JP2530482B2 - Differential temperature sensor and measurement system incorporating the sensor - Google Patents

Description

The present invention relates to differential temperature sensing devices and systems incorporating same, and in particular to improved split-well differential temperature sensors, and water in pressure vessels such as vapor extraction tubes. A measurement system incorporating the improved sensor for detecting presence.

As is known, differential temperature sensors utilize thermodynamic and fluid principles to selectively sense the presence and / or occurrence or termination of a liquid or gaseous stream. U.S. Pat.No. 3,366,
No. 942 (Deane) discloses an example of a known differential temperature sensor utilized as a flow stop detector. This sensor or probe has one heater probe thermally connected to one
It consists of a pair of thermal sensing probes, the sensing probe and the heater probe being introduced into the conduit through which the material flows. The heater probe is in close proximity to one of the pair of sensing probes, and when there is no flow, this sensing probe near the heater probe will be hotter than the other sensing probe and the fluid material When flowing and passing through the probe, heat is removed from the heater probe, causing a temperature difference between the sensing probes to disappear or disappear.

US Pat. No. 3,898,638 (Deane et al.) Has the same basic structure as that of the older Deane Patent No. 3,366,942, but a differential temperature sensor in which the internal structure of the temperature sensing probe is modified to improve the measurement accuracy. Is disclosed. As described in that patent, the selective heating of both temperature sensing probes by the heater probe is accomplished by, for example, the heat distribution between the heater probe and one of the temperature sensing probes located closer to the heater probe. Convection and / or conduction in the stationary medium and conduction in the shunt, although accomplished by the channels, also contribute to the selective transfer of heat to both probes.

Similar to the differential temperature sensing probe described above, another embodiment of the differential temperature sensor including a pair of temperature sensors and a heater element disposed close to one of the temperature sensors is disclosed in US Pat. No. 4,449,403 (McQ).
ueen). Due to its special application, the MCQueen device requires the use of a large number of such sensors in the form of vertically stacked arrays within the reactor vessel guide tubes, and the output from these multiple sensors is especially relevant to the fuel rod area. Indicates the wet / dry state of the coolant in. In such a reactor vessel, particular attention must be given to the presence of voids, for example, voids due to steam, which displaces the reactor coolant from the fuel rods, resulting in undercooling and is likely to cause overheating. Three states,
That is, a decoding device used for sensing the properties of a coolant under a subcool state (normal operation state); saturated liquid (boiling state); and saturated vapor (void state) is disclosed in detail. As described in the patent, in the wrong condition, a "water hammer" effect that causes pressure pulses appears, which may destroy important equipment such as pipes, pipe support structures, tanks and valves. is there.

U.S. Pat. No. 4,440,717 (Bevilacqua et al.) Also discloses a measurement system in which a plurality of sensors are arranged in the reactor vessel at intervals in the vertical direction, and each sensor uses one of a pair of thermocouple wires. It includes a heater for heating and detects the level of the cooling liquid in the container by measuring not only the absolute temperature of each but also the temperature difference between the two, and here again, heat transfer to liquid and heat to gas or vapor are detected. Liquid level is sensed by utilizing the difference in heat transfer characteristics between transfer. Similar sensors and related systems used in nuclear vessels or other pressurized water systems are described in US Pat. No. 4,418,035 (Smith
And No. 4,439,396 (Mr. Rolstad). Smith Patent No. 4,418,035 also discloses a block diagram of a multifunction monitor system utilizing such a sensor.

The differential temperature sensor and measurement system of the present invention have a wide range of applications such as use in measurement and monitoring of a pressure vessel of a reactor system as in the case of some of the above-mentioned patents. And was developed in connection with preventive maintenance. In generators of this type, the problems caused by the inflow of water or cold steam into the steam turbine are exacerbated as the equipment ages, especially as it is often operated cyclically and / or in alternation. If the equipment malfunctions in the heat cycle, the above inflow may occur in various places such as the main steam inlet pipe, high temperature reheated steam inlet pipe, low temperature reheated steam pipe, extraction pipe, packing-holding type steam sealing system, turbine drain. There is. In addition to structural damage and mechanical malfunctions caused by the inflow of water or low temperature steam, unexpected equipment outages are also serious problems.

In addition to identifying where the inflow occurs, the type of inflow that occurs, ie, the type of water inflow event, must be identified. For example, inflow may occur in the form of a water film in the pipe on the turbine side, which is often due to steam condensate or overspray conditions on the cold side of the pipe. It can also appear in the form of droplets or "granular" streams, which appear to be large and small in the form of continuous droplet jets mixed with steam. So-called slug flow may occur. That is, it is a phenomenon in which a water mass clogged in a part of the pipe flows down in the pipe, possibly accompanying the discharge of water. Two-phase flow has also been observed, which is commonly referred to by the vague definition of a "water steam" mixture, due to the release of high-energy water, which includes a central flow of condensed water. Finally, there is a broad category of water rising in pipes due to condensate, spray or flow, feedwater heater tube leaks, and / or poorly designed drainage diameters. However, most of the water inflow events are slow rising types that belong to the last-mentioned category, and are thought to appear as a precursor to other types of water inflow events. Accordingly, the design system of the present invention is primarily concerned with the last-mentioned broad category and is aimed at monitoring conditions in pipes, and in particular detecting relatively slow rises in water in pipes associated with turbine systems. And As already mentioned, this source of water comes from boilers and feed heaters, accumulation by condensate, faulty spray equipment and ruptured pipes, accumulations due to condensate inside the turbine itself during operation in the wet area, etc. Is.

