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What is Your Plan if Your Opacity Monitor Stops Functioning, and You Can’t Operate Without One?

The 4500 MkIII opacity monitor from AMETEK Land is designed to give many years of reliable operation but sometimes breakdowns can happen. Many processes are not permitted to operate without a functioning opacity monitor, so it is important to have a plan in place for any downtime.

One of the best ways to handle downtime is with a temporary spare instrument. This is a provision of US EPA Procedure 3, Quality Assurance Requirements for Continuous Opacity Monitoring Systems at Stationary Sources. Paragraph 10.6 allows an operator to substitute a faulty instrument with an alternative monitor for up to 45 days while the original is either repaired or replaced with a new instrument. A temporary spare is an especially attractive option for users who have several stacks at a single site, or where nearby sites allow a single spare instrument to be shared.

The most important criterion for the temporary spare is that it must have a Manufacturer’s Certificate of Conformity stating that it has been tested according to the provisions of ASTM D6216, Standard Practice for Opacity Monitor Manufacturers to Certify Conformance with Design and Performance Specifications. To meet this requirement, the instrument will be configured and tested for one stack. If used as a temporary spare on that stack, or on one whose dimensions are the same within ± 2 %, no physical modifications are needed. If the dimensions differ by more than 2 %, the instrument must be configured and calibrated for those dimensions as described in the operating manual.  

This is followed by an abbreviated version of the performance tests required for a permanent installation – verifying the system’s linearity, response time, averaging function, and calibration drift. An important difference from the full start-up test is that the calibration drift test specifies seven calibration checks at 3-hour intervals so that the whole procedure can be completed within 24 hours.

Once the tests are complete and the data has been recorded in the site maintenance log, the temporary spare can be used for up to 45 days. That should be ample time to repair or replace the original instrument. It is not permissible to replace one temporary spare with another – the choices are to replace it with the original instrument or with a new, permanent unit.

An advantage of the temporary spare is that it is not usually necessary to include all parts of an opacity monitor in the spare. The most likely parts to fail are the transceiver and retroreflector as these are mounted directly on the stack and include all the optical and optoelectronic components. Therefore, you only need to keep a basic 4500 MkIII on the shelf to have the peace of mind that you can quickly and easily keep your process in compliance if your opacity monitor should fail.

Click here to learn more about the 4500 Mkiii


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