Modern Gasworks Practice

602 MODERN GASWORKS PRACTICE concrete and the joints are readily accessible. The plates of purifiers should be designed with as few different patterns as possible, whilst an eye must be given to Fig. 362.—Milbourne’s Cover Fastener, showing (<i) Catches Shut, and (6) Catches Open. the avoidance of awkward Castings. When the plates are large, they must be adequately stiffened. Some means should always be provided for by-passing the Fig. 363.—“ Eclipse ” Cover Fastener, showing Rubber Joint. separate tiers of material should this be necessary owing to abnormal back-pres-sure. Special tier-valves are made for the purpose, although a mild-steel plate attached to a rod passing through a stuffing-box on the purifier will answer the