Issue 2/2005
03/02/05
Modules for safe and sure operation, monitoring and documentation in elevators
P. Pini, B. Eng.
1. Introduction
Precise measurements instead of subjective “hunches” are the beginning of correct diagnostic procedures. The new ISO 18?738 sets down the standards to be applied in measuring elevators travel performance and ride quality. This makes it possible to measure and compare quality! This is having the predictable effects even today. On the one hand there are the manufacturers, installation and service companies whose qualities and performance can be measured and compared. On the other hand there are the planners, operators, inspectors and elevator users who can profit from this advancement, and will certainly want to do so.
Category: Issue 2/2005
Posted by: Editor
The Henning GmbH has developed the LiftPC® diagnostics system to meet the special needs of elevator and building utilities technology. This system takes the first step beyond the traditional boundaries of the elevator system, creating an interface with building utilities technology and even enables networking with an external facility management system. High-performance hardware and software are used here. The individual modules may be employed independent one of another and may be combined at will, in flexible configurations tailored to the owner’s individual requirements.
2. The diagnostics system
Figure 1 shows schematically the sequence followed in Henning LiftPC® diagnostics. The sensors to measure the elevator data which are of interest serve as the starting point. Shown symbolically at the top are the following:
The individual modules are introduced below.
3. Mobile diagnostics
Even in its basic version, comprising just an accelerometer, the evaluation software and a standard laptop computer, the Henning LiftPC® modular diagnostics system is superbly suited for measurement and evaluation of elevator performance data and ride quality.
The simple operating concept makes for quick set-up and use.
The measurement tracings for acceleration in the X, Y and Z axes are displayed while the car is traveling so that faults are immediately visible. After the test trip is completed, the other curves are derived from the data collected and the performance values are determined. The performance levels which are achieved are the first items of interest to elevator makers, maintenance and service companies, and the owners in regard to “their” lifts:
• Acceleration and deceleration curves along the direction of travel
• Velocity curve during approach
• Time/path charts to locate problems at guide rails
• Jerk and vibration originating at the rail guides
• Irregularities at the doors (accounting for 60 to 80% of all unplanned service calls)
• Quality of motor regulation during acceleration and deceleration
• Evaluation and documentation as per ISO 18 738
All the measured and calculated data on travel performance and ride quality are automatically summarized in the diagnosis report. This document is of major assistance:
• When preparing for commissioning and approvals procedures
• For carefully planned responses whenever faults should occur
• For effective maintenance and monitoring
• To document the attained performance levels
• To determine ride quality as per ISO 18 738
• When preparing quality certificates.
Objective measurement and evaluation instead of subjective estimates will make a considerable improvement in fault diagnosis. Any deficiencies will be recognized immediately; the proper corrective measures can be initiated at once and then checked to make sure they have actually rectified the problem.
Consequently, mobile diagnosis makes it possible for the first time ever to schedule preventive maintenance and repairs exactly as required by the condition of the lift. Regular use of this system makes it possible to detect changes as they occur and to avoid breakdowns. A tremendous increase in economy can thus be achieved.
Inspections in the event of complaints and verification following repairs can be carried out immediately. Any problems which might occur when installing new systems will be revealed early on and can be rectified at once. This is of great benefit when preparing for commissioning and approval by local supervisory authorities.
4. Professional diagnosis
Adding further sensors and software modules to expand the Henning mobile system presented here will turn it into a thoroughly professional diagnostics tool.
• Checking the drive brakes
Employing a new and patented method, the accelerometer is used to measure precisely the effects of the drive brakes during emergency stopping with the car travelling empty. The values can be extrapolated to verify efficacy at full load without having to use extra test weights for this purpose.
• Checking rope load adjustments
The individual rope load sensor, another patented device, is used to verify uniform load distribution within the set of ropes and, in the event of deviations, to make corrections at the ropes or drive sheave before damage can occur.
• Checking the safeties
The accelerometer and the individual rope load sensors make it possible to measure exactly the effectiveness of the safeties during no-load operation, taking account of the influence of the counterweight. This information can be extrapolated to verify effectiveness at full payload, without having to schlep test weights to the site.
• Checking door parameters
The new door force sensor is used to examine the doors for compliance with the limit values for closing power, kinetic energy and closing velocity as set forth in EN 81-1.
The new door force sensor is used to examine the doors for compliance with the limit values for closing power, kinetic energy and closing velocity as set forth in EN 81-1.
5. Continuous diagnosis
Any configuration of the Henning LiftPC® diagnostics system discussed here may also be installed permanently at any given elevator. This enables status-oriented maintenance and repairs. An “early warning system” sends reports to a control center at a remote location. Operators working there can undertake action to rectify defects before a component fails.
Figure 5 provides a schematic overview of the components used in a stationary diagnosis system. Familiar technology may be found here, comparable with other remote monitoring systems which forward data to a control center by way of data transmission protocols.
What is new, however, is that all types of elevators can be continuously monitored, regardless of the elevator control system make or model which might be installed. An intelligent peripheral module, the LiftPC®, is used for this purpose. Here it is possible, using additional sensors, to generate signals which the elevator controls do not provide.
The function normally carried out by the laptop computer in mobile diagnostics is handled here by the LiftPC® peripheral module. It continuously acquires all the measured data and evaluates it immediately. Trends for all the recorded parameters are projected and monitored. Only where predetermined limit values are violated will a report be forwarded to the control center, so that it need only deal with alarm and fault messages. The data kept in storage at the elevator can be called up by remote query as needed for diagnostic or archiving purposes.
