This article contains everything you need to know about temperature chambers.
You will learn:
A temperature chamber is a controlled environment capable of producing conditions that a product will encounter during its use. These highly controlled technical tools are able to produce the types of hazards, uses, and atmospheres a product may endure. To determine the lifespan of a product, temperature chambers are able to create conditions that simulate a product’s usage life by rapidly aging it.
Temperature chambers provide companies with the opportunity to examine how a product will react when put through the most adverse conditions. The ability to perform and create these situations can forestall introducing a product into the market that is unable to meet customer expectations.
Different methods are used by temperature chambers to create the various levels of heat to simulate different atmospheres. The variations in processes have little to do with the efficiency of the device but are more closely associated with the chosen processes of manufacturers. Many producers offer several methods to meet the needs of their customers.
Temperature chambers test the prolonged effects of a varied range of temperatures to examine the quality parameters of a product or part. They help determine the behavior of the tested material in severe conditions that involve changing temperatures in relationship to variations in humidity. The tests can be static over time or dynamic to induce and cause failure.
Temperature chambers, or environmental test chambers, perform thermal tests using forced air convection. In many ways, they operate much like an oven. Their main requirement is air flow, which is powered by a fan and motor to cycle air in the test chamber.
There are three types of thermal testing methods, which are cycling, burn-in, and shock. Each test evaluates the durability of a component at extreme temperatures.
Thermal cycling is a controlled test where the chamber alternates between temperature extremes. The rate of the changes is adjusted to limit the amount of thermal stress and to guarantee that the part achieves the required temperature. These periods of pause are referred to as soaks. A great deal of care is taken to control the rate of the changes such that the temperatures do not too quickly reach temperatures beyond what a part can withstand.
The burn-in test is a set temperature that is held for an extended period of time. The purpose of the test is to determine the ability of a part to perform in the conditions of a particular environment. The test has precision temperature control with power measurements and exceptional reliability. The goal is to ensure the performance of components before they are shipped.
There are a wide variety of industries that use the burn-in test that range from semiconductor producers to tests for consumer appliances and military hardware. The main concerns of the test are to ensure the safety and reliability of products.
Though thermal shock testing may seem to be similar to cycling, the basic difference is the amount of time spent at each level of testing. The ability of a product to withstand severe changes in temperature is a necessary attribute that products must have since they may be subjected to a wide range of temperatures during their usefulness.
Thermal shock testing is the most severe form of temperature testing. The high rate of change between temperature gradients is approximately 30° C every minute or faster. It is used to test packaging, aircraft components, military equipment, and certain electronics.
There are three possible forms of thermal shock chambers, which are defined by the number of zones they have. The two zone version carries parts in a basket between the various temperatures. In the two zone double capacity version, there are two hot zones with one cold zone that is constantly in use. The three zone version has a hot and cold zone with an ambient temperature zone.
An AGREE test chamber is a unique version of environmental test chambers. AGREE is an acronym for Advisory Group on Reliability of Electronic Equipment, which was established by the military in the mid to early 1980s. Aside from being able to perform temperature testing, AGREE chambers have the extra added feature of conducting vibration testing while cycling products through various temperature zones.
Manufacturers use temperature chambers to test their products before introducing them to the market. This is especially true for items that are required to be of high quality and longevity. Temperature chambers provide the opportunity to create manufactured environments and conditions that can simulate the types of conditions that a customer may face with a product. The benefit of temperature chambers is the ability to create specific possibilities in an isolated and controlled environment.
A wide variety of industries rely on the data that is produced by test chambers. The size and type of chambers depends on the industry and their requirements. Semiconductor, automobile, cement producers, the food industry, and pharmaceutical companies depend on test chambers to assist in perfecting their products. In many cases, the design, structure, and application of test chambers are determined by the customer to meet their specific needs.
One of the critical tests of rubber is at low temperatures in cold climates. The temperature retraction test evaluates the elastic properties of rubber at extremely low temperatures. The rubber is elongated and frozen after which its retraction value is calculated. The cooling process is performed by liquid nitrogen.
