1 1/2 S.E.A. Piston Rod packing rings

1 1/2 S.E.A. Piston Rod packing rings, for 2 1/2" dia. rod, one of them cut in halves ( Trist's patent 1903-07)

These are examples of the S.E.A. piston rod packing rings patented by Mr. A. R. Trist from 1903 to 1907. They are designed for use with steam or water, and are kept tight by the internal pressure forcing the lips of the rings against the rod. As the rings do not depend on gland pressure for their steam- tightness, the piston rod moves through them with a minimum of friction. The rings are made of a composite laminated material consisting of alternate layers of textile fabric and rubber, vulcanised together and coated with graphite. They are formed with a thick heel and a tapering lip, which is bent inwards and downwards. The rings are placed one on the other in the stuffing-box with the lips against the rod in the direction of the pressure, their ends being butted closely together; header rings of solid packing are placed at the top and bottom, the bottom header ring having an open joint to permit the fluid to pass to the rings. The wide heel of one ring rests on the curved top of the next lower ring, and the inner edge of the heel is made of harder material to prevent it from spreading and filling the arch of the ring, it being essential that the lip of the ring should be free. The gland is screwed up only sufficiently hard to hold the rings tightly together. Experiments have shown that the friction of these rings, when perfectly steamtight, is only about 40 per cent. of that of plain rings. The packings are made in a range of sizes for rods from o·875 in. to 8 in. diam., and in several widths for each diameter. They are also made with a basis of asbestos, cotton or flax.