Phil Brown Presentation Exi SystemsX

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Phil Brown Presentation Exi SystemsX

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<ul><li><p>After AS2380.7 and AS2381.7</p><p>Philip Brown</p><p>Principal Engineer</p><p>Austdac Pty Ltd</p></li><li><p>New Ex i Standards AS2380.7 Equipment standard replaced by AS/NZS </p><p>60079-11 AS2381.7 Installation standard replaced by AS/NZS </p><p>2381.1 AS2381.7 Installation standard replaced by AS/NZS </p><p>60079-14 So where do we look when designing Group I Ex i</p><p>systems and installations?</p><p>2</p></li><li><p>The Ex i Systems Standard AS/NZS 60079-25</p><p> Provides information and rules about designing and </p><p>assessing Ex i systems using already certified equipment </p><p>with entity parameters and simple apparatus.</p><p> Provides information about documenting system designs </p><p>and installation requirements.</p><p> Also provides a standard to which a certifying body can </p><p>issue a certificate, if required.</p><p>3</p></li><li><p>Why a Systems Standard? The design and installation of Group I Ex i explosion </p><p>protected systems is far to important to be left to the </p><p>installation phase.</p><p> The system must be carefully designed, assessed and </p><p>documented prior to installation, to ensure maximum </p><p>safety of the mine installation.</p><p> AS/NZS 2381.1 and AS/NZS 60079-14 do not provide the </p><p>required level of rigour for a safe design and installation.</p><p> AS/NZS 60079-14 is mainly a group II standard.</p><p>4</p></li><li><p>AS/NZS 60079-25 Procedure DESIGN Put system together to suit functional </p><p>specification.</p><p> ASSESS Check system for Ex i safety, conduct risk </p><p>assessments on cables and determine their types.</p><p> DOCUMENT Show all aspects of design including </p><p>certified modules, simple apparatus, junction boxes, </p><p>entity parameters, cable types and cable parameters.</p><p> INSTALL Carry out installation in accordance with </p><p>documentation, if a change is required, repeat full </p><p>procedure, above all update documentation.</p><p>5</p></li><li><p>Descriptive System Document AS/NZS 60079-25 requires that a descriptive system </p><p>document or drawing be produced to show ALL aspects of the design and installation.</p><p> It should show all certified equipment connections, the entity parameters for each port, hazardous areas, safe areas, zones, cables with their types, parameters, routes and mechanical protection.</p><p> Satisfies DPI documentation / dossier requirements.</p><p> Change the document then the installation, not the other way around.</p><p>6</p></li><li><p>Descriptive System Document</p><p>7</p></li><li><p>Multi-core CablesAS/NZS 2381.7 AS/NZS 60079-25</p><p> Required individual i.s. circuit </p><p>screens for a system design to </p><p>occupy a multi-core cable.</p><p> Did not specify the faults to </p><p>be applied between individual </p><p>circuits when screens not </p><p>used.</p><p> The end user was forced to go </p><p>for an individual system </p><p>certification.</p><p> Allows individual i.s. circuit </p><p>screens for a system design </p><p>to occupy a multi-core cable.</p><p> Specifies the faults to be </p><p>applied between individual </p><p>circuits when screens not </p><p>used.</p><p> Allows a risk assessment </p><p>approach to which type of </p><p>multi-core cable can be used. </p><p>8</p></li><li><p>Multi-core Cable TypesAS/NZS 2381.7 AS/NZS 60079-25</p><p> Screened No faults need be </p><p>applied.</p><p> Unscreened All possible </p><p>(unspecified) faults shall be </p><p>applied.</p><p> Type A Screened No faults need be applied.</p><p> Type B Unscreened cable with low risk of damage No faults need be applied.</p><p> Type C Unscreened cable with high risk of damage Specified faults applied.</p><p> Type D Unscreened cable of inferior construction All possible (unspecified) faults applied.</p><p>9</p></li><li><p>Multi-core Cable Specified Faults</p><p> Four open circuit faults.</p><p> Two short circuit faults.</p><p> These are the minimum number and type of faults </p><p>required to cause voltage and current addition between </p><p>two independent i.s. circuits.</p><p> Voltage and current addition are the most ignition </p><p>capable scenarios that can occur in multi-core cable </p><p>damage.</p><p>10</p></li><li><p>Simple Intrinsically Safe Circuit</p><p>11</p></li><li><p>Type A Cable (screens)</p><p>12</p></li><li><p>Type B cable (Risk Assessment - Pass)</p><p>13</p></li><li><p>Risk Assessment Fail </p><p> Cable is now treated as a type C cable.</p><p> Therefore need to apply 2 short circuit faults and 4 open </p><p>circuit faults to determine safety of design.</p><p> Apply faults to obtain most unsafe conditions.</p><p> Maximum voltage (voltage addition).</p><p> Maximum current (current addition).</p><p> Take note of infallible connections of power supply </p><p>negative terminals prevents voltage addition. </p><p>14</p></li><li><p>Type C Cable (Voltage Addition)</p><p>15</p></li><li><p>Permitted Capacitance</p><p>16</p></li><li><p>Infallible Common Connections</p><p>17</p></li><li><p>Type C Cable (Current Addition)</p><p>18</p></li><li><p>Determining Lo/Ro</p><p>19</p></li><li><p>Conclusion</p><p> Ex i equipment standard AS/NZS 60079-11. Ex i system standard AS/NZS 60079-25. Installation standard AS/NZS 60079-14. Format of descriptive system document is now specified.</p><p> System designer now has the tools (specified faults) to </p><p>conduct an assessment of individual Ex i circuits in cables </p><p>without screens.</p><p>20</p></li><li><p>The End Questions</p><p> Thank you</p><p> Contact: philipb@austdac.com.au</p><p>21</p></li></ul>

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