Frequently Asked Questions ( FAQ) on Electrolock Joints


Electrolock is a boltless restrained joint system with a double chamber socket to be used in Ductile Iron (DI) pipelines. It uses the same gasket as the normal push-on joint. The second chamber accommodates mechanical anchorage provided by specially designed locking bars or plates. It locks with a weld bead made on the jointing spigot. Electrolock joint Ductile Iron (DI) pipes are supplied with compatible Electrolock type Ductile Iron (DI) Fittings. Restrained joints are designed and tested as per the provisions of ISO 2531, EN 545 and ISO 10804.

Before the advent of Ductile Iron( DI) Pipes and Fittings (DI) pipes with boltless restrained joint, the older restrained joint design required cumbersome bolting arrangements with a separately cast follower gland, to serve the purpose of physically restraining the joint. However, in the new ‘Electrolock’ design no bolting is required to do the restraining. The advantages are manifold:

  • Easier to assemble and disassemble
  • Faster jointing
  • Lesser excavation at joint since no bolting is required
  • No separate follower gland is required
  • As there is no extended part, it can be used for trenchless laying of DI pipe

The thrust force developed in a Ductile Iron (DI) pipeline is dispersed along the calculated restraining length with the help of:

  • Passive soil resistance
  • Skin friction between the pipe and the surrounding soil

The concept is explained with a sample force diagram showing the thrust force and resistance forces at horizontal bend -

P: Thrust force developed by internal pressure
A: cross sectional area of pipe
Rs: Unit bearing resistance / Passive soil resistance
Ff: Unit frictional resistance / skin friction
L: Restrained length

  • Execution of project is faster. Concrete thrust block needs much longer time to install and cure.
  • Very useful where there is no space for thrust block.
  • Ideal for soils with low bearing capacity where a concrete thrust block can sink.
  • Eliminates chance of destabilization due to future excavation.
  • It is a more economical solution than conventional concrete thrust block.
  • There is further savings in terms of lesser manpower and machine engagement, lesser excavation and land acquisition cost.
  • No chance of third party interference
  • It is technically advanced and is a more sustainable solution having lesser carbon footprint compared to concrete thrust blocks