Code of practice for design and construction of machine foundations, Part 4: Foundations for rotary type machines of low frequency

IS 2974 Part 4 – Scope & Key Specifications

Scope (Clause 4.1)

This part covers foundation design data for various heavy machines. The designer must obtain specific machine data from manufacturers:

Rounding Off (Clause 0.6)

• Final test/analysis values must be rounded per IS 2-1960.
• Retain significant figures equal to those in the standard’s specified values.

Minimum Reinforcement for Foundations (Clause 7.6)

Typical reinforcement layouts are shown in Figures 1 to 3 of the standard.

Summary

• Obtain detailed machine data for foundation design.
• Use IS 2-1960 for rounding test values.
• Follow specified minimum reinforcement for different foundation types.

flowchart TD
    A[Start: Machine Data Required] --> B{Machine Type}
    B -->|Crushing Mill| C[Get mass, speed, forces, anchor details]
    B -->|Pump| D[Get mass, speed, pressure freq, forces, anchor details]
    B -->|Motor Generator| E[Get mass, speed, short-circuit forces, anchor details]
    B -->|Rolling Mill| F[Get mass, torque, loads, anchor details]
    C & D & E & F --> G[Design foundation]
    G --> H[Apply minimum reinforcement per Clause 7.6]
    H --> I[Round off

IS 2974 Part 4 - Key References and Specifications

1. Notations

• Use Appendix A for all notations (Clause 3.1).

2. Necessary Data from Manufacturer (Clause 4.1)

• Crushing Mill:

  • Outline drawing with loading points
  • Anchor bolt and embedment details
  • Masses (crusher parts, motor drive)
  • Shaft speed and unbalanced forces

• Pump:

  • Mass, anchor bolts, pressure frequency
  • Pump speed, unbalanced forces, impeller vane count

• Motor Generators:

  • Outline, masses (motor, generator, rotors, flywheel)
  • Anchor bolts, operating speed, short-circuit forces

• Rolling Mills:

  • Masses (stands, motor, rotor, stator)
  • Maximum torque, assembly line loads, anchor bolts

3. Minimum Reinforcement (Clause 7.6)

4. Typical Reinforcement Layouts

• Refer to Fig. 1 to 3 for reinforcement details of crushing mill, primary air fan, and instrument air compressor foundations.

flowchart TD
    A[Manufacturer Data] --> B[Design Inputs]
    B --> C{Machine Type}
    C -->|Crushing Mill| D[Load, Mass, Speed, Forces]
    C -->|Pump| E[Mass, Speed, Pressure Frequency]
    C -->|Motor Generator| F[Mass, Speed, Short Circuit Forces]
    C -->|Rolling Mill| G[Mass, Torque, Loads]
    D & E & F & G --> H[Foundation Design]
    H --> I[Minimum Reinforcement]

This summary aligns with IS 2974 Part 4 (1979) requirements for machine foundation design inputs and reinforcement specifications.

IS 2974 Part 4 - Notations & Key Specifications

• Reference for Notations:
  Clause 3.1 states that all notations used are as per Appendix A of IS 2974 Part 4 and definitions from related parts (I, II, III) and IS 2810-1979 apply.

• Key Data to be Obtained from Manufacturer (Clause 4.1):
  For design guidance, obtain:

  • Masses of machine parts (rotors, motors, flywheels)
  • Operating speeds and unbalanced forces
  • Details of anchor bolts, embedments, channels
  • Specific machine data (torques, pressure frequencies, load points)

• Rounding Off Numerical Values:
  Use IS 2-1960 for rounding off results, retaining significant places equal to those specified in the standard.

Typical Notations (from IS 2974 series, Appendix A)

Summary Diagram of Data Flow for Design

flowchart TD
    A[Manufacturer Data] --> B[Machine Masses & Speeds]
    A --> C[Unbalanced Forces & Torques]
    A --> D[Anchor Bolt & Embedment Details]
    B & C & D --> E[Foundation Design Calculations]
    E --> F[Rounded Off Values (IS 2-1960)]

Use IS 2974 (Parts I-IV) collectively for detailed formulas and tables on dynamic forces, foundation dimensions, and reinforcement. This part focuses on data acquisition and notation standardization for machine foundation design.

