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Reviews shall be carried out during the life of the plant. Note that in the cases of activities other than those of normal operation, e. It is expected that this would be dealt with by a safe system of work.
What are different grade of releases? Continuous grade of release Release which is continuous or is expected to occur frequently or for long period.
Primary grade of release Release which can be expected to occur periodically or occasionally during normal operation. Secondary grade of release Release which is NOT expected to occur in normal operation and, if it does occur, is likely to do so only infrequently and for short period.
A continuous grade of release normally leads to a zone 0, a primary grade to zone 1 and a secondary grade to zone 2. Type of ventilation, however, has impact on classification and may lead to different results. How is equipment grouping in hazardous area classification?
Equipment intended to be used in hazardous areas are categorized in three different groups. Group I Electrical equipment of group I is intended for use in mines susceptible to firedamp. Group II Electrical equipment of group II is intended to use in places with an explosive gas atmosphere other than mines susceptible to firedamp. Group II is applicable for gases and vapours. Mists which can form through leaks of liquid can be flammable even though the liquid temperature is below the flash point.
It is therefore important to ensure that clouds of mist do not occur. Group III Electrical equipment of group III is intended for use in places with an explosive dust atmosphere other than mines susceptible to firedamp. What is definition of EPL? EPL stands for Equipment Protection Level and is an assessment showing the suitability of equipment to be installed in hazardous areas.
Traditional relationship of EPLs to zones is as below no additional risk assessment risk assessment is required. This is not directly applicable for mines susceptible to firedamp, as the zone concept does not generally apply.
Ga equipment can be installed in zone 0, 1, 2 Gb equipment can be installed in zone 1, 2 Gc equipment can be installed in zone 2 Da equipment can be installed in zone 20, 21, 22 Db equipment can be installed in zone 21, 22 Dc equipment can be installed in zone 22 Where a risk assessment is carried out to assess consequences, Gb can be installed in zone 0, and Gc can be installed in zone 1.
Note that equipment EPL Mb is de-energised when explosive atmosphere present. Equipment other type of EPL than Mb, remains functioning when explosive atmosphere present.
Which type of gases must be considered lighter than air? For practical applications, a gas or vapor which has a relative density below 0. If the relative density is above 1. Between these values, both of these possibilities should be considered. Care needs to be taken when classifying areas containing cryogenic flammable gases such as liquefied natural gas. Vapors emitted can be heavier than air at low temperatures and become lighter than air on approaching ambient temperature.
Which rule applies to zones overlap? When zones created by adjacent source of release overlap and are of different zonal classification, the higher classification criteria will apply in the area of overlap.
Where overlapping zones are of the same classification, this common classification will normally apply. As they are not certified based on the same standards, Can I use them together in my design? There are Ex equipment certifying bodies accepted by Australian Industry. How these pieces of equipment can be used in Australia?
As EX nA is similar to the Ex e technique, is it necessary to document motor protection capability to disconnect the circuit in motor locked current condition for less than tE?
What if tE is not given in certificate in case of Ex nA? Ex nA is the same as Ex n and therefore it is not necessary to record any locked rotor trip times etc. In AS Shall this documentation be provided by manufacturer of motor, manufacturer of soft-starter or by designer? Is this documentation same as checking circuit protection considering tE same as EX e?
The Clause you have quoted Ex d is covered under Clause The information should be obtained from the Soft Starter manufacturer or by test and then you record the data. Must electrical consumers located in hazardous areas be protected via RCDs? Same standard, part 7.
Clause 7. RCDs are not required to protect motors etc. GPOs, lighting circuits etc. Should any special relay to be considered in motor feeders of which the motor is located in hazardous areas? Loss of phase for multiphase equipment is mandatory. Usually the motor overload takes care of this but if not then a phase loss relay must be installed or replace the overload with one that includes phase loss protection.
