It’s no secret, at least within the industry, that most cranes of virtually all varieties have extraordinarily long working lives. The reason isn’t complex. Unlike earthmoving machinery, which wears itself out by engagement with and the moving of the earth, cranes spend most of the time waiting. And waiting and waiting.
Crane rental has increased utilisation, but cranes are rarely masters of their own domain. They cannot work without a load on the hook. So they waiting for materials to be delivered or dispatched, for obstructions to be moved so that they can reposition, wait for construction workers or machines to do their work before the crane can lift or lower their loads into place.
It’s no wonder that their carriers, crawlers or chassis see more wear and tear than the actual crane. For when cranes aren’t waiting they often traveling or being hauled from one job to another.
Structural design codes for cranes and the margin of safety built into structures haven’t changed much for decades. But, with tools like computer aided design (CAD) and finite element analysis, crane designers are now able to design with a precision that wasn’t possible 20 years ago. Now they can meet required codes, standards, and safety factors pretty much ‘on the nose’. Before this, without such precise knowledge of structures and their response to stresses, crane engineers would often err on the safe side, designing in extra strength.
Consequently, with reasonable maintenance and care, most cranes found in construction or materials handling activities can work for anything from 20 to 40 years. Without overload or damage, their steel structures should perform with little sign of strain.
Certainly hydraulics, electrics, and power train components will need repair and replacement, but the structure should be fine.
But how about installing sensitive measuring and computing equipment on a massive piece of lifting machinery and expecting it to function precisely and flawlessly with little scheduled maintenance? Asking a lot? Maybe. Well there’s more. Then let’s assume that the machine, its computer and instruments may well be in the hands of several, different, often relatively-untrained operators over the course of a year, or even a month. Hmm.
Then, of course, being a heavy construction machine, more than likely the entire machine will be left out in the weather, sometimes with the door and windows left open. Predictably, it will regularly, or even perpetually, be covered in dirt, dust, water, etc. Oh, and did we add that the machine is likely to have a working life of 25 or 30 years or even longer? And that’s in America or Europe.
A generation or two ago, the machinery in question was heavy gear wheels, chains, sprockets, and clutches and the only really sensitive piece of equipment was the engine and transmission. Hydraulics replaced the mechanical gear trains and although they leaked, in some ways the oil acted as a preservative. Then 30 years ago, electronics began to appear on construction machinery and all of a sudden reliability went out the window.
For a while there was a sustained crane user and operator backlash against the use of anything electrical on construction machinery. Indeed, for a long time, anything electronic was only tolerated where nothing else would do. And here, we encounter the famous or infamous ‘safe load indicator’, now know variously as a ‘rated capacity indicator’ or ‘load moment indicator’.
The first electronic safe load indicators were introduced in 1971. Pioneers included the British Company, Ekco Instruments Ltd., with its Ekco M7701 electronic safe load indicator, and the Japanese crane makers, Tadano, Kobelco, and Kato with devices produced in association with local electronics companies such as Hokushin. By this time, ‘safe load indicators’ (SLIs) were well known. Britain had been the first nation to mandate their use, in the 1930s.
By the 1970s, SLIs were mandatory in most of Europe, Australasia, South Africa, India, Japan, and several other countries. But before the 1970s, the safe load indicators were used primarily on mechanical lattice boom cranes and obtained their data inputs by essentially mechanical means such as dynamometers. Though not particularly accurate, limited in scope, a pain to calibrate and change configurations, at least they were quite reliable.
When announced, the apparent benefits of the new electronic instruments were quite enticing. Compared with the big clunky mechanical devices with their attendant boxes of cams, etc, that filled half the operator’s cab, the new electronic instruments were small and fitted neatly in front of the control levers. Unlike the mechanical devices, the new instruments could be recalibrated from one boom length to another with relative ease. Importantly, they looked modern, and they provided information that was more accurate and comprehensive.
Unfortunately, this was some 30 years ago, and electronics were not what they are now, and most of these instruments proved unreliable. Not only were their components unreliable, the boxes had poor seals against the environment, and most service mechanics had little or no knowledge of fixing anything electrical that was more complicated than a plug.
During the late 1970s and 1980s, companies such as Kruger and PAT of Germany, and the Japanese manufacturers began to incorporate microprocessors into their devices, which now, combining the input of several sensors including potentiometers, were able to read the ‘moment’ and thus ‘load moment’ of a crane. They were better, but still far from perfect and still, in terms of reliability, the most troublesome single component on a crane.
By now US crane manufacturers had accumulated substantial experience of the devices, chiefly through their export sales and overseas manufacturing efforts in Europe, Japan, and elsewhere. Indeed, Harnischfeger P&H began installing the ‘Load-Safe-T’ computerised safe load indicator as standard equipment on its 250USt capacity 6250-TC lattice truck crane as early as 1969 and Grove made the Kruger Mark IIA LMI standard on its largest telescopic truck cranes in 1981.
