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Coil coating line managers report that they experience three basic problems in solvent vapor monitoring: 

The Flame Temperature Analyzer has some important reliability features not found in other types:

The direct mounting of the analyzer to a process duct has two main benefits: 

1. eliminates the time delay associated with a long sample line 
2. makes it easier to keep the sample heated sufficiently to prevent condensation 

Even a very short section of relatively cold sample line can have a very serious effect on the analyzer accuracy and reliability.

The most notable feature of the Flame Temperature analyzer is the uniformity of response factors for a wide variety of combustible gases.

Due to the special requirements of analyzer systems, a yearly audit should be performed of the following analyzer records:

1. Installation 
2. Operation
3. Maintenance

This should be performed by a person who is an expert in the particular requirements of the analyzer and process, and who may be able to detect potential problems that otherwise might go undetected.

The most reliable method to test the sensor system is to inject a known concentration of test gas, as during calibration, and observe the reading and alarms.

In all analyzer systems, there is a possibility of undetected faults which might disable the analyzer's safety function. Therefore the greater the frequency of calibration and test, the lower the probability of an undetected analyzer fault. 

Automated test and calibration features in computer-based analyzer systems economically allow increased frequency of calibration and test, increasing reliability. 

Analyzers designed to industry standards incorporate malfunction indicators and relay outputs for most potential detectable faults, such as: 

• low sample flow 
• downscale reading
• electrical fault in sensor wire 

It is essential to connect these to the control system so that the operator is notified and the process reverts to a safe condition during an analyzer malfunction. 

While programmable controls and computers provide a great degree of convenience, unless these controls can be shown to conform to strict standards for the use of programmable devices in safety systems, it is preferable to use hard-wired connections for the critical alarm and analyzer malfunction signals. 

Where an analyzer’s signal controls the ventilation rate, it is particularly important to prevent a false control system during the “zero” portion of calibration, where zero gas is injected to the analyzer, forcing the analyzer’s signal to 0% LFL. 

This would force the control system to reduce ventilation to an unsafe level, since the analyzer, for the duration of the zero calibration, reports a false low solvent concentration.

In normal uses, most analyzers will require adjustment to their sensitivity to make up for a gradual reduction in sensitivity over time. 

The normal amount of adjustment of the signal should be well understood by the maintenance personnel so that problems other than loss of sensitivity are not corrected by the improper use of the "span" adjustment. 

For Example: