Fuel Efficiency Fact or Friction
In article two of this five part series, we will review how both power and fuel efficiency are affected by the design of the concrete pump. Specifically, this article focuses on the methods and path used to pump and place concrete.
SOURCES OF LOSS
When it comes to the systems on a concrete pump, power and fuel efficiency share the same goal: optimized operations. If the wrong parts are used, or not assembled or designed to work correctly, the result will be either a loss of power or an excessive use of fuel. These losses can be minimized by avoiding barriers in either the hydraulic oil or concrete delivery lines.
Friction is defined in engineering terms as the force that resists relative movement at the point of contact and is directly influenced by the pressure/force exerted perpendicular to the surface.
An increase in friction means the resistance to oil or concrete movement increases. In turn, this increases the power and fuel required to pump concrete.
WHAT IS YOUR GOAL?
If power is used to overcome friction in the hydraulic oil or concrete delivery lines, it generates heat in the oil or concrete and is not available for its desired primary function: pumping concrete. The fuel creating the power has thus been used inefficiently. There are several ways that friction robs the operator of both power and fuel:
- Hydraulic oil barriers – In every hydraulic system, there are components that will resist the flow of oil. A few examples: valves that redirect and disturb the flow, in-line orifice reducers that restrict and slow the flow, hoses that resist much more than smooth-walled pipe and excessively long or bending pipelines.
- Concrete delivery system barriers - What is true about the hydraulic system can also be said about the delivery lines. Every elbow redirects and distributes the flow of the concrete. Reducers restrict and change the concrete flow. Delivery hoses use up approximately three times as much power compared to delivery pipes. In addition, non-chromed material delivery cylinders in the pump cell are more difficult to pump through than chromed material delivery cylinders.
- Compounding effect - The greater the friction, the greater the pipeline pressure must be to overcome resistance. Increased pressure means increased force acting on the inner wall of the pipe. Any increase in pressure increases the frictional resistance and wastes more fuel.
HAVE JOB, WILL DELIVER
The question for all operator/owners remains the same: What was the intention of the manufacturer of your fleet when they designed and built it?
- Did they take care to minimize the barriers to flow?
- Is friction being prevented so as not to rob you of fuel and power?
- Can your pump achieve the distances required while still placing high volumes without making expensive changes or adding optional equipment?
If you are a Putzmeister customer, you know the answer to these questions is YES! Here are a few reasons why:
Free Flow Hydraulics
Free Flow Hydraulics (FFH), the name says it all. Putzmeister's simple closed-loop system is designed to allow hydraulic oil to flow freely; resulting in minimal heat, and as a result less fuel consumption.
Click diagram to enlarge
Putzmeister engineers removed the barriers seen in competitive systems, directing the hydraulic power right to where the work needs to be done. In addition, they made it the responsibility of the main pumps to direct the hydraulic oil flow. This allows the source of the oil flow to be the dispatcher and eliminates the need for the energy-wasting directional valves found in open loop systems.
In addition, the placement of each part in the assembly is designed to decrease the length of the hydraulic lines, especially where hoses need to be used. The diagram at right depicts the Putzmeister Closed Loop FFH system.
Boom Pump Design
Putzmeister boom pumps have been engineered with fewer elbows and reducers to allow for smooth concrete delivery. The less friction in the line, the less fuel wasted.
While designing placement lengths that satisfy both jobsite and operator needs, engineers have continuously minimized the number of pipeline elbows and reducers where friction is most active in reducing efficiency and increasing pressures. In addition, every Putzmeister pump is delivered with chrome-lined material delivery cylinders in the pump cell for the smoothest pumping possible.
REAL WORLD EXAMPLES
It has been shown that the Putzmeister Closed Loop FFH system decreases horsepower losses associated with wasted energy by about 38 hp as compared to some open-loop systems. In addition, every elbow in the concrete delivery line adds ½ hp to what is demanded of the engine. With diesel fuel's work output of about 50 hp-hours per gallon, it is obvious how the Putzmeister fuel savings can add up and leave more horsepower available for pumping.
- 30 minutes pre-trip routine
- 60 miles round trip (60 mph highway travel assumed for simplicity)
- 30 minutes set-up time
- 4 hour pour, 400 total cubic yards pumped (100 yd3/hr average)
- 4" slump pumpable concrete mix
- Requires 36m boom with 125mm pipe fully extended vertical
- 75 horizontal feet of 5" hose attached in building
- Using concrete boom pump mounted on a Mack MR688S AI-400 chassis
- 30 minute clean and stow
- 15 minute post-trip routine
Minimum job site savings = $13.68
(4 hr x 38 hp / 50 hp-hr/gal x $4.50/gal)
It should be noted that comparison testing for these fuel efficiency improvements in real world applications is very hard to do with any degree of certainty and accuracy. Even with the best controlled tests a significant margin of error will still exist. As an example, a Mack chassis is not considered "broken in" until it reaches 25,000 miles (approximately 500 hours of pumping). Fuel use during this time period is inconsistent and erratic and should never be used for comparison testing. By the time two test machines have reached that milestone, there are now other discrepancies to consider, including the history of use and the maintenance of the concrete boom pump.
Instead of running such tests and making claims based on them, Putzmeister America focuses its efforts on designing and building efficiency and performance into its concrete pumping equipment. We do this based on sound engineering practices and practical knowledge built up over decades of expertise.
