Datanit probe - SCR SA

Datanit probe
� For all nitriding and nitrocarburizing processes
� For all types of furnaces, also low pressure furnaces
� Automatic calibration
� Uncomplicated conception
Description
The Datanit probe has been elaborated to measure precisely
and continuously :
� the nitriding potential kN in nitriding and nitrocarburizing
atmospheres;
� the carburizing potential kC in nitrocarburizing processes.
It also measures the oxygen potential kO when oxygen is
present, and during the post-oxidation. The probe works with all
kinds of furnaces, even low pressure furnaces, and requires no
special maintenance. The reproducibility of the measurements
is guaranteed by an automatic calibration, also testing the
whole probe.
The Datanit probe can be used as an atmosphere control
system in addition with a plc. It releases alarms when the
composition of the atmosphere is dangerous for the user.
Figure 1 − Schema of the Datanit probe.
1. Gas input 8. Venturi pump
2. Conductivity sensor R 9. Pneumatic valve
3. Oxygen sensor 10. Gas output
4. Cracker 11. Nitrogen input (valve)
5. Catalyst 12. Nitrogen input (pump)
6. Conductivity sensor C 13. Calibration gas input
7. Calibration gas input 14. Electronics
Measurement principle
The Datanit probe consists of three measurement sensors which
complete each other to measure the composition of a gas
mixture (see figure 1). The gas is pumped into the probe by
means of a nitrogen injection (Venturi effect). First, the gas
passes through a conductivity sensor (R for residual). Then, a
lambda probe measures the oxygen partial pressure. After-
wards the gas goes through a cracker, and then through a
second conductivity sensor (C for cracked). The two
conductivities and the oxygen partial pressure allows to
calculate the partial pressure of ammonia and hydrogen. The
partial pressure of the other gases (CO, CO2, N2, H2O) are
calculated according to equilibrium conditions. These
measurements, completed by the measurements of furnace
pressure and temperature, allows to calculate the
characteristic values :
xi is the molar fraction of the gas i and P the total pressure in
the furnace. The calculations consider the treatment
temperature.
During the post-oxidation, the probe must be closed because
of the conductivity sensors. An external lambda probe can be
installed on the furnace to compute the oxygen potential.
Technical characteristics
Precision
kN ± 0.1 bar -1/2
kC ± 0.01 bar
Measurement domain
Hydrogen 8% - 90% vol.
Ammonia 0% - 88 % vol.
Mounting position
Horizontal or vertical
SCR SA, Route cantonale 163a, CH-2944 Bonfol
info@scr-sa.ch, phone +41 32 474 47 27, fax +41 32 474 47 56, www.scr-sa.ch

Exterior influences
None for temperature and pressure. The probe is heated at a
temperature of 100°C.
Treatment range
Nitriding NH3 and two of the following gases : N2,
NH3 c , N2O
Nitrocarburizing NH3, N2 and two of the following gases :
Post-oxidation
CO2, endothermic gas, N2O, CH4, C3H8
In option with the second lambda probe (at furnace exit).
Measurement conditions
Furnace temperature 450°C - 650°C
200°C – 500°C in post-oxidation
Gas pressure 200 – 1300 mbar absolute
Temperature 10°C – 60°C
Relative humidity 10% - 80% without condensation
Fluid pressures
Nitrogen minimum 5 bar
Hydrogen 25% 0.8-1.5 bar
Hydrogen 75% 0.8-1.5 bar
Electrical power supply
230V ± 10V in a box 400 mm x 400 mm x 200 mm
Calculations
Calculations must be done in a plc. Algorithms exists for the
market leader plc.
Measurement signal
O2 4-20 mA / 0–5 V DC
Conductivity R 4-20 mA / 0–5 V DC
Conductivity C 4-20 mA / 0–5 V DC
Temperatures 4-20 mA / 0–5 V DC
Input-output needs in plc
16 DO, 2 AO, 9 AI
Other measurements
Furnace pressure
Internal temperature
115°C and 850°C for the cracker
Heating time
30 min
Calibration
With independent module and 2 calibration gases
Frequency before each treatment, minimum once week
Duration 30 min
Maintenance
No particular maintenance is necessary
Consumption
Electric max. 250 W
normal 100 W
Fluid hydrogen 4 l by calibration
Construction
Materials
nitrogen 4 l by calibration
Galvanized aluminium and stainless steel
Mechanical connection
On the furnace Balzers DN40
Electrical cabling
Harting 32 poles
Cabling for fluids
Swagelok 6mm
Dimensions
Length of the aspiration tube 0.5 m - 2 m
SCR SA, Route cantonale 163a, CH-2944 Bonfol
info@scr-sa.ch, phone +41 32 474 47 27, fax +41 32 474 47 56, www.scr-sa.ch
35 l by treatment hour
50 l by purge hour
External dimensions (H X L x L) 360 mm x 180 mm x 140 mm
Weight
9.8 kg
Figure 2 − Example of the Datanit probe on a pit furnace