Fishplates, also called splice bars or joint bars, are implements used to join the ends of rail lengths together. While rail lengths are produced in the largest possible dimensions to minimize butt-jointed ends, the need for connecting hardware is necessary.
Fishplates are rectangular bars used as a set, one on either side of each rail. These bars feature several holes, through which two rails are bolted together to create a continuous track. They use a set of hardware consisting of fishtail (rail) bolts, rail nuts, flat washers, and spring washers to make the connection. Fishplates are not a reliable conductor, so track circuits require additional electrical wiring. The seam between rail lengths is the weakest portion of the track; even when using fishplates additional welding is often used to strengthen the joint.
Fishplates can be divided into three types
- Light Rail (8kg, 12kg, 15kg, 18kg, 22kg, 24kg and 30kg)
- Heavy Rail (38kg, 43kg, 50kg and 60kg)
- Crane Rail (QU70, QU80, QU100, QU120)
Railway fishplates are commonly found in four and six bolt hole configurations.
Insulated fishplates (joints) have a layer of non-conductive material, such as polyurethane plastic or epoxy resin, between the fishplate and rail. This layer provides insulation between the rail and the fishplate to ensure dielectric insulation for rails with signal circuits.
Most modern railways use continuous welded rail (CWR) that don’t need fishplates. In this form, track rails are welded together by using flash butt welding to form one continuous rail. Because there are few joints this form of track is very strong, gives a smooth ride, and needs less maintenance. Welded rails are more expensive to lay than jointed tracks but have much lower maintenance costs.
Fishplate standards may address terminology, equipment, or operations used with these processes. A list of example standards is found below.
DIN 5902 -- Fishplate for grooveless flat bottom rails
BS 47-1 -- Fishplate for rolled steel Railway Rails