Electrical Interlock Research Articles

Energy conservation at high power consuming holding furnace with modified coil design and electrical circuits

This paper deals with high energy consuming induction holding furnace. The improved version of coil design along with additional electrical interlocks and alarm, modified hydraulic controls, strengthening mechanical structures and energy saving proposals at holding furnace fume extraction system ensures trouble free operation of furnace and hence continuity of production at all the planned plant operational days. This project involves in purchasing of D-section copper extruded coil from Europe–Switzerland for its extended length from existing 3 meters long to 9 Meters which enables in reduction of coil joints. The performance of the holding furnace has improved in terms ofits energy consumption per ton of liquid metal. The payback period for the estimated investment will be less than 2 years.

Tsinghua University Freefall Facility (TUFF): A 2.2 Second Drop Tunnel for Microgravity Research

Ground-based freefall facilities are to create microgravity environment on earth for studying the space-related or fundamental sciences, which have been widely used in the field of combustion, fluid, physics and material sciences. Aiming to serve for the broader microgravity science and preliminary tests for projects onboard the upcoming assembly of Chinese Space Station, a 2.2 second freefall facility was designed and built in the Lee Shau Kee Science and Technology Building on the campus of Tsinghua University in Beijing. This facility is composed of five systems: (I) freefall tunnel and safety cables; (II) release and retrieve system; (III) the capsule; (IV) brake system; (V) electrical control and safety interlock system. The capsule consists of an outer drag shield and an inner rig of which the total weight is 280 kg. The capsule is released by a pneumatic chuck that minimizes disturbance of the release operation. The eddy current brake modules made of several permanent magnets are applied to decelerate the capsule without power supply. This paper primarily discusses the tests designed and conducted to characterize the performance of such facility in many aspects. The results show that during freefall, the microgravity level of 10-3 g can be achieved for 2.2 second. Concerning movement of the inner rig relative to the drag shield during freefall, the clearance of 0.43 m and relative velocity of 0.62 m/s were specified. The deceleration can be controlled within 15 g. The terminal velocity of capsule in the brake system ranges from 0.4 to 0.5 m/s depending on the actual weight of capsule. The noise level in the entrance section of brake system is about 75.6 dB. The duration of this noise is very short (<1 s), suggesting that the operation of facility is environmentally friendly to the operators and people working in the building.

Forensic Engineering Analysis of Unintended Movement of Powered Industrial Trucks

Unintended movement of powered industrial trucks after operators have left the operating position has led to serious — and sometimes fatal — accidents. Even though operators are trained to prevent unintended movement of powered industrial trucks, they can forget to shut off the power source or activate systems to prevent the unintended movement when leaving the truck. Operators are known to make mistakes, especially if they are working in a fast-paced environment and are required to frequently leave the trucks. Engineershave designed electrical interlocks and other systems (e.g., automatically applied parking brakes) to prevent unintended movement; however, not all powered industrial trucks are equipped with them. Furthermore, some of these systems only disconnect the power source from the truck’s drivetrain. These trucks can continue traveling due to their initial momentum or by gravity if the truck was left on a slope. The purpose of this paper is to address the design of forklift operator presence detection systems and unintended movement of unoccupied forklifts through a safety and forensic engineering analysis, highlighting a brief case study to examine the concept of use and foreseeable misuse — and to review the legal concept of strict product liability.

Electrical detection of liquid lithium leaks from pipe joints.

A test stand for flowing liquid lithium is under construction at Princeton Plasma Physics Laboratory. As liquid lithium reacts with atmospheric gases and water, an electrical interlock system for detecting leaks and safely shutting down the apparatus has been constructed. A defense in depth strategy is taken to minimize the risk and impact of potential leaks. Each demountable joint is diagnosed with a cylindrical copper shell electrically isolated from the loop. By monitoring the electrical resistance between the pipe and the copper shell, a leak of (conductive) liquid lithium can be detected. Any resistance of less than 2 kΩ trips a relay, shutting off power to the heaters and pump. The system has been successfully tested with liquid gallium as a surrogate liquid metal. The circuit features an extensible number of channels to allow for future expansion of the loop. To ease diagnosis of faults, the status of each channel is shown with an analog front panel LED, and monitored and logged digitally by LabVIEW.

Installation, Operation, and Maintenance of Safety Interlocks in Medium-Voltage Motor Starters

This paper describes the benefits and techniques for performing maintenance on the electrical and mechanical interlocks in medium-voltage (MV) motor starters. These interlocks are safety features built into MV motor starters to prevent the isolation switch from being operated while the motor is running, which could result in a serious injury because the isolation switch is not rated to operate under a load. The electrical interlock is designed to open the contactor if an attempt is made to rack the isolation switch on or off the bus while the contactor is closed. The mechanical interlock is designed to prevent the isolation switch from physically being opened or closed if the motor is running or the contactor is closed. These interlocks are part of the equipment design and are defense mechanisms to prevent a potentially serious injury. During a maintenance turnaround, the operation of the mechanical and electrical interlocks was function tested. The interesting findings from these tests are outlined hereinafter.

