The “AGREE” in AGREE test chamber is an acronym for Advisory Group on Reliability Electronic Equipment, which was a group within the Defense Department of the United States that worked to create the AGREE chamber to perform tests on military hardware. AGREE chambers can produce fast-acting temperature extremes; they can jump from 41 to 104℉ (5 to 40℃) within 60 seconds, even with large loads. They also have removable floors so that they can enact vibration test systems. Today, AGREE chambers not only test military hardware but also automotive, electronic, and telecommunications equipment.
Cryogenic test chambers test products that must face temperatures between -238℉ to absolute zero. Applications that often undergo cryogenic testing include flash-freezing and long-term food chilling, metal strengthening, medicine preparation, and preservation and the production of rocket fuel from liquid gasses.
Altitude chambers, or hypobaric chambers, test the effects of low-pressure on products, packaging, and electronics that will be exposed to high altitudes. They can also be used for testing human respiratory and circulatory response to altitudes up to 200,000 feet above sea level. Human testing is for specialized professions and activities, like astronaut and pilot training and athletic training.
Salt spray chambers, also called fog chambers, test corrosion resistance by hanging an object from a rod as the chamber introduces a salty residue that creates fog. This process is relatively inexpensive and used by a number of industries, including aerospace, automotive, construction, and industrial manufacturing.
Vacuum chambers are testing chambers from which almost all matter, including air, has been removed. This is mostly used for aerospace and aviation applications.
Thermal shock chambers test the effect sudden temperature changes have on a product since thermal shock can cause faulting or cracking along stress lines. Many industries rely on this testing, though ceramics and glass rely on it especially because, due to low thermal conductivity and a tendency to expand and compress unevenly, they are at-risk for thermal shock.
Temperature chambers are self-explanatory; they test the effect of different temperatures. They’re often used in conjunction with other testing processes, like vibration and altitude testing.
Because of these varying applications, test chambers also vary in length, width, and design. For instance, some chambers are large enough to drive into, while others contain only a simple desktop.
Important to all environmental test chambers is the validity of their test results. Accurate test results are necessary to make adjustments and improvements upon a product before releasing or re-releasing it. To get these accurate results, engineers must first carefully map the chamber’s design and construction. It needs a space through or area in which workers can monitor the tests. These typically manifest as viewing holes, video feeds or, occasionally, a stand-in area. Engineers must also consider whether control panels should be analog or digital. Beyond construction, testing engineers must be careful to maintain consistency; they must avoid interfering and keep the process as uniform as possible. Finally, they must take into account pre-existing variations of products and materials. The stricter the control, the better and more useful the results.
Environmental testing is a necessary process for any business that hopes to be successful. By finding flaws and weaknesses before a product reaches the public, a company can save money on fixes and enjoy a reputation for quality. It can offer a better warranty and feel confident that it will not face high reimbursement costs. The long hours and expenses put into environmental testing are an investment worth your while.
Environmental Test Chambers—Buying Guide
No new product is deemed market worthy until it passes through environmental test chambers. It is in these chambers new products are tested under various environmental conditions that ensure reliability and quality of the product.
Climate chambers, for this reason, are important for any development process, which makes them necessary for manufacturers. However, environmental chambers are expensive equipment, and many factors need to be contemplated before buying one.
Many factors determine selection criteria, and price primarily determines the purchasing decision for many. This over the time can prove to be a costly mistake.
Therefore, we are discussing important factors that you should consider before buying a chamber. Remember, you get what you pay for; reliability and quality are never determined by price. We will help you to make a decision that will add value to your purchase.
The primary questions that you should ask yourself are:
1. What will be tested in the chamber?
2. What should be the capacity of the chamber?
3. Should it be water-cooled or air-cooled?
4. What is the range of temperature you need?
There are various types of test chambers; you should decide the type based on the application. In the following we will discuss different types of chambers, so you can decide what will suit your requirement.
These chambers are relatively huge, big enough to drive vehicles into them. They majorly are either modular or welded. For construction of modular type chambers, pre-fabricated modules or panels are used, lined with urethane foam insulation. The construction limits the temperature and humidity range that can be attained; at maximum, the temperature can reach up to 100 C and 121 C. The humidity range is 70 C and 95% relative humidity (RH).
Alternatively, in welded chambers, as the name suggests, the internal chamber is welded together, which gives it ability to withstand higher humidity ranges and extreme temperature. They are designed to withstand altitude conditions, and because of all these features, they are more expensive than a modular type.
They are the most common type of remote conditioners or chambers. They come in a range of sizes, starting from 0.5 cubic feet to 70 cubic feet. These relatively portable or handy chambers can simulate practically any environment condition, from temperature variations to humidity, to altitude to rain solar to vibration. Specialized thermal shock chambers are also available in different sizes and configurations; they can change temperature condition from one to another a matter of seconds, checking the reliability in adverse conditions.
Primarily, two types of refrigeration systems are available: expanded refrigerant and mechanically cooled.
In refrigerant-based cryogenic chambers, temperatures can go down to –184 C, using liquid nitrogen. Alternatively, carbon dioxide can be used as refrigerant; however, it can only achieve temperature down to –68 C. These gases unlike, chlorofluorocarbon, are environmentally safe and can be vented directly to the atmosphere.