In addition to the sensors disclosed in some of the patents listed above, commercial systems have already been developed that incorporate a differential temperature sensor to monitor and detect the presence of water. That is, Solartron Tr, a company owned by Schlumberger
Solartron Protective Systems, a division of ansducers, is a “Self-Validating Water Induction Monitoring Syst
"em (self-confirming water inflow monitoring system)" is marketed under the registered trademark HYDRATE CT-2455D. Resistance measurement is performed in the manifold by electrodes that function to discriminate between water and steam (or air) resistance. As described in the sales document, the feed end of the electrode is connected to the manifold body to serve as a reference electrode, which is insulated from the manifold body by a high-purity insulator. It is attached to a two-port manifold of a conduit, such as a drainage pipe, so that each electrode detects the presence of water or steam and its output is sent to a discriminator circuit via an independent circuit. According to the discriminating circuit, a fault check of the components and an indication of any faults in each electrode channel are indicated and a validity check between two electrode channels under the same operating conditions. Is based on an indication of whether a fault exists or not, but Solartron's H
The YDRATECT-2455D system is problematic in many respects and essentially cannot be expected to have reliable service life. For example, the sensor is generally cylindrical and can be inserted and secured through the pressure vessel sidewalls, similar to conventional systems of this type. One segment forming the cylindrical structure consists of an annular band of insulating material that insulates the electrode tip of the sensor from the rest of the structure. The interface between the insulating strip and the electrode and the rest of the cylindrical side wall of the sensor must be pressure resistant, eg magnetic / metal welded. The dissimilar material, that is, the interface between the porcelain and the metal, leaks or is caused by the sensor structure, especially considering that this sensor structure is used in a harsh environment (for example, periodic temperature change or vibration). Make it extremely susceptible to damage. In the light of experience, the useful life of such sensors is at most 1 to 3 years. Not only is this type of sensor not durable enough to be an effective monitoring system, but it is extremely leaky and prone to damage, which is a very dangerous factor for workers. Also, due to its structure, the sensor cannot be repaired or replaced while the monitored system remains online.

Another example of a commercial system is Fluid Components, In
c. products, the above-mentioned patent No. 3,366,942; 3,898,638
And the brochure "Liquid Level &Interf" that mentions protections for the systems disclosed in No. 4,449,403.
ACE Controllers ", that is, using a sensor incorporating the probe disclosed in the above patent to measure temperature differences. The value of the output signal depends on the medium in contact with the probe. It can detect not only liquid / gas and liquid / liquid interfaces, but also wet / dry states, etc. Although a monitor circuit and a calibration circuit are shown as a liquid level and interface control means for moving with a sensor, The sensor and associated control means are unsuitable for use in the harsh environment of a steam turbine system, especially for providing the sensing necessary to predict water inflow. Is unable to withstand the high pressure, high temperature conditions present in steam turbine systems, and the sensors are asymmetrical, which allows the present invention to provide effective and reliable monitoring of steam turbine systems. Essentially lacking dual functions that have proven to be essential for monitoring and control.
Fouling tests performed by the sensor of the present invention and related systems cannot be performed by asymmetric sensors and systems incorporating it. Moreover, since it is not of a double structure, it is not possible to automatically switch a failed element, for example, a heater element, in the online state.
In addition, due to the structure of the sensor, the failed heater and / or thermocouple element cannot be physically replaced in the online state. Also, such a sensor, and therefore the associated system, will absorb heat faster than water even at low steam velocities and therefore cannot be used under steam flow conditions unless there is a shield surrounding the heater and thermocouple elements.

Despite incorporating technological advances, commercially available sensors and monitor / alarm systems utilizing them, as reported in the above references, have not met the urgent needs of industry. For example, despite much attention and research since the early 1970s, the problem of water inflow in steam turbines has not been fully resolved.

As water inflow phenomenon becomes a serious problem, ASME (American
Society of Mechanical Engineers
Established Committee on Turbine Water-Damage Prevention, and ANSI / ASME standard No. TDP-1-1985 contains plant design recommendations to prevent water damage.
Recently, the research conducted by the assignee of the present invention on behalf of EPRI in an operating power generation facility was reported by EPRI in the report CS-
The final report "Detection of
Water Induction in Steam Turbines.Phase III: Field
Demonstration. "This research shows that the demand for reliable sensor and monitoring systems that can be used in the environment of steam turbines to detect the serious problem of water inflow is extremely urgent. Emphasized.

Reliably detects serious water inflow problems that are likely to occur in steam turbine equipment, as well as liquid / gas (vapor) conditions and / or any changes in other high pressure, high temperature environments, such as are present in a reactor vessel There is still an unfulfilled need for improved differential temperature sensors and associated monitor / alarm systems to do so. Perhaps most important for water inflow monitoring systems for steam turbines are sensors and associated control systems, often for many years, until the system responds to indicate the occurrence of water inflow. The fact is that it remains inoperative. By the way, during such a long period, it is expected that the electric elements, that is, both the heater element and the thermocouple element, periodically fail due to vibration or temperature change acting on them. Therefore, it withstands high temperature and high pressure conditions, its cycle changes and vibrations for almost indefinite time,
The sensor device itself must have a robust construction and sufficient mechanical strength to provide a highly accurate and reliable output. Since both the heater element and the temperature sensing element may fail in such a sensor, the sensor and the associated monitor / control circuit are not only capable of online testing, but also the heater and thermocouple elements that make up the sensor. It is also required to be able to exchange online. In addition, each sensor contains multiple or redundant components. Similarly, the linked control / monitor circuit automatically generates an alarm when a failure is detected, and automatically switches to a multiple or redundant element when a failure is detected. Must be done.

As a problem closely related to this, the number of through holes for mounting the sensor on the side wall of the container whose condition is to be monitored must be minimized from the viewpoints of structural soundness and installation efficiency. Further, in order to realize the required multiplex configuration and ensure the accuracy of the sensor output, it is a precondition that the states monitored by each multiplex element forming each sensor are almost the same.

Therefore, a main object of the present invention is to provide a dual differential temperature sensor capable of overcoming the above problems and the drawbacks of the known art and satisfying the above-mentioned conditions, and a measuring system incorporating the same.

For this purpose, the present invention is a differential temperature sensor that includes a generally cylindrical shank having a central axis and is attached to and extends through a pressure vessel sidewall, each of which comprises a first
And a pair of essentially the same probe having a second end and originating from an integral junction of the first end and the shank and laterally spaced from the central axis. Defining a smaller diameter perimeter, the shank penetrating through the shank coaxially from its free end, the bottom wall defining a generally cylindrical chamber intersecting the central axis near the integral joint. , A central hole for accommodating a heater element extending in a parallel relationship with the central axis from the bottom wall in each of the probes and reaching near the second end of the probe, and a symmetrical position with the central hole interposed therebetween. Occupy 1
A differential temperature sensor is proposed which is characterized by defining a pair of second holes for accommodating a pair of sensing elements.

