Overall Electrical Explosion Protection

The overall electrical explosion protection of systems in explosive hazardous environment

Electrical equipments and circuits in explosive atmospheres have non explosion protection during electrical safety inspection,such as,the main engine is explosion protected,but accessories are not;ome equipments are explosion protected,but instruments are not;some equipments model number is incomplete,all these do not meet the requirements of overall explosion protection.Therefore,the explosion-proof electrical equipments that installed and used in explosive environments,not only related to manufacturing quality of explosion-proof electrical equipment,but also to the comprehensive safety requirements from engineering design,installation,inspection and maintenance and other aspects.

 

1.The picture below shows the cable wiring of Ex system

2.The picture below shows the steel pipe wiring of Ex system

Selection Of Ex-proof Electrical Equipment

Selection of Ex-proof electrical equipment in hazardous locations

Selection of electrical equipment in hazardous locations shall be based on the classification of hazardous areas,combustible materials and combustible dust classification,the ignition temperature of flammable substances and flammable dust clouds,and the minimum ignition temperature of combustible dust layer,etc.

 

1.Basic principles of the selection of explosion-proof electrical equipment

1.1 Security and reliability:types,class or groups of equipments shall adapt to explosive environments.

1.2 Economical principle :the selection of equipment do not have high requirements,for the same grade of products,the prices,lifetime,reliability,energy consumption and operating costs,availability of spare parts and other factors shall be considered.

1.3 Adaptability to environment:Consider the ambient temperature,humidity,atmospheric pressure;enclosure protection rating as well as corrosion resistance ability and so on.

1.4 Maintainability:Under the same conditions,choose products with simple structure,light weight;also consider the operational requirements of the system when necessary.

1.5 Only choose Ga protection products for Zone 0,for equipments or high voltage equipments that ignition sources often formed inside enclosure shall not be used in zone 1,Exd/Exp equipment shall be used in Zone 1 when necessary.

 

2.Relationship between hazardous area classification and equipment protection degree

Table 1 - Equipment protection levels (EPLs) Where only Zones are assigne

Zone Equipment protection levels (EPLs)
0 “Ga”
1 “Ga” or “Gb”
2 “Ga”,“Gb” or “Gc”
20 “Da”
21 “Da” or “Db”
22 “Da”,“Db” or “Dc”

3.Relationship between equipment protection level (EPL) and explosion-proof structure of device

Table 2 - Default relationship between types of protection and EPLs

EPL  Type of protection  Code According to
“Ga” Intrinsically safe “ia” IEC 60079-11
Encapsulation “ma” IEC 60079-18
Two independent types of protection each meeting EPL “Gb” IEC 60079-26
Protection of equipment and transmission systems using optical radiation “op is” IEC 60079-28
Special protection “sa” IEC 60079-33
“Gb” Flameproof enclosures “d” IEC 60079-1
Increased safety “e” IEC 60079-7
Intrinsically safe “ib”  IEC 60079-11
Encapsulation“m” “m”  IEC 60079-18
Oil immersion “o” IEC 60079-6

3.Relationship between equipment protection level (EPL) and explosion-proof structure of device

Table 2 - Default relationship between types of protection and EPLs

EPL  Type of protection  Code According to
“Gb” Pressurized enclosures “p”,“px”
“py”,“pxb”
or “pyb”
IEC 60079-2
“Gc” Powder filling “q” IEC 60079-5
Fieldbus intrinsically safe concept (FISCO)   IEC 60079-27
Protection of equipment and transmission systems using optical radiation “op is”
“op sh”
“op pr”
IEC 60079-28
Special protection “sb” IEC 60079-33
Intrinsically safe “ic”  IEC 60079-11
Encapsulation “mc” IEC 60079-18
Non-sparking “n” or “nA” IEC 60079-15
Restricted breathing “nR” IEC 60079-15
Energy limitation “nL” IEC 60079-15
Sparking equipment “nC” IEC 60079-15
Pressurized enclosures “pz”or“pzc” IEC 60079-2
Protection of equipment and transmission systems using optical radiation “op is”
“op sh”
“op pr”
IEC 60079-28
Special protection “sc” IEC 60079-33
“Da” Encapsulation “ma” IEC 60079-18
Protection by enclosure “ta” IEC 60079-31
Intrinsically safe “ia” IEC 60079-11 or
IEC 61241-11
Special protection “sa” IEC 60079-33
“Db” Encapsulation “mb” IEC 60079-18
Protection by enclosure “tc” or “tD” IEC 60079-31
IEC 61241-1
Pressurized enclosures “pD” IEC 61241-4
Intrinsically safe “ib” or “ibD” IEC 60079-11 or IEC 61241-11
Special protection “sb”  IEC 60079-33
“Dc” Encapsulation “mc” IEC 60079-18
Protection by enclosure “tc” or “tD” IEC 60079-31
IEC 61241-1
Pressurized enclosures “pD” IEC 61241-4
Intrinsically safe “ic” IEC 60079-11
Special protection “sc” IEC 60079-33

New protection marking codes with identification of EPLs may be introduced in the future

Quoted from IEC60079-14:2013 Table 2

 

4.Selection of the class and group of explosion-proof equipment

The class and group of explosion-proof equipment in explosive atmosphere shall not be lower than that of the explosive gas mixture.Relationship between the classification of gas/vapor or dust and equipment level shall be in accordance with Table Relationship between gas/vapor or dust subdivision and equipment group.When an explosive mixture of two or more flammable substances formed,explosion-proof equipment shall be choosen based on the mixed explosive mixture levels and groups,if there is no evidence or cannot be test,equipments shall be choosen according to high level and group.For explosion-proof equipments that indicating applicable particular gas or vapor environment,if not identified,the equipment can’t be used in other gas atmosphere.Relationship between gas or vapor ignition temperature and temperature class of equipment of class II equipment shall be in accordance with below table.Device structure shall ensure that the equipment Ex performance will not be degraded under operating conditions.Relationship between classification of gases/vapors,dust and selection of equipment types.

