Code of practice for ventilation in petrochemical plants and refineries

IS 12332: Scope & Basis of Design (Clause 4.2)

Scope Summary:

• Covers design of ventilation and air handling systems for industrial applications.
• Specifies methods for heat removal and contaminant extraction.
• Applies to flameproof electrical enclosures, centrifugal and propeller fans, and air filters.

Key Specifications (Clause 4.2.7.1 Systems)

Important Notes:

• Air supply must be forced or forced + positive exhaust.
• Exhaust ventilation must include ducting, grills, blowers, chimneys.
• Air flow rates ensure temperature control and contaminant dilution.

Formula for Air Change Rate (ACH):

[ ACH = \frac{Q \times 60}{V} ]

Where:

• ( Q ) = Volumetric airflow rate (m³/min)
• ( V ) = Volume of space (m³)
• ACH = Air changes per hour

flowchart LR
    A[Heat Removal System] -->|Forced Supply| B[Air Flow ≥ 12 ACH]
    C[Gas/Contaminant Removal] -->|Mechanical Exhaust| D[Air Flow 12-20 ACH]
    B & D --> E[Maintain Temp & Air Quality]

For detailed fan specs, filter testing, and flameproof enclosure standards, refer to respective clauses and referenced IS codes within IS 12332.

IS 12332 - Definitions & Key Specifications

Clause 2.0: Definitions

• This clause establishes the terminology used throughout the standard to ensure uniform understanding.
• Definitions cover terms related to flameproof enclosures, fans, air filters, and ventilation components.

Clause 4.2: Basis of Design

• Specifies design principles and criteria for electrical apparatus and ventilation equipment to ensure safety and performance.

Clause 7.3: Suggested Duct Velocities for Various Media

Clause 22.5: Testing & Specifications

• Covers test procedures for flameproof enclosures and specifications for propeller and centrifugal fans.
• Includes methods for testing panel type air filters used in air-conditioning and ventilation.

Summary

• Use design velocities from Clause 7.3 for duct design based on the conveyed medium.
• Refer to Clause 22.5 for testing standards of fans and enclosures.
• Clause 2.0 ensures consistent terminology throughout the standard.

flowchart TD
    A[Definitions (Clause 2.0)] --> B[Basis of Design (Clause 4.2)]
    B --> C[Design Velocities (Clause 7.3)]
    C --> D[Testing & Specifications (Clause 22.5)]

For detailed design and testing, always refer to the full IS 12332 document.

IS 12332: Criteria for Location of Buildings

Key Specifications:

• Clause 3.2 - Area Classification:

  • Prefer location in electrically safe (non-hazardous) areas to avoid costly hazardous equipment.
  • Avoid populated areas to reduce risk.
  • Ensure compliance with the Environment Protection Act, 1986.
  • Consider environmental impact and surroundings.

• Clause 3.3 - Wind Conditions:

  • Minimize infiltration by placing cracks, crevices, window openings strategically.
  • Design openings to reduce air infiltration, especially under prevailing wind directions.

Important Definitions:

• Wet Bulb Temperature (Clause 2.23):
  Temperature measured by a thermometer with a wetted bulb exposed to airflow ≥ 4.5 m/s, important for HVAC and ventilation design.

Practical Design Tips:

flowchart LR
    A[Select Site] --> B{Area Classification}
    B -->|Non-Hazardous| C[Proceed]
    B -->|Hazardous| D[Reconsider Location]
    C --> E[Analyze Wind Direction]
    E --> F[Locate Openings to Minimize Infiltration]
    F --> G[Check Environmental Compliance]
    G --> H[Finalize Location]

This ensures safe, cost-effective, and environmentally sound building placement per IS 12332.

IS 12332: Design Considerations - Key Points

1. Basis of Design (Clause 4.2)

• Design must consider wind conditions to minimize infiltration through cracks, crevices, and openings (Clause 3.3).
• Openings should be located to reduce air leakage and maintain building integrity.

2. Design Velocity for Ducts (Clause 7.3, Table 7.1)

• Use these velocities to ensure efficient and safe material conveyance without excessive wear or pressure loss.

3. Additional Specifications (Clause 22.5)

• Flameproof enclosures for electrical apparatus.
• Specifications for propeller and centrifugal fans.
• Testing methods for panel type air filters.

Summary Diagram: Design Flow for Ventilation Ducts

flowchart TD
    A[Assess Wind Conditions] --> B[Locate Openings to Minimize Infiltration]
    B --> C[Select Conveying Medium]
    C --> D[Determine Design Velocity from Table 7.1]
    D --> E[Design Ducts & Fans per Specified Velocity]
    E --> F[Apply Flameproof & Testing Specifications]

Keep in mind: Proper selection based on medium and velocity ensures durability, efficiency, and compliance with IS 12332.

