Despatch 934 Installation Manual
C-155
PN 122648
REVISION D
1/2011
900 Series
Temperature Chamber
INSTRUCTION MANUAL
Notice
Users of this equipment must comply with operating procedures and training of
operation personnel as required by the Occupational Safety and Health Act (OSHA) of
1970, Section 6 and relevant safety standards, as well as other safety rules and
regulations of state and local governments. Refer to the relevant safety standards in
OSHA and National Fire Protection Association (NFPA), section 86 of 1990.
Caution
Setup and maintenance of the equipment should be performed by qualified personnel
who are experienced in handling all facets of this type of system. Improper setup and
operation of this equipment could cause an explosion that may result in equipment
damage, personal injury or possible death.
Thank you for choosing Despatch Industries. We appreciate
the opportunity to work with you and to meet your heat
processing needs. We believe that you have selected the
finest equipment available in the heat processing industry.
At Despatch, our service does not end after the purchase
and delivery of our equipment. For this reason we have
created the Service Products Division within Despatch. The
Service Products Division features our Response Center for
customer service. The Response Center will direct and
track your service call to ensure satisfaction.
Whenever you need service or replacement parts, contact
the Response Center at 1-800-473-7373, International 1952-469-8230.
Thank you for choosing Despatch.
Sincerely,
Despatch Industries
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ii
PREFACE
This manual contains instructions for all accessories available on the Despatch 900
Series Environmental Bench Chamber. You may want to mark the parts of the manual
that are applicable to your particular oven.
The INTRODUCTION provides a brief overview of options available for the Despatch
900 Series Environmental Bench Chamber.
The INSTRUCTIONS cover the installation and operation of the 900 Series
Environmental Bench Chamber.
The THEORY OF OPERATION provides detailed technical information on the heating
system, the cooling system, condensation and corrosion.
The MAINTENANCE section contains technical information and checklists for
maintaining the equipment.
The APPENDIX contains tables for Troubleshooting, Temperature/RH%/Pressure
Equations, Humidity Conversion Tables, Wet Bulb Depression - % RH Conversion
Table and the Industrial Equipment Commercial Warranty.
iii
Revision B: Updated schematic diagrams
Revision C: Update Despatch Product Warranty
Revision D: Update Controller information, cover, warranty
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TABLE OF CONTENTS
PREFACE ........................................................................................................................ii
INTRODUCTION ............................................................................................................. 3
230 Volt, 50/60 HZ Operation ............................................................................... 3
Specifications ....................................................................................................... 4
INSTRUCTIONS ............................................................................................................. 5
Operator Training Requirements .......................................................................... 5
Installation ............................................................................................................ 6
Installation of Cooling Gas.................................................................................... 8
Installation of Carbon Dioxide ............................................................................... 9
Liquid CO2 Cylinder Installation ............................................................... 13
Installation of Liquid Nitrogen ............................................................................. 14
Liquid Nitrogen Cylinder ........................................................................... 16
Operating ............................................................................................................ 18
Controller Power Up ................................................................................ 18
Heating Only Operation ........................................................................... 19
Cooling Operation .................................................................................... 20
Safety Information ................................................................................... 21
Performance Characteristics ................................................................... 21
THEORY OF OPERATION ........................................................................................... 26
Functional Description ........................................................................................ 26
High Limit Controller ................................................................................ 28
Watlow EZ-Zone PM Controller .......................................................................... 29
Digital Communication ............................................................................. 30
Serial Data Transmission ........................... Error! Bookmark not defined.
MAINTENANCE ............................................................................................................ 32
Preventative Maintenance Schedule .................................................................. 34
Test Equipment Required ........................................................................ 35
Chamber .................................................................................................. 35
Coolant Solenoid Orifice Assembly ......................................................... 36
CO2 Filter ................................................................................................. 37
Corrective Maintenance ...................................................................................... 38
Service Procedures ................................................................................. 40
Electronic Control Chassis ....................................................................... 41
HI-LIMIT Thermoswitch ........................................................................... 42
APPENDIX .................................................................................................................... 43
IEEE 488 Interface Converter Set-up ................................................................. 43
IEEE 488 Interface Converter .................................................................. 45
Serial Signal Descriptions ........................................................................ 46
XON/XOFF Protocol ................................................................................ 48
XON/XOFF Versus RTS/CTS Handshaking ............................................ 48
Sample Program ...................................................................................... 49
Sample Output ......................................................................................... 50
Troubleshooting .................................................................................................. 51
Schematic Diagrams .......................................................................................... 52
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3
INTRODUCTION
The Despatch Industries 900 Series Environmental Bench Chambers are designed for
high performance and close temperature tolerance. A closed air flow system transfers
heat to or from objects under test. The chamber is heated by a low- inertia coil heater
and cooled by the injection and evaporation of a liquefied gas. An advanced control
system holds chamber temperature to close tolerance.
