: QUALITY AUDITS AND REVIEWS (part 2)

Question 1

What design codes do you normally use?

Answer 1

IP – (Institute of Petroleum) Zones due to release timing of flammable materials

Question 2

What type of classifications do you know on electrical equipment?

Answer 2

• For Zone 1, LV motors and all inherently non-sparking equipment, e.g., junction boxes and luminaires, shall have type of protection ‘e’. HV motors and all inherently sparking equipment, e.g., switchgear and control gear, shall have type of protection ‘d’. Where such type of protection is not available, e.g., large high speed HV motors, type of protection ‘p’ shall be used. HV motors with type of protection ‘e’ shall not be used.
• For Zone 2, all motors and inherently non-sparking equipment shall have type of protection ‘n’. Inherently sparking equipment shall have type of protection ‘d’ or ‘p’, as stated for Zone 1. HV motors with type of protection ‘n’ shall not be installed in Zone 2 areas where:
  1) the motor voltage exceeds 11 kV,
  or 2) the motor drives a centrifugal/screw hydrocarbon gas compressor.
• For the purpose of commonality of spares and to cater for the possibility of re-classification of areas, consideration should be given to installing Zone 2 equipment in outdoor non-hazardous areas within process installations.
  NOTE: This applies specifically to motors, luminaires, RCUs and power and convenience outlets.
• Electrical equipment installed in indoor, non-hazardous areas within process areas shall be of a standard industrial type as specified in the relevant equipment DEPs. Small power and lighting equipment in such indoor areas shall be either of the industrial weatherproof type or of the domestic type depending on the function of the area (6.1).
• Equipment installed in non-hazardous areas outside process installations, e.g., offices, gatehouses, etc., shall be of a normal industrial/domestic type in accordance with national standards of the country of installation.

Question 3

Is it allowed to use zone 1 equipment in zone 2?

Answer 3

Yes, more expensive but not necessarily, eg zone 1 motor in zone 2

Question 4

What type electrical cables are used and why?

Answer 4

Size, type, area of use, cable laying

Question 5

When is XLPE cable used?

Answer 5

Cross-linked polyethylene, insulation for high tension (high voltage) electrical cables.

Question 6

Why is lead sheathing used on cables?

Answer 6

Protection, cheap, light and EMC.

Question 7

What types of cable glands are used in Ex-classified areas?

Answer 7

EexD

Question 8

What factors influence the current carrying capacity of a cable laid in the ground?

Answer 8

Derating factor– Temperature, soil type resistivity, method of group.

Question 9

What is the difference between HV and LV cable regarding the construction of the cable?

Answer 9

Capacitance of cable and leakage, Insulation grade.

Question 10

Why are insulated bearings used in electrical motors?

Answer 10

Circulating current – pitting of bearing

Question 11

What type acceptance tests can you perform on transformers?

Answer 11

Short Circuit test, Open circuit test, Iron & core losses, type test

Question 12

How would you lay single core cables? Why?

Answer 12

Intrefoil, avoiding circulating currents. Reduce magnetic field an also reduce heating

Question 13

How do you test cables after you have installed them?

Answer 13

Megger, continuity and if HV cables then high pot test. 1.5 if new installation after termination.

Question 14

What is a B.O.D?

Answer 14

Interdiscipline specs

Question 15

What is critical path planning?

Answer 15

Identify critical activity with no float day and will impact execution of the activities