4.7 Condensation humidity Salt spray IP chambers

Transcription

1 4.7 Condensation humidity Salt spray IP chambers Salt spray IP chambers perform condensation humidity (wetting) in a slightly different way to cyclic corrosion chambers. The manual base drain valve should be closed before commencing a test. The chamber base will automatically fill with water taken from the air saturator. (The outlet is a low level fitting in the wall of the chamber) The Immersion heating element is used to heat the water in the base of the chamber. Immersion heating element and float switches in chamber sump. (Cover removed) Two float switches are used in Salt Spray IP chambers. One is used to control the water level in the sump when filling from the air saturator. The second is used to detect when the sump needs to be refilled and as a safety measure to ensure that the heating element does not operate unless it is immersed in water. (In 120L chambers, the wrap around, base heating elements are used in condensation humidity mode. An optical sensor at the rear of the chamber is used to control the level of water in the base of the chamber.) 43

2 The chamber temperature probe (PT100) detects the chamber temperature, sending a value to the PLC. Power to the heating element is switched using a solid state relay controlled by the PLC. Note: During rapid heating (where a rapid change in temperature is required) the wrap around chamber heaters will also be active. This would be the case in single programs and in main programs where a 1 min step has been programmed. To turn this off so that the wrap around heaters are not used, create the required program using a ramped increase in temperature. 4.8 Controlled humidity Cyclic corrosion IP chambers Controlled humidity is effectively a combination of the condensation humidity and ambient air drying functions. During controlled humidity, the chamber sump will automatically empty of any condensate and fill up with fresh water. This ensures that the water being heated in order to generate humidity is not acidic as this could prove harmful to the humidity sensor. (This can be overridden to allow liquid to be retained in the base of the chamber for tests such as the SWAAT test) The air curtain, used to protect the humidity sensor automatically turns off during this mode. The water level in the base of the chamber is controlled by a ball cock in a small header tank located behind the front panel of the chamber. Depending upon the conditions within the chamber, any of the chamber heaters may operate. To increase humidity, the immersion heater used in the condensation humidity cycle is used. To decrease humidity, the heaters used in the ambient air drying cycle are used. It should be noted that the chamber may operate both functions at the same time. 44

3 Part 5 - Service & Calibration Ascott recommend that chambers are serviced and calibrated regularly. Typically, this would be on an annual basis. This allows the chamber to be checked for faults that may have developed and to help prevent them occurring. It ensures that the chamber is functioning correctly and keeps the chamber in good working order. Although Ascott chambers have a number of built in devices to detect if the chamber is not working correctly, it is not possible to cover every possible eventuality. Ascott provides a Service schedule to highlight the checks and work required during a routine service. This document can be amended and added to over time to include new checks or procedures. Servicing of Ascott chambers should only be carried out by suitably qualified personnel. 5.1 Portable Appliance Test. This is an electrical safety check, required in the UK that can only be carried out by suitably trained personnel. Although this may not be required, aspects of this test may be useful in determining if a chamber is safe to use following a fault or repair. (See the service schedule for details of checks carried out). 5.2 Calibration Procedures Calibrating chamber temperature: An independently calibrated temperature probe is placed inside the chamber test area at normal sample height. The corrosion chamber is allowed to stabilise at temperature until both the calibrated instrument and the chamber temperature display both reach stability. Once stable, calibration takes place. If required, any offset to the chamber display value for chamber temperature are adjusted accordingly Calibrating chamber relative humidity: An independently calibrated relative humidity probe is placed inside the chamber test area at normal sample height. The chamber humidity probe MUST have its protective filter in place! The corrosion chamber is operated until both the calibrated instrument and the chamber relative humidity display reach stability. 45

4 As the system is dynamic, and the stable control of humidity within a large volume is very difficult to achieve, true stability may be more easily achieved if the chamber is then stopped and the displayed values are allowed to settle. Once stable, calibration takes place. If required, any offsets to the chamber display value for relative humidity are adjusted accordingly Calibrating chart recorder or similar devices: These are calibrated in the same way as detailed above. Refer to the device manual (if available) for possible adjustments Calibrating chamber air saturator temperature: An independently calibrated temperature probe is placed inside the chamber air saturator so that the probe is immersed in the water within. (This is achieved by lowering the air pressure supplied to the air saturator allowing any fitting to be removed from the top of the saturator. The air pressure is then gently increased to allow some disturbance of the water within.) The air saturator temperature is allowed to stabilise until both the calibrated instrument and the chamber air saturator temperature display both reach stability. Once stable, calibration takes place. If required, any offsets to the chamber display value for air saturator temperature are adjusted accordingly Calibrating chamber air pressure: The chamber air pressure gauge is monitored and the indicated value is recorded. The air connection is then disconnected and placed into an independently calibrated pressure gauge. The gauge is held so that the face is vertical. Calibration takes place. It is not possible to offset the chamber pressure gauge. 46

