AADCO 737 Series User manual

OPERATING INSTRUCTIONS
AADCO 737-SERIES
PURE AIR GENERATORS
737-1 & 737R-1
(1-LPM)
AADCO INSTRUMENTS, INC.
145 South Miami Ave.
Village of Cleves, OH 45002
U.S.A.
Telephone: [phone]
Fax: [phone]

737-1 and 737R-1 PURE AIR GENERATORS
TABLE OF CONTENTS
Section Page
LIST OF ILLUSTRATIONS............................................................................iii
0.0 DAMAGED AND/OR LOST IN SHIPMENT PROCEDURE.............................1
1.0 INTRODUCTION..............................................................................................2
2.0 INSPECTION UPON RECEIPT.......................................................................3
3.0 INSTALLATION................................................................................................4
4.0 OPERATION.................................................................................................... 6
5.0 PRINCIPLE OF OPERATION........................................................................11
6.0 PURIFICATION REACTORS.........................................................................12
7.0 METHANE REACTORS.................................................................................14
8.0 PERFORMANCE SPECIFICATIONS............................................................16
9.0 PREVENTIVE MAINTENANCE.....................................................................18
10.0 TROUBLESHOOTING...................................................................................20
11.0 COMPONENT REPLACEMENT....................................................................26
12.0 ABBREVIATED OPERATING INSTRUCTIONS ........................................... 28
13..0 PARTS LIST...................................................................................................29
ILLUSTRATIONS........................................................................30 THRU 46
WARRANTY................................................................................................. 47

737-1 AND 737R-1 PURE AIR GENERATORS
LIST OF ILLUSTRATIONS
Figure Page
1 FRONT PANEL...............................................................................................30
2 REAR PANEL WITH “HOUSE” AIR ADAPTER.............................................31
3 INSIDE TOP VIEW......................................................................................... 32
4 INSIDE BENCH-MOUNTED, COMPRESSOR SIDE VIEW .......................... 33
5 ELECTRICAL TERMINAL STRIP VIEW ........................................................ 34
6 FRONT PANEL, RACK-MOUNTED UNIT..................................................... 35
7 INSIDE RACK-MOUNTED, COMPRESSOR SIDE VIEW.............................36
8 INSIDE RACK-MOUNTED, METHANE REACTOR VIEW ............................ 37
9 WIRING DIAGRAM.........................................................................................38
10 PNEUMATIC DIAGRAM.................................................................................39
11 MOISTURE OUTPUT VERSUS TIME FOR REACTORS ............................. 40
12 GAS CHROMATOGRAPHIC APPLICATION OF “B” REACTOR ................. 41
13 “TEE” BLEED VALVE INSTALLATION..........................................................42
14 “B” REACTOR VERSUS CYLINDER FID RESPONSE.................................43
15 CHROMATOGRAMS-METHANE REACTOR EFFICIENCY .........................44
16 “A” VERSUS “C” REACTOR C02 OUTPUT................................................... 45
17 FLOW NOMOGRAPH.................................................................................... 46

0.0 DAMAGED AND/OR LOSS IN SHIPMENT PROCEDURE.
0.1 SHIPMENTS FOB FACTORY. This shipment was thoroughly inspected prior to
delivery to the carrier. Our responsibility for this shipment has now ended.
Therefore, you should make a thorough inspection upon its arrival.
0.2 In the event any portion of the shipment is damaged or missing, do not sign the bill
of lading or express receipt until the freight or express agent makes appropriate
notation on the receipt.
0.3 “Concealed damage” means damage which may not be apparent until after the
items are unpacked and tested. In the event of such damage, you should file a
written request within fifteen days of delivery with the carrier for inspection. Delay in
making this request may provide grounds for refusal of your claim. Be certain to
retain all papers, packing materials, etc., until the carrier has made his inspection.
Keep in mind that concealed damage can occur from rough handling even though
the shipment shows no evidence of external damage.
0.4 The carrier may request you to return the damaged item to AADCO Instruments,
Inc. for inspection and repair. In this event, we will repair or replace the item and
invoice you for the costs involved. This invoice then becomes part of your claim
upon the carrier.
0.5 SHIPMENTS FOB DESTINATION. In the case of damage in transit on shipments
made “FOB Destination”, we will gladly handle filing of the claim provided you
furnish us with an acceptable inspection report from the carrier. In the event that
our claim is disallowed because of your negligence in obtaining the report, it will be
necessary to bill you for the repair or replacement charges.
0.6 RETURNS TO AADCO INSTRUMENTS. If your property, while being returned to
AADCO Instruments, Inc. is damaged in transit, it will be your responsibility to file a
claim with the carrier. To assist you, we will secure an inspection report from the
carrier and forward it to you.
0.7 Prior to shipment to AADCO Instruments, Inc. you must call or write notifying us of
your intent. In addition, include some identifying note or letter with the item. This
note/letter should include the name of your contact person and the nature of the
damage.
1

