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IS 937:1981 is the Indian Standard (BIS) for washers for water fittings for fire fighting purposes. This standard specifies the requirements for materials, dimensions, and testing of washers used in water fittings for fire fighting purposes. It ensures that critical components like hose couplings, branch pipes, and hydrants maintain leak-proof joints under high water pressure during emergencies.
Specification for Washers For Water Fittings For Fire Fighting Purposes
! Regular inspection and replacement of rubber washers is critical, as they tend to harden, crack, or perish over time, leading to dangerous leaks during fire emergencies.
! Ensure the washer dimensions precisely match the coupling sizes specified in IS 901 and IS 903 to guarantee a watertight seal.
rubberleathervulcanized fiber
International Equivalents
Similar International Standards
BS 336:2010BSI — British Standards Institution, UK
HighCurrent
Fire hose couplings and ancillary equipment
Specifies the same British Instantaneous type couplings, including washer dimensions and material requirements.
NFPA 1963:2019NFPA — National Fire Protection Association, USA
MediumCurrent
Standard for Fire Hose Connections
Covers gaskets for fire hose couplings, but for different (US-threaded) connection types.
DIN 14321:2013-09DIN — Deutsches Institut für Normung, Germany
LowCurrent
Storz couplings for fire fighting purposes - PN 16; Type C
Specifies gaskets for Storz couplings, a different lug-based system, but for the same general firefighting application.
EN 15182-1:2007+A1:2009CEN — European Committee for Standardization, Europe
MediumCurrent
Equipment for fire fighting services - Hoses with couplings - Part 1: General requirements
Sets performance requirements for hose assemblies, including sealing, referencing specific coupling standards.
Key Differences
≠IS 937:1981 is a dedicated standard solely for washers, whereas modern international standards like BS 336 and NFPA 1963 specify washers as a component within the broader standard for the entire coupling assembly.
≠IS 937 specifies leather as an acceptable material. Modern international standards have phased out leather in favor of advanced synthetic elastomers like EPDM, NBR, and silicone due to superior durability and performance consistency.
≠The Indian standard is based on the British Instantaneous coupling system, making its washers dimensionally incompatible with American (NFPA 1963, threaded NST) or German (DIN, Storz) coupling systems.
≠IS 937 is significantly older (1981) and its material testing requirements (e.g., tensile strength, elongation) are less stringent than those in current standards like BS 336:2010, which reference recent material-specific norms like BS EN 681-1.
Key Similarities
≈All standards aim to ensure a reliable, watertight seal in demountable connections for critical firefighting applications.
≈Both IS 937 and its direct equivalent BS 336 specify the same nominal dimensions (OD, ID, Thickness) for washers used in British Instantaneous type couplings, ensuring interchangeability within this system.
≈All standards mandate strict dimensional tolerances and specify key physical properties for the washer material, such as hardness and resistance to ageing, to guarantee proper fit and function.
≈The fundamental requirement for the washer to be made from a flexible, resilient, and durable material that can withstand pressure and environmental exposure is common across all standards.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Elastomeric Material
Natural rubber or synthetic rubber (e.g., Neoprene)
Elastomeric material compliant with BS EN 681-1, Type WA (e.g., EPDM)
BS 336:2010
Inclusion of Leather Washers
Yes, vegetable-tanned leather is a specified option.
No, leather is not specified and considered obsolete for this application.
BS 336:2010
Rubber Hardness
55 ± 5 IRHD
Compliance with BS EN 681-1, which specifies grades (e.g., 50 ± 5 IRHD is a common grade)
BS 336:2010
Minimum Tensile Strength (Rubber)
7.0 MPa
≥ 9.0 MPa (as per BS EN 681-1 for common grades)
BS 336:2010
Minimum Elongation at Break (Rubber)
300%
≥ 350% (as per BS EN 681-1 for common grades)
BS 336:2010
Dimensions for 63 mm Washer (OD x ID x Thk)
78 x 61 x 6.5 mm
78 x 61 x 6.5 mm (Nominal dimensions are identical)
BS 336:2010
Accelerated Ageing Test (Air Oven)
72h at 70 ± 1°C. Max change in hardness: +5 IRHD. Max change in tensile strength/elongation: -15% / -20%
7 days at 70 ± 2°C. Max change in hardness: -5 to +8 IRHD. Max change in elongation: -20% (as per BS EN 681-1)
BS 336:2010
⚠ Verify details from original standards before use
What materials are acceptable for washers in fire fittings?+
Washers are typically made from vulcanized natural or synthetic rubber, or specific grades of leather, depending on the application and joint type.
Which specific fire fighting water fittings do these washers apply to?+
They are designed for delivery hose couplings, suction hose couplings, branch pipes, nozzles, and hydrants.
Why is washer hardness specified?+
Hardness is strictly controlled so the washer compresses sufficiently to form a secure seal, but resists permanently deforming or blowing out under high operating water pressure.