Hazardous Area Classifications and Protection Methods for Electrical Equipment

Hazardous Area Classifications

When it comes to hazardous areas, it is crucial to understand the different protection methods available for instrument and electrical equipment. The three most commonly used methods are:

1) Intrinsic Safety (IS) - Ex'i'

Intrinsic Safety (IS) involves designing equipment to reduce the available energy to a level where it is too low to cause ignition. This method aims to prevent sparks and maintain low temperatures.

2) Increased Safety - Ex'e'

Increased Safety is a fail-safe design method that enhances insulation values, creepage, and clearance distances beyond normal requirements. This approach provides a safety factor against accidental breakdown.

3) Flameproof - Ex'd'

Flameproofing entails placing parts that can ignite in an explosive atmosphere within an enclosure capable of withstanding the force and pressure generated during an internal explosion. In the event of an explosion, the enclosure either contains it or cools down any escaping flames.

For areas classified as Zone 1 and Zone 2 hazards, motor designs such as "Flameproof with Increased Safety Terminal Box" (Ex‘db’eb’) and "Increased Safety" (Ex‘eb’) are permissible.

Specific Types of Protection for Electrical Equipment

The following protection methods are applicable to electrical equipment in Class I, Zone 1, and Zone 2 areas:

- Local Control Stations: Ex 'db eb', Ex 'eb'

- Convenience Sockets: Ex 'db eb', Ex 'eb'

- Lighting Fixtures: Ex 'eb', Ex 'db eb', Ex 'db'

- Junction Boxes: Ex 'eb'

- Local Control Panels: Ex 'eb', Ex 'db eb'

- Motors: Ex 'db eb', Ex 'eb'

- Sparking Components: Ex 'db eb'

- Termination Facilities: Ex 'eb'

By implementing these protection methods, you can ensure the safety and reliability of instrument and electrical equipment in hazardous areas.

Hazardous Area Classifications & Protections: Equipment Protection Level (EPL), Zones, Marking, and Certifications

Hazardous Area Classifications & Protections

In industries dealing with hazardous materials, such as the Oil and Gas industry, understanding hazardous area classifications and equipment protection is crucial. Here are important details about Equipment Protection Level (EPL), zones, marking, and certifications:

Equipment Protection Level and Zones:

Electrical and electronic equipment installed in hazardous (classified) locations must comply with the requirements of IEC 60079-14. When EPLs are identified in the area classification documentation, the selection of equipment should follow the corresponding requirements.

Equipment Protection Levels and Assigned Zones:

- Zone 0: "Ga"

- Zone 1: "Ga" or "Gb"

- Zone 2: "Ga", "Gb", or "Gc"

- Zone 20: "Da"

- Zone 21: "Da" or "Db"

- Zone 22: "Da", "Db", or "Dc"

Exceptions and Restrictions for Equipment Protection Techniques:

a) Zone 1 Areas:

i. Medium Voltage (MV) motors (601-15,000 V range) and sparking equipment (equipment with contact) such as switchgear and control gear should have type of protection "d".

ii. "de" type MV motors (flameproof motor with increased safety terminals) can be used.

iii. Increased safety "e" type MV motors are not permitted.

b) Zone 2 Areas:

i. Motors and non-sparking equipment should have a minimum type of protection "n".

ii. Sparking equipment (equipment with contact) should have type of protection "d".

iii. MV motors with voltage exceeding 4.8 kV and driving centrifugal/screw hydrocarbon or hydrogen compressors should have type of protection as in "Zone 1" or "p". Type of protection "n" or "e" is not permitted.

c) Single-phase motors located in hazardous locations (Zone 1 and Zone 2) should be of the totally enclosed flame-proof Ex-d or Ex-de type as per IEC 60079-1.

Approval for Zone and Properties:

a) Approval for "Zone and Properties" should comply with the requirements of IEC 60079 Series. Equipment should be identified not only for the zone of location but also for the explosive, combustible, or ignitable properties of the specific gas, vapor, dust, or fibers/flyings present.

b) Zone 0, 1, and 2 equipment should not have any exposed surface operating at a temperature exceeding the auto-ignition temperature of the specific gas or vapor.

Marking and Certification:

a) Equipment should be marked according to the requirements of IEC 60079-0.

b) Equipment and materials installed in hazardous areas should have markings as per IEC standards and should be listed, labeled, or certified by recognized Testing Laboratories.

Note: The equipment is certified for specific ambient temperatures indicated on the certification. Exposing it to higher temperatures may exceed the stated T-Class temperature, potentially leading to unsafe conditions.

c) Assembled equipment and materials in hazardous areas, such as switch-racks, control and distribution panels, should be certified and labeled as complete units in addition to each component having the required certification for the installation area.

Understanding the requirements and certifications for equipment in hazardous areas ensures compliance and promotes safety in these environments.

Hazardous Area Classifications & Protections: SIL, LOPA, and Safety Instrumented Systems

Hazardous Area Classifications & Protections: SIL, LOPA, and Safety Instrumented Systems

Safety Integrity Level (SIL):

Safety Integrity Level (SIL) is a study implemented in hazardous areas to protect against accidents, fires, or blasts in process industries. It is a recent study that complies with the IEC 61508 (Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems) and IEC 61511 (Safety Instrumented Systems for the Process Industry Sector) standards.

Layer of Protection Analysis (LOPA):

The Layer of Protection Analysis (LOPA) is a method used to analyze all process hazards and layers of protection. It acknowledges that a single safety measure alone cannot eliminate risks, and multiple layers of protection are necessary. LOPA is performed after the Hazard and Operability Study (HAZOP) to assess if existing protection measures can reduce risks to an acceptable level.