 

Table 3 - Relationship between gas/vapour or dust subdivision and equipment group

Location gas/vapour or dus  subdivision           Permitted equipment group
IIA II,IIA,IIB or IIC
IIB II,IIB or IIC
IIC II or IIC
IIIA IIIA,IIIB or IIIC
IIIB IIIB or IIIC
IIIC IIIC

Quoted from IEC60079-14:2013 Table 3

 

Table 4 - Relationship between gas and vapour ignition temperature and temperature class of equipment

Temperature class required by the
areaclassification
Ignition temperature
of gas or vapour in C
Allowable temperature
classes of equipment
T1 > 450 T1 -T6
T2 > 300 T2 -T6
T3 > 200 T3 -T6
T4 > 135 T4 -T6
T5 > 100 T5 -T6
T6 > 855 T6

Quoted from IEC60079-14:2013 Table 4

 

5.The special symbols or marks on the explosion-proof electrical equipment

The special symbols or mark on the explosion-proof electrical equipment shall be noted,if the explosion-proof certificate number with a suffix "U",it indicates that the device is with a component certificate,which can’t be used directly in the field,it must be used together with the main device after being certified as a whole;if with a suffix "X",it indicates that this equipment requires use under special conditions.

Installation Of Ex-proof Electrical Equipment

Installation of circuits and Ex-proof electrical equipment in explosive hazardous areas

1.Installation of electrical circuits in explosive gas atmospheres

Installation of electrical circuits in explosive gas atmospheres can be completed by cable wiring and conduit wiring.

1.1 General requirements for wiring installation

Electrical circuits shall be applied in areas where there’s a small risk of explosion or far from the source of release,avoiding being applied in places where is susceptible to mechanical damage,vibration,corrosion,dust accumulation and dangerous temperature.If inevitable,

precautions shall be taken.

Cable and conduit openings on the wall between hazardous and non-hazardous locations shall be fully sealed,for example,sealed with sand or mortar.

Cables for use in hazardous locations can’t have middle joint.When unavoidable,unless suitable for mechanical and electrical environmental condition,the connection shall use Ex junction box.

 

1.2 Cable wiring system

Cable system in Zone 0

Zone 0 is only allowed for the use of "ia" intrinsically safe cable system,and must be provide with additional surge current protection devices and lightning protection measures.

Cable system in Zone 1 and Zone 2 flexible cable in hazardous locations shall be:

  ※ Ordinary rubber sheathed flexible cable;

  ※ Ordinary polychloroprene sheathed flexible cable;

  ※ Thick rubber sheathed flexible cable;

  ※ The plastic sheathed flexible cable with same insulation as thick rubber sheathed cable;

  ※ Thick neoprene sheathed flexible cable.

Cables of fixed equipment shall be thermoplastic,thermosetting sheathed cables,synthetic rubber sheathed cables or mineral insulated metal sheathed cables.Flame retardant property of fixed wiring cables shall comply with requirements of IEC standards,unless the cable buried under the ground,powder filling conduit or prevented from flame spread by other measures.

Portable and mobile equipment shall be provided with cables of thick neoprene or other equivalent synthetic rubber sheathed cable;thick tough rubber sheathed cable or sheathed cable of the same rugged construction.The minimum cross-section of wire is 1.0mm2.

 

Isolation measures for cable going through different regions

the following measures shall be taken for cables going through the different regions:

a) cable trench of the connection joint of two regions shall be powder filled,or filled with fire retardant blocking materials or provided with fire partition;

b) places for cables going through adjacent regions that share same walls,floors,or places susceptible to mechanical damage,shall be protected;holes shall be tightly plugged;

c) For cables with protective tubes in the area of the interface (walls,floors,ground) both ends of protective tubes must be blocked by fire retardant blocking materials,filling depth not less than the pipe inner diameter,and not less than 40mm.

 

1.3 Wiring system of conduit

Conduit as following can be used for wiring in explosive dangerous places:

a) Wiring conduits shall be galvanized welded steel pipes for carrying low pressure fluid.

b) Conduit associated with flameproof enclosure,shall be selected according to the following:

1) Heavy gauge threaded steel pipes,seamless steel pipes;

2) Flexible metal conduit or composite structures,such as metal conduit with plastic or synthetic rubber sleeve.

Thread must be used for connection between conduits,between conduits and accessories,or between conduits and electrical equipments.Connection between conduit and electrical equipments shall be not use the back-off.Connection between the conduit and electrical equipment shall meet the requirements of the appropriate type of Ex protection.

Thread for steel pipe connecting must be processed smoothly,and without rust,the thread shall be coated composite resin or conductive rust-proof grease.Linen or insulating tape or paint is not allowed to be applied on the thread.

 

Isolation seals shall be used in conduit system under the following conditions:

a) When steel pipe going through adjacent partition wall of different hazardous areas,lateral isolation seals shall be installed on either side of the wall;

b) If the steel pipe being guided to other areas through floor or ground,vertical isolation seals shall be installed above the floor or ground;

c) In normal operation,within 450mm of enclosure with ignition source;

d) Places connecting conduits of diameter over 50mm and enclosure that contains connectors,or cable end;all threaded connections shall be tightened.

e) Pipelines where’s easy to have condensate accumulated,shall be installed with drainage isolation seals beneath its vertical section,the drain shall be placed underneath.

Isolation seals shall be filled by packing,after solidification,the packing shall be impermeable,no shrinkage,no cracks,such as sealants,sealing clay,epoxy resin,or sealed fiber.Isolation seals as one part of explosion-proof electrical equipment enclosure,the entire unit shall be subject to Ex certification and comply with the appropriate type of protection.Thickness of packing inside isolation seals shall be at least equal to the pipe diameter,at least not less than 16mm.

When the conduit contains multiple wires or cables,the total cross-sectional area of wires or cables shall be not more than 40% of the cross-sectional area of the conduit.

Wires must have no joint inside of seal bushing.

When wires through the walls,floor,or ground,the distance between the seals and walls,floor,or ground shall be not more than 300mm,and keep the holes plugged.

In the conduit system,explosion-proof flexible conduit with same Ex protection type shall be installed in the following places:

  ※ The motor inlet;

  ※ where the connection between electrical equipment and conduit is difficult;

  ※ Expansion joint or settlement joint where the conduit going through to the building.

To meet the protection requirements of enclosure,sealing measures (such as gaskets or thread sealant) shall be provided between the enclosure and conduit,as well as sealing measures (such as,sealing accessories) between the conduit and wire.

 

1.4 Grounding

Non-charged bare metal part of electrical equipment,such as metal enclosure,metal structures,metal wiring pipes and wiring accessories,cable protection pipes,cable metal sheath,etc,shall be grounded.

All electrical equipments in explosive hazardous areas except zone 2 light fittings shall be grounded by dedicated wires;multi-strand soft twisted wires are recommended,copper core cross-sectional area shall not be less than 4 mm2.Metal pipes,or metal enclosure of cables,etc.,can be used as an auxiliary ground wire.For neutral ungrounded system,the grounding resistance is not greater than 10Ω;for neutral grounding system,

grounding resistance is notgreater than 4Ω.

