Hongze Valve
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Dismantling Joint – Single Flange Gland Type
Dismantling Joint – Single Flange Gland Type is a flexible pipeline connection component designed for easy installation and disassembly of valves, pumps, and other pipeline equipment, especially in confined spaces. This joint features a flanged connection on one side and a gland-end (compression sleeve) connection on the other, offering both structural stability and installation convenience.
The flanged side ensures secure bolted connection with standard pipeline flanges, while the gland side allows for direct insertion and compression of the pipe end using bolts and sealing gaskets. This dual-end structure eliminates the need for full flange connections on both ends, which is particularly useful in retrofit projects or where one end of the pipeline is welded or socket-connected.
Equipped with limit rods (tie rods), this dismantling joint effectively transfers axial thrust force and prevents pipeline separation caused by internal pressure or ground movement. The unit provides limited axial flexibility, making it ideal for systems that require vibration absorption, thermal expansion tolerance, or frequent maintenance.
Manufactured using high-quality ductile iron or carbon steel with epoxy coating, the joint delivers excellent resistance to corrosion, mechanical stress, and long-term wear. It is widely used in water supply systems, HVAC pipelines, sewage treatment facilities, fire protection networks, and industrial fluid transmission lines.
Key Features
Technical Specifications
| Nominal Diameter (DN) | Inch | Length (L) mm | Flange Thickness (b) mm | Bolt Qty (pcs) | Bolt Hole Dia. (mm) | Bolt Circle Dia. (D1) mm | Axial Expansion Range (mm) |
|---|---|---|---|---|---|---|---|
| DN50 | 2″ | 130 | 18 | 4 | 18 | 125 | 10 |
| DN65 | 2.5″ | 135 | 20 | 4 | 18 | 145 | 10 |
| DN80 | 3″ | 145 | 22 | 8 | 18 | 160 | 12 |
| DN100 | 4″ | 155 | 24 | 8 | 18 | 180 | 12 |
| DN125 | 5″ | 165 | 26 | 8 | 18 | 210 | 14 |
| DN150 | 6″ | 175 | 28 | 8 | 18 | 240 | 14 |
| DN200 | 8″ | 190 | 30 | 12 | 18 | 295 | 16 |
| DN250 | 10″ | 210 | 32 | 12 | 18 | 350 | 16 |
| DN300 | 12″ | 230 | 34 | 12 | 18 | 400 | 18 |
| DN350 | 14″ | 250 | 36 | 16 | 18 | 460 | 18 |
| DN400 | 16″ | 270 | 38 | 16 | 18 | 515 | 18 |
| DN450 | 18″ | 290 | 40 | 20 | 18 | 565 | 20 |
| DN500 | 20″ | 310 | 42 | 20 | 18 | 620 | 20 |
| DN600 | 24″ | 330 | 48 | 20 | 18 | 725 | 20 |
| Parameter | Unit | Specification |
|---|---|---|
| Product Name | – | Flanged Loose Sleeve Joint |
| Model Code | – | ZD-FLJ (Flange Loose Joint, No Tie Rods) |
| Nominal Diameter Range | mm | DN50 – DN600 |
| Connection Type | – | Flange × Flange |
| Working Pressure | MPa / Bar | PN10 (10 bar), PN16 (16 bar), PN25 (25 bar) |
| Shell Test Pressure | MPa | 1.5 × Working Pressure |
| Seal Test Pressure | MPa | 1.1 × Working Pressure |
| Applicable Temperature | °C | -20°C to +200°C (Depending on gasket material) |
| Applicable Medium | – | Water, Wastewater, Oil, Gas, Compressed Air, Weak Acid & Alkali |
| Axial Expansion Capability | mm | 10 – 20 mm (based on diameter) |
| Angular Deflection (max) | ° | 8° – 12° |
| Lateral Displacement (max) | mm | Up to 20 mm |
| Connection Standard | – | GB/T 9115, ISO 7005, EN 1092, ANSI B16.5 (customizable) |
| Sealing Performance | – | No visible leakage under working pressure |
| Internal Structure | – | Sleeve type telescopic structure with compression gasket sealing |
| Design Life (Recommended) | Years | 8 – 15 Years (with proper maintenance and within pressure/temperature limits) |
| Installation Location | – | Aboveground, Indoor, Outdoor, Not recommended for buried use unless protected |
| Component | Material Option 1 | Material Option 2 | Application & Notes |
|---|---|---|---|
| Main Body | Ductile Cast Iron (GGG40 / GGG50) | Carbon Steel (Q235 / Q345) | GGG50: Suitable for water, heating, and municipal applications; Q345: for industrial use |
