Regarding specifications and management guidelines
Editorial supervision by Government Buildings Department, Minister’s Secretariat, Ministry of Land, Infrastructure, Transport and Tourism
“Machinery and Equipment Work Supervision Guidelines,” 2019 edition
2.2.9 Flexible joints ｐ.165～170
Table 2.2.6 Types of pipe joints
Based on SHSSE-S 008: 2008
|Cylindrical pipe joint||Category A||Cold water
Heat source water
|Flange shape||0~60||0.5※、1 or 2||20~600||Integral multiple of 50|
|Category B||0~70||20~300||Integral multiple of 50|
|Sphere type pipe joint||Category B||Manufacturer specifications|
|Bellows type pipe joint|
0.5MPa is compatible with drainage systems
Table 2.2.7 Types of pipe joints
Based on SHASE-S 008:2008
|Category A||100or more||Earthquake‐resistant
|Mainly absorbing sudden
and large displacement due to earthquakes
|Type designed to cope with ground subsidence||Mainly absorbing displacement due to ground subsidence
at building entry points where there is a risk of subsidence
|For seismic isolation||Mainly the absorption of displacement between seismically isolated buildings and the ground|
|Category B||Less than 100||Protecting equipment and
tanks in earthquakes
|Mainly absorbing displacement around tanks
and equipment such as pumps due to
equipment starting and stopping as well as
piping displacement due to earthquakes
（C）Synthetic rubber material（For water）
In the “Standards Specifications,” rubber displacement absorption pipe joints for use with water are specified as having a steel flange. In the SHASE-S 008: 2008 specifications (rubber displacement absorption pipe joints), pipe joints are divided into Category A and Category B based on the types and face‐to‐face dimensions shown in Table 2.2.6 and the range of maximum perpendicular displacement amounts shown in Table 2.2.7. The “Standards Specifications” show overall lengths for synthetic rubber flexible joints envisaging typical applications.
In addition, joints used in drinking water pipes shall present no hygiene issues nor adversely affect water quality.
It is preferable that EPDM with strengthened chlorine resistance is used on the rubber materials coming into contact with fluids in synthetic rubber flexible joints used in water supply systems where the residual chlorine concentration is high. (from Guidelines) In recent years, direct water supply systems (high residual chlorine concentration) have come to be used in typical buildings, and the chlorine concentration in tap water has also further increased.
Rubber degradation occurs due to the oxidative effect of oxygen in the air and dissolved in fluids. This effect is significantly reinforced by heat, residual chlorine, copper, and salts such as manganese. This oxidative effect causes the rubber surface to become brittle, and rubber to peel away due to liquid flow, vibration, etc.