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COMPEX > UNIT 3: Flameproof Ex d > Flashcards

UNIT 3: Flameproof Ex d Flashcards

1
Q

1.
Cable glands entering flameproof enclosures are required to achieve a minimum number of threads engagement. The minimum requirement is?

Eight full threads
Ten full threads
Three full threads
Five full threads.

A

Five full threads.

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2
Q

2.
Which one of the following may be applied in the gap of a flameproof flanged joint to improve the IP rating?

Thermosetting sealant

Non setting grease

Non-hardening grease bearing textile tape

Any oil based paint

A

Non setting grease

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3
Q

3.
Pressure piling in a flameproof enclosure is caused by?

Over-current protection set too high

Exceeding the equipment rated voltage

Excessive tightening of cover bolts;

Alteration of the internal component layout.

A

Alteration of the internal component layout

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4
Q

4.
Maximum gaps and minimum widths are specified for the joints of flameproof enclosures in order to?

To cool the hot gases produced by an internal explosion

To improve the mechanical strength of the enclosure

To allow a gasket to be fitted

To relieve the pressure of an internal explosion

A

To cool the hot gases produced by an internal explosion.

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5
Q

5.
When an enclosure is termed ‘flameproof it indicates that?

An explosion will not dislodge it from its fixings

It will not burn

It will operate continuously in a fire

Gas around the enclosure will not be ignited by an internal explosion.

A

Gas around the enclosure will not be ignited by an internal explosion.

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6
Q 
6.
A function (live) test on a flameproof enclosure after some internal adjustments requires which one of the following as a minimum requirement?

Fit only the corner bolts and apply a ‘Danger Live’ notice

All bolts to be replaced - spanner tight - and flamepath gaps checked

Only one bolt fitted to support the cover and a ‘Danger Live’ notice

Leave cover off, apply a ‘Danger Live’ notice and make sure inadvertent
contact with live parts is avoided

A

All bolts to be replaced - spanner tight - and flamepath gaps checked.

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7
Q

7.
One of the design features of flameproof enclosures is?

Electric field strength

A gas detector and alarm arrangement

Flanged and/or spigot joints

An IP67 ingress protection level.

A

Flanged and/or spigot joints

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8
Q

8.
Obstruction of the flamepath openings of the flanged joints of Ex d enclosures by solid obstructions requires minimum clearances depending on the equipment group. For a IIC enclosure this not less than?

30mm
40mm
10mm
50mm

A

40mm

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9
Q

9.
The minimum requirement for tightening the cover bolts of a flameproof enclosure
to ensure its safe operation is?

All cover bolts fitted but only alternate bolts need be spanner tight

Some bolts missing (up to 20%) and the rest spanner tight

All cover bolts fitted and spanner tight

All cover bolts fitted and tightened by torque wrench in excess of 60kgfm.

A

All cover bolts fitted and spanner tight

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10
Q

10.
Fitting new (metric thread) cable glands to older flameproof equipment, with
imperial thread forms at cable gland entries, may be achieved by?

Re-tapping the entries using a metric tap the same size as the gland

Using an Exd adaptor with appropriate thread forms

Fitting threaded inserts after drilling

Fitting the metric gland as far as possible with the aim of achieving five-full threads engagement.

A

Using an Exd adaptor with appropriate thread forms

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11
Q

11.
Cable glands for entry to flameproof enclosures are required to have a minimum number of threads engaged and thread depth, the purpose being to?

Prevent flammable gases entering the enclosure

Preserve the strength of the enclosure.

Preserve the enclosure IP Rating.

Prevent the effects of an internal ignition transmitting to and igniting an
external flammable gas.

A

Prevent the effects of an internal ignition transmitting to and igniting an external flammable gas.

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12
Q

12.
Pressure piling in a flameproof enclosure may be described as?

Metal fatigue due to excessive stresses

Operation of a vent due to gas pressure

Piles for supporting heavy equipment

Ignition in one section of an enclosure causing a stronger secondary
explosion in another connected section.

A

Ignition in one section of an enclosure causing a stronger secondary
explosion in another connected section.

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13
Q

13.
Newly installed Ex d equipment may be installed in which one of the following?

Areas needing EPL Gc ( Cat 3G ) equipment

Areas needing EPL Ga ( Cat 1 G ) equipment

Only areas needing EPL Gb ( Cat 2G ) equipment.