Dose profile modeling of Idaho National Laboratory's active neutron interrogation laboratory

A new laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for deuterium–tritium (DT) fusion (14.1 MeV) neutron generators (2×10 8 n/s), deuterium–deuterium (DD) fusion (2.5 MeV) neutron generators (1×10 7 n/s), and 252Cf spontaneous fission neutron sources (6.96×10 7 n/s, 30 μg). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault. The larger vault is designed to allow operation of the DT generator and has walls 3.8 m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for 252Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield walls and entrance mazes and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.

5350562 Method and apparatus for sterilization and separation of plastic and non-plastic medical wastes

Medical waste products including plastic and non-plastic elements are placed in a metal container which includes a raised insert element for supporting the waste above the bottom of the container. The container and used medical waste products are subjected to dry heat treatment at temperatures below the waste material flash points but of sufficient temperature and for a sufficient time to melt the plastic elements as well as to sterilize the contents. During the heating process the metal, rubber and other non-plastic elements remain on the raised insert; whereas, the molten plastic flows through or over the side of the insert to the bottom of the container. Upon cooling the plastic and non-plastic components of the medical waste products are separated as well as being sterile such that the container can be opened and the contents separately handled for appropriate recycling. The dry heat generator conveniently may be placed in a medical office or the like and is microprocessor controlled to obtain the desired end products. The processor additionally controls an electrical interlock system whereby the heat generator unit may not be opened until an entire heat cycle has been completed, and the waste products have cooled to a safe temperature.

The Circumvention and Failure of Electrical Interlock Switches

Electrically interlocked covers and gates on industrial machinery are used to protect the operator from the point-of-operation. When the electrical interlock switches on those barriers fail to function, because of deliberate circumvention or an electrical or mechanical failure, serious accidents frequently result. This paper reviews the methodology used for the design of those interlocking systems, the techniques employed to circumvent them, and their common modes of electrical and mechanical failure. The author provides detailed illustrations and a series of check lists, outlining the protocol for the forensic engineering investigation of such occurrences.

Testing of a medical linear accelerator's computer‐control system

In August of 1987, the Radiation Oncology Center at the Mallinckrodt Institute of Radiology became the first academic-medical-center user of Varian's computer-controlled therapy accelerator, a prototype version of the 2100C. Installation was accomplished by the retrofit of a computer system to our two-year-old Clinac 1800. Being well aware of the malfunctions that occurred in other computer-controlled accelerators, we took extraordinary measures to assure proper operation of the new, computerized, system. Our acceptance procedure included tests of (i) mechanical systems (isocentricity, digital readouts, etc.); (ii) radiation parameters (flatness, symmetry, output, etc.); (iii) manual safety systems (emergency off switches, etc.); (iv) the computer console systems (communications integrity, state integrity, etc.); and (v) the interlock systems (some 50 electrical, mechanical, and/or computer-controlled interlocks). As items (i), (ii), and (iii) do not differ significantly from the tests for a non-computer-controlled machine, they will not be discussed here. Rather, this report will concentrate on the methods that were devised to test the computer-control and interlock systems.

PLC-based interlock system for superconducting magnets

The development of an electrical hazard interlock system based on dual redundant programmable logic controllers (PLCs) is described. Sensitive I/O is implemented and processed in a redundant fashion. The PLCs make sure that terminal covers cannot be opened while dangerous currents are flowing, and they redundantly shut off the power supplies if any interlock violations, faults in the I/O circuits, or problems in the PLC system itself are detected. A first version of the software running on a single CPU has been developed and is being adapted and finalized for installation in the final PLC systems. A description is given of the application, the PLC system, the software architecture, and the hardware and software redundancy schemes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Self-checking safety interlock system

A novel electrical self-checking interlock system for the petrochemical industry is discussed that meets the goals of eliminating fire, explosion, and chemical releases by providing more reliable safety shutdown systems. The design, operating principles, and performance characteristics of the microprocessor-based self-checking safety interlock system are described. With some modification the system can be programmed to verify functionality of the final interlock elements for additional safety improvement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microcomputer calculation of fault levels for operational interlocking

It is shown that an electrical operational interlock for a power generating station must be capable of online fault-level calculations and that conventional methods are outside the capabilities of current 8-bit microprocessors. An algorithm is then developed to calculate fault levels, which is suitable for any network whose associated graph is a tree. The approach is based on the fundamental concepts of fault level and reduction processes related to the network graph. The suitability of this algorithm to practical systems is demonstrated by means of a case study, the accuracy of the computed fault levels being shown to compare very favourably with those from a conventional program.