IS 2974 Part 4 — Necessary Data for Machine Foundations

1. Data to Obtain from Manufacturer (Clause 4.1)

2. Load Considerations (Clause 6.2.1.1)

• Loads to consider:
  • Constructional loads
  • Machine self-weight load × 5
  • Generating force due to unbalanced mass forces

3. Key Formula for Gyratory Crusher (Steep Cone)

[ R = (m_i r_1 - m_a r_2) \omega^2 ]

• (P_x = R \sin \omega t)
• (P_y = R \cos \omega t)

Where:

• (m_i, m_a) = masses
• (r_1, r_2) = radii
• (\omega) = angular velocity

4. Table: Generating Force (P_0) for Crushers

IS 2974 Part 4: Design Criteria Key Points

1. Design Loads (Clause 6.2.1.1)

• Constructional loads
• Machine load × 5
• Generating force due to unbalanced mass forces

2. Generating Force Formulas

Gyratory Crusher with Steep Cone:

[ R = (m_{it1} - m_{ar2}) \omega^2 ] [ P_x = R \sin \omega t, \quad P_y = R \cos \omega t ]

Gyratory Crusher with Flat Cone & Jaw Crusher:

• Force (P = P_0 \sin \omega t)
• (P_0) from table below:

• For different speeds (N_1): [ P_0 = P \times \left(\frac{N_1}{N}\right)^2 ]

3. Other Crushers:

• Roll crusher: Use manufacturer’s force data.
• Hammer crusher: Calculate unbalanced forces for:
  • Max wear (e = 1 mm)
  • Normal balance × 4 (for design)
  • Catastrophic hammer breakage

4. Seismic Consideration (Clause 5.5.3)

• Allowable soil stress may be increased per IS 1893 when seismic forces apply.

Summary Diagram: Load Components on Foundation

graph LR
A[Machine Load × 5] --> F[Foundation Design]
B[Construction Loads

IS 2974 Part 4: Principles of Design (Clause 6)

Key Loads to Consider (Clause 6.2.1.1)

• a) Constructional loads
• b) Machine load × 5
• c) Generating force due to unbalanced mass forces

Generating Force Formulas

1. Gyratory crusher with steep cone:

[ R = (m_i r_1 - m_a r_2) \omega^2 ]

[ P_x = R \sin \omega t, \quad P_y = R \cos \omega t ]

• (m_i, m_a): masses, (r_1, r_2): radius, (\omega): angular velocity

2. Gyratory crusher with flat cone and jaw crusher:

[ P = P_0 \sin \omega t ]

• (P_0) values from table below (tonnes):

• For different speeds (N_1):

[ P_0 = P \left(\frac{N_1}{N}\right)^2 ]

Additional Design Data (Clause 4.1)

• Masses of crusher parts, motors, rotors
• Speed and unbalanced forces
• Details of anchor bolts and embedments
• For pumps, motor generators, rolling mills: mass, speed, torque, unbalanced forces, and embedment details

Notes

• For roll crushers, use manufacturer data.
• For hammer crushers, consider max

IS 2974 Part 4: Materials and Construction Key Points

1. Minimum Reinforcement (Clause 7.6)

• Block foundation: 25 kg/m³ concrete
• Frame foundation:
  • Base slab: 40 kg/m³
  • Columns: 70 kg/m³
  • Top table: 90 kg/m³

Typical reinforcement layouts are shown in Figures 1 to 3 (refer IS 2974 Part 4).

2. Concrete Grade & Dynamic Elastic Modulus (Clause 5.5.1)

• Use M15 or higher concrete for foundations.
• Follow IS 456-1978 for concrete and steel stresses.
• Consider dynamic loads separately.

3. Data Required for Design (Clause 4.1)

For machine foundations, obtain:

• Outline drawings and loading points
• Details of anchor bolts and embedments
• Masses of machine parts (rotors, motors, flywheels)
• Operating speeds and unbalanced forces
• Specific machine data (e.g., torque, pressure frequency)

Summary Diagram of Reinforcement Quantities:

graph TD
  A[Foundations] --> B[Block Foundation: 25 kg/m³]
  A --> C[Frame Foundation]
  C --> D[Base Slab: 40 kg/m³]
  C --> E[Columns: 70 kg/m³]
  C --> F[Top Table: 90 kg/m³]

References: IS 2974 Part 4 (1979), IS 456-1978.

IS 2974 Part 4: Subsurface Investigation Key Points

1. Depth of Investigation (Clause 4.2.2a)

• Investigate soil profile up to 3 times the foundation width from the base or until hard strata is reached (whichever is less).
• Soil characteristics per IS 1892-1979 (Code of Practice for Soil Investigation).

2. Dynamic Soil Properties (Clause 4.2.2b)

• Conduct dynamic soil tests as per IS 5249-1977 to determine soil behavior under dynamic loads (e.g., seismic).

3. Water Table (Clause 4.2.2c)

• Record water table levels at different times of the year to assess seasonal variations.

4. Allowable Soil Stress (Clause 5.5.3)

• For seismic design, allowable soil stress may be increased following IS 1893-1975 guidelines.

