Gas Sampling Probes Interpreting Smoke Signals

Author / Editor: Herbert Beck* / Wolfgang Ernhofer

Continuous emission monitoring by gas sampling probe — The saying “Every beginning is difficult” means a lot also in the field of Gas sampling probes and probe conditioning: if there is a problem in the direct connection to the process that is to be measured, the entire process analytics will cause problems, either in the calibration of the measured results or during the operation phase.

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Continuous Emission Monitoring Systems (CEMS) are facing many challenges at the same time: as a huge difference to the Process Analytic Technology, a CEMS project is often driven by legal requirements and not business case initiated. This circumstance leads into an enormous cost pressure situation: the investment costs have to be optimised but at the same time the operating costs are focussed on the Total Costs of Ownership Calculation. Good to know that the German Company PSG offers a full solution package for gas sampling probes and sample transportation lines.

What is the difference: Not the size matters, but the surface

The main difference of PSG Gas Sampling probes is represented in the inside of the probe: they have the biggest filter surface in the market by far — a very important fact and unique selling proposition for reliable Gas Sampling Probes. The big filter surface allows to reduce the operating costs significantly: the probes continue the measurement when the filter of competitive products have to be changed and cleaned. Next to the reduction of the financial effort in terms of operating costs, another advantage is the high availability which is often required by law and regulations.

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The core is the same – the concepts are different

The core inside of a gas sampling probe is the filter itself. The biggest filter surface, the grain size of 0,3 µm and the filter membrane made of mullite grains, provide the best technical prerequisites for an efficient gas sampling process. The difference is to be made by the layout and housing of the filter. Therefore, both PSG Probe product-lines were designed in order to reduce manual service procedures to the minimum and if a manual filter cleaning is unavoidable all service steps are to be handled without the need of additional tools.

Coming from the same origin the two concepts enable to offer a solution for nearly every need: the PSG basic was designed to serve applications with low or medium dust load. The very compact PSG basic Probe unites a unique combination of low investment and operating costs.

Next to this product-line, the PSG Plus probe focuses more complicated applications with middle to extreme dust load. Together with the two back purging options it can easily resist applications with extreme requirements such as waste combustion or cement works.

In order to achieve the main objective in designing a very economical solution without losing the core technical features the layout of the PSG Basic Probe is very compact. The redesign of the probe head represents a very innovative approach: the usage of a flange clamp allows a very compact layout and at the same time, the clamp has another important functions: during the operation it ensures tightness.

If the filter has to be cleaned or changed the intelligent flange clamp can be used to remove the filter head, even if a temperature drop or corrosion complicates the filter exchange. Therefore the flange clamp has to be moved from the first stage to the second and by using the screw of the clamp nearly no power and maybe more important no tools are needed.

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The PSG Basic Probe comes with a calibration port as standard in order to fulfil legal requirements. In case of middle dust load process applications, a single pack purging option can be chosen from the configuration matrix.

Not enough, more options required?

Other than the PSG Basic the PSG Plus Probe focuses applications with high technical requirements and middle up to high dust loadings. The opening and filter exchange mechanism is very easy to understand and to handle, a thermal disconnection to the hot parts of the probe is ensured. Needless to mention that all of these steps can be executed without the need of any tools. As standard configuration, the PSG Plus Probe comes with a calibration — or test gas port. In addition to this connection a double back purging option is available — together with the unique filter surface the perfect combination to operate the probe without the need of filter exchanges for a maximum operating time.

No matter which of the two product option meets users requirements in the best way: the choice of the weather protection box was made without any compromises: stainless steel ensures a long-term protection against all elements from outside. Other than competitors who decided to use cheaper materials such as Polyamide insulation sleeve a number of reasons made the final decision: For the outside installation, UV radiation makes the dryer go away which results into insulation problems.

Furthermore every open- and closing process causes stress to the material — not a problem for the PSG weather protection box. Last not least optical aspects are an additional argument: even after a long life the housing looks high-end.

Probe Sampling and Transportation from one hand

The high quality approach of the PSG Probes continues in the heating concept. A metal heating sleeve which is in direct contact of the probe allows operating temperatures from 180 °C to 200 °C and this under extreme outside conditions.

The temperature control and reputation concept allows two different options: It is either self-regulating by the integrated temperature controller or it can be controlled from outside (temperature sensor is a PT 100). For another critical temperature point, an innovative insulation sleeve is used: often the connection between the hot parts of the probe and the heated sample line is responsible for temperature drops and cold spots — due to the insulation sleeve and the intelligent heated caps of the sample lines another point not to worry about.

After a success primary gas sampling from the probe or process the way for the gas to the analyser or secondary probe sampling can be very long and holds various technical challenges: next to the temperature control concept long lengths of the lines up to 100 meter require intelligent solutions for the power supply. The flexible production allows the realisation of two or more heating circuits — only one of more than 2500 solutions.

Another advantage of heated sample lines is given by the fact, that PSG tube bundles can be shortened upon the users needs. Many users take advantage of this fact and order a sample line that is preconfigured on the power supply side — for the other side the confection set is added to the delivery.

* * The author is Division Head: Sample Gas Extractions Systems, Sample Lines at PSG Petro Service, Steinbach, Germany. Contact: Phone +49-6171-9750-0

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