Hydraulic cylinder life prediction

Abstract

Maintenance requirements for hydraulic cylinders used to actuate heavy equipment may be predicted by measuring actual use of the cylinders. Sensors measuring piston position within each cylinder are interrogated and the results stored in histograms bins to provide a permanent record of motion. Hydraulic pressure and temperature are also recorded. Data are downloaded periodically and compared with data from laboratory tests and/or from other units in the

1 . A method for predicting service intervals for hydraulic systems on machinery using pressurized hydraulic fluid to actuate hydraulic cylinders for control functions comprising: 
 sensing the position of a piston in an hydraulic cylinder at intervals of time and recording the position of the piston as a function of time;    determining the direction of travel of said piston and calculating the distance traveled by said piston over a period of time;    calculating the acceleration and deceleration rates for said piston over each period of time corresponding to movement in a direction;    recording the acceleration;    sensing the pressure of the hydraulic fluid at intervals of time;    recording the sensed pressure of the fluid at each interval of time;    calculating the average, maximum and minimum pressure over all recorded intervals of time;    sensing the temperature of the hydraulic fluid at intervals of time;    recording the sensed temperature of the hydraulic fluid at said intervals of time;    collecting the recorded data for position, distance, acceleration, pressure and temperature; and    comparing the collected data to pre-established standards to determine the time for the next service.    
     
     
         2 . A method according to  claim 1  wherein the position of a piston is determined by use of a sensor device selected from the group consisting of rotary position sensors, magnetostrictive sensors, radiofrequency sensors, linear potentiometers, variable impedance transducers linear variable displacement transducers, and cable displacement transducers.  
     
     
         3 . A method according to  claim 1  wherein pressure is measured using a strain gauge.  
     
     
         4 . A method according to  claim 1  wherein temperature is measured using a device selected from the group consisting of thermocouples and thermisters.  
     
     
         5 . A method according to  claim 1  wherein data is collected and processed in a microprocessor.  
     
     
         6 . A method according to  claim 1  further comprising downloading the stored data to a portable recording device.  
     
     
         7 . A method according to  claim 1  further comprising downloading the stored data to a central location via satellite.  
     
     
         8 . A method according to  claim 1  further comprising display of data indicating excursions from desired ranges of pressure and temperature within an operator's work station.