Units are ideal for small lot qualification testing, burn-in, life test, temperature cycling or
research and development. All models may be easily modified to add access ports,
fixturing, instrumentation, etc., to meet special customer needs. All models are
designed for continuous use with ease of operation and maintenance in mind.
Figure 1: 900 Series Environmental Chamber Bench Oven
230 Volt, 50/60 HZ Operation
All 920 and 930 series units are designed for 115 volt, 50/60 Hz. operation. An optional
transformer kit is available to allow these units to be used on 230 volt power supply.
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Specifications
Model
924 934 925 935 926 936
Test Volume in cubic feet (liters)
0.4 ft3 (11.3)
0.78 ft3 (22.1)
0.78 ft3 (50.4)
Workspace Dimensions (width x depth x
height) inches (cm)
10 x 10 x 7 in
25 x 25 x 18 cm
14.5 x 11 x 8.5 in
37 x 28 x 22 cm
20 x 14 x 11 in
51 x 36 x 28 cm
Exterior Dimensions (width x depth x
height) inches (cm)
17.5 x 18.5 x 11 in
44 x 47 x 28 cm
17.5 x 19 x 19.5 in
44 x 48 x 50 cm
35 x 24.5 x 15.5 in
89 x 62 x 39 cm
Temperature Range
°F
°C
924, 925, 926
-100 to + 525
-73.3 to +274
934, 935, 936
-300 to +392
-184 to +200
Average Heat-up Rate1 /min
°F
°C
72
40
32
18
20
11
Average Cool-down Rate
1
/min
°F
°C
46
26
54
30
27
15
40
22
41
23
29
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Temperature Control2
°F
°C
±0.25
±0.14
±0.25
±0.14
±0.25
±0.14
±0.25
±0.14
±0.25
±0.14
±0.25
±0.14
Live Load Capacity2
Watts
500
700
1000
Temperature
85
65
200
93
85
65
200
93
85
65
200
93
Heater Capacity in kW
2 2 2 2 2 2 Power Draw in Amps (120V-1ph-60Hz)3
18
23
20
24
20
24
Air Flow
Horizontal
50 CFM (24 lps)
Vertical
150 CFM (71 lps)
Horizontal
175 CFM (82.5 lps)
Approximate Weight
lbs
kg
38
17
41
19
58
26
61
28
102
47
108
49
Cooling rates are approximate and represent the average rate achieved over the stated
1
At steady state conditions.
2
A three wire 6 ft (1.8m) power cord is provided (120V single phase)
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temperature range with an empty chamber. Actual cooling rate achieved may vary depending on
the temperature range, the type of cooling, the pressure of the gas, and other factors.
Additionally, all cooling rates stated are for the condition when the controller is not cycling the gas
flow. The controller will slow the rate of cooling as the temperature nears set-point, so as to not
overshoot the set-point.
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INSTRUCTIONS
WARNING: Nitrogen and carbon dioxide
gases can cause asphyxiation and death if
used in confined, poorly-ventilated areas.
WARNING: Nitrogen and carbon dioxide
as liquid or cold gases can cause freeze
burns of the eyes and skin.
Operator Training Requirements
All users must be thoroughly trained under the supervision of experienced personnel.
The operator must aware of the danger of:
suffocation from nitrogen and carbon dioxide gases,
frostbite from nitrogen or carbon dioxide as liquid or frozen gases,
fire.
User(s) must demonstrate an
understanding of the equipment and its
operation to assure knowledge of and
practice of safe and proper operating
procedures.
User(s) should receive regular re-training
and testing as required to maintain a high level of proficiency and effectiveness.
Training should include the:
function of controls and safety devices,
handling of special atmospheres (on units with LN2 or CO2 auxiliary cool).
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Installation
NOTE:
Attention: Always refer to the electrical
schematic for exact instructions on your
equipment.
NOTE:
WARNING: DO NOT install in wet,
corrosive or explosive atmospheres.
1. Remove all packing materials.
2. Inspect the oven for damage of any kind that could have occurred during
shipment.
See whether the carton and plastic cover sheet inside carton are still in good
condition.
Look at all outside surfaces and corners of the oven for scratches and dents.
