JPH06137490A - Sensor unit, monitoring circuit and sensor device containing these unit and circuit - Google Patents

Abstract

PURPOSE: To provide a sensor unit capable of monitoring the operating condition of a condensate trap, using a single sensor element. CONSTITUTION: A sensor unit used to monitor the operating condition of a condensate rap includes an electrical conductor 4 which accommodates an insulating element 17. The insulating element 17 supports an electrically conductive tube 10 to accommodate a temp. sensing device 8 and a terminal element 14. Existence of any condensate liquid is decided by measuring the electrical continuity condition between the tube 10 and the conductor 4, while the temperature is decided by the temperature sensing device 8. Furthermore, a circuit is provided which is fed with signals from the terminal element 14 and monitors simply the electrical continuity condition between the temperature sensing device 8, tube 10, and conductor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor unit, a monitoring circuit and a sensor device including them, and more particularly to a sensor unit used to monitor the operating state of a condensate trap.

[0002]

BACKGROUND OF THE INVENTION Condensate traps are commonly used in steam mechanics and, in these circumstances, are commonly referred to as steam traps. Its function is to discharge condensed water from the steam mechanism without letting the steam escape. The loss of steam from this mechanism means a loss of energy. Therefore, steam traps are typically equipped with a valve that reacts with condensed water or steam in the vicinity, which valve opens when condensed water is present and closes when steam is present.

Occasionally, however, the steam trap may not close, or may only partially close, in which case a steam leak will continue after the time when the valve should close. It is not always easy to detect such a condition, and various monitoring devices have been devised which issue an alarm signal when the steam trap malfunctions.

One of such monitoring devices is provided with a sensor chamber, which is partially filled with water, and the sensor chamber faces downward from its top to a position lower than the normal water level. A partition wall protruding inward defines the inlet and the outlet. Therefore, the inlet and the outlet are in communication with each other below the water surface. Also, on the water surface, a small hole connects the inlet and outlet.

The vapor flow between the inlet and the outlet passes through the holes if the amount is small. However, as the amount of steam flow increases, the corresponding pressure differential pushes down the water surface in the inlet. When the water level drops significantly, it is detected by the water level sensor and the malfunction of the steam trap is displayed.

An example of a device that operates in this way is disclosed in British Patent Application No. 2231407A.

Further problems can arise when a valve is flooded. In this state, the valve does not open, airlock occurs, or the operation of the valve is disturbed, and condensed water accumulates to an unacceptable height. When the steam trap is flooded, condensed water accumulates in the sensor chamber and the water level sensor sinks in the condensed water, and the sensor emits an output indicating that the steam trap is operating normally. However, since the temperature of the condensed water decreases, it has been previously proposed that such infiltration can be detected by monitoring the temperature of the condensed water and its water level.

[0008]

However, in the conventional device, two separate sensors are required to detect the water level and the temperature, and the structure of the device is complicated and large, and the cost is high. is there.

[0009]

According to a first aspect of the present invention, there is provided a sensor unit having a conductor defining a recess for accommodating an insulating element, the insulating element protruding from one side thereof. Supporting a conductive tube, the conductive tube housing a temperature sensing means, the unit further for receiving a signal indicative of the temperature of the temperature sensing means and the electrical continuity between the conductive tube and the conductor. A sensor unit is proposed, which comprises a terminal element fixed to a conductor and electrically connected to a conductor tube and a temperature sensing means.

The presence or absence of liquid at the sensor position can be detected by monitoring the electrical continuity between the conductive tube and the conductor. Therefore, these two elements constitute the liquid level sensing means.

In the above structure, four terminal elements are provided, two of which are electrically connected to the temperature sensing means,
The other two may be electrically connected to the main body and the conductive tube, respectively. This also allows a single sensor to monitor the temperature of the condensate.

In a further preferred embodiment of the present invention, two terminal elements are provided, each electrically connected to the conductive tube and one terminal of the temperature sensing means. In this embodiment, the other terminal of the temperature sensing means is electrically connected to the conductor, and the conductor itself acts as an electrical connector. Thus, the conductor constitutes a common connector for the temperature sensing means and the liquid level sensing means.

In another embodiment of the invention, the terminal element of the sensor is embedded within the insulating element such that the insulating element supports both the conducting tube and the terminal element.

According to yet another embodiment of the present invention, the sensor body includes a threaded portion for screwing the unit into the fluid chamber to sense the condition of the fluid in the fluid chamber.

In another embodiment, in order to monitor the sensor, a resistance indicating the temperature of the temperature sensing means and a monitoring circuit for alternately monitoring the conduction state between the conductive tube and the conductor are provided in combination with the sensor. .

