This article contains everything you need to know about humidity chambers.
You will learn:
A humidity chamber is a mechanism that creates different environments to allow manufacturers to test their products to the harshest of conditions. It also enables them to see how their products react to variations in humidity. Manufacturers are able to test the various parameters of their products in the harshest of conditions.
The purpose of humidity chambers is to test the influence of varying environments on products to determine the length of their usefulness and at what point they will fail. The collected data assists engineers in adjusting their designs and selecting more resilient materials.
The different varieties of humidity chambers allow testing to be completed in a static or dynamic state depending on the required data and the type of product. Humidity chambers are used as extended testing chambers to determine a specimen‘s reaction to elevated moisture conditions when exposed for weeks or months.
The main components of a humidity chamber are ones that introduce moisture and heat. There are a variety of methods used to introduce moisture into the chamber, which can be in the form of a spray or bath. The same concept applies to heat that is supplied in the form of coils or heating elements.
In most cases, humidity chambers are designed, manufactured, and produced to fit the setting that the customer requires. Though there are many varieties of chambers, the basic components of heat and moisture are necessary to create the needed humid conditions.
The two factors that affect the stability of a product are temperature and humidity, with humidity being the second most damaging. It is for this reason that manufacturers test the effects of humidity on their products since humidity fluctuations cause expansion and contraction. The three basic methods for creating artificial humidity are steam generators, atomizers, and water baths. The AGREE form of test chamber is also used to test humidity as well as temperature changes and vibrations.
Steam generators have immersion heaters that heat water inside the chamber. As the steam is generated by a tank of water, it rises to the top of the chamber where there are heaters to create humidity. Steam generator chambers are capable of producing heat from 300° C up to 1300° C from CNC programmed control panels. The main benefits of a steam generator humidity chamber is its ability to produce a high volume of moisture with consistent excellent quality water vapor.
Atomizer test chambers have a spray nozzle that sprays atomized water as a means of generating moisture and humidity. As the water passes through the chamber heater, it is heated to create humidity. The operational process of an atomizer test chamber is simple and easy to understand as well as being capable of generating high volumes of moisture.
Water bath test chambers work on the same concept as a steam generator without an enclosed box. A small water bath is fitted in the mixing plenum with the heater. As air enters the assembly, it passes through the bath where it picks up the water vapors. This form of chamber provides a quick response since it uses a small amount of water and does not require the temperature of the water to be at the boiling point.
AGREE is a military acronym for Advisory Group on Reliability of Electronic Equipment. AGREE chambers have the same capabilities as all humidity chambers with the added feature of being able to do vibration testing at the same time atmospheric conditions are being tested. They were widely used in the early to mid-1980s at the request of the United States Military. This type of chamber is specially designed to be able to accommodate the vibration or shaker accessory.
A portion of the air returning from the conditioned area is directed through a water spray area with a closely controlled temperature (dewpoint). The water spray is adjusted to maintain the dew point temperature of the targeted condition. As the air passes through the water spray, it is cooled down to the temperature of the water and approaches saturation.
The air then leaves the spray chamber through a mist eliminator, which removes any excess water vapor and is then mixed with air that has bypassed the spray area.
After passing over an electric heater, to heat the air back to the desired dry bulb temperature, the air is returned to the conditioned space.
The process provides very precise humidity control. The system does not distinguish between humidifying and dehumidifying and is always setting a dew point and reheating.
Industries use testing chambers to judge the effect of different weather conditions on the physical, chemical, and mechanical properties of assemblies, parts, and components. These tests are critical in determining the viability of a product for mass production or producing them for other manufacturers and the public.
In the past, products were put on the market with the hope they would last. Until the development of testing chambers, much of the introduction of products was guess work. Humidity chambers provide critical data about products as well as materials for the design of new products.
There is a long list of industries that depend on humidity chambers to provide them with the necessary information regarding the stability and endurance of their products.
