Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1996-12-23
1999-08-10
Ferensic, Denise L.
Fluid handling
Line condition change responsive valves
Direct response valves
137529, 137906, 138 31, F16K 1500
Patent
active
059343184
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a valve system for a space which is under vacuum in relation to its surroundings. The valve system comprises a valve unit which is arranged in association with a wall which delimits the space and has a wall opening through the wall. The valve unit comprises a valve which is normally shut and closes the wall opening but is arranged to be opened and allow air from the surroundings into the space if the vacuum, should exceed a previously defined value. The valve comprises a valve housing which can be connected to the wall in association with the wall opening. The valve housing has at least one inlet opening for air, a passage for the air between the inlet opening and the space, a valve seat and a valve body which is normally pressed against the valve seat by an external force with counteraction by the vacuum in order to keep the passage closed when the vacuum does not exceed the defined value but permits the passage to be opened by the force executed on the valve body when the vacuum exceeds the defined value.
BACKGROUND TO THE INVENTION
There is a need in many areas of application in industry, in particular within different process industries, to be able to limit the vacuum in apparatus, containers, treatment vessels, conduits and the like in which a space in the apparatus or equivalent in question is normally under a certain vacuum. Within the pulp and paper industry, for example, there are many points at which apparatus is operating under a certain vacuum. For example, vacuum pumps are used to deaerate pulp suspensions. In this context it is important that the vacuum does not exceed a given value as fibre pulp would otherwise be able to get into the vacuum pump. For this reason, it is customary to arrange vacuum valves in the wall which delimits the space which is under vacuum, with the valve being set so that it opens and allows air into the space if the vacuum exceeds a certain value. In this connection, it is known to use valves of the type described in a general fashion above, with the external force for pressing the valve body against the valve seat, with the counteraction of the force developed by the vacuum, being produced with the aid of a mechanical, coil-shaped spring, whose spring constant can be regulated using a screw, for example. A disadvantage of these known valves is that the spring must be relatively long, resulting, in turn, in the whole valve forming a long protuberance on the apparatus, conduit or equivalent in question. This results in the valve being readily subject to damage due to external action, particularly since the apparatus, conduit or equivalent, and consequently the valve as well, is often located in those environments where there is a high risk of damage.
BRIEF ACCOUNT OF THE INVENTION
The object of the invention is to make available a valve system of the type specified in the introduction, where the valve unit itself can be made to be very small, as a result of which the risk of mechanical damage due to external action can be decreased substantially. These and other aims can be achieved by means of the external force being obtained from a source of pneumatic power. More specifically, the source of pneumatic power can consist of a separate unit which is arranged at a distance from the valve unit and is connected to the valve unit via a conduit. Preferably, the power source consists of an air accumulator which contains air at a certain excess pressure in relation to the surrounding pressure.
The valve unit can comprise a pneumatic cylinder with a piston and a piston rod, or equivalent, which is in mechanical communication with the valve body, with the power source, preferably an air accumulator, being arranged to develop a pressure in the cylinder, and thereby a force on the piston, which force is transferred to the valve body via the piston rod or equivalent.
It is preferable for it to be possible to regulate the volume of the air accumulator, as a result of which the system can be adjusted so that the valve is open when a ce
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Ekholm Rolf
Jansson Ulf
Farid Ramyar
Ferensic Denise L.
Kananen Ronald P.
Kvaerner Pulping Aktiebolag
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