Aalborg DFC User manual

OPERATING MANUAL
DFC MASS FLOW CONTROLLER
Technical Data Sheet No. TD9805M Rev. O
Date of Issue: February 2012
aalborg
20 CORPORATE DRIVE =ORANGEBURG, NY 10962 =PHONE: [phone] =FAX: [phone]
e-mail: [email protected] =toll free in usa or canada: 1.800.866.3837 =web site: www.aalborg.com
7

CAUTION:
This product is not intended to be used in life support applications!
CAUTION:
K-Factors at best are only an approximation.
K-Factors should not be used in applications that require accuracy
better than +/- 5 to 10%.

TABLE OF CONTENTS
1. UNPACKING THE DFC MASS FLOW CONTROLLER........................
1.1 Inspect Package for External Damage..............................................
1.2 Unpack the Mass Flow Controller.......................................................
1.3 Returning Merchandise for Repair.....................................................
2. INSTALLATION....................................................................
2.1 Primary Gas Connections.................................................................
2.2 Electrical Connections......................................................................
2.3 Communication Parameters and Connections................................
3. PRINCIPLE OF OPERATION..................................................
4. SPECIFICATIONS..................................................................
4.1 DFC 26/36/46 Mass Flow Controllers..............................................
4.2 CE Compliance................................................................................
5. OPERATING INSTRUCTIONS.....................................................
5.1 Preparation and Warm Up................................................................
5.2 Flow Signal Output Readings..............................................................
5.3 Swamping Condition...........................................................................
5.4 Set Point Reference Signal .............................................................
5.5 Valve OFF Control ..........................................................................
5.6 Valve Open/Purge ............................................................................
5.7 Analog Interface Configuration...........................................................
6. MAINTENANCE...................................................................3
6.1 Introduction........................................................................................
6.2 Flow Path Cleaning..............................................................................
6.2.1 Restrictor Flow Element (RFE).................................................
6.2.2 DFC 26 models.........................................................................
6.2.3 DFC 36/46 models........................................................................
6.2.4 Valve Maintenance ...................................................................
7. CALIBRATION PROCEDURES....................................................
7.1 Flow Calibration...................................................................................
7.2 Calibration of DFC Mass Flow Controllers.......................................
8. TROUBLESHOOTING.............................................................
8.1 Common Conditions...........................................................................
8.2 Technical Assistance............................................................................
8.3 Troubleshooting Guide....................................................................
9. CALIBRATION CONVERSIONS FROM REFERENCE GASES................
1
1
1
1
1
1
2
2
6
6
7
8
11
11
11
11
12
12
12
13
13
13
14
14
14
14
15
15
15
16
17
17
17
18
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APPENDIX 1 COMPONENT DIAGRAM......................................................
APPENDIX 2 GAS FACTOR TABLE ("K" FACTORS).....................................
APPENDIX 3 DIMENSIONAL DRAWINGS..................................................
APPENDIX 4 SENDING COMMANDS TO THE DFC........................................
APPENDIX 5 SDPROC TABLES: GAS INDEPENDENT VARIABLES................
GAS DEPENDENT VARIABLES...............
APPENDIX 6 WARRANTY...........................................................................
21
25
29
31
37
39
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1. UNPACKING THE DFC MASS FLOW CONTROLLER
1.1 Inspect Package for External Damage
Your DFC Mass Flow Controller was carefully packed in a sturdy cardboard car-
ton, with anti-static cushioning materials to withstand shipping shock. Upon
receipt, inspect the package for possible external damage. In case of external
damage to the package contact the shipping company immediately.
1.2 Unpack the Mass Flow Controller
Open the carton carefully from the top and inspect for any sign of concealed ship-
ping damage. In addition to contacting the shipping carrier please forward a copy
of any damage report to your distributor or Aalborg7directly.
When unpacking the instrument please make sure that you have all the items indi-
cated on the Packing List. Please report any shortages promptly.
1.3 Returning Merchandise for Repair
Please contact the customer service representative of your distributor or Aalborg7
if you purchased your Mass Flow Controller directly, and request a Return
Authorization Number (RAN). Equipment returned without an RAN will not
be accepted. Aalborg7reserves the right to charge a fee to the customer for
equipment returned under warranty claims if the instruments are tested to be free
from warrantied defects.
Shipping charges are borne by the customer. Meters returned "collect" will not be
accepted!
It is mandatory that any equipment returned for servicing be purged and neutral-
ized of any dangerous contents including but not limited to toxic, bacterially infec-
tious, corrosive or radioactive substances. No work shall be performed on a
returned product unless the customer submits a fully executed, signed SAFETY
CERTIFICATE. Please request form from the Service Manager.
2. INSTALLATION
2.1 Primary Gas Connections
Please note that the DFC Mass Flow Controller will not operate with liquids. Only
clean gases are allowed to be introduced into the instrument. If gases are con-
taminated they must be filtered to prevent the introduction of impediments into the
sensor.
1
Caution: It is the users responsibility to determine if the instrument is
appropriate for their OXYGEN application, and for specifying O2
cleaning service if required. Aalborg is not liable for any damage or
personal injury, whatsoever, resulting from the use of this instrument
for oxygen.


