Safeguard arrangement for plant

Abstract: A plant comprises a plant auxiliary (11,12) provided with a lid (102) which is opened for maintenance, and actuation means (13-16) for switching the plant between "operational" and "maintenance" states. For example there may be switching means (13-16) installed on a piping connected to said plant auxiliary (11), and driving means (221) to give a driving output to the switching means in response to an opening or closing instruction signal for said switching means, and which is employed when operations for maintenance of the aforesaid plant auxiliary are executed. To safeguard maintenance personnel, there are lid opening detecting means (2) to detect the opening of the lid of the aforesaid plant auxiliary or the release of locking means thereof, and checking means to ensure that the actuation means is in the "maintenance" state when it is detected by said lid opening detecting means that the lid is opened or to be opened.

Description: The present invention relates to an industrial plant having a safeguard arrangement, particularly a safeguard arrangement for securing the safety of maintenance personnel when they are within the plant when a test or maintenance is carried out. In a plant such as a thermal power plant, the inspection and maintenance of plant auxiliaries are conducted properly for maintaining sound operations of the plant, and it is indispensable to secure the safety of the maintenance personnel in terms of both mind and body thereof. A sudden motion of some peripheral apparatus in the course of the maintenance, for instance, frightens the personnel, and also exposes them to serious danger, possibly causing casualty, e.g. when they work at a height. Such matters as stated above must be avoided without fail. On the occasion of maintenance of plant auxiliaries, therefore, warning tags for prohibiting operations are usually put on the operation switches of said auxiliaries and the peripheral apparatuses so as to prevent the erroneous operation of said switches by any operator other than the maintenance personnel concerned. Besides, a process control system is known wherein the delivery of a control instruction from a process control unit to a process apparatus is prohibited by operating a switch for maintenance and inspection provided in a process input/output device on the occasion of the maintenance and inspection of the process control system, as described in Japanese Patent Laid-Open No. 91507/1984. Among the plant auxiliaries, there are units, such as a condenser waterbox, a feed water heater, a coal pulverizer, a fan, a motor and a pump, which have a so-called lid, such as a manhole, a hatch or a cover, which is opened for internal on-the-spot maintenance. In many cases, moreover, a plurality of these auxiliaries are installed in juxtaposition to obtain a prescribed output, and therefore it sometimes happens that a part of the auxiliaries is stopped and subjected to the maintenance while a partial loaded operation is executed. On the occasion of the maintenance of the stopped auxiliary, apparatuses on the entrance and exit sides thereof are closed, a rotary machine is stopped, the inflow of a fluid is checked, and the fluid located inside is discharged, before the maintenance is executed. However, if an apparatus on the entrance or exit side is opened or the rotary machine is driven erroneously on the occasion, serious injury may be inflicted on the personnel working inside. In terms of the safeguard regarding such auxiliaries as mentioned above, the method relying on the manual operation of the warning tag for prohibiting operation and the switch for maintenance and inspection according to the above-described prior art cannot eliminate the possibility of forgetting to set the warning tag, to operate the switch for maintenance and inspection, or the like, and it can also be imagined that an operation switch is operated erroneously by a person not knowing that a given auxiliary is under maintenance. These failures cause the problem that the maintenance personnel are imperilled by the operation of the auxiliary under maintenance or a related apparatus. As is seen from the above description it is desirable to enable one to prevent the personnel engaged in the maintenance of a plant apparatus from being imperilled by unexpected motion of the plant apparatus due to an erroneous operation. Ullmanns Encyklopädie der technischen Chemie, 4th edition, Band 6: "Umweltschutz und Arbeitssicherkeit", 1981, Verlag Chemie, Weinheim, p. 754-758 discloses a plant or part thereof having a plant portion delimited by a wall, a cover openable in said wall to permit a person to enter the plant portion to carry out maintenance work thereof; and piping coupled to the plant portion for carrying a flow to the plant portion. The present invention concerns such a plant or part which is characterised in