Known steam schemes use a water level sensor which indicates the operating status of the associated steam trap. Such a mechanism may have a central control station coupled to individual sensors by a large two wire network. In this case, the state of each steam trap can be simultaneously diagnosed from the central control station.

However, the sensor unit according to the present invention has two
It has one sensing means and reduces the number of sensors. Thus, this configuration is typically associated with a four wire network, or three wire network if one terminal is shared. Then, when monitoring them centrally, there arises a problem that a new network must be provided to the existing steam mechanism in order to enable the installation of the sensor unit.

However, by using a suitable interface circuit, a monitoring device between the two terminals can be used.
The operation of the two sensing means can be monitored. Such an interface is achieved by controlling the flow of current through the temperature sensing means and the liquid level sensing means in sequence by two diodes arranged in opposite directions, these two diodes depending on the signal at the input. The response state from one or the other of both sensing means is presented.

Therefore, when installing the sensor unit of the present invention, it is not necessary to modify the steam system which already has a large two-wire electrical network.

From the above, according to the second feature of the present invention,
A monitoring circuit for monitoring the values of two variable resistors, the circuit comprising a monitoring device having two terminals and means for reversing the electrical polarity of those terminals, the variable resistor being connected to said terminals. Connected to two branch lines of the circuit connected in parallel, each branch line having a diode connected in series with a corresponding resistor, the diode having a voltage of one polarity applied to the terminal. When one of the resistors has a current flowing through it, and when a voltage of the opposite polarity is applied to the terminal, the other resistor has a current flowing therethrough.
A monitoring circuit is proposed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The steam trap sensor unit of FIGS. 1 and 2 is mounted upstream of a steam trap (not shown) which, in use, discharges condensed condensate. The sensor unit includes an outer casing, and a sensor chamber that defines a fluid flow path is defined therein. This fluid channel is divided into an inlet portion 1 and an outlet portion 2 by a partition wall 5. The partition wall 5 extends downward from the top of the sensor chamber. The upper region of the partition 5 is provided with holes 7 which equalize the pressure on both sides of it and allow a limited amount of vapor to pass under normal leakage levels from the valve. A sensor 3 protruding into the inlet portion 1 is attached to the casing. The sensor 3 is sensitive to ambient temperature and the presence or absence of condensate.

As shown in FIG. 3, the sensor 3 is provided with a cylindrical elongated metal housing 4 as a conductor, and one end thereof is provided with a screw thread to be screwed into a screw hole of an outer casing of the sensor chamber. The diameter of the threaded portion is typically about 16 mm. The sensor 3 comprises a sensor element in the form of a tube 10 as an elongated metal conducting tube housing a temperature sensing device 8. With the sensor 3 in place, the tube 10 will project into the inlet section 1 of the fluid flow path. The elongated tube 10 and the housing 4 are both electrically conductive, but are separated from each other by an insulator 17 as an insulating element housed in the metal housing 4. Insulator 1
7 has the form of a substantially cylindrical block,
It is firmly held in. The tube 10 projects coaxially with the insulator 17. Part of the tube 10 projects from one peripheral edge of the insulator 17, and the other part of the tube 10 is firmly housed in the insulator 17. The relative position of the tube 10 and the housing 4 is set so that the resistance between them can be monitored with the same sensing circuit used in known water level sensors. By housing the temperature sensing device 8 in the tube 10,
The overall dimensions and thermal mass are approximately the same as those of known water level sensors. Therefore, the sensor 3 can be used without replacing or modifying the casing of the sensor unit shown in FIGS.
It can be used by directly replacing the known sensor. The tube 10 is typically about 3 mm in diameter and projects about 10 mm from the one peripheral edge of the insulator 17. In the embodiment shown in FIG. 3, the sensor has four terminal pins 1 as terminal elements.
4 further, these terminal pins 14 project into a socket 16 as a recess exposed outside the sensor chamber.
The terminal pin 14 is fixed to the sensor body and is embedded in the insulator 17 so as to protrude from the other peripheral edge of the insulator 17 into the socket 16. 2 out of 4 terminal pins
One is electrically connected to the tube 10 and the housing 4, respectively, and the other two terminal pins are connected to two terminals of the temperature sensing device 8.

However, if one terminal is shared by the temperature sensing device 8 and the tube 10 or the housing 4, the sensor may be provided with only three terminal pins. Furthermore, if the metal housing 4 is used as a terminal in addition to this structure, the sensor may be provided with only two terminal pins. An example of this sensor is shown in FIG. 4, with one terminal pin connected to the metal tube 10 and the other terminal pin connected to one of the terminals of the temperature sensing device 8. The other terminal of the temperature sensing device 8 is electrically connected to the housing 4, which itself acts as a connector terminal.