Attitude sensitivity of the Mass Flow Controller is +15F.This means that the gas flow
path of the Flow Controller must be horizontal within those stated limits. Should
there be need for a different orientation of the meter, re-calibration may be neces-
sary. It is also preferable to install the DFC transducer in a stable environment, free
of frequent and sudden temperature changes, high moisture, and drafts.
Prior to connecting gas lines inspect all parts of the piping system including fer-
rules and fittings for dust or other contaminants.
Be sure to observe the direction of gas flow as indicated by the arrow on the front
of the meter when connecting the gas system to be monitored.
Insert tubing into the compression fittings until the ends of the properly sized tub-
ings home flush against the shoulders of the fittings. Compression fittings are to
be tightened according to the manufacturer's instructions to one and one quarter
turns. Avoid over tightening which will seriously damage the Restrictor Flow
Elements (RFE's)!
DFC transducers are supplied with standard 1/4 inch (DFC 26 and 36) or 3/8 inch
(DFC 46), or optional 1/8 inch inlet and outlet compression fittings which should not
be removed unless the meter is being cleaned or calibrated for a new flow range.
Using a Helium Leak Detector or other equivalent method perform a thorough
leak test of the entire system. (All DFC's are checked prior to shipment for leak-
age within stated limits. See specifications in this manual.)
2.2 Electrical Connections
DFC transducers require a +15VDC and -15VDC power supply to operate.
Additionally, a readout panel meter, digital multimeter, or other equivalent device
is required to observe the flow signal in analog mode. A variable analog 0-5VDC
reference input is required for DFC models to operate in analog mode. The
Aalborg7SDPROC accessory Command Modules offer a convenient and com-
pact means to fulfill these needs.
2.3 Communication Parameters and Connections
Baud rate: 9600 baud Stop bit: 1
Data bits: 8Parity: NON
RS-232 option: Crossover connection has to be established:
Pin 11 (TX) of the “D” connector has to be connected to RX
(pin 2 on the DB9 connector).
Pin 24 (RX) of the “D” connector has to be connected to TX
(pin 3 on the DB9 connector).
Pin 20 (Common) of the “D” connector has to be connected
to GND (pin 5 on the DB9 connector).
2

RS-485 option:
The RS485 converter/adapter has to be configured for: multidrop, 2 wire, half duplex
mode. The transmitter circuit has to be enabled by TD or RTS (depending on which
is available on the converter/adapter). Settings for the receiver circuit usually should
follow the selection made for the transmitter circuit in order to eliminate Echo.
Pin 11 (-) of the “D” connector has to be connected to
T- or R- on the RS-485 converter/adapter.
Pin 24 (+) of the “D” connector has to be connected to
T+ or R+ on the RS-485 converter/adapter.
Pin 20 (Common) of the “D” connector has to be connected
to GND on the RS-485 converter/adapter.
3

