| Size and weight do matter with NeSSI. Because our | | | | can monitor valve performance. Use of close-coupled |
| plan is to get the pneumatic equipment by-line (i.e., | | | | systems and smart sensors allows us to simplify our |
| next to the sampling point), it's important that a | | | | systems and reduce size and costs by minimizing the |
| system is small and light so that service can be done | | | | need for double-block-and-bleed stream-switching |
| on a replacement basis. Today we have the ability to | | | | hardware. This also frees us from the burden of |
| fabricate modular miniature systems that should be | | | | providing visual indications of leakage. |
| able to be assembled Lego-style by an unskilled | | | | |
| person. | | | | Rotameter Replacement: NeSSI-bus-enabledunit can |
| Yet in many cases we build modular systems that | | | | sense fluid flow, pressure and temperature,and serve |
| haven't been optimized for space or still require | | | | in Division 1/Zone 1 areas. |
| custom tubing work. We should aim to tightly | | | | Photo courtesy of Circor. |
| integrate the modular system with its enclosure, to | | | | Use of visual indication devices such as rotameters |
| reduce size and weight, as well as eliminate custom | | | | and pressure gauges. We're addicted to their usage |
| tubing. Use of graphical indication of the flow paths | | | | because we've felt a need to "see" the process fluid. |
| certainly will overcome reluctance to use a densely | | | | However, as glass rotameters have given way to |
| populated sampling system. | | | | armored versions with magnetically coupled indicators, |
| Sample system design methodology. Software | | | | what we're getting now is an inferential view of the |
| configurator tools available for designing NeSSI | | | | flow. The new NeSSI-bus-compliant flow devices can |
| systems ultimately will expand to include the heaters, | | | | transmit flow or pressure signals. |
| the microclimate enclosure, the wiring | | | | If you have a signal that's available on a graphical |
| interconnections and the applets specified for the | | | | user interface you really don't need an indicator. |
| SAM. These tools will allow an end user to do a rapid | | | | Maybe it's time to remove the windows from our |
| detail design of a sample system based on company | | | | sample system enclosures and get a smaller |
| best practice and generate a detailed bill of materials | | | | transmitter in their place. Eliminating the rotameter |
| and estimate. | | | | also does away with an aggravating position |
| Because the NeSSI bus is intrinsically safe, use of | | | | constraint that dictates vertical positioning of the |
| pre-certified components allows us to virtually | | | | sample system. |
| self-certify our system as an entity regardless of | | | | Use of manual flow and pressure regulators. A |
| where in the world the system is installed. The | | | | rotameter generally comes with a needle valve, |
| assembler or integrator now will be able to validate | | | | allowing manual flow adjustment by analyzer |
| the automated performance and operation of the | | | | technicians. So, how can we adjust flow without a |
| sample system as part of the check-out procedure | | | | rotameter? Work is underway to supply a |
| by enabling self-checking routines available in the SAM. | | | | proportional valve coupled to a flow or pressure |
| Contrast that to current designs where much of the | | | | transmitter to give a real control loop on the sample |
| detailed design is farmed out and systems are mainly | | | | system. This will allow us to monitor the flow using |
| checked only for mechanical operation. | | | | proportional-integral-derivative (PID) control and also |
| Stream switching norms. For sample and calibration | | | | input a set point. |
| validation fluid switching, we often use | | | | Consider the great strides gas chromatograph |
| double-block-and-bleed stream-switching valves with | | | | manufacturers have made with carrier-gas pressure |
| bubbler systems to indicate a leak. This mandates | | | | controls. The days of matching flows using needle |
| maintenance rounds to regularly check if there's a | | | | valves are history. Thankfully needle valves used in |
| leak at the bubbler. Use of miniature, modular | | | | the majority of process gas chromatographs have |
| close-coupled systems minimizes upswept voids; the | | | | been consigned to the obsolete parts bin. |
| need for double-block-and-bleed valves to reduce | | | | Shows a NeSSI-bus-enabled valve control module for |
| dead volume all of sudden becomes less important. | | | | actuating sample-system pneumatic valves as well as |
| Another reason for multiple valves has been to | | | | a NeSSI-bus-enabled pressure/temperature |
| compensate for leaky valves that were standard | | | | transmitter. The module is rated Division 1/Zone 1 and |
| fare in the "bad old days." | | | | so can be mounted inside a sample system enclosure. |
| Early stream-select valves were ball valves with poor | | | | When used with a gas chromatograph it can obviate |
| seating — later followed by explosion-proof | | | | separate pneumatic tubes between the |
| solenoid valves that probably were even worse. | | | | chromatograph and the sample system. A single cable |
| Today we have better valves (see "Streamline Your | | | | connection links the gas chromatograph to the valve |
| Sampling System," | | | | control module. |
| And if they leak smart flow and pressure sensors | | | | |