that there are valve means on the piping; actuator means for opening or closing the valve means to permit or prevent flow along the pipeline; cover opening detecting means for detecting the opening of the cover or the release of locking means of the cover, said cover opening detecting means producing a cover opening signal in response to such detection; and controller means which are coupled to the actuator means for controlling operation thereof; said controller means being coupled to the cover opening detecting means to receive the cover opening signal from it and being arranged so that, when such a signal is received, (i) operation of the actuator means to open the valve means is prevented; and/or (ii) a closure signal is sent to the actuator means to cause it to effect closure of the valve means if it is open. In Chemische Technologie, 4th edition, Vol. 1: "Allgemeines", 1984, Carl Hanser Verlag, München, p. 684, 685, 718, safety switches as described above are mentioned. There is also disclosure that when fluids are transported to a container during operation, the flow has to be interrupted. This is achieved through the removal of pipes or the insertion of discs in the pipe. Brief Description of the Drawings Figure 1 shows a fundamental construction of the present invention; Figure 2 and 3 show an example of installation of a maintenance state detector for a manhole; Figure 4 is a system diagram related to a condenser; Figure 5 shows an example of application of a safeguard arrangement to a condenser waterbox; Figure 6 is a system diagram related to a feed water heater; Figure 7 shows an example of application of the safeguard arrangement to the feed water heater; Figure 8 is a system diagram related to a coal pulverizer; Figure 9 shows an example of application of the safeguard arrangement to the coal pulverizer; Figure 10 is a system diagram related to a forced draft fan; Figure 11 shows an example of application of the safeguard arrangement to the forced draft fan; and Figure 12 shows another embodiment of the present invention. An embodiment of the present invention will be described hereunder, taking a thermal power plant as an example and using Figures 1 to 13. Figure 1 shows a fundamental construction of a safeguard arrangement 1. In this arrangement, a lid opening detector 2 detecting that a lid, such as a cover, a hatch or a manhole, is opened is provided, an opening detection signal 3 from said detector 2 is inverted by an NOT circuit 4, an operation permission signal 5 thus obtained and a starting (opening) operation signal 7 from an operation switch 6 are given to an AND circuit 8, and an auxiliary 10 is started by an output signal 9 only when the aforesaid operation permission signal 5 and the aforesaid starting (opening) operation signal 7 are effectuated simultaneously. Interlocking of the lid opening detection signal 3 is not necessary for a stop (closure) side signal of the operation switch 6. Figures 2 and 3 show an example of installation of a cover opening detector in a manhole. In this figure, numeral 100 denotes a part of the wall of a plant auxiliary 10. A cover 101 being opened (Fig. 3), maintenance personnel go in and out through a manhole 101. The cover 102 is fitted rotably to the wall 100, and a lever 103 of the cover opening detector 2, e.g. a microswitch, fixed on the wall 100 and a part of the cover 102 engage with each other so as to detect the opening of the cover 102. Fig. 2 shows the state wherein the manhole cover 102 is closed. In this case, the lever 103 of the cover opening detector 2 is pressed by the manhole cover 102, and the detector 2 does not deliver an output. Fig. 3 shows the state wherein the manhole cover 1-2 is opened, and the lever 103 of the cover opening detector 2 is released in this case. Judging from the state that the lever 103 is release, the cover opening detector 2 determines the plant auxiliary 10 to be in the state of maintenance and delivers an output. While the opening is detected from the engagement of the rotating manhole cover with the microswitch in this example, adequate detecting means other than the above can also be adopted. In addition, while the opening of the cover is detected in this case, it is also effective to determine the opening from the disengagement of an opening locking mechanism fitted to the cover and to deliver an output on the basis of the determination. The following is a description on a concrete embodiment of the present invention. Figure 4 shows an example wherein condenser waterboxes 11 and 12 of a thermoelectric power plant are cited as plant auxiliaries. The degree of vacuum of a condenser under a rated load is maintained at a prescribed value by using the two waterboxes 11 and 12, and in this state, valves 13, 14, 221 and 222 are opened, while valves 15 and 16 are closed. Moreover, cooling water such as seawater is made to flow in the