Instrumentation Engineering Standards Interview Questions and Answers

In the field of Instrumentation Engineering, adherence to standards is critical to ensuring the safety and reliability of equipment. This extensive guide answers important questions about IP, ATEX Standards, and CE Markings, providing clarity on the important elements of compliance and regulations.

Instrumentation Engineering Standards Interview Questions and Answers

Ingress Protection (IP) Standards Questions and Answers

What does IP stand for?

  • IP stands for Ingress Protection.

Why is Ingress Protection Important?

  • Ingress of liquid and/or solid particles into electrical equipment may be hazardous not only to the equipment but also to the operator.
  • When purchasing electrical equipment, such as an electric motor, a light fitting, or an enclosure, it is critical to understand the degree of ingress protection provided.

How is Ingress Protection quoted?

  • An “IP” number, commonly referred to as an IP rating, is used to define the level of environmental protection supplied.
  • The IP rating is made up of two numbers, the first of which refers to the protection against solid object entrance and the second to the protection against liquid penetration. The higher the number, bigger the level of protection.

Are there standards covering IP ratings?

The following European standards apply to ingress protection:

  • BS EN 60529 Protection Degrees Provided by Enclosures Specification
  • IEC 529 Specifies the Degrees of Protection Provided by Enclosures

What do they use outside Europe?

  • The NEMA classification is in use across North America. National Electrical Manufacturers Association, or NEMA, is a US trade association that represents the interests of companies in the electro industry that produce goods for use in electricity generation, transmission, distribution, control, and end use.

How does the IP and NEMA systems compare?

  • It is not possible to properly compare the IEC and NEMA degrees of protection as similar ratings.
  • Tests for environmental factors such mechanical damage, corrosion, rusting, ice formation, etc. are included in the NEMA Standard. In any scenario, the table that follows may be used as a reference.
NEMA and IEC Enclosure Classifications
NEMA Enclosure TypesIEC Enclosure Classification Designation
1General Purpose – IndoorIP10Shielded from solid objects up to 50mm, such as inadvertent contact by hands..
2Drip-Proof – IndoorIP11Defended against solid objects up to 50mm, like accidental touch by hands.
Safeguarded against vertically falling water droplets, for instance, condensation.
3Dust-tight, Rain-tight, Sleet-tight – OutdoorIP54Secured against the limited ingress of dust, preventing harmful deposits.
Defended against water sprayed from all directions, with restricted ingress allowed.
3RRain-tight, Sleet Resistant- OutdoorIP14Guarded against solid objects up to 50mm, like unintentional touch by hands.
Defended against water sprayed from all directions, with restricted ingress allowed.
3SDust-tight, Rain-tight, Sleet-tight- OutdoorIP54Safeguarded against limited dust ingress, ensuring no harmful deposits.
Defended against water sprayed from all directions, with restricted ingress allowed.
4Water-tight, Dust-tight, Sleet Resistant-Indoor & OutdoorIP56Secured against limited dust ingress, preventing harmful deposits.
4XWater-tight, Dust-tight, Corrosion-Resistant- Indoor & OutdoorIP56Protected against dust limited ingress, avoiding harmful deposits.
5Dust-tight, Drip-Proof–IndoorIP52Defended against dust limited ingress, preventing harmful deposits.
Protection against water sprayed up to 15 degrees from the vertical.
6
Intermittently Submersible, Waterproof, and Resistant to Sleet – Suitable for Indoor and Outdoor Use.
IP67Completely shielded against dust.
Safeguarded against the effects of immersion between 15cm and 1m.
6PWater-resistant and Sleet-resistant – Endures Prolonged Submersion – Applicable for Indoor and Outdoor Environments.IP67Fully protected against dust.
Secured against the effects of immersion between 15cm and 1m.
12Dust-tight and Drip-tight- IndoorIP52Defended against limited dust ingress, preventing harmful deposits.
Protection against water sprayed up to 15 degrees from the vertical.
12KDust-tight and Drip-tight, with Knockouts- IndoorIP52Defended against limited dust ingress, preventing harmful deposits
Protection against water sprayed up to 15 degrees from the vertical.
13Oil-tight and Dust-tight- IndoorIP54Defended against limited dust ingress, preventing harmful deposits.
Guarded against water sprayed from all directions, with restricted ingress allowed.

Does NEMA produce standards?

Indeed, both NEMA Standard Publication 250 and UL 40 Standard Publication offer valuable insights into ingress protection ratings used in the United States.

Questions & Answers on ATEX Standards

What is Atex?

  • The EU directive 94/9/EC, Equipment and Protective Systems intended for use in Potentially Explosive Atmospheres, is commonly known by its common name, ATEX.
  • The term “ATEX” is derived from the French expression “ATmospheres EXplosibles.”

What is the intent of the ATEX Directive?

  • The ATEX Directive facilitates the free trading of ATEX products within the European Economic Area by unifying documentation and testing requirements.
  • Manufacturers may indicate compliance with this Directive (and any other applicable Directive) on their products by adding a single CE mark.