For light fittings in zone 2 explosive hazardous environment,metal piping systems with reliable electrical connection can be used as ground wires,but pipeline for flammable substances is not allowed.

Ground main lines shall be grounded with the grounding body at least two places in a different direction of explosion hazardous area.

For power in explosive dangerous areas,if TN power system is used,it shall be TN-S type in dangerous places (with separate neutral line N and protection line PE),that is,in dangerous places,the neutral line and the protection line shall not be linked or combined into one wire,for any part conversion from TN-C to TN-S type,protective wires shall be connected to equipotential bonding system in a non-hazardous location.

Note:leakage monitoring between neutral line and PE protection line in dangerous places shall be considered.

If TT -type power supply system used in Zone 1 (grounding of power ground and bare conductor separated),then the power will be protected by (residual) leakage current protection device.

Note:for places of high grounding resistance,this system is not allowed to be used.

If IT -type power system used (neutral line isolated with ground or reactance ground through impedance),an insulation monitoring device shall be provided to indicate 1st ground fault.

Note:The local equipotential connection which commonly referred to as an additional equipotential bonding is necessary.

When armored cables used in electrical equipments,grounding wire cores shall be connected to the internal grounding bolts,the steel strip or metal sheath shall be connected to the external grounding bolts.

During the design and operation of electrical installation,the impact caused by static electricity,lightning effects or electromagnetic radiation shall be considered.

 

2.Installation of Ex-proof electrical equipment in explosive gas atmospheres

2.1 Pre-installation inspection

Type,grade,group,environmental conditions and special signs of explosion-proof electrical equipment should meet the design requirements.Nameplate,Ex-mark,warning plate of explosion-proof electrical equipments should be correct and clear,enclosure and translucent parts should be without cracks or damage.

Fastening bolts of explosion-proof electrical equipment must have locking measures,without rusting.

After the internal wiring of explosion-proof electrical equipment terminal box is fastened,between the exposed live parts and metal enclosure,the clearances and creepage distances should meet the requirements of appropriate standards.

Excessive cable entry of electrical equipment must be plugged by plugging components of suitable protection.

Except the intrinsically safe equipment,plugging components can only be removed by special tools.

Cables and conduits connecting of electrical equipment shall meet the requirements of related protection.

There should be a metal washer between the sealing ring and the clamping elements,clamping elements shall meet the requirements of the product specification and shall ensure that the sealing ring press the cables or wires tightly.

Cable outer sheath diameter and sealing ring inner diameter should meet the requirements of the product specification;sealing ring must not be aging.

The products which explosion-proof certifications number has suffix of “U” is Ex components,they can’t be used separately unless get Ex certifications with other equipments.

Electrical equipments which explosion-proof certifications number has suffix of “X” shall be noted its special use condition.

 

2.2 Lamp installations shall comply with the following requirements:

a) Lamp type,model,and power shall comply with the requirements of the design and technical requirements;

b) Screw bulbs should be tightened,of good contact,not loose;

c) Lamp outer cover should be complete,bolts should be tightened.

 

2.3 Additional requirements of flameproof "d" enclosure

When installing equipment,ensure the distance between flameproof joint and solid obstacle is less than the value specified in the table below,unless smaller distance is proved acceptable by test.

 

Table 13 - Minimum distance of obstruction from the flameproof flange joints related to the gas group of the hazardous area

Gas classification Minimum distance (mm)
IIA 10
IIB 30
IIC 40

Quoted from IEC60079-14:2013 Table 13

 

Flameproof electrical equipment joint should have anti-corrosion measures.During installation please prevent any damage on flameproof surface.

Note:protection measures applicable to the joints:non-condensing grease or preservatives.

But on gas detector it should be used with caution,especially when choosing the material,non-coagulation should be ensured,otherwise it will affect the tightness between joints.

Fastening bolts of flameproof joint shall not be replaced at will,and spring washers should be complete.

The cable and conduit entry system shall meet the requirements of the relevant standards,and ensure the overall explosion -proof performance of flameproof enclosure.Cable entry system shall comply with the requirements of IEC60079-14 conduit engaged with flameproof enclosure at least five buckles.

If electrical equipment cables or cable entries required to be connected by steel pipe,a transition compression element should be used to clamp the sealing ring before connecting pipe;unions can be added if pipe connection is difficult to be achieved.

If the enclosure is designed for conduit connection,but changed to be connected by cables,a flameproof adapter with insulating sleeve and terminal box can be used,which will be connected to enclosure by conduit,conduit length not exceeding 150mm.Then connect the cable to the terminal box (such as flameproof or increased safety type),the terminal box must comply with the requirements of the appropriate type of protection.

 

2.4 Supplementary requirements for increased safety"e"Protection degree of enclosures with bare live parts shall not be less than IP54;and that of enclosures only containing insulated live parts shall be not less than IP44.

Cable gland shall be suitably applied to the cable,and keep the cable effectively connected with increased safety equipment.

Maintain the type of protection"e"and make the terminal box together with the sealing element reach the protection of IP54.

Internal wiring of terminal box should ensure its clearances and creepage distances,if the multi-conductor connected to a terminal,ensure that each is clamped tightly.

 

2.5 Additional requirements for intrinsic safety "i"

In the devices meet the requirements of EPL “Gb”,intrinsically safe electrical equipment and intrinsically safe part of associated equipments shall comply with IEC60079-11,at least"ib"type.

In the devices meet the requirements of EPL “Gc”,intrinsically safe electrical equipment and intrinsically safe part of associated equipments shall comply with IEC60079-11,at least"ic"type.

Insulation of intrinsically safe circuit cable should be able to withstand at least 500V AC test voltage of conductor to ground,conductor to shield and shield to ground.

It shall mark electrical parameters (CC and LC) or (CC and LC/RC) of all cables or accept the value of its most unfavorable conditions specified by the manufacturer.

Note:CC means cable distributed capacitance;

Note:LC means cable distributed inductance;

Note:LC means cable distributed resistance;

During installation of intrinsically safe circuits,ensure the intrinsically safe properties without interference from outside electromagnetic fields,such as the impact of top power lines or single-core cable high current.It can be achieved by shield,twisted pair cable or maintaining sufficient distance to electromagnetic fields.Cables no matter in hazardous areas or in non-hazardous areas,should meet the following requirements:

a) Cables of intrinsically safe and non-intrinsically safe circuits should be isolated;

b) Cables in intrinsically safe circuits arranged without mechanical damage;

c) Intrinsically safe or non-intrinsically safe circuits with armored cables,metal sheath or shield.

