UNIT 3: Flameproof Ex d Flashcards
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.
Five full threads.
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
Non setting grease
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.
Alteration of the internal component layout
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
To cool the hot gases produced by an internal explosion.
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.
Gas around the enclosure will not be ignited by an internal explosion.
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
All bolts to be replaced - spanner tight - and flamepath gaps checked.
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.
Flanged and/or spigot joints
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
40mm
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.
All cover bolts fitted and spanner tight
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.
Using an Exd adaptor with appropriate thread forms
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.
Prevent the effects of an internal ignition transmitting to and igniting an external flammable gas.
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.
Ignition in one section of an enclosure causing a stronger secondary
explosion in another connected section.
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
Areas needing EPL Gb and Gc ( Cats 2G and 3G ) equipment
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
Areas requiring either EPL’s Gb or Ge (Cats 2 or 3) gas group IIA or IIB
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
Gb or Gc (Cat 2G or 3G) areas
Ex d enclosures
Denso tape.
Can you use Denso tape on equipment with Group IIC classification?
NO
Denso tape is only allowed to be used on Group IIA and IIB equipment
Ex d enclosures
Can Non-setting grease be used on flame paths and machined surfaces?
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.
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 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.
Ex d Cable Entry.
What is the minimum number of threads required on threaded cable entries?
6 threads minimum
Metric pitch form 1.5mm
Metric medium and Metric Fine are allowed
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?
5 Full threads of engagement and axial length of 5mm
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?
5 Full threads and an axial length of 8mm.
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
10 mm
Minimum clearance
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
30mm
Minimum clearance
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
40mm
Minimum Clearance