Mechanically cooled systems follow the same principle that are used in home refrigerators. They are further classified as single-stage refrigeration and cascade refrigeration systems. A single-stage refrigeration system can bring down temperature to –34 C, and in some cases, 40 C, whereas cascade refrigeration systems have two separate systems that can cool the chamber down to –85 C. Single-stage refrigeration systems are less expensive and have fewer parts, which makes them more reliable.
When it comes to environmental test chambers, humidity can be confusing. The humidity measure that you will see in the specifications is RH, which is temperature specific. The moisture in the air at 30 C and 50% RH is not equal to 15 C and 50% RH, the capability of air to hold moisture reduces, as the temperature goes down. This complicates the whole functioning. Instead of going into details, if you need to achieve lower humidity levels, ask for a chamber fitted with a dry-air purge system and refrigeration valves.
In most temperature chambers, the common temperature–humidity range is 7 C to 85 C, with 10% to 98% RH, which is limited by a 5 C dew point.
Other than these considerations, you need to know about air-cooled or water-cooled chambers, construction, safety, temperature change rate, and supplier service after the sale. All these will ensure that you get the best chamber for your requirements.
Everything You Need to Know About Environmental Test Chamber Cooling Systems
If you are wondering which type of cooling system would be best for your application, then read what follows. Here we are discussing the properties and advantages of air-cooled and water-cooled systems used in environmental test chambers.
In climate chambers, the refrigeration system moves heat from the air and product in the chamber to give controlled conditions. The heat removed from the chamber is rejected at the condenser. For this purpose, two types of condensers are available: air-cooled and water-cooled. Air-cooled condensers are further divided as integral and remote air-cooled chambers.
Integral Air-Cooled Chambers
Small chambers are generally installed with air-cooled condensers, so they can be moved conveniently from one area to another. However, some things need to be considered with air-cooled units.
The area where the environmental chambers will be placed should be air conditioned, as chamber’s performance can be greatly reduced if the ambient environment goes above 30°C. The chamber may not work at all, in some cases. To operate efficiently in a high ambient room condition, the condensers must be of higher capacity, which can affect the running cost.
Condensers are commonly installed near the floor, which allows them to get dirty easily. A dirty condenser can be clogged and eventually over time can trip the high-pressure safety. Remote air-cooled condenser or water-cooled are better choice for dirty locations.
Remote air-cooled chambers
In remote air-cooled systems, condensers are placed at a remote place, away from the chamber, generally outdoors. It gives you freedom from the noise and heat; however, remote conditioner systems are expensive to install and maintain since they are complicated.
In water-cooled chambers water is used, instead of a refrigerant, to cool the refrigeration system. Environmental test chambers that need six horsepower or over to operate are water-cooled chambers.
To install water-cooled chambers, you need a cooling tower or dry cooler facility. They are easy to easy to install and maintain if above prerequisites are available. The most common problems with water-cooled systems are related to water flow and differential water pressure supplied to the chamber.
Six Questions You Need to Ask before Buying Used Environmental Test Chambers
Given the cost of environmental test chambers, it seems to be a rational option to buy a used test chamber. It can save money; however, equipment bought without proper research and insight can be a source of grief over time. With second-hand equipment, new issues generally accumulate, which negates all the benefits it gave at first. Maintenance and repair can easily drain all the money you saved on the purchase.
Therefore, we have compiled all the information that you need to make an informed decision regarding your used chamber purchase. The questions listed will help you to determine whether the available climate chamber is the best option.
Question 1: Does the chamber provide the conditions you require?
If you buy a chamber and it does not provide the temperature or humidity range that you want, then the equipment is nothing more than junk. There are many types of environmental chambers, with varying degrees of temperature-humidity range. Check if the equipment reaches the temperatures and humidity levels that you need with your products, as heat, shape, and weight of the product can distort the performance of a machine, especially, the rate of change of temperature.
Question 2: Is the manufacturer still operational?
All equipment, new or old, needs repair and maintenance at some point. The cost of repair and maintenance can escalate quickly, if the original manufacturer has gone out of business, the spare parts will be difficult to find. Moreover, it will be difficult to find personnel with relevant expertise.
Question 3: Does the chamber have proper airflow?
Inadequate airflow in environmental test chambers can lead to formation of hot or cold spots, which results in overheating and insufficient performance. Airflow is a major factor when the rate of change of temperature is higher. For high-performance application, 500 feet per minute (FPM) is considered effective, make it your benchmark and decide.
Question 4: Is the mechanical structure rickety?
Rather than the external structure, you should be concerned about the main chamber, since that is where everything happens. The chamber is regularly bombarded with unfavorable environmental conditions, which take a toll on it. Presence of significant deposits or rust is a red flag. Moreover, check for the alignment of doors and panels, misalignment shows the modification done to structure.
Question 5: What is the condition of the refrigeration unit?
The first thing you need to check is whether the unit has modern CFC-free coolants. Old CFC-based units do not pass the stricter regulations. The other thing that you have to consider is leaking; it is the most common problem with a refrigeration unit, which significantly affects the performance.
Question 6: Does the chamber insulation work?
Only few temperature chambers are seam-welded, most are modular based. With the absence of welding, over time, moisture permeates into the insulation, which affects performance adversely. It is difficult to check for damp insulation, the only way is a visual inspection, check the internal chamber thoroughly for any gaps and abnormalities.