directions of arrows shown in the figure, and thereby turbine exhaust not shown in the figure is cooled down to be condensed. While the maintenance of these waterboxes is conducted also with the plant stopped for a long term as is the case with periodical inspection, a higher degree of danger is brought about when one of them is subjected to maintenance while the other is operated, with a plant output halved. These conditions increase the possibility of erroneous operation of valves and the like related to the stopped waterbox. In order to subject the waterbox A 11 to maintenance while leaving the waterbox B 12 operated in this figure, for instance, all of a waterbox A inlet valve 13, a waterbox A outlet valve 14, a waterbox bypass valve 15 and a waterbox bypass valve 16 are put beforehand in a full-closed state so as to isolate the waterbox A 11 from the cooling water flowing through the waterbox B 12 and from that flowing on the upstream side of the waterbox A inlet valve 13 and on the downstream side of the A outlet valve 14, and the cooling water in the waterbox A 11 is discharged. When the waterbox A 11 is subjected to maintenance, any of a waterbox A entrance cover 17, a waterbox A entrance manhole 18, a waterbox exit cover 19 and a waterbox A exit manhole 20 is opened, and maintenance personnel enter a maintenance area therethrough. In this figure, numeral 222 denotes an inlet valve on the waterbox B side, 221 an outlet valve, 224 and 226 waterbox manholes, and 223 and 225 waterbox covers, and cover opening detectors are fitted to all of the manholes and covers respectively. Figure 5 shows an example of application of a safeguard arrangement in the maintenance of the condenser waterbox A 11 shown in Fig. 4. Cover opening detectors 21, 22, 23 and 24 are provided for a waterbox A entrance cover 17, a waterbox A entrance manhole 18, a waterbox A exit cover 19 and a waterbox A exit manhole 20 respectively, and a waterbox A maintenance signal 26 is effectuated by an OR circuit 25 when any one of said detectors 21, 22, 23 and 24 detects the state of maintenance. Besides, a push button 27 for signaling the waterbox A being under maintenance, or the like, which is operated by maintenance personnel on the spot at the start of the maintenance may also be provided in addition to the aforesaid detectors. In the case when the waterbox A maintenance signal 26 is effectuated, a waterbox A operation permission signal 29, which is obtained by inverting said maintenance signal 26 by an NOT circuit 28, is not effectuated. Therefore, opening operation instruction signals 34, 35, 36 and 37 for a waterbox A inlet valve 13, a waterbox A outlet valve 14, a waterbox bypass valve 15 and a waterbox bypass valve 16 are not effectuated even if any of operation switches 30, 31, 32 and 33 corresponding to said valves 13, 14, 15 and 16 respectively is operated for opening, and consequently none of the aforesaid valves 13, 14, 15 and 16 performs an opening operation. An identical opening operation prohibiting circuit may also be provided for an automatic opening operation circuit, such as a sequencer, as well as for the aforesaid operation switches 30, 31, 32 and 33. In this case, the switches 30 to 33 may be regarded as the automatic opening operation circuit such as the sequencer. Moreover, the state that the waterbox A 11 is under maintenance currently may be shown by an indication lamp provided on each of the operation switches 30, 31, 32 and 33, or on a display screen of a computer, in response to the waterbox A maintenance signal 26, so as to inform an operator that the part concerned is under maintenance. In the same way as in the case of the above-stated waterbox A 11, a safeguard arrangement for maintenance of the waterbox B 12 is constructed as follows. A waterbox B entrance cover 225, a waterbox B entrance manhole 226, a waterbox B exit cover 223 and a waterbox B exit manhole 224 of Fig. 4 are provided with cover opening detectors 227 to 230 (Fig. 5) respectively, and when any one of said detectors 227 to 230 detects the state of maintenance, a waterbox B maintenance signal 233 is effectuated by an OR circuit 232. Besides, a push button 231 for signalling the waterbox B being under maintenance, which is operated by maintenance personnel on the spot at the start of the maintenance, is also provided in addition to the aforesaid detectors 227 to 230. When the waterbox B maintenance signal 233 is effectuated, a waterbox B operation permission signal 235, which is obtained by inverting the aforesaid maintenance signal 233 by a NOT circuit 234, is not effectuated. Therefore opening operation instruction signals 238, 239, 36 and 37 for a waterbox B inlet valve 222, a waterbox B outlet valve 221, the waterbox bypass valve 15 and the waterbox bypass valve 16 are not effectuated even if any of operation switches 236, 237, 32 and 33 corresponding to said-valves 