Description

Spring Brake Relay Valve Overview

Heavy trailers rely on this spring brake relay valve for consistent parking and emergency brake control. It combines reservoir charging, pressure protection and rapid spring brake application in one compact unit. As a result, operators can maintain stable trailer braking performance under demanding conditions. The valve suits multi axle trailers that use standard NPT porting and modern air brake layouts, and it provides a durable replacement option for worn or obsolete units.

Spring Brake Relay Valve Features

• Controls trailer parking and emergency spring brake functions through a single multi function valve body.
• Supports reservoir charging while protecting the spring brakes with a defined closing pressure for consistent performance.
• Responds quickly to trailer supply line pressure loss to apply the spring brakes and secure the trailer.
• Uses common 3/8 and 1/2 NPT port sizes to simplify plumbing and replacement in existing air brake systems.

Specifications and Materials

This spring brake relay valve uses 3/8 NPT trailer supply and trailer control ports, with a 3/8 NPT delivery port configuration suited to typical multi axle trailers. It incorporates two reservoir connections, with one 1/2 NPT reservoir port and one 3/8 NPT reservoir port, and a pressure protection valve closing pressure of 70psi to help maintain a charged reservoir before releasing spring brakes.

Part number: AB8393.

Construction and internal layout follow common RT4 style multi function trailer valves used across heavy transport fleets, giving a comparable envelope and mass to other spring brake relay valves in this class. Additionally, the port layout supports straightforward mounting and air line routing on standard trailer air tanks and spring brake chambers.

See this manufacturer technical guide Haldex RT4 multi function trailer valve overview

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. KN26000, KN26010, N4302A, A88802, MIDKN26020, 1191982, 110170X, 110171X, 110180N, 110190N, 110190X, 110315X, 12360, N4305A, N4305D, N4305C, RKN26020, 5396-KN26020, 110147, 110171, 110190, 110180, A83335, A83336, A88812, AV26020, SA530, 767653010540, PP01295, RT4.

Compliance and Safety

Trailer builders and fleet operators use this style of spring brake relay valve on trailers that must meet modern brake regulations for parking and emergency control, including requirements equivalent to FMVSS 121 for spring brake operation. In correctly maintained dual line air brake systems, it works with appropriate reservoir sizing and air dryer protection to limit internal corrosion and contamination. Installers should follow current workshop safety procedures, including isolating air supply and exhausting system pressure before removal or installation, and should pressure-test the circuit after any valve replacement.

Trailer Applications

The valve suits general freight, tanker, tipper and other heavy trailer combinations that require a dedicated spring brake relay valve to control multiple brake actuators. Typically, technicians mount it on the chassis or reservoir close to the spring brake chambers to reduce line length and improve response time. Because it uses common NPT port sizes and an RT4 style layout, it can replace many existing multi function trailer valves in Australian and imported equipment when matched to the correct cross-reference numbers.

Cross-reference and Suitability

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

Users should confirm cross-reference numbers against existing parts and system drawings before final selection, particularly where trailers have been modified or rebuilt.

Why Choose ICS Trailers

ICS Trailers focuses on stocking proven air brake components that match real-world trailer applications, so you can source compatible spring brake valves without guesswork. Our team works with heavy transport operators every day, which helps ensure product information stays practical and relevant. In addition, when you need air brake parts for trailers, we aim to supply reliable options with clear specifications and local support to minimise downtime.

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