Applications: Bolt heaters rapidly heat large
holding bolts to produce shrink-fit tightness upon cooling.
Expansion of tie rods and large studs for steam generators,
compressors, heavy presses, turbines, and pressure vessels
permits uniform tightening of all parts. When inserted
into hollow bolts, the heater expands the bolt and it can be further tightened. Cooling and ultimate contraction draws the bolt even tighter.
Construction: Various diameter high watt density Firebrand cartridge heaters are mounted to a 4" octagonal terminal and are equipped with a wooden handle for easy insertion and removal. Knockouts on the side of the box permit direct wiring to the power supply. A three conductor cord with electrical plug are optional features. Special lengths and diameters are available upon request. Stainless steel sheath provides efficient heat transfer inside the bolt. Uniform heating gives fast response in close tolerance fit holes.Caution Note:
Never operate bolt heaters in open air at their full rated voltage. Energizing heaters at half of their rated voltage to ward of moisture is acceptable. Caution must be taken to avoid contact with the sheath, as surface temperatures of over 500 degrees F can easily be reached even at half voltage. On-off cycling of the heaters can reduce their life. Heaters should not be left on for intervals beyond 30 minutes.
Standard units are single phase. Three phase is available on .813 and larger diameters. Close tolerance fit in the bolt hole makes for longer heater life. Clearance between hole and heater should not be more thatn .066 or less than .030 for ease of removal.
The heaters are designed with high watt density and with anticipated loss of heater life as a result of high heat density. Optimum performance is obtained if the bolt hole diameter does not exceed the heater diameter by more than 1/32 inch.