222, 221, 15 and 16 respectively is operated for opening, and consequently none of the aforesaid valves 222, 221 15 and 16 performs an opening operation. According to the present embodiment, the opening operation of all the valves 13, 14, 15 and 16 connected to the waterbox A 11 can be prohibited during the maintenance of the waterbox B 12. Even if any of the operation switches 30, 31, 32 and 33 is operated for opening erroneously by an operator or if the central sequencer (computer) outputs an opening signal for any reason, the inflow of cooling water into the waterbox A 11 can be prevented. Thus the risk of maintenance personnel being immersed in water and possibly drowned is prevented. During the maintenance of the waterbox B, likewise, the opening operation of all the valves 222, 221, 15 and 16 connected to the waterbox B 12 can be prohibited, and therefore the inflow of the cooling water into the waterbox B 12 can be prevented, even if any of the operation switches 236, 237, 32 and 33 is operated for opening erroneously by the operator. The characteristic feature of this embodiment is that the valves 15 and 16 bypassing the two waterboxes are locked during maintenance of either of the waterboxes since they are common to the two. Figure 6 shows a system of feed water heaters 111 and 112 which are plant auxiliaries. Feed water from a condenser can be supplied to a boiler through three routes, the two feed water heaters 111 and 112 installed in juxtaposition and a bypass valve 240 opened during the operation of the heaters. These feed water heaters receive extracted steam from a turbine through an extraction stop valve 115 and heat the feed water. Numeral 113 denotes a feed water inlet valve and 114 a feed water outlet valve. In this case, a system A consisting of 111, 114a, 115a and 113a and a system B consisting of 112, 114b, 115b and 113b are independent of each other, and there is no apparatus that must be locked when either of the systems is subjected to maintenance, as is the case with the example of Fig. 4. Therefore, a description will be made hereunder only of the system A. In order to subject the feed water heater A 111 to maintenance while leaving the feed water heater 112 in the state of operation, in the present feed water system, the inlet valve 113a, the outlet valve 114a and the extraction stop valve 115a of heater A are put in a full-closed state, while other valves are put in an opened state, and thereby the feed water heater 111 is isolated from the feed water and extracted steam flowing in and out of the feed water heater 3 112. When the feed water heater A 111 is put under maintenance, a feed water heater A manhole 116a is opened, and maintenance personnel enter the maintenance area therethrough. Figure 7 shows an example of application of the safeguard arrangement in the maintenance of the feed water heaters shown in Fig. 6, and a description will be made only of the maintenance of the system A. The feed water heater A manhole 116a is provided with a cover opening detector 117a, and a feed water heater A maintenance signal 120a is effectuated by an OR circuit ll9a when the state of maintenance is detected by said detector 117a or when a push button 118a for signalling the feed water heater A being under maintenance is operated on the spot by maintenance personnel. Said push button 118a may not be provided. In the case when the feed water heater A maintenance signal 120a is effectuated, a feed water heater A operation permission signal 122a, which is obtained by inverting said maintenance signal 120a by a NOT circuit 121a, is not effectuated. Therefore opening operation instruction signals 126a, 127a and 128a for the feed water inlet valve 113a, the feed water outlet valve 114a and the extraction stop valve 115a are not effectuated even if any of operation switches 123a, 124a and 125a corresponding to said valves 113a, 114a and 115a respectively is operated for opening, and consequently none of the aforesaid valves performs an opening operation. Besides, interlocking of a cover opening detection signal for an operation signal for closure of the operation switches 123a, 124a and 125a is unnecessary. According to the present embodiment, the opening operation of all the valves connecting to the feed water heater A 111 can be prohibited during the maintenance of the feed water heater A. Even if any of the operation switches 123a, 124a and 125a is operated for opening erroneously by an operator, the inflow of feed water or extracted steam into the feed water heater A 111 can be prevented. Thus the risk of maintenance personnel being burnt, scalded or drowned by the feed water or extracted steam of high temperature and high pressure is prevented. Figure 8 shows an example of a coal pulverizer as a plant auxiliary. Herein the coal pulverizer 38 is an apparatus for supplying pulverized coal as a fuel to a boiler 