Definition & Applications

A rubber expansion joint is an arch-type flexible non-metallic connector fabricated from natural or synthetic rubber and fabrics, usually with metal reinforcements, to isolate vibration and noise and provide stress relief in piping systems caused by thermal changes, mechanical vibration and other system movements. Generally, it shall be designed & fabricated in accordance with ASTM F1123 and “Technical Handbook on Rubber Expansion Joints and Flexible Pipe Connectors”, or in accordance with special customer requirements. Besides, the Chinese standard HG/T 2289 Flexible Rubber Joints sometimes may apply.

Rubber expansion joints provide flexibility and concurrent movements, isolation of vibration and noise, resistance to corrosion, abrasion and erosion in various piping systems. They are widely used in process piping systems, urban heating & air conditioning systems, water supply systems, sewage treatment, food industry, ship building industry, power generation, as well as pharmaceutical industry.

Construction Features
The 3-dimensional model of a spool arch type rubber expansion joint. The sectional view of the inner tube, carcass and cover.

Miscellaneous design patterns of rubber expansion joints are available: (1) Integral Rubber Flanges – The end connection flanges of the joint are integrally formed as a part of the elastomeric bellows. It is also called “spool arch type rubber expansion joint”. (2) Floating Metallic Flanges – The metal flanges shall have a groove to accept the molded bead in the body at each end of the expansion joint bellows. (3) Spherical Type – Long radius arch, either single sphere or twin sphere, to provide better movement capability and strength. (4) Control Units – Tie rods or control rods are provided to minimize possible damage to the expansion joint caused by excessive motion of the piping system. (5) Custom Designs – rectangular flange connection, threaded union connection, tapered reducer type, no-arch U type, hinged type, gimbal type, sleeve type, PTFE lined type.

Diagrammatic Drawing & Technical Parameter

DN		Length	Axial Displacement mm		Horizontal Displacement mm	Angular Deflection (a1+a2)°
mm	inch	mm	Extension	Compression
32	1.25	95	6	9	9	15
40	1.5	95	6	10	9	15
50	2	105	7	10	10	15
65	2.5	115	7	13	11	15
80	3	135	8	15	12	15
100	4	150	10	19	13	15
125	5	165	12	19	13	15
150	6	180	12	20	14	15
200	8	210	16	25	22	15
250	10	230	16	25	22	15
300	12	245	16	25	22	15
350	14	255	16	25	22	15
400	16	255	16	25	22	15
450	18	255	16	25	22	15
500	20	255	16	25	22	15
600	24	260	16	25	22	15
700	28	260	16	25	22	15
800	32	260	16	25	22	15
900	36	260	16	25	22	15
1000	40	260	18	26	24	15
1200	48	260	18	26	24	15
1400	56	350	20	28	26	15
1600	64	350	25	35	30	10

Working Principle

Production Process

(1) Compounding – Add necessary ingredients to rubber to form the elastomer that can meet service requirements.

(2) Mixing – It involves the mastication process and incorporation of additives. The rubber will become soft and tacky, and articles could be built up from multiple pieces of the masticated rubber.

(3) Forming of the joint body on a die mold.

(4) Vulcanization of the rubber joint to give the material its elastic recovery behaviour.

(5) Assembly – Install the rubber joint with end connector as well as control units.

(6) Inspection & Testing.

(7) Cleaning & Packaging.