Sanyo 550 User Manual

SANYO GALLENKAMP

ENVIRONMENTAL CHAMBER

INSTRUCTION MANUAL

Customer Programming system

Cabinet model supplied: Cabinet reference: Handbook date: Handbook reference:

B. de Ronde

Format 550 Programmer HCC065.PF4.J 7904

July 1994 SG7904/Z01456

CONTENTS PART ONE - THE CABINET

Section

5 6

INTRODUCTION

Health & Safety at Work

1.1

Commissioning (U.K. Customers only)

1.2

Sanyo Gallenkamp service & maintenance facilities

1.3

GENERAL DATA

2.1

Specification - Physical Specification - Performance

2.2

Optional facilities

2.3

Format 550 digital channels

2.4

DESCRIPTION

3.1

Principle and airflow Temperature control

3.2

Relative humidity

3.3

INSTALLATION

4.1

Accessories & spares Positioning

4.2

Ambient temperature

4.3

Power supply

4.4

Mains interrupt bridge

4.5

Drain

4.6

Distilled water supply

4.7

Wet wick(s)

4.8

Test load protection

4.9

4.11

Cable port

4.12

Vent Glass inner door

4.13 RS232 connector

4.14

OPERATION MAINTENANCE

6.1

Maintenance schedule

6.2

Maintenance methods

APPENDICES Parts list Recirculating pure water system - optional facility

FORMAT 550 CONTROLLER OPERATING INSTRUCTIONS

Full instructions for operating the Format 550 controller are given in the second part of this manual. The contents list is provided at the beginning of that part

INTRODUCTION

Great care has been taken in the specification, design and manufacture of your cabinet, to provide a system that will give long dependable service.

This handbook is an integral part of that policy. Please use it to help you obtain continued good performance and reliability. If it fails, please let us know.

1.1.

Health & Safety at Work

Section 6 (4) of the above act requires manufacturers to advice their customers on the operating and handling precautions to be observed when installing, operating, maintaining and servicing their products. Accordingly, the following points should be noted.

The relevant sections of these instructions should be carefully read before proceeding.

Intallation, maintenance and servicing should only be carried out by suitably trained

personnel.

Normal safety procedures must be taken to avoid the possibility of an accident occur-

ring.

1.2. Commissioning (U.K. Customers only)

If required, we can arrange for one of our engineers to commission the cabinet In many cases this is not necessary but should you feel that his services are required please telephone us at Loughborough to make the necessary arrangements. During his visit our engineer will run the cabinet and check that its systems are functioning correctly.

Take advantage of the commissioning visit to ensure that your staff are fully acquainted with the cabinet and its operation.

1.3. Sanyo Gallenkamp service & maintenance facilities

Sanyo Gallenkamp's Service Engineers and their colleagues have many years of experience in this equipment This expertise is readily available, either as diagnostic advice or on-site attendance.

Sanyo Gallenkamp Service Department operates nationally from our Loughborough factory, where all stocks of spares are held. In addition to training of customers own engineers for first line maintenance, we offer:

Extended warranty (2 years)

Contract maintenance schemes

24 hour response/call out

A loan or hire of units can be arranged in circumstances where an immediate repair is not possible.

CABINET DATA

2.1.

SPECIFICATION - PHYSICAL

model size 90 195 310 600 650 1100 2000

Internal working dimensions (mm):

width 450 650 680 650 900 1100 2000 depth 450 500 650 650 900 1000 1000 height 450 600 700 1400 800 1000 1000

External dimensions (mm):

(excluding protrusions) width 1144 1304 1334 1320 1554 1904 2654 depth 710 840 990 850 1240 1340 1340 height 113 1730 1875 1960 1975 1845 1975

Capacity (litres): 90 195 310 600 650 1100 2000

Shelf loading maximum kg: 10 10 15 10 20 30 30

Cabinet loading maximum kg: 30 30 45 50 60 90 90

Distilled water usage litres/hr: not specified

Gross weight approx kg: 180 280 310 320 360 750 900

Electrical requirement:

as stated on the cabinet rating plate (380/440V 50Hz 3ph or 216/264V 50Hz lph)

Refrigeration gas: CFC - free

2.1.1 Construction Interior

High quality stainless steel welded and vapour sealed.

