Description

Overview

This relay valve four delivery ports unit provides fast, balanced control of trailer service brakes on road train combinations. It mounts close to the brake chambers so it can respond quickly to control signals from the foot valve. As a result, it reduces brake lag and helps keep brake applications even across multiple axles.

Features

This relay valve four delivery ports design uses a main supply port and four 3/8″ NPT delivery ports to feed several brake chambers at once. Additionally, a separate 1/4″ NPT control port allows the service signal to arrive cleanly from the primary valve. The 3 psi crack pressure helps the system build line pressure smoothly instead of snapping on. Furthermore, 3/8″ mounting holes on 2-1/2″ centres give a stable mounting footprint on standard brackets.

Specifications and Materials

Part number: AB8428.
This relay valve four delivery ports unit suits heavy vehicle air brake systems that use NPT threaded connections. The supply port A uses 3/4″ NPT, while the B supply port remains plugged in this configuration. In addition, the single 1/4″ NPT control port and four 3/8″ NPT delivery ports support typical road train plumbing layouts. The crack pressure rating of 3 psi suits many trailer service brake circuits where controlled, early response is important. For an overview of relay valve operation in air brake systems, see this manufacturer technical guide on air brake relay valves for further technical context.

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.
AF103600, A103600, 103600, RV030, CA43.

Compliance and Safety

Correct installation of this relay valve supports compliance with heavy vehicle brake performance expectations when used in a properly engineered system. Always follow recognised air brake plumbing diagrams and torque settings, and ensure all NPT threads use suitable thread sealant that does not enter the air passages. Additionally, installers should leak-test all joints after fitting and verify that the relay exhaust port remains clear of road spray, debris and moving parts. Finally, confirm that the relay operation matches the brake manufacturer’s guidelines before returning the trailer to service.

Trailer Applications

This relay valve with four delivery ports suits road train trailers and other heavy combinations that need one control valve to feed several brake chambers on a group of axles. In many cases, it will sit near the axle group so it can shorten air line runs to the service chambers. Consequently, it can help maintain more even brake balance between the lead trailer and following units. In addition, its NPT port layout and 3 psi crack pressure make it a practical choice for upgrades or maintenance on common Australian trailer brake systems where a four-port relay is specified.

Cross-reference and Suitability

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

Why Choose ICS Trailers

ICS Trailers focuses on practical, proven components for heavy trailer air brake systems, so you can match parts to real fleet requirements with confidence. Our team checks cross-reference data carefully and selects parts that suit local conditions and regulations. Moreover, we back our range with product support and straightforward advice to help keep your equipment working reliably. Browse Air Brake Parts at ICS Trailers