Patent Application
20170004942
This invention relates to an equipment isolation switch assembly, in particular for use in remote isolation systems.
Various types of equipment must be isolated from a range of energy sources including electrical energy (the most common) and mechanical energy including pressure and potential energy to enable safe maintenance and other work to be carried out. For example, conveyor belt systems used in the mining industry for transporting iron ore or other bulk materials can span significant distances. These distances can be in the range of many kilometres. Such conveyors are typically powered by electric drive motors: three phase electrical power is supplied wherein the voltage may range from low voltage ranges (from below 600V to 1000V AC), to medium and high voltage ranges (in the multiple kV range and extending to above 10 kV AC and even 33 kV AC). Such conveyors typically include brake systems which are also electrically operated.
Although different mine procedures and relevant safety standards may apply, a typical pre-requisite before permitting mechanical maintenance or other activity involving access to the conveyor belt system involves the electrical isolation of the conveyor system. This isolation ensures that the energy source powering the conveyor belts and associated equipment, i.e. electrical power, is removed from systems that—if energised—could cause a safety hazard. It will however be understood that equipment items other than conveyor systems also require isolation for maintenance and other purposes.
The isolation process is invariably safety critical and has, in the past, been time consuming, as described for example in the introduction to the Applicant's granted Australian Patent No. 2010310881 and International Publication No. WO 2012/142674, the contents of which are hereby incorporated herein by reference.
The remote isolation system described in Australian Patent No. 2010310881 enables equipment isolation to be requested at a remote isolation station associated with the equipment and subsequently approved through a plant control system, without mandatory visitation to the equipment by authorized isolation personnel. This remote isolation system significantly reduces time for achieving safe isolation, especially production downtime which can be very costly.
The remote isolation station includes an isolation switch means which must be switched to isolated mode subsequent to an isolation approval being received. The isolation switch means must also be locked, by a locking means, into the isolated mode thereby preventing re-energisation of purposefully isolated equipment. This is called a manual lock out system and current Western Australian mining regulations require lockout, applying a hasp then a personal lock on the hasp, to the isolation switch which is provided with a specific aperture for this lockout purpose.
An issue that may arise with lock attachment of this nature is that personnel may misunderstand the correct location for attaching the hasp and attach it incorrectly to the wrong part of the isolation switch.
The above discussion assumes use of a manual lock out system. However, other mechanically or electrically operable locking devices may become available in the future and the Applicant also seeks to address future potential issues with mis-application of such locking devices to the isolation switch.
It would be desirable to provide an isolation switch that minimises, or more preferably eliminates, the risk of misapplication of locking devices during the isolation procedure.
With this object in view, the present invention provides an equipment isolation switch assembly for use in a remote isolation system for remotely isolating an equipment item comprising:
an equipment isolation switch movable between a first position in which said equipment item is energised by an energy source and a second isolated position in which said equipment item is isolated from said energy source; and
an actuating device co-operable with the equipment isolation switch to move it between said first and second positions;
wherein said isolation switch assembly includes at least one securing means for securing said actuating device in co-operation with said equipment isolation switch whenever in operative state.
The equipment isolation switch assembly is advantageously configured to enable deactivation, for example where a user of the Applicant's remote isolation system decides to select an alternative isolation procedure under particular equipment operating conditions or where a control system of the remote isolation system indicates that selection of an alternative isolation procedure is required. Deactivation to a maintenance or bypass mode also permits maintenance of the equipment isolation switch and the remote isolation system. In case of deactivation, the securing means is removed allowing the actuating device, such as a removable key, to be removed from co-operation with the equipment isolation switch.
