Sample layout of an unloading station

The systems for emptying tank wagons are engineered and configured such as tank wagon filling facilities as per the customers specification.

Design data for the unloading system :

• Double-track system to 2 x 32KWG

• Unloading performance/day 128KWG

• Workers on the tank wagon 4

• Maximum daily capacity to 6,780 m³/d  3,870 T/d

• Spare time / day* 1 hour /d

• Annual capacity (340 days/year) 1.315.800 T

* The spare time changes at low temperatures since tank wagon pressure  relief  to 0.7 bar takes less time.

Describing the technological operating systems

The following operating systems are specifically engineered for double-track unloading system for a maximum of 32 KWG / track for all unloading tank wagons. Otherwise, these operating systems should be provided as in one loading tank wagon.

Emptying systems   

2 DN40 flexible conduit loaders for the product side are used to drain the liquid hydrocarbon gases and their mixtures (unloading).

1 DN40 flexible conduit loader for the steaming side is used for impinging the tank wagons with excess pressure ∆p ≥ 1 bar.

Additional  Emptying Systems

in opposite to the railcar filling systems are:

Compressor systems

The compressor system in a specific design for generating the differential pressure between the tank wagon and storage tank to transport the product from the tank wagon into the storage tank. It is planned for unloading tank wagons so that it automatically switches from pressure operation to suction operation in the tank wagon by switching over to KWG pressure relief.

This compressor system has the following functions:

  • returning the hydrocarbon vapours remaining when emptying the tank wagon by draining them into the storage tanks
  •  reducing the excess pressure to 0.07 MPa in the emptied tank wagons in conformity with WUP SNE-87 2.15.

SUG evaporator

The SUG evaporator supports the compressor system in cold seasons. This ensures that there is enough gas on the suction side of the compressors to compress the needed differential pressure ∆p. This is necessary with butane fractions where the steaming pressure (absolute) at – 20°C p = 0.47 bar (kg/cm“). The evaporating energy can be generated by:

  • ­the energy medium of steam

  • electrical energy 380 V AC; 50 Hz 

Emptying Regulation

The product flow / KWG should be limited to an unloading rate of 26 m³/h due to the product corner valves of the tank wagons. This is done with an eddy current measuring instrument installed in each emptying position (± 0.6% accuracy) that triggers the control valve to 26 m³/h. 

If a tank wagon in the group to be emptied is empty, a sensor mounted in the product distributor indicates the end of unloading and the control valve is automatically closed. Then the tank wagon is separated from the emptying group.

Data logging

The data logging of the quantity loaded / KWG are recorded legal-for-trade with a:

 Dynamic weighing – bridge, located in front of the railcar loading unit. With passing of the weighing – bridge  with a railcar unit (before and after loading procedure), the quantity loaded per railcar will be recorded legally approved.
(Measuring accuracy: ± 50 kg)

  • Coriolis - mass meter DN80, certified as a licensed measuring instrument in connection with the appropriate control electronics for calculating:
  • ­the filled quantity of product per tank wagon [kg]
  • ­the density of the filled quantity of product [kg/m³] measuring accuracy: ± 0.15%

The quantities loaded are registered and administered in the Scherzer loading computer and the loading voucher is printed out. The loading data can be exported to the customer’s host system.

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