Of the five families of rubber, general, high performance, oil resistant, and high and low temperature, only three of them are suited for use in harsh environments with severe temperature extremes.
To guarantee that the material will perform properly at extreme conditions, various combinations of rubber materials are put through a series of varying temperature tests. Though rubber is a resilient and strong material, it is susceptible to degradation due to atmospheric conditions.
Pharmaceutical products can be severely damaged when exposed to incorrect temperatures, which degrades their properties. Decomposition can happen, which drastically diminishes a drug's effectiveness. This leads to ruined medications unable to perform as intended.
To determine the temperature range that pharmaceuticals can endure, they are put through a series of temperature chamber tests to establish baseline data and warnings. In some cases, products may be required to be kept at a constant temperature during shipping, use, and storage.
The use of electronic components is rapidly growing as the demand for safety, performance, fuel economy, and durability are increasing. Automotive electronics include semiconductors, sensors, and various sub-systems. Modern cars have as many as fifty sensors, switches, and other forms of electronic controls.
To ensure the performance of these electronic components, they are tested in temperature chambers with variations in temperature between -80° C to 225° C or higher. These conditions can be created in a benchtop chamber or a drive-in one to test the durability of all components at once.
Larger components that are tested include engine parts, batteries, and airbags that have to be able to perform in harsh and stressful conditions.
Temperature chambers for the electronics industry are designed to test ICs, circuit boards, semiconductors, transducers, drives, and power supplies. Test chambers for the testing of electronics are designed to simulate a variety of atmospheric and climatic conditions.
The electronics market is rapidly changing and requires immediate response. Temperature chambers provide instant data regarding the durability and longevity of a component. The accumulated data determines the reliability and feasibility of a product before it is put on the market.
The medical industry has very stringent regulations regarding the manufacture, shipping, and design of its products. These requirements are stipulated by national and local governments for the protection of the public.
The standards for medical products also apply to the equipment used to test them. In this regard, the Federal Drug Administration (FDA) and other agencies have published specifications regarding how medical products will be tested.
The testing of medical equipment involves protection against contaminants, which requires the testing of packaging. The next concern is shelf life and how long a piece of equipment may be stored before needing to be replaced.
Types of equipment tested for the medical field include respirators and ventilators that come in direct contact with patients.
The main focus of testing of military equipment is how they will react to the harshest of conditions. The various tests can determine how a product will react and how long it will last. These are critical factors for soldiers serving in the most hazardous of conditions.
Manufacturers that sell products to the military are guided by the specification of MIL-STDs (military standards) for aerospace and automotive products. The specifications of the MIL-STD standards minutely specify the temperature range that equipment must meet to be acceptable.
Of the many industries that rely on temperature chambers, the telecommunications industry requires them as a means to determine the life expectancy of various products, especially cell phones that endure a wide variety of conditions and use since they perform as communication devices and computers.
There are very specific guidelines for testing of products for the telecommunications industry, which follow Telcordia test requirements. Telcordia has developed standards that are widely used in the telecommunications industry with specific categories for various and specialized types of telecommunication devices.
The types of products tested for the telecommunications industry include cell phones, switches, connectors, fiber optics, line protectors, and network interfaces. As with electronic components, the demand for telecommunication products is rapidly growing, which requires companies to minutely test their products to meet the requirements of the public and regulatory agencies.
The telecommunications industry tests its products to meet Telcordia specifications, which are designed to establish product quality and reliability through the creation of conditions products will endure as well as shipping and storage conditions. Telcordia specifications require testing at temperatures as low as -40°C.
Testing chamber customers develop their specifications to meet the Telcordia requirements that are specific to their products.
There are several factors that are examined when testing the weathering factors of plastics. When developing a test, researchers consider the type of polymer, its color, and any forms of additives. The various climatic conditions that are simulated include desert conditions and exposure to sunlight.
The types of plastic tests are normally designed for the specific use of the product, which includes composite plastics used for decking, vinyl siding, and plastic parts for automotive use. It has been found that the temperature of a plastic affects its rate of chemical change as well as its appearance and physical properties.
