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

Tray Support is a dump body support block made by National Plastics & Rubber (NPR, Australia). It sits between the chassis rail and the rail of a raised haul truck tray, so your crew can work underneath on a dedicated support. There are 12 sizes, one per truck model (CAT, Komatsu, Hitachi, Terex and Liebherr), rated at 30 kg per cm² of rail contact.

Which Tray Support size does your haul truck need?

It depends on the make, the model and the tray. Caterpillar 793, 789, 785, 777 and 730 take Size 01 (NPR06253-00); Komatsu 830E and 930E take Size 02 (NPR05233-00); the CAT 797 takes Size 07 (NPR07678-00). The Tray Support compatibility table is a guide only: many trucks have manufacturing variations and many replacement trays differ in weight and dimensions, so NPR does not guarantee fit by model alone. Before quoting, Endeavant checks your chassis and tray rail dimensions with you.

What are the 12 Tray Support sizes and part numbers?

Each size has its own NPR part number, weight and target trucks. Where NPR user guide BRO-A-158 gives a worked example, the capacity per block is shown:

• Size 01 (NPR06253-00) — 18.5 kg: Caterpillar 793, 789, 785, 777 and 730. Guide chassis-to-tray angle 7°, 3.2 m from block to pivot. Example: 21,000 kg per block with a 20 × 35 cm tray rail.
• Size 02 (NPR05233-00) — 24 kg: Caterpillar 793 with a wide chassis rail, Komatsu 830E and 930E. 7° angle, 3.3 m to pivot. Example: 30,450 kg per block.
• Size 03 (NPR06358-00) — 21.5 kg: Terex MT4400 and Liebherr T282C. 7° angle, 3.3 m to pivot. Example: 28,800 kg per block.
• Size 05 (NPR07087-00) — 20 kg: Caterpillar 795. 5.4° angle, 4.7 m to pivot. Example: 23,100 kg per block.
• Size 06 (NPR07226-00) — 11 kg: Caterpillar 793. The lightest block in the range; set-up data is confirmed with Endeavant.
• Size 07 (NPR07678-00) — 20.5 kg: Caterpillar 797. 3° angle, about 3.84 m to pivot, 10 × 116 cm minimum contact. Example: 34,800 kg per block.
• Size 09 (NPR08172-00) — 16 kg: Caterpillar 789 (specific version). 7° angle, 3.3 m to pivot. Example: 18,000 kg per block.
• Size 10 (NPR08264-00) — 29 kg: Caterpillar 796. 10.43° angle, 3.2 m to pivot. Example: 21,000 kg per block.
• Size 11 (NPR08749-00) — 23 kg: Hitachi EH5000.
• Size 14 (NPR08542-00) — 18 kg: Komatsu HD1500 and HD785. 7° angle, 4 m to pivot. Example: 27,000 kg per block.
• Size 16 (NPR08531-00) — 15 kg: Hitachi EH4000.
• Size 17 (NPR08584-00) — 34 kg: Liebherr T264. 13° angle, 3.3 m to pivot. Example: 18,000 kg per block. The heaviest block in the range.

Every size is used with a block temperature between −50 °C and +40 °C (block, not ambient), is marked with its install orientation (TOP / FRONT) and has a handle for positioning.

How much load does a Tray Support block hold?

A Tray Support block is rated at 30 kg per cm² of contact with the narrower rail. NPR's rule: capacity per block = contact area of the narrower rail (cm²) × 30 kg. Worked example for a Size 01: with a 22 × 35 cm chassis rail (23,100 kg) and a 20 × 35 cm tray rail (21,000 kg), the block is good for 21,000 kg. With a 28 × 35 cm tray rail, the chassis rail governs and capacity becomes 23,100 kg. For full contact, chassis and tray rails must sit parallel to the block faces. Real capacity depends on your truck and must be calculated for each case.

Why use Tray Support instead of timber under the tray?

With timber, every stack is different: nobody knows its real capacity or can calculate it before stepping underneath. Tray Support is a block designed only to support trays, with a documented load calculation per size, so the maintenance crew stops guessing. For other truck components, the certified alternative to timber cribbing is Stacko™ cribbing blocks and Timba™ blocks; we compare them in our guide on how to choose support blocks for mining equipment.

One block goes on each chassis rail. With the tray resting on the blocks rather than on the hoist cylinders, those cylinders can be changed and several maintenance jobs can run at once on a stable tray.

How do you use Tray Support safely?

• 1. Risk assessment: complete one for each application, per your site's health and safety requirements.
• 2. Inspect the block: check it before every use. If it shows any damage, discard it.
• 3. Block temperature: do not use it above 40 °C or below −50 °C. This is block temperature, not ambient.
• 4. Know the load: calculate the contact area and check that the block's capacity covers the tray weight.
• 5. Even load: never a point load, with chassis and tray rails parallel to the block faces.
• 6. Lower the tray gently: an impact can generate more force than the rated capacity and damage the block.

What does Tray Support bring to the workshop?

• Documented load: each size has its 30 kg/cm² contact calculation and guide data for angle and pivot distance.
• One size per truck: the guide shows which make and series each block was designed for, and Endeavant checks your fleet's dimensions.
• Light, with a handle: 11 to 34 kg depending on size, with a handle so nobody reaches under the tray.
• Hoist cylinder changes: the tray rests on the blocks, not on the cylinders.
• Several jobs at once: the tray stays stable as a work surface while the crew works underneath.

Where can you buy Tray Support in Peru?

Endeavant S.A.C., based in Miraflores, Lima, distributes National Plastics & Rubber products in Peru, including all 12 Tray Support sizes. We help you identify the right size for your fleet from your chassis and tray rail dimensions, and calculate the load capacity for your application. In the workshop, Tray Support pairs with MineChock™ wheel chocks to immobilise the truck; the full range is in the NPR catalogue.

Tray Support FAQ