Haines & Kibblehouse Drives Down Liquid Asphalt and RAP Crushing Costs
With the price of crude oil skyrocketing over the past three years, everyone has felt the crunch. The high price of asphalt cement (which contains oil) has also hit asphalt producers and paving contractors hard. From early 1999 to the present, the price of liquid asphalt has more than doubled in many areas throughout North America . According to Jerry Rush, maintenance superintendent for Mid-Atlantic regional paving contractor Haines & Kibblehouse (H&K), “In 2000 we paid between $70 and $80 per ton (for asphalt cement), but now the price of liquid asphalt is between $140 and $150 per ton.” With this dramatic increase in liquid asphalt costs, H&K is producing as much RAP as possible in its mix designs to help offset the cost of making virgin asphalt.
Established in 1968, the Skippack, Pennsylvania-based H&K employs approximately 1,500 people and provides construction aggregates and materials, asphalt paving materials, and site construction and demolition services from 50 locations throughout eastern Pennsylvania, New Jersey, Delaware, and Maryland . Its 15 asphalt plants serve a market area consisting of eastern Pennsylvania, parts of Delaware, and New Jersey — with about 50% of the asphalt produced going towards H&K's own paving projects and the other 50% supplying local paving contractors.
H&K Replaces Hammermills with Impactors, and Costs Drop
The key to H&K's success is keeping costs down, according to Rush. This is the reason it is running at least 15% recycled asphalt in about 95% of its current mix designs — the exception being 1/4" topcoat mixes. By running a reasonably high percentage of RAP, H&K saves considerably on production costs. Not only does the company use less virgin aggregate, but it also uses far less liquid asphalt. That is why you will find an asphalt crushing/recycling system at each of the 15 asphalt plants H&K operates.
H&K was one of the first producers in the region to start recycling asphalt. According to Rush, “We installed our first RAP system around 1973.” Since then, H&K has used everything from hammermills to roll crushers to process its RAP. However, a recent change in the company's RAP crushing requirements called attention to the inefficiencies of its existing crushing system.
Originally, H&K was using 1" minus RAP, but it could only be run in the company's base mixes. However, with the incentive to significantly reduce costs, H&K started crushing RAP to 1/2" minus so it could be used in all of the mixes, excluding topcoat. That's when H&K's problems became quite clear. Rush explains, “When you start taking it [RAP] down from 1" to 1/2", that's what separates the men from the boys.” (See below: “Why 1/2” Minus RAP Caused Excess Wear”).
With its hammermills and roll crushers, H&K was getting an increased amount of product returned to the crusher for further reduction. This posed a number of problems. First, screening efficiency suffered severely, since the old crushers were struggling to get even 60% of the RAP material passing through the first time. Second, increasing the number of times the recycled asphalt is cycled through the crusher diminishes the quality of the product. “With the hammermills, the RAP goes through the circuit four or five times and it looks like clean stone. It has all the tar knocked off it,” Jerry explains. “When you knock off the tar, you have to re-coat the rock with liquid asphalt, and you're defeating the primary purpose of running RAP.”
After exploring several alternatives to its current crushing equipment — even considering trying larger screens to handle the increase in oversized materials — H&K decided to test an Eagle Crusher UltraMax® 04 (UM04) stationary impact crusher. The UM04 uses the industry's heaviest solid-steel, 3-bar rotor design to efficiently crush recycled asphalt. Its 3-stage crushing action produces a consistent, uniform cubical product. As most highway contractors know, failure to meet asphalt specs can cost thousands of dollars per day in fines and penalties. The UM04 achieves reduction ratios of 24:1 and delivers production capacities up to 100 TPH. A manually adjustable primary apron and hydraulically adjustable secondary apron allow for precise product gradation control, and the UM04's blow bars, aprons, and liners are designed for long wear life.
The Eagle Crusher stationary UM04s employed thus far have greatly improved H&K's RAP crushing efficiency and produced a better product. Rush estimates that the impactors are running a far higher percentage of material through the crusher on the first pass. “With the impactors, the material goes through one time, and I [would] say that 90% is crushed the first trip. It has less of a tendency to knock the tar off the stone,” commented Rush. And with the tar being left on the stone, there is no need to re-coat the stone with liquid asphalt. This saves H&K a considerable amount of money.
The End to Building Hammers and Grates
H&K had experienced a dramatic increase in wear and maintenance costs on their hammermills when taking RAP down to 1/2" minus final product. This was a major concern for Rush, since H&K expects a RAP system to require very little attention. “You've got to turn it on in the morning and have it run all day long without any problems or backups. You must keep up production. The crusher has got to be almost trouble-free, and that is what we are looking for in a RAP system,” explains Rush.
