UNIT 6: Pressurization EX p Flashcards
1.
For an area requiring EPL Gc (Cat 3) equipment, which one of the following options may be used if the pressurised enclosure contains an ignition source?
No protection required
Ex py
Ex px
Ex px or Ex pz.
Ex px or Ex pz.
2.
Where a pressurised enclosure contains no ignition source, which one of the following will suit an area requiring EPL Gb (Cat 2) equipment?
Ex py
No protection required
Ex px
Ex px or Ex pz.
Ex py
3.
Where a pressurised enclosure contains no ignition source, which one of the following will suit an area requiring EPL Gc Cat 3) equipment?
Ex py;
No protection required
Ex px;
Ex px or Ex pz.
No protection required
4.
Protection types for pressurised enclosures are?
Ex p1, Ex p2, Ex p3
Ex px, Ex py, Ex pz
Ex pG, Ex pD
Ex pa, Ex pb or Ex pc
Ex px, Ex py, Ex pz
5.
Which one of the following statements represents the type of protection Ex p:
The internal pressure has to be greater than 0.5 Bar
The air used for pressurisation shall be taken from a specified non-
hazardous area
Pressurisation of the enclosure is intended to contain explosive gases
Switching on is only permitted after the enclosure has been pressurised for
at least 15 minutes.
The air used for pressurisation shall be taken from a specified non-hazardous area
6.
The interior of a pressurised control room - in a location requiring EPL Gc(Cat 3), is ‘safe’ provided the pressurisation is maintained and there are no gases released internally.
What action is required if the pressurisation fails and the
internal equipment does not meet EPL Gc (Cat 3) requirements?
Alarm sounds and all flameproof equipment must be isolated
On operation of alarm, automatic disconnection of all equipment
No action
On operation of alarm, immediate action taken to restore
On operation of alarm, immediate action taken to restore
7.
Ex p equipment is permitted in which one of the following areas?
Main area needing EPL Gc (Cat 3G) only
An area needing EPL Ga (Cat 1 G) only
An area needing EPL Gb (Cat 2G) only
An area needing EPL’s Gb or Gc Cats 2G or 3G) only
An area needing EPL’s Gb or Gc Cats 2G or 3G) only
8.
A pressurised enclosure, containing ignition capable components, is rated EPL Gb (Cat 2). Which one of the following options may be used?
No protection required
Ex py
Ex px
Ex px or Ex pz.
Ex px
Ex i
When the zener diode fails, does in normally fail open circuit open circuit or short circuit?
Test show that diodes always test to a short circuit condition.
Zener diodes can only be considered infallible when 2 or more diodes are connected In parallel.
Ex i capacitance vrs inductance.
How is capacitance and inductance of an IS circuit influenced by IS circuit Voltage!
At lower voltages (say 5 volts) inductance will be predominant
At higher voltages (say 28 volts) capacitance will be predominant.
[affects of stored energy in a circuit as a result of circuit inductance and capacitance]
IS earth
What are the maximum allowable resistance between Barrier Earth and the main earth point?
The maximum resistance between barrier earth and the main earth point should not be greater than 1 ohm.
IS earth
What is the minimum allowed cross sectional area of an IS earth conductor?
The minimum cross sectional area allowed is
Two separate 1.5nm2 copper conductors
One 4mn2 copper conductor.
IS Earth.
What are the requirements when two separate Earth conductors are installed as a Barrier Earth?
Where two earth conductors are installed, each earth conductor to be secured at separate points at each end to connect the Barrier Earth Bar to the Main Earth Point.
IS Earth Conductor
When installing an IS Earth what must be considered in terms of short circuit currents?
The IS earth conductor must be rated and capable of carrying maximum fault current of the IS Circuit.
IS Earth Conductor
What is the insulation requirement on the IS conductor?
The IS Earth conductor must be insulated and Undamaged along its entire length, to prevent contact with any exposed metal work in the plant
IS Circuit
What is the minimum requirement of an IS Circuit in terms of insulation resistance test voltage to Earth.
The IS Circuit in the hazardous area must be able to withstand a 500 volt insulation resistance test to Earth.
IS cable screens will have sheathing capable of withstanding 500vac or 750Vdc
Ex pxb
What is the definition of Ex pxb?
Ex pxb pressurisation reduces the equipment protection level within the pressurised enclosure from Gb to Non-Hazardous
Minimum overpressure of 0.5 mBar required.
Non-Ex components can be installed inside the pressurised enclosure.
Approved for use in EPL Gb and Gc. (Zone 1 and Zone 2)
Ex pzc
What is the definition of Ex pzc?
Ex pzc pressurisation reduces the equipment protection level within the pressurised enclosure from Gc to Non-Hazardous.
Minimum overpressure of 0.25 mBar required
Non-Ex components can be installed inside the pressurised enclosure.
Approved for use in EPL Gc. (Zone 2)
Ex pyb
What is the definition of Ex pyb
Ex pyb pressurisation reduces the equipment protection level within the pressurised enclosure from Gb to Gc.
Minimum overpressure of 0.5 mBar required
Only components tested for Zone 2, as a minimum, can be installed inside the pressurised enclosure.
Approved for use in EPL Gb and Gc (Zone 1 and Zone 2)
Ex pxb
What is the required action in event of loss of pressure in Ex pxb enclosure?
EPL Gb (Zone 1) EPL Gc (Zone 2)
Ex pxb loss of pressure.
EPL Gb (Zone 1) Alarm and shutdown. Alternate gas supply should be available in more dangerous Atmospheres Areas
EPL Gc (Zone 2) Alarm and requires immediate action to restore the integrity of the system.
Ex pzc
What is the required action in event of loss of pressure in a Ex pzc enclosure
EPL Gc (zone 2) only
Ex pzc loss of pressure.
Gc (Zone 2)
Alarm and requires immediate action to restore the integrity of the system.
Ex pyb
What is the required action in the event of loss is pressure in an Ex pyb Enclosure?
EPL Gb (Zone 1) EPL Gc (Zone 2)
Ex pyb loss of pressure.
EPL Gb (Zone 1) Alarm and requires immediate action to restore the integrity of the system.
EPL Gc (Zone 2) No action required. Ex pyb enclosure only contains equipment that is already rated and approved for use in EPL Gc (Zone 2)
Ex ma
Encapsulation apparatus with a protection Level Ex ma must not be capable of causing ignition during what situations?t
Ex ma
No ignition in normal operation and installation conditions.
No ignition in any specified abnormal conditions.
No ignition in defined failure conditions.
Must not have an operating voltage in excess of 1kV
Approved for use in EPL Ga, Gb, Gc
(Zone 0, 1, 2)
Ex mb
Encapsulation apparatus with a protection Level Ex mb must not be capable of causing ignition during what situations?
Ex mb
No ignition in normal operation and installation conditions.
No ignition in defined failure conditions.
Approved for use in EPL Gb, Gc)
(Zone 1, 2)