Summary Table: Subsurface Investigation Requirements

flowchart LR
    A[Start Soil Investigation] --> B[Determine Foundation Width]
    B --> C[Excavate/Probe up to 3× Width or Hard Strata]
    C --> D[Collect Soil Samples & Test (IS 1892)]
    D --> E[Conduct Dynamic Tests (IS 5249)]
    E --> F[Record Water Table Levels Seasonally]
    F --> G[Analyze Data for Design]
    G --> H[Apply Allowable Stress (IS 1893 for seismic)]
    H --> I[

IS 2974 Part 4: Loads and Load Considerations

Key Loads to Consider (Clauses 6.1, 6.2.1.1, 6.2.2.1, 6.2.3.1)

• Dead Loads (6.1):

  • Mass of foundation & supported structure
  • Mass of mechanical equipment including rotating parts

• Constructional Loads (6.2.1.1, 6.2.2.1, 6.2.3.1):

  • Applied during erection/construction

• Machine Loads:

  • Multiply machine mass by 3 (Clause 6.2.2.1)
  • Multiply machine load by 5 (Clause 6.2.1.1)
  • Multiply machine load by 2 dynamic factor (Clause 6.2.3.1)

• Unbalanced Forces:

  • For gyratory crushers (steep cone): [ R = (m_i t_1 - m_a r_2) \omega^2 ] [ P_x = R \sin \omega t, \quad P_y = R \cos \omega t ]
  • For gyratory crushers (flat cone) and jaw crushers, refer to the table below for P₀ (generating force):

• For speeds different from N, adjust (P_0) as: [ P_0 = P \left(\frac{N_1}{N}\right)^2 ]

• **Torque Load (6.2.3.1

IS 2974 Part 4: Dynamic Analysis & Permissible Amplitudes Summary

1. Dynamic Analysis (Clauses 6.2.1.2 & 6.2.3.2)

• Follow IS 2974 Part I (1969) for dynamic response checks of block foundations.
• For hammer crushers and tube mills, use IS 2974 Part III (1975).
• Tube mills: No dynamic analysis needed; soil stresses based on:
  • Dead mass of foundation
  • Mass of machinery
  • Horizontal centrifugal force ( P_n ):
    • Short drum: 10% of mill mass (excluding ball charge/material)
    • Long drum: 20% of mill mass

2. Permissible Amplitudes of Vibration (Clauses 5.4, 5.4.1, 6.2.3.2)

3. Eccentricity Assumptions for Hammer Crushers

4. Key Notes

• Amplitudes are displacement limits to avoid resonance and structural damage.
• Dynamic forces and eccentricities influence foundation design and safety checks.
• Use supplier data if available; otherwise, adopt above guidelines.

flowchart TD
    A[Machine Type & Speed] --> B{Dynamic Analysis}
    B -->|Rotary Machines| C[IS 2974 Part I]
    B -->|Hammer Crushers| D[IS 2974 Part III

Vibration Isolation per IS 2974 Part 4 (1979)

Key Clauses & Specifications:

• Clause 5.1.1:
  Isolation between machine foundation and adjoining structures is essential to prevent vibration transmission.

  • Common method: Provide a sand trench around foundation block.
  • Thickness and depth: Determined case-by-case.
  • Foundation must not support unrelated structures/machinery.

• Clause 5.4.1 & 5.4.2:

  • Permissible amplitude of vibration at foundation top edge: ≤ 0.20 mm (to avoid resonance).
  • When multiple similar machine foundations share a common mat, treat each foundation independently by dividing the raft.
  • Permissible amplitude may be increased by 30% for such cases.

• Clause 6.2.3.2 (Dynamic Analysis):

  • Follow IS 2974 Part 1 (1969) for dynamic response.
  • Permissible vibration displacement amplitudes:

• Lower values are recommended for safety.

Additional Notes:

• Static loads (e.g., mill motor 3T, mill gear box 8T) must include allowances for live conditions.
• Consider 60% of static load as weight of rotating parts for dynamic analysis.

Summary Table: Permissible Vibration Amplitudes

Conceptual Diagram of Isolation

graph TD
    A[Machine Foundation] -->|Vibration| B[Sand Trench Isolation]
    B -->|Reduced

IS 2974 Part 4: Reinforcement Requirements for Machine Foundations

Key Specifications (Clause 7.6, 7.5 & 7.8)

• Minimum bar diameter: 12 mm
• Maximum bar spacing: 200 mm (to control shrinkage cracks)
• Reinforcement: Top and bottom two-way for all units except block foundations (surface only).

