CCT Chamber - ACC30 Salt Spray (vertically down) - how it works
CCT Chamber - ACC30 Salt Spray (vertically down)
This optional accessory comprises of a high level, multiple nozzle, salt spray rig, which sprays salt water directly down onto the samples under test. Spray time is adjustable and can be programmed to occur automatically at pre-determined point(s) during the test. The salt water is held in a separate holding tank, at ambient temperature.
The control system fitted to Ascott CCT chambers enables the user to program whether salt spray (vertically down) is conducted alone, or in sequence with other climates, to form a cyclic corrosion test, for automatic execution by the chamber.
Salt solution reservoir
An additional 200L (52 US Gal) free standing, salt solution reservoir, is provided with this optional accessory. This stores the salt water to be sprayed down, at ambient temperature. The reservoir is mounted on castors for mobility and incorporates a transparent graduated sight glass for ease of monitoring the solution level inside.
Salt solution pump
A marine specification salt solution pump is built into the CCT chamber. When required by the test program being run, this pump automatically delivers salt solution from the reservoir to the spray rig, at high pressure.
Multi-nozzle spray rig
Located high up on the back wall of the chamber is a spray rig which sprays salt water from a number of strategically located, fixed position spray nozzles (the number depends upon the chamber size). These nozzles generate a uniform spray pattern which covers the entire test area below. Test samples located in the test area will therefore be sprayed directly with salt water.
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 and 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.
This vents spent salt spray from inside the chamber to atmosphere. 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.
If access to an outside wall is not possible or inconvenient, Ascott offer an optional accessory called an Exhaust Salt Scrubber Unit (ref; ACC92). This comprises of a free standing enclosure, which should be located near to the chamber, and connected to the chamber exhaust vent outlet, a floor level drain and a continuous pressurised mains water supply. The unit works by directing the chamber exhaust towards its internal base, where a significant surface area of relatively cool liquid condensate/water is retained. The relatively warm salt laden exhaust passes over this and is simultaneously sprayed with a fine mist of cool water from a mains water sprayer located in the top of the unit. The combined effect of this is to condense and wash out the salt water droplets present in the exhaust, so that they combine with the retained liquid in the base of the unit. Surplus liquid is drained to waste from the base of the unit and the remaining 'scrubbed' compressed air from the chamber exhaust is allowed to vent from a port in the top of the unit. ACC92 is not suitable for chambers fitted with the SO2 gas dosing optional accessory (ref; ACC46) due to the toxic nature of the SO2 which may exist in the exhaust.
A floor level drain is required to remove used salt spray from inside the chamber to waste. 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.
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