These heavy-duty, flanged, gas-powered suction stop valves are designed to control the flow of refrigerant in large industrial and commercial applications. They remain normally open via a spring and require no pressure drop to operate. Valves are normally installed on their side for better conveyance of liquid overfeed or oil and to avoid trapping. A single pilot solenoid valve is required to control a higher pressure refrigerant gas which closes these valves during defrosting.