By exposing plastics to variations in temperature, a determination can be made regarding their degradation rate and service life expectancy. Though outdoor testing has been used in the past to determine the stability of plastics, more and more producers are switching to temperature chambers that provide more accurate data and take less time.
A wide variety of lights have to perform in severe weather. Though we may not consider it, headlights on a car must be able to perform in desert conditions as well as conditions that are well below zero. This variety of weathering requires that lighting be tested in the harshest of environments to ensure their stability and performance.
Light emitting diodes (LEDs) have become one of the most popular forms of lighting due to their low power consumption and long life. Unfortunately, for LED lights to be the most beneficial, they are required to perform in the harshest conditions and are relied on as a source of lighting for airplanes and automobiles. To ensure their proper performance, they are put through the most demanding tests that a temperature chamber can perform.
Temperature chamber is an umbrella term used to describe a chamber that conducts a variety of environmental tests. Excessive or high temperatures is one of the most common causes of product failure, which makes testing a new or present product for those conditions a necessity.
The types of tests completed by a temperature chamber provide data regarding extreme temperature variations and the effects of high moisture content. These tests establish the limits for a product design and provide data regarding product defects or early failure.
Temperature chambers are versatile and capable of creating numerous real-world environmental conditions.
The first criteria you would expect from a temperature chamber is the testing of temperature extremes and their effect on products. There isn‘t a single set of temperature ranges that temperature chambers create. They vary according to the product to be tested and the requirements of the testing company. A typical temperature range is between -78°C and 150 °C.
Rapid cycling at a minute per temperature change can provide significant data regarding a product's ability to endure a variety of conditions in rapid succession. These conditions may apply to shipping and various unstable climatic environments. Several thermal shock tests are performed on electronics especially those for the aerospace industry.
Temperature chambers play a significant role in the testing of humidity since increased temperature gradients are a necessary part of raising humidity. The combination of moisture and heat allows for the expansion of water molecules in the air creating specific forms of humidity.
Temperature testing is an essential part of altitude testing since there are rapid changes in temperature as transports rise through the atmosphere. Temperature chambers are able to simulate temperatures at each change in altitude and provide data regarding a product's ability to endure in the varying environments.
Accelerated weathering is the creation of potential weather conditions that a product may possibly encounter during its use. The conditions can vary between typical, normal weather to seasonal fluctuations that may include heavy storms and disasters. By simulating weathering and closely regulating it, data is provided more rapidly and quickly to make the determination of the stability and endurance of a product.
The accumulated data offers insight into how a product reacts to light, heat, drastic temperature fluctuations, and the seasons of different regions of the country. Using the highly advanced computational equipment of a temperature chamber, any form of weather can be instantly and accurately created.
There are a wide variety of sizes and types of temperature chambers from ones that can fit on a shelf to others that are the size of a building. The factors that are essential for choosing a temperature chamber is the amount of space available and the desired conditions to be created.
Though it is possible to purchase a generic test chamber, in most cases, customers work with producers to design a chamber that specifically meets the customer‘s requirements. There are different factors that each customer wants to test and the chamber they choose has to meet those criteria.
Portable temperature chambers offer high performances with a small footprint. They are easy to install, have low power consumption, produce very little noise, but have all of the basic features of larger units. Regardless of their size, portable units can create temperatures that range from -70° C up to and exceeding 150° C.
Benchtop temperature chambers, much like portable chambers, are a cost effective method for temperature testing with a small footprint. They are designed to test smaller components such as sensors, computer circuit boards, and cell phones. Though they may be compact and versatile, they are ideal for research and development operations on a small scale. Benchtop temperature chambers can be 0.89 cubic feet up to 5.5. cubic feet with a temperature range of - 68°C to 180°C.
Reach-in test chambers are slightly larger than benchtop versions. They sit on the floor and have caster or wheels for ease of movement. Much like benchtop and portable test chambers, they have a small footprint with a larger capacity. They vary in size from 10 cubic feet up to 64 cubic feet with a temperature range of -68°C to 180°C. Reach-in test chambers have a temperature variation of ±1.0°C.