241. One boiler 241 is provided with a plurality of coal pulverizers 38, and the coal supplied from a coal feeder 41 is crushed by a rotor into pulverized coal, and then the pulverized coal is supplied to the boiler by carrier air 242. The figure shows an example of a coal pulverizer having two systems a and b . In order to subject the inside of a coal pulverizer 38a of the system a to maintenance while leaving a coal pulverizer 38b of the system b in the state of operation, in the coal pulverizer 38 stated above, a coal gate 40a checking the flow of coal from a coal bunker 39a into a coal feeder 41a is closed, a coal feeder motor 42a for casting coal from the coal feeder 41a into the coal pulverizer 38a is stopped, a coal pulverizer motor 43a for pulverizing the coal cast in from the coal feeder 41a is stopped, a primary air damper 44a checking the inflow of hot primary air 242, the carrier air, into the coal feeder 41a is closed, and a coal pulverizer outlet damper 45a checking the backflow of a flame in a furnace and that of pulverized coal from another coal pulverizer is closed so that the coal pulverizer 38a is isolated from the coal, primary air, flame and pulverized coal flowing thereinto, and a rotor 46a in the coal pulverizer 38a is stopped. When the inside of the coal pulverizer 38a is subjected to maintenance, any of the plurality of coal pulverizer hatches 47a is opened, and maintenance personnel enter the maintenance area therethrough. Figure 9 shows the safeguard arrangement for the coal pulverizer 38 shown in Fig. 8. Since both systems a and b are based on the same logic, a description will be made hereunder only on the example of the system a . Each of the coal pulverizer hatches 47a is provided with a hatch opening detector 48a, and a coal pulverizer maintenance signal 51a is effectuated by an OR circuit 49a when the opened state of the hatches is detected by any one of said detectors 48a or when a push button 50a for signalling the coal pulverizer being under maintenance is operated on the spot by maintenance personnel. Said push button 50a may not be provided. When the coal pulverizer maintenance signal 51a is effectuated, a coal pulverizer operation permission signal 53, which is obtained by inverting said maintenance signal 5la by an NOT circuit 52a, is not effectuated. Therefore opening operation instruction signals 59a, 62a and 63a for the coal gat-40a, the primary air damper 44a and the coal pulverizer outlet damper 45a are not effectuated even if any of operation switches 54a, 57a and 58a corresponding to said apparatuses respectively is operated for opening, and consequently none of the aforesaid apparatuses performs an opening operation. Even if either of operation switches 55a and 56a corresponding to the coal feeder motor 42a and the coal pulverizer motor 43a respectively is operatec for starting, start instruction signals 60a and 61a for said motors are not effectuated, and consequently neither of these motors is started. According to the present embodiment, the opening and starting operations of all of the auxiliaries 40a, 42a, 43a, 44a and 45a related to the coal pulverizer 38a can be prohibited during the maintenance of the coal pulverizer. Thus such accidents as maintenance personnel being buried in the coal flowing into the coal pulverizer 38a, as the personnel being burnt or scalded by the hot air, flame or pulverized coal flowing into the coal pulverizer 38a and as the personnel being caught in and, in the worst case, killed by the rotation of the rotor 46a, owing to the erroneous operations of either of the operation switches 54a and 55a, either of the operation switches 57a and 28a, and the operation switch 56a, by an operator, respectively, are prevented. Figure 10 is a system diagram of forced draft fans and auxiliaries related thereto for supplying air to a boiler, which are taken as one example of the plant auxiliaries. In order to subject the inside of a forced draft fan 131a of a system A while leaving a forced draft fan of a system B in the state of operation, in a forced draft fan system composed of a plurality thereof, a forced draft fan motor 132a is stopped, and a forced draft fan outlet damper 133a checking the backflow of air from the other forced draft fan is closed. On the occasion, a forced draft fan vane 134a is opened in the lowest degree. When the inside of forced draft fan 131a is subjected to maintenance, a forced draft fan manhole 135a is opened, and maintenance personnel enter the maintenance area therethrough. Figure 11 shows an example of application of a safeguard arrangement in the maintenance of the inside of the forced draft fan 131a shown in Fig. 10. The forced draft fan manhole 135a is provided with a cover opening detector 136a, and a forced draft fan maintenance signal 139a is effectuated by an OR circuit 138a when the opened state is detected by said detector 136a