Difference Between Full face Rubber Expansion Joint and Grooved Rubber Expansion Joint (Performance & Application)

1. Structural Differences

1.1 Grooved Rubber Expansion Joint (Standard KXT Type)

It is the most common and conventional type on the market. Both ends of the rubber sphere are designed with concave annular grooves, where the inner ring of the metal flange is embedded and locked in place.

The sealing surface is narrow with only a circle of sealing belt at the groove. Bolts compress the edge of the rubber groove directly, and the bolt holes are not covered by rubber. The end face of the metal flange is partially exposed to the medium side.

Featuring simple vulcanization process and low rubber consumption, it is the mainstream structure for standard single-sphere rubber joints.

1.2 Full Flanged Rubber Expansion Joint (Full Face Seal Type)

Also known as full-face sealed rubber expansion joint, it is an upgraded reinforced type. The rubber body is integrally flanged outward at both ends, forming a complete wide rubber plane with the same outer diameter as the flange.

The full flanged rubber completely covers the flange outer edge and all bolt holes, with no exposed metal flange contacting the medium, achieving an overall flat sealing effect.

Adopting integral mold vulcanization technology, it consumes more rubber materials with higher manufacturing precision and stricter craftsmanship.

2. Performance Differences

2.1 Sealing Performance

• Grooved Type: Line contact narrow sealing structure. It is prone to local detachment and leakage under pressure fluctuation and pipeline stretching. Slight unevenness of flanges or irregular gasket installation will cause liquid and gas leakage. Long-term bolt extrusion easily crushes and ages the rubber edge.

• Full Flanged Type: Surface contact double sealing structure. The sealing area is more than 3 times that of the grooved type. It achieves superior self-sealing effect under high pressure. It can adapt to slightly uneven flange surfaces and effectively prevent leakage, suitable for medium with particles and corrosive fluids.

2.2 Anti-pull-off & Tensile Resistance (Core Advantage)

• Grooved Type: Fixed only by groove engagement. Under axial pipeline tension, water hammer impact and foundation settlement, the rubber sphere is easy to separate from the flange groove under high pressure. Limit tie rods are mandatory for large-diameter and high-lift water pump pipelines.

• Full Flanged Type: The entire flanged surface is tightly pressed with uniform force distribution, featuring natural anti-pull-off performance. It allows larger axial displacement and effectively resists water hammer and negative pressure impact. No additional limit accessories are required for long-distance pipeline operation, greatly reducing pipe burst risks.

2.3 Pressure Resistance Grade

• Grooved Type: Standard pressure PN6/PN10, maximum PN16 for reinforced type. Vulnerable to sealing failure caused by instantaneous water hammer.

• Full Flanged Type: Standard pressure PN10/PN16; steel wire reinforced type can reach PN25~PN40. Applicable for high-pressure chemical pipelines, fire protection systems and power plant cooling pipelines.

2.4 Erosion & Corrosion Resistance

• Grooved Type: Step structure at the groove causes sedimentation and scouring of slurry, sediment and granular media, accelerating rubber aging. Exposed metal flanges are prone to electrochemical corrosion and medium erosion.

• Full Flanged Type: Smooth inner wall without steps, avoiding dirt accumulation and medium scouring. Rubber completely isolates metal flanges from corrosive media such as acid, alkali and seawater, extending service life by more than 30%.

2.5 Displacement Compensation Capacity

• The grooved joint is prone to unilateral stress and groove detachment under large lateral and angular displacement, with limited allowable offset.

The full flanged joint adopts flexible overall rubber structure, with stronger adaptability to flange misalignment, foundation settlement and equipment installation deviation, and more stable multi-directional displacement compensation performance.

2.6 Installation & Maintenance Cost

• Grooved Type: Low unit price, sufficient stock and light weight with convenient installation. However, it has high requirements for flange flatness and uniform bolt tightening, and additional limit rods are required for vibration and high-pressure working conditions, increasing auxiliary costs.

• Full Flanged Type: Higher cost than grooved type, heavier and more difficult for large-diameter hoisting. But it requires no subsequent limit accessories, with extremely low leakage and pull-off failure rate, saving long-term operation and maintenance costs.

2.7 Vibration Damping & Noise Reduction

Both types have basic shock absorption performance. The full flanged joint has a larger flexible contact surface, providing better vibration isolation and noise reduction effect for high-frequency water pumps and air compressors.

3. Application Scenarios

3.1 Grooved Rubber Expansion Joint (General Purpose)

1. Low-pressure normal-temperature water supply and drainage, central conditioning chilled water and conventional fire protection pipelines (preferred for small diameter DN50 and below)

2. Civil building pipe networks with stable pressure, no severe water hammer and no obvious foundation settlement

3. Low-budget and short-term pipeline projects with clean water and air medium

4. Small-flow fans and small water pump pipelines with low pipeline tension

3.2 Full Flanged Rubber Expansion Joint (High-performance Heavy-duty)

1. High-pressure pipelines, high-rise water supply, long-distance water transmission and main pump station pipelines

2. Chemical acid-base medium, seawater, desulfurization slurry and mineral slag water pipelines with particles

3. Negative pressure pipelines and pump/compressor outlet pipelines with frequent start-stop impact and severe water hammer

4. Large-diameter pipelines above DN300, pipe networks with easy foundation settlement and flange misalignment

5. Process pipelines with zero leakage requirements for flammable, explosive and toxic media

6. Narrow pipe gallery and equipment spaces where limit rods cannot be installed

4. Quick Selection Guide

1. Low pressure, small diameter, clean medium and budget-limited projects → Grooved Rubber Expansion Joint

2. High pressure, large diameter, corrosive/slurry medium, zero leakage requirement and long-term stable operation → Full Flanged Rubber Expansion Joint