Getting a Handle on Power

Buying a hydraulic breaker doesn’t have to seem like buying a mattress. It is possible to know what’s inside.

While several factors come into play, there’s little doubt that the most common thing contractors want to know is how hard a breaker hits—or more scientifically, how much power or impact energy it can produce.

While one would think finding accurate impact energy information would be as simple as visiting a Web site or picking up a brochure, drawing accurate comparisons among breakers using the power ratings published on product literature is actually a far more difficult task than most people could ever imagine.

A typical breaker spec sheet will include a lot of straightforward vital stats—impact rate, working tool diameter, operating specifications, and a weight range of excavators or other carriers the breaker can be attached to, as well as some measure of the breaker’s power output. When these claims of power output are based on calculations or estimates, things get more complicated.

What unit of measure is used to describe impact energy? How is that number determined, and by whom? Is the data accurate? In 1991, questions like these led to the Association of Equipment Manufacturers (AEM) developing a universal testing system that finally gave consumers an objective standard for comparison among different hydraulic breakers. The dilemma of quantifying breaker power output was solved.

Unfortunately the AEM testing system may have worked too well and revealed a little too much, as now only a handful of breaker companies still publish such standardized impact energy ratings. For the last several years this has left, and continues to leave, buyers in a difficult predicament—seeing power specifications from different breaker manufacturers that appear to be based on the same measurement scale— foot-pounds—but are actually just one big pile of apples and oranges.

If the specifications don’t indicate an AEM-certified rating or are categorized as a foot-pound "class," then the figures are not really based on anything other than a manufacturer’s best estimates, and as we will see, these can vary wildly.

As previous generations will attest, things used to be simpler. Long before hydraulic breakers, workers used pneumatic-powered handheld breakers that were categorized by weight. A 90 foot-pound hammer weighed 90 pounds, a 60 foot-pound hammer weighed 60 pounds, and so on.

In 1963, Krupp Berco Bautechnik registered a patent on a hydraulic percussion mechanism. In 1966, the company produced the first hydraulic breaker in a series, and other players emerged. Taking the lead from their handheld predecessors, the power of most hydraulic breakers was categorized with a foot-pound number that roughly equated to the service weight. Therefore, a 1,000-pound hydraulic breaker was considered to have an impact energy output of about 1,000 foot-pounds.

Of course, weight is hardly a perfect measure—it makes no distinction between operating principle, efficiency or other factors that may influence performance from one breaker to the next. So as more companies began producing hydraulic breakers, manufacturers naturally began to try to separate themselves from the competition.

As technology advanced, manufacturers began introducing "new and improved" breakers, with claims that they could deliver more foot-pounds of impact energy than the unit’s actual weight in pounds. The inherent problem, however, was that the methods used to arrive at these measurements were unknown to anyone outside the companies publishing them. In fact, in some extreme cases, it even seemed that the numbers were being arbitrarily derived.

Without knowledge of the test procedures, there was literally no way for a neutral party to prove—or disprove—a breaker’s published power rating. The practical end result was that consumers were left to make decisions based on seemingly comparable foot-pound measurements that, in reality, were obtained from differing methods.

Recognizing the growing need for a standardized rating system, several manufacturers banded together through the Construction Industry Manufacturers Association (CIMA)—now the AEM—to form the Mounted Breaker Manufacturers Bureau (MBMB) in 1990.

One of the primary objectives of the MBMB was to establish a method for calculating breaker energy output that could be universally applied to all hydraulic breaker brands and sizes. Some manufacturers had previously used physics equations and formulas that were scientifically valid. However, information essential to making the calculations work could not be determined in many cases, and thus the equations were unable to generate truly accurate test results. The challenge for the MBMB was to come up with a standard that provided meaningful data that could later be replicated and confirmed.

Eventually the MBMB concluded that the most appropriate method for rating breakers was to measure the energy created at the breaker’s working tool, as opposed to energy levels at the piston or at the material being broken. The rationale was that this measurement would show how much energy the breaker was making available for actual breaking.

Next, a system for testing and measuring the energy was developed. The procedure itself involves a piece of test steel used in place of a normal working tool. This test tool is fitted with strain gauges that measure the shock waves produced through the tool during a test. Each breaker being tested is started and stopped 25 times to help ensure an accurate average. Using the readings from the strain gauges, the shock wave data is then calculated and converted into an impact energy rating measured in foot-pounds.

