Helpline provides Process Heating's readers with a chance to solve problems that crop up in heat processing applications.

I am trying to heat 0.75 to 3" (20 to 75 mm) dia. cylindrical copper or stainless steel objects in vacuum. I will require relatively low power so I can operate a heater below its normal specifications. What should I do? -- W.F.

You may want to wrap a small diameter (1 mm) MI cable around the cylinder. Because vacuum is an excellent insulator, I also would recommend brazing the cable to the cylinder, but at lower wattage levels, this may not be necessary. To eliminate outgassing, electrical connections can be made outside the chamber via Swagelok fittings. -- James Brim, Thermocoax, (678) 947-4669.