4
FIGURE b-1, WIRING DIAGRAM FOR DFC TRANSDUCERS.

PIN FUNCTION
1 +15 VDC Power Supply
2 0-5 VDC Flow Signal (4-20mA Option)
3 0-5 VDC Set Point Input (4-20mA Option)
4 Force Valve Open Control
5 Force Valve Closed Control
6 (Reserved)
7 (Reserved)
8 Relay No. 1 - Common Contact
9 Relay No. 1 - Normally Open Contact
10 Relay No. 2 - Normally Closed Contact
11 RS485 (-) (Optional RS232 TX)
12 (No Connection)
13 Chassis Ground
14 -15 VDC Power Supply
15 Common, Signal Ground For Pin 2
16 Common, Signal Ground For Pin 3
17 (Optional) RS232 Common
18 Common, Power Supply
19 Common
20 Common
21 Relay No. 1 - Normally Closed Contact
22 Relay No. 2 - Common Contact
23 Relay No. 2 - Normally Open Contact
24 RS485 (+) (Optional RS232 RX)
25 Return for Pin 2 (Optional 4-20 mA Only)
FIGURE b-2, DFC 25 PIN "D" CONNECTOR CONFIGURATION
Important notes:
In general, "D" Connector numbering patterns are standardized. There are, how-
ever, some connectors with nonconforming patterns and the numbering sequence
on your mating connector may or may not coincide with the numbering sequence
shown in our pin configuration table above. It is imperative that you match the
appropriate wires in accordance with the correct sequence regardless of the par-
ticular numbers displayed on your mating connector.
Make sure power is OFF when connecting or disconnecting any cables in the system.
The (+) and (-) power inputs are each protected by a 500mA M (medium time-lag)
resettable fuse. If a shorting condition or polarity reversal occurs, the fuse will cut
power to the flow transducer circuit. Disconnect the power to the unit, remove the
faulty condition, and reconnect the power. The fuse will reset once the faulty con-
dition has been removed.
Cable length may not exceed 9.5 feet (3 meters).
Use of the DFC flow transducer in a manner other than that specified in this manu-
al or in writing from Aalborg7, may impair the protection provided by the equipment.
5


3. PRINCIPLE OF OPERATION
The stream of gas entering the Mass Flow transducer is split by shunting a small
portion of the flow through a capillary stainless steel sensor tube. The remainder
of the gas flows through the primary flow conduit. The geometry of the primary
conduit and the sensor tube are designed to ensure laminar flow in each branch.
According to principles of fluid dynamics the flow rates of a gas in the two lami-
nar flow conduits are proportional to one another. Therefore, the flow rates meas-
ured in the sensor tube are directly proportional to the total flow through the trans-
ducer.
In order to sense the flow in the sensor tube, heat flux is introduced at two sec-
tions of the sensor tube by means of precision wound heater sensor coils. Heat is
transferred through the thin wall of the sensor tube to the gas flowing inside. As
gas flow takes place heat is carried by the gas stream from the upstream coil to
the downstream coil windings. The resultant temperature dependent resistance
differential is detected by the electronic control circuit. The measured gradient at
the sensor windings is linearly proportional to the instantaneous rate of flow tak-
ing place.
An output signal is generated that is a function of the amount of heat carried by
the gases to indicate mass molecular based flow rates.
Additionally, DFC model Mass Flow Controllers incorporate a microprocessor and
non-volatile memory that stores all calibration factors and directly controls a pro-
portionating solenoid valve.The digital closed loop control system of the DFC con-
tinuously compares the mass flow output with the selected flow rate. Deviations
from the set point are corrected by compensating valve adjustments, thus main-
taining the desired flow parameters with a high degree of accuracy.
Free PC Software with Gas Blending and Programmable Flow functions.
4. SPECIFICATIONS
FLOW MEDIUM: Please note that DFC Mass Flow Controllers are designed to
work with clean gases only. Never try to meter or control flow rates of liquids
with any DFC.
CALIBRATIONS: Performed at standard conditions [14.7 psia (1.01 bars) and 70F
F (21.1 FC)] unless otherwise requested or stated.
ENVIRONMENTAL (PER IEC 664): Installation Level II; Pollution Degree II.
6

