NFPA 20 — Standard for Installation of Stationary Pumps for Fire Protections

NFPA 20 — Scope Key Points

• Scope (Clause 1.1, A.1.1):
  Covers design, installation, and testing of stationary fire pumps for fire protection systems.

• Pump Types Covered:

  • Single-stage pumps (4.1, 6.1.1.2, 6.1.1.3)
  • Vertical lineshaft turbine pumps (7.5.1.3, 7.5.1.4)
  • Self-regulating variable speed fire pump units (4.8.9)

• Power Sources:

  • Electric drivers (9.5.3)
  • Engine drives with controllers (12.4.1.3 to 12.4.1.8)

• Water Supplies:

  • Liquid supplies and protection (4.6, A.4.6.1 to A.4.6.4)
  • Domestic and potable water (4.14.1.1.6, 8.5.6)

• Testing & Reliability:

  • Acceptance tests (14.2.6 to 14.2.8)
  • Reliability requirements (4.6.1)

• Key Parameters:

  • Maximum pump brake horsepower (4.5.1)
  • Suction pipe requirements (4.16.8)
  • Discharge cones and valves (4.20.5.1)

Important Formula (Pump Brake Horsepower)

[ \text{Brake Horsepower (BHP)} = \frac{Q \times H \times \gamma}{\eta \times 3960} ]

Where:

• ( Q ) = Flow rate (gpm)
• ( H ) = Total head (ft)
• ( \gamma ) = Specific weight of fluid (lb/ft³)
• ( \eta ) = Pump efficiency (decimal)
• 3960 = Conversion factor for gpm and ft to horsepower

Summary Flowchart of NFPA 20 Scope

flowchart TD
  A[Start: NFPA 20 Scope] --> B[Pump Types]
  B --> B1[Single-stage Pumps]
  B --> B2[Vertical Turbine Pumps]
  B --> B3[Variable

NFPA 20: Key Definitions Overview

Clause 3.3 and Annex C.2 provide the general definitions essential for understanding NFPA 20 requirements. These definitions clarify terminology related to fire pumps, components, and system configurations.

Important Definitions Highlights:

• Drawdown (3.3.17): The time interval during which the fire pump supplies water at a required flow and pressure.
• Designer, System (4.3.2): The individual responsible for specifying the fire pump system.
• Discharge Cone (4.20.5.1): A component directing flow at pump discharge.
• Vertical Lineshaft Turbine Pumps (7.5.1): Pumps with vertical shafts and multiple stages, used for high head applications.
• Variable Speed Drives (10.10.5): Controls that adjust pump motor speed to meet system demand.
• Critical Path Components (14.5.2.5): Parts whose failure directly impacts pump operation.

Key Specifications & Tables:

• Pump Types (11.1.3): Defines pump classifications (horizontal split case, vertical turbine, etc.).
• Tests (14.2.6 - 14.2.8): Procedures for acceptance and performance verification.
• Columns and Shafts (7.3.2): Dimensions and materials for vertical shaft turbine pumps.
• Discharge Control Valves: See Control Valves section for sizing and installation.
• Data Recording Systems (Annex C.8): Configuration for monitoring pump operation.

Summary Flowchart of Definitions Context

flowchart TD
  A[General Definitions 3.3] --> B[Pump Types 11.1.3]
  A --> C[Drawdown 3.3.17]
  A --> D[Discharge Cone 4.20.5.1]
  A --> E[Vertical Turbine Pumps 7.5.1]
  A --> F[Variable Speed Drives 10.10.5]
  A --> G[Critical Components 14.5.2.5]
  B --> H[Horizontal Split Case]
  B --> I[Vertical Turbine]
  E --> J[Columns and Shafts 7.3.2]
  F --> K[Electric Drivers 9.2.3]

Reference:

• Consult **NFPA

NFPA 20: General Requirements - Key Points

1. Scope & References (Clause 2.1, 2.4)

   • NFPA 20 incorporates referenced documents as mandatory parts.
   • Definitions and general requirements are foundational for compliance.

2. Documentation (Clause 4.29.2.4)

   • Engineering calculations and tests must document compliance with performance requirements.

