CCT Chambers - Condensation Humidity Mode - how it works
CCT Chamber - Condensation Humidity Mode
This mode of operation is provided as standard on all models of Ascott CCT chamber. It provides a facility whereby the chamber can be used to create condensation humidity conditions (fixed at 95 to 100%RH) at elevated temperatures (user adjustable up to +55°C/+131°F) and is designed to meet a wide range of international standards for such testing.
The control system fitted to Ascott CCT chambers enables the user to program whether condensation humidity is conducted alone, for tests such as ASTM D2247, or in sequence with other climates, to form a cyclic corrosion test, 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 set temperature required during condensation humidity testing is at least +10°C/+50°F 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 (user adjustable up to +55°C/+131°F), and at the same time raise the chamber humidity level to 95 to 100%RH. This fixed, 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, touch-screen, Human Machine Interface (HMI). It is here that the user controls and monitors the various chamber functions. The HMI incorporates alpha-numeric text messaging and digital displays of chamber variables such as temperature, humidity and time . Also included is a useful trend logging facility. This generates a graphical display of set values for temperature & humidity, over a 72 hour time period, and compares this to the actual temperature and humidity achieved inside the chamber, over the same period.
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. CCT chambers 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 to a resolution of 1%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. 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 to waste any excess condensate etc. which accumulates over the internal base of the chamber interior.
If access to a floor level drain is not possible or inconvenient, Ascott offer an optional accessory (ref; ACC20) comprising of a waste water trough and pump, which locates on the floor behind the chamber. Condensate from the chamber drain outlet is directed into this. When the holding tank becomes full, the condensate will automatically be pumped out by a marine specification pump. This will discharge waste water to a remote drain or effluent tank located up to 10M/30ft away horizontally and up to 3M/10ft vertically. ACC20 is not suitable for chambers fitted with the SO2 gas dosing optional accessory (ref; ACC46) due to the possible existence of H2SO4 in the condensate.
The chamber is connected to a continuous pressurized water supply of suitable quality.
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