The sensor of the present invention is configured to provide a given level of accuracy and reliable monitoring capability while minimizing the number of reliable and safe pressure vessel through holes.
Once installed, the sensor does not have to be removed for testing or repairing the heater and sensor elements. The metrology system of the present invention constantly performs on-line sensor testing to ensure that all components are operational. This is extremely important for a normal water inflow monitoring system, as mentioned above, which will not operate for many years until it responds and directs the occurrence of water inflow. Corrective action is taken to provide appropriate display and alarm indications to avoid damage that would occur if water inflow were not detected.

The duplex configuration of the sensor offers many advantages. For example,
A verification test and a fouling test can be performed by automatic switching between complementary elements, and when a failure of the element is detected, it is automatically replaced with a complementary element, so that it is continuous despite the failure of the element. Various monitors are possible.

Since the shank is connected to the pipe or container wall, it acts as a heat sink to insulate between the heated and unheated semi-cylindrical probes of the pipe or container wall, increasing the accuracy of the thermocouple output. The heater and thermocouple leads are connected via cables to the external monitor, control and power circuits by attaching a connector box to the top free end of the shank. The sensor structure of the present invention allows the element to be locked in the insertion position while still allowing online access to the heater and thermocouple for replacement without removing the thermowell housing. .

The measuring / monitoring system of the present invention continuously conducts a continuity check of the heater of each sensor probe and a pair of thermocouple elements associated therewith, and if any of these elements fails, the measuring / monitoring system appropriately performs the check. Instruct. When a defective element is detected, the system of the present invention automatically switches to the complementary element set to compensate for and eliminate the defective element. This guarantees continuous operation of the sensor and prevents false alarms resulting from device failure. That is, the sensor functions as the differential temperature sensor described above.
Denoting the two semi-cylindrical probes by A and B, the heater A may first be powered. Thermocouples A1 and A2 arranged symmetrically
One of the thermocouples B1 and B2 of probe B, for example A1
For example, use with thermocouple B1. If either thermocouple A1 or B1 fails, the system automatically switches to the respective complementary thermocouple A2, B2. Similarly, if heater A fails, the system automatically switches to heater B. Of course, the temperature difference indication (ΔT) must have the same value and opposite signs. The switching capability provided by the dual configuration of the sensor allows automatic guarantee of the faulty element without damaging continuous monitoring and without causing false alarms. In addition, the heater A and the heater B are switched during the online test, and the respective outputs appearing as a result are compared, and the same value and the opposite sign Δ
By confirming that the T-mark is formed, the system will increase the effectiveness of the test by ensuring that the sensor is not clogged with foreign objects between the probes themselves or between them and the calibration is still valid. To be

The sensor and associated monitoring system of the present invention will be described in further detail with reference to the accompanying drawings.

FIG. 1 is an elevational view showing a housing 10 of a split cylindrical thermowell sensor of the present invention, which will be described with reference to the bottom view and the top view shown in FIGS. Sensor housing 10
Is preferably machined as shown to form a cylindrical rod made of metal such as stainless steel having excellent mechanical strength but low thermal conductivity. One end of the rod is machined to form two identical, substantially semi-cylindrical, sensor probes 12A, 12B, the sensor probes 12A, 12B being separated by cutting their boundaries 13. Probe 12
The ends or tips 14A, 14B of A, 12B are further machined to form chamfered portions 15A, 15B. Therefore, probe 12
The opposite ends of A and 12B, or the bases thereof, integrally project from the shank portion 20 of the sensor housing 10, and a collar 18 having a diameter slightly larger than the outer circumference of the probes 12A and 12B is provided for the purpose of the shank 20 and the sensor 12A. , 12B to form a joint. Pipe threads are formed in portion 22 of shank 20 to allow housing 10 to be attached in a known manner to a corresponding threaded boss that is welded to the steam pipe. An annular mounting protrusion 24 is formed on the outer surface of the upper free end of the shank 20, and threaded holes 26, 27 are formed in the annular end surface 28 of the shank 20 for purposes described below.

By piercing the shank 20 from the upper free end, it penetrates the majority of the entire length of the shank 20 coaxially and the probe 12A, 1
A substantially cylindrical chamber 30 is formed that reaches a bottom wall 32 near the proximal end joint of 2B. Central holes 34A, 34B are formed from the bottom wall 32 in an axially parallel relationship into the probes 12A, 12B, respectively, to reach positions near their tips 14A, 14B. Holes 34A and 34B (not shown in FIGS. 1-3) are for accommodating elongated cylindrical heater elements as described below. Holes 36A1, 36A2 and 36B symmetrically arranged with the holes 34A and 34B sandwiched therebetween.
1, 36B2 each have a length that is about 2/3 of the axial length of the probe 12A, 12B, respectively, and accommodate a corresponding thermocouple element (not shown in FIGS. 1-3).

The sensor housing 10 has a total axial length of about 15 cm, a maximum diameter of about 5 cm, and the threaded portion 22 corresponds to a standard 3.8 cm pipe tap formed on the boss for mounting the housing 10 as described above. . Slot 13 to separate sensor probe 12A, 12B
The width of the probe may be about 3 mm, and the outer diameter of the probe 12A, 12B is about
mm is fine. The holes 34A and 34B of the heater element have a diameter of 6.6 mm,
The depth measured from the bottom wall 32 is set to 7 cm, and the holes 36A1, 36A2 and 36B1, 36B2 of the thermocouple element have a diameter of 3.5 mm and a depth of 5 cm.
Should be set to. Each of these holes is further cut to form a countersink with a slightly larger diameter and a depth of about 0.7 cm. These countersinks are the same as the corresponding holes, but with dashes 34A ', 34B', 34A1 '... 34B
2'is attached.