4.1 DFC 26/36/46 Mass Flow Controllers
ACCURACY: +1% of full scale, including linearity for gas temperatures ranging from
59 FF to 77 FF (15 FC to 25 FC) and pressures of 10 to 60 psia (0.7 to 4.1 bars).
REPEATABILITY: +0.15% of full scale.
TEMPERATURE COEFFICIENT: 0.1% of full scale/ FC.
PRESSURE COEFFICIENT: 0.01% of full scale/psi (0.07 bar).
RESPONSE TIME: 1.0 to 2.0 second to within ±2% of set point over 20% to 100%
of full scale.
GAS PRESSURE: 1000 psig (68.9 bars) maximum; optimum pressure is 20 psig
(1.4 bars); 25 psig (1.7 bars gauge) for DFC46.
DIFFERENTIAL PRESSURES REQUIRED: 5 to 50 psig (0.35 to 3.34 bars) differential
pressures. Optimum differential pressure is 25 psid (1.7 bars). See Table IV for
pressure drops associated with various models and flow rates.
MAXIMUM PRESSURE DIFFERENTIAL: 50 psid for DFC26/DFC36, 40 psid for
DFC46.
GAS AND AMBIENT TEMPERATURE: 32 FF to 122 FF (0 FC to 50 FC). 14 FF to 122
FF (-10 FC to 50 FC) - Dry gases only.
RELATIVE GAS HUMIDITY: Up to 70%.
MAXIMUM INTERNAL LEAK: 0.5% FS.
LEAK INTEGRITY: 1 x 10-9 sccs He maximum to the outside environment.
ATTITUDE SENSITIVITY: 1% shift for a 90 degree rotation from horizontal to verti-
cal; standard calibration is in horizontal position.
OUTPUT SIGNALS: Linear 0-5 VDC (2000 Ωminimum load impedance); 4-20 mA
optional (50-500 Ω loop resistance); 20 mV peak to peak max noise.
Contact your distributor or Aalborg 7 for optional RS232 or IEEE488 interfaces.
COMMAND SIGNAL: 0-5 VDC (200K Ω input impedance); 4-20 mA optional.
TRANSDUCER INPUT POWER: DFC - +15 +5% VDC, 450 mA max, 6.75 watts max;
-15 +5% VDC, 450 mA max; 6.75 watts max;
Power inputs are each protected by a 500mA M (medium time-lag) resettable
fuse, and an inverse shunt rectifier diode for polarity protection.
WETTED MATERIALS: 316 stainless steel, 416 stainless steel, VITON7O-rings;
BUNA-N7, EPR or KALREZ7O-rings are optional.
7