5 5.3 Component and Functional checks Record Total Hours run: Allows a record of chamber usage to be maintained Check for compressed air leaks at solenoid valves: This is a check to ensure that solenoid valves are closing correctly. A solenoid valve assembly. Note: With the chamber switched off or idle, the solenoids can be manually operated or tested by pressing the small button on the top with a pen or small screwdriver. If solenoid valves are not closing properly, the chamber may continue to perform the function associated with that valve. Example: The chamber continues to spray salt fog after switching off. This would indicate that the Y3 / Y4 solenoid valve is not functioning correctly and are allowing air to pass through when they should be closed. Bubbling through the air saturator would indicate that the moist air solenoid (Y4) is not closing properly. No bubbling, would indicate that the dry air solenoid (Y3 is not closing properly Check Air pressure regulator and gauge function correctly: This refers to the air pressure regulator and gauge on the front of the chamber. Used during salt spray mode, this is often never adjusted by the customer so any failure may not be noticeable. Check that altering the air pressure regulator is matched by a change to the display on the gauge. Also check for signs of any leaks of moisture. 47

6 As the regulator and gauge are exposed to the moist air from the air saturator, they should be inspected for signs of leaks Check air saturator heater operating: As the customer sets the temperature once and then rarely needs to adjust this setting, it is possible that a fault could go undetected. Air saturator heating elements are very reliable indeed. Faults are usually attributed to poor water quality leading to the optical level sensors failing to detect the correct level of water within the air saturator sight glass. This can give rise to the chamber PLC failing safe and not sending a signal to switch on the air saturator heating element solid state relay Check Moist air/dry air operating: The default setting for salt spray testing is Moist air. This involves long periods of time where the moist air solenoid valve (Y4) is active. This can lead to it sticking in an open position. When the air saturator needs to refill with water, the chamber will automatically switch to dry air. The solenoid valve Y4 closes and solenoid valve Y2 (air saturator vent) opens. This allows the air saturator to de-pressurise as it fills with water. If Y4 does not close, the air saturator will continue to be pressurised, preventing it from filling correctly. This would result in an Air Saturator Low Water alarm. Check by switching between Air saturator active (moist air on) and Air saturator inactive (dry air). Pushing the manual buttons on the solenoid valve can help shift a sticking solenoid. 48

7 5.3.6 Check Pump speed control operation: During salt spray testing the peristaltic pump is used to regulate the flow of salt solution supplied to the atomiser. Once set, the pump speed rarely needs to be adjusted. Check the function by briefly setting the pump speed to a higher value to see a corresponding change in the speed of rotation of the pump rotor. The pump speed is controlled by a signal from the PLC. The PLC sends a frequency signal to a special module (IAG Unit) that converts this frequency to a voltage. This voltage would be 0-24VDC. At 24VDC, the pump will rotate at its maximum speed (40rpm). A pump motor can be checked by connecting it to a 24VDC supply. The IAG unit has an indicator (PWR) that illuminates to show that it is on. A second indicator pulses when it is operating Check individual wall heaters by hand: Ascott chambers have flexible silicone heating elements bonded to the outside of the floor of the chamber. These have proven to be incredibly reliable; however a simple check is worthwhile. Open the canopy and touch the floor of the chamber to ensure that there are no cold spots which would indicate a heater not working. If a heater is found to be faulty, check the solid state relay for that heating element. If this is not faulty, disconnect the faulty heating element to make it safe. Replacement is possible but may not be required if the chamber is able to heat up and operate to the required specification using the remaining heating elements. 49

8 5.3.8 Check temperature controllers function & control correctly: Ascott chambers use a number of settings and PID terms to control the temperature and humidity within the chamber. If these settings are lost or altered, the chamber could suffer from a loss of control. This could happen if an internal battery fails and the chamber is switched off for a long time. Replacement batteries can be fitted and PID terms can be reinstalled (Contact Ascott for advice) Check Purge outlet not blocked by salt: On salt spray chambers the purge outlet is a small aperture in a plastic fitting. This can, over time, become blocked by salt crystals, particularly if the chamber has been switched off having not been cleaned. Unblock with a sharp implement and by operating the purge facility. (On cyclic corrosion chambers, the purge outlet is the square shaped inlet on the chamber wall. It should not be blocked or restricted in any way.) Check HMI battery condition (IP chambers only): Ascott chambers have in built warnings if the HMI battery is in need of replacement. A message will be displayed on the HMI. Battery life will depend upon chamber use and ambient conditions. (High ambient temperature and humidity may reduce battery life.) Turn the power supply to the chamber OFF. Replace the HMI battery by opening the small cover on the rear of the HMI. 50

