Explosion Proof Lights- Glass vs. Plastic |
Article - April 1, 2016 By LarsonElectronics.com
Explosion Proof Lights- Glass vs. Plastic
Explosion proof lights are designed to keep hazardous work environments safe and secure. In addition to providing adequate visibility in dark areas, such products actively prevent sparks or ignitions that can cause explosions. The lighting solution can be found in establishments that deal with explosive gases such as food processing plants, offshore lighting, paint spray booths and marine work areas.
An example of a food processing facility that incorporates explosion proof lights is Koopmans Meel, located in Leeuwarden, Netherlands. The establishment specializes in industrial baking goods, and handles a range of culinary products, including wheat and flour (classified under Class II, Group G). The fixtures allow the company to meet strict HACCP standards, while avoiding issues related to changes in operating temperature, maintenance and explosive dust.
When manufacturing explosion proof lights, designers have the option to use glass or plastic to encase the fixture’s parts. Read on to find out which material is commonly used for explosion proof lighting and hazardous locations.
Sparks and Plastics
Plastics are beneficial when used for lightweight casing solutions and packaging. However, they are not usually applied in explosion proof lights. Generally speaking, the material falls into two categories: thermoplastics (polyethylene- can be melted down and remolded several times) and thermosets (urea formaldehyde- cannot be re-melted, ideal for heat resistance). The main reason why plastics are not suitable for explosion proof lights and hazardous locations is due to its poor spark-mitigating properties. Sparks, or rapid electrical discharges, can penetrate plastic easily, which increases the risk of setting off combustible dust, vapors and flammable elements in the area.
Sparks are produced when an electric field strength surpasses 4–30 kV/cm, or the dielectric field strength of air. When this happens, there is an increase in the number of free electrons and ions in the air. As a result, this temporarily forces the air to become an electrical conductor through dielectric breakdown, allowing a group of electrons to move freely in an air gap. By design, explosion proof lights prevent ignition and electrical sparks from escaping outside of the unit. The mechanisms of the fixture isolate or contain sparks within the light, where it cannot react with flammable substances. The products require superior electrical protection that can block current flows diligently, such as glass. As a mineral material, glass is equipped with incombustible features. It does not promote the spread or creation of flames during exposure to high levels of heat and electricity. Moreover, glass does not smoke or emit toxic products.
The Power of Glass
In a study conducted by Gillinder Glass, an industrial glass manufacturing company, the group compared the viability of glass and plastic (polycarbonate) under various heat and protective conditions. Scientists compared 24 samples of glass, ranging from 300 to 1,100 nanometers in thickness with eight samples of polycarbonate with the same dimensions. The groups findings included the following:
• When exposed to heat, polycarbonate has a tendency to release vapor and warp
• Glass displayed more abrasion resistance
• Glass cleaned easily, and did not scratch or chip
• Removing stains and dust from plastic resulted in scratches
When applied in hazardous locations, glass may help extend the lifespan of explosion proof lights. In industrial settings, the material (when combined with powerful resins) can withstand abrasive cleaning solutions during hose down and sterilizing sessions. Furthermore, when exposed to varying heat temperatures (for example, overhead explosion proof lights above food processing machines), glass can maintain the integral shape of the fixture. Contrary to popular belief, industrial glass is not fragile. It boasts high compressive strength, enabling to resist external pressures without noticeable damage. Glass is also extremely resistant to aggressive chemicals, even at high temperature settings. This feature is useful in plant operations that handle interactive chemicals on a daily basis.
Industrial Glass Trends
Scientists have been developing new ways to reinforce the sturdy properties of glass. Such practices have led to new trends in industrial glass manufacturing and design. In particular, blast-resistant glass is currently being used to provide extra protection for industrial equipment, buildings and electronics. “The new multilayered transparent glass could have a wide range of potential uses if it can be made strong enough to resist small-scale explosions,” said Sanjeev Khanna, a professor of mechanical and aerospace engineering at Missouri University.