Aalborg7makes no expressed or implied guarantees of corrosion resistance of
mass flow meters as pertains to different flow media reacting with components of
meters. It is the customers' sole responsibility to select the model suitable for a
particular gas based on the fluid contacting (wetted) materials offered in the dif-
ferent models.
INLET AND OUTLET CONNECTIONS: 1/4" (DFC 26/DFC36) or 3/8" (DFC46)
compression fittings standard. 1/8" (DFC26) or 3/8" (DFC26/DFC36)
compression fittings or 1/4" (DFC26/DFC36) VCR7fittings are optional.
TRANSDUCER INTERFACE CABLE: Flat cable with 25-pin "D" connectors on the ends
is standard. Optional shielded cable is available with male/female 25-pin "D" con-
nector ends. [Cable length may not exceed 9.5 feet (3 meters)].
FREE PC SOFTWARE WITH GAS BLENDING AND PROGRAMMABLE FLOW FUNCTIONS.
4.2 CE Compliance
Any model DFC bearing a CE marking on it, is in compliance with the below
stated test standards currently accepted.
EMC Compliance with 89/336/EEC as amended;
Emission Standard: EN 55011:1991, Group 1, Class A
Immunity Standard: EN 55082-1:1992
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FLOW RANGES
TABLE I DFC 26 LOW FLOW MASS FLOW CONTROLLERS*
TABLE II DFC 36 MEDIUM FLOW MASS FLOW CONTROLLERS*
TABLE III DFC 46 HIGH FLOW MASS FLOW CONTROLLERS*
* Flow rates are stated for Nitrogen at STP conditions [i.e. 70 FF (21.1 FC) at 1 atm].
For other gases use the K factor as a multiplier from APPENDIX 2.
9
CODE scc/min [N2]CODE std liters/min [N2]
01 0 to 10 07 0 to 1
02 0 to 20 08 0 to 2
03 0 to 50 09 0 to 5
04 0 to 100 10 0 to 10
05 0 to 200
06 0 to 500
CODE standard liters/min [N2]
11 0 to 15
30 20
31 30
32 40
33 50
CODE standard liters/min [N2]
40 60
41 80
42 100

TABLE IV PRESSURE DROPS
TABLE V APPROXIMATE WEIGHTS
10
MODEL FLOW RATE
[std liters/min]
MAXIMUM PRESSURE DROP
[mm H2O] [psid] [mbar]
DFC 26 up to 10 720 1.06 75
DFC 36
15 2630 3.87 266
20 1360 2.00 138
30 2380 3.50 241
40 3740 5.50 379
50 5440 8.00 551
DFC 46 60 7480 11.00 758
100 12850 18.89 1302
MODEL WEIGHT SHIPPING WEIGHT
DFC 26 transmitter 2.20 lbs (1.00 kg) 3.70 lbs (1.68 kg)
DFC 36/46 transmitter 2.84 lbs (1.29 kg) 4.34 lbs (1.97 kg)

5. OPERATING INSTRUCTIONS
5.1 Preparation and Warm Up
It is assumed that the Mass Flow Controller or Controller has been correctly
installed and thoroughly leak tested as described in section (2). Make sure the
flow source is OFF. Power up the transducer using your own power supply (or
switch the POWER switch to the ON position at the front panel of your SDPROC
Command Module). Allow the Mass Flow Meter or Controller to warm-up for a
minimum of 15 minutes.
During initial powering of the DFC transducer, the flow output signal will be indi-
cating a higher than usual output. This is indication that the DFC transducer has
not yet attained it's minimum operating temperature. This condition will automat-
ically cancel within a few minutes and the transducer should eventually zero.
5.2 Flow Signal Output Readings
The flow signal output can be viewed on the panel meter, digital multimeter, or
other display device used as shown in figure b-1.
When using the accessory SDPROC Command Module the flow rate will appear
on the display at the front panel. The observed reading is a 0 to 100% indication
(direct engineering units are optional). [If using a multichannel readout, be sure
that the CHANNEL selector switch is set to the correct channel.]
Analog output flow signals of 0 to 5 VDC or optional 4 to 20 mA are attained at
the appropriate pins the 25-pin "D" connector (see Figure b-2) on the side of the
DFC transducer. The output flow signal is also available at the DATA connector on
the rear panel of the SDPROC Command Module.
Meter signal output is linearly proportional to the mass molecular flow rate of the
gas being metered. The full scale range and gas for which your meter has been
calibrated are shown on the flow transducer's front label.
For information on the RS485 or optional RS232 interfaces please contact your
distributor or Aalborg7.
5.3 Swamping Condition
If a flow of more than 10% above the maximum flow rate of the Mass Flow
Controller is taking place, a condition known as "swamping" may occur. Readings
of a "swamped" meter cannot be assumed to be either accurate or linear. Flow
must be restored to below 110% of maximum meter range. Once flow rates are
lowered to within calibrated range, the swamping condition will end. Operation of
the meter above 110% of maximum calibrated flow may increase recovery time.
11
Caution: If the valve is left in the AUTO (control) or OPEN mode for an
extended period of time, it may become warm or even hot to the touch.
Use care in avoiding direct contact with the valve during operation.