9 Check PLC battery condition: Ascott chambers have in built warning if the PLC battery is in need of replacement. A message will be displayed on the HMI. Battery life will depend upon chamber use and ambient conditions. (High ambient temperature and humidity may reduce battery life.) Turn the power supply to the chamber OFF. Replace the PLC battery by opening the small cover on the rear of the PLC Check/clean water inlet solenoid: Although customers should use deionised water, not all do. Algae, contaminants, and crystals from the deionising system can build up at the water inlet filters eventually leading to blockages. Blocked inlet solenoid valves can result in low water alarms associated with the air saturator and the humidity generation system. To check, turn off the water supply to the chamber at the mains. Slowly unscrew the water inlet fittings using a cloth to absorb any water that remains pressurised within the hose. Check and clean the rear of the solenoid valve. Water inlet solenoid filter. (Hose connection removed). 51

10 Check for blow back in water inlet line (air saturator): Water supplied to the air saturator passes through a non-return valve. This is to prevent a pressurised air saturator from inadvertently pressurising the mains water supply. This can be seen as bubbles will be visible inside the transparent hose that supplies the air saturator with water. If suspected, remove and check the non- return valve and replace it if required. Air saturator water inlet none return valve (NRV4). Allows water to pass into the air saturator but prevents air from getting back into the water supply Check Moist air outlet check valve: The moist air non-return valve (NRV2) allows compressed air to flow from the air saturator to the atomiser but prevents the air saturator from being pressurised during dry air. This would prevent the air saturator from filling with water when required. Air saturator moist air outlet non-return valve. Check by removing from the air saturator and inspecting internally for signs of contamination. Air should pass from the air saturator but not back into it. An arrow on the side of the valve indicates the direction of flow. 52

11 Check Pressurise air saturator non-return valve: During salt spray testing, air passes through a non-return valve before entering the base of the air saturator. This valve prevents any moisture from getting back to the solenoid valve assembly. Air saturator air inlet non-return valve. Remove from the air saturator and inspect internally for signs of contamination. (Take care as water will flow from the hose) Air should pass into the air saturator. A symbol on the side of the valve indicates the direction of flow. On salt spray IP chambers, an additional non-return valve is fitted near the top of the air saturator. During condensation humidity testing, compressed air is fed into the air saturator to pressurise it allowing the water to be pushed out into the chamber base. This non-return valve prevents moisture from getting back to the solenoid valve assembly. Air saturator pressurise (base fill) non-return valve. Check by removing from the air saturator and inspecting internally for signs of contamination. Air should pass into the air saturator. A symbol on the side of the valve indicates the direction of flow. 53

12 Check moist air solenoid valve for contamination: The solenoid valve assembly is a high quality, reliable component. Exposure of the internals to moisture can lead to problems with the solenoid valves sticking. In some cases, the solenoid valve or assembly may need to be replaced. Ascott chambers have a number of non-return valves and a filter to help prevent contamination of the solenoids with water. If a fault occurs with any of these, the solenoid valves should be inspected for signs of water ingress and internal corrosion. Pressing the manual override button (chamber off) will test the solenoid valves. Individual segments can be removed and inspected internally. If found to be faulty it is advised to replace the entire assembly after identifying and rectifying the cause Check for oil in air lines: Check for signs of water/oil in pneumatics/water filter: Ascott chambers MUST be provided with clean, dry, oil free compressed air. A 5 micron filter is fitted to the rear of every chamber to remove any moisture that may be present in the air supply. The base of the filter has a small nut that vents any moisture that gathers inside. 54

13 Oil contamination of the air supply will prevent the filter from working correctly. This could lead to oil or water getting into the pneumatic system which could damage the solenoid valve assembly. The white filter medium can be replaced if required Check function of over temperature thermostats: Ascott chambers have a number of 0-120C variable thermostats fitted. These provide protection against over temperature conditions and may give rise to alarms when operated. They are a vitally important safety feature. Each thermostat has a white dial with a screw to prevent the thermostat from being adjusted incorrectly. To check that a thermostat is functional, loosen off the dial fixing screw and rotate the dial. When the thermostat trips there will be an audible click from the dial. If the chamber is on, an alarm may sound. The switching point of the thermostat is in line with the centre terminal. As the dial is rotated, the thermostat will trip when the value on the dial (nearest the centre terminal) matches the actual temperature detected by the thermostat. If no click is heard, the thermostat must be replaced. This shows two thermostats located behind a rear access panel. O/T 1 is set to trip at 80C O/T 7 is set to trip at 120C. 55

