Building an Analyzer System Project involves various aspects of plant operations and needs inputs from various disciplines. An Analyzer System Project Engineer faces the task of managing interface engineering with at least the Instrumentation, Electrical, Piping and Process departments. All this is done while pushing ahead the design and approval process for sampling systems, HVAC, power distribution, fire and gas detection, safety system etc.
Electrically heated sample transportation tube (popularly known as bundles or hoses) takes typically a back seat in the larger project scenario, due to various reasons. Sample tubes are not typically required till the construction phase starts at site. More often than not errors in bundle design or selection surfaces when the analyzer system is under commissioning. That is a time when it is too late for complete corrective action and more often than not things are patched up and left for review at a later date. When the problem gets severe, it leaves the end user frustrated and the system integrator looking for immediate answers.
More often than not we see project enquiry specifications that look like this ….
¼”, SS316L, 65 Deg maintain, Zone 2, 720 Mtrs.
There is a lot more information that is required to prepare a flawless quote, and provide value addition in terms of engineering inputs. We will dwell more on these aspects rather than on the nuts and bolts of the design itself.
Power supply is obviously important part of the specification. However, for obvious reasons it is best to have a high voltage supply. This is even more important to avoid multiple power supply feeders on simple applications. For example 120 VAC power supply should be avoided for sample heat tracing if 208 VAC is available at site.
Maintain temperature, obviously needs to be specified to help select the tracer size and insulation thickness.
Ambient temperatures (Min & Max) are equally important to the design of the bundle. It is based on the minimum ambient temperature that the heated bundle is fundamentally designed.
Important: A bundle maintaining 65 Deg C used in Russia will be quite different from a bundle maintaining 65 Deg C in Malaysia.
Maximum ambient temperature helps determine the maximum sample temperature maintained in the tube. It also helps determine if the insulation thickness if enough to ensure jacket temperature is within personnel safety norms.
The maximum sample temperature helps in determining if the selected heat tracer will survive any exposure to high temperatures that the sample brings in, especially closer to the sample take off point.
Hazardous Area Classification is most important to help select the right kind of components. Each area has different set of approved components especially the accessories. T-Rating is a key element on all kinds of heating systems.
Individual Tag Lengths when provided makes the most well-engineered quote that you can receive. When a lump sum project requirement of say 720 Mtrs is requested, it should be understood that the engineer making the quote does not know what kind or how many accessories are required. This leaves the onus to design, select and quantify the accessories on the analyzer project engineers. In the midst of a project, this is really his last priority. So if the analyzer bundle supplier is ready to do it for you, why not? It is best to list each line item separately, even if it is a 3 Mtr length between the sample probe and the Pressure Reducing Station. Once each and every sample tube run is identified as a line item, there is very little chance that the engineer will go wrong in quantifying the accessories. Further, when there are complex loops that also include, for example, a fire shut off valve on the analyzer house, the configuration can be as neat & user friendly as any other.
One of the most important outputs of the design process is the current rating. It is easily possible to determine the value of maximum current and operating current for each bundle run.
Important: On many project specifications it is specified that the maximum current rating for any field circuit shall not exceed 20 A and the maximum rating of the circuit breakers for parallel type heaters shall be 25 A.
Once again this is possible only when each bundle run is identified and quantified. The maximum current value is used to select the right sized circuit breaker for each line.
No information is too less when it comes to engineering a perfect project. It is only a question of putting it all together and understanding why each parameter is important.
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