1.0 INTRODUCTION.
1.1 The 737-1 (one-liter per minute) pure air generator is unique in the 737-series of
pure air generators. It is the only unit which is completely self-contained. All
components of the system, the air source and purification system, are within one
cabinet.
1.2 Incorporating all components within one enclosure limits the maximum output of this
instrument to one-liter per minute. Since all of the components must be able to
accommodate the air volume and perform the purification functions as well, there is
a compromise in component size.
1.3 The user must be aware of this limitation in capacity and select only those
applications whose requirements do not exceed this limitation. FAILURE TO DO
SO WILL COMPROMISE THE PURITY OF THE AIR ISSUING FROM THE UNIT.
1.4 When application is made to those situations which remain within the one-liter per
minute capacity, the air quality will be equal to any and all of the larger 737-series
pure air generators.
1.5 The 737-1 pure air generator is available either in bench-mounted or rack-mounted
units. All components are common to both and are readily interchangeable.
1.6 Figures 1 thru 5 are referenced to the bench-mounted units, Figures 6 thru 8 refer
to the rack-mounted units, and Figures 9 thru 11 are common to both.
1.7 The SOURCE SELECTOR valve, Figure 1 (5), and the EXTERNAL SOURCE
bulkhead connector, Figure 2 (4), are not a part of the rack-mounted units since the
use of “house” air as a source for this unit is very uncommon. Both of these
components, shown in Figure 10, should be ignored when addressing the rack
mounted systems.
2

2.0 INSPECTION UPON RECEIPT.
2.1 Remove unit from shipping container WITHOUT INVERTING.
2.2 For both bench-mounted (Figure 1) and rack-mounted (Figure 6), remove cover.
2.3 WITHOUT INVERTING, place unit between two level surfaces so that the bottom is
exposed.
2.4 Remove the two red screws underneath the chassis which held the compressor,
Figure 4 (14), stationary during shipment. (Hold these for possible future use.)
Screw removal is best accomplished by turning each screw a few turns, alternating
between screws rather than completely removing one screw and then the other.
The compressor is spring-mounted and removing one screw completely before
attempting to remove the other will cause difficulty with removal of the second
screw.
2.5 After removing the two red screws, remove blocking material from under
compressor and retain with screws for later use.
2 6 Check that the compressor rides freely on its shock mounts and that none of the
mounts is damaged.
2.7 Inspect for damage that column of the purification reactor, Figures 5 and 8 (1),
which is immediately adjacent to the outlet fitting of the compressor. Damage to the
column may occur during shipment if the compressor is not securely retained by the
shipping screws, thus allowing the compressor outlet fitting to pound against the
column. This could damage either or both the compressor outlet fitting and/or
purification column.
2.8 If all appears in order, replace the cover.
2.9 Remove the shipping plugs from all bulkhead fittings on the rear wall of the unit.
The unit is now ready for operation.
3

3.0 INSTALLATION.
3.1 THE FOLLOWING INSTRUCTIONS ARE TO BE FOLLOWED ONLY AFTER
SECTION 2.0 HAS BEEN COMPLETED.
3.2 FOR BENCH-MOUNTED UNITS UTILIZING “HOUSE” AIR AS THE PRIMARY AIR
SUPPLY TO THE PURE AIR GENERATOR, connect the “house” air adapter,
Figure 2 (1), to the EXTERNAL SOURCE fitting on the rear of the pure air
generator, as shown in Figure 2. The stainless steel tubing supplied with the
“house” air adapter will support the adapter rigidly when all fittings are properly
tightened.
NOTE: SINCE MOST “HOUSE” AIR SUPPLIES ARE FROM OIL-PUMPED
SOURCES, IT IS MANDATORY THAT THE AADCO INSTRUMENTS’
“HOUSE” AIR ADAPTER, AND ONLY THIS ADAPTER, BE USED. This
is an oil-indicating filter and dramatically indicates when depletion is
imminent. Use of this filter avoids contaminating the purification reactor
and jeopardizing the purity of the output air.
3.3 If a source selector valve, Figure 1 (5), is present, place it in its downward position
indicating EXTERNAL SOURCE. If not present, unit is ready for connection to the
air source.
3.4 Connect the “house” air to the lower inlet, Figure 2 (3), of the “house” air adapter
utilizing 1/4 inch swage connectors. Admit the “house” air to the “house” air adapter
and open the shutoff valve, Figure 2 (3), so that the “house” air enters the pure air
generator and registers its pressure on the INPUT PRESSURE gauge, Figure 1 (6).
NOTE: THE MINIMUM ACCEPTABLE PRESSURE FOR THE INPUT AIR IS 50-
PSIG AND THE MAXIMUM PERMISSIBLE PRESSURE IS 95-psig. Any
pressure lower than the minimum will compromise the effluent air purity
and any pressure greater than 95-psig will exceed the working capacity
of the inlet solenoid valves.
3.5 At this time, check for leaks using soap solution on all connecting fittings. Tighten
as required.
NOTE: The horizontal shutoff valve, Figure 2 (3), at the base of the “house” air
adapter serves as a shutoff to the air supply so that the pure air
generator may be moved and, should the need arise, the filter element
may be changed without shutting off the main air supply.
4

