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Blackmer Bypass Valve Blackmer BV2a Bypass Valve Blackmer Bypass Valve

BV Series Bypass Valves

Blackmer® BV Series bypass valves have no small, easily plugged, sensing passages; and with only two moving parts, their operation is simple and reliable. They open precisely at the preset spring pressure, and they close smoothly and quietly, thanks to a patented dash-pot design. A small chamber in the valve stem fills with liquid when the valve opens. This liquid then provides a hydraulic cushion preventing the valve from slamming shut if pressure is suddenly released. It also minimizes chatter and valve seat wear when pressures hover around the crucial limit.

Features and Benefits

Blackmer differential bypass valves are designed to protect pumps and system components from excessive pressure damage. Blackmer offers five different models that provide full-flow pressure control to 250 U.S. gpm (946 L/min) at 120 psid (8.27 bar). Installation is easy with NPT tapped ports in sizes from 3/4- to 2-in. All models are suitable for LPG, anhydrous ammonia, CO2, among other liquids.

Performance and Specifications

In operation, Blackmer valves provide exceptionally close pressure control, even under widely varying bypass flow conditions. The Blackmer valve maintains a virtually constant pressure of 100 psi (6.89 bar) even as the volume being bypassed rises from 10 gpm to 100 gpm (38-378 L/min). Although the curve is that of a BV1.5-in valve, the precision it demonstrates is typical of any Blackmer valve.

The BV0.75, BV1, BV1.25, and BV1.5 are all UL Listed for 200 psi differential.

Bypass Valve Pressure Curve Chart


1-in & Under BV Valves

These models are commonly used for cylinder-filling system. Either valve can be used with 1.25 or 1.5-in Blackmer pump models.

Model BV0.75 

Ports are  3/4-in NPT tapped.

Model BV1 

Ports are 1-in NPT tapped.

1.25- & 1.5-in BV Valves

These models are normally used for bobtail trucks and smaller bulk plant systems. Either valve can be used with 2 or 3-in Blackmer pump models. Both valves are available with optional springs for use with the LGL158 or LGLH2.

Model BV1.25 

Ports are 1-1⁄4-in NPT tapped.

Model BV1.5 

Ports are 1-1⁄2-in NPT tapped.

2-in BV Valves

The BV2 model is widely used for transports or larger bulk plant systems. It is recommended for use with 3 and 4-in Blackmer pump models. The BV2 is factory set at 125 psi (8.62 bar).

Model BV2 

(Optional flanges: Ductile iron 2-in NPT companion, 1-1 ⁄4-in and 1-1 ⁄2-in NPT and cast steel 2-in weld. Or Stainless steel 2-in weld, 2-in weld elbow, 2-in NPT elbow)


Maximum Rated Flow* - gpm (L/min)

Pump Model 20 psi (1.38 bar) 50 psi (3.45 bar) 80 psi (5.52 bar) 120 psi (8.27bar)
25 (95) 40 (151) 50 (189) 60 (227)
60 (227) 80 (303) 100 (379) 125 (473)
150 (568) 180 (681) 220 (833) 250 (946)

*Normal maximum bypass flow rate without significantly exceeding the set pressure limit