There is an EX-d motor in Zone 1 area need to be installed with a soft-starter. Considering the d-type of Ex protection, Does motor need to be protected by direct temperature control? You are correct. The motor may be protected by imbedded thermistors that disconnect the motor from supply. The problem is our Ex-d motor which is going to be installed in zone 1, and will run in association with the soft start device, does not have imbedded thermistors.
Sorry, must be direct imbedded thermistors. When the certificate for equipment expires what impact does this have on the equipment? Does this mean it cannot be installed if it has not been already been installed. Yes, the equipment is OK to use provided it was manufactured within the period of certification.
Note: This level of protection reduction takes account of the fact that the assessment is by calculation only without any test. It is for more than 1 associated device connected in an Ex ib installation not an Ex ia installation. If we have more than 1 associated device then their method of connection must be taken into account, for example 2 devices connected in series or parallel.
In series, the circuit current is affected while in parallel the circuit voltage is affected. Annex A2 must also be used in conjunction with Annex B1. See Annex 2 a as an example. This is not intended for any Ex ia installation. The Solenoid valves, in this case, are used to close or open big valves actuators by connecting gas pressure. While one of them is closing the actuator, another one release a small amount of gas confined in the tube. Is the operating medium gas or instrument air?
If it is gas, then the zone around the vents would be Zone 1 normal release but the flanges would still be zone 2 abnormal. What are definitions for thermal and dynamic current limits for Ex-e equipment? Thermal current limit Ith r.
Dynamic current limit Idyn Peak value of that current, the dynamic effect of which the electrical equipment can sustain without damage. What is the designed temperature range of Ex-e equipment?
Is there any recommendation for selection of cables used for Ex-e equipment? Where not specified, the current rating given in AS Note: it is recommended that, where each conductor carries its rated current, the bunch should not exceed 6 conductors AS Can non-metallic conduit systems be used in hazardous areas? Non-metallic conduit systems are not permitted in either Zone 0 or Zone 1 areas, but are permitted in Zone 2 areas. Unused cable entries shall be closed with plugs which maintain the degree of protection appropriate to the application, at no time less than IP Why Ex-e motors are rated less than normal motors with the same frame size?
When selecting an increased safety motor it should be born in mind that the output is less than that of a standard motor of the same frame size. Compliance with a minimum tE may necessitate an even more severe output limitation. Is there any limitation for tE in Australian standards? Please refer to AS What is the maximum permissible rotor temperature of Ex-e protected motors? What if starting time of the motor exceeds the tE time?
It is preferable that the starting time of the motor should not exceed the tE time to be quite certain that the motor protection device will not trip the motor during the starting period.
In cases which this is not achievable, a starting time up to 1. This longer time is permissible because of the reduction in the starting current towards the end of the acceleration period.
However, it is recommended that where the starting period exceeds the tE time, the motor manufacturer should be consulted so that the time required to reach the critical limiting temperature under the starting condition, can be established. What is the impact of low voltage on Ex-e motor starting? The low voltage will have the effect of reducing the motor torque during starting period torque is proportional to the square of the voltage and therefore will increase the starting time.
On the other hand, the starting current will be reduced in proportion to the voltage. Since the temperature rise in the motor and in any external motor protection device is proportional to time and the square of the current, the increased time and reduced current tend to compensate each other. Is there any limitation for successive start of Ex-e motors?
Storage, distribution or use on network prohibited A source of release may give rise to any one of these grades of release, or to a combination of more than one. For example, releases from seals which rely on wetting by the fluid which is being pumped are considered to be minor releases. NOTE 2 Failures such as the breakdown of pump seals, flange gaskets or spillages caused by accidents which involve urgent repair or shut-down are not considered to be part of normal operation nor are they considered to be catastrophic. NOTE 3 Normal operation includes start-up and shut-down conditions. For Australia and New Zealand this shall be taken to include Lower Flammable Limit or similar terms used by relevant codes and regulations.
AS-NZS 60079-14: Explosive atmospheres - Electrical installations design, selection and erection
Hazardous Area Classification & Design