| Loose Flange Ends | Carbon Steel (Q235B / Q345B) | Stainless Steel (SS304 / SS316) | Flanges drilled per GB, DIN, ANSI, or EN standards |
| Sleeve Section | Carbon Steel | Stainless Steel | The sliding or telescopic section that accommodates axial movement |
| Sealing Gasket | EPDM (Ethylene Propylene Rubber) | NBR (Nitrile Rubber) / PTFE | EPDM: Water, hot water, alkaline; NBR: Oil, fuel; PTFE: Chemicals, acids, solvents |
| Bolts & Nuts | Carbon Steel, Zinc-Plated | Stainless Steel (A2-70 / A4-80) | Use appropriate strength class (e.g., 8.8) for pressure applications |
| Washer / Spacer Ring | Carbon Steel with Zinc Coating | Stainless Steel | Helps evenly distribute pressure around the sealing surface |
| Coating | Fusion Bonded Epoxy (≥250μm) | Bitumen Paint / Bare Stainless Finish | Epoxy is standard; bitumen for underground; stainless may be uncoated if polished |
| Surface Finish | Shot-blasted to Sa2.5, coated | Polished & Passivated (for SS) | Shot-blasting improves adhesion; passivation improves corrosion resistance |
🔍 Material Selection Recommendations
Ductile Iron (GGG50) is the most cost-effective and widely used for civil water systems.
Carbon Steel (Q345) is recommended for general industrial pipelines under high strength requirements.
Stainless Steel (SS316) is ideal for chemical plants, coastal, marine, or food-grade applications.
PTFE Gaskets should be used for corrosive or high-temperature media above 120°C.
Fusion Bonded Epoxy (FBE) provides 15–20 years of corrosion protection in potable water lines if undamaged.
| Step | Installation Task | Detailed Procedure & Notes |
|---|---|---|
| 1️⃣ | Inspection Before Installation | – Unpack all components and inspect the joint body, sealing surfaces, flanges, and sleeve – Ensure no deformation, rust, or transport damage |
| 2️⃣ | Pipeline End Preparation | – Pipe ends must be flat, clean, burr-free, and cut perpendicular to the axis – Verify axial alignment and that there is sufficient straight pipe on both sides |
| 3️⃣ | Positioning the Joint | – Insert the loose sleeve joint between two pipeline flanges – Ensure the flanges match the bolt hole pattern and pressure rating |
| 4️⃣ | Gasket Placement | – Place the correct gasket (EPDM/NBR/PTFE) between each flange face – Center the gasket carefully to avoid displacement during tightening |
| 5️⃣ | Bolt Assembly | – Insert flange bolts symmetrically and tighten in a star pattern (e.g. 12→6→3→9…) – Do not fully tighten one side before the other |
| 6️⃣ | Axial Adjustment | – If minor misalignment or expansion space is needed, adjust the sleeve position within its allowable axial range (usually 10–20 mm) |
| 7️⃣ | Final Torque Application | – Use a calibrated torque wrench to tighten bolts according to torque tables (varies by DN and pressure) – Ensure even compression of the gasket |
| 8️⃣ | Sealing Check | – Confirm gasket is not visible outside the flange connection and that no uneven gaps exist |
| 9️⃣ | Pressure Testing | – Conduct hydrostatic or pneumatic pressure testing per standard – Monitor for any leakage at flange faces and around gasket area |
| 🔟 | Commissioning | – After successful testing, slowly pressurize the line and bring the system into operation |
⚠️ Important Installation Tips
| Topic | Best Practice |
|---|---|
| Gasket Selection | Always match gasket to the medium (e.g. EPDM for water, PTFE for chemicals) |
| Alignment Tolerance | Allowable misalignment < 2 mm and angular deflection < 3° |
| Do Not Use as Load Bearing | Joint should not bear pipe weight—use proper pipe supports |
| No Tie Rods Included | This joint type does not include limit rods—not suitable for thrust restraint |
| Underground Installation | Apply additional bitumen or PE wrapping for buried service |
| Maintenance Task | Recommended Frequency | Detailed Procedure & Notes | Purpose / Effect |