5.4 Set Point Reference Signal
DFC flow controllers have a built-in solenoid valve and allow the user to set the
flow to any desired flow rate within the range of the particular model installed. This
valve is normally closed when no power is applied.
The set point input in analog mode responds to an analog 0 to 5 VDC reference
voltage or 4-20mA reference current. This voltage is a linear representation of 0
to 100% of the full scale mass flow rate. Response time to set point changes are
1 second to within 2% of the final flow over 25 to 100% of full scale.
A variable 0 to 5VDC analog signal may be applied directly to the SET POINT and
COMMON connections of the DFC transducer (see Figure b-1).
If a potentiometer is used to adjust the set point reference signal its value should
be between 5K to 100K ohm and it should be capable of at least 10-turns or more
for adjustment.
5.5 Valve OFF Control
It may, at times, be desirable to set the flow and maintain that setting while being
able to turn the flow control valve off and on again. This can be accomplished via
pin 5 on the 25-pin "D" connector. When 0 VDC (LOW) signal is applied (connection
via a relay, switch or NPN open collector transistor is permissible), the solenoid
valve is not powered and therefore will remain normally closed. Conversely, when
the pin is disconnected from 0 VDC ("floating”) the solenoid valve will remain active.
The simplest means for utilizing the VALVE OFF control feature, is to connect a
toggle switch between the COMMON and FORCE VALVE CLOSED pins of the
DFC transducer. Toggling the switch on and off will allow for activating and deac-
tivating the solenoid valve.
5.6 Valve Open /Purge
At times, it may be necessary to purge the flow system with a neutralizing gas
such as pure dry nitrogen. The DFC transducer is capable of a full open condition
for the solenoid valve, regardless of set point conditions. Connecting the FORCE
VALVE OPEN pin (pin 4 on 25-pin "D" connector) to ground will fully open the
valve. This connection can be made with a relay, switch or NPN open collector
transistor. Conversely, when the pin is disconnected from 0 VDC ("floating”) the
solenoid valve will remain active. (Note: in digital mode hardware I/O overrides
software command).
The simplest means for utilizing the VALVE OPEN control feature, is to connect a tog-
gle switch between the COMMON and FORCE VALVE OPEN pins of the DFC trans-
ducer. Toggling the switch on will cause the valve to open fully and purge the system.
Toggling the switch off will allow the solenoid valve to resume normal activity.
12
Caution: If the valve is left in the AUTO (control) or OPEN mode for an
extended period of time, it may become warm or even hot to the touch.
Use care in avoiding direct contact with the valve during operation.


