The Cast Air BLG is the high-flow pilot valve for gas engine-driven compressors that need a 1/2" NPT control circuit. It is the gas engine counterpart to the electric-application BLE — same 1/2" NPT-F inlet and outlet, same 60 CFM flow capacity, same hex brass body, but rated and configured for gas engine compressor applications. At $147.84, it is the top of the Cast Air pilot valve lineup, reflecting both the larger port size and the gas engine-specific design requirements.
If you are running a large trailer-mounted or stationary gas engine compressor — the kind used in oilfield, construction, or heavy industrial service — and the pilot valve that controls the load/unload cycle has failed, sticks, or is hunting between states, this is the replacement part to source. The external adjustment makes it possible to dial in both cut-in pressure and differential without pulling the valve off the compressor.
What the BLG Does
- Application: Gas engine-driven air compressors — manages the pilot signal controlling loading and unloading on larger gas engine compressor systems
- Valve Type: 2-way pilot valve — two ports, one function per signal, reliable and straightforward to troubleshoot
- Inlet: 1/2" NPT-F — threads directly into standard 1/2" NPT manifold or control circuit ports
- Outlet: 1/2" NPT-F — full-size outlet preserves flow capacity; no restriction through the valve body
- Pilot Port: 1/4" NPT-F — appropriately sized for the higher-flow pilot circuit this valve manages
- Flow Capacity: 60 max CFM — handles the control circuit demands of larger gas engine compressor systems without starving the signal
Construction and Adjustment
- Body: Hex brass — corrosion-resistant, robust connection threads, holds up in the field environments where gas engine compressors typically operate
- Pressure Adjustment: Full external pressure adjustment — set the actuation pressure at the valve without removing it from the system; critical for field service where disassembly is not always practical
- Differential Adjustment: Full external differential adjustment — tune the spread between cut-in and cut-out to match engine speed recovery characteristics; prevents short-cycling that wears engine and compressor components prematurely
- Pressure Range: 40–250 PSI available; most gas engine compressor applications in this flow class order the 100–120 PSI or 140–170 PSI versions — confirm working pressure before specifying
- Corrosion Resistance: Corrosion-resistant construction throughout — built for the outdoor and field environments where trailer-mounted gas engine compressors live
Where This Valve Fits
- Replacement pilot valve on large gas engine compressors with 1/2" NPT control circuit ports
- New builds for industrial or oilfield gas engine compressor installations requiring a full 60 CFM pilot valve
- Field service replacements where the original valve has failed in service — the external adjustments let you set it correctly on-site without a workbench
- Not for electric compressor applications — the BLE covers 1/2" NPT, 60 CFM electric applications
- Not for 1/4" NPT gas engine circuits — the BG2-M (20 CFM) handles those applications at a lower cost
BLG vs. the Cast Air Pilot Valve Lineup
- BG2-M — $78.54: 1/4" NPT-F, 20 CFM, gas engine — smaller gas engine compressors with 1/4" control ports
- BLE — $123.20: 1/2" NPT-F, 60 CFM, electric dual — same port size and flow, electric application
- BLG (this valve) — $147.84: 1/2" NPT-F inlet and outlet, 1/4" NPT-F pilot, 60 CFM, gas engine — largest in the lineup, highest flow, gas engine rated
- BE2-M — $91.63: 1/4" NPT-F, 20 CFM, electric dual — for reference on the smaller electric side
Before ordering the BLG versus the BG2-M, check your control circuit port size at the compressor. Gas engine compressors vary considerably in how the pilot circuit is ported — a 1/4" port means the BG2-M, a 1/2" port means the BLG. Getting that right the first time avoids bushing adapters and potential flow restriction in the control circuit.
Technical Specifications
- SKU / Part Number: BLG
- Manufacturer: Cast Air (Castair)
- Valve Type: 2-Way Pilot Valve
- Application: Gas Engine
- Inlet Port: 1/2" NPT-F
- Outlet Port: 1/2" NPT-F
- Pilot Port: 1/4" NPT-F
- Maximum Flow: 60 CFM
- Pressure Range: 40–250 PSI (specify range at order)
- Common Range Orders: 100–120 PSI or 140–170 PSI
- Body Material: Hex brass
- Adjustment: External pressure and differential adjustment
- Price: $147.84
Why Buy From Air Compressor Factory Direct?
- Specialist since 2016 — gas engine compressor parts are a known category for us; we can help you match the correct pilot valve to your specific compressor configuration
- Free shipping on orders to the contiguous US
- Free tech support at 866-217-0063 — call with your compressor specs and port sizes before ordering if there is any uncertainty about which valve fits
- Full manufacturer warranty — Cast Air warrants their parts; we process warranty replacements without delays
- Full lineup stocked — we carry all four Cast Air pilot valve models so you get the correct part matched to your application, not a substitute
Call 866-217-0063 for quick answers and help!