Before this test method was officially implemented, the MBMB proceeded to test a single breaker made by one manufacturer. Four separate manufacturers in four different countries performed independent tests, and all four achieved the same results. Based on this experiment, the method was confirmed as a reliable system for determining a breaker’s impact energy output.

Because different breaker brands and models use various levels of hydraulic oil flow and pressure, the testing procedure also requires that the actual tested pressure be within a small percentage of, and not greater than, the pressure specification published by the manufacturer. The exact conditions during the test—including blow frequency, oil flow, supply line pressure and return line pressure—are published alongside the AEM foot-pound rating. This allows the test to be replicated by any AEM-approved test facility. Additionally, to verify that each manufacturer is using the proper testing techniques to obtain accurate results, tests must be observed and certified by an independent AEM observer.

The development of the AEM test gave the hydraulic breaker industry what it sorely needed—a repeatable and documented test to serve as an accurate basis for comparing breaker power output. But with the standardized test came a new dilemma, as some manufacturers whose breakers tested poorly chose not to publish the numbers, but instead reverted back to estimated figures.

Some began to suggest that the test methodology was flawed, with the biggest objection being that the test does not indicate how a breaker will perform on an actual job site. This is true, given that impact energy is only one of several factors that determine how much material can be broken at the end of the day. The breaker’s carrier, the density of the material being broken, operating conditions and the carrier operator are also key factors on a site.

However, the AEM Tool Energy Rating was not designed to "rank" breakers. Rather, it was merely developed to put everyone on the same scale for determining power output, much like a tape measure does for length or a thermometer does for temperature.

Imagine hearing a meteorologist say it was 85 degrees Fahrenheit while another said it was 100 degrees Fahrenheit, all because one used a thermometer while the other said, "it felt like 100." Temperature alone won’t determine what you choose to do on a summer afternoon—other considerations might include rain in the forecast and having to deal with traffic—but it will have an influence. And because everyone knows what temperatures on the Fahrenheit scale mean, or feel like, they’re fully able to apply that knowledge to decisions.

No doubt manufacturers unhappy with their AEM ratings are fearful that customers will be swayed by power ratings alone, but most contractors are savvy enough to understand that they must apply additional knowledge to their purchase decisions. It’s possible that a hard-hitting breaker may not be built for longevity—striking a balance between physical size and power output is key to the reliability and useful life of a breaker. Perhaps another breaker has an attractive price tag, but the product’s lifespan or aftermarket support is poor.

AEM ratings don’t answer every question, but they do answer one—how hard does the breaker hit?

With several manufacturers abandoning the AEM ratings system, many breakers on the market have reverted to ratings based on previous methodologies or pure estimates that are also measured in foot-pounds. This obviously creates great potential for confusion in the market.

Therefore, it’s absolutely critical to point out that the foot-pound measurement from an AEM test should only be compared to other results specifically designated as AEM Certified Tool Energy Ratings. In other words, be certain to make an apples-to-apples comparison when looking at impact energy ratings described in foot-pound classes.

Customers should know that they can access AEM information and use it to make an educated decision. Even manufacturers who no longer publish standardized numbers should have the AEM test results for their breakers available if a customer requests to see them.

The importance placed on standardized impact energy data will vary from one contractor to the next. Many feel that all breakers are basically the same, and they might never encounter a demanding circumstance where true differences are revealed. Others may realize just how good or bad a choice they’ve made on the very first day the breaker hits a job.

In a perfect world, a contractor could run every breaker manufacturer through an audition process. While some contractors may have experienced the luxury of test-driving several breakers at once, this isn’t usually a realistic option. Ultimately, if a contractor can’t observe a breaker’s capabilities first hand, he must make an educated decision based on readily available information. Physical weight, hydraulic input and working tool diameter will be relatively similar when accurately comparing competing models.

No matter if the driving force in the purchase process is a breaker’s power rating or some other criteria, it’s vital to ensure the information you do have is truthful and accurate. Be diligent and obtain the necessary facts to make the best possible decision. C&DR