5.7 Analog Interface Configuration
The DFC can be configured for the desired range and scaling by selection of
analog board (see APPENDIX 1 on page 21) jumpers as follows:
0 to 5 V output: Jumper pins 2 and 3 of JP6.
Jumper pins 2 and 3 of JP3.
Jumper pins 2 and 3 of JP5.
Jumper pins 1 and 2 of JP12.
0 to 5 V input: Jumper pins 2 and 3 of JP2.
Jumper pins 2 and 3 of JP4.
Jumper pins 1 and 2 of JP11.
0 to 10 V output: As for 0 to 5V, but jumper pins 2 and 3 of JP12.
4 to 20 mA output:Jumper pins 1 and 2 of JP6.
Jumper pins 1 and 2 of JP3.
Jumper pins 1 and 2 of JP5.
Jumper pins 1 and 2 of JP12.
4 to 20 mA input: Jumper pins 1 and 2 of JP2.
Jumper pins 1 and 2 of JP4.
Jumper pins 1 and 2 of JP11.
By default the DFC is configured for analog input output ranges set to 0-5V
(unless ordered with special configuration).
6. MAINTENANCE
6.1 Introduction
It is important that the Mass Flow Controller is used with clean, filtered gases only.
Liquids may not be metered. Since the RTD sensor consists, in part, of a small cap-
illary stainless steel tube, it is prone to occlusion due to impediments or gas crys-
tallization. Other flow passages are also easily obstructed. Therefore, great care
must be exercised to avoid the introduction of any potential flow impediment. To
protect the instrument a 50 micron (DFC26) or 60 micron (DFC36/46) filter is built
into the inlet of the flow transducer. The filter screen and the flow paths may require
occasional cleaning as described below. There is no other recommended mainte-
nance required. It is good practice, however, to keep the meter away from vibration,
hot or corrosive environments and excessive RF or magnetic interference.
If periodic calibrations are required they should be performed by qualified per-
sonnel and calibrating instruments, as described in section (7). It is recommend-
ed that units are returned to Aalborg7for repair service and calibration.
13
CAUTION: TO PROTECT SERVICING PERSONNEL IT IS MANDATORY
THAT ANY INSTRUMENT BEING SERVICED IS COMPLETELY
PURGED AND NEUTRALIZED OF TOXIC, BACTERIOLOGICALLY
INFECTED, CORROSIVE OR RADIOACTIVE CONTENTS.


6.2 Flow Path Cleaning
Before attempting any disassembly of the unit for cleaning, try inspecting the flow
paths by looking into the inlet and outlet ends of the meter for any debris that may
be clogging the flow through the meter. Remove debris as necessary. If the flow
path is not unclogged, then proceed with steps below.
Do not attempt to disassemble the sensor. If blockage of the sensor tube is not
alleviated by flushing through with cleaning fluids, please return meter to Aalborg7
for servicing.
6.2.1 Restrictor Flow Element (RFE)
The Restrictor Flow Element (RFE) is a precision flow divider inside the trans-
ducer, which splits the inlet gas flow by a preset amount to the sensor and main
flow paths. The particular RFE used in a given Mass Flow Controller depends on
the gas and flow range of the instrument.
6.2.2 DFC 26 models
Unscrew the inlet compression fitting of meter. Note that the Restrictor Flow
Element (RFE) is connected to the inlet fitting.
Carefully disassemble the RFE from the inlet connection. The 50 micron filter
screen will now become visible. Push the screen out through the inlet fitting. Clean
or replace each of the removed parts as necessary. If alcohol is used for clean-
ing, allow time for drying.
Inspect the flow path inside the transducer for any visible signs of contaminants.
If necessary, flush the flow path through with alcohol. Thoroughly dry the flow
paths by flowing clean dry gas through.
Carefully re-install the RFE and inlet fitting, avoiding any twisting and deforming
the RFE. Be sure that no dust has collected on the O-ring seal.
It is advisable that at least one calibration point be checked after re installing the
inlet fitting - see section (7).
6.2.3 DFC 36/46 models
Unscrew the four socket head cap screws (two 10-24 and two 6-32) at the inlet
side of the meter. This will release the short square block containing the inlet com-
pression fitting.
The 60 micron filter screen will now become visible. Remove the screen. DO NOT
remove the RFE inside the flow transducer! Clean or replace each of the removed
parts as necessary. If alcohol is used for cleaning, allow time for drying.
14
Note: Overtightening will deform and render the RFE defective.


