A tyre baler that produces PAS 108-compliant bales is not simply a machine that squeezes tyres into blocks. It is a piece of precision manufacturing equipment whose dimensional configuration, compressive force specification, tying system design, and control parameters are all derived from the PAS 108 specification requirements. The connection between machine specification and bale compliance is direct and quantifiable: change one and you change the other.
Understanding how the Gradeall MKII Tyre Baler’s technical specification maps to PAS 108 requirements is valuable both for operations establishing PAS 108 production and for those reviewing whether their existing equipment can reliably achieve compliance. It also provides context for why machine maintenance is not separable from production quality: a machine that has drifted from its original specification through wear or neglect cannot consistently produce compliant bales regardless of how carefully it is operated.
The MKII Tyre Baler is Gradeall’s flagship tyre baling machine, manufactured at the Gradeall International facility in Dungannon, Northern Ireland and exported to operations in over 100 countries. The headline specification:
The machine is also available with optional conveyor integration through the inclined tyre baler conveyor and the TBC8M tyre baler conveyor, which automate the tyre loading function for high-volume operations.
The baling chamber is the structural element of the MKII that defines the length and width of the finished bale. The chamber’s internal dimensions determine two of the three key bale measurements; only the height (compression direction) dimension is variable and controlled by the number of tyres loaded and the compression force applied.
The MKII’s baling chamber is configured to produce bales within the dimensional targets and tolerances of PAS 108. This configuration is not a manufacturing preference; it is a deliberate design decision that makes the machine suitable for PAS 108 production. A baler with a chamber configured to different dimensions produces bales of different dimensions that may or may not fall within PAS 108 tolerances.
The chamber walls are fabricated from structural steel plate to resist the compressive forces generated during the baling cycle. Wear of the chamber walls over the machine’s service life can alter the internal dimensions. Chamber wear inspections at scheduled maintenance intervals identify dimensional drift before it affects bale compliance. For operations with LOLER requirements, the annual thorough examination provides an opportunity to assess chamber condition alongside the hydraulic system inspection.
The hydraulic compression system is the most critical element for PAS 108 compliance because it determines the compressive force applied to the tyre load, which in turn determines the density of the finished bale.
The MKII’s single hydraulic ram applies top-down compression force to the tyre load in the baling chamber. The hydraulic system is designed to deliver the compressive force needed to achieve PAS 108’s minimum density requirement from a correctly loaded chamber of car or truck tyres.
The key parameters:
Hydraulic working pressure. The system operates at a working pressure that delivers the specified compressive force at the ram. This pressure is set and tested at manufacture and should be verified against specification at regular maintenance intervals. A hydraulic system that has lost pressure through pump wear, seal deterioration, or valve leakage will not achieve the specified compressive force and will produce under-compressed bales.
Platen area. The compressive force is applied through a platen whose area determines the pressure applied to the tyre load. The MKII’s platen is sized to the chamber cross-section to ensure even force distribution across the full bale area.
Cycle control. The hydraulic cycle is controlled by the MKII’s programmable control system, which manages the compression stroke, pressure hold at the end of stroke, and platen retraction in the tying position. The pressure hold at end of stroke is important: it ensures the tyre load is compressed to the full specified force before the tie wire cycle begins, not just momentarily at the peak of the compression stroke.
Hydraulic fluid specification. The MKII hydraulic system uses ISO VG 46 hydraulic oil. Operating with incorrect fluid grade affects viscosity and therefore system pressure and flow rates. Annual fluid changes with the correct specification fluid are part of the maintenance schedule.
The six-wire automatic tying system is the element that holds the bale within its compressed dimensions after the platen retracts. A bale that achieves the correct density at peak compression but then expands because the ties are inadequate is a non-compliant bale when it leaves the machine.
The MKII’s tying system applies six wire ties at evenly spaced positions across the bale width. The tie positions are fixed by the tying needle geometry. Six ties at the correct positions represent the PAS 108 minimum tie requirement; this is not a coincidence. The MKII’s tying system was designed to meet the standard’s requirement.
