Heating Up Underground "During the first few days, we saw (the Sahara Air Heater) haise our ambient temperature 4 or 5 degrees higher than previous projects"   Heating Up Underground GRAND RAPIDS, Mich. – Winter construction is a difficult undertaking, no matter what the job. Cold temperatures are tough on the site and the equipment, and frigid weather isn’t easy on the crew either. But taking on a below-ground public works project in the middle of a Michigan winter is even more of a challenge. Built in 1940, an underground drinking water reservoir for the city of Grand Rapids, Mich., was in need of repairs. While the reservoir’s two water tanks were generally in excellent condition, the material in the expansion joints had begun to deteriorate due to age and the tanks required a new coat of sealer. If repairs were not made, the tanks could start leaking water, or, even worse, ground water could seep in and contaminate the drinking water. The city of Grand Rapids looked to Rahm Industrial Services to take on the task. In business for 14 years and located in Grand Rapids, Rahm Industrial specializes in concrete restoration, making the firm an ideal choice for the job. Additionally, Rahm Industrial was familiar with the reservoir repair process, having completed maintenance work on another Grand Rapids underground water tank the previous year.   Dave Pylman Project Manager, Rahm Industrial   As with most jobs, a tight schedule was the biggest challenge. But before the crew from Rahm Industrial could enter the work area, an asbestos abatement contractor had to first take out any material in the expansion joints that tested positive for asbestos. With the hazardous material removal complete, Rahm Industrial began work on the first of the two tanks on January 12, 2005, with a target to complete both tanks by June 1, 2005. The city of Grand Rapids requires both tanks to be full by the deadline to be prepared for summer water needs. Of course, in order to begin the job, the water tank had to be dry enough to allow the crew to do their work. Excess moisture also had to be eliminated for the newly applied concrete to cure and protective sealer to set. On a strict schedule, Rahm Industrial needed equipment that would accomplish multiple tasks. Ground Heaters, Inc.’s newest product fit the bill. The Sahara Air Heater, first introduced two years ago, utilizes a trailer-mounted hydronic heater to heat a propylene glycol-based fluid that is then pumped through a series of hoses. But instead of relying on this system alone to distribute the heat, the hoses are connected to liquid-to-air heat exchangers. Placed throughout an enclosed workspace, each heat exchanger’s fan draws cooler air from the area and blows it across heated coils to produce hot, dry clean air. The fluid then returns to the main unit for re-heating. Rahm Industrial had rented an air heater for similar jobs in the past, but found it didn’t perform as well as expected. The unit wasn’t as efficient or reliable as hoped. In fact, the company had to call service technicians out to a job site several times to fix a recurring problem. These issues led Rahm Industrial to consider purchasing an air heater that better fit the company’s needs. .   “We checked out a couple of major manufacturers, and the Sahara Air Heater was the one we liked the best,” said Dave Pylman, project manager for Rahm Industrial. “We went out and looked at it at Ground Heaters’ headquarters in Spring Lake, Mich., and we definitely felt like this was the one that fit our needs.” After purchasing the unit, Rahm Industrial’s first test for the heater was the underground reservoir. The crew applied the Sahara Air Heater’s five heat exchangers (the company purchased one additional heat exchanger to complement the four that come standard with the heater) throughout the reservoir’s work area and saw dramatic results. “During the first few days, we saw [the Sahara Air Heater] raise our ambient temperatures 4 or 5 degrees higher than previous projects,” said Pylman. “Having the newer, more efficient model helped get our temperature to where we needed it.” Working on eight million gallon tanks that hold 15 percent of Grand Rapids’ drinking water supply posed obstacles as well. Only food-grade chemicals could be used in the tanks to ensure the drinking water was safe for human consumption. The Sahara Air Heater’s food-grade glycol was ideal for this job, as this heating fluid met the necessary public health requirements. Pylman said that using a heater with another kind of heating solution “would have made the job longer.” The confined workspace, 22 feet below ground, also raised concerns. “We need a top man who stays by the access hole all day, recording who goes in and out and monitoring the air quality,” said Pylman. “We parked the unit [by the access hole] to get the hoses inside the tank as soon as possible so they wouldn’t travel through the cold air and cool off,” he said. “I thought it would be kind of loud right next to the hole, but I was pleasantly surprised. It’s very non-obtrusive and very quiet. You can stand there and talk right next to it.” .   "It's probably 20 percent more efficient than what we've used in the past." said Pylman.  "We're definitely getting more heat out of this unit than (other products)" Pylman and his crew didn’t need to worry about air quality, either. Since the Sahara Air Heater’s self-contained heating system doesn’t introduce open flame or combustion by-products into the workspace, Rahm Industrial didn’t need to provide ventilation. Cost-effectiveness was also another benefit for Rahm Industrial. “Looking at the cost of renting versus ownership, it makes sense to invest in one,” said Pylman. “It’s probably 20 percent more efficient than what we’ve used in the past.” Not only was the Sahara Air Heater more efficient, but it produced higher temperatures than other products Rahm Industrial has used in the past. “We’re definitely getting more heat out of this unit than [other products], probably as much as 15 or 20 percent,” said Pylman. This increase in heat output has helped Rahm Industrial move the project forward. The first tank has been completed and the second tank is on track to be finished on time. The company’s outstanding work will hopefully lead to a contract to repair Grand Rapids’ remaining underground reservoir. “We did a good job on the first [tank], so we’re back again for this job,” said Pylman. “We feel like we’ll be the ones on the last tank.” And where Rahm Industrial goes, the Sahara Air Heater is sure to follow. After proving to be efficient, reliable and effective, the company is already discussing what challenging job the heater will be applied to next. “The heater was a good purchase,” said Pylman. “We’re looking forward to using it again.” The crew used five heat exchangers with the main unit, positioning them throughout the reservoir's work area.  The results were dramatic.     Go to Ground Heaters Air Heater's Products Page Go Back to the Job Studies Page