Corporate Buyers Guide

Laboratory ovens are of the bench top type with a volume up to about 3 cu feet. Larger ovens up to 30 cu feet in volume sit on the floor or on a stand. They are called reach-in or cabinet ovens and are similar to industrial ovens.

The ovens have a maximum temperature of 300 C. The thermal insulation is usually rock wool or fiberglass. It is light weight, but makes a good insulator giving the ovens fast heat up and recovery times. To have uniform temperature throughout the oven the use of circulating fans is recommended.  Where a convection oven may have a temperature uniformity of +/- 3 C, with a circulating fan, the uniformity in the same chamber will be +/- 1 C.

The standard temperature controller is a temperature set point on/off control. This will give a temperature fluctuation of about 3 % of set point. Using a PID temperature controller reduces the fluctuation to ½ % of set point.

The inside of the ovens is stainless steel and for vacuum and inert atmosphere ovens is tightly sealed, but has tubes with fitting for external connections. These ovens have tight seals around the door.  

The normal laboratory ovens have a single door and room for 2 to 10 shelves depending on the oven volume. Most models only come with 1 or 2 shelves standard. More shelves are extra

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.