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.
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 (-25 C) 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.
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.
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 achieving 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.