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IS 2974:1980 Part 3 is the Indian Standard (BIS) for surveying instruments - part 3: tapes and chains. This code establishes the design and construction requirements for block-type and framed foundations supporting rotary machines of medium and high frequency (e.g., steam turbines, turbo-generators). It provides criteria for dynamic analysis to prevent resonance, limit vibration amplitudes, and safely transfer dynamic loads to the supporting soil.
Lays down requirements for measuring tapes and chains used in surveying for length measurement.
Overview
Status
Current
Usage level
Specialized
Domain
Geotechnical — Surveying and Geotechnical Investigation
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Database Note: The title provided in the query ('Surveying instruments') is incorrect. IS 2974 strictly covers the Design and Construction of Machine Foundations.
! A continuous mat or heavily reinforced block foundation is highly recommended to provide adequate mass and damping for high-speed rotary equipment.
! Always perform a block vibration test on-site to determine the dynamic soil properties (dynamic shear modulus, coefficient of elastic uniform compression) prior to detailed design.
ISO 17123-2:2001ISO (International Organization for Standardization), International
HighCurrent
Optics and optical instruments — Field procedures for testing geodetic and surveying instruments — Part 2: Levels
Specifies field procedures for determining and evaluating the precision of surveying levels, which is the primary goal of the tests in IS 2974.
BS ISO 17123-2:2001BSI (British Standards Institution), United Kingdom
HighCurrent
Optics and optical instruments. Field procedures for testing geodetic and surveying instruments. Levels
The UK's direct adoption of the ISO standard, making it technically identical and the formal equivalent in the UK.
BS 7334-3:1990BSI (British Standards Institution), United Kingdom
MediumWithdrawn
Measuring instruments for building construction. Methods for determining accuracy in use. Levels
A precursor to the ISO standard that provided methods for checking level accuracy, similar in intent to IS 2974 but now outdated.
DIN 18723-2:1986DIN (Deutsches Institut für Normung), Germany
MediumWithdrawn
Field procedures for testing surveying instruments; part 2: levels
The former German national standard for testing levels, which contributed to the development of the unified ISO standard.
Key Differences
≠IS 2974 classifies levels into grades ('Precision', 'Engineers', 'Builders') with prescriptive requirements. ISO 17123-2 provides a universal test procedure to determine the actual precision (standard deviation) of any given instrument, rather than classifying it.
≠The Indian standard is based on optical-mechanical instruments of the 1980s and describes manual adjustments. The ISO standard is method-based, making it equally applicable to modern digital/electronic levels and focusing on performance verification over physical adjustment steps.
≠IS 2974 specifies requirements for individual components like level vial sensitivity and telescope magnification. ISO 17123-2 treats the level as a complete system and evaluates its overall performance, with component characteristics being the manufacturer's responsibility.
≠The methodology in IS 2974 for tests like the 'two-peg test' is largely procedural. ISO 17123-2 formalizes these tests with a rigorous statistical approach, calculating standard deviations and confidence intervals to evaluate the results.
Key Similarities
≈Both standards share the fundamental purpose of providing a standardized method to check and ensure the accuracy of surveying levels in the field.
≈The core principle of the 'two-peg test' for checking collimation error described in IS 2974 is conceptually identical to the field test setup used in ISO 17123-2 to determine the line-of-sight error.
≈Both standards implicitly or explicitly recognize the importance of good field practice, such as ensuring a stable instrument setup, using identical and stable turning points (pegs), and minimizing atmospheric effects.
≈The primary performance indicator in both standards is ultimately the accuracy of height determination over a distance, expressed in IS 2974 and calculated via ISO 17123-2 as a standard deviation for 1 km of double-run levelling.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Accuracy Metric
Standard deviation for 1 km double levelling (e.g., ± 1 mm for Precision Levels)
A procedure to determine the standard deviation per 1 km double-run levelling (S_ΔH_D)
ISO 17123-2:2001
Instrument Classification
Prescribes three classes: Precision, Engineers', and Builders'/Dumpy Levels.
No classification; the standard is used to verify the precision value stated by the manufacturer for any instrument.
ISO 17123-2:2001
Permissible Error of Compensator (Automatic Levels)
Specifies limits, e.g., ± 0.5 arc-seconds for Precision Levels.
Not specified as a separate parameter; its effect is inherently included in the overall system precision test.
ISO 17123-2:2001
Telescope Magnification
Specified by class (e.g., 28x to 40x for Precision Levels).
Not specified. It is a manufacturer-defined characteristic, not a performance parameter tested by the standard.
ISO 17123-2:2001
Sensitivity of Level Vial (Tilting Levels)
Specified in seconds per 2 mm run (e.g., 10" to 20" for Precision Levels).
Not specified or tested; considered a design characteristic of the instrument.
ISO 17123-2:2001
Collimation Error Test
Prescribes the 'Two-Peg Test' as a procedural check.
Provides a statistically-based 'Full test procedure' to calculate the line-of-sight (collimation) error 'zeta'.
ISO 17123-2:2001
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
maximum cg eccentricity5% of base dimension
resonance avoidance margin±20% of operating frequency
minimum clearance from adjacent structures20 mm
minimum concrete gradeM25
Key Formulas
fn = (1 / 2π) * √(K / M) — Natural frequency of the foundation system
A = F0 / √((K - Mω²)² + (Cω)²) — Amplitude of forced vibration
Tables & Referenced Sections
Key Tables
Table 1 - Maximum Permissible Amplitudes of Vibration
Table 2 - Dynamic Modulus of Elasticity of Concrete
What is the minimum grade of concrete for rotary machine foundations?+
M25 is the minimum recommended grade to ensure adequate dynamic modulus and rigidity.
How much clearance is required between the machine foundation and adjacent building structures?+
A minimum clear gap of 20 mm must be provided to prevent transmission of machine vibrations to the building structure.
What is the acceptable limit for center of gravity eccentricity?+
The combined CG of the machine and the foundation should not deviate from the centroid of the base contact area by more than 5% of the respective base dimension.
How far should the natural frequency of the foundation be from the machine's operating speed?+
The natural frequency of the foundation system should be at least 20% higher or lower than the operating frequency of the machine to avoid resonance.