FIG. 4 is a cross-sectional view of the sensor housing 10 taken along the line 4-4 of FIG. 5 in a cutaway plane showing a complete assembly of sensors. A protective screen 40 having a hole 42 in the cylindrical side wall 43 and often a hole in the bottom 44 is also provided on the sensor probe 12.
Place around A, 12B and weld bead 46 at its upper free end
It is fixed to the collar 18 of the shank 20 of the sensor housing 10. The main function of the screen 40 is to reduce the vapor velocity around the sensor divider or probe while still allowing water to enter. The high vapor flow rate cools the heated sensor probe as effectively as water. Therefore, by providing holes 42 symmetrically on screen 40, a minimum or limited flow rate can be directly contacted with the sensor probe when the sensor is placed in the flow path, i.e. defined within screen 40. Enable contact within the sensor / chamber. The holes 42 are symmetrical with respect to the probes 12A, 12B, but are not necessarily evenly arranged around the cylindrical side wall 43 of the screen 40, and are arranged so as to match the flow direction,
The sensor must be properly oriented with respect to the direction of vapor flow during installation.

The extension assembly 50 encloses the electrical connector box 60 in the housing 10.
Removably attach to the upper free end of. The lower end of the assembly 50 is telescopically fitted to the annular protrusion 24 of the housing 10, and is welded to the upper end of the bottom wall 61 of the box 60 as indicated by the weld bead 52. In order to make it easy to understand, FIG.
A notched plane along the line is shown. The extension assembly 50 includes two elongated tubes 53A, 53B which, as seen in FIG. 4, have countersinks 34A 'for receiving heater elements A, B (not shown), respectively. The bottom end fits into 34B ',
The upper end of each reaches the same level as the upper surface of the bottom wall 61 of the connector box 60. Similar to the tubes 53A and 53B,
However, tubes 53A1, 53A2 and 53B1, 53 with a smaller diameter than this
B2 has its bottom end with corresponding countersinks 36A1 ', 36A2' and 36B
Fitted in 1 ', 36B2', and extending to the upper surface of the bottom wall 61 of the connector box 60 like the tubes 53A, 53B. The bottom wall 61 includes a central hole 62 for accommodating the various tubes described above.

A plate 63 is arranged in the connector box 60 so as to overlap the hole 62 and close the hole. While the threaded rod 64 is screwed into the threaded hole 26 of the sensor housing 10, the rod 63 is projected upward from the hole 65 of the plate 63, and the nut 66 is screwed into the hole so that the plate 63 and the connector via the plate 63 are connected.・ Box 60 and extension assembly 50
Is fixed to the sensor housing 10. Holes 66A, 66B are formed in the plate 63 for passing a conductor wire to the heater element (not shown), and holes 67A1, 67A2 and 67B1, 67B2 corresponding to the 44 thermocouples housed in the sensor housing 10 are formed. Formed on the plate 63. FIG. 4 shows the thermocouple 70 inserted into the plate 63 with the upper end cut away. A true arc ring 72 is fitted around the upper end of the thermocouple 70, and engages with the lower surface of the plate 63 to fix the thermocouple 70. Spring type snap rings 74A, 74B fit into slots formed in the sidewalls of the corresponding tubes 53A, 53B (not shown in FIGS. 4 and 5) to secure the heater element in the corresponding holes 53A, 53B. are doing. Connect the terminal plate 80 to the bottom plate 61 with screws and nuts 82A and 82B.
A and 80B are fixed and 6 pieces are attached to each probe half.
Insert terminal screws 84A and 84B in sufficient numbers to connect to the wires from the 12A and 12B thermocouples and heaters.
Installed in A and 80B.

As shown in FIGS. 4, 5 and 6, the cover plate 86 has four hanging side surfaces 87, covers the upward bent end 61 a of the bottom plate 61, and is fixed by the self-tapping screw 88. Engagement holes 89, 66b for inserting a cable (not shown) used for connection with the connection screws 84A, 84B of the terminal plates 80A, 80B are provided.

FIG. 7 shows a heater element 90 used in the sensor of the present invention, which comprises a generally cylindrical heater element portion 91 having a lead 93 extending from a grooved tip portion 92. As shown in FIGS. 4 and 5, the grooved portion 92 is fitted with a clip 74 for fixing the heater element 90. A preferred commercially available heater element is the Watlow Com, St. Louis, Missouri.
There is a FIREROD CARTRIDGE HEATER (code name EIA51) for manufacturing pany, diameter 6mm, length 7.5cm, 120V, 80
Watt.

FIG. 8 is a plan view of a thermocouple 95 which can be used in the present invention, which comprises an elongated, generally cylindrical body and a wire 96. A preferred commercial thermocouple that can be used is manufactured by Marlin Manufacturing Company of Cleveland, Ohio.
There is a Model CAIN-18U-10RP, the structure of which is 4th and 5th.
It has a length of about 25 cm suitable for accommodation in the sensor housing 10 and the extension assembly 50 shown in the figure.

FIG. 9 is a block diagram of a measurement and monitoring system for multiple sensors as shown in FIGS. 1-8 of the present invention. FIG. 9 shows two sensors, namely
Although only sensor I and sensor II are shown, the system will typically include a larger number of sensors. Since the configuration of each sensor is the same, the dual internal elements of the probe are only shown for sensor I. The sensors I each have a heater (HTR), as indicated by the same reference numbers as in FIGS.
A, a heater (HTR) B, thermocouples (TC) A1 and A2, and thermocouples (TC) B1 and B2. Similarly, the sensor I and corresponding processor I include a heater control circuit 100 and a thermocouple control circuit 102, each of which connects to the system controller 104 via bidirectional buses I (HC) and I (TC). Device 104 also includes multiple bidirectional buses II.
(HC), ... and II (TC), ... through a plurality of processors II, ... and the associated sensor II, ... corresponding control circuit (HC and TC), Bidirectional bus 10
It is also connected via 6 to the central display and operator control panel 108. As will be described later in detail, the heater control circuit 100
Under the control of the system controller 104, performs calibration, on-line test (for example, continuity check and short-circuit to ground), alarm instruction processing, and heater A / B switching of the sensor I. Similarly, under the control of the system controller 104, the thermocouple control circuit 102 performs a similar function for each thermocouple A1, A2 and B1, B2, such as online testing and automatic switching in the event of device failure. .