3.6 Connect the power cord to a suitable outlet observing voltage and power
requirements as shown on the rear of the unit, Figure 2 (7). The instrument is now
ready for operation.
3.7 FOR BENCH-MOUNTED UNITS UTILIZING THE INTERNALLY MOUNTED
COMPRESSOR AS THE PRIMARY AIR SUPPLY, place the source selector valve,
Figure 1 (5), in its upright position indicating INTERNAL PUMP.
3.8 Connect the power cord as in Section 3.6. The instrument is now ready for
operation.
NOTE: It is not uncommon to connect “house" air to those units which contain
their own internal compressors and to operate the units with “house” air
as the primary source, utilizing the internal compressor only during those
periods when the “house” air compressor is undergoing repairs or
maintenance. To make the conversion from “house” air to the internal
compressor, it is only necessary to turn the source selector valve to the
correct position and depress the PUMP switch, Figure 1 (3).
SPECIAL NOTE: AADCO Instruments, Inc. offers an automatic source selector for
those unattended installations where both “house” air and the internal compressor
are both available at the same unit. This device will automatically select between
the two sources and provide that source which is available should the other source
fail.
3.9 FOR RACK-MOUNTED UNITS (Figure 6), install in the electronics rack the slides
provided, correcting the alignment until the unit moves freely and the front panel
seats squarely when fully inserted within the cabinet.
3.10 Remove the two red screws underneath the chassis as in Section 2.4.
3.11 Connect the power cord to a suitable outlet observing voltage and power
requirements as shown on the rear of the unit, Figure 2 (7). The instrument is now
ready for operation.
NOTE: At no time should the DUMP fitting, Figure 2 (6), be restricted nor the
flow impeded in any way. The operator may attach a large bore 1/4 inch
o.d. tubing to this fitting and lead the exhaust into a space where the
exhaust noise will be inaudible; e.g., desk drawer, suspended ceiling, etc.
3.12 When “house” air is being admitted as the air source through the “house” air
adapter, Figure 2(1), ANY ACCUMULATED WATER MUST BE BLED DAILY via
the water bleed valve, Figure 2 (8).
5

4.0 OPERATION.
4.1 Once the instructions outlined in Sections 3.0 thru 3.6 have been followed, whereby
the air source has been connected to the pure air generator, leak checked, and the
power cord inserted into a proper outlet, the BENCH-MOUNTED unit utilizing
“house” air as the primary air supply is ready for operation.
NOTE: AT THIS TIME THERE SHOULD BE NO EQUIPMENT CONNECTED
TO THE PURE AIR GENERATOR.
4.2 The INPUT PRESSURE gauge, Figure 1 (6), should indicate the source air
pressure which must be not less than 50-psig nor more than 95-psig. See Section
3.4.
4.3 Depress the POWER SWITCH, Figure 1 (1). The POWER lamp should light, there
should be an audible “click” of the inlet solenoid valve of the purification reactor
followed immediately by a momentary decrease of input pressure and the
METHANE HEAT lamp, Figure 1 (12), if present, should light.
4.4 If no methane reactor is present, within one-minute (one full purification cycle) the
unit is ready to deliver clean air. The operator now may adjust the output pressure
to his needs by turning the OUTPUT PRESSURE REGULATOR, Figure 1 (9),
clockwise until the desired pressure appears on the OUTPUT PRESSURE GAUGE,
figure 1 (8).
4.5 To determine the proper output pressure from the pure air generator, it is necessary
to ascertain the greatest pressure required by any or all of the using instruments.
For example, if there are five instruments and the highest pressure requirement for
any or all of the instruments is 30-psig, then the output pressure can be set no
lower than 40-psig. This 10-psig pressure differential is mandatory for proper
operation of any differential pressure regulator. The 40-psig accommodates not
only that instrument with the 30-psig requirement but all of the others as well.
4.6 The pressures and flows at each of the using instruments should now be set
according to the recommendations of the manufacturer. If snubbers are present as
flow regulation devices, only proper pressure settings are required. If pressure and
flow settings are both required, set the pressure and then establish flow using
bubble towers or mass flow meters for accurate settings.
NOTE: Any instrumentation which is sensitive to even slight variations in oxygen
concentration; e.g., flame ionization detectors or flame photometric
detectors, etc.; all require incorporation of a mixer-receiver, Figures 5
and 8 (10), within the pure air generator prior to use by the above
mentioned detectors. NDIR, chemiluminescent, photoionization,
6

