4 Valve Description
19 of 72
0570.81/22-EN
For fitting a body pressure relief valve, (
Section 4.5.1, Page 21) (see type series
booklet 7300.1) a connection branch 131.2 with connection dimensions Ø 22 mm /
14.1 mm (or 12.3 mm) is welded to body 100. The connection branch is supplied
closed.
Body pressure relief valves, if ordered, are supplied unassembled, i.e. attached loosely
to the gate valve.
Instead of fitting a body pressure relief valve, the operator may also provide a means
of pressure balancing between the body’s middle section and the gate valve’s
pressurised connection branch, e.g.:
▪
a pressure balancing hole in the seat ring or
▪
an external balancing line.
In this case the gate valve can be used for one flow direction only.
If gate valves and swing check valves in pressure seal design (bonnet 139) are fitted in
close proximity to one another, meaning that the trapped liquid could heat up if the
valves are closed, the operator must fit a body pressure relief valve.
Gland packing 461, which seals off stem 200, is tightened via gland follower 452 by
means of studs 902.3 and nuts 920.1. Stem 200 is moved in the axial direction by the
rotating threaded bush 544, which is fitted with cylindrical roller bearings 323. Stem
200 lifts off wedge discs 360 or presses them against seat rings 515.
Threaded bush 544 is positioned in the yoke head by intermediate flange 729 and
hexagon socket head cap screws 914.1. Handwheel 961 sits on threaded bush 544, to
which it is keyed using key 940. It is secured by circlip 932.
The stop nut 920.3 fitted on stem 200 serves as a travel stop in closing direction. It
prevents jamming of the wedge assembly in the seat and is secured by parallel pin
562.3.
Fig. 7:
Parallel discs
Unlike wedge gate valve designs, slide gate valves feature two parallel discs 368,
which are flexibly mounted in disc holder 367. The discs are supported and pressed
against seat rings 515 by replaceable disc springs 950.1 with parallel pin 562.1.
