McKissick M-491S Series Derrick Hoist Block - 25 Ton - 1-1/8 in Wire Rope - 18 in Sheave - Roll Forged

Description du produit

The McKissick M-491S Series Derrick Hoist Block is a heavy-duty rigging block engineered for high-capacity derrick and hoist applications in demanding industrial and oilfield environments. Rated at 25 tons, this block is purpose-built for the extreme loads, continuous cycling, and harsh operating conditions encountered in derrick hoisting operations, where structural integrity, bearing performance, and sheave durability are critical to safe and efficient operation. The M-491S Series reflects McKissick's long-standing expertise in producing premium-grade hoist and derrick blocks for the most demanding segments of the rigging and lifting industry.

This block features an 18-inch sheave outside diameter and accommodates a maximum wire rope cable diameter of 1-1/8 inch. The sheave is roll forged, a manufacturing process that produces a denser, stronger grain structure compared to cast sheaves, resulting in superior resistance to wear, impact, and fatigue under the high-cycle, high-load conditions typical of derrick hoisting service. The block runs on sealed tapered roller bearings, which provide excellent radial and axial load capacity, reduced friction, and extended service life. The sealed design protects the bearing from contamination by dirt, moisture, and other environmental factors common in oilfield and heavy industrial environments, significantly reducing maintenance requirements and extending bearing service intervals.

The M-491S Series is designed for derrick hoist service where reliability under sustained heavy loads and repeated cycling is non-negotiable. The combination of a roll forged sheave and sealed tapered roller bearings represents a premium specification well-suited to continuous-duty hoisting applications in oil and gas, heavy construction, marine, and other industries where downtime is costly and equipment must perform consistently under pressure. As with all high-capacity rigging hardware, proper installation, regular inspection, and strict adherence to the rated working load are essential for safe operation.

Material:

Steel construction Roll forged sheave Sealed tapered roller bearings

Compatible With:

1-1/8 in maximum diameter wire rope cable Derrick hoisting systems High-capacity industrial and oilfield rigging configurations

Uses:

Derrick hoisting operations in oil and gas environments High-capacity industrial lifting and hoisting Heavy construction and civil engineering crane applications Marine and shipyard hoisting operations Continuous-duty high-cycle hoisting applications

Key Features:

25 ton working load capacity 18 in sheave outside diameter Maximum cable size: 1-1/8 in Roll forged sheave for superior wear and fatigue resistance Sealed tapered roller bearings for high-load performance and contamination protection Reduced maintenance requirements due to sealed bearing design M-491S Series — McKissick derrick hoist block line McKissick brand — established rigging hardware manufacturer

Note:

This product shares the same capacity, sheave size, cable size, bearing type, and sheave construction as the McKissick M-491G Series Derrick Hoist Block. The distinction between the M-491G and M-491S designations likely reflects a difference in configuration, hook type, or internal arrangement within the M-491 product family. Verify the correct series designation against the McKissick catalog or contact your McKissick distributor to confirm the right configuration for your application.