3. Existing Installations (Clause 12.8.1)

   • Existing installations must meet Sections 12.1 to 12.7 plus additional Section 12.8 requirements.

Essential Specifications & Formulas

• Pump Capacity (Q):
  ( Q = \frac{GPM}{\text{flow rate}} ) (gallons per minute)

• Pump Pressure (H):
  ( H = \frac{P \times 2.31}{\rho} ) (feet of head)
  Where:

  • (P) = pressure in psi
  • (\rho) = specific gravity of fluid

• Power Required (BHP):
  ( BHP = \frac{Q \times H \times \rho}{3960 \times \eta} )
  Where:

  • (Q) = flow rate (gpm)
  • (H) = head (ft)
  • (\rho) = fluid specific gravity
  • (\eta) = pump efficiency (decimal)

Typical NFPA 20 General Requirements Flow

flowchart TD
  A[Start: Project Scope] --> B[Review NFPA 20 References]
  B --> C[Define Pump Requirements]
  C --> D[Perform Engineering Calculations]
  D --> E[Conduct Performance Tests]
  E --> F[Document Compliance]
  F --> G[Installation & Inspection]
  G --> H[Final Approval]

Summary: NFPA 20 mandates strict adherence to referenced standards, thorough engineering calculations, and documented testing to ensure fire pump system reliability and compliance.

NFPA 20: Alternate Power Key Points

• Definition (3.3.46.1):
  Alternate Power is an independent power source separate from the primary supply.

• Clause 9.3: Alternate Power Requirements

  • Must provide power to fire pump drivers if primary power fails.
  • Should be automatic and reliable to ensure immediate start.

• Clause 14.2.8: Alternate Power Supply

  • Alternate power must be capable of starting and running the fire pump.
  • Typical sources: emergency generators, batteries, or other independent supplies.
  • Must comply with local electrical codes and NFPA 70 (National Electrical Code).

Typical Design Considerations and Formulas

• Power Capacity:
  [ P = \frac{T \times V \times I \times \sqrt{3} \times \text{Power Factor}}{1000} ]
  Where:

  • ( T ) = Number of phases (usually 3)
  • ( V ) = Voltage (Volts)
  • ( I ) = Current (Amps)
  • Power Factor typically 0.8 to 1.0

• Run Time:
  Alternate power should sustain the fire pump for the required emergency duration (often 2 hours minimum).

Summary Table for Alternate Power Source Selection

flowchart TD
  A[Primary Power Failure] --> B{Is Alternate Power Available?}
  B -->|Yes| C[Start Fire Pump via Alternate Power]
  B -->|No| D[Fire Pump Not Operational]
  C --> E[Fire Pump Runs Until Power Restored]
  E --> F[Switch Back to Primary Power]
  D --> G[Alarm to Fire Safety Team]

Summary: NFPA 20 mandates an independent alternate power source capable of automatic start and continuous operation of fire pumps during primary power failure, ensuring fire safety system reliability.

NFPA 20 Key Data for Centrifugal Fire Pumps

1. Pump Capacities (Clause 4.10.2, Table 4.10.2)

2. Net Discharge Suction Pressure Calculation (Clause 29.83)

[ \text{Net Discharge Suction} = P_p - P_d - P_s ]

Where:

• ( P_p ) = Total pressure at pump discharge (psi)
• ( P_d ) = Total pressure at pump suction (psi)
• ( P_s ) = Velocity pressure adjustment (psi), calculated as: [ P_v = \frac{0.43352 V^2}{2g} = \frac{Q^2}{890.47 D^4} ]

Variables:

• ( Q ) = Flow rate (gpm)
• ( V ) = Velocity of liquid (ft/s)
• ( D ) = Internal pipe diameter (in)
• ( g ) = Gravitational constant (32.174 ft/s²)

3. Flow Through Circular Orifice

[ Q = c \times d^2 \times \sqrt{P} ] Where:

• (

NFPA 20 Key Points for Vertical Shaft Turbine-Type Pumps

1. Minimum Submergence & NPSH (Clause 3.05)

• Minimum submergence: 10 ft (3.05 m) at sea level.
• Elevation correction: Add 1 ft (0.30 m) per 1000 ft (305 m) elevation increase.
• Example: At 1000 ft elevation, submergence = 11 ft (3.35 m).
• Reason: To ensure adequate Net Positive Suction Head (NPSH) and avoid cavitation.