Cables with intrinsically safe circuit conductors should be clearly marked.

Wires banded to the same intrinsically safe circuit and non-intrinsically safe circuit should be isolated by an insulating layer or grounded metal.

Cables with intrinsically safe circuit conductors should be clearly marked.If the sheathing or surface is identified by color,the color should be light blue,and these cables should not be used for other purposes.If intrinsically safe or non-intrinsically safe circuit cables have armor,metal sheath or shield,the marking is not necessary.

Installation of intrinsically safe electrical equipment shall meet the requirements of IEC60079-14.

 

2.6 Special requirements for pressurized Ex equipment

1) Ventilation system must be made from non-combustible material,its structure should be strong,the connection should be close,and shall not remain dead angle with gas stranded;

2) Equipment shall be interlocked with ventilation system.It must ventilate first before operation,and when the ventilation rate is greater than 5 times on equipment and pipeline volume ventilation system,can connect to the main power supply of equipment;

3) In operation,the gas enter into equipment and ventilation system shall not contain flammable substances or other harmful substances;

4) In the operation of the equipment and ventilation system,for px or py type equipment,the wind pressure should not be lower than 50pa;for pz type equipment,the wind pressure should not be less than 25pa.When air pressure is lower than the above value,automatically disconnect the main power supply or signal of equipment;

5) The gas exhausted from ventilation process,should not be discharged into explosion hazardous environment;when taken effectively measures to prevent sparks and hot particles blown out from the device and its ventilation system,can be discharged into Zone 2 space;

6) For closed-circuit ventilation pressurized type equipment and its ventilation system,shall be supplied with clean gas;

7) The little gate or cover of equipment enclosure and ventilation system shall take interlocking device or add warning signs and other security measures;

8) Devices must have one or more of the inlet and exhaust port which is connected to the ventilation system.Exhaust port must be closed after ventilation.

In addition to overall inspection,all installation should be checked by professionals,they must meet the requirements of product documents and this specification.

 

6.1 Places for protective gas entering pipelines should be designed in non-hazardous areas,except canned protective gas.

 

6.2 Protective gas outlet should be located in non-hazardous areas,or follow the following table to install,which can prevent the existence of a small export in the danger area when flushing.

 

Table 17-Use of spark and particle barriers

EPL requirements of pipe
out let area
Gb
Equipment
A B
Gb Required Required
Gc Required Not Required
 A- devices under normal operating conditions generating ignitable sparks;
 B - devices under normal operating conditions not generating ignitable sparks.
 a: If a fault occurs in the pressurization,temperature of equipment may result in ignition hazards,protective devices installed in pressurized enclosure can prevent flammable gas quickly into pressurized enclosure.

Quoted from IEC60079-14:2013 Table 17


6.3 Pressure supply equipment,such as fan and compressor protective gas inlet,should be installed in non-hazardous areas.If the drive motor and/or control devices located in the gas pipeline or unavoidable installed in hazardous areas,these devices

should be protected by appropriate explosion-proof measures.

 

6.4 For installation of equipment without internal source of release,in the event of failure of protective gas,the installation shall meet the requirements of specified method.And for equipment with internal source of release,in accordance with manufacturer's instructions,in case of a failure of protective gas,there should be alarms,take corrective measures to ensure the security of the system.

 

Table 18-Summary of protection requirements for enclosures without an internal source of release

EPL requirements Equipments without pressurization installed
Inside of enclosure are not suitable for EPL
Gc.
Equipments without pressurization installed
Inside of enclosure are suitable for EPL Gc.
Gb Alarm and power cut off Alarm
Gc Alarm Measures are unnecessary
Note 1: If alarm starts,immediately take measures to restore the supply of entire system;
Note 2: If automatic power-off may cause a greater risk,take other measures,such as doubling the supply of protective gas.

Quoted from IEC60079-14:2013 Table 186.5 For equipment with internal source of release,in accordance with manufacturer's instructions,in case of a failure of protective gas,there should be alarms;take corrective measures to ensure the security of the system.

 

6.6 Multiple pressurized enclosures sharing safety equipment should meet the requirements of IEC60079-2.

 

6.7 Flush 

For the shortest flush time of the pressurized enclosure specified by the manufacturer,the pipeline smallest additional flushing time in unit volume should be added to multiply the time for pipeline receiving.

In Zone 2 areas,if the enclosure and its pipeline internal environment is far below the lower explosive limit (e.g.25% LEL),flush can be omitted. In addition,gas detector can be used to check whether the gas in pressurized enclosure can be ignited.

Gas for flushing,continuous dilution or pressurization should be non-flammable,non-toxic,and does not contain moisture,oil,dust,fibers,chemicals,fuel,or other impurities,because these factors may cause danger or adversely affect the integrity of the equipment and operation. Usually air is used,sometimes inert gas.Oxygen content of protective gas should not be higher than the oxygen in the air.

If using air as a protective gas,air supply should be in non-hazardous area,and located at where the risk of air mixed can be reduced,the impact of nearby buildings due to the wind direction,wind speed changes may also be considered.

Temperature at the protective gas inlet should not exceed 40 (in special cases,higher or lower temperature gas can be used,but it must be indicated on the pressurized enclosure).

The invasion of flammable gas or vapor through spreading into wiring system or protective gas leakage through the wiring system must be avoided,wiring system should be sealed.

 

7 Supplementary requirements for equipments used in Zone 2

7.1 If exposed live parts or only insulated live parts within the enclosure,the minimum protection shall be IP54 and IP44 respectively.

 

7.2 If the application spaces can provide sufficient protection to prevent foreign matters entering,for enclosure with exposed live parts and the enclosure is only with insulated live parts,protection shall be IP4X and IP2X respectively.

 

7.3 If entering of hard objects or water does not affect the safety of the device,the above requirements may be unnecessary (such as deformeter,heat resistance thermometer,thermocouple,energy-limited equipment).

 

7.4 For energy-limited equipment and equipment in circuits,the maximum internal capacitance sum with the capacitance of the cable should not exceed the maximum allowable capacitance (two adjacent cable core equivalent as a centralized capacitance),the maximum internal inductance sum with the inductance of the cable should not exceed the maximum allowable inductance (two maximum isolator cable core equivalent as a centralized inductance).These figures shall be marked on the equipments of protection type“n”or files.

