Like most industrial products, environmental test chambers are characterized by a diverse range of categories. One of the significant dividing lines between different chambers revolves around the methods used to receive and display information. Put another way, test chambers can vary widely between user interface and information output options. Some chambers are “simple” analog devices that characterized by needles or similar visual displays. Digital types of chambers are more complex and may include front panels, digital keypads, various types of dials and switches, alphanumeric or video readouts, etc. Parameters such as temperature range and humidity range can be seen and modified with such digital apparatuses. Some chambers even contain cathode ray tubes (CRT) or liquid crystal displays (LCD). The most complex types of chamber interfaces and outputs are remote types. For example, some chambers operate in conjunction with programmable logic controllers (PLCs) or send radio signals to host devices.
Materials, Sizes, and Configurations
Environmental test chambers are usually made from steel due to the rigorous applications they undergo, although various parts (e.g. inner walls or doors) may be made from different materials (e.g. glass) depending on the industrial scenario. Since the breadth of tests performed with test chambers is incredibly broad, it is no surprise that they also come in a broad range of sizes and configurations. The smallest chambers (e.g. bench models) hover around a half-cubic foot while the largest types (e.g. walk-in rooms) can consist of up to 12,000 cubic feet. Some chambers are specifically designed to mount on desktops or tabletops (as opposed to work benches), while others are designed to be free-standing. From simple and small benchtop chambers to larger and more complex walk-in chambers, there is a test chamber to accommodate just about any condition or product.
What They Are Used For
Chamber testing that focuses on replicating normal conditions a product would operate under is known as simulation or “testing to pass.” Its purpose is uncovering defects or flaws in a product rather than discovering its operational limits. While many test chambers are utilized to reproduce normal environmental conditions for simulation, they can also be used to create extreme conditions and test the limits of products. Such extreme testing is known as stimulation or accelerated testing. Many products will never actually encounter environmental extremes. However, it is still important to know how different materials and products will respond to additional stress for the sake of product improvements and the identification of special precautions that should be taken. Generally speaking, products are reviewed after failing accelerated testing and either improved (if the failure was deemed unacceptable) or introduced directly to the market (if the failure was deemed acceptable).
There are many different kinds of test chambers which simulate various environmental conditions; many chambers can even control several different conditions at once. Overall, the simulation and stimulation categorization of test chambers integrate with the actual conditions that chambers produce to present a common “stock” of chambers. Some commonly tested conditions include extreme temperatures, sudden temperature variations, humidity, moisture, and varying levels of salt water (which are tested in temperature chambers, humidity chambers, and salt spray chambers). Many other kinds of test chambers exist, such as AGREE chambers, altitude chambers, thermal shock chambers, and vacuum test chambers. Additional test conditions that are commonly replicated include airborne and structural vibrations, shock, dust and sand, and UV radiation. Broadly speaking, test chambers can be divided between those that test environmental stresses and those that test mechanical stresses.
Chambers test the effects of high temperature by adding heat to the environment with electric heaters. Conversely, they test the effects of low temperature by using refrigeration systems (either mechanical or liquid based) to remove heat from the environment. Temperature testing typically falls into the categories of steady state testing, thermal cycling, and thermal shock.
Steady state testing refers to the practice of holding a product at a certain temperature and/or humidity for an extended period of time.
Thermal cycling and thermal shock, on the other hand, both involve changing temperature at preset intervals to test a product’s response to temperature flux. These two types of testing are primarily distinguished by the amount of time or rate of temperature change. Thermal cycling focuses on exposing products to (and holding products at) temperature extremes over an extended period of time. As its name suggest, thermal shock exposes products to rapid temperature fluctuations (normally by switching products rapidly in a “basket” between hot and cold fluid zones within a multi-compartment chamber).
Cryogenic chambers are examples of “stimulation” type devices within the temperature testing category. These types of chambers can achieve temperatures below -200 degrees Fahrenheit, and on the other end of the scale, temperature chambers can reach temperatures of more than 1000 degrees Fahrenheit.
Humidity chambers can test humidity and air moisture extremes, producing humidity levels ranging from 10-100% humidity. Rather than using heaters or refrigeration systems, humidity chambers reproduce desired conditions with either steam generators or (mechanical) dehumidifying systems. (Sometimes air dryers are used to assist the dehumidifying process.)
Other environmental stress chambers focus on more direct sources of product corrosion. A common type of test chamber is the salt spray environmental test chamber. Salt spray is created within the chamber by storing a brine solution in a tank and transporting it via a compressed air nozzle.
