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Comparing hydraulic breakers
Most demolition, utility or general contractors understand that while one hydraulic breaker can handle a given project, another may be needed for a different job. Usually what contractors are most interested to know is how hard a breaker hits ó or, more scientifically, how much impact energy it can produce.
A typical breaker spec sheet includes impact rate, working tool diameter, operating specifications and a weight range of appropriate carriers. But things can get complicated with power output claims that are often just based on estimates.
In 1991, the Association of Equipment Manufacturers (AEM) developed a testing system that provided an objective standard for comparing hydraulic breaker power output. But today only a handful of companies still publish standardized impact energy ratings. This has left buyers with power specs from different manufacturers that appear to be based on the same measurement scale ó foot-pounds ó but that are actually like comparing apples and oranges.
In 1966, Krupp Berco Bautechnik produced the first hydraulic breaker series, and other players soon followed. Back then, breaker power output was categorized with a foot-pound number that roughly equated to a modelís service weight. Of course, weight is not a perfect measure, as it makes no distinction between other factors that influence performance. So as more companies produced breakers, they tried to separate themselves from the competition.
Manufacturers introduced breakers claiming to deliver more foot-pounds of impact energy than the unitís weight in pounds. But measurement methods were unknown and at times it even seemed numbers were arbitrarily derived. Without knowledge of test procedures, neutral parties couldnít replicate a breakerís published power rating. Consumers were left to make decisions based on seemingly comparable measurements obtained from differing methods.
Several breaker manufacturers banded together through AEM to form the Mounted Breaker Manufacturers Bureau (MBMB) in 1990. The MBMB set out to establish a standard method for calculating breaker energy output that could be universally applied to all hydraulic breaker brands and sizes, while also providing meaningful data that could be replicated and confirmed.
The MBMB concluded the most appropriate method for rating breakers was measuring the energy created at the breakerís working tool, to show the power the breaker was making available for actual breaking. The test itself involves test steel fitted with strain gauges that measure the shock waves produced through the tool. Each tested breaker is started and stopped 25 times for an accurate average. The strain gauge shock wave data is then converted into an impact energy rating measured in foot-pounds.
Because breakers use varying levels of hydraulic oil flow and pressure, the procedure requires that the tested pressure be within a small percentage of, and not greater than, the manufacturerís published specification. The exact test conditions ó blow frequency, oil flow, supply-line pressure and return-line pressure ó are published alongside the AEM foot-pound rating so the test can be replicated. Tests must be certified by an independent AEM observer.
The AEM test gave the hydraulic breaker industry an accurate basis for comparing power output. But some manufacturers chose not to publish the numbers. Some objected that the test didnít demonstrate job site performance. This is true, given that the breakerís carrier, operator, operating conditions and material density are also key factors.
Although this objection is logical, it misses the point. The AEM Tool Energy Rating was not designed to ďrankĒ breakers. It just put everyone on the same power output scale, like a tape measure does for length or a thermometer does for temperature. AEM ratings donít answer every question, but they do answer one ó how hard does the breaker hit?
With several manufacturers abandoning the system, many have reverted to old methods or pure estimates also measured in foot-pounds, recreating the potential for confusion. To make an apples-to-apples comparison, an AEM foot-pound measurement should only be compared to specifically designated AEM Certified Tool Energy Ratings. Even manufacturers who donít publish their AEM numbers should have test results available upon request.
In a perfect world, a contractor could test-drive every breaker, but this isnít usually a realistic option. If a contractor canít observe a breaker firsthand, he must make an educated decision with available information. Whether itís a power rating or other criteria, itís vital to ensure the information you have is truthful and accurate. Be diligent and obtain facts to make a solid decision.