 

7.5 Cable and conduit wiring system should be installed based on standard and meet the following supplementary requirements for cable glands and terminals:

a) Connection of cable should be finished by suitable cable gland.

b) In order to ensure the protection degree of wiring cavity,only cable glands with suitable sealing elements (such as gaskets or thread sealant) between cable and cable gland can be used.

Note: When engagement between threaded cable gland and enclosure is 6mm thick or above,sealing measures may not be applied,

but the central axis of the cable gland should perpendicular to the enclosure surface.

c) Seal of breathing-restricted enclosure should ensure the breathing-restricted performance of enclosure.

d) Unused cable entries should be plugged to ensure the protection of enclosure.

 

7.6 Conductor terminals

Some terminals,such as groove terminals,allow entry of several wires.If multiple wires simultaneously connected to a terminal,make sure each wire is reliable clamped.Unless specified by the manufacturer,conductors of different sections can‘t be connected to the same terminal,except for single clamped first.

On the terminal board,if there is short circuit danger between adjacent terminals,insulation of each conductor should be coherent to the metal of terminal.

Note:If single nut saddle clamp is used to fix a wire,the wire around the screw should be a "U” shape,unless not permitted by the

manufacturers.

Inspection And Oaintenance Of Ex-proof Electrical Equipment

Inspection and maintenance of explosion-proof electrical equipment in hazardous area

1.Requirements of inspection for explosion-proof equipment

1.1 General

Initial inspection shall be made to minimize the ignition risk of the electrical equipment used in hazardous areas before devices and equipment are put into service and/or during the acceptance checking of the project handover after final installation.And the electrical equipment shall be continuously monitored and regularly checked in order to ensure that it is in good condition and may be continuously used in hazardous areas.

NOTEThe complete initial inspection is not required if some items were checked by manufacturer equally and the components checked are not possible to be affected by the installation,e.g.initial detailed inspection for the clearance of flameproof in explosion-proof motors is not required,however,initial inspection of terminal boxes dismantled to facilitate field wiring connections shall be carried out after installation.

 

1.2 Qualifications of personnel

Persons involved in the electrical inspection and maintenance in hazardous areas shall possess the following:

a) Understanding of the general principles of explosion protection;

b) Understanding of the general principles of types of protection and marking;

c) Understanding of those aspects of equipment design which affect the protection concept;

d) Understanding of content of certificates and relevant provision;

e) General understanding of inspection and maintenance requirements of IEC 60079-17;

f ) Familiarity with the particular techniques to be employed in the selection and erection of relevant equipment;

g) Understanding of the additional importance of permitting to work systems and safe isolation in relation to explosion protection.

The inspection and maintenance of explosion-protected equipment shall be carried out only by persons whose training has included instruction on the various types of protection and installation practices,relevant rules and regulations and on the general principles of area classification.

Appropriate continuing education or training shall be undertaken by personnel on a regular basis and certificates of relevant experience and training shall be obtained.

 

1.3 Continuous monitoring and regular inspection

1.3.1 Continuous monitoring

Continuous monitoring shall be carried out by professional personnel as required and be record.

Care shall be taken off if there is any unusual phenomenon found.Continuous monitoring shall include the following items.

1) Explosion-proof electrical equipment shall be operated under prescribed conditions specified by the equipment manufacturer.

For the product with certificate numbers which have the suffix “X” shall comply with specific conditions required by the relevant documentation for safely using.

 

2) The enclosure and surrounding environment of the explosion-proof electrical equipment should be kept clean,sundries and flammable items that obstruct the safe operation of the equipment shall be cleared away,and personnel shall to be specified to test and analyze the concentration of surrounding explosive compound around equipment frequently.

 

3) There should be good condition for ventilation and heat dissipation when the equipment is working,and inspection shall be taken to ensure that the surface temperature and temperature rise of enclosure is not exceeded to the product requirements.

 

4) Check the running equipment that shall not be suffer the external damage,and there shall be no incline,friction between components or abnormal sound.The vibration value shall not exceed the specified.

 

5) The completion and tightness of fixed bolts and spring washers on enclosure shall be checked and shall be secured against loosening.

 

6) Enclosure shall be checked that there are no cracks or mechanical deformation which may undermine explosion-proof performance.Cable entry devices shall be sealed reliably.Unused cable entries shall be sealed with a flameproof blanking element appropriate to the protection type.

 

7) Various device of protection,blocking,detection,alarm and grounding shall not be arbitrarily removed and the integrity,sensitivity and reliability shall be maintained.

 

8) Whether the explosion-proof lighting fittings maintain its structure and integrity of protective cover,and whether the surface temperature of lighting fittings does not exceed the predetermined value of products shall be checked. Whether power source and the lamp model are consistent with the lighting markings,and whether lighting installation position is in line with the provisions described shall also be checked.

 

9) The operator could shut down the electrical equipment and take emergency measures and then notify the professional to take inspection and treatment if the following occurs:

a) The load current exceeds the predetermined value suddenly or phase running state is confirmed;

b) The temperature of motors or switches rises up highly or emit smoke;

c) Motors or other equipment produce noise or sparks due to the friction caused by loosening of components;

d) The mechanical load has severe fault or may endanger the electrical safety.

 

10) To minimize the risk of ignition caused by electrical equipment used in dust hazardous areas,whether the original design conditions have changed shall be checked (dust type,maximum thickness of the dust layer,etc.).

 

11) Mobile electrical equipments (hand-held,portable or moveable equipment),are particularly prone to be damaged or misused,the time between two inspections could be shortened according to actual needs.Mobile electrical equipment shall be taken general inspection every 12 months at least.For the enclosure needs to be often opened (such as a battery cover) detailed inspection shall be taken.Moreover,visual inspection shall be taken before using this kind of equipment to ensure the device is not obviously damaged.

 

1.3.2 Periodic inspection

Further detailed inspection could be necessary after Periodic inspection of visual check or general check may need.

For the determination about degree of inspection and the gap time between two inspections,situations about equipment type,manufacturer's instructions,factors affect the damage degree,the operation location and the results of the previous inspection.

These experiences shall be utilized to ensure the degree of inspection and the gap time between two inspections about this kind of equipment.

NOTE:The main factors causing deterioration of equipment,includingbeing susceptible to corrosion and exposed to chemicals or solvents,possibility of accumulation of dust or dirt,possibility of water ingress,being exposed to high ambient temperature,the risk of mechanical damage,subjecting to intense vibration,training and experience of personnel,unauthorized modifications or adjustments,inadequate maintenance,such as maintenance which is not followed the manufacturer's recommendations.

