Back to the Basics: Fault Detection

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. 



Back to the Basics: Frequency of Calibration

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. 

Back to the Basics: Safety Audits

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.

Back to the Basics: Duct Mounting and Sample Probes

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.