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Sample Stream Selection System - DROP IN SOLUTION MSS/ISS 
As it 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 orders 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.
As 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.
A sampling system must meet these criterias:
- Compact design: - reduces enclosure and housing costs;
- Leak proof, Air diffusion resistant;
- No sample stream cross contamination;
- Small gas volume;
- No dead or unswepted dead volume:
- eliminates virtual leaks;
- reduces dry-down and purge time;
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- Ease of operation;
- Easy integration to an automatic process as remote control or automatic sample selection, calibration or truck loading operations;
- Sampling system must not change the nature of the sample media;
- Can be used with any type of process G.C. or on line process analyzers.
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The Conventional Way
- Engineering department must select all hardware, i.e. valves, tubing, etc.
- Purchasing department must give assembly contract to a panel builder.
- Panel certification shipping, on site installation and start-up.
The 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.
Our Way, Drop in Solution
- One stop buy;
- Engineering specifies how many inputs/outputs;
- Purchasing department issues one purchase order for a complete system;
- Systems are built, tested and shipped ready to use;
- No headaches. Plug and Play philosophy;
- Replaces complete sample panel, discrete valving system with one small 5 inch high rack mounted cabinet.
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In figure 1, the SV valves are miniature, low internal volume, manifold mounted two way sample selection valves. The FM flow meters and associated valves are used as bypass sample flow meters. Each inlet has its own 2 micron particle filter. The Rn calibrated flow restritors makes sure that there is an equal back purge flow through the stem of the SV valves. Back purge flows coming out of each stem of SV valves are summed up into one flow meter Fb, this one indicates the total back purge flow.
In 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 flow meter. The unselected sample stream valves have their discharge side and their stem back purged with the gas coming from the selected stream. The back purge flow is limited and controlled by its respective flow restrictor and flow meter Fb. This eliminates any unswept dead volume and speeds up upset recovery.
The output stabilisation loop allows a smooth, equilibrated flow and no dead volume. An optional back pressure regulator may be installed to maintain outlet pressure constant. Furthermore, for sample input, connect to calibration cylinder a special purge safety valve that can be added on these inlets to provide safety vent in case of cylinder regulator failure. This way, workers and equipments are protected. The purge on the pressure safety valve eliminates the dead volume created by the insertion of this valve. A small purge flow is kept constant, eliminating the possibilities of inboard contamination. This is a problem found in almost 100% of all conventional sampling systems equipped with that feature. |
Practically 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, can be mounted in an optional 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 meters and its associated valves are mounted in this case outside of the purged box. These parts are not critical for the sample contamination.
Designed to FITThe number of sample inlets can be 4, 6, 8, 10 or 12. Multiple outlets are also possible. If more sample streams are used, the outlet of a first MSS and ISS can feed the inlet of a second one. |
| Many users struggle with a tight budget to design a new sample stream selection system. The final result is often a system where the performances are poor. The MSS and ISS have a higher performance than the equivalent stainless steel diaphragm valves using welded joints. Such system is always based on tubing having 1/4" O.D. or higher resulting in a large volume of gas to be purged causing slow response time. The MSS and ISS have the price equivalent of a quick connector based system with the performance of a high end system. |
Integration into an existing or as a new systemThe MSS and ISS are the ideal solution for retrofit existing plants where quick connectors or rotary valves are used. It is easy and fast. The sample channel can be selected locally or remotely. When selected locally, the selected channel can be monitored by the remote control system to know witch sample number is selected. The automation job and retrofit has never been so easy and straight forward. What used to be weeks of work is now a matter of one day or two. The system can be remote controlled directly by standard digital output of any control system (PLC, DCS, etc..).
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Specifications may change without notice.
Patent Pending.
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High (mm) |
Deep (mm) |
Wide (mm) |
| Standard rack mount 3U |
5.25" (133.3) |
12" (304.8) |
19" (482.6) |
| Number of sample inlets |
4, 6, 8, 10 and 12 inlet versions |
| Bypass flow range |
0 to 1 liter/min |
| Back purge flow |
10 to 50 sccm for each channel |
| Gas connections |
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| Power |
- 85 VAC to 230 VAC, 50/60 Hz
- Maximum 10 watts
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| Inlet pressure range |
- Recommended minimum inlet pressure at 5 PSIG (35 Kpag)
- Maximum 65 PSIG (450 Kpag)
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| Valve rated life |
Minimum 500,000 actuations |
| Usable gas |
- N2, He, Ar, O2, H2, CO2, CH4, non condensable HC
- All noble gases
- No corrosive gases
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| Remote control voltage input |
12 VDC at 400 mA maximum |
| Standard features |
- Local or remote controlled
- Remote channel identification dry contact outputs
- Oxygen cleaned and compatible
- Outlet back purge flow
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| Options |
- Backpressure regulator mounted on the outlet to maintain constant pressure into analyzer’s inlet
- Manifold and valves mounted in a purge box
- Purged pressure safety valve on inlet used with high pressure cylinder (as calibration cylinder)
- RS-232 communication port
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| Warranty |
5 years full warranty |
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