Tray Support for Mining Trucks: Safety and Maintenance in Mining Operations

In open-pit mining, tray maintenance on haul trucks is one of the most delicate and highest-risk procedures. Lifting a multi-tonne tray to inspect or repair components underneath — hoist cylinders, rear suspension, hydraulic systems — demands a support system that guarantees absolute stability. Historically, mining operations have relied on stacked timber blocks, improvised welded structures, or even combinations of both, with no verifiable load capacity or documented safety factor.

Tray Support: engineered support for a specific function

The Tray Support is a high-density polyurethane support block designed exclusively to chock haul truck trays during maintenance tasks. Unlike a generic block, each Tray Support size is calculated for a specific truck model, considering the angle between chassis and tray, the distance from the pivot point, and the minimum contact area between the block and the chassis rails.

Manufactured by National Plastics & Rubber (NPR) in Australia, each block comes with a certified load capacity based on the formula: minimum contact area × 30 kg/cm². The chassis and tray rails must be parallel to the block surfaces to ensure uniform load distribution. This eliminates the uncertainty of improvised supports, where the actual capacity is unknown.

10 sizes for the largest trucks in the world

NPR offers 10 Tray Support sizes, each designed for specific haul truck models. The following shows the complete compatibility range:

• Size 01 (NPR06253-00) — 18.5 kg: compatible with CAT 793, 789, 785, 777, and 730E. Chassis-tray angle of 7°, capacity of 21,000 to 23,100 kg per block. The most versatile size, covering the majority of the CAT fleet.
• Size 02 (NPR05233-00) — 23.5 kg: compatible with Komatsu 830E, 930E, and CAT 793. Capacity of 30,450 to 32,550 kg per block. Designed for Komatsu's wider rail configurations.
• Size 03 (NPR06358-00) — 21.5 kg: compatible with Terex MT4400, Liebherr T282C, and Hitachi EH4000. Capacity of 28,800 to 30,600 kg per block.
• Size 05 (NPR07087-00) — 20 kg: designed for CAT 795. Angle of 5.4°, pivot distance of 4.7 m, capacity of 23,100 to 26,250 kg.
• Size 07 (NPR07678-00) — 20.5 kg: exclusive to CAT 797, Caterpillar's largest haul truck. Bar-type design at 116 cm long, angle of only 3°, capacity of 34,800 kg per block.
• Size 09 (NPR08172-00) — 16 kg: specific variant for CAT 789. Capacity of 18,000 to 19,800 kg. The lightest in the range.
• Size 10 (NPR08264-00) — 29 kg: designed for CAT 796. Angle of 10.43°, capacity of 21,000 to 28,350 kg.
• Size 11 (NPR08270-00) — 23 kg: compatible with Hitachi EH5000. Angle of 5°, capacity of 23,760 to 27,000 kg.

All blocks operate within the temperature range of -50°C to +40°C (block temperature) and are manufactured from polyurethane that does not absorb moisture, does not degrade with oils or fuels, and withstands prolonged UV exposure.

How Tray Support eliminates wooden cribbing

The traditional tray support procedure with timber involves stacking multiple layers of sleepers, manually checking alignment at each layer, and accepting that the actual load capacity is unknown. Each stack is different, each piece of wood has a different state of preservation, and the technician working beneath the tray trusts their safety to an uncertified material.

Tray Support replaces that entire process with a single block per side. It is positioned beneath the raised tray respecting the indicated angle between chassis and tray and the distance from the pivot point. No stacking, no unknown variables, no improvisation. Each block has a documented capacity and a defined placement procedure.

Installation procedure

• 1. Risk assessment: complete the assessment per site health and safety requirements before any operation.
• 2. Block inspection: verify that the Tray Support shows no signs of damage, cracks, or deformation. If any deterioration is found, mark as out of service.
• 3. Temperature verification: confirm that the block temperature is between -50°C and +40°C. In high-altitude mines with severe frost, blocks may require acclimatization.
• 4. Positioning: place the block ensuring that the chassis and tray rails are parallel to the block surfaces. Respect the angle and pivot point distance indicated for each size.
• 5. Controlled descent: lower the tray carefully onto the blocks. Impact can exceed the rated capacity. Distribute the load evenly; never concentrate on a single point.

Key benefits

• Certified safety: each size has a calculated and verified load capacity (minimum area × 30 kg/cm²). Technicians work beneath the tray with the certainty that the support has been designed and tested for that exact function.
• Drastic reduction in setup time: positioning a Tray Support takes minutes. Building a timber tower can take an hour or more, plus requires additional personnel for verification.
• Documented compatibility: each size indicates exactly which truck models it supports, at what angle, and at what distance from the pivot. There is no ambiguity.
• Ergonomic weight: from 16 kg (Size 09) to 29 kg (Size 10). Significantly lighter than an equivalent timber structure that can weigh 50 kg or more, reducing the risk of musculoskeletal injuries.
• Mine-condition resistant: polyurethane does not absorb moisture, does not degrade with oils or fuels, withstands UV and extreme temperatures. A timber block under the same conditions can lose up to 40% of its capacity within weeks.
• Ideal for hoist cylinder changes: provides a flat, stable working surface on the tray, allowing multiple maintenance tasks simultaneously without compromising stability.

Eliminating uncertainty

Tray Support turns a high-risk procedure into a controlled and documented operation. It's not just about meeting safety regulations — it's about giving maintenance personnel the certainty that the support they're working under has been designed, calculated, and manufactured for that specific function by an Australian manufacturer with decades of mining experience.

For mining operations in Peru working with CAT, Komatsu, Hitachi, Liebherr, or Terex fleets, Tray Support is a direct investment in personnel protection and operational continuity. Endeavant distributes the full line in Peru with technical advisory for selecting the correct size based on the truck model and operating conditions.