Fluid handling – Self-proportioning or correlating systems – Self-controlled branched flow systems
Patent
1985-12-24
1987-01-27
Nilson, Robert G.
Fluid handling
Self-proportioning or correlating systems
Self-controlled branched flow systems
417299, G05D 701
Patent
active
046388311
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a valve arrangement for obtaining an unloading liquid flow for cooling a centrifugal pump or the like even when working against a closed supply pipe. The arrangement includes a valve housing containing a non-return valve, the respective closing and opening movement of the non-return valve causing a respective opening and closing of an unloading orifice in the valve housing, such that an unloading liquid flow will be obtained even when the non-return valve is in a closed position within the valve housing.
THE PRIOR ART
Valve arrangements of the noted type, which are also called minimum flow valves, are used to protect centrifugal pumps from overheating when working against a closed supply pipe, for instance a supply pipe for used delivery water to one or more consumers. The fact that a pump is working against a closed supply pipe may be due to the fact that this pipe is connected to a number of independent users, who at any given time may not be using the no water available in the pipe. However, the pump cannot be stopped just because at any given time the water being supplied thereby is not being tapped. As such, the pump will work against a closed non-return valve in the supply pipe with the same water, such that the cooling effect of the water which normally flows through the pump will be reduced, thus causing damage to the pump bearings. This phenomenon will also occur when several pumps are connected in parallel, as the tightest pump will close the non-return valves of the other pumps when there is a low flow in the supply pipe. Empirically it is known that a centrifugal pump for instance must have a flow of about 10% of its whole capacity to cool down the loss of heat arising in the pump when working. Centrifugal pumps for pumping hot water are particularly sensitive to overheating when there is a low flow therethrough or closed valves. In such cases, the pump may also be damaged by hot-water evaporation.
It is well-known that an unloading liquid flow from a non-return valve can be obtained by making its movement govern a special valve so that the unloading valve will be opened when the non-return valve is moved to a closed position. One example of such a valve arrangement includes a lever which is connected to the non-return valve such that, when the non-return valve is moved to a closed position within the housing, the lever will cause the valve body to turn so that a connection will be obtained between the pressure side of the valve housing and an unloading orifice in this housing. The unloading pipe may also be provided with a non-return valve. When having great pressure differences, there are also throttlings arranged in the unloading pipe. The well-known valve arrangement, however, is impaired by the disadvantage of containing several movable parts, bringing about high cost of production and a comparatively unsafe operational reliability.
DETAILED DESCRIPTION OF THE INVENTION
The object of this invention is to provide a minimum flow valve not having the drawbacks of the well-known valves. The object was not obtained by means of a valve arrangement including a valve housing encasing a non-return valve, by the movement of which when respectively closing and opening, a connection will be respectively opened and closed to an unloading orifice in the valve housing, by which a predetermined liquid flow will be obtained when the non-return valve is closed. The invention is characterized in that the non-return valve is connected to a valve sleeve member which is linearly displaceable in a guide element; that the valve sleeve member is provided with an interior duct being in contact with an orifice to the pipe pressure side on one hand, an orifice on the outer sliding surface of the valve sleeve member on the other; that the guide element is provided with a tight plate and in fixed contact with an orifice on its interior sliding surface being in contact with the unloading orifice; and that the sleeve orifice is in contact with the guide
REFERENCES:
patent: 3358705 (1967-12-01), Krechel
patent: 3976090 (1976-08-01), Johnson
patent: 4321940 (1982-03-01), Krechel
Nilson Robert G.
SSAB Svenskt Stal AB
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