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Method and apparatus for determining stress on hoisting equipment
| Details |
Inventors: Hasselmann, Heinz; Muenzebrock, Anton;
Assignee: Mannesmann Aktiengesellschaft (Dusseldorf, DE)
Primary Examiner: Wise; Edward J.
Assistant Examiner: Teska; Kevin J.
Attorney, Agent or Firm: Mandeville & Schweitzer
The disclosure is directed to a method and apparatus for determining the cumulative load stress on hoisting equipment. Generally, the apparatus according to the invention comprises a system of electronic components operable to measure and indicate the cumulative load stress handled by a particular hoisting installation. The apparatus includes a time signal generator, generating a series of constant time interval electrical signals, first electrical conductor means, selectively operable to conduct an electrical signal indicating operation of the hoisting equipment and a second electrical conductor means selectively operable to conduct an electrical signal corresponding to the value of the load being handled by the hoisting equipment. First and second circuit means are electrically associated with the time signal generator and first and second electrical conductor means. The circuit means are operated to calculate the cube of the value corresponding to the load during the time interval of each particular one of the series of constant time interval electrical signals generated by the time signal generator during the operation of the hoisting equipment. Electrical adding and storage means and electrical comparator means are electrically connected to the circuit means and are operable to determine the sum of all the cube values formulated by the circuit means and to compare the sum with a predetermined maximum value. The comparator means is arranged to actuate an indicator means when there is a predetermined relationship between the sum stored in the electrical adding and storage means and the predetermined maximum value. |
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DETAILED DESCRIPTION The invention is directed to a method and apparatus for determining the cumulative load stress on hoisting equipment, under consideration of various types of load stress.
Hoisting installations are described and classified in such a way, pursuant to the agreements and guidelines of the Federation Europeanne de la Manunetion (European Federation of Conveyor Technology, hereinafter, the FEM) that, for an intended application, a known life expectancy for the equipment, expressed in years, may be expected.
To this end, the hoisting installations are divided into six groups, according to certain operating conditions known to effect equipment life expectancy.
These operating conditions are 1.
The mean running time per day, and 2.
The cube of the mean value of the cumulative load.
In choosing a hoisting installation, values for both these magnitudes are assumed.
The point here is to know as accurately as possible both of these values for the specific case of application.
In a known comparable individual case of a hoisting installation, the running time may be determined somewhat reliably by timing with the aid of a service-hour meter.
The cube of the mean value of the cumulative load, however, which is a time-dependent as well as a load-dependent magnitude, may be approximated only by gross estimates of the prevailing number of cases of application.
The FEM (Section IX) has issued the following formula for calculating the cube of the mean value of the stress from the cumulative load: ##EQU1## wherein: ##EQU2## In order to economize on the expenditures involved in the calculation of K, it is customary to divide the cumulative load into a limited number of load categories for which the relative running period for each category is then determined.
This measuring process is, however, technically very expensive and not suitable for continuous monitoring of the hoisting installation during operation.
The classification of the hoisting equipment, in view of the cube of the mean value of the cumulative load, is based on the premise that the life time of the individual building elements depends on the value of the load cubed
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