FIG. 10 illustrates in partial block diagram detail of the measurement and monitoring system of the present invention for a single processor I (ie, the processor shown in FIG. 9) including the heater control circuit 100 and the TC control circuit 102. As shown, the respective interface circuits in the control circuits 100 and 102.
Reference numerals 118 and 129 connect the internal components of these control circuits and the system controller 104. Heater elements HTR A and HTR B are independent of each other for continuity check / current check / calibration (“CCCFC
C ") is connected to an adjustable power supply 116 via a device 110 and a switching selection circuit (SELECTOR) 112. The display device 114 is a heater element HT.
It includes alarm lamps 116 and 118, which correspond to RA and HTR B, respectively, and which are independently turned on by corresponding outputs from the device 110 when a failure occurs in the corresponding heater element. The cooperating devices 110 and 114, the device 112 and the adjustable DC power supply device 116 are connected to the system control device 104 via the interface circuit 118 and the corresponding bus as shown.

The system controller 104 automatically adjusts the output of the DC power supply 116 according to the state detected by the CCCFCC device 110 and the selection of the heater element HTR A or HTR B performed by the operation of the selector 112 by the system controller 104. By doing so, the heat outputs from the heaters A and B are made equal. The device 104 also displays a heater failure on the central display panel 108, as described below.

The sensor shown in FIG. 10 has four thermocouples (TC) A1, A2, B1, B2.
Including the same as the conventional configuration in the differential temperature sensor,
One thermocouple of probe A is associated with the corresponding thermocouple of probe B and connected in series in a bucking or vice versa relationship. That is, as shown in the figure, the thermocouple elements TC A1 and TC B1 are connected as a cooperating pair, and the thermocouple elements TC A2 and TC B2 are connected as a second or complementary pair, and the two pairs Are represented by TCP-1 and TCP-2, respectively. Continuity check device 1
21 intermittently checks the continuity of the thermocouple of each pair, and if an abnormality is found in the continuity and an element failure is detected, an output is sent to the TC failure alarm device 120 and the thermocouple TCP-1
Alternatively, the alarm lamp 120-1 or 120-2 corresponding to TCP-2 is turned on and an output is sent to the system controller 104 to display a failure on the central display panel 108 as described later.

The selector device 122 supplies two TC TEMP CIRs for supplying one of the outputs ΔT1 and ΔT2 to the interface circuit 129.
It is controlled so as to select one of the outputs of CUIT 124-1 and 124-2. TC TEMP CIRCUIT 124-1, 124-
The selected one of the two outputs a voltage signal STEMP that is proportional to the temperature difference (ΔT) sensed by the selected thermocouple. The interface circuit 129 connects the devices 121, 122, 124-1 and 124-2 to the system controller 104 via the corresponding buses as shown. The device 104 also selectively displays ΔT on the central display device 108 during normal monitor operation, and automatically and verifies and displays the alarm status of each sensor on the central display device 108, as will be described later.

FIGS. 11A, 11B and 11C show various displays of the display and operator control panel 108 of FIG. 9 and the arrangement of control modules. The eleventh readout and control module 130 includes a digital display 132 which indicates the value and sign of the temperature difference ΔT (° F) measured by a given sensor and selected for display as described below.

Under operator control of the switch 140, the system can be set in the automatic test mode, indicated by the lighting of the lamp 138, or in the selective test mode, indicated by the lighting of the lamp 139, in which the operator Any one of the plurality of sensors can be tested, as described in detail below. The momentary actuation of switch 142 provides a "test all sensors" or "test single sensor" mode of operation as described below. The digital display 132 can only be operated by the operator and displays the ΔT of any sensor. The "Failure Sensor" lamp 135 and "Failure Heater or TC (Thermocouple) lamp" 136 indicate the corresponding alarms, which are described in detail below. By pressing switch 137, all indicator lights in the system can be tested.

FIG. 11B shows extraction monitor 150. Since many such monitors are used in a typical turbine system, a plate 152 is provided to identify the particular function being monitored, and thus the location of the associated sensor. Sensors are placed at the corresponding alarm lamps 155, 156, 157 and 160 of the extraction tubes associated with the turbine as shown schematically on the monitor board 150. Specifically, the alarm lamp 15
5 corresponds to the sensor located on the turbine side of the isolation valve 158,
The alarm lamp 156 corresponds to the sensor located between the isolation valve 158 and the check valve 159, the alarm lamp 157 corresponds to the sensor located in the lower part of the extraction pipe and the alarm lamp 160 corresponds to the high temperature in the heater. Corresponds to a sensor located in the heater to detect the water level condition. When water is detected by a given sensor, the corresponding alarm lamp on monitor board 150 is automatically turned on.

Since multiple monitors of different types can be incorporated into the system, a corresponding monitor display and control panel incorporating alarm lamps similar to the monitor panel 150 will be provided. One example is the water monitor board 170 shown in FIG. 11C, which includes alarms 1001 to 1004. As described above, the present invention includes different types of monitors, each of which has a corresponding monitor display and control panel, and the number of monitors required for each type.
Only the extraction monitor panel 150 shown in FIG. 11B is considered below as a representative example.

In the following, the system of the present invention and its operation will be described in relation to the ninth, tenth, eleventh and eleventh. In order to properly understand the operation of the system, one must understand the multiple configurations inherent in the sensor of the present invention. In connection with the sensor I schematically shown in FIG. 10, the selector 112 selects the heater HRT A and the selector 12
2 is a thermocouple consisting of thermocouples TC A1 and TC B1 TCP-1
Suppose you choose. Under normal operating conditions (and thus in the absence of water surrounding the dual probe A, B of sensor I) TC A1 is heated by HTR A and RC B1
Senses a temperature higher than that sensed by, and produces a positive ΔT output STEMP for a reference polarity or direction with each output as a pair. On the other hand, if the complementary heater B is selected, energized and substituted for heater A, then under this same analytical condition, the ATEMP output will be negative ΔT, ie the numerical or absolute temperature difference value will be the same. The signs are opposite. As previously mentioned, the calibration circuitry of device 110 controls the power levels supplied to heaters A and B under the direction of system controller 104 and through the adjustment of adjustable DC power supply 116 to control HTR A and If the same heater output is generated in HTR B and the sensor is not clogged, ΔT with the same absolute value is generated.

