RETORT-BENCH APPURTENANCES 277
(6) those in which no air floats are employed, but which are rendered buoyant by a counterbalance.
Both types are in common use, but (6) is, perhaps, preferable, owing to the tendency
Fig. 196.—Arrangement of Foul Mains and Rbtobt-Housb Govebnobs for Labge Bench. Note.—Valves (not shown) are bequirbd at the Base or each Govbknor.
of the float casings to corrode. The arrangement of the air ch ambers is shown ii. Fig. 194, and it may be pointed out that for retort-house governors this is preferable to fixing the floats with an exterior annular space as in Fig. 195. With the latter
Fig. 197.—Retort-House Govebnok.
arrangement the governor frequently operates in too “ lively ” a manner for the best results. On the other hånd, for exhauster governors, the annular cham-ber is preferable.
The most suitable place for the governor is on top of the retort bench, and as close up to the end of each section of the foul main as possible. It is not so sensitive when fixed on the inlet or outlet of the condensers, as sometimes found. In a retort house of any size, more than one governor is necessary, and the different sections of foul main will best be controlled by some arrangement as that shown in Fig. 196. By-passes are advis-able whenever they can be arranged for, as the governors will usually require attention. about every four months, when both. tank aijd valve should be cleaned.
A typical governor of the counter-balanced bell type, designed on Parkinson