Environmental Chamber Upgrades and Retrofit Kits
Upgrading a tensile testing machine with a thermostatic chamber can be an expensive endeavor. Most UTM manufacturers will require the machine to be sent back to the factory for the installation. Given the costs of shipping heavy machinery, most laboratory managers will choose to purchase a brand new machine with the chamber included. What if it were easier to upgrade an existing universal testing machine with an environmental chamber?
The Universal Grip Company has designed an Environmental Chamber retrofit package which can work with any existing dual column universal testing machine. The chamber is mounted to a weighted floor sled and can be wheeled into position for testing at elevated or low temperatures. Liquid nitrogen gas is used for cooling the chamber, while electric induction coils are used to heat up the chamber. The novel retrofit upgrade kit can be installed on-site with minimal disruption to the lab.
Certain ASTM procedures require the use of a temperature controlled chamber in order to perform tests in hot or cold conditions. Our standard environmental chambers range from -70°C to 280°C and are available on all Galdabini dual-column benchtop testing machines. The chamber is cooled using liquid nitrogen and the temperature is controlled using an RTD temperature sensor. A maximum temperature of 350°C can be reached.
Heat-treated grips and fixtures must be used when testing in conditions over about 150°C. These special grips are nickel-plated which allows them to resist the hot oven temperatures.
A video or laser extensometer can be used for high accuracy strain data.
Installation of the temperature chamber is relatively easy, especially if you are using the weighted sled to support the system. Most users can install a temperature chamber without the need of an onsite technician. Universal Grip is able to support onsite installations of the sled-based environmental chamber for virtually any dual column tensile testing machine.
The most difficult step is installing the hose coming from the liquid nitrogen tank. This quick video demonstrates how to install and insulate the connecting hose for cooling. Heating the chamber is simple and the plug can be wired for US or International electricity.
Heating a chamber is rather simple but, cooling is a bit more complex. There are different set ups depending on two things, how cold you need to go, and for how long.
Liquid Nitrogen - Cold/Short - LN2 gas is emitted into the chamber via a tank which can be provided by most any major gas supplier. This is great for bursts of cooling, but can become expensive over time for long cooling applications. It also takes a decent amount of gas to get the chamber down to a low temperature.
Basic Refrigerator - Not as Cold/Long - The refrigeration unit is perfect for long-term cooling applications down to about -20 degree celsius. The setup for this is also pretty easy.
Chilling Machine - Cold/Long - The chiller is used for cooling down to about -50 Celsius for long periods of time. The chilling system is similar to that used for the Charpy Chiller. A circulator vents the cold air directly into the chamber.
Words to the Wise:
Special considerations must also be made for the size of the grips used in an environmental chamber. The space inside the box is limited, so not every fixture will fit.
The furnaces heat up at a rate of 5° to15°C per minute, slowing down as they reach closer to their high limit range. Heated coils can be used on the window to control for any condensation and fogging.