Corporate Buyers Guide

Laboratory furnaces are like industrial furnaces in every detail, except that they are smaller. This, actually gives them some advantages over their bigger cousins, such as better temperature uniformity and faster heat up and cool down rates.

Box Furnace..

The box furnace can be bench top size or floor mounted on a frame. The walls are thick because of the refractory insulation. For bench top use, the interior capacity is no more than one or two cu feet. Because of the small size, these box ovens have gravity air circulation.

The doors also require heavy insulation, this makes them heavy and bulky. A rising or vertical lift door is preferred for bench use. The vertical lift door has another advantage, as the door is opened, the hot side always faces away from the operator.

Muffle Furnace.

The same parameters that apply to box furnaces apply to muffle furnaces. The muffle furnace has a muffle on the inside separating the heating elements from the product being heated. This is important for two reasons, the vapors inside the muffle may be corrosive to the heating elements, or the very high temperatures of the heating elements may cause fire of the vapors released by the product in the furnace. Also, the muffle furnace has smooth walls and floor and is easy to keep clean.

Ashing Furnace

The ashing furnace is a box furnace with a venting system. The basic method is an opening in the top and one in the bottom of the furnace. This way the vapors emitted by the product can be removed by gravity venting. A fan at the top opening can control the rate of venting if this is required.

As stated previously, all L sealers use folded plastic film and heat sealing wires/blades which are arranged in an L shape. The product is placed between the folded sections of the film. The heated L is then brought down to seal across the film plus along the open side where the product was inserted. The seal across the film is wide enough and strong enough to separate the section containing the product and seal the film producing a sealed end for the next product insertion.

In a manual L sealer, the plastic film comes off a roll already folded and is pulled by hand over the sealing station. The first end has to be sealed from the previous sealing operation. The product is then placed between the sheets of film and the sealing L is brought down sealing the other end plus the opening where the product was inserted.

Sealing the end also separated the product package from the roll of film. The product package can now be pushed by hand into a heating tunnel to shrink the film.

A semi-automatic sealer requires that the product is placed into the film pocket by hand. The heating L bar is lowered by hand. When the bar is raised, the sealed package moves automatically to the end of the conveyor and the film advances in the sealing station ready for the next filling operation.

With an automatic L sealer, the shrink film with one end sealed lies in the sealing station. The product is brought by conveyor and is inserted into the film pocket with a push rod. The L sealer bar is lowered mechanically and is raised when the seal is completed. The sealed package is then moved ready for heat shrinking. With the automatic L sealer the feeding of the product at the input end plus the shrink tunnel at the output end have to carefully integrated for the process to operated without difficulty.