Such removal of the actuating device is permitted by the equipment isolation switch only when the associated equipment item(s) is (are) in normal position, not the isolated position. Such deactivation may also require other tasks to be completed before a remote isolation system is safely and completely removed from service. For example, completion of such tasks may involve the use of other keys, preferably rendered operable using a key exchange unit such as that described in the Applicant's Australian Provisional Patent Application No. 2015902557 filed on 30 Jun. 2015, the contents of which are hereby incorporated herein by reference. In embodiments such as this, the actuating device, such as a key, is multi-functional being used to implement additional tasks in the isolation system to just actuating the equipment isolation switch.
Conveniently, the actuating device is a key for moving the equipment isolation switch between the first and second positions to isolate equipment. Such key is typically a mechanical device (though other devices including electronic devices and signals could be used). Where mechanical keys are used, the switch module may take the same form as a conventional lock, for example a cylinder-lock working on a pin and tumbler principle. For reasons described above, the key is desirably both unique to the equipment isolation switch and removable under prescribed circumstances, the key circumstance being a requirement for deactivation of the equipment isolation.
The equipment isolation switch may be comprised within a replaceable switch module, a feature which is particularly advantageous under certain circumstances. For example, safety is a paramount consideration and, for this reason, it is undesirable to provide duplicate actuating devices with it instead being highly preferable for a unique actuating device to be provided to co-operate with any equipment isolation switch. Accordingly, if the actuating device is lost or stolen from the switch, even if intended to be removable under prescribed circumstances described below, replication is avoided and no replacement is available. Rather, the switch module is replaced with a substitute switch module including its corresponding actuating device following any required authorisation procedure. The original switch module may then be refurbished with a substitute actuating device in a manner with substantially lesser risk than encountered with duplicate actuating devices.
The securing means would be a mechanical or electronic means, or a combination of these which holds the equipment isolation switch and actuating device in co-operation through operation of a control system for the remote isolation system whenever the equipment isolation switch is operative.
The securing means may hold the actuating device in co-operation with the equipment isolation switch through operation of a control system for the remote isolation system. For example, the control system may prevent the actuating device from disengaging from co-operation with the switch unless specific conditions, such as faults, arise. The actuating device, such as a key, may be held captive to the switch—for example by mechanical interlock—unless the securing means is removed under control system authority. The control system could also prevent removal of any mechanical securing means such as the keeper plate described below.
The isolation switch requires to be locked out to complete equipment isolation. Currently, the lockout process is a manual process requiring application of a locking device such as a hasp and personal lock to the isolation switch, though electronic devices, such as smart cards, may be used in the future, for example as described in the Applicant's Australian Provisional Patent Application Nos. 2015902559 and 2015902564 each filed on 30 Jun. 2015, the contents of which are hereby incorporated herein by way of reference.
The above described isolation switch advantageously should not permit lockout unless the above mentioned control system for the remote isolation system electronically implements co-operation between the isolation switch and locking device in line with a series of permissives, which desirably involves completion of a logical sequence of requirements, selected to prevent hazardous release of energy from the equipment item following isolation. Importantly, this means, amongst other benefits, that personnel cannot complete the required lockout process by misapplication of a manual lock to an apparent lockout point or, by analogy, by way of some other form of locking device.
A preferred series of permissives would involve a first try start step involving attempted restart of the equipment item. Successful completion of this try start step actually involves a failure to restart the equipment item. A second step in the sequence, subsequent to successful completion of the try start step, would involve actuation of the securing means. Both steps are controlled by the control system of the remote isolation system.
In a preferred embodiment suitable for a manual lockout arrangement, the equipment isolation switch comprises a securing means including a plurality of lock members engageable to form a lockout point when permitted by the control system. Two such lock members are preferred, each configured with portions co-operable, when permitted by the control system, to form the required lock out point. Such portions may be in the form of cut outs, such as slots, which co-operate to form an aperture providing the isolation lockout point. A first lock member may be a fixed portion of the equipment isolation switch, possibly forming part of the exterior of the equipment isolation switch housing. A further lock member may be configured to be inoperable, for example being held captive at a desired location, until the control system authorises lockout. To reiterate, control system lockout authorisation is dependent on the correct isolation procedure involving successful completion of a series of permissives such as that described above being followed.
