Rosemount® 400A

Unstable or noisy readings may be symptomatic of a contaminated flow system.  Hydrocarbon contamination can occur in multiple areas: external components, like the fuel or air supplies, external frits and filters, regulators or supply tubing; internal flow components, such as pressure regulators and gauges; and finally, with water or condensation infiltration of the burner itself.

Contamination issues can be mitigated with intensive cleaning of the suspect components, or with their replacement.

The “+1” reading is indicative of an out-of-scale sensor response.

The 400A readout is a “percent of scale” display, which means that the display reads out the percentage of the scale of readings available under the current range setting.

If the analyzer’s current output voltage exceeds 200% of the current scale, the readout will return “+1”.

A quick check of the actual current sensor output is to increment the current range selected upward until the sensor output is no longer out-of-scale.   The set range multiples* (see: 400A Calculator) are instructive in determining the real sensor reading.

*Range multiples are variable if the optional 400A range trim board is installed.

(Describe likely diagnoses and specify possible confirmation testing, mitigation, and relevant RIGAS products or services)

Failure of the burner to ignite can be attributed to several separate (or contributing) factors.

Ignition failure can be due to issues with the supply gases: an insufficiently purged fuel supply, pressure regulators for the air and fuel supplies adjusted incorrectly or simply malfunctioning, or flow restrictions of the fuel and/or air into the burner assembly caused by clogging.

It can also be caused by internal electrical problems, such as faulty contacts and connections in the ignition circuit.

Finally, it may be caused by malfunctioning or failed components, such as the igniter itself, the transformer circuit, or the ignition switch.

(Describe likely diagnoses and specify possible confirmation testing, mitigation, and relevant RIGAS products or services)

This symptom shows up in different ways:
The readout shows an upscale reading with no flame present:

This unexpected reading is usually indicative of electrical leakage within the burner assembly.

The analyzer displays a loss in sensitivity, i.e, the same concentration of test gas reports a lower measured concentration over time:

This is often indicative of regular system degradation over long periods of time; the fuel and air supply systems (filters, restrictors, etc) as well as the sample restrictor and capillary can develop clogging, and the electrical elements of the burner can be partially short circuited, by extended operation without cleaning and rebuilds on the pertinent systems.

Further questions about day-day operation of your 400A can be answered with use of the RIGAS 400A Calculator Spreadsheet (PH).

RIGAS is equipped to diagnose and repair 400A analyzers in our Wooster, OH, office.

Please inquire for terms and instructions to ship your analyzer to RIGAS for service or repair.

Phone:
877.616.0600

Email:
[email protected]

Mail:
2310 East Hutton Rd
Wooster, OH 44691