|---|---|---|---|
| 🔍 Visual Inspection | Monthly / Quarterly | – Check for signs of leakage, flange rust, or sleeve misalignment – Inspect flange coating or paint condition | Detect early corrosion, deformation, or potential failure |
| 🔧 Bolt Tightness Check | Every 3–6 months | – Use torque wrench to verify flange bolts are still within specified torque – Tighten in cross-pattern if needed | Prevent gasket relaxation or leakage due to vibration or thermal cycling |
| 🧪 Seal/Gasket Condition Check | Every 6–12 months | – Check for aging signs: hardening, cracks, swelling, extrusion – Replace with identical size and material if necessary | Ensure reliable sealing and prevent unplanned shutdowns |
| 🧱 Sleeve Movement Check | Annually | – Confirm the sleeve still has axial flexibility within rated range – No rust jamming or overcompression signs | Ensure continued ability to absorb expansion or misalignment |
| 🧴 Surface Protection Maintenance | Annually | – Remove surface dust, reapply fusion bonded epoxy or corrosion protection paint if damaged – Touch up damaged areas | Maintain corrosion resistance and extend product lifespan |
| 🔁 Bolt/Nut Replacement | Every 3–5 years | – Replace bolts/nuts if threads are rusted or stripped – Use matching material and grade (e.g. A2-70, 8.8 class) | Maintain mechanical integrity and flange strength |
| 🧾 Maintenance Logging | Every inspection | – Record date, observations, actions taken, and part replacements – Include technician name and photos if possible | Establish service history and support future troubleshooting |
⚠️ Common Failure Symptoms & Solutions
| Symptom | Likely Cause | Recommended Action |
|---|---|---|
| Flange leakage | Gasket wear or under-tightened bolts | Replace gasket, re-torque all bolts |
| Gasket extrusion | Overcompression or pressure surge | Install correct gasket thickness, inspect pressure control |
| Rust on sleeve or bolts | Damaged coating or humid environment | Clean surface, repaint, or upgrade to stainless bolts |
| No axial movement | Internal rust binding sleeve | Disassemble, clean, grease, or replace |
| Flange misalignment | Pipe settlement or thermal distortion | Re-align pipeline supports, reinstall joint if necessary |
✅ Recommended Spare Parts
Rubber Gaskets (EPDM, NBR, or PTFE) – matched to pressure and media
Full sets of Flange Bolts & Nuts
Sleeve Section (if replaceable type)
What is the purpose of a single flange dismantling joint?
A single flange dismantling joint is used to connect pipelines where one end is flanged and the other end is a plain pipe. It simplifies installation and removal of valves, pumps, or pipeline sections, especially in tight spaces or retrofit applications. The gland-end allows for direct compression connection without welding or flange preparation.
What are the advantages of using a gland-type end?
The gland-type end offers easy on-site connection by compressing the joint around the inserted pipe using bolts and gaskets. This provides a secure seal without the need for welding or additional flanges, making installation faster and more flexible—ideal for systems where one end is not flanged.
How does the dismantling joint handle pressure and movement?
The joint is equipped with limit rods (tie rods) that absorb axial thrust caused by internal pressure, preventing pipeline separation. It also allows limited axial flexibility to accommodate thermal expansion, vibration, and slight misalignment between pipeline sections.
In which applications is this type of dismantling joint commonly used?
This joint is widely used in water supply networks, wastewater treatment plants, HVAC systems, fire protection pipelines, and industrial fluid transmission lines. It’s especially beneficial in installations where one end of the pipeline is fixed or welded and the other requires periodic maintenance access.
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