CRYOGEN GAS REFUELING STATION

Ascon Tecnologic’s I/O modules are used in a plant that loads gas into cylinders.
This plant includes:
– A central cryogenic tank
– A high pressure pump
– A vaporizer
and several petrol stations.
The plant requires that the control systems are mounted in each position with a truly distributed system.

NEEDS

Check the system for correct and safe operation of the system.
The process uses low temperature technology that compensates for the heating generated by the compression of the gas.
The main variables and data to monitor and control include:
– Temperature of the liquefied gas at the delivery point;
– Gas temperature downstream of the vaporizer;
– Pump stuffing box temperature.

SOLUTION

Complete control system with CPU, I/O modules and operator panel.
The analogue I/O modules acquire all temperatures, for temperature control and to generate alarm thresholds.

Controls and operation
Temperatures are controlled by valves, while pressure is controlled by a pump. Interlocks and alarms are provided for various conditions such as: loss of the pump gland, failure when starting the pump, high pressure and diagnostics of the I/O modules.
The control system has to work with different types of gas and manage the plant options as a static fill system. The plant must also comply with the regulations of the local authorities on safety at work.

System architecture
The control unit (CPU) of the Sigma series by Ascon Tecnologic generates commands to the pump and the control valve.
Data and commands are available on an operator panel connected via serial communication.
Based on the temperatures detected and the related thresholds, the CPU stops the pump to prevent damage to the system.
The shunt down is particularly important if the temperature downstream of the vaporizer is too low, since the equipment is not designed for cryogenic temperatures and can be damaged.

The Ascon Tecnologic system was chosen because:

– It is a distributed system based on stand-alone modules, with Fieldbus interface and integrated power supply;
– The modules are smart to relieve the CPU from complex calculations and increase the connection speed;
– It is a flexible and simple solution.