How To Improvise Or Install Load Monitoring In A Crane

As you intend to do it the computing will be very complex since you measure pressure in a cylinder and stability is related to load. Load will always be vertical but the cylinder is in an angle with the boom and the length is along the boom which has a different angle with the horizontal.

The simplest solution is to monitor the tension in the cable measured at the dead end and as well the boom length as the boom angle. If you have those values the relationship is simple since you will know the load eccentricity (boom length x cos(boom angle)) and the load the product can be compared with the table data and generate a signal according to the value resulting from the computation.

For the load you can use force transducers of different types.

Keep it as simple as you can !

If you need further explanations ask even on direct mail.

You can get a battery a operated weighing device that goes between the hook and the load. The lift is then assessed using that and the crane's own SWL indicator.

Have you discussed the matter with the crane's manufacturer?

Without knowing the geometry or hardware of your crane, I cannot help you locate suitable devices to measure the lifted load. I do recommend that regardless of how you design your instrumentation that you test your instrumentation design with either a calibrated mass to lift or certified crane scale.

If you are trying to rehabilitate an old crane, it may not even be possible to incorporate all of these new automatic features onto an old beast.

I believe that this scope of work may have been the brainstorm of some young MBA in the client's organization with no practical crane experience.

Your best source of information is the original crane vendor.

Understand that incorporation of automatic safety features implies some liability too.

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This could be a very interesting problem. The most usual important quantity is the overturning moment involving weight at horizontal distance from mounting base of the crane, or wheelbase of the vehicle. With suitable arrangements, this could be measured with a single load cell.

However, there may also be other limiting factors such as cable tension, which can be measured as Crabtree describes.

A dimensioned drawing is essential in cases like this.

Only if the boom cannot rotate with respect to base

Why is that a problem? Envision the rotating base as a tripod, say with two vertices toward the boom, and the third vertex away from the boom, with a load cell.

Everybody thankyou for the replies. I am sorry for replying late as i was out of office for few days. I should have attached a pic of what i am discussing here. here is the wrecker truck i am talking about.

the wrecker crane is a two stage telescopic crane. the extracted length is 5.5m and retracted length is 3.5m .

here are the links of devices i am talking about.

LOAD Cell , Indicator , ANgle and length indicator , Overview of Full Scheme

I am mainly concerned about the pressure transducer and its implementation in the hydraulic cylinders. how is it calibrated?

The hydraulic pressure transducer is measuring and should display in your monitor the hydraulic oil pressure. IMHO The oil pressure should not need any more calibration than being sure the range is set properly. This device tells the operator indirectly if any fluid leaks are present. If a calibration is required of this part then the sensor manufacturer has the documentation how to do this.

The load cell is what tells the operator the calibrated mass that one is lifting. Depending on the design of the control system the load cell might report the cable tension instead of the load on the hook. Beside the factor of two difference, the only anticipated error will be the hook and extended cable mass difference.

A clever programmer with sound knowledge of the crane mechanics might be able to interlock parts of the crane operation to prevent dangerous operation.