Pfaff-Silberblau DSRB Wire Rope Pulley Block

Model DSRB | SWL 700 kg – 2,500 kg (at 90° deflection) | Ball-Bearing Sheave | 90° or 180° Rope Deflection | Base-Mounted | Doubles Winch Pulling Capacity | CE & UKCA Marked | Made in Germany

The Pfaff-Silberblau DSRB is a heavy-duty base-mounted wire rope pulley block (Rollenbock) used to deflect a winch rope through 90° or 180°, redirect the working line to suit the lifting geometry, or rig the rope through the block to double the pulling capacity of the connected winch. The DSRB is a passive deflection sheave — it has no drive of its own; rated capacity is the maximum force the sheave and its base can carry from the deflected rope. Five standard sizes cover safe working loads from 700 kg up to 2,500 kg at 90° deflection (and up to 1,800 kg at the more demanding 180° deflection geometry). The sheave runs on heavy-duty ball bearings for smooth low-friction rope passage at full rated load, and each block carries an FEM/ISO classification (2m/M5, 1Am/M4, or 1Dm/M1) that defines the design duty cycle category.

Technical Specifications

SWL at 90° is the safe working load when the rope deflects through a 90-degree angle around the sheave (the standard rigging configuration for repositioning a winch rope). SWL at 180° is the safe working load when the rope deflects fully — used when rigging the block to double the pulling capacity of the connected winch. The 180° rating is always lower than the 90° rating because the rope applies its full force in both directions on the sheave bearing. The model number reflects the sheave diameter and minimum rope diameter the block is designed for (e.g. S 90/4 = 90 mm sheave for 4 mm rope; S 270/12 = 270 mm sheave for 12 mm rope).

Key Features

• Ball-bearing sheave: Heavy-duty ball bearings give smooth low-friction rope passage at full rated load — significantly more efficient than a plain bearing sheave, and lower wear on both rope and sheave groove.
• Two deflection options: Rope can be rigged through the block at 90° (for redirection) or 180° (for capacity doubling); the SWL differs between these two geometries and is published per model.
• Capacity doubling: Rigging the winch rope through the block so it deflects 180° back to the load doubles the effective pulling capacity of the winch (with a corresponding halving of the lifting speed) — the standard mechanical advantage of a single-sheave block.
• Base / foot mounting: Designed for fixed-position installation on a structural mounting plate or anchor point. Not for swinging suspension from a hook.
• Suitable for manual and motorised operation: Compatible with hand-cranked Pfaff winches (Alpha, GAMMA, LAMBDA, MWS, SW-W, LB, KAL) and motorised Yale winch ranges (RPE, CPE, VTEU).
• FEM / ISO classified by duty cycle: Each block carries a classification (2m/M5, 1Am/M4, 1Dm/M1) defining the acceptable design duty cycle — match the classification to the application's load spectrum and cycle count.
• Five sheave sizes: 90 mm, 145 mm, 185 mm, and 270 mm sheave diameters cover rope diameters from 4 mm up to 12 mm.
• Capacities up to 8 t at 90° / 5 t at 180°: The Pfaff DSRB range extends beyond the five standard variants listed here, with larger blocks available on request for heavy-duty applications.

Suitable Applications

The Pfaff-Silberblau DSRB is the standard wire rope deflection sheave used alongside Pfaff and Yale wire rope winches across industrial lifting, marine, sailing centre, construction site, and rigging applications. Typical uses include redirecting a winch line around a corner or column where the winch and load cannot be in line; doubling the pulling capacity of a winch by rigging through the block (1,000 kg winch + DSRB = 2,000 kg pulling capacity, half speed); rigging high-line installations where the winch is at ground level and the load needs to be lifted vertically from an overhead point; sailing centre boat hoists where the rope must turn under a launching jetty; theatre and event rigging where deflection geometry varies between productions; and structural lifting on construction sites where the winch mount and load lift point cannot be coincident. The S 90 size suits light Pfaff winches (Alpha 300 / 500, MWS 150 / 300, SW-W up to 750 kg); the larger S 145 / 185 / 270 are specified for heavier winches and motorised applications.