The main function of humidity chambers for the auto industry is to simulate weather conditions by pumping in hot moisture filled air into the chamber. The ability of cars to withstand the abuse they endure is a critical issue to producers. By ensuring a vehicle can tolerate all of the types of weather they will encounter is important for the life of the vehicle and the safety of its passengers.
Humidity chambers for the automotive industry come in several types with ones designed to test individual parts and assemblies with others that are large enough for an automobile to drive in.
Rubber is highly affected by climatic conditions. It has a high tolerance but is susceptible to change due to temperature and humidity. The purpose of a humidity chamber is to test how rubber behaves when subjected to 95% humidity. By using a humidity chamber, the cracking and melting properties of rubber can be determined.
Humidity is an important factor in the pharmaceutical industry since moisture can cause drugs to degrade rapidly, which makes humidity testing data critical to determining the stability of a drug. The parameters for humidity testing vary but are measured in accordance with the amount of water vapor applied to the chamber.
Air is composed of nitrogen, oxygen, and other elements. Between the molecules of these elements is water. The ratio of the molecules to the amount of water the molecules hold is humidity. When the air is heated, the molecules move apart leaving more room for water. This is the factor that is tested in a humidity chamber when the temperature increases. The data provided lets researchers know at what temperature the humidity will damage or cause a drug to deteriorate.
The exposure to moisture and humidity can cause plastics to discolor, have surface crazing, chalking, and becoming brittle. It is important to test for these factors since they can lead to failure of a plastic product. In most cases, plastic is put through damp heat cycles, which is determined by the durability requirements of the product.
Automotive producers have a set of standards and requirements for their plastic parts. Humidity chambers are engineered to replicate the conditions to examine the behavior of the product's components in extreme conditions. Where the part is located in the vehicle determines the severity of the testing.
An important aspect of the production of electrical components and complete systems is to determine the humid conditions that result in the failure of components. The conditions that are tested vary between 60% to 85% humidity. The purpose of the testing is multidirectional and is used to determine how products will perform in storage, shipping, and in harsh operational conditions.
When testing electronics, it is not necessary to examine humidity at low temperatures. As the temperature rises above 50° C, humidity becomes an important factor in how a product will perform. In those conditions, humidity has to be measured for condensation on electronic devices.
Much of the testing for aerospace products is similar to that for electronic components since aerospace instruments are subjected to harsh conditions. One of the tests used on aerospace products, due to the exposure to varying climatic conditions, is thermal cycling where a component is put through wet and dry atmospheres in rapid succession.
The time between exposure depends on how the part will be used and its type. For aerospace products, there are a strict set of standards that manufacturers are required to follow. Many of them correspond with those established for the military.
The conditions that products for the military have to be tested against are wind, rain, dust, and extreme heat. Humidity chambers are able to replicate high moisture atmospheres in a controlled environment to provide substantial data regarding the ability of a weapon or component to survive harsh conditions.
The United States defense standards or military standards are identified by codes, which are represented by MIL-STD, MIL-SPEC, or MilSpecs. Adherence to these codes ensures that products for the military meet the required specifications for reliability, compatibility, and interoperability. In the case of humidity, the standards define the correct heat to moisture ratio for how a part, mechanism, or assembly will be used. The conditions of the testing vary depending on the specified environment. The specific regulation regarding humidity is MIL-STD 810 G, which applies to materials that will be deployed in warm or humid environments.
All instruments and equipment that are used for medical purposes have to be thoroughly tested prior to being sold or marketed. Much like the pharmaceutical industry, the medical industry has to adhere to stringent governmental guidelines, standards, and regulations. These restrictions apply to equipment used to test medical devices that will be used for patient care.
Humidity chambers serve several purposes regarding the performance and capabilities of medical instruments. The initial purpose is to ensure that the instruments will not become contaminated or are not contaminated. A second purpose is to determine the shelf life of the instruments and at what point they will need to be disposed of or replaced.
Testing the weathering capabilities of batteries is an essential part of ensuring their high quality performance. The critical factors that need to be determined regarding batteries is their durability, susceptibility to corrosion, and over all performance. Humidity chambers are used to do rapid cycling of batteries through a variety of environmental conditions.
