SAFETY DEVICES USED IN HAULAGE ROADWAYS

Safety Devices Used In Haulage Roadways

Stop Block:
They are made in difficult forms & are used to stop or derail a moving tub on a track. Generally a wooden block which is pivoted to the sleeper at one end is kept across the track to derail the unwanted tubs. The track can be cleared by positioning the wooden block inclined with the track. It is used in direct rope haulage & main & tail rope haulage

Backstay or Drag:
These are used behind an ascending set of tubs as a safe guard against a broken rope or coupling. It is very strong & made up of steel of rail section. If the tub coupling or rope breaks, the ascending tub starts moving backward. At the pointed end of the drag gets fixed in the ground or sleeper to derail the tubs. It is used in direct rope haulage.

BUFFERS

When any roadway or face is in direct line with a haulage track and persons may be exposed from runaway tubs, strong buffers is provided and maintained on haulage road to prevent danger.

Buffers may be horizontal or vertical.

Back Catch or Monkey Catch: 
It comprises a piece of wood or rail placed in such a way that one end is always high enough to catch the axle of the backward run away tub. When the tubs move in moving in correct direction, its axle presses the elevated end of the back catch so that it can cross the back catch. In this safety device movement of tubs is possible because only in one direction. It is used in endless rope haulage.

Spring Catch:
It consists of a wooden block at one end & pressed sideways over the rail at the other end by a spring as shown in figure. The tub moving in proper direction pushes aside the wooden block & passes over it, but due to spring the wooden block at once returns to its original position to arrest a backward run away tub. It is used in endless rope haulage.

Age Croft Device:
It is some what similar to a monkey catch. But their designs to arrest forward run away automatically. When the tub is moving in the direction from B to A as shown in figure the front axle of the tub depresses the higher end ‘A’ of the pivoted bar AB & so raises the forked end ‘B’ to axle height. If the tub is moving at normal speed the ‘B’ end drops before the back axle reaches it. If the tub is moving very fast, the back axle of the tub is caught by the end ‘B’ & the tub is held in position. It is used in endless rope haulage.

APPROACH WARNING DEVICE

It is sometime necessary to warn man working and travelling in a haulage roadway.

A simple way of operating a warning device in a rope haulage roads is an arm protruding into the path of oncoming trams which, when deflected closes an electric circuit connected to a signal lamp or a bell.

The device is operated by a lever depressed by tram axle.

Jazz Rails:

In this safety device, the straight rail track is giving a very slight curve & again made straight. In some cases the track is bent at both sides & then made straight. At normal speed the tubs can easily cross it in either direction. But the uncontrolled tubs gets a high speed hence they cannot cross the jazz rails. Hence the derailment takes place. It is used in all types of haulage.

Manholes: 

Height should be more than 1.8 meter, depth should be more than 1.2 meter & width should be more than 0.7 to 1 meter. When person are allowed to work or pass through an incline, when the haulage is in motion, the manholes are made along the roadways sot that person travelling can take shelter in the manholes. The interval between two manholes should not be more 10 meters, but if the gradient is less than 1:6 the interval may be up to 20 meter. If the roadways are less than 1.8 meter in height the manhole should be made up of full height of the roadway it is used in direct, main & tail & endless rope haulages.

Run Away Switch:
This switch is normally kept open by a spring. When a lever handle is operated by an operator, the switch gets closed. And tubs can pass over it otherwise the tub derails when they pass over the runaway switch. It is used with direct rope haulage & main & tail rope haulage.

Runaway Switch & Stop Block:
This safety device is situated at the incline mouth of direct or main & tail rope haulage.In this safety device the stop block & the run away switch are so interconnected that at any time one of them is working. The distance between stop block & run away switch should be more than the train length (train length + 4.5 meter). The stop block & the primary switch are connected by a lever. When the lever is operated to clear the track from the stop block the run away switch is open. But as soon as the tubs crosses stop block the lever is again operated to close the run away switch & at the same time it is on the stop block.

Drop Warrick:

This safety device consists of a strong girder which is pivoted at the roof level through an eye bolt & pin. The pin is operated through a long wire attached to the swinging lever which is to be operated by the tubs, on the up hill side when the tubs are moving in downward direction. The control movement of tub does no exert in a pull or the wire but in case the tub running uncontrolled. It extracts a high pull on the wire through the lever which is turned. Drop the pivoted girder between tracks to arrest the forward runaway of the tubs. It is used with direct rope haulage, main & tail rope haulage & endless rope haulage.

POINTER PLATES

This is fitted on the main haulage track to deflect a backward runaway into the prepared side of the roadway.

The derailed tubs may be automatically re-railed when drawn forward.

RETARDERS

Slowing down and stopping tubs are integral parts of haulage operation.

A hand operator retarder consists of two planks, line on the top with belting and mounting on cams.

An end cover plank fastened to the inside faces of planks serves to hold the plank in position.

They are operated by a single lever.

When the cams are fully raised, the tub wheels are lifted clear to the rails and a braking action is provided on the axle.

The tub retarders represents waste of energy and should be avoided in planning.

However, the speed movement of tubs required for quick turn over and higher rising may make its application essential at pit top, pit bottom haul brow heads etc.

There are many types of elaborate designs and manually control.

Smooth breaking may be affected by air or hydraulic breaking.

Fully automatic retarders, which are released by pneumatic cylinder, are widely used.

The device consists of two pairs of hinged bars faced with renewable skid plates and breaking action effected by movement of two opposing pistons of in a cylinder containing air.

The bars are raised above the rail level and grip the wheels.

When no braking is desired, the value releasing to the atmosphere is opened after cutting of compressed air supply.

A spring draws back the breaking bars to normal position.

An automatic hydraulic tub retarder is suitable for locomotive haulage or ordinary rope haulage.

The hydraulic pressure is supplied from 1-2 KW electrically driven pump.

The oncoming tramp is retarded by the trained of the leading wheels running fixed skids

And an  inclined hinged platform which act as a wedge.