Periodic inspection should be entrusted to the safety testing and inspection organization with professional qualifications of explosion-proof equipment,and generally,the time interval shall not be more than three years.Enterprises shall take timely corrective action based on test result,and the inspection reports and rectification shall be recorded in production safety supervision and management departments.

All the results of initial,regular and continuous monitoring shall be recorded.

 

2.The maintenance requirements of explosion-proof electrical equipment

2.1 Remedial measures and equipment replacement

All equipment shall be required to indicate that the general conditions,appropriate remedial measures shall be taken if necessary.It should pay attention to maintaining the integrity of the type of protection,which could require consulting with the manufacturer.Replacement parts should be carried out in accordance with the requirements of the relevant security documents.

The parts which will,if replaced,adversely affect the safety performance of the equipment specified in security documents shall not be done so unless permitted by the relevant departments.

NOTE1:It should be taken to avoid conflict with the measures that manufacturers taken to reduce static electricity affection.

NOTE2:When replacing the bulb of lighting fittings,the of power and models of lamp source shall comply with the provisions of fitting markings, or it may cause overheating.

NOTE3:Overheating may be caused by the corrosion,being painted or covered of transparent cover or incorrect installation of light fittings.

 

2.2 Maintenance of flexible cable

Flexible cables,flexible connecting pipe and terminal segment connected could be easily damaged,so it shall be checked by a predetermined time interval and be replaced if damaged or missing.

 

2.3 Shutdown

If electrical equipment and other equipment must be shut down during maintenance,the bare wire shall meet one of the following conditions:

a) Correctly connected to the appropriate enclosure;

b) Disconnected with all the power supply and insulated;

c) Disconnected with all the power supply and being ground.

If electrical equipment is shut down and will not be operated permanently,all power supply conductors associated shall be disconnected,dismantled or correctly connected to the appropriate enclosure.

 

2.4 Fasteners and tools

Special screws,fasteners or special tools shall be prepared and be utilized where necessary.

 

2.5 Environmental conditions

Electrical equipment used in hazardous areas may be affected by the adverse effects of environmental conditions,major factors such as corrosion,ambient temperature,ultraviolet radiation,water entering,accumulation of dust or sand,mechanical and chemical action shall be considered with.

The type of equipment protection and protection degree could be affected by the effect of metal corrosion or chemical substances (especially solvent) to plastic or elastic components.It shall be replaced if the enclosure or components is corroded seriously.Plastic enclosure may appear the overall surface cracks.The metal enclosure of device,when necessary,shall be protected appropriately by use of appropriate protective coating as anti-corrosion treatment.The frequency and methods of such treatment shall be according to the environmental conditions.

It shall be verified whether the electrical equipment designed can withstand the maximum and minimum ambient temperatures likely to be encountered.

NOTE: If the marking of the electrical equipment does not include an ambient temperature range,the equipment is designed to be used within the temperature range -20°C to 40°C.If the marking of the electrical equipment includes an ambient temperature range,the equipment is designed to be used within this range.

All components of the device should be kept clean,and there shall not be accumulation of dust and similar hazardous substances which could cause the temperature rise.

Measures shall be taken to ensure to maintain the performance of weather-proof of electrical equipment. Damaged gasket shall be replaced.

Anti-condensation device,such as breathing and draining devices or heating unit shalbe checked to ensure the correct operation.

Tightness of bolts and cable entries of equipment shall be paid specially attention to if subjected to vibration.

Measures shall be taken to avoid producing static electricity when cleaning non-metallic enclosures for electrical equipment.

 

2.6 Isolation of equipment maintenance

Electrical equipment shall be isolated to all power supply including neutral line before being opened in hazardous area,and effective measure shall be taken to avoid the inadvertently re-energized when opened.

 

2.6.1 Devices other than intrinsically safe circuits

a) For the electrical equipment with intrinsically safe circuits built-in installed in hazardous locations,before it is isolated with all input connection or isolated with the output connection including neutral conductors when there is existence for zero line to ground,the cover shall not be opened,except for item b or c on specification.Here being isolated means to pull out fuse link,or disconnect isolator and switch. The enclosure could only be opened until enough time passes by and the surface temperature or stored electrical energy cannot cause ignition.

b) Within the time required for planning work,if the responsible department or personnel could ensure that there will not be explosive

environment and make the written approval,the main operation of exposed live parts could be taken after taking general security

measures.

c) If permitted by the relevant laws and regulations,the requirements on item a and b could be loosened but only in Zone 2.

Operation could be taken after taking general security measures if it meets the following conditions and is certificated by security assessment:

1) The planning operation on the live part could not produce combustible spark;

2) The circuit has the structure to prevent sparking;

3) There is no hot surface on electrical equipment and associated circuits used in the hazardous area which may cause ignition. The planning operation could be taken after taking general security measures if it is complied with these conditions.

Results of the safety assessment shall be recorded in the file,which contains the following information:

  ※ The form of the planning operation on live equipment;

  ※ Assessment results,including the test results made in the assessment;

  ※ Any related conditions for maintenance of live equipment required about the assessment.

Evaluator personnel of equipment shall:

  ※ Being familiar with all relevant standards,the requirements of regulations being implemented and the existing explanatory material;

  ※ Could obtain a variety of materials required for the evaluation;

  ※ When necessary,could use the test equipment and make test procedures similar to national inspection department.

 

2.6.2 Intrinsically safe devices

Maintenance on live equipment could be taken if it meets the following conditions:

a) Maintenance work in hazardous areas

Any maintenance work shall be limited to the following condition:

1) When disconnect,remove or replace some electrical equipment components and cables;

2) When adjust the control device required for electrical equipment or systems calibration;

3) When remove and replace the plug-in unit or components;

4) Using inspection equipment required in the documents,when inspection equipment is not specified in the document,only using instruments that will not affect the safe performance of the circuit;

5) Other maintenance activities specifically allowed by relevant documents.

After the completion of these tasks,personnel to perform these functions should ensure that the intrinsic safety system or supporting intrinsically safe electrical equipment complies with the requirements of relevant documents.

b) Maintenance in non- hazardous areas

For maintenance of non-hazardous area associated electrical equipment and partial intrinsically safe circuit,when these electrical equipment or circuits are still partly connected to intrinsically safe circuit in hazardous areas,they should be limited to the content in term a).

Before disconnecting circuit in hazardous areas,grounding connection of barriers should not be dismantled to facilitate test of grounding resistance,except when double grounding device installed,single ground can be removed.

