MechChem Africa March 2017

⎪ Petrochemical industries, oil and gas ⎪

Energas Technologies has completed a commission to design and supply a mobile heater skid for the high-pressure natural gas line between Mozambique and South Africa. Mobile heater skid for 127 km natural gas pipeline

T he existing 865 km Mozambique to Secunda Pipeline (MSP) for natural gas from Mozambique to South Africa is currently the only sustainable source of natural gas to South Africa and, in order to meet the demand for natural gas in South Africa, the transportcapacityofthislinehasbeensignificantly increased. In order to facilitate this increase, a combination of compressors and parallel lines – at approximately128kmper section–had tobebuilt. The Republic of Mozambique Pipeline Investment Company (ROMPCO), owner of the existing pipeline, represents a joint initiative between Sasol, Companhia Mocambiçana de Gasodutoand theSouthAfricanGasDevelopment Company (iGas), and has played a pivotal role in commercialisingMozambique’s natural gas supply. With the backing of a successful first project, Loop Line 1, Sasol Group Technology, which was spearheading this project at ROMPCO’s behest, appointed VGI Consulting Africa as the EPCM contractor for the Loop Line 2 (LL2) undertaking. The 26-inch LL2 adds further capacity to the system through the installation of a 127 kmparal- lel pipeline to the existing MSP line that ties back into the MSP. The importance of this gas supply cannot be understated. Much of the supply is fed to the Gauteng region in South Africa, a commer- cial and industrial hub that has earned the city of Johannesburg the title of ‘Africa’s powerhouse’. This feeder line supports residential, commer- cial, power generation and industrial heating requirements in the Gauteng area. Further to this, the supply also supports the operations of Sasol’s liquids and chemical plants in Secunda and Sasolburg as well as other large, energy-intense industries nearby. Commissioning of LL2 with Energas mobile heater skids For the commissioning of LL2, the new line was filled and pressurised from atmospheric pressure to a line pack pressure of 116 bar. The filling gas had tobepreheated toensure the temperaturedid not dropbelowthepipelineminimumdesignmetal temperature of zero – due to the Joule Thompson cooling effect –while the flow ratewas controlled andmonitored. A flow totaliser added the benefit of measuring the normalised volume of gas con- sumed to achieve the required line pack. The project specification called for the design, manufacturing and supply of a transportable skid- mounted electrical gas heater with flow control in accordance with ASME 31.8, ASME VIII and SANS 10108. Design, fabrication, complete as- sembly and testing of the heater skidwere done in SouthAfricabeforedeliverytositeinMozambique. Laetitia Botha, Energas Technologies product engineer comments: “Energas specialises in the

design, manufacture and supply of skid-mounted pressure reduction and metering stations to the natural gas industry. Most of these skids are for sites in remote areas and being able to complete the fabrication and assembly in South Africa sig- nificantly reduces schedule risk, siteestablishment and workforce logistics. “Another benefit of the mobile heater skid is that it could be relocated and used at different site points or locations as the new pipeline sec- tions were being constructed. The heater skid is only required once during the commissioning of a new section and it is therefore not required as a permanent installation. It’s a cost-effective solu- tion to invest in amobile skid that canbe relocated where needed.” The heater skid comprises a thyristor control panel, a 416 kWheater with isolation valves, flow meter, filter, instrumentation and manually oper- atedcontrol valve tomeasure, heat andcontrol the filling of LL2 during commissioning. The thyristor controller monitors the gas temperature at the outlet of the control valve and controls the power to the heater’s elements in order to maintain an outlet gas temperature of 10 °C. During commis- sioning the electrical heater was powered by a diesel generator. AMokveld equal percentage axial flowmanual control valvewas chosen to control theflowof gas from 116 bar to, initially, atmospheric pressure. This required a special trim that allowed precise control while noise and vibrations were very low. The control valve andheating capacity allowed the LL2 commissioning team to make effective use of the gas volumes made available by the pipeline operator, leading to the pipeline being commis- sioned much sooner than originally anticipated. “The natural gas industry both in South Africa and Africa is a growing one and has a bright future ahead. We have directly felt the effects of this growth through ongoing skid manufac- turing projects in Ghana, the Western Cape and Mozambique,” Botha concludes. q

The heater skid comprises a thyristor control panel, a 416 kW heater with isolation valves, flow meter, filter, instrumentation and manually operated control valve to measure, heat and control the filling of LL2 during commissioning.

March 2017 • MechChem Africa ¦ 25