How to Use the Pfaff-Silberblau DSRB

1. Verify the application capacity: Confirm the working load is within the SWL for the rigging geometry — 90° or 180°. The 180° rating is significantly lower; use the published 180° SWL for capacity-doubling applications.
2. Verify the FEM / ISO classification: Confirm the block's classification (2m/M5, 1Am/M4, 1Dm/M1) is appropriate for the duty cycle. High-cycle applications need higher-classification blocks.
3. Verify the mounting: The block must be mounted on a structural base capable of supporting the SWL plus an appropriate safety factor. The mounting must resist forces in the direction of the resultant rope tension — not just the load force.
4. Verify rope diameter match: Confirm the rope diameter matches the sheave size (e.g. S 90/4 takes 4 mm rope; S 270/12 takes 12 mm rope). Undersized rope on an oversized sheave will deform under load; oversized rope will not seat correctly in the groove.
5. Rig the rope through the block: Feed the rope around the sheave such that it deflects at the intended angle (90° or 180°). The rope must seat fully in the sheave groove — visually confirm this before applying load.
6. Apply load gradually: Start the lift slowly and verify the block remains stable on its mount and the rope tracks correctly in the sheave.
7. For capacity doubling: The free end of the rope (after deflection through the block) is anchored to a fixed point; the load is attached to the moving block or directly to the doubled rope, giving 2:1 mechanical advantage between winch and load.

Warning: Pulley blocks are passive deflection devices — they have no brake or holding mechanism. The connected winch must always hold the load. Never exceed the SWL for the rigging geometry actually in use. Side-loading the block or rigging at an angle other than the intended 90° or 180° applies forces the block is not designed for.

Safety Information

• Verify the base mounting is rated for the resultant force direction and magnitude — not just the load force.
• Use the SWL appropriate to the rigging geometry — 90° rating for redirection, 180° rating for capacity doubling.
• Match rope diameter to sheave size; undersized rope on an oversized sheave is dangerous.
• Confirm the FEM / ISO classification is appropriate for the duty cycle before committing to high-cycle use.
• Inspect the sheave bearing for free rotation before each lift — a seized bearing causes severe rope wear.
• Inspect the sheave groove for wear; deep grooving or sharp edges damage the rope.
• The block has no brake — the connected winch holds the load. Never expect the block to hold load if the winch fails.
• Workplace operators must establish a Thorough Examination regime under LOLER 1998 for lifting accessories at intervals not exceeding 12 months.

Inspection and Maintenance

The DSRB requires periodic inspection of the sheave bearing (free rotation without grinding, no excessive play), the sheave groove (no deep wear, sharp edges, or cracks), and the base mount (structural integrity, no impact damage or distortion). Replace the block immediately if the sheave shows cracks, severe groove wear, or bearing failure. The ball bearings in the sheave are sealed and typically maintenance-free over the design service life; if play develops, the block is at end-of-life. Routine cleaning to remove rope debris, grit, and any chloride deposits (in marine and pool environments) extends service life. WOLFF Onsite provides LOLER-certified Thorough Examination, replacement blocks, and rigging consultancy for the Pfaff-Silberblau DSRB range.

Optional Accessories

• Matched wire rope assemblies: Wire ropes sized to match the DSRB sheave size (4 mm – 12 mm), pre-terminated with eyehooks.
• Reinforced mounting plates: Heavy-duty mounting plates for installation on structures not designed to take the resultant forces directly.
• Rope-end terminations: Pressed or swaged eye terminations, shackles, and load-rated end fittings.
• Larger DSRB capacities on request: Sizes beyond the five standard variants up to 8 t at 90° / 5 t at 180° are available — contact our team.

Downloads

• OEM datasheet not currently published on the CMCO portal for this family. Contact WOLFF Onsite for the specific datasheet for any DSRB variant you intend to specify.

Frequently Asked Questions