As the name implies, walk-in temperature chambers are larger and designed for several or large parts. They can be modular and delivered as a single unit or constructed on site. The majority of walk-in chambers are custom designed to meet the needs of the customer. Panel walk-in chambers have lightweight insulated panels that are quick and easy to install, while solid walk-in chambers have welded walls for a perfect seal.
Walk-in temperature chambers come in a wide variety of sizes from ones that are 286 cubic feet up to chambers as large as over 1400 cubic feet. Though these are common sizes, most types of walk-in temperature chambers are specially designed and engineered. Depending on the design, they can have a temperature range of -40°C up to 150°C.
Drive-In temperature chambers are mainly used to test automobile components and parts as part of a fully assembled automobile. Though individual parts may be tested in smaller chambers, drive-in chambers allow manufacturers to examine the weathering of parts as they interact in a finished product.
As with walk-in chambers, there isn‘t a standard size for drive-in chambers. They can be small enough to accommodate a compact car or large enough for a diesel long haul truck. The specifications and dimensions vary according to the auto maker‘s needs.
The variations in sizes also applies to any of the extra features of the chamber. It can be said that all testing chambers have a PID control system. For drive in chambers, the applications on the system may be more precise and specific for the data required.
A main function of a drive-in test chamber is to examine the weathering effects of climatic conditions on vehicles. The test chamber allows producers to accelerate conditions and simulate any variety of possible weather.
In the majority of cases, environmental test chambers are built to the specifications and requirements of the customer since every industry has different needs and testing requirements. Regardless of the specialization and variations, there are aspects of all test chambers that are similar such as materials, doors, sealing materials, air circulation equipment, and controllers, though controllers vary depending on what conditions are being monitored.
The walls of temperature chambers have an exterior of steel with a stainless steel inner lining. The stainless steel interior has 304 or 306 grade steel. The materials chosen for chamber construction are used for their resistance to corrosion and sturdiness. Test chambers are built, produced, and designed to last as well as be able to endure the stress put on them by the various tests.
Between the steel exterior panels and stainless steel interior panels is insulation. There are several forms of insulation used in test chambers, which can be certain forms of silicone, fiberglass, and polyurethane. In most cases, polyurethane is used for its low thermal conductivity and high performance as a thermal insulation.
A critical factor in door construction is the ability to form a tight seal as well as being very sturdy and rugged enough to withstand constant and continuous use. They have full action clamps that hold them in place. As with the walls, they have a sealing material that prevents contamination of the chamber by ambient materials. In many cases, they have a double paned window made of glass or a clear polymer, which is also tightly sealed. The larger the size of the chamber the more doors it may have, which are double sealed.
Larger chambers also have a defogger or heating cord to prevent condensation on the windows.
The sealing material for the windows and doors can be silicone rubber, certain polymers, or plain rubber. The sealing material is chosen for its resistance to high temperatures, resistance to aging, and exceptional sealing capability. Temperature chambers designed to do low temperature testing may be fitted with double seals.
One of the most critical components of a temperature chamber is the controller, which comes in a wide array of types, programming, and components. The key factor for a controller is its ability to maintain the programmed conditions with very slight variations.
The most important part of a controller is its accuracy of data and reliability. They need to be easily configured and adaptable for a variety of products and conditions. The program has to balance between precise data with ease of programming. Every controller has several features. The majority have a color LCD readout monitor and a variety of application features. They are computer compatible with a USB port for easy transfer of data.
Free air flow is the key to an efficient temperature chamber. It is the one factor that ensures that the temperature gradient reaches all parts of the chamber. Temperature chambers require a heavy duty motor driven blower or axial fan that evenly distributes air throughout the chamber.
There are several methods used for cooling a temperature chamber. For smaller chambers, the heat is expelled through an air cooled condenser. Larger chambers require a more sophisticated cooling system, which may be in the form of water cooling or nitrogen cooling.
Some systems use refrigeration to cool the air and water as it enters the chamber. This is more economical than a water cooling system. Regardless of the system, antifreeze may be mixed with water to enhance the temperature range of the chamber. Though antifreeze is a viable method, it is not as efficient as other methods.