Typical Reinforcement Arrangement

• Refer Figures 1, 2, and 3 in IS 2974 Part 4 for layout of bars in block, base slab, and frame foundations.

Summary Formula for Minimum Reinforcement Weight:

[ W_{min} = \rho_{min} \times V_{concrete} ] Where:

• ( \rho_{min} ) = minimum reinforcement ratio (kg/m³) from table above
• ( V_{concrete} ) = volume of concrete in m³

flowchart TD
    A[Foundation Type] -->|Block| B[Min Reinforcement = 25 kg/m³]
    A -->|Frame Base Slab| C[Min Reinforcement = 40 kg/m³]
    A -->|Frame Columns| D[Min Reinforcement = 70 kg/m³]
    A -->|Frame Top Table| E[Min Reinforcement = 90 kg/m³]
    B & C & D & E --> F[Bar Diameter ≥ 12 mm]
    F --> G[Max Spacing ≤ 200 mm]

This ensures adequate crack control and structural integrity as per IS 2974 Part 4.

Key Formulas, Tables & Specifications from IS 2974 Part 4 for Specific Machines

1. Crushing Mills (Clause 6.2.1 & 6.2.1.1)

• Loads to consider:

  • Constructional loads
  • Machine self-weight × 5
  • Unbalanced mass forces (generating force)

• Generating force for gyratory crusher with steep cone:

[ R = (m_i t_1 - m_a r_2) \omega^2 \ P_x = R \sin \omega t \ P_y = R \cos \omega t ]

• For gyratory crusher with flat cone and jaw crusher:

• Adjusting (P_0) for speed (N_1):

[ P_0 = P \times \left(\frac{N_1}{N}\right)^2 ]

• Hammer crusher unbalanced forces:
  • Max unbalance due to wear (e=1 mm)
  • Normal balancing × 4 (design)
  • Catastrophic hammer breakage

2. Rolling Mills (Clause 6.2.4.2)

• Loads to consider:

  • Mass of rolling mill stands and motor
  • Maximum torque on shaft
  • Loads from assembly line and manipulations
  • Erection loads

• Dynamic load factors:

  • Use dynamic coefficient = 2 for rolling mill mass and motor
  • Actual values for max disconnecting moment and horizontal forces
  • Horizontal impact forces: design for double

IS 2974 Part 4 – Construction Joints and Grouting Key Points

Construction Joints (Clause 7.12)

• Joint plane: Horizontal only.
• Reinforcement: Must be continuous across the joint.
• Surface preparation: Roughen, clean, and wash with water jet before new concrete.
• Grouting: Apply a 20 mm thick rich cement grout (1:2 mix) on the prepared surface.
• Timing: Place new concrete within 2 hours of grout application.

Grouting (Clauses 7.4 & 7.3)

• Surface prep: Clean and roughen foundation surfaces before grouting.
• Grout type: Use non-shrink cement grout or grout with non-shrink additives where structural bonding is critical.
• Continuous concreting: Preferred to minimize joints; leave provisions for grouting as per 7.12.

Concrete Consistency (Clause 7.2)

• Slump: 50 to 80 mm.
• Water-cement ratio: ≤ 0.45.
• Consistency: Maintain uniform plastic consistency throughout concreting.

Typical Grout Mix for Construction Joint

Summary Diagram of Construction Joint Preparation

flowchart TD
    A[Existing Concrete Layer] --> B[Surface Roughening & Cleaning]
    B --> C[Water Jet Washing]
    C --> D[Apply 20mm Cement Grout (1:2)]
    D --> E[Place New Concrete Layer within 2 hours]

This ensures proper bond, continuity, and durability at construction joints and grouted surfaces in machine foundations.

Coordination Among Engineering Disciplines (IS 2974 Part 4)

• Key Concept: Effective teamwork among civil, mechanical, electrical, and foundation engineers is vital for rotary machine foundation design to ensure performance, operation convenience, economy, and aesthetics.

Important Notations (Appendix A, Clause 3.1)

Coordination Guidelines:

• Share dynamic forces (R, P, Px, Py) and mass/inertia data (m1, m2, I) between mechanical and foundation engineers.
• Civil engineers use soil stress (Omr), foundation weight (Q), and area (F) to design foundation size and reinforcement.
• Mechanical engineers provide rotational speeds (N), torque (M), and eccentricities (e) for dynamic load analysis.
• Electrical engineers coordinate on vibration frequencies (f) and machine operation parameters.

Key Formula Example: Unbalanced Force

[ P = m \times e \times W^2 ]

Where:

• (m) = mass (t·s²/m)
• (e) = eccentricity (m)
• (W = \frac{2\pi N}{60}) angular frequency (rad/s