Areas needing EPL Gb and Gc ( Cats 2G and 3G ) equipment

A

Areas needing EPL Gb and Gc ( Cats 2G and 3G ) equipment

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14
Q

14.
A flameproof enclosure is marked gas group IIB With consideration of the EPL
(Category), in which areas may it be installed?

(Areas requiring either EPL’s Gb or Gc (Cats 2 or 3) gas group IIB only

Any hazardous area;

Areas requiring either EPL’s Gb or Gc (Cats 2 or 3) gas group IIA or IIB

Areas requiring either EPL’s Gb or Gc (Cats 2 or 3) gas group IIB or IIC

A

Areas requiring either EPL’s Gb or Ge (Cats 2 or 3) gas group IIA or IIB

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15
Q

15.
Flameproof Ex d equipment may be used in which one of the following areas?

Ga (Cat 1 G) areas only

Gc (Cat 3G) areas only

Gb or Gc (Cat 2G or 3G) areas

Ga, Gb or Gc (Cat 1 G, 2G or 3G) areas

A

Gb or Gc (Cat 2G or 3G) areas

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16
Q

Ex d enclosures

Denso tape.

Can you use Denso tape on equipment with Group IIC classification?

A

NO

Denso tape is only allowed to be used on Group IIA and IIB equipment

17
Q

Ex d enclosures

Can Non-setting grease be used on flame paths and machined surfaces?

A

YES

Non-setting grease provides an additional layer of ingress protection and inhibits formation of rust. Types of grease should be recommended by the manufacture.

18
Q

Ex d Barrier Glands

For Ex d enclosures which have an internal ignition source,

When is a barrier gland required to be installed in an Ex d enclosure?

A

A barrier gland is required

Enclosure is greater than 2-litres in Zone 1 and Zone 2  
EPL Gb (Cat 2)  EPL Gc (Cat 3)

Enclosures with Gas Group IIC that have an ignition source.

19
Q

Ex d Cable Entry.

What is the minimum number of threads required on threaded cable entries?

A

6 threads minimum

Metric pitch form 1.5mm

Metric medium and Metric Fine are allowed

20
Q

Ex d Glands
Thread Engagement

An Enclosure having a internal volume of less than 0.1 litres (less than 100cm3) how many threads of engagement are required?

A

5 Full threads of engagement and axial length of 5mm

21
Q

Ex d Glands
Thread Engagement

An Enclosure with a volume greater than 0.1 litres (more than 100cm3) how many threads of engagement are required?

A

5 Full threads and an axial length of 8mm.

22
Q

Ex d Flange Faces obstacle clearance.

What is the minimum clearance for Gas Group IIA

GAS GROUP A
ETHANE        C2H6
PROPANE      C3H8
CYCLOPROPANE   C3H6
ACETONE      C3H6O
METHANE     CH4
BENZENE       C6H6
HEXANE         C6H14
TOLUENE       C7H8
GASOLINE     C8H18
AMMONIA       NH3
KEROSENE     CxHy
Kerosene carbon atoms range C6 to C20
XYLENE
A

10 mm

Minimum clearance

23
Q

Ex d Flange Faces obstacle clearance.

What is the minimum clearance for Gas Group IIB

GAS GROUP B
ETHYLENE C2H4
HYDROGEN SULPHIDE H2S
DIBUTYL ETHER C8H18O

A

30mm

Minimum clearance

24
Q

Ex d Flange Faces obstacle clearance.

What is the minimum clearance for Gas Group IIC

GAS GROUP C
HYDROGEN H2
ACETYLENE C2H2
CARBON DISULPHATE CS2

A

40mm

Minimum Clearance

25
Q

Atex Inspections

A = ?

B = ?

C = ?

A

A = General all equipment

B = Installation

C= Environment

26
Q

Ex d flame proof enclosures

What are the two types entry into of flameproof enclosure?

A

Direct Entry
Single flame proof chamber all components installed

Indirect Entry
Has two separate chambers. One chamber only contains terminals for connection of cables. The second chamber contains the arcing components. Connection between the two chambers is via a flame proof interface

27
Q

DRAIN PLUGS

What are the installation requirements of Breather/Drain plugs?

A

Bd and Be breather drains without drain holes must not protrude within the enclosure.

Breather / Drains must utilise the castled locknut provided within clearance holes.

Type Be Breather / Drains are only suitable for bottom entry within Ex e enclosures with a minimum wall thickness of 1mm

COMPEX (14 decks)

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