The system of the present invention uses the heater B in place of the heater A (or vice versa) to ensure a continuous monitoring function when the heater A fails, and avoids false alarms that would otherwise result from heater failure. Therefore, by switching between the heater A and the heater B, the advantages of the dual sensor can be exhibited.

With respect to the TC control circuit 102 shown in FIG. 10, the duplex configuration of the sensor also significantly enhances the capabilities of the system including the thermocouple. That is, if the continuity check circuit 121 detects that one or both of the thermocouple elements of the TCP-1 has a failure, the selector 1 is controlled by the system controller 104.
22 automatically switches to the second pair TCP-2 and TC TEMP circuit 12
Apply the output to 4-2 and get the value SPEMP (ΔT) from the circuit. As shown in FIG. 10, the RCP-2 is a thermocouple TC A1 and
It is connected in the same direction as the complementary first pair TCP-1 consisting of TC B1. Therefore, the complementary pair of heater elements HTR A and HTR B
When TCP-2 is selected, the same sign ΔT is formed. Of course, TC A2 and TC B2, ie, to RCP-2
By reversing the direction of TCP with respect to TCP-1, a more complicated structure having a larger failure indication capability can be obtained.

Physical replacement of the heater and thermocouple elements that make up the sensor (as distinguished from automatic switching) can be done online after the faulty element is identified by the processor I, which can be located remotely from the control panel 108. . In the drawing, the HTR and TC failure alarm display units 114 and 120 are incorporated in the heater control circuit 100 and the TC control circuit 102, respectively. However, the display units 114 and 120 may be arranged in a place where maintenance personnel can easily see them. When a defective element is detected, the alarm lamp 116 or 11 corresponding to the heater A or the heater B is detected.
8 or alarm lamp 120-1 or 120-2 corresponding to thermocouple TCP-1 or TCP-2, respectively, is lit.

Both heaters A and B and / or both thermocouples TC
Failure of P-1 and TCP-2 will render this sensor channel inoperable to prevent false alarms. Also, the common mode blinking of lamp 136 (FIG. 11A) and the alarm lamp corresponding to the failed channel indicates to the user that this channel has failed and is inoperable.

As will be described later, automatic switching is performed to verify the sensed alarm condition. Specifically, if the water level rises and surrounds both probes A and B, the normal ΔT value drops significantly below the alarm threshold, but not zero. Therefore, the alarm condition is automatically verified by switching the heaters and comparing the corresponding ΔT values of STEMP. If the numerical values are not the same (however, the signs are opposite), it is concluded that the sensor I is clogged with foreign matter and the lowered ΔT value is a false alarm. However, as a result of the verification test,
If a sensor failure becomes apparent, the operator has been alerted to the need for system maintenance. The system operation displayed and controlled on the control display / operator control panel 108 will be described based on the above background.

First, consider the normal operating state. Monitor in the “auto” or “select” test mode
By pressing the corresponding alarm lamp / switch on 150, for example alarm lamp / switch 155, the ΔT of each sensor in the system can be determined. An alarm lamp / switch, eg, a delay circuit triggered by actuation of 155, maintains a ΔT indication on the display 132 of the module 130 for a predetermined time, eg, 2 minutes. Monitor board
The delay circuit is reset when another alarm lamp / switch on 150, for example 156, is activated.

As already mentioned, these same alarm lamps / switches will light up when the corresponding sensor senses an alarm condition. Also, as previously mentioned, the system performs an automatic verification test on the sensor channel indicating the alarm condition by switching the heater before the alarm indication occurs. However, the sensor for which one of the heaters has failed is not switched for verification.
The switching function is in one of three different forms:
One "automatic test" mode, as described below,
It is done in either of two manual or operator controlled modes.

Specifically, when switch 140 is set to the automatic test mode position to illuminate lamp 138, system controller 104 responds to an alarm condition detected by a given sensor to perform a verification test on this sensor. Performs switching function (However, as already mentioned, this sensor
If a heater failure in the channel does not prevent the switching test, then an alarm is raised based on only a single heater functioning in the sensor). When ΔT is generated, which has the same numerical value but opposite signs (thus, the absolute values of both are less than or equal to the alarm threshold), an alarm is issued. If the difference between the two ΔT values is larger than a predetermined value, for example, 3 ° F, the false sensor arm is emitted as described above. This alarm is cleared by switching switch 140 to the central neutral position or Selective Test Mode (139). In the preferred embodiment of the system of the present invention, in the "automatic test mode", the switching test is performed according to predetermined criteria only on the sensor channels which indicate an alarm. Further, in the automatic test mode, the switching test is performed for only one cycle in response to the alarm instruction. Furthermore, switch 14
When a 0 returns from the neutral or "select test mode" position to the "auto test mode" position, any channel that is alarming will be switch tested before the alarm is triggered again.

The second type of switching test switches switch 140 to the "select test mode" position (which causes lamp 139 to illuminate) and at the same time switch 142 to single sensor.
The operator can make a selection by momentarily depressing to the Test position (142) and momentarily depressing the alarm lamp / switch corresponding to the desired channel, eg, alarm lamp / switch 155 on the monitor board 150. Next, the ΔT of the switched sensor is displayed on the display unit 132 of the monitor 130. As mentioned earlier, the delay circuit will
Hold for minutes or until another display prompt is pressed.

A third type of switching test is performed on all channels simultaneously by switching switch 140 to position 139 and momentarily pressing switch 142 to the "all sensor test" position (lighting lamp 144). This causes all sensors to switch from heater A to heater B (or B to A if the intended direction is reversed). Two minutes later, the operator manually turns on the alarm lamps / switches one by one (eg 155, 156, 157 ...
・) Display 1 of module 130 by pressing manually
The ΔT corresponding to 32 is sequentially displayed. The ΔT display value of a series of sensor channels is compared to the previously recorded ΔT of the same channel before all heaters were switched.

