Manufacture of electric steel is characterized by essentially non-uniform consumption of oxygen under pressure 12-14 bar. For reliable maintenance by oxygen on metallurgical manufacture applies piston compressors for filling of recipients by it under pressure up to 35 bar. The oxygen regulating factory’s station using oxygen from air separation plant and recipients, allows to submit it in to furnace of electric steel heat under the required schedule, despite of significant changes of expenses. Reliability and power parameters of such technological circuit depend on corresponding characteristics of oxygen piston compressors. The characteristic of three compressors «4М10-40/35» and one compressor «4D225-3D» used in the circuit are considered in comparison. It is paid attention to higher reliability and pro-fitability of compressor «4D225-3D» in comparison with three others. Original design features of compressor «4D225-3D» which provide high values of its characteristics are described. The maintenance of service and repairs of this compressor continuously working on the Moldavian metal works more 11th years is stated.