4.6 Continued.
and electrochemical sensors are unaffected by slight variations in oxygen
concentration and, therefore, do not require mixer-receivers.
4.7 At this time, since there is no equipment connected to the unit which may be used
to regulate the flow of pure air from the pure air generator, the operator must be
certain that the capacity of the unit is not being exceeded. To do so, the OUTPUT
FLOW ADJUST knob, Figures 1 and 6 (10), must be adjusted so that the indicated
flow is some value between 1.0 and 10.0 as perceived on the rotameter, Figure 1
(7). It is unnecessary to establish an exact flow during this “burn-in” interval but it is
important to maintain a positive flow of clean air, especially if there is a methane
reactor, Figure 5 (2), within the unit.
4.8 If there is no methane reactor in the unit, allow the pure air generator to operate for
about a half hour without connecting any equipment to the PURE AIR fitting, Figure
2 (5), located on the rear of the unit.
4.9 Following the half hour interval, connect the equipment which is to receive the pure
air to the PURE AIR fitting. Connections must be made with 1/4 inch large bore
tubing from the pure air generator to the using equipment. The using equipment
should be located as close to the pure air generator as possible. Great lengths of _
inch or small bore 1/4 inch tubing should be avoided because of the back pressure
exerted on the system by the restrictive tubing.
4.10 If connections at the using equipment are _ inch swage type, use 1/4 inch large bore
tubing from the pure air generator to the using equipment and then reduce to _
inch, keeping the _ inch length as short as possible. All “tees” should be 1/4 inch
also.
4.11 Open the OUTPUT FLOW ADJUST knob completely counter clockwise. Close all
valves at the using equipment. Within a minute or two the rotameter ball should
drop to zero indicating that the entire system is leak tight. If the rotameter ball does
not drop to zero but remains upscale, there is a leak. Check all connections with
soap solution and tighten as required until the rotameter ball does indicate zero. It
is imperative that all leaks be detected and remedied before putting the system into
full operation.
4.12 Once a leak free system has been established, set the required flows at each of the
receiving instruments after calculating that the aggregate flow does not exceed the
capacity of the unit.
4.13 If there is a methane reactor in the unit and the instructions in Sections 4.1 thru 4.5
have been followed, allow the unit to operate for about four hours without
connecting any equipment to the PURE AIR fitting located on the rear panel.
7