Check the oven controls and
indicators for normal
movement, bent shafts, cracks,
chips, and missing parts such as
knobs and lenses.
Look inside the control cabinet for loose or broken parts.
Open the chamber door and look at all the chamber surfaces to see that they
are flat and smooth.
Check the door and latch for smooth operation.
3. If anything is found to be out of order, check the rest of the oven very carefully
for any other damage that could have occurred.
a. If there is damage that could
have happened during
shipment, contact the
shipper immediately and file
a formal, written damage claim.
b. After you have filed a written damage claim with the shipper, contact
Despatch Industries to report your findings and to order replacement parts
for those that were damaged or missing. Please send a copy of your filed
damage claim to Despatch.
4. Set the unit on a level floor with clearances of at least 6 inches (15.2cm) on all
ventilated sides.
5. Locate utility connections at the rear of the chamber.
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6. Install the power cord.
WARNING:
WARNING: If your receptacle cannot
accommodate these plugs, your wiring
and/or receptacle must be upgraded to
allow this plug to be used. If the plug is
modified, this equipment will not meet code
and could result in a wiring and/or
receptacle overload. Failure to heed this
warning can result in wiring and/or
receptacle overheating, fire and/or property
damage, personal injury or death.
WARNING: Nitrogen and carbon dioxide
gases can cause asphyxiation and death if
used in confined, poorly-ventilated areas.
WARNING: Nitrogen and carbon dioxide
as liquid or cold gases can cause freeze
burns of the eyes and skin.
The 920 series units are equipped with a 20 amp, 120 volt rated plug designed to
be plugged into a Hubbell Model 5362, or equal, receptacle. This plug is
required by the NEC and will provide necessary protection for this chamber
installation.
The 930 series are equipped with a
30 amp, 120 volt rated plug
designed to be plugged into a
Hubbell Model 9308, or equal
receptacle. This plug is required by
the NEC and will provide necessary
protection for this chamber
installation.
7. Connect the appropriate LN2 or CO2
supply to the fittings provided on the
chamber.
8. CO2/LN2 Venting. The room must be ventilated sufficiently to ensure that the
oxygen level in the vicinity of the chamber will be maintained above 18% and
the CO2 level will be maintained below 0.5% at the expected N2 or CO2 usage
levels. If critical ventilation cannot be maintained, the exhaust port must be
connected to an exhaust system which will vent the nitrogen or CO2 out of the
facility. The exhaust port is on the rear of the unit. NOTE: exhaust temperature
may reach as high as 150C (300F).
CO2/LN2 consumption estimates are listed in the section titled “Performance
Characteristics”.
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Installation of Cooling Gas
WARNING:
WARNING: Nitrogen and carbon dioxide
gases can cause asphyxiation and death if
used in confined, poorly-ventilated areas.
Nitrogen and carbon dioxide as liquid or
cold gases can cause freeze burns of the
eyes and skin.
If the test chamber is to be cooled below chamber ambient temperature, it is necessary
to provide a source of liquefied coolant gas. The type, quality, and handling of the gas
is quite important as is the plumbing used to deliver the gas to the test chamber. Most
test chamber operational problems are caused by improper gas use; thus, the
installation procedures and precautions should be reviewed carefully before operating
the chamber.
The liquid coolant gases should be used only after observing stringent safety
considerations and practices.
Nitrogen is a non-toxic gas, but it can
cause asphyxiation in a confined area that
does not have adequate ventilation. Any
atmosphere which does not contain
enough oxygen for breathing (at least 18%)
can cause dizziness, unconsciousness, or
even death. Carbon dioxide affects the
important acid-base balance within the
body; the body can tolerate increased amounts of carbon dioxide only in limited
concentration. This is recognized in OSHA standards where a Threshold Limit Value of
5,000 parts per million by volume (0.5% concentration) has been adopted. For safety,
concentrations above this level should not be permitted; increased concentrations can
cause bodily harm or death.
Nitrogen and carbon dioxide cannot be detected by the human senses and will be
inhaled like air. If adequate ventilation is not provided, these gases may displace
normal air without warning that a life-depriving atmosphere is developing. Store
containers outdoors or in other well-ventilated areas. Never enter any confined area
where these gases may be present until the area is purged with air and is checked for a
breathable atmosphere.
Never use containers, equipment, or replacement parts other than those specifically
designated for use in nitrogen or carbon dioxide service. Gaseous nitrogen or carbon
dioxide should be released only in an outdoor open area if disposal is required. Liquid
nitrogen or carbon dioxide should be dumped into an outdoor pit filled with clean,
grease-free and oil-free gravel, where they will evaporate rapidly and safely.