The further lock member may be held captive to the housing of the equipment isolation switch, for example by magnetic force (such as induced by a solenoid) or mechanical interlock. When the control system authorises a lockout, the further lock member is released, thereby being actuated through movement into co-operation with the first lock member to together form the aperture which provides the required lock out point.
Preferably, the equipment isolation switch assembly securing means comprises a plate lock member which, when positioned for isolation, partially or wholly covers the isolation switch to prevent it being moved from the isolated position. In such a case, the plate forms the further lock member and an additional securing means. The plate is connected to a hinge only operable to allow the plate to rotate into co-operation with the first lock member when authorised by the control system following completion of the correct isolation procedure.
Where a mechanical key is used, it typically requires to be inserted to activate the equipment isolation switch. Equipment isolation switches tend however to be subject to environmental factors, such as vibrations emanating from equipment or caused by climatic conditions. Such vibration could cause the key to be lost from the switch. Misuse or error might also result in key loss. To avoid loss in circumstances such as this, a retaining or keeper plate may be installed as part of the equipment isolation switch assembly following insertion of the key into the switch, the plate having an aperture through which a portion of the key extends for manual operation between the first and second positions. However, the aperture has insufficient dimension to allow removal of the key once the keeper plate has engaged the key. The keeper plate may itself be locked into position by a lock preventing unauthorised removal.
The position of the further lock member is preferably monitored by sensors and the control system for correct positioning whether for isolated and de-isolated states. An alert signal may issue where there is any variation from such correct positioning. Tampering with a locked out equipment isolation switch may also be monitored by sensors provided for the purpose.
The equipment isolation switch is advantageously employed in the Applicant's remote isolation systems which include a control system for approving isolation on permissible request logged by an operator at a remote isolation station. Such systems are described, for example, in Australian Patent No. 2010310881 and the Applicant's Australian Provisional Patent Application Nos. 2015902556, 2015902557, 2015902558, 2015902559, 2015902561, 2015902562, 2015902564 and 2015902566 each filed on 30 Jun. 2015, the contents of which are hereby incorporated herein by way of reference.
More preferably, the equipment isolation switch is integrated with the remote isolation station which also includes the required control panel and interface for effecting equipment isolation requests. The remote isolation station may be in a fixed position or may be configured to be mobile to suit specific applications. A plurality of remote isolation stations may also be provided for an equipment item. Where a remote isolation station is arranged to be mobile, for example in the form of a portable computer device or communication device using wireless communications, it will likely be possible to reduce the number of remote isolation stations well below that conveniently employed using fixed remote isolation stations.
Lockout of the equipment isolation switch, for instance at the above described remote isolation station may release an additional actuating device, such as a key, or equipment item for use in, or following, an isolation procedure. Such actuating device may be used to operate a specific equipment item and/or to access a particular area off limits other than when equipment is isolated. For example, barriers such as gates or doors may be locked during normal equipment operating conditions but when the equipment isolation switch is locked out, a key for removing the barrier, such as by opening a gate or door, is released enabling equipment maintenance.
The equipment isolation switch may be included in any desired remote isolation system, beneficially being included in new remote isolation systems or retrofitted to existing isolation systems, especially those remote isolation systems disclosed and/or supplied by the Applicant. Such remote isolation systems may be used in a range of applications including in the materials handling and mining industries. The equipment isolation switch assembly may also advantageously be used for isolating rail system components in railway infrastructure.
The term “isolation” as used in this specification is to be understood in its maintenance engineering and legal sense as not simply turning off a supply of energy to equipment, whatever the nature of that energy, but removing and/or dissipating energy to provide a safe work environment as required by applicable occupational health and safety regulations. In the case of electricity, as just one example, isolation is not achieved simply by turning off a power supply to the equipment. In such cases, the equipment could accidentally re-start or be restarted and cause injury to personnel, or worse. Isolation instead prevents such accidental re-starting and typically will also involve processes to dissipate any hazardous stored energy, in whatever form that energy may take (e.g. potential energy), from the equipment. For example, such an additional energy dissipation step could be effected in respect of a conveyor belt system by way of the braking cycle procedure as described in the Applicant's Australian Provisional Patent Application No. 2015902565, the contents of which are incorporated herein by way of reference.
