Hazardous Area Requirements (with a case study) Presenters: Dan Alecu & Lovenah Galchoolah

Transcription

1 Hazardous Area Requirements (with a case study) Presenters: Dan Alecu & Lovenah Galchoolah

2 Infernal triangle The process of combustion can be represented by the fire triangle. Three factors are always needed to cause an explosion: 1. A source of ignition e.g. hot surface, arc or spark 2. Oxygen 3. Flammable material A hazardous area is an area in which an explosive gas mixture is present or may be present in sufficient quantities to require special precautions in the life cycle of the equipment that could create an ignition source.

3 Electrical equipment in hazardous areas (EEHA) If any side of the triangle is removed, a fire cannot be started or an existing fire cannot continue to burn. This forms the basis of design of electrical equipment in hazardous areas. Various protection techniques exist: Ex d, flameproof-explosion containment Ex e, increased safety-exclusion of arcs or sparks or hot surface Ex n, non sparking-avoidance of ignition source Ex i, intrinsic safety- Energy limitation

4 Hazardous area classification Zone depends the probability of the explosive gas atmosphere being present Zone 0-present continuously (>1000hr per annum) Zone 1-likely to occur in normal operation (between 10 and 1000hr per annum) Zone 2-not likely to occur in normal operation (less than 10hr per annum) Gas Group depends on ignition energy of the gas present IIA-Representative gas: propane IIB-Representative gas: ethylene IIC-Representative gas: hydrogen Temperature class (T1-T6) depends on auto ignition temperature of the gas present

5 Australian Standards AS 3000 is mandatory and mentioned in Regulations of numerous Acts of Parliament. AS 3000 calls up AS2381 with regards to the design, selection and installation of electrical equipment in hazardous areas. AS 2381 makes reference to various other standards for example AS series and AS 2380 and hence these standards become mandatory. All Ex inspections to be carried out by competent people as per AS 2381 clause 1.7.

6 Ex inspections Flowchart to determine periodic inspection interval:

7 Exd inspection findings Ex d enclosure works on explosion containment Common issues are: Extra unauthorised entries in enclosure Missing or damaged bolts Corroded junction box Damaged box along flamepath

8 Exe inspection findings Exe works on ignition avoidance Common issues are: Non certified terminals inside JB Absence of IP washer Loose conductor terminations create hot spots IP54 (min) enclosure

9 CASE STUDY ON MOTORS

10 CASE STUDY ON MOTORS It is strongly recommended that the relevant IEC, Australian Standards and Statutory Authorities be consulted prior to final selection of the motor including: Ex d Group I - Combination of Gas & Dust Ex d Group IIA, IIB & IIC - Combination of Gas & Dust Ex d Single Phase 240Volt Ex d HighVoltage EX d Brake &Two Speed Ex td ( Formerly DIP) -Dust Excluding Ignition Proof Ex d Forced Cooled Inverter Duty Ex e - Increased Safety Motors EX na - Non Sparking Motors

11 CASE STUDY ON MOTORS It is strongly recommended that the relevant IEC, Australian Standards and Statutory Authorities be consulted prior to final selection of the motor including: Ex d Group I - Combination of Gas & Dust Ex d Group IIA, IIB & IIC - Combination of Gas & Dust Ex d Single Phase 240Volt Ex d HighVoltage EX d Brake &Two Speed Ex td ( Formerly DIP) -Dust Excluding Ignition Proof Ex d Forced Cooled Inverter Duty Ex e - Increased Safety Motors EX na - Non Sparking Motors

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20 CASE STUDY ON MOTORS Temperature Tolerance Class Maximum Operation Temperature Allowed Allowable Allowable Temperature Temperature Rise at full Rise load 1.15 service 1.0 service factor motor 1) factor motor 1) oc of oc oc A B F H

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