I. Basic Parameters of DN250 Force Transfer Joint

Item Typical Parameters

Nominal Diameter (DN) 250mm (corresponding to 8-inch imperial)

Applicable Pipe OD 273mm (carbon steel seamless pipe)

Working Pressure 1.0MPa / 1.6MPa (common specifications)

Material Body: Q235 carbon steel; Sealing ring: EPDM rubber

Compensation Capacity Axial displacement ±10mm; Angular displacement ≤1.5°

Connection Mode Flange connection (compliant with GB/T 9115 standard)

II. Core Functions and Application Scenarios

Functional Principle:

Fix flanges to pipes via bolts, and use force transfer screws to transmit pipeline thrust to the entire system, preventing displacement, leakage or damage to the joint caused by medium pressure or thermal expansion/contraction.

Typical Scenarios:

Inlet/outlet of water pumps, valve connections (to eliminate vibration stress);

Long-distance water/gas transmission pipelines (to balance axial thrust);

Water supply and drainage systems in high-rise buildings (to resist water pressure impact).

III. Correct Installation Steps (Preventing Leakage and Stress Damage)

Pre-installation Preparation

Check integrity of components: flanges, sealing rings, force transfer screws, nuts, limit bolts, etc.;

Grind pipe end faces: remove burrs and welding slag to ensure flat flange sealing surfaces (roughness ≤12.5μm).

Positioning and Alignment

Axial position: The natural length of the joint should be consistent with the pipeline spacing, and forced stretching or compression is prohibited (allowable deviation ±3mm);

Flange parallelism: Use a feeler gauge to detect the spacing between two flanges, with a maximum deviation ≤1mm (DN200 standard).

Key Points for Bolt Installation

Bolt material: 8.8-grade galvanized bolts (corrosion-resistant), with length ensuring 2-3 threads exposed after nut tightening;

Tightening sequence: Tighten diagonally and crosswise (as shown), gradually reaching the rated torque in 3 steps (reference value: M20 bolt torque 180-220N·m).

Adjustment of Limit Devices

After installation, loosen the limit bolt nuts, reserve a 10mm axial clearance, then lock the lock nuts;

If system pressure >1.6MPa, install additional limit supports (spacing ≤3 times pipe diameter).

IV. Key Selection Parameters and Precautions

Medium Compatibility:

Water system: Select EPDM rubber sealing ring (temperature resistance -20℃~120℃);

Oil/acid-base media: Switch to NBR or fluororubber sealing rings (medium composition needs to be specified).

Temperature Difference Compensation Calculation:

Example: For a DN250 carbon steel pipeline with a temperature difference of 50℃, the thermal expansion amount ΔL=12×10⁻⁶×L×50 (L is pipeline length). If L=50m, ΔL=30mm, ensuring the force transfer joint is used in conjunction with a compensator.

Adaptation to Special Working Conditions:

Buried installation: Flanges need anti-corrosion treatment (such as epoxy resin coating) with additional protective casings;

Vibrating environment: Install spring washers at screw connections and check bolt tightness quarterly.

V. Common Failures and Solutions

Failure Phenomenon Possible Causes Solutions

Leakage at flange joint Aging sealing ring/loose bolts Replace sealing ring and retighten bolts according to torque standard

Abnormal pipeline vibration Force transfer screws not loosened/limit too tight Readjust limit clearance to 5-10mm

Joint deformation Overpressure operation/untreated temperature difference Install pressure safety valve and add bellows compensator

VI. Maintenance Specifications

Regular Inspection Cycles:

Within the first 3 months of operation: Check bolt torque monthly;

After normal operation: Inspect sealing ring aging condition semi-annually (replace if cracks >2mm).

Anti-corrosion Treatment:

For outdoor installation, paint flange surfaces with anti-rust paint every 1-2 years (iron red primer + aluminum powder topcoat);

For seawater environments: Switch to 316L stainless steel flanges and screws.

VII. Industry Standards and Selection References

Execution standard: GB/T 12465-2017 Loose Sleeve Expansion Joints for Pipeline;

Selection tool: Refer to the following table based on system pressure, medium temperature and installation method (overhead/buried):

Working Condition Type Recommended Model Additional Configurations

Municipal water supply/drainage VSSJAF(C2F) force transfer joint Anti-pull-off limit device

Thermal pipeline network VSSJA-2(B2F) double-flange force transfer joint High-temperature silicone sealing ring (temperature resistance 180℃)

Summary: The correct installation of DN200 force transfer joints requires balancing mechanical stress and sealing reliability, with special attention to bolt tightening sequence, limit clearance adjustment and medium compatibility. For complex working conditions (such as high pressure and high temperature), it is recommended to form a complete solution by combining with compensators, supports and other accessories to extend service life and avoid system failures.