What Is a Rail Fish Plate?
A rail fish plate (joint bar) is a mechanical continuity component that connects rail segments so that track geometry and stiffness remain stable across joints during repeated train passage. Its accuracy directly affects joint durability. Fish plates are produced for GB light rail and heavy rail, UIC profiles, DIN 536 and QU crane rails, JIS rail sections, AS 1085 rails, BS 11 profiles and AREMA/ASCE rails.
Types of Rail Joint Bars
| Type | Primary Function |
|---|---|
| Standard fish plates | Connect rail ends of the same size, typically with 4 or 6 holes, for standard rail joints |
| Insulated fish plates | Electrically isolate rail sections for signaling systems using non-conductive materials |
| Compromise fish plates | Transition joints connecting rails of different sizes or profiles |
| Joggled fish plates | Bent shape for temporary repair or to accommodate rail defects |
| Glued insulated joints (GIJ) | High-strength bonded joints that minimize movement on high-speed or heavy-axle lines |
| Crane rail fish plates | Heavy-duty plates for crane rail profiles (for example QU70, QU100, QU120) |
Are Insulated Fish Plates Needed for All Train Tracks?
Insulated fish plates (or insulated rail joints) are not needed for all train tracks; they are specifically required in areas with electrical signaling systems, track circuits, or at turnouts to prevent electrical interference. They are crucial for separating track sections, while standard, non-insulated fish plates are used on conventional track sections where insulation is unnecessary.
When Insulation Is Essential
- Signaling systems: essential where track circuits are used for train detection.
- Electrified tracks: crucial in electrified railway systems to maintain electrical isolation.
- Turnouts and special track work: used at turnout conversion parts to prevent current from interfering with turnout control circuits.
- Bridge/tunnel safety: often required in humid environments to prevent electrical leakage.
When It Is Not Needed
- Standard non-signaled tracks or conventional railway sections where electrical isolation is not required.
- Modern continuously welded rail (CWR) may require fewer joints; but where gaps are needed for signaling, insulation remains crucial.
What Materials Are Used for Rail Joint Bars?
Rail joint bars (or fishplates) are primarily manufactured from high-strength carbon steel, such as 45#, 50#, 55# steel, or alloy steels like 50Mn for enhanced durability. They are designed to withstand heavy railway, crane or light rail loads. Specialized insulated joints use high-strength composite materials to provide electrical isolation.
| Material | Typical Grade | Notes |
|---|---|---|
| Carbon structural steel | Q235 (GB/T 700) | Common mild steel for general joint bars; similar to ASTM A36, S235JR |
| Medium carbon steel | 50Mn / 55# (GB/T 699) | Classic high-strength fish plate steel for mainline joints |
| Alloy steel | 42CrMo (GB/T 3077) | High-strength, high-toughness alloy for severe service; similar to AISI 4140 |
| Spheroidal graphite cast iron | QT450-10 (GB/T 1348) | Used in some traditional joint kits for castability and damping |
| Insulating composite | Epoxy fiberglass / FRP | Electrical insulation (resistivity > 10¹² Ω·cm), corrosion resistance |
Use standard fish plates for conventional joints; specify insulated fish plates (or glued insulated joints) wherever track circuits, signaling, electrification or turnout control requires electrical separation.
Request Insulated Fish Plate Pricing
Insulated fish plates are mainly required where track circuits, signaling, or electrical isolation is needed; they are not necessary for every railway track. The correct type should be selected according to the signaling system, rail profile, and joint design. GNEE RAILWAY RAILWAY supplies insulated and standard fish plates for different rail systems and track requirements.