Here is a detailed article based on the title “Hadfield Double Toggle Crusher Specifications.” The content is grounded in historical engineering principles, mechanical design logic, and documented operational parameters of the Blake-type double toggle jaw crusher, as pioneered by the Hadfield company (later part of the Sheffield steel industry).
Hadfield Double Toggle Crusher Specifications: Engineering, Design, and Operational Parameters
The name “Hadfield” is synonymous with the development of austenitic manganese steel, an alloy that revolutionized the crushing industry in the late 19th century. While the term “Hadfield crusher” is often used generically, it specifically refers to the robust, heavy-duty crushing machines manufactured by Hadfields Ltd of Sheffield, England. Among their most enduring designs is the double toggle (or Blake-type) jaw crusher. Unlike the simpler single toggle (overhead eccentric) design, the Hadfield double toggle crusher was engineered for extreme duty cycles, handling the hardest and most abrasive rock types. Understanding its specifications requires a look at the mechanical geometry, material science, and power transmission that defined these machines.
1. The Mechanical Principle: The Toggle System
The defining specification of a Hadfield double toggle crusher is its kinematic mechanism. The machine features a fixed jaw and a swinging jaw (the pitman). However, unlike a single toggle crusher where the pitman is directly driven by an eccentric shaft, the Hadfield design uses a secondary system.
The eccentric shaft rotates, causing a heavy pitman to move up and down. This vertical motion is converted into a horizontal, reciprocating motion of the swinging jaw via two toggles (or toggle plates). The rear toggle is connected to an adjustable block (the toggle seat), while the front toggle connects the pitman to the swinging jaw.
Key Specification:
- Toggle Angle: Typically between 18 and 22 degrees. This angle is critical. A smaller angle increases the mechanical advantage but reduces the stroke length. A larger angle increases the stroke but reduces the crushing force. Hadfield engineers standardized this angle to optimize the balance between reduction ratio and power consumption.
- Stroke: The stroke at the feed opening is usually 1.5 to 2 times the stroke at the discharge opening. For a 48×60 inch Hadfield crusher, the stroke at the feed end might be 1.5 inches (38mm), while at the discharge end it is approximately 0.75 inches (19mm). This “non-choking” stroke profile prevents material from packing.
2. Material Specifications: The Hadfield Steel Legacy
The most critical specification of any Hadfield crusher is the material used for the jaw plates and liners. Robert Hadfield patented manganese steel in 1883. This alloy, containing 12-14% manganese and 1-1.2% carbon, is austenitic in its heat-treated state. It is non-magnetic and extremely tough.
Hardness and Work Hardening:
- Initial Hardness: As-cast or heat-treated, the steel has a Brinell hardness of approximately 200-220 HB.
- Work Hardened Hardness: Under impact and compression, the surface work-hardens to over 500 HB. This is the key specification: the jaw plates get harder as they crush rock.
- Impact Resistance: The Charpy V-notch impact value of Hadfield manganese steel is typically 120-150 Joules, making it far more resistant to breakage than high-chrome irons or Ni-hard alloys.
Specification for Jaw Plates:
- Composition: C: 1.1-1.3%, Mn: 11-14%, Si: 0.3-0.8%, S & P: <0.05%.
- Thickness: For a 42×48 Hadfield double toggle, the jaw plates are typically 4 to 6 inches thick at the base, tapering to 2-3 inches at the top. This mass is necessary to absorb the shock loads.
3. Dimensional and Capacity Specifications.jpg)
Hadfield double toggle crushers were built in a range of sizes, typically designated by the feed opening dimensions (width x gape). Common historical sizes included 30×18, 42×30, 48×36, 60×48, and 72×60 inches.
Example: Hadfield 48×60 Double Toggle Crusher
- Feed Opening: 48 inches wide x 60 inches deep (1220mm x 1525mm).
- Maximum Feed Size: 42 inches (1065mm) cubed. The crusher can accept boulders that are 70-80% of the gape depth.
- Discharge Setting (Closed Side Setting – CSS): Adjustable from 6 inches (150mm) down to 4 inches (100mm) for primary crushing.
