Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Reexamination Certificate
1999-06-18
2002-08-20
Buiz, Michael Powell (Department: 3753)
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
C137S486000, C137S551000, C073S204110, C073S861000
Reexamination Certificate
active
06435207
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a flow regulation control valve for setting and measuring volume flows in pipes, in particular in pipes of supply systems. The invention makes it possible for an actual state of a volume flow to be recorded with the aid of measuring instruments with evaluation and display devices and for a desired state to be set by means of a control member of the valve.
Piping systems distribute a conveyed medium to individual usage points within a building or in a plant. Such piping systems usually have a large number of branches, and there is the problem of guaranteeing a supply which meets the respective demand under full load at the individual usage points. The ability to make an adjustment is needed for the most unfavourable operating state of a piping system, in which all the users demand the maximum supply at the same time. In this case, the supply to the users, for example heat exchangers, should neither be insufficient nor excessive. For this purpose, it is known to adjust the individual pipe sections accordingly.
Flow regulation control valves which are fitted with connections for pressure-measuring lines are useful for this purpose. A separate pressure-measuring device which can be connected thereto measures the differential pressure inside the valve between two measuring points which are spaced apart from one another. There is usually also a shut-off member for the flow control valve located between the two measuring points. After the differential pressure has been measured, the instantaneous volume flow is determined with the aid of existing specific characteristic values of the valve and knowledge of the position of the shut-off member relative to the associated seat. By changing the position of the shut-off member, the volume flow is changed in order to establish a desired volume flow by means of further measuring and control operations. Such valves for section control are known from the publications DE-C 40 30 104, EP-A 0 671 578 and WO 92/03677.
This kind of section control is very time-consuming and cumbersome, and it is even more awkward to carry out in the case of large and branched pipe sections. In this context, it is also known use measuring computers to convert the differential pressures measured in section control valves into the respective throughflow volumes. For this purpose, the specific data of a valve must be stored in the measuring computer. To do so, it is also absolutely essential to know the momentary position of the shut-off member in relation to the associated seat. Changing the position of the shut-off member causes a change in the throughflow volume. Depending on the construction of the valve, the respective stroke or rotational position of a shut-off member of a flow regulation control valve must be recorded by the operator and, in addition, entered manually into the measuring computer.
Although such flow regulation control valves permit an exact setting of the throughflow volumes in different pipe sections, they also have many disadvantages. There is the risk of the measuring bores in the housing becoming soiled. Considerable measuring errors may occur if the necessary pressure-measuring lines have not been vented with extreme care. Furthermore, the assembly and the disassembly of the measuring lines at the pressure measuring points of a pressurized housing in which high temperatures and/or pressures can prevail constitute a great potential hazard. To avoid inaccuracies in the measurements which result due to the occurrence of eddies inside the housing which have adverse effects on the measuring parameter, sufficiently long settling routes are usually required in front of and behind the measuring points in order to assure sufficient measuring accuracy. The handling of the overall measuring device is also very awkward.
Another type of adjustment of pipe sections is known from the product TACO-SETTER, which is published in the catalogue of the company Gebrüder Tobler AG, Haustechniksysteme, CH-8902 Urdorf, 1994 edition, pages 2.59 and 2.60. This is a throughflow measuring device which can be inserted directly into a piping system and has an integrated fine control valve. The throughflow volume displayed by the throughflow measuring device can be changed with the aid of the fine control valve. However, this solution has the disadvantage that its use is limited to clean liquids. Due to the mechanical construction of this throughflow measuring device, periodic servicing and additional monitoring outlay are required. In the case of soiled media, incorrect measurements are therefore to be expected. Additionally, such a throughflow measuring device which is installed directly in the flow path also changes the flow resistance in the piping system. Attempts have been made to avoid the latter disadvantage by arranging the throughflow meter in a bypass line around a shut-off valve. Although this solution improves the operability, it brings about a reduction in the measuring accuracy.
A sensor in the form of a pressure monitor with integrated temperature measurement is known from FR-A-2 713 764. This sensor, which is to be installed in a pipe, has a diaphragm which reacts to changes in pressure. If stipulated threshold values are exceeded, a switch-on or switch-off signal is emitted. With the aid of the temperature recording device, the presence of a flow is also determined at the same time and is displayed with the aid of additional devices.
DE-A 34 32 494 discloses a regulating and/or control arrangement for regulating or controlling the throughput of gas or liquid flows in pipelines. This device is intended to permit flexible configuration of industrial or technical plants to facilitate changes or expansion. The solution proposed for this provides for the actuating element, the actuator, the sensor and the control device to be combined into one structural unit and for it to be possible for this unit to be inserted as such into the pipeline. This collection to form a single structural unit is intended to permit easier installation at the suitable point in a pipeline. By comparison with the previous regulation systems, which were constructed from discrete components and require more space, the simpler connection technique of the individual components, which are accommodated in a single housing and are fed by a common power supply, is an advantage. According to
FIG. 1
, however, this actuating unit has a considerable overall size. It must be constructed to be at least sufficiently large to be able to accommodate a three-way valve, parts of the pipelines connected to the three-way valve and a relatively long pipeline section in which a sensor is arranged at a distance from the three-way valve. The sensor has to be arranged at a large distance from the three-way valve in order for the pipeline section, which acts as a quieting section, to be able to balance out the flow turbulence which occurs within the valve. The document is always concerned only with a sensor which is used in a pipeline and which, depending on its construction, can record different physical, chemical or biological states of a medium.
The actuating unit, which is configured on the building-block system, can always be fitted with only one sensor, it having to be ensured that the control variables output by the various sensors which can be used are compatible with the input signal values of a control device. In addition to the control variable input to the control device from the replaceable sensor, there is a further permanently arranged sensor as a temperature sensor. Since in many applications the temperature constitutes an interfering variable and can impair a regulation process, the interfering variables output by the permanently installed temperature sensor, and the controlled variable supplied by the replaceable sensor, which is in contact with the conveyed medium, are conditioned in the control device and processed to form an activating signal in which the interfering variable has been compensated for.
This solution, in the form of an au
Gabelmann Torsten
Illy Alois
Mewes Frank
Ruckert Heinz-Juergen
Buiz Michael Powell
Krishnamurthy Ramesh
KSB Aktiengesellschaft
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