The HDE patented heaters are unique from other infrared heaters, consisting of a 16-gauge heater plenum, a patented replaceable heater cartridge, and a protective 16-gauge skirt. Heater panels are made up of any number of interconnected 4-foot (1.2m) or 3 ft (900 mm) long by 18 inch (450 mm) individual HDE heaters. The heater cartridge will develop surface temperatures of 1400-1500 F emitting high intensity radiant heat over a large area. Cartridge life is generally considered to be about 1500 to 2000 hours, which translates to a cost of about 7-8 cents per square foot per hour. At a charge out of $5.00/ SF for repair and figuring 3 heats per hour, the replacement cost of cartridges is about 1/2 % of revenue generated.
The propane gas is ignited inside the cartridge, heating up the entire outside ceramic surface to temperatures up to 1500°F within seconds. Infrared radiation is emitted from the surface area of the heater, making it the most powerful large size infrared heater on the market, emitting more infrared rays per square foot of heater area. The heaters can work at gas pressures ranging from 5 to 50 psi, giving varying intensities of infrared radiation. The heater plenum and skirt come with a 3-year warranty, the heater cartridge a 90-day warranty. The cartridge can be replaced in 20 minutes.
Individual heaters can be shut off to heat isolated areas. The heaters are at maximum effectiveness in seconds. The full infrared surface ensures fast penetrating infrared radiation, with no flame to overheat the asphalt surface. Many owners do not allow a flame application to pavement, since it will overheat the surface to temperatures above 270 F where the light oils begin to burn, and rely on heat transfer to depth by conduction. The higher operating pressures ensure easier lighting and no blow out in higher winds. The range of operating pressures can better suit varying job conditions. Besides the savings on propane tank filling, the design of the heaters ensure maximum temperature production with minimal energy input. The operating cost of the HDE heater is minimal since the propane usage is about 3/4 pound of propane per hour per square foot of heater deck on high intensity (1400F ) and 1/2 pound per hour on low heat. At a cost of .87 ¢ / gallon (21 ¢ / lb ) this translates to a cost of 15¢ / SF per hour . At 3 heats per hour $5.00 / SF revenue , this is 1 % of revenue.
The Propane Cylinder
The larger HDE Patchers and Joint Heaters are normally fueled by 100 lb. liquid draw propane cylinders. These are standard propane cylinders, but instead of the vapor being drawn off the top of the cylinder and fed to the heaters, the liquid is draw n from the bottom of the tank into a vaporizer. The mini heaters can operate using standard vapor draw 20, 30 or 40 pound propane tanks.
Even at very low operating temperatures, there is sufficient vapor at the top of the tank, to ensure that when the cylinder valve is o pe ned , the liquid is forced by pressure to the vaporizer and the heaters obtain sufficient gas to burn at maximum energy.
A 15′ x 6′ patcher can be operated on two 100 lb cylinders. On a standard working day of patching, only four 100 lb. cylinders are required, saving truck storage space. The liquid propane drawn from the bottom of the cylinder and converted into a gas through the vaporizer. A s a result, the cylinders can be completely emptied, reducing cylinder change time and providing cost savings, if buying full cylinders, rather than propane added on refill, and labor in cylinder changes.
HDE uses a vaporizer to ensure a consistent pressure of propane to the system without a freeze up of the cylinders at temperatures down to -15 F (-25C) The liquid propane which is drawn from the bottom of the LPG cylinders is heated in the vaporizer and converted to gas. Using a vaporizer empties the tanks completely without any “freeze up,” which is the most common problem among any vapor system. This happens because the heating system draws more vapor propane than the tank can naturally produce. The vaporizers are used on all joint heaters and all asphalt patchers larger than 36 square feet. The HDE mini heaters operate on 20 to 40 pound vapor draw cylinders.
In a normal vapor draw cylinder, the pressure coming out reduces as the cylinder empties, until the liquid propane in the tank stops vaporizing. The pressure difference is zero and the cylinder frosts up. A typical competitive 8 x 6 infrared heater which operates on vapor propane will require a minimum of 5 LPG cylinders for daily operation, whereas a 8’ x 6 ‘ HDE liquid draw system operate on one hundred pound tank and uses 2 for daily operation.
It is important to have constant pressure going to the heaters, to have uniform infrared radiation, for the complete workday, especially if heating in motion.The vaporizer also ensures empty cylinders, saving on minimum charges on volume fill-ups, and in general, considerable labor on changing and transporting cylinders.
The unique heater design allows us to run the heaters on a range of pressures from 10 psi to 60 psi.
The high pressure propane gas coming from the vaporizer is reduced in pressure and split into high and low pressure, so the heaters can be run at both high and low intensity. This can be done both electronically or manually. This helps in acheiving fast heat penetration in the initial 5 minutes of heating when operating in high pressure, the low pressure allows the less intense heat to keep the surface of the asphalt hot while the infrared rays are penetrating into the asphalt. Other heater designs actually shut the heaters off to prevent burning.
Instead of just an off/on switch, the HDE heaters have a high/low setting. The high and low settings can be adjusted according to site conditions.
A high setting can be used initially for shorter infrared wavelengths and quicker penetration into the asphalt. When the surface of the asphalt becomes very hot, the heater can be switched to a low heat, until the desired depth of penetration is reached. The higher operating pressures compared to conventional heaters, make blowers and batteries unnecessary.