Valves and valve actuation – Reciprocating valve – Gate
Patent
1981-12-10
1984-04-10
Rosenthal, Arnold
Valves and valve actuation
Reciprocating valve
Gate
251328, 251329, F16K 312, F16K 4102
Patent
active
044416881
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Field of the Art
This invention relates to a bonnetless compact design gate valve in which a yoke is directly screw-joined, with no bonnet being provided, to the body of an outside-screw type compact design gate valve having its fluid conduit passage smaller in diameter than the pipeline connected thereto, thereby to attain a weight reduction of the valve. Further, the seat ring to be fixed in said fluid conduit passage is so designed that it will not become loose in use and is effective for shutting off the high pressure fluid.
2. Background of the Art
There are known outside-screw type compact design gate valves having their fluid conduit passage formed smaller in diameter than the pipeline connected thereto. Such gate valves are generally standardized in, for instance, the American Petroleum Institute Standard 602, and they are widely used in petroleum refining systems and other petrochemical apparatuses. Usually, a gate valve is used for the purpose of shutting off or passing a fluid in a pipeline, and it is so constructed that the gate is moved perpendicularly to the fluid contact passage to fully open or fully close said passage. In order to minimize the pressure loss of the fluid passing therethrough, the fluid conduit passage is formed equal in diameter to the pipeline connected to the valve.
In the case of the small-sized, or so-called compact design gate valve, the fluid conduit passage is formed smaller in diameter than the pipeline connected thereto so that there is a certain pressure loss of the fluid, thereby to attain a sizable reduction of the unit valve weight as well as the weight of the whole apparatus using a plurality of such valves and to also realize an improvement of the working efficiency of piping assemblage and a saving of labor. However, these small-sized gate valves are substantially of the same construction as the large-sized gate valves known in the art. That is, both the body and the bonnet have the respective integral flanges which are joined together by bolts to integrally combine the body and bonnet. Therefore, even though the fluid conduit passage of the valve is formed smaller in diameter than the pipeline connected thereto to attain a certain weight reduction of the unit valve, such effort is not fully effective because of the provision of thick flanges and strong bolts used for joining the body and bonnet.
Further, at the joint of said flange a gasket is provided for preventing leakage of the fluid from this section. This gasket has sufficient toughness and is designed to attach tightly enough to inhibit leakage of the fluid in use of the valve, but once a leakage of the fluid occurs, there is no effective measure to check such leakage. If leakage occurs from the gasket joint, there is no alternative but to replace the gasket with a new one by blocking the fluid flow in the pipeline connected to the valve and disconnecting the body and bonnet.
Moreover, in the case of a valve with a small diameter such as less than 2 inches, it is extremely difficult to properly fix in the conduit hole the seat ring which is adapted to attach against the corresponding face of the wedge-shaped gate to block the fluid flow. As means for fixing the seat ring, there are known the following two methods: a screw is formed on the outer peripheral wall of the seat ring and it is screwed into the fluid conduit hole provided with a mating screw; or the seat ring is formed cylindrically and it is expanded after it has been fitted into the fluid conduit hole. However, the former method has difficulties in providing a screw thread in the direction not parallel to the fluid conduit hole but vertical to the wedge face of the gate, that is, transverse to the fluid conduit hole. On the other hand, according to the latter method in which the seat ring is merely expanded in and pressed against the fluid conduit hole, there could occur sliding between the pressed faces when, for example, a high-temperature fluid is blocked, due to a difference in coefficient of linear expansion owing to a
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