When a plant operator faces the task of moving tons of sand or dozens of cubic meters of biomass, the choice of attachment—electrohydraulic orange peel grab or clamshell bucket—can make the difference between a smooth day and a series of stoppages and breakdowns. This article breaks down the key technical parameters that must be considered to make the right decision from the start.
First Step: Determine the Material Density
Density, expressed in kg/m³, measures the relationship between the weight of a material and the space it occupies, and therefore determines the size and strength of the equipment.
For light materials such as biomass or pruning residues (200–600 kg/m³), the priority is to maximise the bucket volume and use long-stroke hydraulic cylinders.
When the density increases to intermediate ranges, 800–1,600 kg/m³, typical of sand or gravel, a balance is required: medium-volume buckets reinforced to withstand the weight, and grabs with sufficient closing force.
For very dense materials, those above 2,500 kg/m³, such as scrap metal or rocks, the most efficient choice is compact orange peel grabs with reinforced tines and plates, capable of working at high pressures.
Granulometry: Determining Particle Size
Particle size, measured in millimetres, is a decisive factor when defining the correct shape and opening of a handling tool. Choosing the right design for the material size ensures operational efficiency and reduces premature wear of the equipment.
For fine particles, such as ash or powders, less than 4 millimetres in diameter, it is essential to use tools with sealed closures. This prevents leaks and dust clouds that could affect both the work environment and machinery.
For medium-sized materials, between 4 and 50 millimetres, such as coarse sand or chipped biomass, it is advisable to protect exposed parts such as tines and plates with wear-resistant coatings, which extend the service life of the tool.
For larger fragments, such as concrete blocks or rocks, wide-opening orange peel grabs are required, especially those reinforced at the pins and bushings. Only this type of equipment offers the robustness and reliability needed to handle heavy loads without compromising safety or structural integrity.
Facing Abrasion: Protect to Last
The abrasiveness of materials—the degree of wear they cause to steel upon contact—is a decisive factor in selecting both steel quality and protective coatings.
For low-abrasion materials, such as municipal waste or wet biomass, standard steels reinforced with light coatings are usually sufficient.
Medium-abrasion materials, typical of dry sands or soft slags, require harder, anti-abrasion steels (usually of intermediate grade), combined with additional coatings on the most exposed wear areas.
Finally, highly abrasive environments, such as those involving hard minerals or volcanic ash, require the hardest steels available and a strict preventive maintenance program to prevent unexpected failures and ensure equipment durability.
Which Equipment to Choose for Each Material?
For handling sand, a fine material with medium abrasiveness, a clamshell bucket with protective coatings on tines and plates is commonly used to extend equipment life.
When working with gravel, composed of coarser and more abrasive particles, an electrohydraulic orange peel grab with reinforced tines and hardened plates is more suitable.
In facilities that process dry biomass—light, medium-sized pieces—large-capacity buckets with fast-response cylinders are preferred to speed up loading cycles.
For municipal waste, with irregular shapes and a tendency to snag, a light orange peel grab with smooth surfaces is convenient, as it facilitates emptying without blockages.
Handling ferrous scrap requires particularly robust equipment, manufactured with anti-abrasion steel and designed to withstand hard, sharp materials.
In the case of rocky minerals, due to their hardness and large size, orange peel grabs with a high closing force, and additional reinforcements in both tines and cylinders are recommended.
Volcanic ash, excellent and highly abrasive, requires sealed buckets made of wear-resistant steel. Finally, for wet biomass—combining moisture with different fragment sizes—buckets with drainage systems and reinforced coatings are recommended to prevent sticking and extend equipment durability.
These are just some common examples of materials; the industry also handles many others, such as seaweed, salt, speciality soils, or granulated products, each with its own design and protection requirements.
Tips for Selecting and Maintaining Bulk Handling Equipment
Before choosing a biomass or seaweed handling solution, it is essential to analyse the material directly on site. Collecting real samples and measuring characteristics such as density and particle size provides more accurate data than any theoretical estimate, ensuring better equipment matching.
Maintenance should also be an integral part of the strategy from the outset. Designing a plan that includes periodic inspections and the proactive replacement of wear parts helps prevent unexpected failures and maintain uninterrupted operational productivity.
Another key aspect is hydraulic pressure adjustment. Both excessive and insufficient pressure can cause damage or inefficiency. A well-calibrated setup not only prevents breakage but also maximises the service life of hydraulic components.
Finally, modularity is particularly useful in plants that handle a variety of materials. Incorporating systems that enable quick attachment changes helps reduce downtime and increase operational flexibility.
Stemm, Engineering and Manufacturing of Grabs, Clamshell Buckets, and Clamps for All Types of Material Handling
For decades, Stemm has supplied orange peel grabs and clamshell buckets to biomass projects, ports, and water treatment facilities worldwide. If you are looking to optimise your fleet and reduce downtime, contact our technical team: turning your challenges into solutions is what we do best.