The sensor is electrically connectable to the remote mains power unit shown in FIG. The remote units have associated devices, each corresponding to the operation of a steam trap. An input unit 18 that can be electrically connected to the plurality of sensors 3 is provided.
The mechanism is thus capable of monitoring a plurality of sensors to detect a flooded or leaked steam condition resulting from the malfunction of one of the steam traps. The remote unit comprises means 19 for indicating which trap is being monitored. In addition, a plurality of indicators 21 are provided to show the results of water immersion or steam leak tests. The indicators 21 may be in the form of green and red diodes, respectively, to indicate whether the response to each test performed is satisfactory or unsatisfactory.

In the existing vapor trap monitoring mechanism, the output of the water level sensor is sent to the sensor unit of FIG. 2 via a network consisting of two lines. Figure 3 shows the water level sensor
In order to utilize the conventional wiring after replacing the sensor according to the present invention, the four terminal pins of each sensor are connected to two wires of the conventional wiring by the circuit shown in FIG.

This circuit comprises a temperature sensing device 8 indicated by a variable resistance RT and a water level sensor indicated by a variable resistance RC (ie variable conductivity). The variable resistance RC is the resistance between the tube 10 and the housing 4. Two diodes D1 and D2 for passing currents in opposite directions to the variable resistors are provided in opposite directions on branch lines connected in parallel with each other. Both resistors RT and RC and diodes D1 and D2 form a monitoring circuit. At the input 22 of the circuit, the voltage Vin is applied in the positive or negative direction by the main control unit. By applying a DC voltage in one direction, a current flowing through the circuit from the + terminal to the − terminal of the input section 22 is generated. Therefore, one diode conducts and the current passes through one of the two variable resistors. This resistance can be measured, for example, by amperometry. If the voltage applied at the input of the circuit is reversed, the current will flow in the opposite direction and the other diode will conduct. In this case, the current flows through the other variable resistor in the opposite direction. Therefore, in that case,
This second resistance can also be measured by amperometry.

When the circuit of FIG. 7 is used for a sensor having four terminal pins, the connection positions of the terminal pins in the electric circuit are the connectors 26 to 29.

The connectors 26 and 27 are the temperature sensing device 8
Two terminals connected to (RT) are shown. Connector 28
Reference numerals 29 and 29 denote terminals connected to the tube 10 and the metal housing 4.

However, if this circuit is used for a sensor having only two terminal pins, the connector 30 is a common connector for both sensing means of a terminal in the form of a metal housing 4 and the connectors 26 and 28 are two. Shows two terminal pins.

In using the sensor monitoring mechanism according to the present invention, two resistors RC and RT are sequentially measured by sequentially applying a voltage to the input 22 of the circuit in both directions. The polarity switching is automatically performed by the monitoring unit shown in FIG. As a result, it is possible to diagnose the flooded state of the steam trap in the steam mechanism or the state of steam leakage from the trap.

FIG. 6 shows a portable unit for periodically monitoring the sensor of FIG. In this arrangement, the portable unit has a four wire lead 20 with suitable plugs 23 for connecting to the four terminal pins 14 of the sensor 3. Alternatively, the portable unit may have two wire leads with a socket and be connected to the circuit of FIG. 7 connected to the four terminal pins 14 of the sensor 3.

The portable unit is equipped with two switches 24 which perform a flood test and a steam leak test, respectively. Further, a light emitting diode 25 for displaying the test result is also provided. Similar to the remote unit of FIG. 5, these light emitting diodes are also green and red, indicating a normal state and a faulty vapor trap, respectively.
A portable unit may be used to monitor each vapor trap of the mechanism individually.

When installing the steam trap sensor unit shown in FIGS. 1 and 2, it is installed in the lower part of the pipe line of the steam mechanism, and the flow of the pipe line at the inlet 1 and the outlet 2 of the sensor chamber is installed. Define the path. Condensed water generated in the steam mechanism is discharged through the sensor chamber. In the normal operating state of this trap, the level of condensed water in the sensor chamber is higher than that of the sensor. If there is condensed water in the vicinity of the vapor trap, it will open the trap and drain some of the condensed water. Once the condensate is drained, the steam trap closes to prevent steam loss. When the steam trap closes and operates normally,
The tube 10 is submerged in the condensed water and vapor is present slightly higher in the sensor chamber. Therefore, the temperature of water in the sensor chamber becomes close to the temperature of steam. This temperature is detected by the temperature sensing device 8. Further, the condensed water creates a conductive path between the tube 10 and the housing 4. This state is therefore detected by the water level detecting means. The amount of leakage is small and tolerable, and by providing the small hole 7 in the partition wall, such a small amount of leakage does not significantly affect the water level of the condensed water in the sensor chamber.

