Cranes require regular maintenance for safer operation through the replacement of components that have reached their service life. However, components that have had little usage and do not require replacement may also be replaced as part of the maintenance operation because of the lack of data on the stress and load experienced by the critical parts that can conclude whether they are actually at the end of their service life.
In order to overcome this issue for reducing maintenance expenses, new cranes now come with monitoring systems that can measure and store the loads, time and stresses on key crane parts. Using these monitoring systems, crane operators can get alert messages when the crane reaches certain ‘milestones’ and can achieve a reduction of up to 75% in maintenance costs (figure 1).
Figure 1. Monitoring systems for cranes.
Several companies provide monitoring systems for older cranes, thus helping operators of older cranes to achieve reduction in maintenance expenses and failures. Strain gauged-based sensors like strain links and load pins are the crucial sensing element of these monitoring systems. They substitute pivot and clevis pins and facilitate crane operators to take measurements of the forces experienced at these crucial points over a long period of time. This, in turn, provides thorough details about the maintenance requirements of the crane.
Load cells are strain-gauge-based transducers, which are utilized for measuring tension, compression and load in a mechanical assembly.
Load pins are deployed into machines as direct alternatives for pivot or clevis pins, without modifying the mechanical structure being monitored.
Besides being used in cranes, load pins are also utilized in hoisting gear, elevators, floor conveyors, shackles, pivots, bearing blocks, brake anchors, chain, rope, offshore platforms, tankers, marine, cable laying equipment, winches, sea ploughs, submersible anchor, and boom trucks.
A load pin slightly deforms during the application of a force on to it, as shown in Figure 2. This force is then measured by strain gauges installed within the load pin. In order to obtain accurate and repeatable results, the load pin must be positioned in such a way that the strain gauges are at right angles to the force being applied to it. Moreover, it is essential to prevent the load pin from rotating. The strain gauges are innately protected from the environment as they are placed inside the load pin. This protection is optimized when the load pins are fixed with end caps sealed with an O-ring or welded end caps.
Figure 2. A load pin deforms slightly when a force is applied to the pin. Strain gages installed inside the load pin, measure this force.
Load pins require virtually zero maintenance even in relatively aggressive operating environment of a construction crane. They are offered in many different capacities, styles and output signals. HBM recently produced a load pin with a 0-10 V output and a wireless adapter for a crane monitoring system.
The wireless adapter enables the operator to position the load pins on the required areas of a crane, without worrying about routing cables.
Accuracy and repeatability are two key and beneficial prerequisites for applying load pins in crane monitoring purposes in order to ensure safety.
In terms of accuracy, load pins offered by HBM average better than 0.5% when compared to competitive products. Obtaining accurate and repeatable measurements allows operators to perform maintenance of crane only when required. This, in turn, will ensure safer operation and reduce maintenance costs.
Figure 3. Load pins offered by HBM.
Assessing the capability and expertise of a supplier is also an essential element of the load pin selection process for a crane monitoring system, because these products often need to be customized based on specific applications of customers. Moreover, price and delivery time are also need to be considered while evaluating a supplier. A more capable supplier can deliver cost-efficient components on time.
HBM recently worked with a crane monitoring system provider, which installs systems on existing cranes that do not have monitoring equipment.
The crane monitoring system provider was previously utilizing a load pin produced by another manufacturer. Unfortunately, that component was not able to produce the accurate and repeatable results required. Hence, the customer approached HBM to get a more accurate component for the same price. Since, HBM is one among the few makers of internal strain gauges, it was able to design and deliver the load pin within two weeks. Moreover, HBM was able to meet delivery dates without fail, as it produces load pins in the United States.
HBM also provided support to the crane monitoring system provider for integrating the load pin into its system. It also helped the customer with the wireless gateway and customized the design of the load pin for its easy connection with the wireless gateway.
The new crane monitoring system has demonstrated to be a successful product and is currently being used in over 20 cranes. The number is expected to reach 100 at the end of 2013. Each and every one of the systems is significantly reducing maintenance costs for their owners and operators. HBM is happy to be part of the success.
This information has been sourced, reviewed and adapted from materials provided by HBM, Inc.
For more information on this source, please visit HBM, Inc.