Wire specification. The tie wire used in the MKII must meet the tensile strength and gauge specification for which the machine and the PAS 108 requirement were calibrated. Using under-gauge wire, or wire with lower tensile strength than specified, allows the ties to stretch or fail after bale ejection, resulting in bale expansion. Gradeall’s baler wire range, including baler wire for the MKII, is specified for the machine and the application.
Needle position verification. The tying needles that carry wire through the bale at the tie positions must return to their reference position accurately on every cycle. Needle wear or misalignment causes ties to be applied at positions other than those required, potentially concentrating restraint force at the centre of the bale and leaving the ends under-restrained. Needle position inspection at maintenance intervals is standard.
The MKII’s programmable control system manages the baling cycle and provides the operator with feedback on cycle status. For PAS 108 production, the control system’s role in maintaining cycle consistency is significant.
The control system manages the timed sequence of: tyre loading (door interlock), compression stroke, pressure hold at end of stroke, tying cycle, platen retraction, and bale ejection. Deviations from this sequence (premature retraction before full pressure is achieved, tie cycle skipping, loading door interlock bypass) all produce non-compliant bales.
The system’s fault monitoring detects conditions such as wire break in the tying cycle, limit switch failures, and hydraulic pressure anomalies. These faults are flagged to the operator rather than allowing a defective bale to be completed and ejected without detection. Reviewing the fault log at shift start and end is a simple quality management practice that identifies systematic issues before they affect a significant number of bales.
A new MKII Tyre Baler produces PAS 108-compliant bales when operated correctly. Keeping it producing to specification over years of operation requires the maintenance schedule to be followed.
The maintenance items that most directly affect PAS 108 compliance:
Hydraulic pressure testing. Annual testing of system pressure against the rated specification confirms the hydraulic pump and valves are maintaining the force needed for compliant compression. Pressure drift below specification is the single most common cause of production quality problems in baling equipment.
Wire feed system service. Annual inspection and service of the needle position, wire tensioning, and feed mechanism. Tie position accuracy is a PAS 108 requirement; maintaining the tying system to specification maintains compliance.
Chamber dimensional inspection. Periodic inspection of the chamber walls for wear or deformation. Significant chamber wear alters bale geometry.
Control system calibration. Verification that the pressure hold and cycle timing parameters remain at their set values.
Gradeall provides technical support and service documentation for the MKII. Contact Gradeall International for maintenance scheduling guidance and for the full tyre recycling equipment range including pre-processing equipment.
The MKII’s ability to produce PAS 108-compliant bales depends on receiving tyres that have been correctly pre-processed. The machine cannot compensate for incorrect tyre input.
Rim-free tyres only. A rimmed tyre in the MKII’s baling chamber damages the equipment and produces a non-compliant bale. All rimmed tyres must be processed through the tyre rim separator or truck tyre rim separator before entering the baler.
Sorted tyre types. Car and truck tyres are baled separately. Mixed loads produce inconsistent bale properties.
Sidewall-cut truck tyres. Truck tyres should be processed through the truck tyre sidewall cutter before baling to achieve consistent density compliance.
“The MKII is designed to produce PAS 108-compliant bales,” says Conor Murphy, Director of Gradeall International. “But the machine and the pre-processing line work as a system. You can’t expect consistent compliance from the baler if the tyre input isn’t properly prepared. The investment in the full pre-processing and baling line is the investment in consistent civil engineering supply.”
No. Only a baler whose chamber dimensions, compressive force specification, and tying system configuration are designed to meet PAS 108 requirements can produce compliant bales. A machine with a smaller chamber, lower hydraulic pressure specification, or fewer tie positions will not produce compliant bales regardless of how it is operated.
Annual hydraulic pressure testing against the rated specification, combined with regular bale dimension and mass monitoring in production, provides ongoing confirmation. If bale density or dimensions are drifting from the target, the hydraulic system is the first place to investigate.
Up to 6 PAS 108-compliant bales per hour is the MKII’s rated output. In practice, output depends on tyre loading rate, operator familiarity, and pre-processing line throughput. Well-configured operations with conveyor integration typically achieve output rates close to the rated specification consistently across a shift.
Yes. The MKII handles both car and truck tyre bale production. For truck tyre bales, the truck tyre sidewall cutter is an essential pre-processing step for consistent density compliance. Car and truck tyres are baled separately using different per-load tyre quantities.
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