However, in the case of a severe leak, the relatively large pressure drop occurring before and after the partition wall 5 causes the vapor to flow through the sensor chamber at a faster rate than it can pass through the hole 7. Due to this pressure drop, the water level of the condensed water in the area of the sensor 3 drops below the pipe 10, and the vapor becomes foamy below the partition wall 5. This state is indicated by an increase in resistance RC. Since the temperature sensing device 8 is in steam, it senses the relatively high temperature in this condition.

In the flooded state, the valve is not open or an air lock has occurred. In this case, too much condensed water will collect in the sensor chamber, which will cool over time. This temperature change can be detected by the temperature sensing device 8.
In this way, the flooded state can be detected even if the water level sensing means outputs a normal output due to the flooding of the pipe 10.

[0036]

As described above, according to the present invention, the sensor unit has the conductor that defines the recess for accommodating the insulating element, and the insulating element supports the conductive tube protruding from one surface thereof.
The conductive tube accommodates the temperature sensing means, and the terminal element is fixed to the conductive body and electrically connected to the conductive tube, and the temperature sensed by the temperature sensing means and the electrical conductivity between the conductive tube and the conductive body are detected. A signal is received to indicate the electrical continuity. It is possible to detect a liquid level above a certain level by the conduction between the conductive tube and the conductor, and therefore, it is possible to detect both the temperature and the liquid level with a single sensor. The operating condition of the body trap can be accurately monitored.

[Brief description of drawings]

FIG. 1 is a perspective view of a steam trap sensor unit.

2 is a schematic cross-sectional view of the sensor unit of FIG.

FIG. 3 is a sectional view of a sensor of the sensor unit shown in FIG.

4 is a cross-sectional view of another embodiment of the sensor of the sensor unit of FIG.

FIG. 5 is a schematic diagram of a remote mains power unit that reads a signal from a sensor.

FIG. 6 is a schematic diagram of a portable unit that reads a signal from a sensor.

FIG. 7 is an electric circuit diagram for extracting the output of the sensor of FIG.

[Explanation of symbols]

 1 inlet part 2 outlet part 3 sensor 4 housing (conductor) 5 partition wall 7 hole 8 temperature sensing device 10 conductive tube 14 terminal pin 16 recess 26-29 connector D1, D2 diode RT, RC resistance

 ─────────────────────────────────────────────────── ————————————————————————————————————————————————————————————————————————————————— Inventor Antony Graham Ricketts GL 52 6 T.Y. Gloucestershire, Cheltenham, Eldon Road, Beecharst Avenue 41

Claims (8)

[Claims] 1. A sensor unit comprising a conductor defining a recess for accommodating an insulating element, the insulating element supporting a conductive tube protruding from one surface thereof, the conductive tube accommodating temperature sensing means. However, the unit is further fixed to the conductor to receive the signal indicating the temperature of the temperature sensing means and the electrical continuity between the conductor and the conductor. A sensor unit comprising terminal elements electrically connected. 2. The terminal element has four, two of which are electrically connected to the temperature sensing means, and the other two are electrically connected to the conductor and the conductive tube, respectively. 1. The sensor unit according to 1. 3. The terminal element is two, the terminal element is electrically connected to the conductive tube and one terminal of the temperature sensing means, respectively, the other terminal of the temperature sensing means is the conductor. The sensor unit according to claim 1, which is electrically connected to the sensor unit. 4. The conductor according to claim 1, further comprising a screw portion for screwing the sensor unit to the fluid chamber in order to sense the state of the fluid in the fluid chamber. Sensor unit. 5. The sensor unit according to claim 1, wherein each of the terminal elements is embedded in the insulating element. 6. The sensor unit according to claim 1, a resistance indicating the temperature of the temperature sensing means, and an electrical conduction state between the conductive tube and the conductor are alternately monitored. Combination with the monitoring circuit. 7. A monitoring circuit for monitoring the values of two variable resistors, said circuit comprising a monitoring device having two terminals and means for reversing the electrical polarity of those terminals, The variable resistor is connected to two branch lines of the circuit connected in parallel to the terminals, each branch line having a diode connected in series with a corresponding resistor, the diode being a voltage of one polarity. Is connected to the resistor so that a current flows through one of the resistors when the voltage is applied to the terminal, and a current flows through the other resistor when a voltage of the opposite polarity is applied to the terminal. 8. The monitoring circuit according to claim 7, wherein the sensor unit according to any one of claims 1 to 6, the variable resistance includes a temperature sensing means, and a resistance between a conductor and a conductive tube. Sensor device.