This type of arrangement is especially intended for so-called service valves that are used to control flows of water in municipal water mains, but also in connection with other types of valves placed in the ground. The selected term "stop valve" is therefore to be interpreted in its widest sense, i.e. to include also e.g. control valves of different types.
A drawback of many prior-art stop valves is that they are used relatively rarely and therefore, after being in use for some time, tend to jam or be clogged. The jamming part generally is the actual stop means of the valve, which in most cases is a slide adapted to run in a corresponding seat in the valve housing. The slide is supported and operated by means of a valve spindle mounted in a valve bonnet. The valve bonnet is arranged on top of the valve housing and is, by means of bolts and an intermediate seal, tightly arranged on top of the valve housing. The valve spindle extends in a sealed manner through the valve bonnet and has an upper end intended to engage a wrench rod, by means of which the valve spindle can be rotated.
Before arrangements of the type briefly described above came into use, it was necessary to dig up a jamming valve for cleaning or renovating. With arrangements of the type at issue, of which one is disclosed in GB-A-2,118,687, in which also a tool is described for use in connection with renovation of valves, this is no longer necessary.