or when a push button 139a for signaling the forced draft fan being under maintenance is operated on the spot by the maintenance personnel. Said push button 137a may not be provided. When the forced draft fan maintenance signal 139a is effectuated, a forced draft fan operation permission signal 141a, which is obtained by inverting said maintenance signal 139a by an NOT circuit 140a, is not effectuated. Therefore a start instruction signal 145a for the aforesaid motor 132a is not effectuated even if an operation switch 142a corresponding to the forced draft fan motor 132a is operated for starting, and consequently the motor 132a is not started. Even if either of operation switches 143a and 144a corresponding to a forced draft fan outlet damper 133a and the forced draft fan vane 134a respectively is operated for starting, opening operation instruction signals 146a and 147a for said auxiliaries are not effectuated, and consequently none of these auxiliaries performs an opening operation. According to the present embodiment, the starting and opening operations of all the auxiliaries 132a, 133a and 134a related to the forced draft fan 131a can be prohibited during the maintenance of the forced draft fan. This produces effects that such personal accidents as maintenance personnel being caught in a movable element of the forced draft fan 131a and as the personnel being tumbled down or caught in the movable element, killed in the worst case, by the reverse rotations of the forced draft fan motor 142a and the vane 144a due to the backflow of air into the forced draft fan 131a, owing to erroneous operations of either of the operation switches 142a and 144a and the operation switch 143a by an operator, respectively, are prevented from occurrence. According to the present invention, it is possible to detect automatically that some plant apparatus and auxiliaries are under maintenance and thereby to prevent dangerous motions of relevant apparatuses due to erroneous operations, and therefore personal accidents can be prevented from occurrence. The ideas described above with reference to figures 1 to 11 are premised on the thought that "peripheral apparatuses are stopped or closed", and accordingly the technological value thereof is derived from preventing the start or opening of the peripheral apparatuses on the occasion of maintenance. In a plant, the stoppage or closure of the peripheral apparatuses is confirmed generally before maintenance is started. If it should be missed that some apparatuses are in the state of operation or opened, checking of the start or opening will lose its meaning, and safety cannot be secured. In order to avoid this, it is effective to stop or close apparatuses forcibly when the state of maintenance (the release of locking of a cover or the opening of the cover mentioned with reference to Figs. 2 and 3) is detected. However, this measure is not based on the thought that the occurrence of a dangerous state is prevented (i.e. the thought equivalent to that stated with reference to Fig. 1), but based on the thought close to that of averting the dangerous state quickly. It is desirable, therefore, to take the following three-step measure. 1. The state of closure or stoppage of peripheral apparatuses is confirmed without fail before maintenance is commenced. 2. The state of maintenance is detected and a forced stop or closure signal is delivered to the apparatuses. 3. The state of maintenance is detected and a start or opening checking signal is delivered to the apparatuses. Next, the basic thought of the method of forced stop or closure stated in the above item 2 will be described by using Figure 12. Numeral 2 in Fig. 12 denotes a cover opening detector. The detail thereof is the same as that of the detector described with regard to Figs. 2 and 3, and it gives an output 3 when a cover 102 is opened or when the locking of the cover is released. However, the arrangement of Fig. 12 is premised on an assumption that an apparatus is opened or operated, and it is intended to effect switching over to the safe state. Therefore it can be assumed that a transient state of danger appears and thereby a measure is delayed, if the opening of the cover is detected on the occasion. It is preferable, accordingly, that the release of locking is detected. The output 3 is turned to be a stop or closure signal 9 through an OR circuit 8, and thereby an operation of stopping or closing the apparatus 10 is conducted. Besides, a stop (closure) instruction 6 of an operation switch 6 may also be impressed on the OR circuit 8. The circuit of Fig. 12 is applicable also to the interlocking circuits of Figs. 5, 7, 9 and 11, and by applying both ideas of Fig. 1 and Fig. 12, a double safeguard arrangement can be obtained. According to the present invention described above, the safety of maintenance personnel on the occasion of maintenance can be secured.

