Approx. a month ago, the NSW Mine Dept. became aware of an issue with Alternators. This issue was in regards to Alternators producing voltages way in excess of their stated limits.

Manufacturers advise in their provided manuals that for a 12 Volt Alternator it would be impossible for the voltages to rise above 16 – 18 Volts depending upon the supplier, due to the DCBR card clamping and preventing anything above that.

Subsequent testing has highlighted spikes up to 45 Volts, with Nautitech’s independent testing showing even higher than that.

As per the NSW Dept. Safety Alert SA17-06, in regards to Alternators spiking, the industry has looked at connection downstream of the alternator. We recognise and would like to highlight our concerns along with the Regulator of the misleading information circulating.

Nautitech would like to give people in the industry regular updates on progress. Over the last month several Installers, Auditors and OEMs in NSW have requested feedback on these three points in regards to the Nautitech Methane Master. As Nautitech is the largest supplier of Methane Systems we feel we need to protect our IP, so cannot divulge everything to some requesters.

None of the points below are an issue:

1. The Nautitech methane system Battery is directly connected to the machine alternator and listed with a Um value of 24V. This value is stated on the component Certificate of Conformity(CoC) reference IECEx 14.0009X. After review of the IECEx 60079.11:2011 standard (Clause 7.5.1 Transient effects), it states that the semiconductor devices shall be capable of withstanding the peak of the a.c. voltage and the maximum d.c. voltage. By converting the listed Um from Vrms or Vdc to peak voltage as depicted by the standard reveals approximately 33.94V.

2. Closer inspection of the Nautitech 7.2V Battery Pack (Part Number ME50702-99-151, Ref CoC IECEx ITA 14.0009X) used to power the methane system, has a two terminal Non-Intrinsically safe (Non-I.S.) “alternator input” connection (JA-2) with a corresponding Um of 24V. The IECEx CoC states that this “alternator input “connection is also an Intrinsically Safe output. (reference IECEx ITA 14.0009X). If the alternator is not producing a voltage (Um=0), the I.S. outputs are applied to the Non-I.S. electrical equipment interfaced to the JA-2 terminals (for example Lights, Camera Systems, Hour Meters, Alternators etc.).

3. The wiring harness between the two Nautitech flameproof enclosures (ME5070-2-99-151 7.2V Battery Pack – IECEx ITA 14.0009X connecting to the ME5070-2-99-139 Remote CH4 Monitor – IECEx ITA 13.0021X) on the NTMS Hawkeye Master Methane System carries both I.S. and Non-I.S. electrical circuits in a single cable which is not allowed under AS/NZS 60079.25 – 2011 (Clause 8).

Nautitech can confirm that all of these questions from the field have been investigated, internally and with the CoC provider, and all of the above raised potential issues, are non-issues.

Due to the alternator’s poor performance, outside of their certification, Nautitech was forced to develop an Alternator Protection Device, to protect its equipment and circuitry from Spikes and Surges above the suppliers stated levels. This device will also protect anybody else’s equipment.

In addition to the APD device Nautitech can also arrange for training on its systems.

Contacts

Telephone: +61 2 9899 6857
Facsimile: +61 2 8456 6004
Email: sales@nautitech.com.au
Web Site: www.ntms.com
Manuel Cuevas – Quality Manager
Artur Gorski – Field Support Engineer NSW
Mitch Barnes – BDM QLD