Exterior/finish

Zinc coated mild steel with a staved acrylic, textured finish. The interior surfaces of

the mild steel are protected with rubberised paint and sealed against the ingress of

moisture.

Insulation

Minimum of 75mm of polyurethane foam/glass wool.

Access

Full sized insulated outer door with silicone rubber seal.

If fitted, full sized inner glass door with silicone rubber seal.

One or more 66mm diameter silicone rubber cable entry port in left hand wall.

Shelf

One solid stainless steel shelves with three shelf positions.

All models have a double skinned working chamber base which can be used for test samples.

False roof

Provided to prevent condensate droplets from falling on the test samples.

Castors

Nylon castors are fitted to floor standing models; front castors are lockable.

Drain

Provided for drainage of excess moisture.

Vent

Provided in the rear of the cabinet to allow for expansion and contraction during temperature changes.

Can also be used, in conjunction with the cable port, to provide air exchange to prevent the build up of humidity or contaminating gases from test samples.

2.2.

SPECIFICATION - PERFORMANCE

Model reference CF1

Temperature range: -10°C to+180°C

models HCC009.CB1 and HCC060.CF1 have a T°max of 100°C

Temperature rise rate Temperature fall rate Temperature fluctuation (with time) Temperature variation (gradient) Humidity range % rh

Humidity fluctuation (with time) at max rh:

at min rh:

Air velocity (average, empty working chamber)

Tolerated cabinet loadings to maintain specified performance

CF4

-40°Cto+180°C -70°C

not specified not specified

0.3°C

1.0°C 20°C 30°C 50-95 30-95

3%rh

5%rh

0.2 m/sec (turbulent)

CF7

to +180°C

60°C

15-95

Static load (ie the test load): not specified Dynamic load watts (ie dissipating loads): not specified

Fluctuation is the maximum difference (temperature or humidity), measured at the chamber centre, over a period of time, after the cabinet has reached stability.

Variation is the maximum temperature difference, at any time, between the centre of the chamber and the extremes of the working envelope.

2.3.

OPTIONAL FACILITIES

Where optional facilities are fitted to the cabinet instructions for their use, if necessary, are detailed in the appendices of this manual. Alternatively, additional information sheets are inserted in the front of this manual.

2.4. FORMAT 550 DIGITAL CHANNELS

The Format 550 programming system fitted to the cabinet has the following digital channel functions. A number of the channels are for the control of the cabinet and are

usually automatically selected on or off by the programmer as required to achieve particular conditions. If applicable, other user designated channels are also detailed below. All digital channels are shown on the monitor and program screens of the Format 550 programmer.

Full operating instructions for the Format 550 programmer are given in Part 2 of this manual.

DIGITAL CHANNEL 1 COOLING (MAIN) *

SYSTEM CHANNEL

This channel switches the main cooling mode on (see section 3.2). The main cooling mode is used to:

a) enable programmed temperature pull down from +70°C, ie: the fall rate is controlled. b) enable freejall temperature pull down from the cabinet's maximum temperature, ie:

the fall rate is as fast as possible.

c) enable temperature dwells below +40°C (auxiliary cooling is used between +40°C

and +15°C if high humidity control is required).

d) extract heat dissipated from the test load between +70°C and the minimum operating

temperature.

e) enable the cooling coil's low surface temperature to dehumidify the cabinet between

+5°Cand+70°C.

DIGITAL CHANNEL 2 COOLING (AUXILIARY)

SYSTEM CHANNEL

This channel switches the auxiliary cooling mode on. The indirect cooling mode is used

to: a) control temperature dwells with high humidities between approx. +15°C and +60°C. b) extract heat dissipated from the test load during temperature dwells. The capacity of

the auxiliary cooling mode to extract heat from the test load is limited.

DIGITAL CHANNEL 4 HUMIDIFIER (VPG)

SYSTEM CHANNEL

This channel determines when "steam" injection from the vapour phase generator system is available to the program controller.

This channel is always enabled when a humidity setting is programmed into the Format 550 programmer.

DIGITAL CHANNEL 8 VOLTAGE FREE TERMINAL (VFT)

USER PROGRAMMABLE CHANNEL

This channel enables the switching of external devices, such as measuring equipment, and the test load.