4.13 Continued.
NOTE: DURING THIS “BURN-IN” INTERVAL COPIOUS AMOUNTS
OF WATER WILL BE DRIVEN FROM THE CATALYST AND
WILL CONTAMINATE ANY INSTRUMENTS WHICH MIGHT
BE CONNECTED TO THE PURE AIR GENERATOR AT THIS
TIME.
4.14 Once the POWER switch has been depressed, the methane reactor will begin to
heat. After about a half hour the METHANE HEAT lamp should begin to cycle and
the pyrometer, Figures 1 and 6 (11), should indicate 290°C ± 10°C.
4.15 After a four hour interval, connect the equipment which is to receive the pure air to
the PURE AIR fitting and proceed as in Sections 4.7 and 4.8.
4.16 The operator should consult Figure 11 at this time to determine the time delay
before connecting the equipment to the pure air generator. The critical factor will be
the tolerance of the equipment for particular moisture levels.
4.17 Once connected to the using equipment the output flow can be regulated at the
pure air generator with the OUTPUT FLOW ADJUST valve, Figures 1 and 6 (10),
provided all flow devices external to the pure air generator are opened wide or
nonexistent. It is more common to open wide the OUTPUT FLOW ADJUST valve
on the pure air generator and control the flow at the using equipment with its own
flow control system; i.e., needle valves, differential flow controllers, etc.
4.18 Note that when the output flow is set with the OUTPUT FLOW ADJUST valve and
no external equipment is connected to the instrument, no methane reactor system
in the unit, and the rotameter vented directly to the atmosphere, the rotameter is
direct reading for output flow. See Figure 17. The operator must realize that when
any equipment is connected to the PURE AIR fitting the rotameter now operates in
a pressurized condition and is no longer direct reading and will indicate a lower flow
than is actually being delivered.
4.19 As an example, if the output pressure is set at 30-psig and the rotameter indicates
500-cc/min, then the full actual flow will be √3 times the rotameter indicated flow, or
866-cc/min, since the rotameter is now two atmospheres above ambient. This
same rule-of-thumb will apply at other pressure settings.
The calculation is: Actual Flow = √N+1 x R (N = Number of atmospheres above
ambient and R = Rotameter reading in LPM) as determined from the nomograph
(Figure 17).
8

4.19 Continued.
4.20
4.21
4.22
4.23
4.24
4.25
At 45-psig output pressure the rotameter float should not indicate greater than 50%
of full scale at any time since the rotameter is three atmospheres above ambient
and the actual flow is √4 times the indicated flow. Therefore, any flow reading
greater than 50% means that the flow capacity of the instrument is being exceeded
and the output purity is being jeopardized.
For the operator’s convenience, listed in Section 4.21 is the multiplier for each
output pressure setting. Simply multiply the rotameter reading in LPM (determined
by the proper nomograph, Figure 17) using the multiplier from the listing for that
operating pressure.
T PRESSURE MULTIPLIER
60 2.24
55 2.16
50 2.08
45 2.00
40 1.91
35 1.82
30 1.73
25 1.63
20 1.53
15 1.415
10 1.29
51.155
The purpose of this exercise is to allow the operator to know the flow conditions but,
more importantly, TO AVOID EXCEEDING THE OUTPUT CAPACITY OF THE
PURE AIR GENERATOR AND JEOPARDIZING THE OUTPUT PURITY. Each
pure air generator has a maximum output rating and the operator should know this
before setting flows.
The pressure and flows at each of the using instruments should now be set
according to the recommendations of the manufacturer. If snubbers are present as
flow regulations devices, only proper pressure settings are required. If pressure
and flow settings are both required, set the pressure and then establish flows using
bubble towers or mass flow meters for accurate settings.
Any instrumentation which is sensitive to even slight variations in oxygen
concentration; e.g., flame ionization detectors used with total hydrocarbon
analyzers, gas chromatographs, flame photometric detectors, etc.; all require
incorporation of mixer-receivers, Figures 4, 7 and 8 (10).
FOR BENCH-MOUNTED AND RACK-MOUNTED UNITS UTILIZING THE
9

INTERNALLY MOUNTED COMPRESSORS AS THE AIR SUPPLY TO THE PURE
AIR GENERATORS, proceed as applicable in Sections 3.7 through 3.10.
4.26 Depress the POWER switch, Figures 1 and 6(1). The POWER switch lamp should
light, there should be an audible click of the solenoid valve located on the inlet to
the purification reactor, and the METHANE HEAT lamp, if present, should light.
4.27 Depress the PUMP switch, Figures 1 and 6 (3). The PUMP switch lamp should
light. The compressor will start and pressure will appear on the INPUT PRESSURE
gauge, Figures 1 and 6 (6), and begin to increase.
4.28 Within three minutes (three full purification cycles) the unit is ready to deliver clean
air. The operator may now adjust the output pressure by turning the OUTPUT
PRESSURE REGULATOR, Figures 1 and 6 (9), clockwise until the desired
pressure appears on the OUTPUT PRESSURE gauge, Figures 1 and 6 (8).
4.29 SHUTDOWN PROCEDURE.
4.30 If the unit is not to be used for one week or more, depress the POWER switch,
Figure 4 (2), and immediately cap both the PURE AIR outlet, Figure 5 (34), and the
DUMP fitting, Figure 5 (32), to avoid contaminants from entering the system.
4.31 Depress the PUMP switch, Figure 4 (1). Unit is now ready for storage.
10