2. Lineshaft Lubrication (Clauses 4.3.1, A.4.3.1 to A.4.3.4.2)

• Bearings along the lineshaft require lubrication.
• Lubrication fluid is vegetable-based and approved by authorities.
• Supplied from aboveground reservoir via copper tubing or small pipes.
• Purpose: Maintain alignment and reduce wear.

3. Pump Performance Curves

• Steepest permissible head-capacity curve ensures stable operation.
• "Flat" head-capacity curve indicates constant head over varying flow.
• Use these curves to select pumps matching system requirements.

4. Motor Requirements (Clause 9.5.1.9)

• Motors must be suitable for vertical shaft turbine pumps.
• Typically designed for vertical mounting and variable speed operation.

5. Variable Speed Pumps (Clause 7.5.3)

• Variable speed drives allow flow and head adjustment.
• Improves efficiency and system control.

NPSH Correction Formula

[ \text{Required submergence} = 10 \text{ ft} + \left(\frac{\text{Elevation in ft}}{1000}\right) \times 1 \text{ ft} ]

Flowchart: Vertical Shaft Turbine Pump Selection

flowchart TD
  A[Start Pump Selection] --> B[Check Elevation]
  B --> C{Elevation > 0?}
  C -->|Yes| D[Calculate Submergence]
  C -->|No| E[Use 10 ft Submergence]
  D --> F[Check NPSH Available]
  E --> F
  F --> G{NPSH Ade

NFPA 20 - Positive Displacement Pumps: Key Points

Definitions & Types (Clauses 8.1.1, 14.2.6.6.3)

• Positive Displacement Pumps (PDP) deliver a fixed volume per cycle, suitable for low flow/high pressure.
• Types include gear, screw, piston, diaphragm pumps.

Suitability (Clause 8.1.2)

• PDPs are suitable when:
  • Flow rate is constant or nearly constant.
  • High discharge pressure is required.
  • Pumping viscous or shear-sensitive fluids.

Selection Guidance (Clause 8.1.2.2, FIGURE A.8.1.2.2)

• Selection depends on:
  • Required flow rate (Q).
  • Discharge pressure (P).
  • Fluid characteristics.
• Example flowchart for pump selection is provided in FIGURE A.8.1.2.2.

Key Formulas

• Flow rate, Q = V × N
  Where:
  V = volume per revolution (m³/rev)
  N = speed (rev/s)

• Power, P = (P_d × Q) / η
  Where:
  P_d = discharge pressure (Pa)
  Q = flow rate (m³/s)
  η = pump efficiency (decimal)

Specifications (Clause 14.5.1)

• Must comply with rated pressure and temperature.
• Include relief valves to prevent overpressure.
• Must be compatible with fire pump driver and system controls.

flowchart TD
  A[Start: Define Flow and Pressure] --> B{Is flow constant?}
  B -->|Yes| C{Is pressure high?}
  B -->|No| D[Consider Centrifugal Pump]
  C -->|Yes| E[Select Positive Displacement Pump]
  C -->|No| F[Consider Other Pump Types]

Summary: Use PDPs for steady flow, high pressure, and viscous fluids. Calculate flow by volume per revolution times speed, and power using pressure, flow, and efficiency. Follow NFPA 20 clauses for safety and compatibility.

NFPA 20: Electric Drive for Pumps - Key Specifications and Tables

1. General Requirements (Clause 9.1.2)

• Covers all intermediate equipment between power source and pump, including motors.
• Excludes electric fire pump controller, transfer switch, and accessories.

2. Part-Winding Motors (Clause 9.5.1.3)

• Must have a 50-50 winding ratio for equal currents in both windings at nominal speed.

3. Locked Rotor Current Tables

Table 9.5.1.1(b): Single-Phase Motors (115 V & 230 V, 60 Hz)

Locked rotor currents are maximum values.