Only after the electrical equipment or circuit is disconnected from circuit in hazardous places,maintenance work can be done for associated equipment or parts in intrinsically safe circuit in non- hazardous areas.

 

2.7 Maintenance requirements of combustible dust explosion-proof electrical equipment

For electrical equipments which must be opened for maintenance should be located in dust free places.

Otherwise,appropriate measures need to be taken to prevent dust from entering the enclosure.

When removing the seals,joints,etc,if not replacing them,they must not be damaged.

When reassembling,you should provide and comply with the manufacturer's recommendations of seal.

Electrical apparatus in combustible dust environments shall be inspected and maintained according to schedule.Inspection and maintenance intervals depend on the environmental conditions,device quantities and the manufacturer's recommendations.

 

2.8 Grounding and equipotential bonding connection

Grounding and equipotential connection in hazardous area need to be made sure in good condition.

 

3 Ex electric apparatus check list(the following tables and contents only for reference)

Check for Ex “d” Grade of inspection
Detailed  Normal  Visual
A EQUIPMENT      
1 Equipment is appropriate to the EPL/zone requirements of the location X X X
2 Equipment group is correct X X  
3 Equipment temperature class is correct X X  
4 Equipment circuit identification is correct X    
5 Equipment circuit identification is available X X X
6 Enclosure,glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory X X X
7 There is no unauthorized modifications X    
8 There is no evidence of unauthorized modification   X X
9 Bolts,cable entry devices (direct and indirect) and blanking elements are of the correct type and are complete and tight      
- physical check
- visual check
X X  
    X
10 Flange surfaces are clean and undamaged and gaskets are satisfactory      
11 Dimensions of flanged joint gaps are within maximum values permitted X X  
12 Lamp rating,type,and position are correct X    
13 Motor fans have sufficient clearance to the enclosure and/or covers X    
14 Breathing and draining devices are satisfactory X X  
 
B INSTALLATION      
1 Type of cable is appropriate X    
2 There is no obvious damage to cables X X X
3 Sealing of trunking,ducts,pipes and/or conduits is satisfactory X X X
4 Stopping boxes and cable boxes are correctly filled X    
5 Integrity of conduit system and interface with mixed system maintained X    
6 Earthing connections,including any supplementary earthing bonding connections are satisfactory (for example connections are tight and conductors are of sufficient cross-section)      
- physical check X    
- visual check   X X
7 Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory X    
8 Insulation resistance is satisfactory X    
9 Automatic electrical protective devices operate within permitted limits X    
10 Automatic electrical protective devices are set correctly (auto-reset not possible) X    
11 Specific conditions of use (if applicable) are complied with X    
12 Cables not in use are correctly terminated X    
13 Obstructions adjacent to flameproof flanged joints are in accordance with the appropriate requirements X X X
14 Variable voltage/frequency installation complies with documentation X X  
 
C ENVIRONMENT      
1 Equipment is adequately protected against corrosion,weather,vibration and other adverse factors X X X
2 No undue accumulation of dust and dirt X X X
3 Electrical insulation is clean and dry      

3.2 Inspection schedule for Ex “e”

Check for Ex “e” Grade of inspection
Detailed  Normal  Visual
A EQUIPMENT      
1 Equipment is appropriate to the EPL/zone requirements of the location X X X
2 Equipment group is correct X X  
3 Equipment temperature class is correct X X  
4 Equipment circuit identification is correct X    
5 Equipment circuit identification is available X X X
6 Enclosure,glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory X X X
7 There is no unauthorized modifications X    
8 There is no evidence of unauthorized modification   X X
9 Bolts,cable entry devices (direct and indirect) and blanking elements are of the correct type and are complete and tight      
- physical check X X  
- visual check     X
10 Lamp rating,type,and position are correct X    
11 Electrical connections are tight X    
12 Condition of enclosure gaskets is satisfactory X    
13 Motor fans have sufficient clearance to the enclosure and/or covers X    
14 Breathing and draining devices are satisfactory X X  
 
B INSTALLATION      
1 Type of cable is appropriate X    
2 There is no obvious damage to cables X X X
3 Sealing of trunking,ducts,pipes and/or conduits is satisfactory X X X
4 Stopping boxes and cable boxes are correctly filled      
5 Integrity of conduit system and interface with mixed system maintained X    
6 Earthing connections,including any supplementary earthing bonding connections are satisfactory (for example connections are tight and conductors are of sufficient cross-section)      
- physical check X    
- visual check   X X
7 Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory X    
8 Insulation resistance is satisfactory X    
9 Automatic electrical protective devices operate within permitted limits X    
10 Automatic electrical protective devices are set correctly (auto-reset not possible) X    
11 Specific conditions of use (if applicable) are complied with X    
12 Cables not in use are correctly terminated X    
13 Obstructions adjacent to flameproof flanged joints are in accordance with the appropriate requirements      
14 Variable voltage/frequency installation complies with documentation X X  
 
C ENVIRONMENT      
1 Equipment is adequately protected against corrosion,weather,vibration and other adverse factors X X X
2 No undue accumulation of dust and dirt X X X
3 Electrical insulation is clean and dry X    

3.3 Inspection schedule for Ex “n”

Check for Ex “n” Grade of inspection
Detailed  Normal  Visual
A EQUIPMENT      
1 Equipment is appropriate to the EPL/zone requirements of the location X X X
2 Equipment group is correct X X  
3 Equipment temperature class is correct X X  
4 Equipment circuit identification is correct X    
5 Equipment circuit identification is available X X X
6 Enclosure,glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory X X X
7 There is no unauthorized modifications X    
8 There is no evidence of unauthorized modification   X X
9 Bolts,cable entry devices (direct and indirect) and blanking elements are of the correct type and are complete and tight      
- physical check X X  
- visual check     X
10 Lamp rating,type,and position are correct X    
11 Electrical connections are tight X    
12 Condition of enclosure gaskets is satisfactory X    
13 Enclosed-break and hermetically sealed devices are undamaged X X X
14 Restricted breathing enclosure is satisfactory X    
15 Motor fans have sufficient clearance to the enclosure and/or covers X    
16 Breathing and draining devices are satisfactory X X  
 
