Ball Mill Trunnion Forgings — The Rotating Shaft Supporting a Mineral Grinding Mill's Full Charge Weight on Its Bearing System
Shivam Forge manufactures forged trunnion shaft components for ball mills and rod mills — the large-diameter rotating shaft, integral or bolted to the mill shell head, that supports the mill's entire rotating mass (shell, grinding media, and mineral charge) on its trunnion bearings while also serving as the feed or discharge passage for material flow. Mineral processing and cement industry applications. Rajkot, India. Call +91-9265772827.
A ball mill trunnion is among the largest single forged shaft components used in mineral processing and cement grinding equipment, and its engineering challenge is defined by scale as much as by loading complexity: the trunnion is the shaft extending from each end of the mill shell that seats into the trunnion bearing, and through that bearing interface it must support the combined static and dynamic weight of the entire rotating mill assembly — the steel shell itself, the tonnes of grinding media (steel balls or rods) loaded inside it, and the mineral feed charge being ground — while also transmitting whatever torque reaction and, on many designs, providing the hollow bore through which feed material enters or ground product discharges. This combination of enormous supported mass, continuous rotation under that load, and in many designs a functional through-bore that removes material from the shaft's cross-section exactly where bending stress from the supported weight is highest, makes trunnion design and manufacture a genuinely demanding forging application: the shaft must be forged from a single sound billet large enough to produce the finished trunnion's diameter and length without defects, since any internal discontinuity in a component supporting this much static and cyclic bending load risks a failure that would stop an entire grinding circuit and, given the trunnion's size, require an extended replacement lead time measured in months rather than days. This is precisely why mill trunnions are sourced from forge suppliers capable of both the large-billet forging capacity and the ultrasonic testing rigor needed to verify soundness through a section this substantial.
Forged feed-end trunnion shaft blanks incorporating the feed inlet bore geometry, supporting the mill's rotating mass on the feed-side trunnion bearing while providing the passage for incoming mineral feed and, on some designs, grinding media.
Forged discharge-end trunnion shaft blanks supporting the mill on the discharge-side trunnion bearing while incorporating the bore geometry through which ground product exits the mill shell.
Forged trunnion shaft components sized for rod mill applications, where the specific grinding media and shell geometry differ from ball mills but the trunnion's fundamental load-bearing and material-passage function remains the same.
Forged trunnion components for cement grinding mills and mineral processing ball mills across ore types, sized to the specific mill diameter, shell weight, and charge capacity of the target application.
Trunnion shafts forged from a single sound billet sized to produce the finished component's full diameter and length, avoiding the internal soundness risk that welded or built-up construction would introduce in a component under this much bending and torsional load.
Ultrasonic testing verifying internal soundness through the trunnion's full cross-section, essential given the component's large diameter and the severe consequence of an undetected internal discontinuity in a shaft supporting this much static and cyclic load.
Precision dimensional control on the trunnion bearing journal surface, since journal roundness and surface finish directly affect trunnion bearing wear life and the mill's rotational stability under its full supported load.
Complete dimensional inspection and material certification to EN 10204 3.1, supporting the traceability requirements of mill OEMs and mineral processing and cement plant operators.
Ball mills and rod mills sit at the center of mineral processing and cement grinding circuits, reducing ore, clinker, or other feed material to the fine particle size downstream processing requires by tumbling it inside a rotating steel shell together with a substantial charge of grinding media. The scale of this equipment is considerable — mill shells can run several meters in diameter and carry hundreds of tonnes of combined shell, media, and feed weight — and every bit of that rotating mass is ultimately supported through just two points: the trunnion shafts extending from each end of the shell, seated in their respective trunnion bearings. This makes the trunnion one of the most structurally critical single components in the entire grinding circuit, despite receiving comparatively little attention next to the mill shell, liners, or drive system that more visibly define the equipment.
The trunnion's engineering demand comes from the combination of scale and geometry it has to satisfy simultaneously: it needs to be forged large enough in diameter to support the mill's full rotating weight with adequate margin against both static bending load and the cyclic stress that continuous rotation under that load introduces, while on many mill designs it also needs to incorporate a hollow bore serving as the feed inlet or product discharge passage. That bore is not a minor manufacturing convenience — removing material from the shaft's cross-section at the location where supported-weight bending stress is highest is a genuine structural tradeoff, and trunnion forging and design practice has to account for it directly rather than treating the bore as an afterthought machined into an otherwise solid shaft design.
Because a mill trunnion is forged as a single large-diameter component from a correspondingly large billet, verifying its internal soundness through the full section is not a routine quality step but a genuinely load-bearing part of the manufacturing process: any internal discontinuity carried through from the original billet or introduced during forging represents a latent structural weakness in a component that will spend its service life under continuous, substantial bending and torsional load. Given that a trunnion failure stops the entire grinding circuit and that replacement lead time for a component this large is typically measured in months given the scale of billet procurement and forging capacity required, full-section ultrasonic testing before a trunnion ever ships is treated as essential rather than an optional add-on to the quality package.
For mill OEMs and mineral processing and cement plant operators sourcing forged ball mill or rod mill trunnion shafts, Shivam Forge manufactures from single sound billets sized to your mill's diameter and shell weight, with full-section ultrasonic testing and bearing journal precision matched to your trunnion bearing specification. Contact our engineering team at +91-9265772827 or sales@shivamforge.com with your drawing or mill specification for a manufacturability review and quotation.
The trunnion, through its bearing interface, supports the mill's entire rotating mass — the steel shell itself, the full tonnage of grinding media (steel balls or rods) loaded inside, and the mineral feed charge being processed. On large industrial mills this combined weight runs into hundreds of tonnes, all carried continuously through the trunnion shaft as the mill rotates.
On many mill designs the trunnion incorporates a through-bore for feed or discharge material flow, and that bore removes material from the shaft's cross-section at exactly the location where bending stress from the supported mill weight is highest. Trunnion design and forging practice has to account for this directly, since the bore geometry genuinely affects the shaft's structural capacity, not just its function as a material passage.
A mill trunnion is one of the largest single shaft forgings used in mineral processing equipment, and an undetected internal discontinuity in a component under this much continuous static and cyclic bending load risks a failure that stops an entire grinding circuit. Given the trunnion's size, replacement lead time on a failure is typically measured in months, not days, which is why full-section ultrasonic testing is treated as essential rather than optional on these components.
Yes. Forged trunnion shaft components are available for both ball mill and rod mill applications, sized to the specific mill diameter, shell weight, and grinding media and charge capacity of your target application.
Mineral processing operations grinding ore (copper, iron, gold, and other minerals) and cement plants grinding clinker both rely on ball mills with forged trunnion shaft components, and we supply trunnions sized to the specific mill diameter and duty requirements across both industries.
Why Choose Shivam Forge
Shivam Forge delivers precision hot-forged components from our integrated Shapar, Rajkot facility — covering forging, CNC machining, heat treatment, and quality inspection under one roof.