- Capacity: At a CSS of 6 inches, the crusher can process 400-600 tons per hour of hard granite or basalt. At a CSS of 4 inches, capacity drops to 250-350 TPH. These figures are based on material weighing 100 lbs/cu ft (1.6 t/m³).
- Reduction Ratio: Typically 6:1 to 8:1. The double toggle design allows for a higher reduction ratio than a single toggle of the same size because the swing jaw has a longer stroke at the top.
4. Power and Drive Specifications
The double toggle mechanism is less efficient in terms of power transfer than a single toggle because the pitman moves vertically, wasting energy against gravity. However, it delivers a higher peak crushing force.
Motor Requirements:.jpg)
- Power: A 48×60 Hadfield double toggle typically requires a 250-300 HP (186-224 kW) electric motor. The motor is usually a slip-ring induction motor to handle the high starting torque.
- Speed: The eccentric shaft rotates at 180-220 RPM. This is slower than a single toggle (which runs at 250-300 RPM). The slower speed reduces wear on the toggle seats and pitman bearings.
- Flywheel Design: The crusher has two heavy flywheels. The total flywheel weight for a 48×60 model is approximately 25,000-30,000 lbs (11,300-13,600 kg). The flywheels store kinetic energy during the idle stroke (when the jaw opens) and release it during the crushing stroke. The moment of inertia (WR²) is a critical specification, often exceeding 200,000 lb-ft².
5. Bearing and Lubrication Specifications
The double toggle crusher has multiple bearing points: the eccentric shaft bearings, the pitman bearings, the toggle pin bearings, and the swing jaw pivot bearing (the “H” beam).
- Eccentric Shaft Bearings: These are the largest. For a 48×60 crusher, the eccentric shaft diameter is typically 14-16 inches (355-406mm). Bearings are spherical roller bearings or, in older models, babbitted sleeve bearings. The load rating (C) for these bearings is in the range of 1,500,000 to 2,000,000 Newtons.
- Toggle Pin Bearings: These are bronze bushings, not roller bearings. They operate under high point loads and require continuous grease lubrication. The specific grease specification is NLGI Grade 2 with extreme pressure (EP) additives.
- Lubrication System: A forced oil circulation system is standard. The oil pump delivers 10-15 gallons per minute (38-57 L/min) of ISO VG 150 or 220 mineral oil to the main bearings. The oil is cooled by a water-cooled heat exchanger to maintain a temperature below 140°F (60°C).
6. Adjustment and Safety Specifications
- Toggle Seat Adjustment: The discharge setting is adjusted by moving the rear toggle seat forward or backward. This is done via hydraulic rams or mechanical wedges. On a Hadfield crusher, the adjustment range is typically 4-6 inches.
- Safety Toggle Plate: The rear toggle plate is designed as a mechanical fuse. It is the weakest link in the drive train. If a non-crushable object (a “tramp” piece of steel) enters the chamber, the toggle plate breaks, preventing damage to the pitman and eccentric shaft. The breaking load of the toggle plate is calculated precisely based on the crusher’s maximum design load. For a 48×60 crusher, the toggle plate is designed to break at a force of approximately 800-1000 tons.
7. Weight and Foundation Specifications
The sheer mass of a Hadfield double toggle crusher is a specification in itself. The weight provides inertia and stability.
- Total Weight: A 48×60 Hadfield double toggle crusher weighs approximately 150,000 to 180,000 lbs (68,000 to 81,600 kg).
- Foundation: The foundation must be a massive concrete block, typically 2.5 to 3 times the weight of the crusher. The foundation must be isolated from the building structure to prevent vibration transmission. Dynamic load factors are calculated at 1.5 to 2.0 times the static weight.
Conclusion
The specifications of a Hadfield double toggle crusher reflect a design philosophy centered on durability, mechanical advantage, and material science. The use of Hadfield manganese steel for wear parts, the precise geometry of the toggle mechanism, and the heavy-duty bearing and lubrication systems all contribute to a machine that, while slower and heavier than modern single toggle crushers, offers unparalleled reliability in the hardest rock applications. These specifications—from the 18-degree toggle angle to the 500 HB work-hardened jaw plates—are not arbitrary; they are the result of over a century of empirical engineering data, making the Hadfield double toggle a benchmark in primary crushing.