When loading or unloading liquid or gaseous (petro-) chemical products at discharge stations there is often a hazard of spilling dangerous product or a hazard of severe damage by forgetting to disconnect the loading arms, hoses or stairs when a train, truck or tanker moves away.
To ensure safe operation of the loading stations, rail or barrier locks in combination with interlocking of the loading arms, hoses, pumps and stairs can be installed. These loading arms, hoses and stairs can be operated manually, pneumatically or hydraulically.
The interlock system ensures that a train, truck or tank-er will not access a loading station unless all loading arms, hoses and stairs are locked in a safe position and cannot be damaged while entering. Visa versa the train, truck or tanker cannot leave the loading station unless all loading arms, hoses and stairs are disconnected and locked in a safe position.
Furthermore it prevents a train or truck getting access of a loading station while another train or truck is already present at this loading station. The predetermined sequence may vary and is always depending on the client requirements.
Railway locks (SRL DRL etc.)
Locks for loading arms and stairs (SDL, DDL)
Key exchange boxes (KEB)
All loading arms, the stairs and the protection gate are locked in safe position up in the air away from the track. The product arm and the gas arm are manual operated. The stairs and the protection gate are pneumatically operated in this example.
The railway lock is unlocked with the key A trapped.
Once the train has entered the loading station it is secured by locking the railway lock. The train is now lock-ed and no other train can enter the loading station.
Take key A from the railway lock and insert the key into the key exchange box.
Once key A is inserted all three keys B can be released simultaneously.
If one of the keys B has been released key A will always be trapped.
Insert one of the keys B in the loading arm L1, another key B in the Gas arm G1 and the third key B in the stairs S1. Now the product arm, the gas arm and the stairs are unlocked and free to move. Take key C from the stairs and insert this key in the protection gate P1. Take out key D to unlock the protection gate P1. Now also the protection gate is free to move. Insert key D into the air three way valve V1 to unlock the closed position of the valve and open the valve. Key D is trapped and the system is pressurized. You can now connect all the loading equipment to the train to start loading. After completion disconnect all equipment and place it back in the safe position away from the track. Close the air three way valve and lock it by taking out key D. The stairs and protection gate cannot be operated anymore since there is no air supply. Insert key D into the protection gate and take out key C.
Insert key C into the stairs and take out key B. Take out the two other keys B from the loading arm and the gas arm.
All loading arms, the stairs and the protection gate are locked in safe position again.
Insert all three keys B into the key exchange box. Now key A can be released.
Insert key A into the railway lock to unlock the train. The train can now safely leave the loading station.
Please note that this just an example. Each system can be designed according to the client requirements.
The same kind of principle can also be applied on trucks and tankers.