Electrical & Instrumentation (E&I) QA&QC Interview Questions

1). What is the maximum percentage of cross section a conduit can be filled with containing three or more wires? 

Pursuant to NEC 501-5(5) © (6), the fills for the wires shall not exceed 25% of the cross-sectional area of the conduit size. 

2). What do the letters PVC stand for in case of cable insulation? 

PVC – Poly-Vinyl-Chloride

3). Instrumentation wires having drain/shield: what is the role of drain/shield in it? 

In order to minimize electrostatic noise so that there is no distribution of unnecessary signals. 

4). According to the Aramco Standards, what should be the minimum distance between LV Power cables and Instrumentation cables in Cable Trays? 

Minimum of 50mm (refer to NEC). 

5). According to the NEC, what is the allowable spacing for 2-inch rigid steel conduit, effectively? 

a) For Horizontal – 3 meter (10 of feet) 

b) For Vertical – 6 meter (20ft.) 

6). What is the minimum size of the grounding grid conductor According to the Per Aramco Standard? 

According to SAES-P-111 – the cross sectional area no less than 70mm2 (2/0 AWG) / for stranded bare copper cable – 4/0 kcmil 

7). From NEC, what would be the size of equipment grounding copper conductors for the equipment protected by the overcurrent device having a rating of 600 Amperes? 

1/0 AWG / 50mm2 / per NFPA art. 250. 122 

8). According to NEC, what would be the size of the grounding electrode copper conductor for alternating current systems if the largest service conductor size is 350 kcmil? 

Per NFPA art. 250. 122 minimum of 120mm² (4/0 AWG) / 350 kcmil 

9). Connecting Constraints of the grounding conductor to the Grounding Grid System which is buried underground?

a) By Thermite Welding 

b) By mechanical compression approved. 

10). On electrical equipment, the following letters denote: Exd, IIB, T5 Which of these markings is explained by what abbreviation? 

 a). Exd – Equipment Standard Symbols 

b). IIB – Gas Classification Group 

c). T5 – Temperature Classification Group

11). In the case of electrical equipment or material being used in hazardous areas, the letter UL (or) C. S. A. may appear; stated what are these abbreviations or what do these mean?

a). Underwriter Laboratories (UL)

b). CSA- Canadian Standard Association

12). From the above NEC classifications, when are seal fittings required and what are they used for?

Hazardous Location 

a). Classified Location 

• Class 1; Zone 0, 1 & 2

b). Unclassified Locations

• Class I, Division. 1 & 2
• Class II, Div. 2
• Class Ill, Wet Location

13). What is the degree bend allowed in a conduit run? Also the max. number of bends.

In terms of degrees shall not be shall not be more than 270 degrees to avoid straining the cables and consequent damage.

14). As per NEC, how many conduit threads should be engaged in hazardous locations?

The National Electrical Code, Article 501-4 (A), stipulates that there must be five (5) complete threads engaged. 

15). What is the coming color code of grounding, neutral and phase conductor?

a). Conductors in phase A are black.

b). Neutral is White,

c). Grounding is Green

16). What is the minimum temperature rating of the low voltage wires?

90°C dry, 75°C wet.

17). Identify the type of electrical test instrument equipment needed for testing the following cables.

a). Power cables for medium voltage-Megger test and DC high potential test.

b). Cathodic protection cables- Holiday Test.

c). Low voltage cables–Resistance Test & Megger Test

d). Cable related to Musical instruments – Megger Test, Continuity Test.

18). Enumerate some of the overall tests demanded for the testing of the under mentioned Electrical Equipment

a). Type Test on oil – Winding Test, Turns Ratio Test and Transformer Oil tester

b). Electrical Motors – Winding test, the DC Resistance test, Megger test and Phase rotation test

c). Batteries – Voltage/Current Test, Specific Gravity (G) Test.

d). Circuit Breakers – Megger Test, Primary Current Inspection Test, and Ductor Test.

19). What is the NEMA rating of the electrical enclosures used in the Indoor, Outdoor & Corrosive Environment?

• Indoor  – NEMA 1
• Outdoor – NEMA 3 (or) 4.
• Corrosive Environment – NEMA 4X 

20). Is it allowed to use the lighting fixture installation as a raceway? 

No.

Lighting fixture shall be used only as a lamp shade to the light bulb etc. 

21). To how many divisions and groups are Class I atmospheric hazards subdivided or classified? 

The locations covered by each division are: 

• Class 1, Zone O – Flammable gasses (or) vapor (vapour) are always present in the area. 
• Class 1, Division 1 –Arrangements of non-ventilated areas where flammable gasses or vapor gasses could exist at normal operating condition. 
• Class 1, Zone 2- In this area flammable gas or vapor is not expected normally or for a short time during their working shifts. 

22). Explain the following for enclosures having an arched electrical device and installed in a hazardous region. 

a). Type – Class 1, Zone O – where in w/c ignitable concentration of flammable gasses or vapors are always present (flammable mixture always present, 10%). 

b). Safety Factor – Class 1, Zone 1 – in which, under normal operation condition, flammable gasses or vapor having a w/c ignitable concentration are often present or may exist in the air, flammable mixture present 0. 1 to 10%. 

c). Flame tight – Class 1, Zone 2 – in w/c ignitable concentration of flammable gasses or vapor are not likely to occur in normal operation and if they do occur are likely to exist only for a short time (normal 0. 01 to 0. 1 % area – unclassified; normal 0. 01 %). 

23) According to Aramco Standard, what should be the maximum value of resistance for the grounding system in an industrial area? 

Not Greater Than 0. 1 ohm. 

24). What are all the sources of information that would be applied to guarantee that a specific electrical installation meets all necessary standards? 

In the case of house construction NEC stands for National Electrical Code. 

• NAFB- National Association of Fire Chiefs,
• UL – Underwriters laboratory, 
• NEMA – National Electrical Manufacturers Association, 
• NETA – National Electrical Testing Association 

25). What E&I QA/QC Engineer will do when he notices violation of any of the above? 

Report to the respective QA/QC manager / Supervisor or file a Raised Non Conformance Report (NCR) to the respective and concerned production unit who will take necessary and corrective action.