Conrader NG-Series Piloted Unloader Check Valve — 30 SCFM, Brass (Gas Engine Compressors)

The Conrader NG-Series is an all-in-one piloted unloader check valve for gas-engine driven piston air compressors running in continuous (constant-speed) operation. It combines three functions in a single brass body — a pilot valve, a discharge unloader valve, and a check valve — eliminating separate components and the plumbing between them.

How it works: The check valve prevents backflow as the compressor builds pressure. When downstream pressure reaches the unload setting, the pilot opens and pressurizes the unloader, venting excess air to the atmosphere so the engine runs unloaded. As air is used and pressure drops to the load setting, the pilot closes, the unloader reseats, and the cycle repeats.

Key specifications

• Max flow capacity: 30 SCFM @ 100 psig
• Unload set pressure range: 40–250 psig
• Set pressure differential: 10–50 psid
• Operating temperature: −65°F to 400°F
• Connection sizes: 1/8" to 3/4" (−2 to −12)
• Connection types: NPT, BSPT, compression, SAE 45° flare, JIC 37° flare
• Body & fittings: brass  |  poppets: reinforced PTFE  |  springs: stainless steel  |  O-rings: silicone/Viton
• Unloader outlet: muffler (standard)
• Application: gas-engine driven air compressors

Built to order

The NG-Series is available in dozens of inlet and outlet configurations and any pilot load/unload pressure setting within range. When ordering, specify your inlet/outlet connection sizes and types and your desired load and unload pressure. Optional add-ons include a hand unloader (red cap or black knob), a start unloader, an additional 1/8" or 1/4" NPT inlet port, white thread sealant, and a pilot tamper seal.

The Conrader NG-Series piloted unloader check valve is a rugged, all-brass compressor control that simplifies continuous-run gas-engine compressor packages — combining pilot, unloader, and check-valve duties in one field-proven assembly rated to 250 psig.