Humidity chambers for batteries have special fixtures that allow the testing of over 50 batteries during one testing cycle. By being able to test multiple configurations of batteries in a single test cycle, researchers can gather a wide range of data regarding each of the different designs.
Unlike other forms of humidity chambers, battery testing chambers have to have additional electrical cables to be attached to the batteries during testing. To allow for the testing of multiple batteries, shelves or special fixtures are added as well. To ensure that a humidity chamber is capable of testing batteries, it has to be examined for the special battery fixtures and cables.
There are several variables that can affect the durability of a product. Humidity chambers are made of materials that ensure their durability and optimize their performance so that they can provide accurate and reliable data regarding the many factors that can cause deterioration and failure of products. Since a humidity chamber is a miniature environment able to create a wide array of conditions, it is made of durable materials capable of withstanding the conditions that it creates.
Humidity chambers come in several sizes from desktop models to ones large enough to walk in. Regardless of the range of sizes, all humidity chambers have several elements in common, which include wall design, sealing materials, doors, observation ports, humidity controllers, and temperature settings monitor.
The construction of the walls of a humidity chamber is an essential part of the design. A major factor in the testing of products is to ensure that the created atmosphere is not contaminated by the surrounding environment. All humidity chambers are double walled and can be modular or welded. The welded design is preferred since it offers a better seal to the enclosure.
The sealing material for a humidity chamber has to be resistant to compression, steam, pressure, and temperature variations. The types of materials used to seal doors and windows are silicone, rubber, and certain polymers. The chamber sealant ensures that the chamber is protected against any intrusive factors that could cause harm to the chamber or corrupt the data.
To preserve and contain the environment in a humidity chamber, doors are double walled and mounted with heavy duty hinges with a locking mechanism that completely seals the chamber when closed. The construction of the door is essential to ensuring the integrity of the chamber and blocking any potential ambient contaminants that could distort the test results.
The control mechanism for humidity chambers is a proportional integral derivative (PID) controller, which provides continuous modulated data and error values or the difference between the setpoint and measured process variable. The controller takes in the accumulated information and makes automatic corrections in accordance with the proportional, integral, and derivative terms.
A PID instantly and automatically makes corrections to the controlled function. If the particulate humidity falls below the desired setting, the controller makes the necessary adjustments to keep the ratio constant.
The heat for a humidity chamber is provided by a direct heating coil, wire, or electrical heating element,which evenly distributes heat to all parts of the chamber. When a humidity chamber is designed, its size determines the heat range. Large walk-in chambers have a highly complex heating system connected to the air supply, while smaller chambers are able to use a more direct heating method.
The heating elements are normally encased in ceramic. The calculation of the required temperature is computed by the control system once it has been programmed with the parameters for the items of the testing.
The purpose of the air supply system is to circulate the humidified air in the inner chamber and consists of a circulating motor, circulating wheel or fan, and air duct system. The air supply system is designed to pull in air from the surrounding environment and distribute the humidified air in the chamber.
There isn‘t one single way that the humidity in a humidity chamber is produced. Some chambers have a water tank that is heated to produce steam that is vented into the chamber, while other systems have spray nozzles. The heating system has water and vapor controls to meet the required international standards for humidity chambers. In each of the systems, there is an overflow control to avoid having the chamber having too much moisture.
One of the key requirements of a humidity chamber is durability. They are constructed of thick and durable metal sheets that are designed for wear resistance of the highest quality steel. The majority of test chambers are made with a welded steel frame on the exterior and a stainless steel interior liner. They have fiberglass or silicone insulation with a 0.25k factor.
To add to the life of a test chamber, the metals are powder coated and painted for corrosion resistance and ease of cleaning. A key feature of humidity chambers is their double wall seal that ensures the quality and accuracy of atmospheric tests.