In both of these two manual test modes, the operator is asked if an actual alarm condition exists.
That is, whether the ΔT display has the same absolute value below the predetermined threshold (although the sign is opposite) or the sensor is clogged, that is, the numerical value differs depending on the switching position.
Can be verified.

Other checks can be made in the manual style switch test. For example, as already mentioned, if one heater of a given sensor (eg sensor I) fails,
The switching test is blocked and no ΔT change is observed in any of the manual test modes. This identifies the sensor in which one heater has failed. Display 114
And 120 lamps identify the particular faulty heater and faulty thermocouple, respectively.

The fault sensor is identified by the fault sensor lamp 135 and the blinking alarm lamp / switch corresponding to the sensor channel, eg, alarm lamp / switch 155 of control board 150. The faulty sensor is (1) both thermocouples TCP-1 and TCP of a given sensor detected by device 121.
-2 abnormality in conduction; (2) failure of both heater elements A and B of a given sensor detected by device 110; and (3) confirmation of sensor failure by switching test in "automatic test mode" described above. Either result is indicated by the device 104.

By pressing the button 137 on the module 130,
All lamps on the control display / operator control panel 108 (FIG. 10), ie individual modules, eg 130, 152, 170
All lamps can be tested, including specific indicators (Figures 11A-11C) and alarm lamps.

In conclusion, the monitoring system of the present invention outputs from the first active heater element while performing continuous on-line testing, automatic detection of element failure by appropriate fault indication output and automatic switching to complementary sensor element, All sensor locations are constantly monitored and diagnosed by displaying the alarm status of a given sensor, which is automatically verified by a switching test using a complementary second heater element, and alarms are issued as needed. It is possible to eliminate the erroneous alarm caused by the element failure. Besides automatic and continuous online testing,
A selective test mode under operator control is also possible. Essential to these capabilities of the system of the present invention is the duplex configuration of each sensor unique to the present invention. Not only does the sensor of the present invention have a rugged construction for long-term use, but the automatic switching to the complementary element allows the failed heater and sensing element to be replaced while still online while maintaining full functionality. Various modifications to the sensor and measurement system of the present invention will be readily apparent to those of ordinary skill in the art, and therefore the appended claims are intended to cover all modifications that fall within the spirit and scope of the present invention.

[Brief description of drawings]

1 is an elevational view showing the thermowell housing of the sensor of the present invention; FIG. 2 is a bottom view of the split tubular thermowell housing of FIG. 1, and FIG. 3 is a split tubular thermostat of FIG. Top view of well housing; FIG. 4 is a sensor assembly of the present invention including an electrical connector box and associated structures in a plane through the axis of the split tubular thermowell housing of the present invention shown in FIG. Sectional view of the body; FIG. 5 is a top view showing a partial section in a cut-away plane passing through line 5-5 in FIG. 4; FIG. 6 is a connector box shown in section in FIGS. 7 is a plan view showing a heater and a thermocouple element used in the sensor of the present invention; and FIG. 9 is a monitor using a plurality of split cylindrical sensors of the present invention. FIG. 10 is a block diagram schematically showing the system; FIG. 10 shows the measurement / monitor system of the present invention. Simplified diagram showing a Temu an association with the elements of the split cylindrical sensor part block diagram; 11
A, 11B and 11C are plan views showing the components of the display / operator control panel of the system of the present invention. 10 is a housing, 12A and 12B are sensor probes, 13 is a slot,
14A and 14B are tips, 15A and 15B are chamfered parts, 18 is a collar,
20 is a shank part, 22 is a threaded part, 28 is an annular end surface,
30 is a chamber, 50 is an extension assembly, 51 is a cylindrical sleeve,
60 is a connector box, 62 is a central hole, 63 is a mounting plate, 6
4, 65 are fixing means, 70, 95 are thermocouples, 74 are clips, 86
Is a cover plate, 87 is a hanging side wall, 89 is a matching hole, 90 is a heater element, and 93 and 96 are conducting wires.

Claims (19)