14 Check/clean flow meter: The salt solution flow meter gives an indication of the flow rate of salt solution to the atomiser during salt spray testing. The small ball will rise and fall in conjunction with the rotation of the peristaltic pump motor. The flow meter is a restriction in the flow of salt solution to the atomiser. As such, any contamination can quickly lead to blockages. It is fixed to the chamber wall with two screws. These should NOT be over tightened. The flow meter can be cleaned by inserting a bent cable tie or similar to be used to loosed any deposits inside. The flow meter cap can be removed. Take care not to lose the small ball inside. Do not over tighten the cap when refitting as they can be broken. 56

15 Change salt hoses: Ascott chambers are fitted with blue salt solution hoses. These hang free inside the chamber in order to prevent the hoses from folding, causing restrictions and to allow easy replacement. Although no light can pass into the hose, it is still possible for algae to grow within the hose. Also, the hose may become hardened over time, potentially leading to leaks or the ingress of air into the system. This would affect the flow of salt solution and therefore the salt fog distribution within the chamber. Disconnect and replace the salt solution hose in stages to avoid making a mistake when replacing the hose. (Rear of flow meter connections shown) Change peristaltic pump tubing: The user should be replacing the peristaltic pump tubing periodically. It is best that this is also replaced during a service visit as this also allows the tube connections and pump to be examined at the same time. Check that the pump rotates freely. It should be possible to turn the rotor easily by hand. 57

16 The rotor can be tightened if required Change salt filters and clean salt filter housing: Clean/adjust atomiser: The user of the chamber should be cleaning/replacing the atomiser filter on a regular basis. Details can be found in the chamber instruction manual. During a service, this filter should be replaced and the atomiser checked for signs of damage and for good function. Atomiser salt in Luer fitting assembly Atomiser Body & filter spacer Compressed Air Inlet Hose & Atomiser air in Luer fitting assembly Atomiser Cap Salt Solution Inlet Hose Salt solution Filter Housing (filter fitted) Plastic spacer Atomiser Nozzle 58

17 The effectiveness of an atomiser can be checked with the canopy open and the chamber operating in salt spray test mode. Remove the salt supply line from the bottom of the atomiser and place the open salt filter into a cup of clean water. The atomiser should draw the water through the filter to create a strong plume of fog. If this does not happen or if the atomiser blows bubbles back into the cup, inspect the atomiser for damage or blockages Check, tighten braided hose connections: 12mm internal diameter braided hose is connected to hose connections using hose clips. Over time, the hose can harden and connections can develop small leaks. Check that hose connections are not leaking and are secure. Pay particular attention to optional accessories that may not be in constant use Check air saturator safety valve is not leaking: The air saturator is fitted with a pressure release valve. This is not adjustable and is designed to release at 2.5bar. Locate the safety valve on the air saturator. (Shown here with plastic tubing removed). During salt spray testing, it should not leak. Reset by lifting & releasing the small nipple until it stops venting air. With chamber operating in salt spray mode, open the front regulator to maximum 59

18 Locate regulator PR1 (hoses P1/P2 connected) Adjust until pressure gauge on the front of the chamber is at 22psi. Lock the regulator PR Drain Air Saturator: The air saturator and its components can become contaminated during use. This could be due to poor water quality, poor air quality or the build-up of algae. Turn off the water supply to the chamber. Set the chamber to salt spray in dry air mode and open the air saturator drain valve on the rear of the chamber. Use a suitable vessel to capture the water. Open the air saturator drain using a flat bladed screwdriver to open the valve. Be careful to close the valve when the air saturator has emptied! 60

19 Remove, clean air saturator sight glass: (Chamber turned off) Do not disconnect the optical sensors connected to the sight glass. They can be removed from the sight glass while leaving their electrical connections intact. Optical sensors are held in place using cable ties. These can be cut, to allow the face of the sensors to be cleaned. To prevent fitting in the wrong order, remove and replace each sensor individually. Refit with new cable ties. The sight glass can then be cleaned internally using a long, narrow bottle brush, or by pushing a wad of tissue paper through it, having previously removed the pneumatic fittings at each end. (Shown removed from chamber for clarity) Refill air saturator checking the function of all optical sensors: With the mains water supply turned on, turn the chamber on. The air saturator will automatically fill with water. (An alarm will also sound) As water fills the air saturator, the sight glass will also fill. The optical sensors will show an illuminated red LED when no water is detected. The LED will turn off as water passes through. The air saturator will stop filling when water reaches the top sensor. 61