The types and designs of humidity chambers vary according to the type of testing to be completed and the size of the parts. There are test chambers that can fit on a shelf to test the effects of humidity on small parts. On the other hand, walk in and drive in chambers are large enough for a car and large computing systems.
In most cases, the type of chamber, that a customer purchases, is designed to fit the specific needs of the customer. Each industry has requirements and types of data that are needed to ascertain the quality of their products, which necessitates producers to design and manufacture a wide variety of test chambers.
Regardless of the specific designs and varying sizes, there are certain criteria that are applicable to all forms of test chambers.
Benchtop test chambers are a cost effective method for the testing of products. They are used for testing smaller components such as electronics, sensors, or cell phones. They are made for research labs or small businesses. Benchtop test chambers vary in size from 0.89 cubic feet up to 5.5 cubic feet. They can have the same basic features as larger units in a more compact size.
Reach-in test chambers have a smaller footprint than larger models with similar versatility as benchtop models. They come in a vertical configuration that allows for easy access but are completely sealed during testing. Reach-in models come in several sizes to match the available space. They are designed with casters or wheels for convenience.
When humidity chambers are large enough to walk-in, they are specifically designed to fit the location and temperature requirements. Walk-in test chambers can be of modular construction where they are installed as a single unit or be built on site depending on the needs of the customer.
In the case of walk-in humidity chambers, some units may require a highly sophisticated steam distribution and flow system to ensure uniformity of the desired conditions. Other walk-in chambers have a simple duct system to provide uniform airflow. Walk-in chambers are widely used by automotive, electronics, and battery manufacturers.
The main purpose for drive-in test chambers is for the testing of vehicles in several atmospheric and environmental conditions to determine their life span and durability. Much like walk-in chambers, drive-in chambers have to be engineered to meet the needs of the customer, which are mainly automotive companies.
Drive-in chambers are programmed to test all of the movable parts on a vehicle, which include doors, windows, various types of switches, lights, and knobs. One of the essential features of a drive-in chamber is to test the endurance of motors in a variety of climatic conditions.
Scientific testing chambers are much like any other variety of test chamber and used to create mini environments. The purpose of scientific test chambers is to examine specimens for potential flaws or problems. The data collected is crucial for the development of future products for food science, pharmaceuticals, and electronics industries.
The types of testing methods range from simple elevated temperatures to extreme humidity. The main purpose of scientific test chambers is to complete testing of specimens on site instead of sending them out to laboratories.
Laboratory test chambers are used to create a variety of environmental conditions such as corrosion testing and for biological research.
The decision to do in-house testing has several variables, which include the size of the company, the types of products produced, quality control, and cost. Once the decision is made to purchase a test chamber, there are other factors to be considered. In the case of larger companies with specific goals, the choosing of a testing chamber is based on scientific research and the demands of their clientele. As companies grow and expand, they find that they can better serve their customers by doing thorough research on their products.
The size of the footprint that the company has available is a guiding factor when making the decision to purchase a test chamber. Test chamber manufacturers work with their clients to ensure that the chamber they purchase fits the space available and the client‘s needs.
Temperature is an essential part of a humidity chamber since it is necessary to create the vapors and humidity. The majority of chambers are capable of reaching temperatures of 200° C. The factor that can influence the range of temperatures to be achieved is the construction of the chamber and its stability.
The design of the test chamber determines the amount of water needed to create humidity. As important as this is, it is also critical that there be some form of drainage or method for removing water at the end of a test cycle. The location where the chamber will be placed should be designed for a water supply and proper drainage.
Every humidity chamber has a different ramp-up and pull-down time. When planning to purchase a unit, it is important to consult with researchers to determine the time frame they require to complete the collection of data. Long ramp-up times can delay tests and may produce tainted results depending on the item to be tested. Manufacturers are careful to examine this factor with their customers to ensure the unit meets the customer‘s requirements.
Most humidity chambers have an RH factor between 20% to 98%. This consideration is determined by how the product is to be tested and what data is required. In the majority of cases, this is planned long before contacting a test chamber manufacturer.
