Engineered to satisfy stringent DVSA roadworthiness standards and UNECE Regulation 13 braking protocols. Explore our verified production line of pneumatic valves, chassis hardware, and axle sensors manufactured under rigorous automotive quality systems.
"In British heavy transport, unexpected pressure loss in a single pneumatic line cannot be allowed to compromise the entire braking apparatus. Our four circuit protection valves are engineered with precision bypass orifices and calibrated spring thresholds, ensuring that if one pneumatic circuit ruptures, the remaining primary and secondary circuits retain regulated holding pressure to bring multi-axle freight to a safe stop."
Commercial heavy goods vehicles (HGVs) and high-capacity buses operating in the United Kingdom rely fundamentally on compressed air to energize both service and emergency braking mechanisms. At the pneumatic epicentre of this system sits the Four Circuit Protection Valve (often designated as a Quadruple Protection Valve or Multi-Circuit Protection Assembly). Its primary architectural mandate is threefold: to distribute regulated compressed air from the air processing unit (APU) or air dryer into four isolated reservoirs, to prioritize initial charging to primary brake circuits, and to dynamically isolate any defective circuit should an abrupt rupture or catastrophic pneumatic bleed occur.
Without this valve, a puncture in an auxiliary air bellows line or a burst trailer umbilical would completely evacuate the vehicle’s main reservoirs, resulting in either complete loss of service brakes or uncontrolled, violent spring brake lockup in high-speed motorway traffic.
Feeds the primary steer axle service brake circuits. Calibrated to an initial opening pressure of 7.0 bar, securing directional steering stabilization before secondary ancillary reservoirs accept compressor delivery.
Delivers continuous pressure to rear drive and tag axle brake chambers. Operates in tight hysteresis tolerance with Circuit 21 to ensure balanced front-to-rear friction lining engagement under heavy payload.
Feeds the spring-loaded parking actuators and the red supply coupling for semi-trailers. Features integrated non-return protection ensuring trailer decoupling does not exhaust prime-mover holding pressure.
Powers pneumatic air suspension (ECAS), cabin bellows, air horns, exhaust brake valves, and gearbox splitters. Features an engineered safety closing cutoff that dumps auxiliary demand before brake reserves suffer.
Operating an articulated lorry or commuter bus in the United Kingdom places extreme, distinct physical demands on pneumatic control assemblies. From high-salinity maritime humidity to relentless urban stop-start cycling, components must survive environments distinct from continental arterial routes.
During prolonged winter maintenance along the A9, M74, and Pennine corridors, UK highway authorities apply heavy saturations of calcium chloride and crushed grit brine. Ordinary die-cast aluminum alloys suffer intense galvanic pitting and external galvanic corrosion at the exhaust seat. Our OEM/ODM valves feature electrophoretic multi-layer resin coatings and high-silicon ADC12 aluminum alloys that pass 1,000-hour continuous salt spray exposure under ISO 9227 without micro-perforation.
Rigid distribution lorries and multi-drop courier tractors navigating Greater London, Birmingham Clean Air Zones, and Manchester ring roads endure thousands of valve cycles per shift. Frequent brake applications and exhaust venting cause severe thermal swings and diaphragm rubber fatigue. Our valves incorporate vulcanized hydrogenated nitrile butadiene (HNBR) diaphragms rated from -45°C to +125°C, eliminating premature elastomeric embrittlement.
The Driver and Vehicle Standards Agency (DVSA) enforces rigorous commercial vehicle brake tests. A pressure drop exceeding 0.15 bar per minute under full pedal application causes an immediate vehicle prohibition (PG9). Our Four Circuit Protection Valves are built with lapped valve seats and computer-calibrated stainless steel internal springs that keep pneumatic leakage below 0.005 bar/min, guaranteeing 100% first-pass MOT roller brake test compliance.