20 (When replacing these sensors be sure to set the small dip switches to be exactly as the original sensor) Check for any leaks at the pneumatic connections during a short period of salt spray testing Check pneumatic cylinders hold canopy stable when open: The chamber canopy is held open pneumatically. It should be stable when fully open and should not start to close without user input. If the canopy does start to fall, check that the compressed air supply to the chamber is sufficient (4-6bar) before checking for pneumatic leaks in the air supplied to the pneumatic cylinders Check canopy for function and leaks: This check is to ensure that when closed, the canopy provides a good seal in order to prevent the conditions within the chamber from escaping. If the canopy lifts, check for a restriction in the chamber exhaust system. Check the canopy gasket for signs of damage or the build-up of salt deposits. A flattened, canopy gasket is not necessarily a problem providing that it is kept clean and creates a seal between the chamber and canopy. The position of the canopy is monitored by the chamber PLC using two sensors: The position of these should not need to be adjusted in normal use. A canopy open sensor on the top of a pneumatic cylinder. Only one will be fitted on the cylinder at the control compartment end of the chamber. 62

21 The canopy closed sensor on the front face of the chamber Check canopy hinges for signs of corrosion and oil as required: Ascott chambers are fitted with stainless steel canopy hinges. Light periodic lubrication is the only maintenance required Check canopy cylinder brakes: 1000L and 2000L chambers are fitted with pneumatic brakes on the cylinders used to operate the canopy. These brakes require air pressure to operate and in turn allow air to pass through. If the air supply to the chamber is suddenly lost, the canopy cannot close by accident. With the canopy open, turn the chamber off and turn the air supply to the chamber off. Disconnect hose P1 from the cylinder brakes, or at any connection. (Air will escape) The canopy should not close. If the canopy closes, the cylinder brakes should be checked and replaced if found to be faulty. 63

22 Check for any leakage to drains including through plastic ball valve: This check is primarily to check for signs of solution leaking from the chamber onto the floor of the laboratory. As the chamber is moved, drain connections can work loose between the chamber and the laboratory drain. In addition, leaks from the chamber components can lead to problems with heating elements and corrosion of the chamber itself. When inspecting the drains, pay particular attention to the area around the sump and immersion heating element. Any leaks must be dealt with as the leaking water will be corrosive and will lead to further problems. The check also covers the function of the drain valve. On salt spray chambers, this is the manual drain valve. On cyclic corrosion chambers, this is the automatic, pneumatically actuated drain valve. On salt spray chambers, check that the manual drain valve is able to open and close fully and that when closed, water does not drain. Pneumatic drain valve on a cyclic corrosion chamber. Note the white tab on the top at 90 degrees to the direction of flow, indicating that the valve is closed. 64

23 Clean base water level sensor & check that it operates correctly: Check that the float switches in the chamber sump are clean and able to operate properly. On 120L chambers, this is the optical sensor located in the base of the chamber alongside the drain outlet. Immersion heating element and float switches in chamber sump. (Cover removed) If not kept clean, the corrosion waste can build up on the float switches creating a sticky paste. This eventually stops the float switches from moving. This can lead to substantial damage within the chamber! This can be removed using a soft brush Check main program function: Chambers are typically used to perform one test standard, usually salt spray ASTMB117 or similar. It is important to check that other programs operate properly and that the chamber changes automatically from one function to another. Install a main program to test that the chamber changes functions properly. Pay particular attention to base draining and filling as required. 65