The decision for the type of controller is a central factor when purchasing a humidity chamber. The features that offer the best results are controllers with a microprocessor, which can be LED, LCD, or touch LCD. An RH display comes with all humidity chambers as well as a solid state RH sensor.
In most cases, the type of humidity chamber is decided by the available footprint. A limited footprint would suggest a benchtop or vertical test chamber. As a part of this factor, the construction of the chamber needs to be considered such as how the seams are welded, the internal seal, and how the door opens and its gaskets.
The purchase of large test chambers is a budgetary item and is conducted more carefully. This type of chamber is built to the exacting standards of the customer.
The purpose of humidity chambers is to identify the weaknesses and flaws in tested items such that the errors can be corrected. The variations in humidity and heat quickly expose the vulnerable areas of a product and offer a prediction of its survivability. The various tests are designed to life-test the product as well as analyze its viability and parameters.
Many products have coatings to protect them from harsh and damaging atmospheric conditions. Humidity chambers place coated products in the harshest of environments. The results of the tests can cause cracking in the coating, expansion, contraction, moisture ingress, corrosion, and abrasions.
Sealed units that have a window, viewport, or windshield are tested for moisture seepage between the layers. Since these products are exposed to rapid temperature changes, they are normally put through tests that rapidly raise and lower the temperature and humidity. If the product fogs, it is an indication of its potential for failure and poor quality.
The two most damaging atmospheric conditions are temperature and moisture. To ensure that a product is not susceptible to water ingress and has a tight seal, it is subjected to several cycles of humidity with varying moisture content. The failures that emerge from the testing is leakage and water droplets or collecting.
Atmospheric conditions create a great deal of stress on a product as it passes through a variety of climatic conditions. Humidity chambers are able to create any of the types of conditions that can cause the mechanism of a product to fail. In essence, the test of mechanical components and their proper function is the main concern for manufactures especially in relation to electronics and microcircuitry.
There are an endless number of agencies, organizations, committees, and governmental regulations that govern humidity chambers. The more stringent regulations are related to pharmaceuticals, medical suppliers, and food production. A few of the regulating groups are listed and described below.
The purpose of the IEST is to guide professionals through international regulations and standards. It has educational programs regarding environmental testing, testing reliability, and other technologies. The members of the IEST work together to publish industry best practices.
The ISO is a highly regarded international standards setting group that is composed of representatives from a variety of nations. The ISO standards for humidity chambers include:
ISO 10605 – Testing of vehicles for electrical disturbances caused by humidity test conditions.
ISO 16428: 2005 – Testing standards for surgical implants.
ISO 16525-7:2014 – Testing standards for adhesives.
ISO 7137: 1995 – Testing standards for airborne devices.
ISO 9022-20:2015 – Testing standards for optics and photonics.
The UL outlines acceptable processes for testing and evaluating products to determine the compliance of the standards for risk, injury, and hazards. The organization offers guidance and assistance for the development and testing of new products and ones that are currently on the market.
The main focus of the ICH is the development and registration of pharmaceutical products as well as their testing. The goal of the organization is to create cooperation between regulatory agencies and the pharmaceutical industry.
The FDA oversees any devices that test food and drug products that will come in contact with the public. The main aspect of the FDA‘s involvement with humidity chambers is specified in Q1A(R2).
Q1A(R2) – This portion of the FDA standards outlines testing recommendations for drugs, various substances, and products, which include temperature, humidity, and trial duration for climatic zones. The purpose of the testing recommendations is to provide evidence regarding the stability and quality of a product in various environmental conditions.
The ASTM is one of the earliest organizations to establish standards for testing of products and is a member of the ISO. It includes several thousand testing standards for industries that range from aerospace and chemicals to medical devices and telecommunication equipment.
The IEC has developed standards for the electronics and electrical industries. IEC 60068 delineates the methods for environmentally testing of electronics. The methods described are ways to assess how electrotechnical and electronic equipment should react in harsh environments and the conditions for testing and measurement.
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