HAZOP and SIL Study:

While a HAZOP study makes the overall process robust by adding redundant instruments and additional alarms, it does not address the required reliability of the system. SIL studies are essential to determine the necessary reliability and identify if additional safety measures, beyond the HAZOP study, are required.

SIL Levels:

SIL levels, such as SIL 1, SIL 2, SIL 3, and SIL 4, are determined based on hazard frequency and severity. SIL 4 is used for high-frequency and high-severity fault conditions.

Safety Life Cycle:

The Safety Life Cycle provides a structured approach to identify and analyze process hazards and determine if a Safety Instrumented System (SIS) is required. The IEC 61508 standard offers a safety lifecycle model that helps guide new projects in selecting and using the appropriate version for their applications.

SIL Identification, Verification, and Validation:

SIL identification and SIL verification studies are conducted during detailed design engineering for projects, while SIL validation is performed on-site after the installation of all components in the SIL-certified loop.

Application of SIS:

A Safety Instrumented System (SIS) is designed to prevent hazardous events by taking a process to a safe state when predetermined conditions are violated. SISs are also known as safety interlock systems, emergency shutdown systems (ESD), or safety shutdown systems (SSD).

Example:

Consider a pressure vessel containing flammable gas controlled by a PLC-based process control system. Implementing an SIS as an additional safety measure will reduce the risk of overpressure. The SIS may include a pressure transmitter to sense intolerable pressure levels, a logic solver for system control, and a solenoid valve to vent the vessel's contents to a safe location, thereby bringing the pressure vessel to a safe state.

Understanding SIL, LOPA, and the application of SIS is crucial for ensuring safety and mitigating risks in hazardous areas of process industries.

Hazardous Materials: Classification by Class, Division, Group, and Temperature Class

Understanding Hazardous Materials: Classification by Class, Division, Group, and Temperature Class

Hazardous materials can be classified based on the following features:

A) Class:

I) Class A - Gas/Vapour

II) Class B - Dust

III) Class C - Fiber

B) Division:

I) Division I - High probability of the presence of the material

II) Division II - Low probability of the presence of the material

C) Group:

Groups are specific to gases and are classified as follows (applicable only in the case of Class A):

Group A

Group B

Group C

Group D

D) Temperature Class:

Temperature Class indicates the ignition temperature of materials and is denoted by T1 to T6:

T1 - 450°C

T2 - 300°C

T3 - 200°C

T4 - 135°C

T5 - 100°C

T6 - 85°C

Examples:

A combination can be Class B, Division I, Group A, T4, indicating a hazardous material that is a dust, with a high probability of presence, belonging to Group A, and having an ignition temperature of 135°C.

Understanding the classification of hazardous materials based on class, division, group, and temperature class helps in identifying and managing potential risks associated with different substances. It plays a crucial role in ensuring safety measures are in place to handle and store hazardous materials appropriately.

HAZARDOUS AREA & PROTECTION METHODS

HAZARDOUS AREA

There are two categories used to classify hazardous areas:

A) Zones

B) Groups

A) Zone Category

1) Zone 0: Hazardous gas is present continuously.

2) Zone 1: Hazardous gas is present intermittently.

3) Zone 2: Hazardous gas can be present due to leakage.

4) Zone 20: Hazardous dust is present continuously.

5) Zone 21: Hazardous dust is present intermittently.

6) Zone 22: Hazardous dust can be present due to leakage.

Group Category

1) Group I: Mine area

2) Group II: Gas

   - Group II A corresponds to Zone 0

   - Group II B corresponds to Zone 1

   - Group II C corresponds to Zone 2

3) Group III: Dust

   - Group III A corresponds to Zone 20

   - Group III B corresponds to Zone 21

   - Group III C corresponds to Zone 22

PROTECTION METHODS - EXPLOSION PROOF & FLAMEPROOF

Ex Ia & Ex Ib: Intrinsically safe instruments are designed in a way that the energy produced by any spark is lower than the ignition energy of a flammable mixture. Ex Ia instruments have a higher integrity level and can be used in Zone 0 hazardous areas, while Ex Ib instruments are suitable for Zone 1 and 2 locations.

Ex d: Flameproof cable instruments are designed to contain or control an ignited flammable mixture and prevent it from igniting any external flammable mixture. This protection method is applicable in Zones 1 and 2 hazardous areas.

Ex e: Increased safety cable instruments are designed using components that do not create arcs or sparks, ensuring ignition prevention. The enclosures of these instruments can be made from thinner materials, but they must be sealed to at least IP54 ingress protection level. This protection method can be used in hazardous area Zones 1 and 2.

Ex p: Pressurized equipment that is continuously pressurized to expel flammable mixtures. This protection method can be used in Zones 1 and 2.

Ex nA: Similar to Ex e, equipment under this protection method should not create arcs or sparks, but with less stringent requirements. This protection method is limited to Zone 2 only.

Ex nR: Restricted breathing equipment is equipped with tightly fitting seals that prevent explosive mixtures from entering and reaching hot components. This protection method is limited to Zone 2 only.

INTERNATIONAL CLASSIFICATIONS OF HAZARDOUS AREAS

ATEX: The European Directive requires and certifies instruments intended for explosive atmospheres in hazardous areas to be designed and manufactured in a way that minimizes the occurrence and limits the severity of accidental explosions.

IECEx: The International Electrotechnical Commission System provides hazardous area certification for instruments to be used in potentially explosive atmospheres.

EAC EX: The TR CU Certificate of Conformity for the Russian Customs Union is mandatory for electrical equipment intended for operation or installation in hazardous areas and potentially explosive atmospheres in these countries.

INMETRO: This certification body in Brazil ensures that electrical instruments meet the requirements for use in hazardous and potentially explosive atmospheres.

CSA: An expert source for Ex testing and Ex certification of explosion-proof instruments used in hazardous locations and potentially explosive atmospheres across North America.