5.0 PRINCIPLE OF OPERATION.
5.1 The 737-series pure air generators produce absolutely clean air from pressurized
unclean air by chromatographic techniques. Pressurized air from a compressor or
other source enters either the number 1 or number 2 column system (see Figure
10), depending upon the status of the solenoid valve located at the inlet of the
column. These valves are normally closed, sealing the system against possible
contamination.
5.2 The pressurized air passes through the column where selective absorption takes
place, with a subsequent separation of the various components present in the air.
Only the desired components, which elute first, are permitted to reach the end of
the column system and elute, whereupon, the solenoid valve at the head of the
separation column closes and the solenoid valve at the inlet to the alternate column
system opens.
5.3 Pressurized unclean air now enters the alternate column system where separation
again takes place. The alternation of the two column system produces a steady
flow of purified air.
5.4 During the interval that pressurized unclean air is being separated in one column, a
portion of the clean air passes through the purge valve and back flushes the
alternate column of impurities. This purge valve, Figures 5 and 8(12), has been set
at the factory at optimum flow and must not be altered.
5.5 The back flush flow of air with impurities exits from the instrument through the
swage bulkhead connector labeled “DUMP” at the rear of the instrument, Figure 2
(6). This exit must not be restricted. A back pressure situation must be avoided at
this fitting.
5.6 The timer, Figures 4 and 7 (13), which provides alternate power to the solenoid
valve, has been set to effect the proper residence time of the unclean air in the
column and also the purge time for each size reactor. The timer must not be
altered.
5.7 To prolong the life of the support media within the column, it is mandatory that the
operational directions for the instrument be followed as closely as possible.
Selection of this separation medium, residence time in the column, proper input
pressure, purge flows, and column volumes have been determined to meet the
requirements of the particular 737-series pure air generator being used. These
components are not interchangeable except among units of the same rated output.
5.8 Rapid depletion of the purification reactor can occur if: (a) improperly filtered air is
admitted to the columns as with oil compressors, (b) water is admitted to the
columns, or (c) the unit is operated above its rated capacity.
11

6.0 PURIFICATION REACTORS
6.1 AADCO Instruments offers four basic types of purification reactors, designated “A”,
“B”, “C”, and “D”.
6.2 The “A” PURIFICATION REACTOR produces air of purity outlined in Section 8.0
and with an oxygen concentration of 20.8% ± 0.3%. In addition, the C02
concentration will be that of the ambient environment of the user’s locale (~350-
ppm). This purification reactor should be specified if the operator wishes to avoid
calibration disparities where it is essential that the C02 level for both the “zero” air
and the sample be the same; e.g., use of the flame photometric detector or NDIR.
The “A” model is the most universal purification reactor and is usually supplied
when advised of this application. It is the reactor to be employed for air monitoring.
6.3 The “B” PURIFICATION REACTOR is factory set to produce air with the same
purity as the “A” model but with an oxygen concentration of 37.0% ± 0.5%, at
specified conditions. By in-house experimentation, this concentration has been
found to produce a greatly increased response for most commercial flame
ionization detectors over that response experienced with cylinder air. This has
since been field proven and has become the purification reactor of choice when
high sensitivity FID is required. It has also been found to decrease the noise level
of the flame photometric detector when used in conjunction in a chromatography
mode. Use of this purification reactor will eliminate both the oxygen and air
cylinders when operating this detector for that application.
6.4 It should be noted that output flows less than 50% of the rated output should be
avoided with any model pure air generator which contains a “B” reactor. This is the
lower threshold for maintaining the oxygen output at 37%. Flows below this level
will produce an oxygen enrichment greater than 37% oxygen. This higher oxygen
level causes the flame to become too hot with a consequent increase in noise. This
increased noise can be nullified, without loss of sensitivity, by decreasing the
hydrogen flow slightly.
6.5 Those chromatographers actively using flame ionization detectors with pure air
generators having “B” reactors experience a response from three to ten times
greater than the response of the same detector with cylinder air, particularly if
nitrogen is used as the carrier gas. The magnitude of this increased response will
depend upon the particular detector. The substitution of nitrogen for helium carrier
gas will also improve resolution within the GC column. The more dense the carrier
gas the better the resolution.
12