(57) [Claims] 1. A differential temperature sensor including a generally cylindrical shank having a central axis, mounted on and penetrating a pressure vessel sidewall, each having a first and a second end.
A pair of essentially identical probes hanging laterally with respect to the central axis defining an outer circumference having a smaller diameter than the shank, starting from an integral junction of the first end and the shank. The shank extends coaxially through the shank from its free end and a bottom wall defines a generally cylindrical chamber that intersects the central axis near the integral joint,
A center hole for accommodating a heater element extending in the axis parallel relationship with the central axis from the bottom wall and reaching near the second end of the probe in each of the probes, and a symmetrical position with the central hole interposed therebetween. A pair of second holes for accommodating a pair of sensing elements that occupy the differential temperature sensor. 2. The sensor according to claim 1, wherein the sensor has a housing made of a low heat conductive metal material. 3. An essentially identical semi-cylindrical structure in which the pair of probes are symmetrical about a central axis with a slot defined therein defined by opposite sides from the integral joint to the second end of the probe. The sensor according to claim (2), comprising: 4. The sensor according to claim 2, wherein an annular collar is provided coaxially with the central axis at an axial position of the housing close to the integrally joined portion. 5. The collar is provided at an axial position with respect to the shank and the probe so as to surround at least a part of the axial length of the integral joint of the probe and the shank. The sensor according to item 4). 6. A substantially cylindrical shield having a cylindrical side wall, an open end and a closed end, at least the side wall having a plurality of through holes, said shield having an inner diameter substantially the same as the outer diameter of said collar and said probe. The sensor according to claim (4), which has an axial length larger than the axial length, and accommodates and surrounds the probe in a coaxial relationship. 7. A first free cylindrical shank having a concentric annular protrusion having a diameter smaller than the maximum diameter of said shank.
The sensor according to claim (2), which is provided at an end. 8. An exterior of the shank, between the first and second ends of the shank, for mounting the housing to a sidewall of the pressure vessel such that the probe is exposed to the interior of the pressure vessel and accessible from the outside. The sensor according to claim 1, characterized in that it has means provided at a position. 9. An extension assembly comprising a connector box and a generally cylindrical structure having a first end fixed to a central position of the connector box and a second end, and the extension assembly including the sensor. The sensor according to any one of claims (1) to (8), characterized in that the sensor is axially aligned with the housing and is detachably connected to the housing. 10. Forming a concentric annular protrusion of a diameter smaller than the maximum diameter of the shank at the free first end of the substantially cylindrical shank of the housing, and having first and second ends. The inner diameter is equal to the outer diameter of the concentric annular protrusion,
A substantially cylindrical sleeve whose end is detachably fitted to the annular protrusion is provided, and means for axially fixing the extension assembly and the connector box to the sensor housing are provided. Sensor according to claim (9), characterized in. 11. The connector box has a central hole that is smaller than the inside of the sleeve, and a second hole of the sleeve.
A bottom plate aligned and fixed to an end, the extension assembly removably connecting each first end to a cooperating hole in the probe, and a second end defined by an inner surface of the bottom plate of the connector box. A plurality of tubes corresponding to the plurality of holes in the probe and arranged substantially continuously with the plane; and a mounting plate straddling the holes in the bottom plate and engaging in abutting relationship with the second ends of the plurality of tubes. , (9) and () including means for securing the mounting plate to the free end of the shank to secure the extension assembly and connector box to the sensor housing. The sensor according to item 10). 12. A measurement system for monitoring the condition of fluid within a pressure vessel, the elements being integrally connected to each other at a first end, extending in an axially parallel relationship and separated from each other by a slot, the side wall of the pressure vessel. There is a pair of substantially identical first and second probes mounted at appropriate positions therethrough, sealed to the sidewalls and exposed inside the pressure vessel, each probe being A heater element and a pair of temperature sensing elements are built in, and the heater element of the first probe, the selected temperature sensing element and the selected temperature sensing element of the second probe constitute a first differential temperature sensor component, The heater element of the second probe and the selected temperature sensing element and the selected temperature sensing element of the first probe form a second differential temperature sensor component. And a dual differential temperature sensor and power is selectively supplied to the respective heater elements of the first and second probes of the sensor, and the supplied heater elements come into contact with the probe to remove heat into the line. By heating the corresponding probe to raise its temperature in the absence of the sensor, a difference is generated between the temperatures sensed by the temperature sensing elements associated with the heated probe and the unheated probe of the sensor, and A heater control means including a means for generating an invalid heater element output when the validity of each heater element is determined and the output of the heater element is determined to be invalid, and the temperature sensing elements of the first and second probes are selected. And monitoring the sensed temperature output of the selected temperature sensing element to sense the temperature of each of the selected temperature sensing elements of the first and second probes. In the normal monitoring mode of the temperature sensing element control means and the measuring system, which generates a differential temperature output (ΔT) indicating the difference between the outputs and determines the validity of the selected temperature sensing element of the first and second probes. By controlling the heater control means and the temperature sensing element control means to select the heater and sensing element of each sensor corresponding to the first sensor component, a normal differential temperature output state is determined, and the differential of the selected first sensor component is determined. Temperature output (ΔT
If 1) is different from the normal differential temperature condition, the system detects the alarm condition in the normal monitor mode and generates an alarm output in response to the detection of the alarm condition, and responds to the alarm output of the system controller. And an invalid heater element output from the heater control means for the selected heater of the first probe corresponding to the first sensor component and the system control means to form an alarm indication associated with the corresponding sensor. By automatically operating the heater control means in response,
A measuring system characterized in that a heater element of a second probe is selected and is supplied with electric power to switch from a first sensor component to a second sensor component of a given sensor. 13. The system control means verifies this in response to the detection of an alarm condition and commands the heater control means to select a second heater element to switch to a second sensor component. The differential temperature output indication (ΔT2) provided by the temperature sensing element control means for the component is compared to the output indication for the first sensor component and the detected alarm condition is verified as the appropriate condition to generate the alarm indication for the corresponding sensor. Claim (1) characterized in that
The system described in item 2). 14. The system of claim 13, wherein the system control means sequentially online tests each sensor of the plurality of sensors in an automatic test mode. 15. The heater for measuring and storing the differential temperature output (ΔT1) of the first sensor component of a plurality of sensors in a normal operation mode for the system control means to perform an automatic mode online test of each sensor. The control means and the temperature sensing control means are actuated to switch to each second sensor component of the plurality of sensors, and the heater of each second probe of the plurality of sensors for a time sufficient to stabilize and stabilize the temperature of the second sensor component. The elements are selectively powered and the corresponding differential temperature output (ΔT2) is measured and compared to each differential output (ΔT1) of the first sensor component of each sensor to determine the first of the given sensor under test. And each differential temperature output of the second sensor component (ΔT
The sensor failure condition is detected unless 1, and ΔT2) have the same numerical value and opposite sign.
The system according to paragraph. 16. A means for selectively displaying a numerical value and a sign of a sensed temperature difference output (ΔT) of each sensor, a means for displaying a faulty sensor, a means for displaying a faulty heater element, and the selected sensor online. 16. The system of claim 15, characterized by means for initiating a selective test mode instead of an automatic test mode for testing. 17. A plurality of alarm display means respectively associated with the plurality of sensors for pointing to an alarm condition sensed by the corresponding sensor and selectively testing a given sensor in a selective test mode of the system. Thus, the system control means operates the heater control means and the temperature sensing element control means to switch to the second sensor component of a given sensor, thereby forming a first sensor in a normal monitor mode of the system. 15. A selective display of the value and sign of the differential temperature output (ΔT2) of the second sensor component formed in the selective test mode for comparison with the corresponding display of the component output. ) System. 18. The temperature sensing element control means selects the same temperature sensing element conditioned for continuous operation for both the first and second sensor components of each sensor. The system described in section 12). 19. A sensor complement for each of the first and second sensor components of a given sensor when the temperature sensing element control means detects a failure in any of the selected first temperature sensing elements. System according to claim (18), characterized in that the selective temperature sensing element is selected.