The equipment isolation switch assembly of the present invention may be more fully understood from the following description of a preferred embodiment made with reference to the following drawings in which:
Referring to
The conveyor belt system 20 also includes a Tramp Metal Detector (TMD) 21 B for detecting tramp metal which requires removal to avoid damage to the conveyor belt 21. Prior to removal of tramp metal, the conveyor belt system 20 requires isolation, as described below, to make removal safer.
The conveyor belt system 20 and sub-station 30 are under the control and supervision of a plant control system 260 having a central control room (CCR) 40, via a DCS (Distributed Control System), a PLC (Programmable Logic Controller) and a SCADA (Supervisory Control and Data Acquisition System) as are commonly used and would be well understood by the skilled person. Item 41 in
The remote isolation system 10 comprises fixed remote isolation stations 12 and 14 which are located proximate to the conveyor belt system 20. It will be understood that remote isolation stations 12 and 14 could be replaced or supplemented by one or more mobile isolation stations, for example in the form of a portable computer devices (in certain applications these potentially being provided as smartphones) or communication devices using wireless communications as disclosed for example in the Applicant's Australian Provisional Patent Application Nos. 2015902561 and 2015902562 , the contents of which are incorporated herein by reference. The remote isolation stations 12 and 14 may be powered from the plant grid, other power networks or alternative power sources, conveniently such as solar power.
The remote isolation system 10 also includes a master controller 50 incorporating a human/machine interface (HMI) in the form of a touch sensitive screen 51 which displays human interpretable information. The master controller 50 is also located within sub-station 30. Remote isolation stations 12 and 14 are in communication with master controller 50 and each other via communication channels 11 and 13. These communication channels can be provided in any suitable form including hard wired or wireless forms with an open communications protocol. Ethernet communications are particularly preferred to enable flexible system updating on site if needed. Communications must be via safety rated communications protocol software such as Interbus Safety or PROFIsafe which are well known within the mining and materials handling industries. This will ensure that the communication channels are monitored and diagnostic tools are available for fault control and rectification when required.
Further description of the electrical layout and operation of the remote isolation system 10 is provided in the Applicant's granted Australian Patent No. 2010310881, the contents of which are incorporated herein by reference. In summary, the conveyor belt system 20 is isolated by a process involving the following sequence of steps;
Control panel 700 also includes:
Control panel 700 also includes an equipment isolation switch block 765 which prevents completion of the isolation process by locking with an operator's personal lock at isolation switch 400 until the correct remote isolation procedure, for example as described in Australian Patent No. 2010310881 has been completed. In particular, a correct remote isolation procedure requires a try start step to be completed by an operator by activation of a try step button 780 before any manual lock out is possible. The equipment isolation switch 400 is designed to prevent any such manual lock out before the correct isolation procedure has been completed.
The try step is essentially a means by which an isolation can be proved by attempting a plant start. Failure of the plant to start can be considered as confirmation that an operator has isolated the correct plant or equipment item. The operations that occur when a try step is performed may vary from site to site and application to application, but by way of example, the control system can provide the following actions when the try step button 780 is pressed:—
Housing 220 also accommodates, noting its interior as well as exterior, electrical and mechanical components and systems to enable operation of the isolation switch box 200. Power and communications cables are connected through socket 280 (detachable by removing screws 282) as shown in
Equipment isolation switch 400 must co-operate with a switch actuating device, which in this embodiment is provided in the form of key 500 whenever remote isolation system 10 is operative, i.e. available to achieve remote isolation. Key 500 is shown in greater detail in
For various reasons, including vibration of the switch box 200 or misuse, there is some risk that key 500 could be lost from equipment isolation switch 400. To minimise such risks, the equipment isolation switch assembly 200 includes at least one securing means to secure the key 500 into co-operation with equipment isolation switch 400 whenever it is operative, not necessarily in isolated condition as will be apparent from description below.
