South African energy giant Sasol has ordered the main ethylene compressors, a critical component of its multibillion-dollar facility in Westlake, from MHI Compressor International Corp.

Sasol did not disclose the compressors’ cost in the announcement Monday. The compressors are the largest made by MHI’s parent company, Mitsubishi Heavy Industries Compressor Corp. Mitsubishi Heavy Industries Compressor Corp.’s website says these types of compressors form “the heart of a petrochemical plant.”

Placing the order now ensures Sasol’s equipment will be made before the market for the compressors heats up, Johan du Preez, Sasol executive vice president: US Mega Projects, said in a news release. MHI is one of the few companies that can make the compressors.

The compressor order is the latest development in the Sasol project in southwest Louisiana. On Dec. 3, the company announced it had begun the engineering and design phase of the ethane cracker, which breaks natural gas into smaller molecules to make ethylene, which is used in making plastic. Sasol plans to spend between $16 billion and $21 billion on the ethane cracker and a facility that will convert natural gas to diesel.

The plant is expected to create more than 1,250 direct jobs with an average annual salary of nearly $88,000, plus benefits. The Sasol plant will create about 7,000 construction jobs, according to estimates from Louisiana Economic Development.

The facility is expected to begin operating in 2017.

A study commissioned by LED and performed by the LSU Division of Economic Development estimates the Sasol project will have a total economic impact over the next 20 years of $46.2 billion and the project will be one of the top 10 drivers of the Louisiana economy once it is completed. Gov. Bobby Jindal’s office has said the project is the largest single manufacturing investment in the state’s history and one of the largest in U.S. history.