Product Model Confirmation
- Verify the specifications of the limit expansion joint (e.g., DN100-DN1200), working pressure (1.0MPa/1.6MPa/2.5MPa), compensation range (axial ±15mm~±50mm), and applicable media (water, steam, oil, etc.) to ensure consistency with pipeline system design requirements.
- Inspect the product certificate and test report, ensuring that limit bolts, flanges, seals, and other components are intact without damage.
Pipeline Pretreatment
- Clean welding slag, burrs, and oil stains from pipeline interfaces to ensure flat flange sealing surfaces without radial scratches (roughness ≤Ra12.5μm).
- When welding pipelines, avoid generating excessive stress near the expansion joint; it is recommended to reserve an installation spacing of 200~300mm.
Positioning and Leveling
- Place the expansion joint on the pipeline centerline, calibrate verticality with a level (deviation ≤1mm/m) to prevent uneven force caused by tilting.
- For overhead pipelines, install fixed supports within 1m on both sides of the expansion joint to prevent excessive displacement; for buried installation, add a concrete protection well.
Flange Connection Specifications
- Use matching flanges (PN10/PN16), and ensure bolt materials are compatible with the medium (e.g., 304 stainless steel for corrosive media).
- Tighten bolts diagonally and uniformly, with torque controlled at 80~120N·m (for DN200 as an example), ensuring the sealing gasket (NBR or PTFE) is evenly pressed without offset.
Adjustment of Limit Devices
- Loosen the limit bolt nuts before installation to keep the expansion joint in a natural extended state. After the pipeline system is installed, adjust the tightness of the limit bolts according to the designed compensation amount.
- Example: When the designed allowable axial displacement is +20mm, reserve a 20mm clearance for the limit bolt and fix it with a lock nut to prevent loosening during operation.
| Application Scenario | Installation Key Points | Risk Avoidance Measures |
|---|
| High-temperature Steam Pipelines | Select heat-resistant sealing materials (e.g., graphite wound gaskets), and install thermal insulation layers (thickness ≥50mm) on the outer side of the expansion joint to prevent rubber parts from aging. | Regularly inspect the integrity of thermal insulation to avoid local overheating causing sealing failure. |
| Connection to Vibrating Equipment | Install anti-vibration supports on both sides of the expansion joint, and add spring washers to limit bolts to absorb high-frequency vibrations from pumps, fans, etc. | Tighten bolts quarterly and check whether limit devices are loose. |
| Buried Pipelines | Use anti-corrosion expansion joints (galvanized flanges or rubber lining). After installation, backfill fine sand 100mm above the flange surface to prevent soil settlement from squeezing. | Perform an airtightness test before burying (0.6MPa air pressure test, hold for 30min without leakage). |
- Forbidden Forced Installation: Strictly prohibit compensating for pipeline installation errors by stretching or compressing the expansion joint (allowable deviation ≤3mm/m), as this may cause overload fracture of the limit structure.
- Medium Flow Direction Marking: Pay attention to the medium flow direction arrow on the expansion joint to ensure consistency with the medium flow direction in the pipeline, avoiding reverse installation that causes sealing failure.
- Temperature Difference Compensation: When the temperature difference between the installation environment and the design temperature exceeds 30℃, pre-adjust the initial position of the expansion joint according to the formula ΔL=α·L·ΔT (α is the linear expansion coefficient of the pipe material).
- Welding Protection: Wrap the expansion joint flanges with a damp cloth during pipeline welding to prevent welding slag from splashing and scalding the sealing surface. Clean residual welding slag after welding.
Pressure Testing
- Pressurize the system to 1.5 times the working pressure (hold for 30min), inspect all interfaces of the expansion joint for no leakage, and ensure the limit device is free from deformation; vacuum systems need to conduct a negative pressure test (-0.08MPa, hold for 1h).
Operation Monitoring
- During initial operation, check the torque attenuation of limit bolts every 2 hours, and retighten the bolts after 72 hours of operation; regularly record the displacement of the expansion joint (recommended monthly), and adjust the limit device in a timely manner when the displacement exceeds 80% of the design value.
Maintenance Cycle
- Inspect the aging degree of sealing gaskets every six months, and apply anti-corrosion treatment to flange bolts annually (brush molybdenum disulfide grease). For corrosive medium environments, shorten the maintenance cycle to 3 months.
By strictly following the above installation specifications, the limit expansion joint can effectively compensate for pipeline thermal displacement, absorb vibrations, and ensure long-term safe operation of the system. In case of special working conditions (such as high pressure or strong acid media) during installation, contact the manufacturer for customized installation solutions.
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