Additional sensors are used here.
The new rope load sensors made by Henning, one attached to each individual rope, register variances in rope forces within the rope set. Deviations are detected and reported early on, before unacceptable wear occurs and service life is shortened.
With the use of high-resolution pulse counters at the drive and at the absolute value transducer both rope and sheave wear – and traction and even rope stretch and wire breaks – can be automatically detected and measured using a novel Henning process. Thus the retirement age for the ropes and the need for repair work at the sheave can be detected automatically and indicated in good time.
Figure 6 shows by way of example the vibrations in an elevator car, recorded continuously over two months and averaged for all trips. Quite noticeable here is the improved value for acceleration along the X axis (measured perpendicular to door motion) following a change in the car guides (slip guides). By contrast, the Y value shows a temporary increase due to the close tolerances of the new guides which, how-ever, run in after a short period of time.
In the same way additional trend curves for all the other sensors are automatically developed and evaluated. Should limit values be violated, then fault reports can be generated automatically and displayed at the control center.
The advantage of continuous diagnosis using the Henning LiftPC® concept at a glance:
• Status-oriented maintenance and repairs at pre-planned maintenance intervals
• Considerably improved troubleshooting, thanks to objective measurement and evaluation
• Defects are recognized immediately and the appropriate corrective measures can be initiated without delay and then verified for effectiveness
• Documentation of performance
• Avoidance of downtimes by detecting changes as they occur
• Ideal utilization of capacities remaining to retirement
• Cost reduction; avoiding time losses
6. Electronic elevator custodian
A further module in the Henning-LiftPC® system is the “electronic elevator custodian.” The new Operating Safety Ordinance in Germany no longer specifically mentions the need to appoint a custodian, but responsibility for the system’s safety is explicitly assigned to the owner/operator. In the absence of proof of regular system inspections, the potential liability borne by the elevator owner/operator can come to represent an incalculable risk.
Providing a human custodian for the elevator is often an organizational problem for the owner/operator and above all a liability issue. If the custodian is not on site or is otherwise unavailable, then the supervisory authorities can shut down the elevator. Elevator owners can counter this problem by installing the LiftPC® custodian module made by Henning.
The LiftPC® elevator custodian checks – autonomously, fully automatically and around the clock – the following critical factors:
• Leveling of the car at the landings
• Photoelectric sensors
• Hoistway and car doors
• Car illumination
• Glass breakage
• Monitoring the inspection and test intervals
• Monitoring and testing the emergency call system
• Monitoring and testing the “open door” button
• Weekly self-test
The custodian shuts the system down immediately should a potentially hazardous condition arise. An operational safety alarm (warning report) is transmitted instantly to the control center and can be forwarded to the technician in the field either by e-mail or text messaging.
7. Interactive control technology
The Henning LiftPC® control technology offers the additional convenience of being able to monitor and initiate elevator functions from a remote workplace. This is possible in a stand-alone configuration or with the controls integrated into the facility management network.
The monitoring functions in this control technology offer these capabilities:
• Continuous monitoring of operations
• Visualization of relevant system functions (status of doors and photoelectric sensors, car moving or stopped etc.)
• Automatic and immediate, on-screen reporting of any faults as they occur or notification of service employees by way of text messaging or e-mail.
• Remote actuation of the “door open” button, emergency call button, alarm button
• Shutting down the system etc., independent of the elevator controls
• Monitoring maintenance intervals
• Communication with the elevator by way of analog and digital telephone lines, GSM, GPRS, 433 MHz, Bluetooth and Ethernet
• Logging interventions and maintaining a fault log
• Compiling statistics on of the elevator
• Administering master records and password access
• Simple user guidance owing to the familiar Windows graphic user interface
Visualization is not limited to just a single lift but can also be expanded to cover banks of elevators (Figure 9).
If the data protocol for the elevator controls is known, then it is possible to implement direct access to the controls – with all the functions they offer – so that, for instance, the fault memory in the controls, the statistical functions or the configuration of such functions can be read out and edited at the remote workplace.
8. New database concepts
The new LiftPC® database module offers new options for analysis in the interest of determining quality in elevator systems. Here all the measured data on performance and ride quality, as supplied by the mobile diagnostics unit, are administered in a logical fashion; this make it possible for the first time to compare the elevators through time. In addition, all the essential engineering features of the lifts are registered to any desired degree of depth and detail. This enables central statistical analyses in the form of tables and graphs. Moreover, using an Internet database, individual units can be compared anonymously with the average for all lifts of similar design.
9. Summary
The LiftPC® system made by Henning GmbH is a complex diagnostics, remote supervision and monitoring system designed especially for elevator engineering. It is made up of high-performance hardware and software of modular design. These modules can be combined as required, without regard to the elevator’s type and maker.
• LiftPC® mobile diagnostics – evaluations of performance and ride quality, important for installation and service firms and for owners, expert assessors and inspectors when verifying lift performance.
• LiftPC® professional diagnostics – the expansion to include measurements which are relevant to safety.
• LiftPC® permanent diagnostics – for automatic, status-oriented maintenance and repairs, with early warning alarms forwarded to the control center (before the elevator fails).
• LiftPC® AWF – the electronic “lift custodian” function.
• LiftPC® control technology – the interactive control center for continuous operational monitoring and remote supervision, interfacing with the facility management network.
• LiftPC® database – for quality determination and statistical tracking of elevators, and for anonymous comparison with similar systems.
2/2005