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Installation of Carbon Dioxide
WARNING: Nitrogen and carbon dioxide
gases can cause asphyxiation and death if
used in confined, poorly-ventilated areas.
Nitrogen and carbon dioxide as liquid or
cold gases can cause freeze burns of the
eyes and skin.
Before purchasing or installing CO2 gas supplies, insure that the test chamber is the
correct model to use CO2 (High - 70 Kg/cm2 or 1,000 PSI or Low - 21 Kg/cm2 or 300
PSI) and that the desired low temperature can be reached by use of this gas. The
following special CO2 requirements must be met:
The liquid CO2 should be furnished by a reputable source.
The liquid CO2 cylinder must be a siphon-type. Syphon tank will have a red
neck.
The interior of the cylinder must be clean and absolutely dry before being
filled by the supplier.
Use of welding grade CO2 offers no assurance of trouble- free operation.
The internal condition of the cylinder and its previous use are more important
than the quality of the CO2.
Never fully exhaust the cylinder after use or leave a cylinder which is to be
returned to the supplier with the valve open. This will permit moisture or
other contaminants to enter the cylinder and cause serious problems when
the cylinder is reused later. If a cylinder is returned to the supplier without a
positive pressure, it must be purged with dry nitrogen by the supplier before
filling.
Other important factors are as follows:
The interior of the liquid CO2
pipe, tubing, hose and fittings
used between the supply
cylinder and the solenoid input
valve of the temperature
chamber must be kept clean and
free of moisture at all times. Any moisture will turn to ice as the liquid CO2
flows through the lines; the ice can then lodge on the solenoid valve seat or
plug the orifice of the valve and cause system malfunction.
Any low-pressure CO2 connecting hoses between the supply cylinder(s) and
the chamber input valve should be kept as short as possible and should be
insulated.
If the connecting hose is removed often or has been stored for a period of
time, the line and fittings must be examined for presence of chips, rust or any
foreign substance which can jam the inlet valve or plug the valve orifice.
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A filter installed in the line must be checked for cleanliness every 50 hours of
operation, or more often if necessary. Clean the filter in trichloroethylene and
dry thoroughly using filtered, moisture-free compressed air at low pressure.
It is important that the CO2 solenoid valve assembly and the orifice be kept clean.
Additional Precautions
Never install CO2 supply pipe fittings or valves of a larger internal diameter
than those used upstream [beginning at the supply cylinder(s)].
Do not use fittings which allow undue expansion or restriction of the liquid
CO2. This could cause the CO2 to reach a critical point where it would
expand in the line and cause icing.
Do not use excessively long, small diameter supply hoses which might cause
the liquid to change to gas in hot areas or during intermittent cycling
conditions.
Do not meter the CO2 through any type of valve that has a smaller I.D. than
the supply hose and CO2 supply cylinder siphon tube. The cylinder supply
valve should be fully open during use.
It is not possible to use all of the CO2 in a siphon-type cylinder. The ambient
temperature at the cylinder will determine the amount of CO2 available (about
95 percent of maximum). Thus, CO2 usage may appear to be somewhat
higher than it actually is.
Never set the temperature controller below -100 F (-73 C). Excessive
snowing occurs as you approach temperature below -100 F (-73 C) until the
temperature reaches -109 F (-78 C) which is the freezing point of CO2 at
atmospheric pressure. At -109 F (-78 C) all discharged CO2 could form
snow which could cause damage to the chamber and its contents and if
allowed to build up to the point of blocking off the pressure relief vent, could
cause explosion of the chamber due to available pressure from the liquid
carbon dioxide source.
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Pressure of Solid, Liquid and Saturated Vapor CO2
Temperature (F)
Pressure (PSIA)
Temperature (F)
Pressure (PSIA)
-140 3.19
-20
215.02
-130 5.39
-10
257.46
-120 8.85
0
305.76
-110
14.22
+10
360.4
-100
22.34
20
421.8
-90 34.05
30
490.6
-80 50.70
40
567.3
-70 74.90
50
652.7
-69.9 75.1
(triple point)
60
747.4
-60 94.75
70
852.5
-50
118.27
80
969.3
-40
145.87
87.8
1072.1
-30
177.97
The solenoid valve used to inject the CO2 coolant into the test chamber should "pulse" or
actuate rapidly. If the CO2 valve remains open for long periods of time after pull-down, the
chamber may be leaking coolant, the test object may be introducing substantial amounts of
heat beyond the capacity of the inlet valve orifice, or the temperature set-point may be set
below -73.3 C (-100 F). These conditions can cause "snow" to be introduced into the
chamber with resultant control problems and possible damage to the chamber and contents.