6.6 When operating any pure air generator which has a “B” reactor, mixer-receivers
must be incorporated in the system. These units, Figures 5 and 8 (10), are located
after the purification reactor, and before the output pressure regulator (see Figure
10). They mount within the generator cabinets. Their purpose is to homogenize the
oxygen/nitrogen effluent developed by the “B” reactor. It is imperative that no other
chamber be used for this purpose and that this chamber remain empty.
6.7 The “B” purification reactor should not be used to produce air which is to serve as
diluent in the production of air blends, standards, etc., for air monitoring equipment.
Nor should it be used for instrumentation where air is used as the carrier gas or
support air, as with total hydrocarbon analyzers. The hyper oxygenation will cause
difficulties with calibration and the increased response will appear as hydrocarbon
response even though the air is hydrocarbon-free. The “A” or “C” purification
reactors should be utilized for these applications.
6.8 The “C” PURIFICATION REACTOR is identical with the “A” unit except that the
carbon dioxide concentration will be less than 0.3-ppm. This reactor is mandatory
in those situations where carbon dioxide is actually being measured; e.g.,
non dispersive infrared where the hydrocarbons and carbon monoxide are oxidized
to carbon dioxide before measurement, the moving wire liquid chromatograph
whereby all carbon dioxide is converted to methane and measured with flame
ionization detection, and those TOC systems employing the technique. For those
situations where the carbon dioxide serves as an interferant for the analysis of other
components, such as carbon monoxide, the “C” purification reactor must be used.
This is the preferred reactor for FTIR applications.
6.9 The “D” PURIFICATION REACTOR is for those applications requiring high purity
and extremely low moisture. It has the same performance specifications as the
other three reactors but has a moisture content of less than 1-ppm. lonmobility
analyzers and plasma chromatographs require this purification reactor. Other
applications include air supplies for automatic samplers, valves, and pneumatic
systems. The low moisture content eliminates maintenance problems with these
systems.
6.10 For those instances were pure air with high humidity is required, AADCO
Instruments, Inc. will supply a humidifier to be located after the pure air generator.
This device will operate under pressure and produce air with 50-90+% RH. This
addition alleviates the drying problem associated with the premapure dryer used in
some air monitoring instrumentation.
13