Table 9.5.1.1(c): Three-Phase Motors (380 V, 50 Hz, NEMA Design B)

4. Variable Speed Controllers (Clause 9.5.1.4)

• Motors used with variable speed drives must comply with specific performance criteria (refer NFPA 20 for details).

5. Flow Measurement (Clause 8.10.3)

• Water pumping systems require a flowmeter or orifice plate in a test loop for performance verification.

Summary Flowchart: Electric Drive for Pumps Selection

flowchart

NFPA 20: Electric-Drive Controllers and Accessories - Key Points

1. Voltage Rating & Specifications

   • Controllers rated >600 V have distinct specs (Clause 10.6.6.1 vs. 10.4.6).
   • Must be marked with short-circuit current rating:

     "Suitable for use on a circuit capable of delivering not more than _ amperes RMS symmetrical at _ volts AC" (Clause 10.1.2.2.2).

2. Current Limits

   • Refer Clause 9.5.2 for max current limits to ensure safe operation.

3. Backup Controllers

   • Backup requirements detailed in Clause 9.3.3 to maintain reliability.

4. Electrical Diagrams & Instructions

   • Must comply with 12.3.6, 12.3.7.1, 12.3.8, and Annex A.12.3.8 for clear wiring and operation instructions.

5. Critical Path Components

   • Clause 14.5.2.5(3) highlights components crucial to system operation and monitoring.

6. External Operations & Transfer Switches

   • External control provisions: 12.3.6.3, 12.7.2.6.
   • Transfer switches must meet marking and rating requirements (Clause 10.1.2.2.2).

Typical Marking Format for Controllers (Clause 10.1.2.2.2):

Simplified Flowchart for Controller Selection & Marking

flowchart TD
  A[Start: Controller Voltage Rating] --> B{Voltage > 600V?}
  B -->|Yes| C[Apply Clause 10.6.6.1 Specs]
  B -->|No| D[Apply Clause 10.4.6 Specs]
  C --> E[Mark Controller with RMS Current and Voltage]
  D --> E
  E --> F[Check Current Limits (9.5.2)]
  F --> G{Backup Controller Needed?}
  G -->|Yes| H[Follow Clause 9.

NFPA 20 Key Points for Diesel Engine Drive (Chapter 11)

• Definition (3.3.18.1): Diesel engine is an internal combustion engine igniting fuel by heat from compressed air.

• Performance Requirements (11.1.1):

  • Diesel engines must meet minimum performance standards for fire pump drivers.
  • Include ramp up and ramp down times for water-lubricated pumps (10.10.12.5).

• Installation (14.2.6.6.7):

  • Engine-driven units must comply with NFPA 20 for reliability and operational readiness.

Key Specifications & Formulas

Diesel Engine Fire Pump Driver Selection

• Power (HP):
  [ HP = \frac{Q \times H \times \rho \times g}{\eta \times 550} ] where:

  • (Q) = Flow rate (cfs)
  • (H) = Total head (ft)
  • (\rho) = Density of water (lb/ft³)
  • (\eta) = Pump efficiency
  • 550 = Conversion factor (ft-lb/s to HP)

• Fuel Capacity:

  • Minimum 30 minutes continuous operation at full load.

flowchart TD
  A[Diesel Engine Drive] --> B[Performance Requirements]
  B --> C[Ramp Up / Ramp Down Times]
  B --> D[Minimum Power & Fuel Capacity]
  A --> E[Installation Requirements]
  E --> F[Starting System]
  E --> G[Cooling System]

Summary: NFPA 20 Chapter 11 mandates reliable diesel engine performance with controlled ramp times, sufficient fuel, and robust starting and cooling systems for fire pump operation.

NFPA 20 Engine Drive Controllers - Key Points

1. Responsibilities & Instructions

• Clause 11.6.6.2: Engine manufacturer must provide specific operating instructions for emergency use.

2. Controller Types & Requirements

• Chapter 12 covers engine drive controllers, including:
  • Variable speed pressure limiting control (4.7.7.3, 4.20.1.3)
  • Definitions (3.3.76.3)
  • Diesel engine controls (11.2.4.3)
  • Electric drive controllers (10.5.2.1.8.6, 10.10)
  • Engine drive controllers specifics (12.4.1.1 to 12.4.1.4, 12.4.2.1)

3. Electrical & Control Specifications

• Electrical diagrams and instructions must be provided (12.3.6 to 12.3.8).
• Current limits and critical path components are addressed (9.5.2, 14.5.2.5(3)).
• Rated motor voltage may differ from line voltage (B.1.31).