Standardized pneumatic port geometry, thread tolerances, and pressure profiles mapped across leading UK commercial tractor models: DAF, Scania, Volvo, MAN, Mercedes-Benz, and Dennis Eagle.
| Part Designation | Primary OEM Cross-Ref | UK Target Vehicle Applications | Inlet / Outlet Ports | Dynamic Opening Pressure | Closing Cutoff Pressure |
|---|---|---|---|---|---|
| KNB-MAY-1668 | Wabco 934 702 041 0 / DAF 1315539 | DAF XF 105/106, CF 85, LF Series | Port 1: M22×1.5 / Ports 21-24: M16×1.5 | 7.0 bar ± 0.2 | 4.5 bar min. |
| KNB-MAY-1892 | Knorr-Bremse AE4510 / Scania 1935518 | Scania R-Series, G-Series, S-Series | Voss 232 Quick System | 7.2 bar ± 0.2 | 4.8 bar min. |
| KNB-MAY-2104 | Volvo 20546793 / Renault 7420546793 | Volvo FH12/FH16, FM9, Renault T-Range | Port 1: M22×1.5 / Voss 230 Fittings | 7.5 bar ± 0.15 | 5.1 bar min. |
| KNB-MAY-0441 | Wabco 934 702 210 0 / MAN 81521016285 | MAN TGX, TGS, Neoplan Cityliner | Metric Threads with Integrated Filter | 6.8 bar ± 0.2 | 4.3 bar min. |
| KNB-MAY-3309 | Mercedes A 001 431 71 06 / Knorr AE4528 | Actros MP4, Antos, Arocs Heavy Tipper | Voss Push-in Cartridge System | 8.1 bar ± 0.2 | 5.5 bar min. |
The British freight transport landscape is navigating monumental shifts driven by net-zero emission mandates, post-Brexit customs restructuring, and the integration of electronic air processing units (EAPUs). Fleet purchasing directors, aftermarket buying groups, and Tier-1 distributors must navigate the following operational shifts:
As electric commercial trucks (such as DAF XD Electric and Volvo Electric) penetrate UK city centers, the legacy engine-driven mechanical compressor is replaced by high-efficiency electric screw compressors. These units operate on on-demand duty cycles rather than continuous engine idling. Our modern four circuit valves are optimized with low-drag internal poppets and instant-response micro-bypass chambers, slashing parasitic pressure drop and conserving onboard kilowatt-hour battery reserves.
Modern tractor platforms deploy electronic air dryers that communicate via CAN bus with the EBS. While the electronic controller governs regenerative desiccant purge cycles, the mechanical Four Circuit Protection Valve remains the absolute safety-critical pneumatic fail-safe. If electrical ECUs fail or harness continuity drops, our mechanical pressure-retaining valves instantly take physical control to safeguard human life.
British fleet operators have suffered deep supply chain disruptions from extended Asian transit lines, Red Sea shipping diversions, and rising port handling surcharges. Manufacturing directly out of our Bursa, Türkiye automotive corridor provides British clients with 7-10 day overland road freight or rapid maritime links into UK container ports, fully supported by preferential A.TR customs agreements and simplified border declarations.
Headquartered in Nilüfer, Bursa — the heartland of Türkiye’s commercial vehicle manufacturing sector — KNB Automotive (under the legal stewardship of KNB Concept Dış Ticaret Limited Şirketi) combines heavy engineering precision with deep international logistics mastery.
Direct proximity to world-class die casting foundries, automated CNC machining complexes, and ISO/TS 16949 certified testing labs gives us unbeatable production flexibility and shortened lead times compared to typical Far East brokers.
Led personally by founder Burak Azman, our export team brings a decade of hands-on logistics, customs compliance, and parts distribution mastery. Every UK shipment arrives with complete commercial invoices, packing lists, and certified movement certificates.
Every single valve body is serial-stamped with batch production traceability. Before crating, parts endure 100% automated pressure decay diagnostics, helium leak sniffing, and spring load verification benches.
Authoritative answers to the most common technical, regulatory, and commercial inquiries received from British motor factors, commercial vehicle workshops, and logistics transport operators.
Whether you require a dedicated production run of OE-specification Four Circuit Protection Valves or wish to consolidate heavy-duty air brake replacement inventory for your UK distribution network, speak directly with our engineering desk today.