Important Industrial Oven Features FAQ
Top features to consider for your next laboratory oven purchase
Airflow –Sounds pretty basic, doesn’t it? Airflow affects a number of things:
- How efficiently you will heat your load.
- How fast you will recover heat after a door opens as you take parts in and out. and
- Airflow also influences the temperature uniformity you can expect.
Once we understand what samples you are heating, we can determine the right oven type with the correct airflow pattern so your materials are evenly heated in every batch.
Temperature – Depending on your application (drying, curing, bake-out, etc.) your temperature needs may vary. Temperature uniformity is just as important. Temperature uniformity depends on a combination of factors, including type of circulation and also insulation levels.
Temperature Uniformity, Uniform Zone, and Capacity – What temperature uniformity do you need? Uniformity is largely a function of airflow. If airflow is managed properly, the air temperature uniformity throughout the chamber will be tight, assuming you don’t block the airflow completely with your load.
Most oven manufacturers will state the oven zone in which uniformity can be expected, i.e. to within what distance of the walls, ceiling, and floor. This defines the “uniform zone”. For example, + 10F at 300F, you can expect the readings you get during a survey to be 290F to 310F throughout the uniform zone.
Capacity – Once you determine how large your uniform zone must be, you can clearly choose an oven with the appropriate capacity. EPS alone carries more than 20 different capacity laboratory ovens. We don’t want you to end up paying for more oven than you need.
Other Oven features – These include things like shelving design and temperature controllers. Will you need to ramp up and hold your temperature, or will your application require multiple temperature set points and holds during a cycle?
Control –The simpler your operation the simpler the controls should be. Let’s go from one extreme to another. If you are leaving the temperature in the unit at one point all day, and taking your parts in and out, several times a shift: a single set point controller will suffice. Pair this with a door switch that shuts down the heat and circulation when the door is open for loading and unloading: this guarantees simple and safe operation.
At the other end of the spectrum, an application that needs composite curing requires:
- Ramping the temperature up and down at a controlled rate
• Acquiring data from vacuum transducers and parts’ thermocouples
• Recording the data to your computer for archiving and print outs.
This operation will require a graphical human-machine interface (HMI) and a PLC (programmable logic controller). Complex applications use programmable controllers that will allow the cycle to run automatically, ramping up, holding, cooling down, and shutting off.
PLC (programmable logic controller) –In early years, all actions—turning heaters on or off, processing an alarm condition, activating an exhaust blower to cool the unit, etc.—were accomplished using relays.
PLCs aren’t used in small lab ovens or even in many small industrial oven units where the operating logic is simple. The more complex the operating parameters the better the case can be for a PLC. Lights on the PLC can indicate the source of a malfunction for easier dianostics.
The PLC is a black-box that takes the place of all the relays. The box can be “programmed” with what is called “ladder logic.” On one side of the “ladder” (which essentially was what a PLC program schematic looked like) is a vertical line, representing the inputs. The line on the opposite side represents the outputs. The “rungs” in between the two were the transmitters between the two. You could set this up so that the number of inputs (power switch on, limits satisfied, etc.) had to be on before the “rung” would tell the output to be active. This output could allow the heaters to be energized or the blowers to come on at specific set points.
Gas or Electric –Lastly, let’s talk about whether a unit should be heated by gas or electricity. We will initially determine the expected power usage during an average operating day and use the local utility rates to compare costs. Another factor to consider is the size of the unit. On a smaller unit, electricity may be the way to go: this avoids a potentially more expensive gas system. Gas systems also will require more maintenance, another consideration.
On very large units, the cost of the gas system will pale in comparison to the very expensive components (relays, breakers, SCR’s wire sizes, etc.) needed to maintain sufficient electrical power.