Rugged Inductive Sensor with Analog Output Measures Wear in Plain Bearings


Straddle carriers, purpose-designed container-handling vehicles, operate in highly aggressive seaport environments, necessitating frequent preventative maintenance. To measure wear in components with a high risk of premature failure, European port operators use rugged, analog-output inductive sensors. Monitoring the condition and wear rate of each component enables predictive maintenance to be undertaken only when necessary, maximizing vehicle utilization and reducing maintenance costs.

Customer Values

  • Maximum vehicle utilization with fewer constraints on operations
  • Real-time indication of bearing condition and wear rate
  • Reduced maintenance costs with minimal incidence of breakdowns
  • Reliable operation in a highly demanding and harsh environment

Specific Product Advantages

  • Analog device with extended 40mm sensing range
  • Small physical size (less than 50mm length)
  • Exceptional accuracy and resolution in the micron range

Customer Application

A fleet of straddle carriers services a busy German container port, operating round the clock in a highly aggressive environment. Frequent maintenance is necessary, but traditional, interval-based maintenance schedules are not always optimal. Condition-based intervention minimizes the risk of breakdowns, while imposing fewer constraints on day-to-day operation; it also incurs cost only when necessary.

As a carrier moves over a container, a central spreader beam lowers and locks onto the four corner fittings of the container. Plain plastic bearings on the carrier legs guide the container as it is raised; there is significant contamination from dirt and other debris. Bearings wear rapidly in the all-weather operating conditions.

A condition-monitoring system must measure bearing thickness, repeatably and accurately, in real time and with µm resolution. Sensors must operate reliably in the harsh environment with a minimum rating of IP67. Sensor length must not exceed 70mm and a minimum sensing range of 30mm is mandatory.

Customer Solution

Contrinex inductive sensors from the Analog Output range with Extra Distance technology are ideal for this demanding application. These M30-diameter metal-bodied devices are IP67-rated and provide an analog voltage (0- to 10-volt) or current (4- to 20-mA) output. The sensors are less than 50mm long with a 40mm sensing range, comfortably exceeding the specified requirement.

A mild steel mounting plate, fixed immediately behind the plastic bearing, locates each sensor with its sensing face in contact with the rear surface of the bearing. As a container passes over the front face of the bearing, the sensor measures the distance to the metal container wall, and thus the bearing thickness. Data is collected in real time with exceptional accuracy and resolution in the micron range.

Data passes to on-board computers mounted on each carrier; connection is via a flexible cable with an easily detachable M12 connector. At intervals, carriers transmit data wirelessly to a central processor for detailed analysis.

The output gives a clear indication of the condition and wear rate of each bearing, identifying any carrier requiring maintenance. Consequently, the port operator has the means to develop a genuine commercial advantage by eliminating compromise from day-to-day operating processes.