EMS Pipeline Services (EMS) started its operations in 2003 in Houston, Texas. Main Street Mezzanine Fund made an investment in EMS to support a management team in the purchase of Hanover Measurement Services, LP (HMS) from Enron North America and Hanover Compressor Company. EMS is a leading provider of gas measurement and other energy infrastructure services to natural gas industry participants. In addition, EMS owns PGAS, which is a proprietary software system licensed to a majority of the larger gas transmission companies in North America. EMS provides gas measurement and other services for several key customers, including the Houston Pipeline Company, a subsidiary of Energy Transfer Partners, L.P., Calpine, Duke Energy, ChevronTexaco, ONEOK and BP.