The system comprises of a voltage free termination of the programmer's digital channel number 8 which is wired through the cabinet's safety thermostat The final termination is a socket on the side or rear of the instrument compartment (a suitable plug is provided). The termination is rated at 240v 5A maximum and requires a suitable circuit for switching higher current loads.

Program this channel ON whenever the voltage free termination is required to be "closed

contact".

3.DESCRIPTI0N

3.1.

PRINCIPLE AND AIRFLOW

The well insulated cabinet interior is divided into working and treatment chambers, as shown in the diagram (fig. chamber into the working chamber through the right hand wall plenum in which the wet and dry bulb sensing elements are situated in the optimum position for rapid response. The conditioned air passes through the working chamber in a turbulent manner, ensuring minimum temperature gradients, before returning to the treatment chamber through the left hand wall plenum.

All performance tolerances are to within 50mm of the walls of the working chamber. This is the working envelope in which the test load is not affected by heat sources such

as fans, heaters or cooling coils.

The temperature and relative humidity of the air are maintained at the conditions set by the operator via the control system. A sloping false roof is fitted to the working chamber to prevent condensation dripping onto the test load. The base of the working chamber is double skinned to prevent hot and cold "spots" forming due to radiated heat/cold from the treatment chamber. If required, the base of the working chamber may be used as

another

shelf.

1).

Air is circulated by a fan from the treatment (conditioning)

direct

cooling^

coil

working chamber

111

heaters

refrigeration unit

Figure 1

vapour phase

generator

temperature

sensors

drain

3.2. TEMPERATURE CONTROL

Accurate, repeatable temperature control levels are achieved by continuously balancing heat loss with intermittent modulated heating controlled by electronic controllers.

The conditioned air flows over a dry platinum resistance temperature sensor (BS1904,

lOOohms at 0°C) which feeds signals back to an electronic controller. The actual temperature is compared with the operator set temperature and errors are corrected by switching the heaters via relays on a time proportioning basis to achieve smooth accurate control.

3.2.1 HEATING

One or more "mconel" sheathed electrical heating elements are situated in the treatment

area. These elements normally operate only at black heat, for a long life and avoidance of excessive heater surface temperatures.

3.2.2 COOLING

All models have CFC-free mechanical refrigeration units with a direct cooling coil to

achieve the minimum temperature specified

All refrigeration compressors are protected for operation at working chamber temperatures up to +70°C.

Cabinets with a -70°C lower temperature limit (CF7 models) use cascade refrigeration systems.

The main and auxiliary cooling modes are automatically selected by the control system to enable:

a) freefall temperature pull-downs from the cabinets maximum temperature, ie the fall

rate is as fast as possible down to +70°C or below.

b) temperature dwells below +40°C (auxiliary cooling is used between +40°C and

+15°C if high humidity control is required).

c) extraction of heat dissipated from the test load between +70°C and the minimum op-

erating temperature.

d) the cooling coil's low surface temperature to dehumidify the cabinet between +5°C

and+70°C.

Refrigeration unit control

The refrigerator is controlled by the switching of solenoid valves which pass refrigerant to pressure switches, which in turn energise the refrigerator compressor motor. There is a short delay between switching and motor start up. Similarly, pressure switches act as safety devices, preventing excessive pressure which might arise when the refrigerator is not selected, and the refrigerant is heated by the cabinet. In such cases, the pressure switches detect the incipient pressure rise and switch on the compressor to "pump down".

3.3. RELATIVE HUMIDITY (RH)

Relative humidity is a measure of the ratio of the amount of water vapour present in an atmosphere to the amount of water vapour that atmosphere could hold, ie. Ihe humidity present relative to the humidity possible. The latter varies with temperature, hence RH measurements are related to their prevailing temperature. Air at 100% relative humidity is saturated and cannot absorb any more water. If air at 100% rh is heated, the amount of water the air can hold increases and therefore the %rh will drop unless more water is introduced. If air at 100% rh is cooled, water will be lost through condensation on to the cooling surface.

For each atmospheric RH/temperature relationship there is another relevant temperature, known as the dew point. Surfaces at or below this temperature chill the water vapour sufficiently to cause condensation.

