With flow rates of 31.7 CFM (53.8 m³/hr) at max rpm, the two-cylinder, single-stage NG640 Series of Gas Compressors is available in two different models, the NG642 for natural gas and the NGS642 for sour gases of up to 8% dry H₂S. Constructed with a single distance piece between two sets of seals on each piston rod, all NG Series Gas Compressors provide optimal leakage control and prevent oil contamination of the compressed gas stream. Ports are provided in the distance piece chamber for purging, pressurizing, or venting. Designed for a wide range of wellhead applications for oil and gas production and storage operations, NG Gas Compressors are equipped with a ductile iron head and cylinder, high-efficiency valves, steel pistons, self-adjusting piston rod seals and other robust features designed for quiet efficient handling of natural gas. Even in the most severe service conditions, the NG Series Gas Compressors offer the best-combined characteristics of sustained high-level performance, energy efficiency, trouble-free operation and low maintenance cost.