B INSTALLATION      
1 Type of cable is appropriate X    
2 There is no obvious damage to cables X X X
3 Sealing of trunking,ducts,pipes and/or conduits is satisfactory X X X
4 Stopping boxes and cable boxes are correctly filled      
5 Integrity of conduit system and interface with mixed system maintained X    
6 Earthing connections,including any supplementary earthing bonding connections are satisfactory (for example connections are tight and conductors are of sufficient cross-section)      
- physical check X    
- visual check   X X
7 Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory X    
8 Insulation resistance is satisfactory X    
9 Automatic electrical protective devices operate within permitted limits X    
10 Automatic electrical protective devices are set correctly (auto-reset not possible) X    
11 Specific conditions of use (if applicable) are complied with X    
12 Cables not in use are correctly terminated X    
13 Obstructions adjacent to flameproof flanged joints are in accordance with the appropriate requirements      
14 Variable voltage/frequency installation complies with documentation X X  
 
C ENVIRONMENT      
1 Equipment is adequately protected against corrosion,weather,vibration and other adverse factors X X X
2 No undue accumulation of dust and dirt X X X
3 Electrical insulation is clean and dry X    

3.4 Inspection schedule for Ex“i”

Check for Ex “I” Grade of inspection
Detailed  Normal  Visual
A EQUIPMENT      
1 Circuit and/or equipment documentation is appropriate to the EPL/zone X X X
2 Equipment installed is that specified in the documentation-(only for
permanent installation)
X X  
3 Circuit and/or equipment category and group correct X X  
4 Equipment temperature class is correct X X  
5 Installation is clearly labeled X X  
6 Enclosure,glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory X    
7 There is no unauthorized modifications X    
8 There is no evidence of unauthorized modification   X X
9 Diode safety barriers,relays and other energy limiting devices are of the approved type,installed in accordance with the certification requirements and securely earthed where required X X X
10 Electrical connections are tight x    
11 Printed circuit boards are clean and undamaged x    
 
B INSTALLATION      
1 Cables are installed in accordance with the documentation X    
2 Cable screens are earthed in accordance with the documentation X    
3 There is no obvious damage to cables X X X
4 Sealing of trunking,ducts,pipes and/or conduits is satisfactory X X X
5 Point-to-point connections are all correct X    
6 Earth continuity is satisfactory (e.g.connections are tight,conductors
are of sufficient cross-section)
X    
7 Earth connections maintain the integrity of the type of protection X X X
8 Intrinsically safe circuit is insulated against ground or grounded at one point (refer to document) X    
9 Separation is maintained between intrinsically safe and non-intrinsically safe circuits in common distribution boxes or relay cubicles X    
10 Short-circuit protection of the power supply (if applicable) is in accordance with the documentation X    
11 Specific conditions of use (if applicable) are complied with X    
12 Cables not in use are correctly terminated X    
 
C ENVIRONMENT      
1 Equipment is adequately protected against corrosion,weather,vibration and other adverse factors X X X
2 No undue accumulation of dust and dirt X X X

3.5 Inspection schedule for Ex“p”

Check for Ex “p” Grade of inspection
Detailed  Normal  Visual
A EQUIPMENT      
1 Equipment is appropriate to the EPL/zone requirements of the location X X X
2 Equipment group is correct X X X
3 Equipment temperature class or surface temperature is correct X X  
4 Equipment circuit identification is correct X    
5 Equipment circuit identification is available X    
6 Enclosure,glasses and glass-to-metal sealing gaskets and/or compounds are satisfactory X X X
7 There is no unauthorized modifications X    
8 There is no evidence of unauthorized modification   X X
9 Lamp rating,type,and position are correct X    
 
B INSTALLATION      
1 Type of cable is appropriate X    
2 Type of cable is appropriate X    
3 Earthing connections,including any supplementary earthing bonding connections,are satisfactory,for example connections are tight and conductors are of sufficient cross-section      
- physical check X    
- visual check   X X
4 Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory X    
5 Automatic electrical protective devices operate within permitted limits X X X
6 Automatic electrical protective devices are set correctly X    
7 Protective inert gas inlet temperature is below maximum specified X    
8 Ducts,pipes and enclosures are in good condition X X X
9 Protective gas is substantially free from contaminants X X X
10 Protective gas pressure and/or flow is adequate X X X
11 Pressure and/or flow indicators,alarms and interlocks function correctly X    
12 Conditions of spark and particle barriers of ducts for exhausting thegas in hazardous area are satisfactory X    
13 Specific conditions of use (if applicable) are complied with X    
 
C ENVIRONMENT      
1 Equipment is adequately protected against corrosion,weather,vibration and other adverse factors X X X
2 No undue accumulation of dust and dirt X X X

3.6 Inspection schedule for Ex“tD” (dust-ignition-proof)

Check for Ex “tD” Grade of inspection
Detailed  Normal  Visual
A EQUIPMENT      
1 Equipment is appropriate to the EPL/zone requirements of the location X X X
2 Degree of protection (IP grade) of equipment is appropriate for the dust conditions X X X
3 Equipment maximum surface temperature is correct X X  
4 Equipment circuit identification is available X X X
5 Equipment circuit identification is correct X    
6 Enclosure,glass parts and glass-to-metal sealing gaskets and/or compounds are satisfactory X X X
7 There is no unauthorized modifications X    
8 There is no evidence of unauthorized modification   X X
9 Bolts,cable entry devices (direct and indirect) and blanking elements are of the correct type and are complete and tight      
- physical check X X  
- visual check     X
10 Lamp rating,type,and position are correct X    
11 Electrical connections are tight X    
12 Condition of enclosure gaskets is satisfactory X    
13 Motor fans have sufficient clearance to the enclosure and/or covers X    
 
B INSTALLATION      
1 Installation to minimize the risk of accumulation of dust X X X
2 Type of cable is appropriate X    
3 There is no obvious damage to cables X X X
4 Sealing of trunking,ducts,pipes and/or conduits is satisfactory X X X
5 Earthing connections,including any supplementary earthing bonding connections are satisfactory (for example connections are tight and conductors are of sufficient cross-section)      
- physical check X    
- visual check   X X
6 Fault loop impedance (TN systems) or earthing resistance (IT systems) is satisfactory X    
7 Insulation resistance is satisfactory X    
8 Automatic electrical protective devices operate within permitted limits X    
9 Specific conditions of use (if applicable) are complied with X    
10 Cables not in use are correctly terminated X X  
 
C ENVIRONMENT      
1 Equipment is adequately protected against corrosion,weather,vibration and other adverse factors X X X
2 No undue accumulation of dust and dirt X X X

Warom Technology Incorporated Company

Address:No.555,Baoqian Road,Jiading District,Shanghai,China.

Zip Code:201808

Fax:+86 21 3997 7077