Industrial environments come in every imaginable configuration. All of them must be kept safe from fire and explosion, but most do not need any special steps taken to achieve this goal. But others, by the nature of what they manufacture and how they do so, have special regulations to keep them safe.
Dangerous situations can occur where there are flammable gases, such as propane. Vapors from solvents can also present hazards. High levels of dust particles in the air can also be highly problematic.
What Is Intrinsic Safety
Hazardous areas can generally be classified by the nature of the hazard. The National Electrical Code (NEC) specifies these hazards by classes, divisions, and groups.
Classes define the type of hazardous material in the atmosphere. Flammable gases and vapors are Class I. Combustible dust is considered to be Class II, and ignitable fibers are Class III.
Divisions declare the probability that a hazardous environment exists. Division 1 means that the substance noted by the class has a high probability of being present in a high enough concentration or quantity that under normal conditions there could be ignition or an explosion. Division 2 means that there is a low probability of this type of occurrence, or that it will only occur if there is an equipment failure.
Groups A through G defines the specific hazardous material. For example, Group A is an atmosphere containing acetylene. Other groups include hydrogen, ethyl, isoprene, gasoline, ammonia, benzene, butane, methanol, aluminum dust, titanium dust, coal dust, and many others.
Qualities That Make A Load Cell Intrinsically Safe
Equipment that is designed to be Intrinsically Safe is meant to be used in hazardous areas. The requirement is to reduce the total energy available so that no ignition can be caused. This means that no spark can be caused, and temperatures of the system will be kept low.
The amount of energy available is calculated by first determining the values of all items with the system that have the capability of storing energy. Among others, this includes capacitors, inductors, and batteries. The value, voltage rating, and current rating are all considered.
The value and current ratings of resistors must also be appropriate. If the voltage of the system is applied to a resistor, it must not be able to generate enough heat to cause a spark.
As a generalization, standard strain gauge load cells do not include capacitors, inductors, or batteries, meaning there is only a very negligible amount of stored energy. The resistance of the strain gauges and the excitation voltage of the load cell will determine the current flow through the strain gauges, and therefore the power consumed. The type, shape, and size of the load cell itself will determine the temperature rise of the load cell.
Pressure transducers that utilize strain gages can be considered to be specialized types of load cells. In this case, the strain gauges are usually bonded to a thin diaphragm. The difference in pressure between each side of the diaphragm will cause it to deflect, stretching the strain gages, developing a differential voltage.
Industrial Uses Of Intrinsically Safe Load Cells
Load cells are used in virtually every industrial environment that requires the use of weight measurement. They are almost always coupled with a weight display or other output device. This system is considered to be a scale.
Scales are ubiquitous throughout the industry. They come in a very wide variety of capacities, shapes, and types. These can range from laboratory balances to bench scales, floor scales, drum scales, platform scales, and innumerable other variations.
Any one of these varieties of scales may be required for use in different types of hazardous locations. Scales that are approved for these classified environments must incorporate intrinsically safe load cells.
Intrinsically Safe Load Cells By Arlyn Scales
Creative engineering has allowed Arlyn Scales to develop intrinsically safe load cells that offer unique advantages. This applies not only to strain gauge load cells but also to special Surface Acoustic Wave (SAW) load cells that are used in Ultra Precision Scales.
The resistance of the strain gages used in most load cells is nominally 350 ohms. As noted, the current flow through the strain gage, and therefore the power dissipated and heat generated, is dependent on the resistance.
Arlyn’s strain gage load cells have a much higher resistance value of 4500 ohms. Therefore the power consumed will be about 13 times less. Much less heat is generated, and there are many additional benefits associated with the circuitry required to send current to the load cell.
The net result is that Arlyn can offer Intrinsically Safe Scales using these load cells that offer a range of benefits, including superior performance and much lower pricing. For example, if the included battery pack is used, the battery life will be much longer. If an external power supply is chosen, it will be simpler, easier to wire, and just a fraction of the cost.
These intrinsically safe units are configured as bench scales, platform scales, and cylinder scales, among others. They are available in capacities ranging from 5 lb up to 20,000 lb, and higher. Options include a number of different communication choices, such as RS-422, USB, or Ethernet.
The Intrinsically Safe SAW Ultra Precision load cells have allowed Arlyn to offer much higher accuracy than any other type of scale. A standard intrinsically safe scale with a capacity of 100 lb has a resolution of 0.02 lb, while the Arlyn SAW scale has a resolution of 0.001 lb, which is twenty times better. A standard 1000 lb scale has a resolution of 0.2 lb, compared to the Arlyn SAW scale at 0.01 lb.
Safety, Performance, Flexibility, And Value
Most intrinsically safe load cells are very similar to most others in the market. Only Arlyn Scales has engineered superior load cells. This translates into superior intrinsically safe scales.
Contact our technical specialists to find out more about our load cells. They will provide the best intrinsically safe solutions for your applications.