3.3.1 RELATIVE HUMIDITY DETERMINATION

Air with a relative humidity less than 100% flowing over a wet surface causes evaporation of water from that surface and causes a temperature drop at the surface. The actual drop in temperature compared with the temperature of a similar dry surface subjected to the same air flow can be used to measure and control relative humidity. The technique is known as "wet & dry bulb psychrometry" and the difference in temperature is referred to as the "wet bulb depression". Psychrometric tables give

interrelated values for temperature, relative humidity and wet bulb depression.

In the cabinet, conditioned air flows over two resistance thermometer (RT) sensors, one dry and one kept permanently wet by a wick fed from a constant level water reservoir. The RT's are connected to the programmer. The relative humidity is determined from the psychrometric difference between the wet and dry RT's. The reference temperature for humidity control is compensated for the actual chamber temperature. Errors are corrected by actuating the vapour phase generator (vpg).

3.3.2 RELATIVE HUMIDITY CONTROL

Relative humidity levels are maintained by balancing continuous, minimised, extraction

of water by condensation with intermittent injection controlled by an electronic controller.

3.3.3 RELATIVE HUMIDITY INCREASE

All cabinets are fitted with a vapour phase generator (VPG).

Vapour phase generation

Water vapour produced in the vpg is introduced into the treatment chamber and is absorbed by the air.

The vapour phase generator is provided humidification from 15% to 95% rh at 60°C to

50to95%at20°C.

3.3.4 RELATIVE HUMIDITY DECREASE

Dehumidification is achieved using the cooling coil to form a dew point to remove water vapour from the air in the working chamber.

The direct cooling mode has a low surface temperature cooling coil which enables dehumidification of the cabinet air between +5°C and +70°C.

4.INSTALLATION

4.1.

ACCESSORIES & SPARES

Check that the following items have been supplied with the cabinet.

a) Wick for the wet bulb sensor(s)

b) A set of psychrometric tables for the recorder (if fitted)

c) Instructions and wick for recorder (if fitted)

4.2.

POSITIONING

4.2.1 Cabinets not requiring on-site commissioning

Place the cabinet on a level site, or suitable surface in the case of bench standing models, in such a position that air is free to circulate around it. The cabinet should be placed at least 450mm (18ins) away from any obstruction, eg: a wall or workbench.

For floor standing models lock the front castors to prevent movement.

Stand the cabinet in its operating position for 24 hours before switching on, to allow oil in the refrigeration system to return to sump. If the cabinet is moved, allow it to stand again.

If required, we can arrange for one of our engineers to commission the cabinet. Should you feel that his services are required please telephone us at Loughborough to make the necessary arrangements. During his visit our engineer will run the cabinet and check that its systems are functioning correctly and enable you assure that your staff are fully acquainted with the cabinet and its operation.

4.2.2 Cabinets requiring on-site commissioning

Cabinets supplied with a separate or remote refrigeration unit should be positioned to enable the pipe and cable connections to be made by our service engineer. Positioning must be on a level site such that the cabinet and refrigeration unit are at least 450mm (18 ins) away from any obstruction, eg: a wall or workbench. Lock the front castors to prevent movement.

During his visit our engineer will run the cabinet and check that its systems are functioning correctly. Take advantage of the commissioning visit to ensure that your staff are fully acquainted with the cabinet and its operation.

Connect a suitable power supply to the cabinet (see section 4.4). The maximum power ratings are shown on the cabinet rating plate (and refrigeration unit rating plate, if applicable).

DO NOT SWITCH ON THE CABINET UNTIL IT HAS BEEN COMMISSIONED.

Figure

^gomax.

5S0 controller

Mains On/Off

pushbutton (green)

Reset pushbutton

(orange)

Mains isolator

Figure

Distilled water inlet

instrument

compartment

Overflow (wick reservoir tank)

sited

back

some

cabinets

Overflow (VPG

reservoir tank)

"sited

back

Drain at

back

some cabinets

(sited

some cabinets)

4.3.

AMBIENT TEMPERATURE

IMPORTANT

To achieve the guaranteed performance figures, the maximum acceptable laboratory ambient temperature is +25°C. At higher ambient temperatures, the minimum operating temperature and rate of fall will be affected.