Causes for these conditions should be located and corrected.
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13
Liquid CO2 Cylinder Installation
WARNING:
WARNING: Always use heavy safety
chains to hold gas cylinders securely in an
upright position. A gas cylinder, damaged
by hitting the floor, can become a
dangerous projectile and cause serious
damage or injury over a wide area.
For extensive use at low temperatures, it is recommended that two or more liquid CO2
cylinders be used in parallel.
This will increase operating time between cylinder changes. Install the liquid CO2
cylinder(s) as follows.
1. Turn off POWER switch and disconnect AC input power.
2. Position the cylinder in a safe and convenient location.
3. Secure the cylinder in an upright
position with safety chains.
4. Carefully crack the cylinder valve
slightly before connecting the hose
assembly in order to blow out any
loose scale or rust which may be in
the cylinder.
5. Connect the hand wheel end of the hose assembly to the cylinder.
6. Connect the threaded fitting on the flexible hose to the threaded portion on the
chamber bulkhead fitting. The bulkhead fitting must be held in place with a
second wrench while the coolant hose is being attached.
7. When replacing the CO2 cylinder,
a. Shut off chamber if controls call for cool (see LED L2 on the front panel).
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b. Shut off the valve at the cylinder.
WARNING: Nitrogen and carbon dioxide
gases can cause asphyxiation and death
if used in confined, poorly-ventilated
areas.
Nitrogen and carbon dioxide as liquid or
cold gases can cause freeze burns of
the eyes and skin.
c. Crack the hose fitting slightly, and allow the residual CO2 pressure in the
hose to bleed off before disconnecting the hose.
d. Connect hose to new cylinder.
e. Open cylinder valve.
f. "Crack" the fitting at the bulkhead to bleed off gas and moisture.
g. Turn chamber on.
Installation of Liquid Nitrogen
Some models of test chambers use pressurized liquid nitrogen (LN2) so that lower test
temperatures may be reached. Line pressure should be between 55 kPa (8 PSI) and
310 kPa (45 PSI).
The following precautions should be observed in handling LN2 :
Liquid nitrogen is extremely cold (-196 C or -320 F) at atmospheric pressure
and can damage skin or eyes on contact.
Insulated gloves and safety goggles or face plates should always be used in
handling LN2.
Clean cotton clothes or lab coats should be worn where LN2 spillage or
prolonged contact with its vapors is a factor.
Smoking should be prohibited in the
immediate area were LN2 is being
handled.
All handling equipment such as
funnels, dewars, piping and tubing
must be clean, dry and free of grease.
All transfer tubes, valves and other
equipment which reach liquid nitrogen
temperatures should be properly insulated with a non-absorbent insulation
which is properly contained within a vapor seal.
Liquid nitrogen is not in itself explosive or combustible; however, its low
temperature will cause condensation of the water vapor in the air and all the
15
gaseous constituents of the air which liquefy above -196 C (-320 F),
including oxygen. Therefore, supply lines, clothes and equipment which are
subject to this temperature can absorb or liquefy oxygen, which will cause a
severe fire if ignited and which can become explosive when in contact with
grease.
LN2 should not be left in sealed containers or hoses. When the LN2 turns to
nitrogen gas, it will build up very high pressure. Unless LN2 is being actively
used in test chamber operations, care should be taken that an adequate vent
is provided and that excessive pressure is bled off.
The concentration of liquid oxygen suspended in the LN2 builds up as the LN2
is used. Consequently, nearly empty LN2 containers should be handled as if
they were liquid oxygen containers. The presence of liquid oxygen in LN2 can
be determined by the milky appearance of the liquid. LN2 is normally clear.
If parts of the body are frozen by contact with these cold liquids, first-aid
treatment for frostbite should be given, with slow thawing of the frozen parts.
Severe cases should be referred to a physician for treatment.
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Liquid Nitrogen Cylinder
NOTE:
Slide the insulation over the fittings after
connecting to the bulkhead fitting and the
coolant source.
The liquid nitrogen cylinder is connected to the test chamber by the hose assembly.
To prevent ice crystals in the coolant line
from entering the test chamber, an ice
filter (optional) may be connected
between the LN2 cylinder and the test
chamber.
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