| Medium Type | Recommended Rubber Material | Performance Parameters | Notes |
|---|
| Strong acid/alkali (pH ≤2 or ≥12) | EPDM (Ethylene-Propylene-Diene Rubber) | Resistant to pH 2-13, temperature range -20°C to +150°C | Verify compatibility of flange anti-corrosion coatings (e.g., PTFE spray) with the medium |
| Organic solvents/oils | FKM (Fluororubber) | Resistant to gasoline, benzene; temperature range -10°C to +250°C | Prohibited for media containing ketones/esters (may cause swelling); require additional fabric reinforcement |
| High-temperature steam (≥180°C) | Silicone rubber + fiberglass reinforcement | Temperature range -60°C to +200°C (short-term +250°C) | For steam pressure >1.6 MPa, use pressure-resistant type with metal skeleton; avoid condensate accumulation during installation |
| Particulate/abrasive media | NR (Natural rubber) + wear-resistant layer | Shore hardness 60-70A, tear strength ≥15 MPa | Install Y-type filters at inlets/outlets; add wear-resistant coating (e.g., neoprene) to sphere surface |
| Toxic/flammable media | PTFE (Polytetrafluoroethylene) lining | Temperature range -200°C to +260°C, permeability ≈0 | Must be paired with explosion-proof limit flanges; apply anti-loosening adhesive (e.g., Loctite 243) to bolts; regularly monitor leakage rate |
- Double-flange joints must be equipped with limit bolts (adjustment range ≤±5 mm) to prevent sphere tearing from excessive displacement, especially in:
▶ Reciprocating pump outlets (vibration frequency >50 Hz);
▶ Heat transfer pipelines with temperature difference >80°C (calculate axial expansion ΔL = α×L×ΔT, where α = linear expansion coefficient of pipe material). - Ensure flange parallelism error ≤1 mm and angular deviation ≤1.5° during installation to avoid eccentric loading and localized stress concentration.
| Flange Size (DN) | Bolt Material | Tightening Torque (N·m) | Anti-Loosening Measures |
|---|
| DN50-DN150 | 304 stainless steel | 40-60 | Use spring washers + diagonal tightening in 3 stages |
| DN200-DN400 | 316L stainless steel + PTFE coating | 80-120 | Apply molybdenum disulfide lubricant to threads; retighten every 6 months |
- Galvanized bolts are strictly prohibited (risk of electrochemical reactions with chemical media); use titanium alloy bolts in coastal areas.
- Install guide supports 1 pipe diameter away from the joint to prevent lateral displacement exceeding limits;
- For vertical installations (DN ≥200), install load-bearing supports below the joint (load capacity ≥ sphere weight + medium weight).
- When transient pressure peaks >1.3 times design pressure, install:
▶ Pulsation dampers (e.g., bladder type, volume ≥ pipeline cross-sectional area ×0.5 m);
▶ Limit flange stop blocks with thickness ≥10 mm (Q345R material).
- Wet chlorine media: Use FKM rubber + 316L stainless steel flanges with chlorosulfonated polyethylene (CSM) coating;
- Seawater pipelines: Apply zinc anode protection to flanges (potential difference ≤-1.1 V) and seal bolt holes with polyurea.
- For temperature differences >100°C, use dual-layer spheres (inner silicone + outer EPDM) with thermal compensators (e.g., bellows expansion joints);
- For low-temperature applications (≤-40°C), use cold-resistant rubber (Shore hardness ≤50A) and conduct -50°C impact tests prior to installation.
| Inspection Frequency | Item | Acceptance Criteria | Corrective Action |
|---|
| Monthly | Surface cracks/blisters | Crack length >5 mm or blister height >3 mm | Replace immediately |
| Quarterly | Flange seal leakage | Bubble test (soapy water) ≥5 bubbles/min | Retighten bolts or replace gaskets |
| Annually | Rubber aging | Shore hardness change >15 HA or tensile strength reduction >20% | Sample for material testing, assess remaining life |
| Biannually | Limit device integrity | Bolt elongation >1% or thread wear >1 pitch | Replace limit components, recalibrate displacement |
In case of leakage:
① Activate bypass line for immediate pressure relief;
② Apply emergency 堵漏夹具 with PTFE gasket for temporary sealing;
③ For toxic media, operators must wear Type A chemical protective suits (permeation resistance >8 hours).
- Atmospheric/vacuum distillation tower bottoms (DN300, 350°C residual oil):
FKM rubber + 316L flanges with bidirectional limiters, compensating ΔL = 28 mm; leak-free operation for 3 years.
- Syngas pipeline (DN200, 15% H₂S, 200°C):
PTFE-lined joints with titanium alloy flanges and steel mesh reinforcement; helium leak testing every 6 months (leak rate <1×10⁻⁹ Pa·m³/s).
- Hydrochloric acid circulation (DN100, pH=1, 80°C):
EPDM rubber + electropolished 304 flanges; horizontal installation to prevent media accumulation and localized corrosion.
- Domestic Standards:
- GB/T 26121-2010 Rubber Joints
- HG/T 2289-2017 Flexible Rubber Joints
- Chemical Industry Requirements:
- SH/T 3406-2013 Petrochemical Steel Flanges (flange rating ≥1.5× design pressure)
- GB 50160-2008 Fire Protection Code for Petrochemical Plants (explosion-proof joints with Ex d IIBT4 rating for flammable media)
Note: Ordinary rubber joints are prohibited in SIL2+ safety systems. Use intelligent joints with built-in sensors (e.g., strain gauges for real-time displacement/stress monitoring).
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