All refrigeration equipment, from home freezers to air-conditioning plant, performs a heat exchange operation in which the refrigeration compressor acts as a heat pump to transfer heat from the cooling coil (called the evaporator because this is where the gas evaporates and absorbs heat) to the condensing coil (where the gas condenses and gives up heat). The condensing coil is air-cooled, and assisted by a fan.

All air-cooled condensers need air movement around them in order to be able to give up to the air the heat extracted from the cooling coil (and hence the cabinet).

If the ambient temperature is high (above +25°C) more air will be required around the condenser to take up the same amount of heat At the same time the higher ambient temperature transfers heat more quickly into the cabinet through the insulation, giving the refrigeration unit more work to do to maintain low temperature conditions.

Excessively high ambient temperatures and poor ventilation will cause the refrigerator compressor to overheat and inevitably reduce its working life - possibly even causing it

to burn out.

4.4. POWER SUPPLY

Cabinets designed for operation from a 13A supply are supplied with a 13A plug fitted.

Cabinets not supplied with a 13A plug are required to be hard wired by a competent electrician to an adequate power supply by connection to the front panel power contactor. Power requirements are shown on a plaque on the rear of the cabinet, The supply frequency is 50Hz, unless stated otherwise. An EARTH connection is essential to all chamber. In addition, if the chamber requires a 3 phase supply NEUTRAL is also required.

WARNING

If the cabinet requires on-site commissioning do not switch on until it has been fully commissioned, see section 4.2.2.

4.5. MAINS INTERRUPT BRIDGE

If the power supply to the cabinet fails for up to 30 seconds, the cabinet will restart and continue the program from where it left off. However if the power supply interruption lasts longer than approx 30 seconds the cabinet will fail-safe.

4.6.

DRAIN

An outlet nipple (usually copper pipe) is fitted to the cabinet (right hand side or back). Connect a pipe to give a CONTINUOUS FALL to an OPEN DRAIN. Drainage restriction could cause an airlock and consequent flooding of the treatment chamber.

Two small black plastic pipes are also fitted to the right hand side or rear of the cabinet. These are overflows from the wick reservoir and vpg humidification system self levelling header tanks. If a float valve develops a fault, the respective overflow will operate preventing flooding of the instrument compartment

4.7.

DISTILLED WATER SUPPLY

EITHER

Connect the distilled water supply to inlet connector situated on the right side or at the

rear of the cabinet. Maximum allowable head is 1500mm (5ft) above the inlet.

It is safe for a container to stand on top of the cabinet, but ideally any reservoir should have its own support to one side of the cabinet.

If the cabinet is supplied with a water re-circulating system, fill the reservoir as instructed and connect the water connections to the cabinet water inlet and drain as shown..

4.8.

WETWICK(S)

(See Section 6.2.4 wet wicks)

Wet bulb sensor(s) must be fitted with wet wick(s).

Anchor the wick in the water reservoir and then push it over the sensor. The wick should

be taut but not stretched. The sensor must be completely covered. If any part of the

sensor is uncovered or protrudes through the weave then accuracy will be impaired.

Keep wick material clean. Contamination affects absorbency and hence RH control.

4.9.

TEST LOAD PROTECTION

A safety thermostat should be fitted to all equipment being powered inside the cabinet. The thermostat should switch off equipment power if the air temperature in the cabinet rises above safety level.

The thermostat will protect both the equipment and the cabinet against damage in the event of failure or shut down of the cabinet's temperature control system. Equipment dissipating only a few hundred watts inside the well insulated cabinet, with no cooling, will heat sufficiently to cause severe damage.

Advice on suitable thermostats is available from our Technical Department.

SANYO GALLENKAMP will not be held responsible for any damage to either equipment or cabinet, during or after the cabinet guarantee period, caused by heat dissipation from unprotected equipment.

If the cabinet is fitted with a glass inner door and the load being tested in the cabinet is liable to dissipate excessive heat, the glass inner door must be protected from absorbing this heat by radiation effect. Failure to protect the inner door could result in the glass cracking.

4.10.

