386 MODERN STEAM PRACTICE . for double - ported valves , that is to say , there are two steam passages at each end , and one central passage , in communication with the condenser . The joints should be placed metal to metal , all planed or surfaced in the boring lathe , and the rubbing surfaces… … for the slide valve should also be carefully ; planed as smooth as possible , and then scraped to a face plate , before the slide valve is fitted , which should also be care fully faced on the plate , and thus both surfaces will only require a finishing touch . All the other joints are made steam -…
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