But, during this period, the ‘hands-on’ conservative culture of the US construction industry placed greater weight on the unreliability and loss of operator ‘control’ that they saw as implicit in these devices, than it did the apparent benefits. The crane standards committees of the American National Standards Institute (ANSI), heavily represented by trade unions and crane user and operator interests, reflected those views, regularly voting against any regulations mandating the use of such devices.
Beginning in 1987 with Grove, US crane manufacturers began to, so to speak, take the law into their own hands by installing Kruger, Morganite/Greer or PAT LMIs as standard on their crane lines. But despite elaborate training and orientation, these programs often encountered resistance. Long memories meant that many crane operators were set against the devices. Also, 15 to 20 years ago, electronics were not nearly as dependable as they are today and virtually always the single most troublesome component on a crane and the highest-cost warranty item.
But the engineering leadership of the German crane industry was gaining momentum, and in 1989, the introduction by Liebherr of its LICCON (LIebherr Computer Controlling) system, was another bold and revolutionary step forward. By 1992, Liebherr had extended its lead with the development of Work Planner software and program tele-diagnosis.
Then, in 1997, another giant advance saw the first mobile cranes – from Liebherr and Grove – with CAN-Bus systems. Now, electronic sensors and computers were monitoring and sometimes managing a broad range of machine components and functions. The bar was raised significantly again in 2001 when Demag introduced its IC-1 system featuring a VDU screen, touch screen control interface, an optional overload recorder with a CAN-Bus based crane system.
Thanks to the computer and domestic electronics revolution of the past decade, most everyone is now far more comfortable with such devices than they were just a few short years ago. Today, most crane operators have computers in their homes and cell phones in their pockets. And when it comes to cranes, buyers worldwide expect ‘wiz-bang’ electronics in their new cranes.
But what about those 20 and 30 year old cranes that still inhabit the job sites of many parts of the world? Clearly, in markets such as Europe, Japan, and Australia when ‘older’ cranes come up for their periodic re-certification, their LMIs must be fully functional. But elsewhere? There are many countries where LMIs or load indicators are still not mandatory, and there are still some users and buyers that argue against them.
There are also a great many cranes in service which were originally equipped with LMIs of, shall we say, ‘earlier’ design vintages. PAT demonstrated its recognition of this with the introduction last year of their new ‘Maestro’ LMI. Aimed squarely at the retrofit market, the Maestro is claimed to be much more affordable than earlier retrofit offerings, not just in terms of hardware but in all the attendant costs. PAT’s idea is not to change-out the entire system, but to simply replace the old central computer unit of an LMI with the new, more affordable and reliable technology of the Maestro.
In this way, PAT claims that the ‘original’ load charts, etc. can be simply transferred over to the new computer and therefore eliminate the need for recalibration. With this approach, PAT claims that the whole job can generally be done within about half a day. Its primary target seems to be the ‘more than 10,000’ of its own LMIs that are 10 years old or greater ‘somewhere out there’.
This seems to be a good concept. PAT knows, as well as anyone, that the age-old problem of persuading crane owners (at least in the US) to invest in installing a new LMI in an older crane, often comes down to dollars. Until recently, crane owners looking to retrofit an LMI have been faced with what they perceived as being a relatively high cost for a new LMI system combined with the additional cost a lengthy installation and recalibration/testing program and lost earning time for the crane.
So just how big an issue worldwide is this? Clearly, virtually all new cranes of European, Japanese, Australian, Indian, or Russian origin that are still in service had some form of LMI or SLI as original equipment. The vast majority of rough terrain and telescopic truck cranes of US origin produced since 1993 had an LMI as original equipment. Before 1987, unless sold for first use in Europe or a market mandating LMIs, most cranes of US origin had no LMI system or similar. LMIs have been mandatory in China for well over 10 years and indeed both PAT and Robway of Australia have had local joint ventures in China since the early 1990s.
The question is how many of the systems installed in the 1970s, 1980s and 1990s are still properly functional? But the landscape is pretty vast. Table 1 shows my best estimate of the total working population of mobile cranes of 5t capacity and greater including hydraulic telescopic boom cranes (RTs, truck cranes, all terrains, crawlers, and industrials), lattice boom cranes (crawlers, truck cranes and wagon or self-propelled) and truck-mounted (boom trucks). We’ve stopped short of estimating cranes of over 30 years old, though these are still a factor:
The total number of cranes originally equipped with some form of LMI or load indicator includes some 140,000 produced in the former Soviet Union, China, India and certain developing nations.
Given the rigours of the environment in which cranes work, it might be argued that a relatively minor percentage of the systems installed more than 10 or at least 15 years ago might not be as accurate or as fully functional as they should be. Of course, some percentage of the cranes of older vintage have been retrofitted with replacement devices or had some remedial work done. But, I’d think that those would be distinctly in the minority.
