MARINE ENGINES.

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secured to the seating with nuts, and a central boss at the top, forthe reception of a screwed stud for tightening up or compressingthe spring; one cap being cast along with the valve for the spring torest on, and another cap at the top of the spring on which the screw Fig. 282.—Relief Valve

with fixed Crosshead.

a, Valve . b, Valve seat. c, Spring, d, Cross-head. e, Set screw. F F, Columns. g, Baffiepiece.

Fig. 284.—Relief Valve with Dome.

Fig. 283.—Relief Valve with Stud on Cylinder Cover.

a, Valve . b, Valve seat. C, Spring, d, Cap. a, Valve and spindle. b, Valve seat.

e, Set screw. f, Stud. g, Bafile piece. h, Cylinder cover. C, Spring, d, Bafile dome.

for compressing the spring bears: in this arrangement the valveis guided by the spindle passing through the seating. A verysimple form of this description dispenses with the wrought-ironbow, a stud being screwed into the cylinder cover and end, throughwhich the screw for tightening up the spring passes; while in otherforms the dome fitted over the spring for protecting it from beinginjured, as well as for preventing the water flying about the engineroom, is fitted with a boss at the top, through which the tightening-up screw passes, the dome being bolted to the covers and end withstud bolts. Many prefer a fixed pressure on the relief valve, but,