Claims: A plant or part thereof having a plant portion (11) delimited by a wall (100), a cover (102) openable in said wall to permit a person to enter the plant portion (11) to carry out maintenance work thereof; and piping coupled to the plant portion for carrying a flow to the plant portion; characterised in that there are valve means (13) on the piping; actuator means for opening or closing the valve means (13) to permit or prevent flow along the piping; cover opening detecting means (2) for detecting the opening of the cover or the release of locking means of the cover, said cover opening detecting means producing a cover opening signal in response to such detection; and controller means (4,8) which are coupled to the actuator means for controlling operation thereof; said controller means being coupled to the cover opening detecting means to receive the cover opening signal from it and being arranged so that, when such a signal is received, (i) operation of the actuator means to open the valve means is prevented; and/or (ii) a closure signal is sent to the actuator means to cause it to effect closure of the valve means if it is open. A plant or part thereof according to claim I including an opening operation switch (6) for instructing opening of the valve means (13); said switch being operable to provide an opening signal to the controller means which then causes the actuator means to effect opening of the valve means unless this is prevented by the receipt of the control signal from the cover opening detecting means. A plant or part thereof according to claim 2 wherein the controller means includes a NOT circuit (4) which inverts the cover opening detection signal to produce an output which constitutes an operation permission signal (5) when cover opening or release of locking is not detected; the controller means also including an AND circuit (8) arranged to receive the operation permission signal (5) and an opening operation signal (7) from the switch (6) and to produce an output for causing operation of the actuator means when said signals are received simultaneously. A plant or part thereof according to any preceding claim including a closing operation switch for instructing closure of the valve means; said switch being operable to provide a closing operation signal to the controller means which thus sends a closure signal to the actuator means on receipt of either a cover opening signal or a closing operation signal. A plant or part thereof (38) according to any preceding claim having a rotor (46a) installed inside of said plant portion or on a piping connected thereto, and rotor actuator means to give a driving output to said rotor in response to a start or stop instruction signal for the rotor, and which is employed when operations for maintenance of the aforesaid plant auxiliary are executed; and wherein the controller means are coupled to the rotor actuator means so that when a cover opening signal is received, operation of the rotor actuator means to start the rotor is prevented. A plant or part according to any preceding claim wherein a flowable material is supplied into and discharged out of the plant portion through inlet and outlet valve means, and wherein the controller means is arranged to prohibit the opening of the aforesaid inlet and outlet valve means when a cover opening signal is received. A plant or part according to any preceding claim wherein the controller means are arranged so that on receipt of a cover opening signal a closure signal is sent to the actuator means to cause it to effect closure of the valve means on the piping for carrying a flow to the plant portion. A plant or part thereof according to any preceding claim having a rotor installed inside of said plant portion or on a piping connected thereto, and rotor actuator means to give a driving output to said rotor in response to a start or stop instruction signal for the rotor, and which is employed when operations for maintenance of the foresaid plant auxiliary are executed, and wherein the controller means are coupled to the rotor actuator means so that when a cover opening signal is received, the actuator means is caused to act to stop the rotor forcibly.

Inventors: FUKAI MASAYUKI, IKEMATSU TAKEHIKO, NIGAWARA SEIITSU, FUKAI, MASAYUKI, IKEMATSU, TAKEHIKO, NIGAWARA, SEIITSU
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1988
Main classification: F16P3
IPC codes: F16P3