A first such securing means is provided by retaining (keeper) plate 405 which is designed to prevent removal of key 500 from equipment isolation switch 400 once locked into position. Keeper plate 405 is shown as a separate component in
Keeper plate 405 has dimensions allowing a neat fit between upper surface 240A of magnetic portion 240 (with which lower flange 405B of keeper plate 405 is in contact) and upper flange 230 (with which upper flange 4050 of keeper plate 405 is in contact) of switch box housing 220.
Installation of keeper plate 405 will now be described with reference to
Equipment isolation switch 400 is now operable by turning the key 500 between a first “NORMAL” position in which the drive motor 22 for the conveyor 21 is electrically energised (i.e. not isolated) and a second “ISOLATE” position in which the drive motor 22 is electrically isolated and thus without power thereby facilitating any maintenance works which may be required. That is, the isolation switch 400 maintains the isolated position/status of the isolators when rotated to the ISOLATE position, and when rotated or returned to the NORMAL position, de-isolation occurs.
However, whilst turning the key 500 from the NORMAL to the ISOLATE position is a necessary step in establishing an isolation state when authorised by master controller 50, this alone does not provide a sufficient condition for the remote isolation system to isolate the conveyor belt 21 and its drive motor 22. Importantly, the equipment isolation switch 400 must be locked out, in this case, by a manual lockout procedure. Further, manual lockout is not provided for by equipment isolation switch 400 unless a lockout point is provided by co-operating a locking device with the isolation switch 400 under the control of master controller 50. Authorisation of manual lockout by the master controller 50 requires the correct remote isolation procedure sequence to have been be completed as summarised above and as described in detail for example in the Applicant's Australian Patent No. 2010310881.
The locking device for equipment isolation switch 400 has two lock members, the first being formed by cut out or slot 291C located in a fixed position top flange 230 of the switch housing 220. Slot 291C would alone not typically accommodate a locked padlock or hasp as required for a regulatory governed isolation. The second lock member is configured as a plate or flap 291 which has a cut out or slot 291B arranged at one end of flange 292 which corresponds with the cut out or slot 291C when the flap 291 is raised to cover the key switch 400. The cut out or slot 291C is also designed to alone not support attachment of a hasp or personal lock 600 thereto. The flap 291 also includes a central slot 293 arranged to correspond with the outer end 510 of the key 500 when the flap 291 is raised to cover the isolation switch 400. The slot 293 and flap 291 are designed with dimensions such that they alone cannot co-operate with a hasp 600 (as depicted in
The lock members 291 (and in particular its slot 291B) and 2910 will only be allowed to co-operate to form a lockout point 297 (as best depicted in
As shown in
When isolation is authorised following correct procedure and key 500 is turned to the second ISOLATE position (as shown in
Further detail of the solenoid operated mechanical interlock is shown in
In locking position, flap 291 covers the isolation switch 400 though providing for the outer end 510 of the key 500 to extend through slot 293. When this occurs, slots 291B and 291C co-operate to form an aperture 297 or lockout point through which a hasp 600 is securely and correctly accommodated for lockout as shown in
The master controller 50 of the remote isolation system properly deactivates flap solenoid 301 enabling lockout to occur as above described only when an unsuccessful try step (i.e. attempt to restart conveyor belt system 20) is first completed. Until that point, flap 291 is held captive in its resting position as best seen in
Sensors, such as proximity sensors similar to sensors 315 described above, are used to monitor the position of the key 500 in isolation switch 400 and to ensure that various components (e.g. key 500, keeper plate 405 and flap 291 (through sensors 315)) are correctly positioned when the system is in a “resting” or NORMAL (energised) state or a “locked out” or “ISOLATE” condition. Corrective action may be initiated if deviation from the correct position is indicated. The system can also be configured to generate alert signals if such a scenario were to occur. Sensors can also be arranged to indicate any tampering with the flap 291 such that corrective action may be initiated if any tampering is detected.
