Salt Spray Chambers - Condensation Humidity Mode - how it works
Salt Spray Chamber - Condensation Humidity Mode
This mode of operation is provided as standard on all Plus & Premium models of Ascott salt spray chamber, to enable these chambers to be used for condensation humidity testing, as well as salt spray testing. It provides a facility whereby the chamber can be used to create condensation humidity conditions (fixed at 95 to 100%RH) at elevated temperatures (variable from ambient +10C/+50F to +50C/+122F) and is designed to meet a wide range of international standards for such testing.
The control system of the Plus models enables the user to choose either a salt spray test, such as ASTM B117, or condensation humidity test, such as ASTM D 2247, to be executed by the chamber.
The control system of the Premium models enables the user to program either a salt spray test or condensation humidity, to occur alone, such as ASTM B117 & ASTM D2247, or in sequence with each other , as a simple two part cycle, such as those required by ASTM G85, for automatic execution by the chamber.
Set into the bottom of the chamber is a water sump containing a corrosion resistant immersion heater. When condensation humidity testing is selected, this sump is automatically filled with water, to a pre-determined level, using water taken from the pressurised supply to which the chamber is connected (the same supply that is used to fill and top-up the air saturator used in the salt spray mode of operation). Providing the sump is full of water and the user adjustable set temperature required during condensation humidity testing is at least +10C/+50F above the ambient temperature of the room in which the chamber is located, the immersion heater located in the sump will heat. As it heats, it evaporates moisture from the surface of the sump into the chamber atmosphere above. Eventually the heat from the sump will raise the chamber temperature to the required set value, and at the same time raise the chamber humidity level to 95 to 100%RH. This high humidity level will form condensation on the surface of the samples under test.
Forming the centre-piece of the ergonomically designed control panel is a state of the art Human Machine Interface (HMI). This incorporates alpha-numeric text messaging and digital displays of chamber variables such as temperature, humidity and time (see chamber data sheets for the type of HMI fitted). It is here that the user controls and monitors the various chamber functions. In addition, all chamber control panels incorporate an emergency stop and other safety facilities.
The chamber canopy is effortlessly opened/closed using pneumatic cylinders, which are activated at the touch of a button on the control panel. An automatic purge facility is incorporated to minimise the risk of corrosive salt spray escaping into the laboratory when the chamber is opened.
Strategically located sensors, mounted inside the chamber and air saturator, monitor the climate continuously and convey this information to the Human Machine Interface (HMI), where it is displayed digitally at the control panel. Temperatures are monitored by PT100 precision temperature sensors and displayed to a resolution of 0.1°C. Most chambers (model specific - see chamber data sheets for details) are also equipped with a special design of corrosion resistant humidity sensor. This measures the relative humidity electronically inside the chamber and displays this at the HMI as %RH.
Test samples are accommodated within the chamber generally by placing on, or by suspending beneath, sample racks. A full set of sample racks are provided as standard with each new chamber (see chamber data sheets for quantity) in a choice of styles. Additional sample racks are available as optional accessories, if required, as is a reinforced false floor (ref; ACC19) for supporting large/heavy test samples directly on the chambers internal base.
During the condensation humidity mode of testing, this vent equalises any difference in pressure that might exist between the inside and outside of the chamber, due to expansion and contraction. It also provides a source of fresh air to the chamber to help ensure that an oxygen rich high humidity environment is created inside. The chamber should therefore ideally be located adjacent to an outside wall, and a hole made through the wall to accommodate the exhaust pipe (diameter varies depending on chamber model). The end of this pipe should be directed away from persons and property, and be shielded from wind to prevent any disturbance to the conditions inside the chamber.
A floor level drain is required to remove excess condensate etc. which accumulates over the internal base of the chamber interior.
The chamber is connected to a continuous pressurised water supply of suitable quality.
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