Unfortunately, H&K's hammermills were requiring more attention than the company's far more complicated asphalt plants. As Jeff Clark, quarry foreman of H&K's Locust Ridge Quarry, explains, “We had to shut down our circuit every four days to change the hammers and rebuild the grates.” It took them about four days to rebuild a set of hammers and grates, so they had several sets on hand to rotate into the crusher. Ron Granteed, who is in charge of maintenance at H&K's Dunmore Materials plant, agrees with Clark, stating, “When you think about all the time it takes to hard face all the grates and hammers itself, it wasn't worth it.” All the maintenance H&K had to perform on its old crushers was costing the company money.
So Rush kept track of all the maintenance records of the old crushers for a year and compared them with the projected maintenance costs for the Eagle Crusher UM04 impactor. When taking into account all the downtime and wear parts with the existing hammermills alone, he concluded that it cost between $.50 to several dollars per ton to process the company's RAP. The projected costs with the UM04 would be less than $.10 per ton. Rush concluded that with the reduction in required maintenance alone, each impactor would pay for itself in a single paving season.
After compiling this information, Rush presented his findings to management. He said that switching to the Eagle Crusher impactors “was a no-brainer.” It didn't take too much convincing after that. “If you have it down in black and white, and you can document everything, then that gets their attention.” Rush's findings definitely got the attention of upper management, and his analysis was the deciding factor in switching over to the Eagle Crusher UM04 impactors. H&K is currently switching out all of its old crushers and going with the UM04 impactors.
H&K's maintenance has been reduced to routine lubrication, occasional adjusting of the aprons to keep the right tolerances, and rotating or replacing the blow bars. The company is currently crushing approximately 20,000 tons of RAP per set of blow bars, 10,000 tons per side. To this, Granteed exclaims, “Our blow bars last about six months, which is fantastic!” With the hammermills, H&K was only processing about 1,200 tons per set of hammers and grates before they needed to be rebuilt. Now, when it becomes necessary for a set of blow bars to be changed, Clark comments, “It's a piece of cake. It couldn't get any easier.” It takes approximately two men one and a half hours to change a set of blow bars — and then they are up and running again.
Increase Your Tonnage While Lowering Your Maintenance Costs
When H&K started to grind its RAP to 1/2" minus, the company noticed a big wear problem with the hammermills. Rush explains his reason for changing to the smaller size RAP: “It heats up a lot quicker and makes a nicer mix all the way around.”
Not to mention the fact that the smaller sized product can be used in 95% of H&K's mixes. A large portion of the millings the company was receiving was from base material, and most of the virgin aggregate in this base material was over 1/2" in size. The hammermills did not handle the aggregate very well. When they were crushing RAP to only 1", they were just breaking apart the asphalt — not actually crushing the aggregate present in the asphalt.
When H&K went searching for a crusher to replace its hammermills and roll crushers, it wanted something that was designed to crush the oversized virgin aggregate that was in the RAP as well as to break apart the asphalt. With the Eagle Crusher UM04 impactor, H&K got a crusher that had not only been proven in various aggregate applications, but had also been proven in thousands of concrete recycle applications, efficiently crushing large chunks of heavily reinforced concrete into a saleable product.
Rush recalls, “The pricing was right, and we tried a unit (the Eagle Crusher UM04) out. It worked really well, and we are happy with it. Once you find something that works, you stick with it.” Clark agrees with Rush, saying, “It does what it is supposed to do.”
Automation Further Reduces Costs
Since the installation of its first RAP crushing system, H&K has always had an automated circuit. The circuit is turned on in the morning, and from then on it is computer controlled. The 1/2" minus RAP is stored in a 2.5-ton surge bin, and a feed conveyor transports material to the asphalt drum mixer when the computer indicates a need for it. When the RAP level in the surge bin falls below approximately one ton, the computer starts the feed conveyor from the receiving hopper to deliver the feed material into the UM04 impactor. Material discharged from the impactor is transported via a discharge conveyor to a double-deck inclined screen with a 1.5" top deck and a 5/8" bottom deck screen. Any oversized material is then fed back into the impactor for further resizing. When the RAP level in the surge bin reaches 2.5 tons, the computer automatically shuts off the feed conveyor to the impactor.
H&K reports that it saves extra handling time and money by taking millings from road projects, stockpiling them, and then loading them directly on the receiving hopper grizzly. According to Rush, “We do this so we can pay attention to making the best possible mix, and that is where the money is.” H&K's goal is to operate a plant with as few people as possible. If H&K can get the RAP system to where it is virtually maintenance-free and everything is automated, then one man could easily operate the plant.
When asked if the Eagle Crusher UM04 impactor had helped H&K save anything besides time and money, Rush immediately replied, “Yeah — our sanity! Because we don't like digging out those other crushers when they jam up. Any one of the plants that had one of the old hammermills and now have one of these [UM04 impactors] in there — they are happy with them. And you have everyone else [at H&K] that are currently running the hammermills begging to get an impactor.”