Upon correct de-isolation being initiated, the flap 291 is rotated back to its resting position to again be held captive against resting block 240 through operation of the solenoid actuated magnetic interlock.
The equipment isolation switch 400 is only operable when the key 500 is engaged with it. Equally, the key 500 must be removed from the isolation switch 400 when deactivation of the equipment isolation switch 200 is required. Control system or authorised personnel approval would be required prior to any such removal which, even then, is only permitted when the isolation switch 400 is in the NORMAL condition. Importantly, key removal is not permitted without additional validation steps if the key switch 400 is in the ISOLATE condition. Deactivation would typically require other tasks to be completed before a remote isolation system is safely and completely removed from service and the equipment item in question can be re-energised for normal operation. Completion of such tasks may involve the use of other keys, preferably rendered operable using the key exchange unit described in the Applicant's Australian Provisional Patent Application No. 2015902557, the contents of which are incorporated herein by reference.
A further embodiment of the invention is now described with reference to
However, in such circumstances, a module including isolation switch 400 may be removed and replaced with a substitute switch module 900 including its corresponding actuating device following any required authorisation procedure. Switch module 900 includes a cylinder or barrel 905 including the isolation switch 400 and a latch portion 910 including the switch locking mechanism 915. A key (not shown) but having different configuration of notches than key 500 would also be provided. Barrel 905 also includes a different pin arrangement to the former switch module. However, both switch modules conveniently work on the known pin and tumbler principle which is accordingly not described further here.
The original switch module may then be refurbished with a substitute key 500 (but with a different arrangement of notches 520) in a manner with substantially lesser risk than encountered when duplicate keys, including master keys, are provided.
Application of the isolation switch assembly as described above ensures that isolators do not de-energise, and that a lock flap associated with the isolation switch 400 is held captive until all isolation steps are verified, hence preventing any personal locks being attached until isolation is confirmed and safe maintenance or work conditions are confirmed. Importantly, no lock points are provided on the isolation switch 400 or switch box 200 until an isolation has been effected.
Furthermore, the isolation switch assembly facilitates a desirable two-stage process required to achieve lock-out by an operator and hence provides an additional level of safety for the operator of the remote isolation system, Specifically, if a try step attempt to start the plant after a request to isolate is approved (i.e. restarting of the plant is unsuccessful as desired), the isolation switch 400 is then able to be turned to an ISOLATE position. When actuated, the isolation switch subsequently results in de-energisation of the solenoid which retains the lock-out flap 291 which can then be rotated into engagement with the isolation switch 400 and key 500 and in turn provide the required lockout point for the operator.
Modifications and variations to the equipment isolation switch of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present invention. For example, the above discussion refers to isolation of conveyor belt systems at mine sites by isolating conveyor belt drive motors from an electrical energy supply. It will be understood however that different equipment may be isolated from different energy sources using the equipment isolation switch described herein.
Furthermore, while the control panel 700 has primarily been described as including a human machine interface (HMI) 710 with a touch screen 1265 and a series of buttons and lights (e.g. 740, 750, 760, 770, 780 etc) to enable an operator to request an isolation event, it should be noted that the control panel 700, and specifically the touch screen 1265, may be configured to provide greater control and more information about isolation system steps to an operator (or indeed full control and all information to do with the isolation system). That is, a more ‘digitally’ based input means (or indeed a totally digital system) may be arranged for operation instead of an analogue or part analogue system as described herein to enable control of the equipment isolation system according to the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015902554 | Jun 2015 | AU | national |
