Light Equipment: Handheld hydraulic breakers

For small demolition jobs that call for the maximum impact force, nothing equals the power of a hydraulically powered handheld breaker.

Different types of breakers have different strengths. Electric models do well on small projects, like busting up a section of sidewalk. Pneumatics are the best choice when you intend to run multiple breakers on a tow-behind compressor. But the best power-to-weight ratios come with hydraulics. A 70-pound hydraulic breaker delivers roughly the same impact energy as a 90-pound pneumatic breaker.

As with other types, hydraulic breakers are classified according to how much they weigh. As a general rule you use a 40-pound breaker on 4-inch thick concrete, a 60-pound breaker on 6-inch concrete and a 90-pound breaker on 9-inch concrete.

Power packs
The primary source of power for a hydraulic breaker is a hydraulic power pack. These gas-, diesel- or electric-powered machines are about the size of a portable jobsite generator and light enough for two people to load into a truck. Their hydraulic flow and pressure can be adjusted to match a variety of breaker sizes, and they keep the hydraulic fluid from overheating via cooling fans.

The Hydraulic Tool Manufacturers Association designates two standards for breakers and power packs. An HTMA Type I circuit has a flow of 5 gallons per minute. Type II circuits provide 8 gpm. Both call for pressures at the tool inlet of 2,000 psi and backpressures on the return side of 200 psi or less. Most power packs provide appropriate flows for both Type I and Type II tools, although for some specialized applications you can get power packs that are set up for only Type I or Type II circuits.

Tap your machine’s hydraulics
Hydraulic breakers are also sometimes powered by auxiliary hydraulic circuits in utility trucks or construction machines. Utility trucks typically have hydraulic circuits compatible with Type I and Type II tools. But skid steers and backhoes crank out more flow and pressure (typically 10 to 15 gpm and 3,000 psi) than a breaker can handle.

To reduce flow and pressure coming from a machine, breaker manufacturers provide an intermediary device that you plumb in between the machine’s auxiliary circuit and the breaker. Atlas Copco calls theirs an oil flow divider; Fairmont names it a flow adjustment valve. These restrict the flow of hydraulic oil coming from the machine and contain a pressure relief valve set to trip at 2,000 or 2,100 psi. Stanley’s solution is a more elaborate device called the Hydraverter which compensates for fluctuations in the host machine’s oil circuit and adjusts to deliver consistent output to the tool. It’s powered by the host machine’s oil flow but has its own oil reservoir and cooling system that don’t intermingle with the machine’s hydraulic circuit.

Most mobile construction equipment generates 300 to 350 psi back pressure at the oil return outlet, which is higher than desired for optimal performance of a handheld breaker. The simpler flow dividers and adjustment valves don’t alleviate this high back pressure. Most breakers are rugged enough to deal with it. But the lower the backpressure the better. Low backpressure allows the tools to run more efficiently and reduces heat added to the system and thus allows you to run the tool for longer periods of time. The HTMA recommends hydraulic systems have enough heat rejection capacity to limit the oil temperature to 140 degrees Fahrenheit. You can minimize backpressure by keeping the hydraulic system clean, using the correct viscosity oil and not using hoses longer than 25 feet.

Nitrogen accumulators
Hydraulic handheld breakers, like machine-mounted breakers, use a nitrogen gas charge as the primary energy source to fire the breaker. When released via a shuttle valve pressure from the nitrogen accumulator pushes the hydraulic oil and the striking piston downward to impact the tool. During the upstroke of the piston the nitrogen is recompressed and absorbs any energy not being used in the tool.

If the pressure in the nitrogen accumulator drops, the energy it normally absorbs will follow the path of least resistance to the hoses and whip them back and forth. This, or any reduction in performance, indicates that you need to recharge the accumulator. Breakers that see regular use may need recharging at the end of a season, but many go two seasons or more – some even as long as a decade – without needing a recharge.

Vibration and noise
Concern about prolonged exposure to vibration has led manufacturers to develop optional low-vibration models. These use springs to isolate and absorb some of the vibration traveling up the tool and into the handles.

Compared with pneumatic breakers, hydraulic breakers are considerably quieter. This makes them the preferred choice in urban settings or anywhere excessive noise is an issue. Pneumatic is still the most popular choice in the United States, but the reduced noise levels of hydraulic breakers have helped make them the standard in much of the rest of the world.

Maintenance and longevity
Maintenance on hydraulic breakers is simple. Rule number one: keep your hydraulic system clean. Most contamination enters through the couplers, so avoid dragging the hoses through the dirt and wipe off the faces of the couplers every time you connect them.

If you’re storing a breaker for the off season, use a chisel to push the piston into the raised position so it stays lubricated. If you use a power pack, don’t forget to change the oil and filters and perform routine maintenance on those as well.


The six-second rule
If it takes less than six seconds to break, whatever the material, then you’re using too big a breaker. If it takes more than 10 seconds, you’re using too small a breaker.

The hardness and thickness of the material will determine the best combination of impact energy and frequency. Concrete varies from as little as 3,000 psi for residential slabs to 12,000 psi or more for engineered structures. Concrete also continues to harden for decades.

For soft material, like granite or low-psi concrete, use a breaker with high frequency, low impact – faster hits but with less force. For hard, dense material you want low frequency, high impact – a breaker that hits slower, but harder.


Sources
Product experts interviewed for this article include:
Ron Axon, senior product manager, Greenlee, a Textron company.
Bruce Burton, product manager, handheld products, Stanley Hydraulic Tools.
Eudes Defoe, applications manager, hand held products, Atlas Copco Construction Tools.