IS 12332: System Components – Key Formulas & Specifications

1. Ventilation Air Flow Rates (Clause 4.2.7.1)

• Heat removal:
  • Minimum 12 air changes/hour.
  • Pit temperature rise ≤ 5°C above ambient.
• Gas/contaminant removal:
  • Mechanical exhaust system with 12 to 20 air changes/hour depending on application.

2. Air Washer Applications (Clause 4.2.8)

• Used for:
  • Maintaining high relative humidity & dry bulb temperature.
  • Filtering dust and gaseous fumes.
  • Useful in spaces with high sensible heat generation.

3. Relevant Standards for System Components (Clause 22.5)

Basic Air Change Rate Formula:

[ \text{Air Flow Rate (m}^3/\text{hr)} = \text{Volume of Space (m}^3) \times \text{Air Changes per Hour} ]

Summary Diagram:

flowchart LR
    A[Conditioned Space] -->|Heat Removal| B[Forced Supply + Exhaust Ventilation]
    A -->|Gas Removal| C[Mechanical Exhaust System]
    A -->|Humidity Control| D[Air Washer]
    B -->|Min 12 ACH| E[Maintain ≤5°C Temp Rise]
    C -->|12-20 ACH| F[Remove Contaminants]
    D -->|Filter Dust & Fumes| G[Maintain RH & Temp]

Note: Always refer to IS 12332 Clause 4 and 22 for detailed design and testing requirements of ventilation system components.

IS 12332: Installation and Operation - Key Points & Formulas

1. Temperature Indication (Clause 5.5.5)

• Temperature indication must be provided in the workroom.
• Maintain temperature within specified limits.

2. Ventilation System Design (Clause 4.2.7.1)

• Heat Removal:

  • Use forced supply or forced supply + positive exhaust ventilation.
  • Airflow to limit pit temperature rise ≤ 5°C above ambient.
  • Minimum 12 air changes per hour (ACH) required.

• Gas/Contaminant Removal:

  • Mechanical exhaust ventilation with ducts, grills, blowers, chimneys.
  • Air exhaust rate: 12 to 20 ACH, depending on application.

3. Air Changes per Hour (ACH) Calculation

[ ACH = \frac{60 \times Q}{V} ] Where:

• ( Q ) = Volumetric airflow rate (m³/min)
• ( V ) = Volume of the room or pit (m³)

4. Summary Table: Ventilation Requirements

flowchart LR
    A[Heat Source] --> B[Work Room]
    B --> C[Forced Supply Ventilation]
    B --> D[Mechanical Exhaust Ventilation]
    C --> E[Maintain ≤ 5°C Temp Rise]
    D --> F[Remove Gases/Contaminants]
    E & F --> G[Maintain Air Changes: 12-20 ACH]

For detailed specifications on flameproof enclosures, fans, and filters, refer to Clause 22.5 and related referenced standards.

IS 12332: Testing and Performance Evaluation Key Points

1. Testing at Works (Clause 7.1)

• Filters Testing: As per IS 7613-1975, panel type air filters for air-conditioning and ventilation are tested for:
  • Dust holding capacity
  • Airflow resistance
  • Efficiency in particle removal

2. Specifications Covered (Clause 22.5)

• Flameproof enclosures for electrical apparatus
• Propeller type AC ventilating fans (1st revision)
• Centrifugal fans
• Panel type air filters testing method

3. Key Testing Parameters & Formulas

• Airflow Rate (Q):
  [ Q = A \times V ]
  where,
  (A) = cross-sectional area (m²),
  (V) = velocity of air (m/s)

• Pressure Drop (ΔP): Measured across filter to assess resistance.

• Filter Efficiency (η):
  [ \eta = \frac{C_{in} - C_{out}}{C_{in}} \times 100% ]
  where,
  (C_{in}) = particle concentration before filter,
  (C_{out}) = particle concentration after filter.

4. Reference Table: Sample Filter Test Parameters

For detailed procedures and exact values, refer to IS 7613-1975 for filters and respective IS codes for fans and enclosures.

flowchart LR
    A[Air Intake] --> B[Filter]
    B --> C[Measure Pressure Drop ΔP]
    B --> D[Measure Particle Concentration Out]
    A --> E[Measure Particle Concentration In]
    E & D --> F[Calculate Efficiency η]

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