is well known, the accuracy and reliability of process analyzers are
directly linked to the quality of the valves, manifolds, fittings and
various hardware used in the sampling system.
The best trace gas analyzer can’t have better performance than
the sampling system it is connected to.
In short, an analyzer is only as good as it’s sample system. By
many order of magnitude, today’s trace gas analyzers outperform the analyzers
designed 20 or 30 years ago and yet, it is not uncommon to find the same
sampling system design philosophy found 30 years ago.
For example, the quick connectors are still in use in many Air
Separation plants even with gas analyzers having ppb sensitivity.
a trace gas manufacturer, Contrôle Analytique reports that, more than
90% of its service calls are problems related to the sampling
system. It is obvious that
there is a need for a new approach concerning sample stream selection
systems and that this need is highly
addressed to the industrial gas industries.
design: - reduces enclosure and
proof, Air diffusion resistant;
sample stream cross contamination;
dead or unswepted dead volume:
- eliminates virtual leaks
- reduces dry-down and purge time
of operation; micro
processor, intelligent support
integration to an automatic process as remote control or automatic
sample selection, calibration or truck loading operations;
of serial communication with remote computer, PLC or DCS.
department must select all hardware, i.e. valves, tubing, etc.
department must give assembly contract to a panel builder.
certification shipping, on site installation and start-up.
conventional way requires the implication of many people from the
engineering department, the purchasing and third party contractors.
It is very expensive and prones to communication errors.
This type of system is bulky and the performances are variable.
specifies how many inputs/outputs;
department issues one purchase order for a complete system;
are built, tested and shipped ready to use.
headaches. Plug and Play
complete sample panel, discrete valving system with one small 5 inch high
rack mounted cabinet.
figure 1, the SV valves are miniature, low internal volume, manifold
mounted two way sample selection valves.
The FV valves and associated FT flow transducers are used as bypass
“electronic rotometers”. Each
inlet has its own 2 micron particle filter.
The FT-V flow transducer, monitors the outlet backpurge flow.
figure 1, sample #1 is selected, so SV-1 is open and SV-2 to SV-n are
closed. On each respective
sample inlet, there is a bypass flow that is
maintained by the microprocessor at the entered bypass flow set
point. So each FV bypass flow control valve maintains the bypass
flow at their respective set point. The
unselected sample stream valves have their discharge side backpurged
with the gas coming from the selected stream.
The backpurge flow is limited by its respective flow restrictor
“R”. This eliminates any
unswept dead volume and speeds up upset recovery.
output stabilisation loop allows a smooth, equilibrated flow and no dead
volume. Finally, an optional
electronic back pressure regulator may be installed to maintain outlet
all SV valves are mounted on a stainless steel manifold.
All gas inlets and outlets are welded on the manifold’s body.
Finally the manifold, holding the selection
SV valves, is mounted in a box that can be purged or maintained
under vacuum, based on application. This
eliminates completely the possibility of air diffusion into the system.
All other parts of the system like the inlet bypass flow control
valves and associated flow transducers are mounted outside of the purged
box. These parts are not
critical for the sample contamination.
system may be tailor made to fit the final application.
The number of sample inlets or outlets, the number of systems in a
software controls all the system operations.
The user interface is done through 4x4 keypad and 4x40 LCD display.
Upon power up, the user is prompted for inlet stream bypass flow
set point. Optionally, the
user enters back pressure set point if the system is equipped with an
electronic back pressure regulator.
user also enters identification tags for sample inlet.
The stream (or tag) to be sampled is selected by pressing the
associate number on the keypad. Automatic
sample stream sequencing can be configured.
The back purge flow is also displayed.
The software will issue an alarm when there is not enough flow
(pressure) from a sample stream inlet.
An appropriate digital dry contact output will be activated.
The software makes sure to close a valve before opening a newly
selected one to avoid cross flow. The
system has an isolated RS-232C communication port for interface with PLC,
DCS, computer, etc…
||User defined, up to 16.
Special configurations on request
||0 to 5 liter/min, resolution 1
||0 to 200 cc/min
1/8”, 1/4” or 3,4 or 6 mm.
- Double ferrules Swagelock® type
- Stainless steel compression fittings
VAC or 220 VAC, 50/60
Maximum 50 watts
He, Ar, O2, H2, CO2, CH4,
non condensable HC.
-All noble gases
-No corrosive gases.
Isolated RS-232C serial port with simple ASCII protocol
- Dry contact alarm outputs
User programmable time based sample stream sequencing or calibration
- Electronic sample inlets bypass flow controller
- Outlet backpurge
- Fully microprocessor controlled with 4 x 40 LCD
- Self-diagnostic system software
- Purged valve
- Oxygen cleaned
|| -Electronic backpressure
regulator to maintain constant outlet pressure.
may change without notice.