7.0 METHANE REACTORS.
7.1 The 737-40 series methane reactors are canisters, Figures 5 and 8 (2), containing
a low temperature catalyst, a heating system, and a temperature controller. The
system temperature is factory set at the optimum temperature for a destruction of
methane (about 290°C ± 10 °C). A cooling coil (9) is placed between the methane
reactor and the exit fitting labeled “PURE AIR” so that the temperature of the
effluent hydrocarbon free air does not exceed 40°C.
7.2 This reactor, when installed in any 737-series pure air generator, is electrically
controlled by the POWER switch located on the face of the generator unit. The
equilibration time from initial power is about sixty minutes. IT IS ADVISED THAT
NO INSTRUMENTATION BE CONNECTED TO THE PURE AIR GENERATOR
DURING THIS INTERVAL SINCE COPIOUS AMOUNTS OF WATER ARE DRIVEN
FROM THE CATALYST DURING THIS PERIOD.
7.3 During this initial “burn-in” a low flow of air should be permitted to pass through the
methane reactor to sweep the accumulated water from the reactor and effluent
tubing prior to connection to the using equipment. A rotameter reading of about
one quarter scale, set with the OUTPUT FLOW ADJUST, Figures 1 and 2 (10), and
about 20-psig output pressure, set with the OUTPUT PRESSURE REGULATOR,
Figures 1 and 6 (9), should be adequate.
7.4 The methane reactor will accommodate hydrocarbons, methane, and carbon
monoxide concentrations in air to 500-ppm. Most ambient levels are below 5-ppm.
The life span of the catalyst is almost indefinite though rapidly poisoned by
halogenated and sulfur compounds. It is for this reason that the methane reactor is
always located after the purification reactor (see Figure 10). The efficiency of the
methane reactor for methane is expressed by the nomograph on Figure 14.
7.5 The methane reactor is recommended for the generation of air which is to be
hydrocarbon and carbon monoxide free. It is widely used in determining ambient
methane levels, reactive versus non-reactive hydrocarbons, as source air for CO,
CH4, and THC analyzers, preparation of air blends, combustion air for TOC
analyzers, etc. A pure air generator with the “C” purification reactor is usually
employed in conjunction with the methane reactor for these applications. See
Section 6.8.
7.6 To remove the low level C02 formed during the catalytic reaction, AADCO
Instruments, Inc. offers an in-line, see through , C02-indicating scrubber (catalog
no. 737-120). This device is offered for those users who may be concerned with
this low level C02 and who have a genuine need for air which is completely C02
free.
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7.7 AADCO Instruments, Inc. offers free standing methane reactors (Models 153 and
154) for those individuals who wish to remove hydrocarbons and carbon monoxide
from their own oxygen or air sources. It should be borne in mind that suitable
halogen and sulfur scrubbers are required if these compounds are present when
using these free-standing units. The Models 154 and 154 are also ideal for
destroying the ethylene used as excitation gas for chemiluminescent ozone
analyzers rather than venting same within any monitoring enclosure.
7.8 The temperature of the methane reactor is monitored by the panel mounted
pyrometer, Figures 1 and 6 (11). Confirmation that the unit is operating at a
controlled temperature is made by observing the METHANE HEAT lamp (4) which
will cycle when at operating temperature. Should the pyrometer indicate some
erroneous temperature (other than 290°C ± 10°C), refer to Section 10.0, Trouble
Shooting, for remedial action.
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8.0 PERFORMANCE SPECIFICATIONS.
8.1 The AADCO 737-series pure air generators produce air with less than 0.005-ppm
hydrocarbons, carbon dioxide, methane, ozone, sulfur dioxide, hydrogen sulfide,
and oxides of nitrogen. Carbon dioxide level is either at ambient levels (~350-ppm)
or less than 0.3-ppm, depending upon the model purification reactor selected.
Dewpoint is at least -60°F; i.e., 20-ppm water or less.
8.2 Oxygen concentration of the output air is 20.8% ± 0.5% for the “A”, “C”, and “D”
purification reactors and 37.0% ± 0.5% for the “B” units. These respective oxygen
concentrations are determined at -60°F dewpoint, after the units have been in
operation for at least four hours and under conditions described in Section 8.7.
8.3 Source air may be from the oil-less compressor normally supplied with the
instrument, suitably filtered “house” or “plant” air, or any other source including
cylinders.
8.4 Hydrocarbon content of the unclean input air may be as great as 500-ppm and the
methane concentration to a maximum of 20-ppm. For those air sources containing
greater than 0.2-ppm methane, the AADCO 737-40, 737-41, etc., methane reactors
are recommended. The accessory units mount within the cabinets of all models
and completely remove all hydrocarbons, carbon monoxide, and methane by
converting these compounds to carbon dioxide and water. They are low
temperature catalytic oxidizers which, when properly installed, have effluent
temperature no greater than 40° C. See Section 7.0 for details.
8.5 Output pressure is maintained constant within 0.05-psig through the maximum
output pressure range of each instrument without the use of ballast tanks on the
outlet side of the pure air generator.
8.6 All 737-series pure air generators are calibrated for purity prior to shipment. They
are standardized for output purity and oxygen concentration against a factory
standard to assure consistent performance between all pure air generators. This
standardization is performed at an input pressure and output flow commensurate
with the rated output flow of the generator being tested. To reproduce this output
purity the operator must not exceed the maximum permissible output flow for this
unit and must have the proper input pressure and flow for same. All compressors
supplied with the 737-series pure air generators will meet or exceed the pressure
and flow requirements for the respective units.
8.7 Factory conditions for models 737-1 and 737R-1 are:
1-LPM output flow @ 30-psig, 50-psig input pressure.
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8.8 Any output flow greater than the stated maximum output flow for any particular
model pure air generator produces air with purity worse than specifications. A
nomograph is supplied (Figure 17) indicating output flow versus rotameter reading
at STP.
8.9 The operator must realize that once other equipment is connected to the pure air
generator and output flow is controlled at the other equipment, the rotameter will
then be pressurized and will indicate less flow than is actually being delivered.
8.10 Relevant direct rotameter readings can be made only without any equipment
connected to the output of the rotameter. This is because all rotameter calibrations
are performed at ambient pressure (in actuality @ STP). Once equipment is
connected to the PURE AIR fitting on the rear of the pure air generator the
rotameter now becomes pressurized and will no longer be direct reading.
8.11 The operator can quickly calculate actual flow even though the rotameter is
pressurized. To do so, note the output pressure and the rotameter reading. If the
output pressure is set at 15-psig, then the rotameter is at two atmospheres and
indicated rotameter reading will be one half the actual flow. In this instance, the
operator multiplies the indicated reading by two to find the actual flow.
8.12 If the output pressure is set at 30-psig and the rotameter indicates 50-mm, as an
example, then full flow is being taken from the unit since the rotameter is now two
atmospheres above ambient. This same rule of thumb will apply at other pressure
settings; i.e., at45-psig the rotameter reading should be no greater than 25% of full
scale.
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