Mechanical stress chambers often focus on testing the effects of pressure and/or physical vibration.
Electro-dynamic and mechanical vibration chambers are available to test long-term effects on industrial machinery. Altitude chambers can also test extreme pressures and air variations, while vacuum test chambers can test extremely low pressures.
Environmental test chambers can be utilized in practically any industry which creates products that will encounter degrading or damaging environmental conditions. Some industries that make extensive use of test chambers include the automotive, aerospace, electronics, biotechnology, construction, timber, engineering, food processing, medical, metal, ceramics, pharmaceutical, packaging, textile, and consumer industries. Products that we use every day, like car parts, make-up, medicines, and kitchen appliances, are tested thoroughly to ensure durability, effectiveness, and reliability in common environmental conditions. Test chambers can be used to test small electronic devices or large aircraft or vehicles. (Electronics, in particular, are especially dependent on high-quality and reliable environmental chamber testing.)
The following is only a small sampling of specific applications for environmental test chambers. Mechanical stress and vibration chambers are often used in conjunction with electronics, automotive, and solar products (which tend to undergo such stresses more than other products), while salt spray chambers are widely used with paints and finishes (which are often found in marine environments). The pharmaceutical and food industries depend on environmental chambers to abide by international regulations and establish parameters such as expiration dates and shelf lives. In biology, test chambers enable the successful cultivation of plants and cells by establishing healthy ranges of environmental factors (such as light and humidity). Aerospace companies use test chambers to design products that can handle extreme pressure conditions.
It is important to note that the usage of environmental test chambers in the commercial world is often divided into two phases. Highly Accelerated Life Testing (HALT) is especially useful in the early design phase of a product to discover early design flaws and slash overall testing time. HALT occurs prior to the production phase of a product. On the other hand, Highly Accelerated Stress Screen (HASS) occurs prior to the market introduction or commercialization of a product (during the production phase) in order to uncover actual production defects. Generally speaking, the types of environmental test chambers and testing processes used in HASS are not as rigorous as those applied during HALT.
Since so many manufacturers depend on environmental test chambers to determine the reliability and quality of their products, careful consideration should be given when selecting and using environmental test equipment. There are all kinds of available features, components, designs, and constructions with regard to environmental test chambers. However, it is of utmost importance to consider which components will provide the most accurate results and most beneficial features.
Choosing between “general purpose” and more specialized types of test chambers provides a good illustration of how to weigh various factors to make the best chamber selection. General purpose chambers are characterized by (relatively) small sizes, which make them ideal for the majority of laboratory applications (which require room to operate and low product loading). However, if testing products with large mass (or high heat dissipation), then specialized, high-performance chambers should be used. (It should be noted that walk-in rooms are the most unique type of high-performance test chamber which is characterized by a high degree of customization suited to a user’s particular needs.)
Certain types of chamber features or aspects of the overall testing process may become more important depending on your actual field. For example, some tests may require the operator to see the inside of the chamber or even manipulate the interior of the chamber during the test. Food/pharmaceutical applications often meet this need by using chambers with glass doors. In addition, view ports can be added on the sides of the chamber, cameras or interior lights can be placed on the inside, reach-in ports can be included to allow access from the outside, or a system of controls can be used from the outside to handle components in the interior. (It is important to always keep in mind that such extra features should be chosen based on the type of test conditions and the required accuracy of the results.) Features attached to the exterior of a test chamber can also be significant. Interference from the exterior of the chamber can radically change the results and therefore, depreciate the value of the information gained from the tests. In addition to human interference, exterior environmental and climate conditions should also be considered carefully to ensure that they do not skew test results. For the most accurate and useful results, strict control should be maintained throughout the entirety of the testing process.
You should look for several things in an environmental test chamber supplier alongside standard considerations (e.g. range of products, customer responsiveness, level of customization, etc.). Because of the nature of the product, some environmental test chambers pose environmental concerns. Investigate a supplier’s commitment to environmentally friendly products and practices (e.g. using a low-noise compressor and environmentally friendly refrigerant). Environmental test equipment can be expensive so finding a supplier that offers competitive rental options is also a prudent strategy. Always check to see how closely a supplier or manufacturer abides by industry standards. In the case of environmental test chambers, inquire about standards such as BS EN 60068-3-5 (confirming the performance of temperature chambers) and IEC 60068-3-11 (estimating temperature/humidity conditions in steady state testing).
Overall, using environmental test chambers leads to better products for consumers and leads to lower warranty claim expenses for manufacturers. Though testing can take a great deal of time and effort, it is a wise manufacturing choice that will reduce long-term costs and improve product quality.