friction was reduced by about 20′ by using rings instead of segments and letting only an auxiliary blade slide to take up differences in diameter. .’

In 1877 the same John Beale patented (No. 2419) a greatly improved type in which the friction was only 30-40% of that in the original. Shortly afterwards Mr.Beale retired and the Bryan Donkin Company purchased his business outright. The rings and segments for guiding were entirely abolished in this design and a simple block, brought to the centre, was substituted. In the example quoted above, the velocity of the slide on the guide block became fewer than 60 instead of 600 ft. per minute. The block also had a much greater wearing surface than the segments.

There is still sufficient interest in this long-lived type for “the 1877 patent” to
remain a term in current use within the company.

The cylinders of these exhausters are bored with the horizontal axis a little longer than the vertical. This is an improvement over the true circle as it gives a curve swept by a slide of constant length and was employed originally by Franchot about 1860. An amusing result of this eccentric boring is that on more than one occasion maintenance fitters have “rectified” this ovality under the impression that it was due to wear. They then found the circular bore useless and a new shell had to be supplied.

The great advantage of these exhausters over otter types was the small number of working parts. More than 600 exhausters of the various Beale types were at work by 1897 many of them drive by steam engines supplied by the Bryan Donkin Company. Nearly 100 had been exported with examples in reach of the five continents. The company also made some 3- and 4-bladed exhausters, the pioneer 3-blade type at the Old Kent Road works of the South Metropolitan Gas Company dating back to as early as 1873-4

Another early achievement was the installation of sets of gas boosters at Beckton Gas Works in 1880 which pumped the gas through 4 ft. mains over a distance of 8-10 miles to London. This pioneer installation was one of the very few examples of gas boosting in this country prior to the present century. There were 8 exhausters of the Beale 1866 pattern each of 225,000 cu ft. per hour capacity at 50 rpm. The exhausters could pump 48 million cubic feet a day against a pressure of 48 in w g. they were driven by four steam engines connected to a common condensing plant. Other sets were subsequently installed at Bromley by Bow to discharge gas from that works into the same mains

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