24 Check humidity sensor assembly: The humidity sensor is a delicate instrument and is often overlooked by the user, particularly when the chamber is operating in modes that do not require relative humidity to be monitored or controlled. There is a known degradation over time of ALL manufacturers humidity probes if they are exposed to humidity levels above 90%RH. Humidity probes should be considered a consumable item and should be considered for replacement on an annual basis. This is particularly the case in chambers that operate at levels ABOVE 90%RH as part of any test procedure. Filter cap unscrews from sensor to reveal electronic sensing element inside. This filter can be removed for cleaning or replacement. In either case, the cabinet must not be operated until the filter has been correctly screwed back into position (finger tight only). Check that the humidity sensor element for signs of corrosion. Check that the Process Value (PV) for humidity changes on the HMI and that the display is as expected. Typically, the sensor filter will be saturated with moisture if the chamber has been used for salt spray testing. Set the chamber to perform a high temperature, air drying test. This will dry out the filter cap and lower the relative humidity inside the chamber. (Remember to open the drain valve on salt spray IP chambers in order to lower the RH within the chamber). The delicate sensor element should only ever be cleaned using a can of dry compressed air such as duster gas. Under no circumstances should it be scratched or rubbed. Avoid contact with finger tips. If the sensor element is seen to be corroded or damaged in any way it should be considered for replacement Check condition of pneumatic hoses: Ascott chambers are fitted with high quality, nylon, pneumatic hoses that can withstand the passage of warm compressed air containing deionised water. (Moist air 66

25 during salt spray). Over time, usually many years, the ends of the hoses, where connections to pneumatic components are made, can become hardened. This can lead to minor leaks within the chamber. Check the ends of the hoses and trim the ends or replace the hoses as required. Pay particular attention to pneumatic hoses connected to the air saturator. It should be noted that pneumatic hoses should not be replaced with other lower grade hose. This may degrade quickly leading to leaks of compressed air/moisture Check alarm record and note frequent alarms: This is useful for identifying potential problems with the chamber or how it is being used. For example: Air saturator water low alarms may indicate that there is a problem with the water supply to the chamber, or that the air saturator is not filling correctly. Frequent Power failure during run alarms could indicate that there is a problem with the power supply or that tests are being stopped by switching the mains isolator off. Over temperature alarms could indicate that the humidity sensor cap is blocked with salt deposits Check Immersion Element terminals Remove the cover from the immersion heating element and check for signs of leaks. Also check for degradation of the terminal connections and ceramic insulation materials. 67

26 Cyclic Corrosion chambers Header Tank: Inspect humidity header tank and clean if required: Remove the cover from the header tank to inspect / clean the inside. Note: the level of water in the base of the chamber during humidity modes is controlled by the position of the float inside this tank. Raise the float to increase the level of water, lower it to reduce the level. If changes are made, test a few times to see the base drain and fill to the required level Check humidity function and base fill: (this also applies to salt spray IP chambers) Cyclic corrosion chambers fill the base, through the drain system with water supplied from the header tank. Salt spray IP chambers fill the base using water from the air saturator. Check that the chamber automatically fills to the required level and that the heating element (or base heater for SS120IP chambers) operates Salt spray function: Check that the salt spray function operates correctly. (Largely covered in earlier aspects of the service schedule) 68

27 Air drying function including base drain and blower assembly: Check that the base drain valve opens and remains open. Check that the variable speed fan operates. (There may be a delay of 20 seconds) Check that the heating element attached to the fan heats up. (It may glow initially). Check that the ball valve opens. (Ball valves are fixed in an inverted position) When open, the red, closed flag will change to a yellow open flag Check controlled humidity function: 69

28 Having checked the condensation humidity function and the drying function, controlled humidity should now prove to be functioning normally. Check that the variable speed fan operates correctly when high humidity is required. Briefly start a controlled humidity test with a higher than actual set value for humidity. Verify that the chamber base fills with water and that the fan starts and runs at low speed. Refer to the chamber functionality section of this manual for details on checking the fan is operating correctly Check the 50mm hose at the ball valve/fan for signs of damage: The 50mm hose is designed to withstand high temperatures and the steel reinforcement is completely encased in rubber to prevent corrosion. However a visual check of this hose should be made as any degradation may affect performance of the chamber Check ball valve connections are secure but not over tight: The 50mm hoses connect to the ball valve with knurled rings that tighten onto the ball valve mechanism. An o ring seals the connection. These should not be over tightened as this can put strain on the ball valve actuator Check ball valve function BV1 & BV2: As above, check that the ball valve(s) open and close as they should. They should open during a purge or dry test and should close completely during salt spray testing. Pneumatically actuated ball valves are known to be very reliable but the following is a worthwhile check. Disconnect one hose connection to the ball valve and check that the ball inside the valve closes COMPLETELY during salt spray testing. The valve protects the fan and heating element from salt contamination. 70

