TEHRAN, May 04 (Shana) -- National Iranian Gas Company (NIGC) and Oil Turbo Compressor Co. (OTC) signed a Memorandum of Understanding with Germany's Siemens. Managing Director of NIGC Hamidreza Araqi, Managing Director of Oil Turbo Compressor Group (OTC Group) Saeed Mohtadi and Siegfried Russwurm, member of the Managing Board of Siemens,...