Temperature chambers are heated using wire heaters made of Nichrome. The wires of the heater are looped to generate the greatest amount of heat. Air flow circulates the heat in the chamber to evenly distribute it. This avoids samples being exposed to radiant heat.
Other methods for creating heat in a temperature chamber include gravity or fan driven convection and circulating water bath.
Nichrome Heating – Nichrome is used as a heating element because it is so resistant to electricity. It is used in small products like hair dryers as well as industrial furnaces.
Gravity Convection – Gravity convection uses the natural flow of heat. Since hot air rises, heat is gently, evenly, and naturally circulated without force but still provides uniform heating.
Fan or Forced Air Convection – Fan or forced air convection spreads heat by forcing warm air around the chamber.
The amount of heat that a chamber can produce is limited by the materials from which it is made since certain insulation materials cannot withstand extreme temperature ranges.
Temperature creates stress in a product and is something every product experiences during its usefulness. How important temperature is for a product varies from product to product. Most typically, electronics experience more temperature stress due to the nature of how they operate.
There are certain temperature tests that can be performed to determine the viability of a product. The basic forms of tests are high and low temperature, thermal cycling, thermal shock, and temperature with humidity.
There are various factors that can be identified by high temperature testing.
The lists of agencies, organizations, and groups that oversee the standards and regulations for temperature chambers is long and extensive involving voluntary groups as well as governmental administrative groups. Due to the importance of testing and its required accuracy, manufacturers pay close attention to the requirements they must meet with their products.
Producers who manufacture testing equipment for the food, medical, pharmaceutical, and military industries have specific instructions regarding acceptable standards for their products. Each manufacturer follows the guidelines closely to ensure their products are acceptable.
The requirements for the FDA are not specific to temperature chambers. They are more in regard to the food equipment that is tested in the chambers and specify the types of acceptable tests that qualify food production equipment for sale.
The ISO has set the qualifications for acceptable testing methods in regard to a wide range of products. It is an international organization that has been recognized by the majority of countries. They have a specific list of requirements regarding testing practices and how they should be performed.
Some of the ISO standards:
ISO 11507 – Testing of paints and varnishes
ISO 29664 – Testing of plastics
ISO 4892-1 and 3 (EN) (DIN) – Testing of plastics
The focus of testing for the AAMA is in regard to weather testing of coatings. It outlines procedures and performance requirements for coatings applied to windows and doors.
The AATCC has published standards for testing methods and quality control for textiles and clothing manufacturers.
A few of the codes from the ASTM are:
ASTM C1257 - Accelerated Weathering of Solvent-Release-Type Sealants.
ASTM C1442 - Artificial Weathering Apparatus.
ASTM C1501 - Stability of Building Construction Sealants
ASTM C1519 - Evaluating Durability of Building Construction
ASTM C732 - Aging Effects of Artificial Weathering on Latex Sealants
ASTM C734 -Temperature Flexibility of Latex Sealants After Artificial Weathering.
ASTM C793 - Accelerated Weathering on Elastomeric Joint Sealants.
ASTM D1148 - Rubber Deterioration-Discoloration from Heat Exposure
ASTM D1670 - Failure End Point of Outdoor Weathering of Bituminous Materials.
ASTM D3424 Weathering of Printed Matter.
ASTM D3451 – Testing Powder Coatings
ASTM D4101 – Testing of Polypropylene Injection and Extrusion Materials
As with all the other standards organizations, the military has a long list of specific requirements that must be met by military hardware producers. One of the interesting facts regarding military testing standards is that they are very specific down to the exact temperatures, time of testing, and point of acceptable failure.
Temperature chambers for testing automotive components are strictly regulated for safety purposes and product quality. The list of standards is rather extensive and all inclusive. As new developments in designs arise, the SAE publishes new codes and standards. Below is a short list of some of the types of standards:
SAE AS39029 – Regarding electrical components
SAE AS50151 – Electrical connectors
SAE AS5382 – Fiber optic cable
SAE AS50881 – In conjunction with MIL-W-5088L regarding aerospace vehicles
SAE AS4373 – Electrical wiring
SAE AMS3238F – Butyl rubber
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