CABLE PORT

One or two cable portis are fitted to the left hand side of the cabinet to enable wiresAeads etc to pass into and out of the cabinet. The port has two plugs, one inside, one outside the cabinet and both plugs must be fitted when the cabinet is in operation to maintain

the cabinets excellent insulation. The plugs can be slit or holes bored to enable

wiresAeads to pass through the port. WiresAeads should enter the cabinet via the top of the outside plug and the bottom of the inside plug to prevent condensation accumulating between the plugs. Extra or replacement plugs can be obtained, see PART NUMBERS

4.11.

4.12.

VENT

An air vent is situated at the rear of the cabinet. The hole in the vent must always be kept clear as it prevents pressurisation of the cabinet.

GLASS INNER DOOR

When fitted, a glass inner door enables observation of the test without unduly disturbing the cabinet's climatic conditions. The door is held closed by sash fasteners which should be hand tight and not forced.

If the test load dissipates heat, the glass door must be protected from absorbing heat by radiation effect, see section 3.8 Test load protection.

4.13. RS232 CONNECTOR

On the right hand side of the instrument compartment is the 25 pin "D" type RS232 serial communications connector of the Format 550 programmer. Further details of the pin connections are given in Part 2 of this manual.

4.14. SAFETY THERMOSTAT

A factory preset safety thermostat is fitted inside the instrument compartment to protect against overheating of the cabinet in the event of failure of the temperature control system.

The thermostat is set to a temperature 10°C above the maximum operating specification of the cabinet. The thermostat must not be reset.

Should the cabinet air temperature exceed that set on this thermostat it will cause the

cabinet to fail-safe, i.e. shutdown automatically.

N.B.this thermostat monitors the cabinet only - see also 4.9 - Test load protection.

5.0PERATI0N

WARNING

This cabinet is capable of temperatures well outside ambient. If the door is opened during such conditions there could be a temperature HAZARD from cabinet air or contents.

5.1.

CONTROL PANEL INSTRUMENTATION

Full details of the Format 550 programmer/controller fitted to the cabinet are given in Part 2.

If there are any further controls not mentioned here, refer to 2.3 - Additional facilities fitted.

5.1.1 INDICATORS/PUSHBUTTONS

Mains Green indicator lamp

The mains indicator is illuminated green when mains power is supplied to the cabinet and the mains power switch (red/yellow rotary switch) is switched on.

Reset Amber pushbutton

Internal lamp glows whenever the cabinet is powered but not reset. Press to reset and start the cabinet. The reset button is not illuminated when the cabinet is running.

5.1.2 RECORDER

If a recorder is fitted it should be set up and operated in accordance with the manufacturer's instructions, packed either with this manual or inside the instrument itself.

5.2. CABINET AND PROGRAM START UP

Ensure that: a) The interior of the cabinet is clean and dry. b) You know how to SHUT DOWN the cabinet (see section 5.4). c) Distilled water level is adequate d) Clean wicks are fitted to the wet bulb sensor(s).

TO START THE CABINET:

a) Switch the MAINS red/yellow isolator fitted to the front control panel to ON. The

MAINS pushbutton on the front control panel will become illuminated green. b) Power is now available to the Format 550 controller and settings for required test or

cycle are entered - see Part 2 of this manual for the Format 550 instructions.. c) Start manual control or the desired program. d) Press and hold the RESET pushbutton until the cabinet starts. The reset orange indi-

cator light will extinguish when the cabinet starts.

e) The Format 550 will now control the cabinet.

5.3. CABINET AND PROGRAM SHUT DOWN

TO SHUT DOWN THE CABINET - NORMAL SEQUENCE:

a) To terminate steady state or two setpoint cycling control - see Format 550 instruc-

tions.

b) When control by Format 550 has been completed or terminated switch the cabinet's

red/yellow mains isolator to OFF. The cabinet conditions will now drift slowly to ambient.

EMERGENCY SHUT DOWN:

a) Switch the MAINS red/yellow isolator fitted to the front control panel to OFF.

6.MAINTENANCE AND CARE

WARNING

Before entry into the instrument compartment, refrigeration compartment, or treatment

chamber ISOLATE THE CABINET FROM MAINS POWER unless otherwise stated.