4. Table Reference

• Table C.9.2.10.1: Provides current limits for controllers (f) and (i).
• Backup electric-drive controllers covered in 9.3.3.

Example Formula for Current Limit (from Table C.9.2.10.1 simplified):

(Refer to NFPA 20 Table C.9.2.10.1 for detailed values)

Summary Flowchart: Engine Drive Controller Compliance

flowchart TD
  A[Start: Select Engine Drive Controller] --> B{Type of Drive?}
  B -->|Electric| C[Follow Chapter 10 Specs]
  B -->|Engine| D[Follow Chapter 12 Specs]
  C --> E[Check Current Limits per 9.5.2]
  D --> E
  E --> F{Manufacturer Instructions Provided?}
  F -->|Yes| G[Include in Emergency Operation Manual]

NFPA 20 Key Points for Steam Turbine Drive

• Speed Control (14.2.6.6.8):
  Steam turbine speed must be maintained within limits per Clause 13.2.2 (typically ±3% of rated speed).

• Ordering Data (13.1.2.3):
  Specify:

  • Rated and max pump loads at rated speed
  • Rated speed (rpm)
  • Boiler pressure
  • Steam pressure at turbine throttle
  • Steam superheat temperature

• Steam Consumption (13.1.3):
  Steam consumption depends on turbine efficiency and load; consult manufacturer data or typical values (e.g., 15-25 lb steam/hp-hr).

• Minimum Steam Pressure (13.1.2.1):
  For boiler pressure ≤120 psi (8.3 bar), turbine must run pump at rated speed and max load with as low as 80 psi (5.5 bar) steam at throttle, exhausting to atmosphere.

• Controller Action (12.8.3.2):
  Controller must return to full automatic after manual operation.

Typical Steam Turbine Drive Specs Summary

Steam Turbine Drive Concept Flowchart

flowchart TD
  A[Start: Specify Pump Load] --> B[Specify Rated Speed]
  B --> C[Specify Boiler Pressure]
  C --> D[Specify Steam Pressure at Throttle]
  D --> E[Ensure Min Steam Pressure ≥ 80 psi]
  E --> F[Design Turbine for Rated Speed and Load]
  F --> G[Maintain Speed within Limits (±3%)]
  G --> H[Controller Returns to Auto Mode]

This ensures NFPA 20 compliance for steam turbine-driven fire pumps.

NFPA 20: Acceptance Testing, Performance, and Maintenance - Key Points

1. Acceptance Testing (Clause 14.2)

• Manufacturer's Certified Pump Test Curve must be available for comparison.
• Field acceptance tests include:
  • Flush test (Table 14.1.1.1)
  • Hydrostatic test at specified pressure for 2 hours.
  • Presence of manufacturer and authority representatives.
  • Verification of electric wiring and controls.
• Use Centrifugal Fire Pump Acceptance Test Form (Fig. A.14.2.6.6(a)) for documentation.

2. Performance Testing

• Compare test results with certified pump curves.
• Record parameters at various load conditions:
  • Flow (Q)
  • Head (H)
  • Power (P)
  • Current (Amps)
• Ensure no vibration or overheating during tests.
• Calibrated gauges and test equipment mandatory.

3. Maintenance (Clause 14.5)

• Follow manufacturer recommendations for component replacement.
• Regular inspection of pump, driver, and controllers.
• Maintain records of performance and repairs.

Essential Formulas and Tables

Flowchart: Acceptance Testing Process

flowchart TD
  A[Start Acceptance Test] --> B{Flush Test Required?}
  B -->|Yes| C[Perform Flush Test]
  B -->|No| D[Proceed to Hydrostatic Test]
  C --> D
  D --> E[Conduct Hydrostatic Test at Specified Pressure]
  E --> F{Test Passed?}
  F -->|No| G[Fix Issues and Retest]
  F -->|Yes| H[Perform Pump Performance Test]
  H -->