29 Check blower heater internals for signs of corrosion: If the ball valve is suspected to be faulty, the result would be corrosion of the heating element within the fan assembly. It is also possible that external conditions, can be drawn into the heating element. It may be possible to see inside the casing through the fan outlet. Alternatively, the heating element housing would need to be opened to inspect the element inside. A new blower (fan) assembly heating element. Note that the coils are supported and do not sag. A new blower (fan) assembly heating element viewed through the outlet from the heater casing. 5.4 Consumables spares kit Ascott Ref. No.: ACC12/C A kit of consumables parts for an Ascott salt spray or cyclic corrosion test chamber. Sufficient for up to 1 year. These may be offered for sale to the customer at any time. Many will purchase this at the same time as ordering a service or it can be sold during the service visit.. 1m x PERC012 Silicone Tube 2pk x SALC010 - Salt Filter Wadding 1pk x ELEC690 - Cable Ties 71

30 ATOA110 - Atomiser air in luer fitting assembly ATOA120 - Atomiser salt in luer fitting assembly SALC012 - Salt Filter Housing Tube 72

31 Customer Name: 5.5 Ascott approved service checklist Chamber Serial Number: X=N/A Portable Appliance Test (if ordered): Check appliance casing for damage Check mains cable & plug Check point of cable entry Check mains switch Check chassis continuity Conduct Earth Bond, test & record...(<0.5w) Conduct Class 1 or 2 insulation test & record...(>2mw) Apply tested for electrical safety sticker Calibration (if ordered): Calibrate air temperature controller & RH sensor Certificate Number:.. Calibrate chart recorder (if fitted) Certificate Number:.. Calibrate air saturator temperature controller Certificate Number:.. Calibrate Air pressure gauge Certificate Number:.. Apply calibration stickers Component & Functional Checks: Record total hours run.h. Check for compressed air leaks at solenoid valves Check air pressure regulator & gauge function correctly Check air saturator heater is operational Moist/dry air Check pump speed control operation. Check individual wall heaters (by hand) to verify they are all heating Check temperature controllers function & control correctly Purge - Check purge outlet into chamber not blocked by salt Check HMI battery condition, replace if required. (3 yr interval) Check PLC battery condition, replace if required. (3yr interval) Check/clean water inlet solenoid valve filter on autofill chambers Check for blowback in water inlet line on auto fill chambers Check moist air outlet non-return valve for lime scale deposition and change if necessary Check pressurise air saturator non return valve Check moist air inlet solenoid for internal contamination and change if necessary Contact: Date of Service: Check for oil in air lines, changing if necessary Check for signs of water in pneumatics/function of water filter. Check operation of over temperature thermostat(s) Check/clean flowmeter Change salt hoses. (Check for any evidence of leaks before & after) Change peristaltic pump tubing & check for any slackness in rotor or rotor shafts, oil if satisfactory Change salt solution filters & clean salt filter housing Clean /adjust atomiser Check/tighten braided hose connections Check air saturator safety valve is not leaking Drain air saturator and: Remove, clean & replace air saturator sight glass Refill air saturator checking operation of: ALL level sensors Check pneumatic cylinders hold canopy stable when open and oil if necessary Check canopy for function and leaks Check roof hinges for signs of corrosion, oil as required Check canopy cylinder brakes operate correctly if fitted. Check for any leakage to drains including through plastic ball valve Clean Base water level sensor & check that it operates correctly Check Main Program function Check humidity sensor assembly Check condition of pneumatic hoses Check alarm record & note frequent alarms * *Recorded alarms : Check Immersion Element terminals Cyclic Corrosion Chambers Only: Inspect humidity header tank and clean if required Humidity function inc auto base fill. Salt spray function Air drying function inc auto base drain & blower motors Controlled humidity function inc auto base fill and blower motors Check 50mm hose at ball valve for damage. Check ball valve hose connections secure but not over tight. Check Ball valve function BV1...BV2... Check Blower heater internals for corrosion Check additional functions 73

32 Part 6 - Service Action Points This section provides supplementary information on issues that may occur in Ascott corrosion chambers. Detailed below are symptoms, causes and solutions to problems that have occurred. Additional information can be found on the Ascott website, Chamber Doctor facility. Chamber Doctor has two levels of access. Customers can access details specific to the type of chamber they own. (Free of charge within warranty period) Engineers can access details for all chamber types. To log in as an engineer, you will need a specific login card from Ascott. The Password is card specific. The login number will also be unique. Once logged in as an engineer, follow the on screen prompts. 74

33 6.1 PLC Monitor (IP chambers) Within the SETTINGS menu (1234) touch the to access the screen shown below. This is a pictorial view of the Programmable Logic Controller (PLC). This page can be useful for determining what the chamber is doing and may be used to verify PLC input and output signals. Touching any of the modules will bring up a screen specific to that module. Inputs and outputs will illuminate with an orange background when they are active. 75