Discussion on “Electrical interlock design for complex high-power switching networks”

Discussion on “Electrical interlock design for complex high-power switching networks”

The Application of a Microprocessor to Complex Electrical Interlocks

The electrical interlock logic for a complex high power switching station is presented and shown to be difficult to implement using conventional techniques. An alternative method of implementation, that of using a microprocessor to perform the interlocking function is proposed. The results of a feasibility study on this proposal are discussed and are shown to verify this application. Two methods of programming the interlock logic are described, the provision of both making the microprocessor system essentially self-validating.The paper is concluded by a summary of the microprocessor requirements in this application, especially operating time and memory.

Electrical interlock design for complex high-power switching networks

The paper reviews the derivation of interlock logic and the resultant interlock circuits for conventional double-busbar substations. These methods are then shown to be inadequate when the number of operating constraints on each switch and the degree of network interconnection are increased. A new method of deriving the interlock logic that can be converted directly into hard-wired form is then presented. The application of this method to the Dinorwic pumped storage scheme is given as an example. The ways by which conflicts between safety and operating requirements can be overcome are then described. Finally, the methods by which such complex interlock logic may be checked are discussed and examples given of the application of decision tables to this task.

A comprehensive safety shutter and collimator coupling for the Philips X-ray tube shield PW 1016

A set of safety shutters and collimator couplings for the Philips X-ray tube shield PW 1016 have been designed and made for use with (i) the Enraf-Nonius Weissenberg camera, (ii) the Charles Supper precession camera, (iii) the Philips Debye-Scherrer powder camera, (iv) the Nonius Guinier powder camera and (v) unused tube windows. The shutter couplings provide (i) a scatter shield around the filter disk, (ii) a scatter shield around the collimator face, (iii) a gravity and spring-loaded safety shutter over the direct beam, (iv) an electrical interlock to the shutter solenoid by camera movement, (v) a readily visible shutter knob, (vi) a fail-safe green lamp for indication that the electromagnetic shutter is closed and (vii) easy movement of the filter disk.

THE GRENZ-RAY OUTPUT CHARACTERISTICS OF A SUPERFICIAL THERAPY MACHINE.

In a superficial X-ray therapy unit, the Dermopan, recently installed at this hospital, an unexpected relationship was observed between X-ray output and tube current when the latter was varied from the specified value at the 10 kV setting. It is thought worth while to record this observation, since failure to appreciate this behaviour could lead to serious errors in dosage. It will also be seen that, by means of a simple adjustment of the control circuit of the machine, this characteristic can be turned to good account by providing improved dose control. The equipment uses a self-rectified tube with a beryllium window. A selector switch on the control panel provides for operation at 10, 29, 43 or 50 kVp. An electrical interlock system ensures that the tube can be energised only when the filter appropriate to the selected kilovoltage is in place. A fine control of line voltage is provided. A tube current of precisely 25 mA is specified at all four X-ray qualities. Tube current control is smooth and adequat...

A Portable Synchronous Interlock Projection System

The studio-equipped electrical interlock projection system has certain disadvantages. It is expensive, cumbersome and stationary. A portable, lightweight interlock projection system, which employs mechanically locked-in sync of 16mm motion-picture film with the 16mm magnetic soundtrack, has been developed. The films are synchronized on a common sprocket-driven roller of a conventional optical, or optical/magnetic, projector. A series of rollers leads the magnetic film from its supply reel to the sprocket and then to its take-up reel. Constructed of simple, inexpensive components, it offers many advantages to the smaller commercial producer and the in-plant film department.

Improved 16mm Projector for Research Films

The flicker-free, slow-motion and single-frame projector described in the November 1954 issue of the SMPTE Journal has been completely redesigned to give more reliable and smoother operation. In the transition from cine to single-frame projection, the 5-blade shutter is shifted to one side, leaving a single 42° blade to occult the film aperture during film transport. An electrical interlock in the push-button-triggering circuit excludes any possibility of overrun and assures uniform registration of successive frames. Also described is an experimental version of the projector with a 10-blade shutter and 12° pulldown. It provides relatively flicker-free projection at speeds from 5 to 3 frames/sec.

The development and design of electrical control-gear for machine tools

The paper deals with some of the technical considerations of the design and application of control gear to machine tools. The application of electrical control to machine tools is compared with other orthodox types of control gear, and the choice of electrical control gear is discussed with particular reference to the frequency of operation. Design of components (in particular, contactor design) is given due consideration, and the paper also shows how design may be based on results obtained from experimental work and past experience. After a note on complex schemes of control, the need for incorporating reliable interlocks is stressed, especially electrical interlocks involving auxiliary switches. Thesupply voltage is shown to have its importance, and low-voltage control circuits are compared withthose operating from line voltage. Speed control is next treated, with some regard to the application of electronics. The importance of motor protection is stressed, with particular reference to protection by h.r.c. fuses. Electricbraking, especially the d.c. injection method, is dealt with in some detail. Types of timing devices are described, and the electrical timer is compared with mechanical and thermal types. After discussing d.c. supply and its advantages over a.c. supply in connection with motor speed control, future developments in design of control gear and its application are reviewed.