The cabinet has been designed and built for a long life and requires minimal attention and maintenance. However, regular attention to the few points will ensure a long and trouble free life.

If the cabinet does fail, the expertise of our service engineers is readily available for

either diagnostic advice or on-site attendance. Service contracts are available after the one year guarantee period finishes and details are available from our Service Department.

This section contains a maintenance schedule to follow and a methods section giving instructions relating to the schedule.

Note: If the cabinet is going to be left unused for more than a month, we suggest that

the cabinet is started up and run through all its functions on a monthly basis. This will

ensure that the cabinet is in perfect running order for when it is required.

6.1 • MAINTENANCE SCHEDULE

Weekly or between tests

Clean the cabinet's interior and exterior surfaces Clean drain(s) Clean atomiser(s) Check wicks

Month

Renew wicks Lubricate moving parts Check safety thermostat Clean refrigerator condenser Check distilled water filter

6.2. MAINTENANCE METHODS

6.2.1 Interior and exterior cleaning

The cabinet interior and exterior should be kept clean and free from deposits.

The exterior surface is easily cleaned with warm soapy water. When cleaning any

stainless steel surface do not use any cleaning agent containing chloride or hypochlorite

ions as these will cause corrosion.

6.2.2 Cleaning of cabinet drain(s)

Either one or two drains are situated centrally in the base of the treatment chamber.

Access to the treatment chamber involves the removal of the working chamber base. Remove the front cover and slide out the working chamber base. Any accumulation of contaminants from the test sample can cause the treatment chamber to block. The drain should be checked regularly to ensure that particles are not collecting around it.

6.2.3 Inspection and replacement of the wet wick(s)

Access to the sensors and wicks is through the sliding panel in the right hand wall of the

working chamber. See fig. 4 for the position of the wet and dry bulb sensors.

The accuracy of all wet and dry bulb systems for the control of relative humidity is totally dependent on the wet wick. The rate of evaporation from the wick determines the cooling of the sensor and hence the temperature differential (wet bulb depression) of the control or recording instrument. Adherence to the following notes is recommended for all serious work at controlled relative humidities.

a) Wick must be clean - handle with care and clean hands - store in a clean place - change

regularly (once a month).

b) Wick must cover the entire exposed length of the sensor ie: extend well beyond the

sensitive tip and fit tightly to the sensor.

c) Wick must be the correct length to fit over the sensor and well down into the rubber wick reservoir, to prevent the high speed, necessary for correct evaporation, from blowing the wick out of the reservoir.

d) If wicking quality of the material is suspect, test by cutting off 1 cm of dry material and dropping into a cup of distilled water. Sample should wet and sink within 2 seconds.

Often wicking quality can be restored by boiling for a few minutes in clean distilled . water.

Figure 4.

RECORDER CONTROLLER

DRYRT WETRT WETRT DRYRT

white\ /white

Temperature sensor positions (as viewed from inside working chamber)

6.2.4 Lubrication

Most moving parts are lubricated and sealed for life except, the inner door catches (if glass inner door is fitted). These components should be oiled once per month

6.2.5 Check safety thermostat

Adjust the safety thermostat, sited inside the instrument compartment, through prevailing cabinet temperature. Check that the safety thermostat fails the cabinet safe. In the event of a fault RECTIFY AT ONCE.

6.2.6 Clean the refrigeration condenser

It is essential that the refrigeration condenser is kept clean - dirty condensers adversely affect the performance of the cabinet and reduce the working life of the refrigeration unit.

Isolate from MAINS

Remove the front louvre and back mesh panels from refrigeration compartment, or

ventilation panels in the case of a separate refrigeration module.

Gently brush/blow/vacuum dust etc from the fins and tubes of the refrigerator

condenser coil(s).

Initially check and clean the condenser monthly, actual frequency will depend upon the cleanliness of the surroundings.

6.2.7 Distilled water filter

This is located below the distilled water inlet nozzle and can be inspected through the viewing hole in the cabinet's side or back panel. The clear plastic bowl and filter can be removed for cleaning.

ISOLATE ELECTRICS

If recirculating water system is not fitted disconnect the distilled water supply.

Open instrument compartment door.

Unscrew the bowl and remove the filter. Clean or replace.

Reassemble in reverse order.

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