34 6.2 Humidity sensors (IP chambers only) Symptoms: Humidity PV (Process Value) is fixed and never changes. Alarm condition -Chamber over-temperature. (Controlled humidity function) Poor transition times between conditions. (Controlled humidity function) Any or all of these symptoms would share the following causes & solutions. Cause 1: Contamination of the humidity sensor cap. Over time, salt and dirt deposits can block the PTFE filter on the humidity sensor cap. Solution 1: The sensor/cap should be examined and cleaned on a regular basis. See section 3. Cause 2: Humidity sensor/ sensor assembly is corroded or damaged. -This is usually due to poor maintenance or physical damage. Solution 2: The humidity sensor assembly will need to be replaced. - See Chamber Doctor for instructions, which are also supplied with replacement assemblies. 76

35 6.3 Humidity Header Tank (CC IP chambers only) Symptom: Alarm condition Humidity low water. (Water present in sump) Alarm condition Humidity low water. Persistent alarms, that clear with no apparent cause. Poor control of humidity and water overfilling chamber sump (Controlled Humidity function). (In condensation humidity mode, the sump over-fills.) Cause 1: Water level in sump is too low. As water boils the float switch in the sump bounces causing an alarm. Solution 1: Ball cock valve within the header tank needs slight adjustment so that when fully closed, the water level in the base of the chamber fills to the top of the sump. Rotate the central pin to raise/lower the float. Test the system by draining and filling a few times to see that the sump is filled to the top edge. (Select wetting, then stop and open the drain valve) 77

36 Cause 2: Contamination of the humidity header tank. Algae growth within the header tank can lead to the ball cock mechanism inside sticking in a closed position. (Algae forms a skin on the surface of the water that will hold the valve closed. As the level of water drops an alarm occurs, but the sump does not fill. After a short time or after flushing the drains, the algae releases the valve which now works correctly) this has been noted in SWAAT chambers which can be prone to algae growth. Solution 2: Clean and sterilize the header tank. This can be performed by draining the chamber and then filling the sump with dilute sterilising solution. Water will flow back from the sump to the header tank. Allow 30 minutes before draining and flushing with water. Cause: Contamination or damage of the header tank ball -cock valve. Damage or dirt within the ball cock mechanism can prevent it from closing effectively. The result will be a permanent feed of water to the header tank and chamber. The chamber base over-fills with water during humidity modes. Normally during humidity modes, water should fill the sump to the top and stop. Solution: The ball cock valve should be carefully disassembled, cleaned and refitted. Test by manually closing the valve when water is flowing. Water should stop flowing. If cleaning does not resolve the problem, the valve mechanism should be replaced. In Addition, it is possible for a restricted exhaust system to cause humidity low water alarms. This is easily overlooked. During controlled humidity air is blown into the chamber. A blocked exhaust will allow the pressure inside the chamber to increase. This can lead to the water level dropping and the float switch opening, giving rise to an alarm. 78

37 6.4 Air Saturator Sight Glass Symptom: Chamber will not start testing (pump does not rotate) Water squirting from atomiser (air saturator overfilling) Air Saturator failure- catastrophic! Any or all of these symptoms would share the following causes & solutions. Cause: Sight glass contamination. All of the above symptoms can be caused by contamination of the water within the air saturator. This leads to deposits forming on the surface of the air saturator sight glass. The optical sensors fail to detect changes in the water level. Sight glass contamination. Algae contamination of sight glass will lead to blockages preventing the sight glass from filling and emptying properly. Draining and flushing with fresh clean water only. Do not use any chemicals! Contamination can come from the water supply itself. It is extremely important that the water is de-ionised and that the de-ionising system is regularly maintained. As the air saturator has compressed air passed through it; it is possible for the incoming air to contaminate the water. 79

38 Solution: The sight glass should be cleaned as described in the service section of this manual. The air saturator water should be drained and flushed, to remove deposits. In extreme cases, the air saturator may need to be removed from the chamber to be thoroughly cleaned. 6.5 Drain system blockages Symptom 1. Humidity Low Water Alarms 2. Chamber over temperature alarm 3. Melted sump cover Cause: Contamination of drain system and/or float switches Solution: Clean and flush the chamber base of waste products. Waste should be scooped out rather than flushed through the drain system. Drain system contaminated with algae/corrosion deposits will lead to float switch malfunctions and humidity system failures. The picture shows a salt spray ip chamber (also SS+ or SSxp) There is a risk of heating elements remaining on when no water is present! 80

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