Gas Flow Computers

The Challenge

The Turk Stream is the first gas pipeline with a diameter of 81 centimetres to be laid at depths exceeding two kilometres. It starts on the Russian coast near the town of Anapa and runs over 930 kilometres through the Black Sea to come ashore in Kiyikoy, Turkey. When operational, Turk Stream will offer a reliable energy supply for Turkey and Europe by delivering 31.5 billion cubic meters of natural gas annually.
The offshore component of the system consists of two parallel pipelines; each made up of thousands of individual pipe joints of 12 meters in length. The pipes have been made from 39 millimetres of specially designed carbon manganese steel plates to withstand the huge pressure under the sea. Pipes laid in shallow waters closer to the shore have been coated in concrete for added stability and protection.
The biggest construction vessel in the world, Pioneering Spirit, carried out the offshore construction with the pipe joints welded to each other and to the main string on board. Each weld was tested and coated for protection before the pipeline string was lowered into the water.
Pioneering Spirit has completed the construction in just over 15 months. Operating around the clock, the vessel laid 5 kilometres of pipeline on average each day.
Once completed the pipeline needed to be cleaned internally, using a Pipe Inspection Gauge, known as a PIG. A PIG can be used to inspect or clean a pipe without stopping the flow of the product, in this case natural gas. The PIG is inserted into a launching station and then the pressure-driven flow of the product forces it down the pipe until it reaches the receiving station. Throughout its journey the PIG transmits data on the condition of the pipe interior to engineers monitoring its progress.

The Solution

Baker Hughes Process and Pipeline Services were contracted for the Turk Stream pipeline pig operations. Contrec, the global leader of high quality flow instrumentation, supplied two Contrec 515 (GC-02) General Gas Flow Computers as part of the bespoke compressed air and nitrogen flow measurement control solution supplied.
The complete control solution incorporated two 12″ F200 E&H Vortex Flowmeters, two Pressure TX, two Temp TX, one Downstream Pressure TX, one Differential Pressure TX, one Control Panel and one Oxygen Sensor. In addition to Contrec’s 515 (GC-02) Gas Flow Computers, the control panel incorporated one Siemens PLC, one Red-lion HMI, one GSM Internet Gateway, UPS power backup system and control valve override switch/controller.
The 515 (GC-02) Gas Flow Computers were selected for their capability and accuracy in the conversion of gas volume to corrected volume and mass. The GC-02 application measures the volume, corrected volume and mass of a general gas. The properties of a gas are calculated using common industry standard equations of state. These equations use a simplified set of parameters to quickly and accurately determine the value of compressibility and actual quantity of gas.
The 515 (GC-02) also offers connectivity integration between Modbus and Ethernet with HMI PLC, which made it easy to get multiple parameters such as pressure, temperature and flow.
During Pigging operations the system used signals from one set of instruments but could have been switched over to the second set in the event of a component failure or other measuring related issue.
This bespoke measurement and control package was designed to accurately measure the volume and mass flow of air, pressure and temperature through both pipe work systems. It provided auto PID control of a pneumatically actuated 10″ V-ball valve to govern the speed of the pig train based on the calculated mass flow rate of air and monitored differential pressure across downstream air filters.
In addition all the data was logged for the complete pigging operations locally and securely to the Cloud. To ensure safe and effective completion of the clean it provided local visual system alarms and remote e-mail alarms to specified users; it also supplied back-up power to all instrumentation and control valves for 60 minutes in the event of site main power loss. As an additional safety feature it also provided local manual override of control valve positions and local emergency shutdown of valves.
It allowed for auto PID control for final air venting of pipe lines based on downstream system pressure and monitored oxygen content of air to determine arrival of nitrogen gas packing. And finally it allowed authorised remote access to PLC and HMI programs to enable engineers to carry out system modifications.
Contrec’s 515 (GC-02) General Gas Flow Computers played an integral part in this bespoke compressed air and nitrogen flow measurement control solution for Turk Stream. This solution operated in a challenging environment, as part of a ground-breaking international project that has advanced the technical boundaries of the gas pipeline industry.