Inspect the flow path inside the transducer for any visible signs of contaminants.
If necessary, flush the flow path through with alcohol. Thoroughly dry the flow
paths by flowing clean dry gas through.
Re-install the inlet parts and filter screen. Be sure that no dust has collected on
the O-ring seal.
It is advisable that at least one calibration point be checked after re installing the
inlet fitting - see section (7).
6.2.4 Valve Maintenance (DFC)
The solenoid valve consists of 316 and 416 stainless steel, and VITON7(or
optional EPR or KALREZ7) O-rings and seals. No regular maintenance is required
except for periodic cleaning.
Various corrosive gases may demand more frequent replacement of VITON7
O- rings and seals inside the valve. Be sure to use an elastomer material, appro-
priate for your specific gas application. Contact your distributor or Aalborg7for
optional sealing materials available.
Set the DFC into PURGE mode, and attempt to flush through with a clean, fil-
tered, and neutral gas such as nitrogen. [Another option for fully opening the valve
is to remove the plastic cap on top of the valve, and turn the set screw counter-
clockwise until it stops. Set valve for the closed position. Apply an inlet pressure
of 5 psig and atmospheric pressure at the outlet. If a small flow occurs, turn the
set screw on top of the solenoid valve clockwise until the flow through the DFC
just stops.
7. CALIBRATION PROCEDURES
7.1 Flow Calibration
Aalborg7Instruments' Flow Calibration Laboratory offers professional calibration
support for Mass Flow Meters and Controllers, using precision calibrators under
strictly controlled conditions. NIST traceable calibrations are available.
Calibrations can also be performed at customers' site using available standards.
Factory calibrations are performed using NIST traceable precision volumetric cal-
ibrators incorporating liquid sealed frictionless actuators.
Generally, calibrations are performed using dry nitrogen gas. The calibration can
then be corrected to the appropriate gas desired based on relative correction [K]
factors shown in the gas factor table see Appendix 2. A reference gas, other than
nitrogen, may be used to closer approximate the flow characteristics of certain
gases. This practice is recommended when a reference gas is found with ther-
modynamic properties similar to the actual gas under consideration. The appro-
15
Note: Removal of the factory installed calibration seals and/or any
adjustments made to the meter, as described in this section, will void
any calibration warranty applicable.


priate relative correction factor should be recalculated see section (9).
It is standard practice to calibrate Mass Flow Meters/Controllers with dry nitrogen
gas at 70 FF (21.1EC), 20 psig (1.4 bars) [25 psig (1.7 bars) for DFC46] inlet pres-
sure and 0 psig (0 bar) outlet pressure. It is best to calibrate the DFC transducers
to actual operating conditions. Specific gas calibrations of non-toxic and non-cor-
rosive gases are available at specific conditions. Please contact your distributor or
Aalborg7for a price quotation.
It is recommended that a flow calibrator of at least four times better collective accu-
racy than that of the Mass Flow Controller to be calibrated be used. Equipment
required for calibration includes a flow calibration standard and a certified high
sensitivity multimeter (which together have a collective accuracy of +0.25% or bet-
ter), an insulated (plastic) screwdriver, a flow regulator (example: metering needle
valve) installed upstream from the Mass Flow Controller and a pressure regulated
source of dry filtered nitrogen gas (or other suitable reference gas).
The gas and ambient temperature, as well as inlet and outlet pressure conditions
should be set up in accordance with actual operating conditions.
7.2 Calibration of DFC Mass Flow Controllers
All adjustments to the DFC calibration and control loop tuning are accomplished
using the RS485 (or optional RS232) interface in conjunction with setup and cal-
ibration software available from Aalborg7. The sensor zero is automatically
adjusted internally whenever the control valve is fully closed (set point less than
2% of full scale) and the unit is warmed up.
DFC Mass Flow Meters may be field recalibrated/checked using the setup and
calibration program for the same range they were originally factory calibrated for.
Flow range changes may require a different Restrictor Flow Element (RFE).
Additionally, a different Solenoid Valve Orifice for the DFC Mass Flow Controller
(see Table VI) may also be required. Consult your distributor or Aalborg7for more
information.
TABLE VI DFC SOLENOID VALVE ORIFICE SELECTION TABLE
16
ORIFICE PART NUMBER FLOW RATE [N2]
OR.020 10 to 1000 sccm
OR.040 1 to 5 slpm
OR.055 5 to 10 slpm
OR.063 10 to 15 slpm
OR.094 20 to 50 slpm
OR.125 50 to 100 slpm