Description

Overview

Genuine Williams pressure protection valve 70psi protects auxiliary air circuits in heavy vehicle brake systems. It also helps maintain a safe air reserve for primary braking. It suits road train and trailer applications where you need to feed extra circuits without risking a full air loss. Additionally, it provides a compact way to manage pressure thresholds in complex air layouts.

Features

This valve uses a normally closed design that opens only after inlet pressure reaches the set point. As a result, downstream circuits receive air only when the main system is charged. When pressure falls below the threshold, the valve closes again and prevents further loss from the supply side. Furthermore, the built-in filter helps reduce contamination ingression from dirty air lines.

• Normally closed pressure protection function with 70psi opening point
• 1/4″ NPT inlet and outlet ports for common trailer air plumbing
• Internal filter element to reduce contaminants entering auxiliary circuits
• Compact body suited to tight mounting spaces on trailers and dollies

Specifications and Materials

Operating pressure: 70psi opening point for auxiliary circuit supply. Inlet port: 1/4″ NPT. Outlet port: 1/4″ NPT. The valve body suits industrial and vehicular air brake service where a defined minimum pressure must be maintained to protect the primary braking system. Part number: AB8431G.

For more background on how pressure protection valves work in air brake systems, see this manufacturer technical guide

Compatibility and Fitment

This cross-reference listing means this valve is a suitable replacement for the part numbers and applications shown. Some changes in air line plumbing may be required. WM778A, 118181

Compliance and Safety

Pressure protection valves play a key role in keeping enough air in reserve for service brakes. Therefore correct installation is critical. Always mount the Williams pressure protection valve 70psi in the orientation recommended by the vehicle or brake manufacturer. Additionally, you should pressure test the system after installation, check for leaks, and confirm that the protected circuits cut in and out at the expected pressure.

Trailer Applications

This Williams pressure protection valve 70psi suits heavy trailers, dollies, and road train combinations that run auxiliary circuits such as air suspensions, lift axles, or accessory tanks. When fitted correctly, it allows these systems to operate without compromising brake priority on the towing vehicle or trailer set. In addition, it fits neatly into existing 1/4″ NPT line plumbing on many fleet and OEM air layouts.

Cross-reference and Suitability

This part cross-references to or suits the following equivalent part numbers and compatible alternatives:

Use the cross-reference information as a guide only and confirm dimensions, port sizes, and pressure settings against your existing valve before final selection.

Why Choose ICS Trailers

ICS Trailers focuses on reliable air brake parts that match real transport workloads, from local rigid trucks through to full road train operations. Our team checks specifications carefully so you can select components with confidence and minimise downtime. In addition, we back our range with support that helps you match valves, fittings, and accessories across your trailer fleet.

Browse Air Brake Parts at ICS Trailers in our Air Brake Parts category