What does ATEX apply to?

  • The ATEX directive covers both electrical and mechanical equipment designed for potentially explosive atmospheres. 
  • This includes equipment and protective systems meant for use within these atmospheres. 
  • Additionally, it applies to devices needed for the safe operation of equipment inside explosive atmospheres, even if used outside, as well as components related to these devices. 
  • In essence, ATEX ensures safety in areas where explosive conditions may exist, extending its reach to various types of equipment and related components.

To what industries does ATEX apply?

  • Any industrial area with the possibility of an explosive environment is regulated by ATEX standards.
  • e.g., water and other chemical processing environments, factories, mines, agricultural silos, and oil and gas platforms.

To whom does ATEX apply?

  • Designers, manufacturers, and sellers within the EU involved with equipment for potentially explosive atmospheres must comply with the ATEX Directive 94/9/EC.

How can I determine if a product adheres to ATEX compliance?

  • Compliance involves meeting technical objectives and marking the product with the CE Mark and the distinctive Ex mark.

What other marking can be shown?

  • Essential markings include the CE Mark, Ex-marking symbol, ATEX data, manufacturer details, and safety information.

Can you provide an illustration of the CE, EX, and ATEX data marking?

  9876    II  2  G

What does the ATEX data mean?

The ATEX Directive distinguishes two types of equipment.

  • Group 1 equipment is designed for mining applications. M1 and M2 are the two categories. M1 denotes equipment that must continue to work in the presence of a potentially explosive atmosphere. M2 designates equipment that does not work in the presence of a potentially explosive atmosphere.
  • Group 2 is for all other conditions. There are three categories: 1, 2, and 3. Category 1 equipment is designed for usage in Zone O environments. Category 2 equipment is designed for usage in Zone 1 environments. Category 3 equipment is designed for usage in Zone 2 environments.

What are Zones? D and the G?

  • Zoned locations are those where combustible materials may be released into the atmosphere.
  • The subscripts 0, 1, and 2 describe the likelihood of a flammable material being released in explosive concentrations into the atmosphere.
  • The letter G indicates that the item has been tested for potentially explosive atmospheres due to the presence of gas.
  • D indicates that the item has been tested for potentially explosive atmospheres due to dust present.

Questions & Answers on CE Markings 

What is CE marking?

  • CE certification identifies a product as adhering to European Directives. When a company affixes a CE mark to their products they are confirming compliance with ALL Relevant EC Directives.

When was the commencement of using the CE mark?

  • CE marking for instruments became mandatory on January 1, 1996, within the European Economic Area.
  •  All electronic equipment supplied within the European Economic Area must now bear the CE mark. The rules do not apply retroactively.

What does a CE mark look like?

Displayed prominently, the CE mark is usually stamped on the manufacturer’s nameplate.

What European Directives are relevant to Instrumentation?

Relevant directives include the 

  • Electromagnetic Compatibility Directive
  • Low Voltage Directive
  • Pressure Equipment Directive
  • ATEX.

Which countries demand a CE mark?

  • It is necessary in all 27 European Union (EU) member countries and the three EFTA (European Free Trade Association) member countries. It is estimated that approximately 70% of all products sold in these nations must be labeled.
  • CE marking obtained in one EU nation is valid in all other EU countries and in EFTA countries. It allows the product to be freely moved throughout all 28 nations

Who belongs to the European Union?

Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Holland, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, and the United Kingdom are among the countries represented.

Who belongs to EFTA ?

EFTA includes Iceland, Liechtenstein, Norway, and Switzerland.

Who Ensures Compliance?

  • The manufacturer, importer, supplier, and buyer are all covered by the legislation.
  • It is illegal to sell a product that is not CE marked, regardless of where it is manufactured. As a result, the manufacturer, importer, and supplier must verify that their items are CE marked.
  • It is also illegal to use unlabeled items. As a result, the consumer must confirm that the products are CE marked.
  • The enforcement of the law is the responsibility of the competent regulatory agency in the relevant nation. In the United Kingdom, this is the responsibility of local government’s trading standards department.

What about spare parts?

  • Components with no intrinsic function may not require a CE mark, but spare parts for certain applications must be marked.

Questions & Answers on Hazards

What is Zone Classification in Hazards Location ?

  • Zone signifies something different depending on where you are in the world: North America, Europe, or elsewhere.
  • Each country may have its own set of electrical codes that impose varying requirements on hazardous-area equipment. We usually get requests for installation equipment in one of four different types of Zone designated dangerous areas:
  • Class I/II, Zone 1 and 2
  • ATEX Class I/II, Zone 1 and 2
  • ATEX Zone 1/21 and 2/22
  • IECEx Zone 1/21 and 2/22

What is the hazard?

  • Combustible Gas and dust create explosive environments, each behaving uniquely.

Where will this equipment be installed?

  • The installation’s location determines the applicable standards, with Class, Zone, AEx Class, ATEX, and IECEx systems offering varying certifications.

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