WPWO Worm Gearbox | Output-Flange WP Series Worm Reducer

WPWO — The Flange-Mount Variant of the WP Worm Gearbox Family

The WPWO is the output-flange variant of our WP-series cast-iron worm gear reducer. Where the WPWDKS configuration drives a load through a keyed solid output shaft, the WPWO presents a hollow output bore with a bolted PCD flange face — the gearbox bolts directly onto the load housing rather than connecting through a coupling. Common targets include vertical pump bodies, mixer assemblies, screw-conveyor drive ends, slewing-ring drives on small cranes, and any application where the driven machine carries its own input shaft and the gearbox is designed to mate flush with it.

The WPWO worm gear reducer covers a wider torque envelope than any other WP variant in our catalogue: 19 Nm at the smallest WPWO50 frame at i=5, scaling all the way to 2,745 Nm at the WPWO250 frame at i=60. Rated input power runs from 0.12 kW (a small mixer auxiliary) up to 33.2 kW (a heavy bag-house screw conveyor). Output speeds span 19 rpm to 186.7 rpm from a 1,400 rpm input — the natural range for slow-speed industrial machinery. For other variants in the WP family, see our broader WP series worm gearbox lineup including WPWA (horizontal flange input) and WPWDV (vertical-output) configurations.

Catalogue Specifications & Frame Capacity

The first table below lists the catalogue specification of the WPWO worm gear reducer family — gearing arrangement, torque and power range, materials of the principal wear components, and motor-flange options. The second table is the frame-by-frame capacity matrix: pick a frame, read the input power band the housing supports, and cross-reference the output-flange PCD that mates with your driven machine. PCD (pitch circle diameter) is the dimension to specify when ordering — the bolt pattern is what determines whether the gearbox bolts cleanly onto the existing flange, so it is worth measuring carefully before quotation.

Frame-size matrix below for the WPWO worm gear reducer: centre distance "a" (mm) defines mechanical capacity. Output-flange PCD is the dimension to verify against the driven machine before placing an order.

Why a Flange Output Matters — Mechanical Logic of the WPWO

A flange-output worm gear reducer eliminates one of the most failure-prone elements of a typical drive train: the coupling between gearbox output shaft and driven machine input shaft. Couplings — even good elastomeric ones — introduce backlash, demand careful angular and parallel alignment during commissioning, and are the first thing to fail under shock-load conditions. The WPWO sidesteps the issue by clamping its output flange directly to the driven machine. The result is shorter installed length, fewer alignment steps at commissioning, and a cleaner moment-load path through the driven machine's own bearings.

There is a structural cost to this elegance. Because the output bore now carries the radial moment of the driven machine — the load no longer sits on a separate bearing — the WPWO worm gear reducer output bearings must be sized larger than equivalent solid-shaft units. We use tapered roller bearings rather than deep-groove ball bearings on the output side for exactly this reason; the tapered roller pair handles both axial and radial moment loading without complaint. For a vertical mixer drive, this is critical: the mixer impeller weight, the radial fluid drag, and the axial down-thrust all enter the gearbox at the same flange face.

A common mistake new worm gear reducer specifiers make is treating WPWO and WPWDKS as interchangeable on the basis of frame size and ratio alone. They are not. The WPWO output flange is a structural member, not a connection convenience. Specify WPWO when the driven machine has its own bearings and you want the gearbox to bolt onto an existing flange face. Specify WPWDKS when you need a free-standing solid output shaft that drives through a coupling to a bearing-mounted load.

Heat Generation, Thermal Power & Sizing for Continuous Duty

Sizing a WPWO worm gear reducer for a continuous-duty mixer or pump drive requires considering thermal capacity alongside torque capacity. A WP-style worm gear reducer has two distinct power ratings the catalogue does not always emphasise. The first is mechanical rated power — the load the gear teeth, bearings and shafts can carry without breaking under SF=1.0 loading. The second is thermal rated power — the heat the housing can dissipate to ambient air without the oil bath exceeding its degradation temperature.

For a single-stage WPWO worm gear reducer at i=40, mesh efficiency sits around 70%. A 5.5 kW input therefore generates 5.5 × 0.30 = 1.65 kW of waste heat, all of which has to leave the housing through convection and radiation. At 25 °C ambient with a still-air installation, a WPWO135 cast-iron housing dissipates roughly 1.4 kW thermally. For the worm gear reducer that is below the 1.65 kW heat generation — meaning the unit cannot run continuously at its mechanical rating without auxiliary cooling. Either step up to WPWO147 (next frame, more housing surface), add forced-air ventilation, or accept that the unit can only run intermittently at 5.5 kW input.

This is the trap that catches first-time WP-series worm gear reducer specifiers and is why our application form asks for ambient temperature, duty cycle and hours-per-day before quoting. The mechanical rating column in the frame-size table assumes intermittent operation; for continuous duty above 12 hours per day, derate by a factor between 0.7 (45 °C ambient, sealed enclosure) and 0.9 (25 °C ambient, open ventilation). Specify the actual operating environment and we will return a thermally validated frame size, not just a mechanically-sufficient one.

Where the Flange-Output Geometry Earns Its Premium

The WPWO worm gear reducer is selected for applications where the load offers its own input flange and a coupling-free drive train is preferable. The five sectors below cover roughly 85% of WPWO orders shipped to Korean and regional industrial customers over the last twelve months.

Vertical Mixer & Agitator Drives

Top-mounted mixer drives in chemical, paint and food-processing tanks bolt directly to the WPWO output flange. The mixer column hangs from the flange via a stub shaft, and the bronze wheel inside the WPWO worm gear reducer absorbs the down-thrust from the impeller. The WPWO100 worm gear reducer at i=30 with a 1.5 kW motor is the workhorse for 200–400 L tank mixers; WPWO155 i=20 with 5.5 kW handles 1,000–2,000 L industrial agitators.

Vertical Pump Body Drives

Vertical-shaft sewage pumps, slurry pumps and viscous-fluid lobe pumps mount the WPWO directly onto the pump head. A WPWO80 or WPWO100 worm gear reducer at i=10 paired with a 0.75–2.2 kW motor delivers the 140–187 rpm range that most positive-displacement pumps need. The flange mount eliminates the stuffing-box realignment ritual that plagues coupled pump drives.

Screw Conveyor Drive Ends

Bag-house dust handling, cement clinker conveyance and sludge-removal screws all feed into a flange-mounted worm gear reducer end with a flanged drive boss that mates to the WPWO. WPWO135 to WPWO250 frames cover screw conveyors from 250 mm to 600 mm trough width. The self-locking i ≥ 30 ratios prevent reverse-drive of the screw column under power loss — important when the conveyor is full and a backflow could overload the discharge end.

Slewing Drives on Small Cranes & Manlifts

A WPWO worm gear reducer driving a slewing-ring pinion provides positive holding torque provides positive holding torque without an external brake on small jib cranes, telescopic manlifts and warehouse stacker cranes. The flange output drives a pinion shaft that engages the slewing-ring gear teeth directly — typical configuration is WPWO120 i=50 with a 1.5 kW brake motor.

Cooling Tower Fan & Damper Drives

For industrial cooling-tower variable-pitch damper actuators a worm gear reducer in WPWO80 or WPWO100 frame size and small cell-fan slow-speed drives use the WPWO80 or WPWO100 flange-mounted to the damper hub. Outdoor weatherproofing and the corrosion-resistant cast-iron housing handle the wet ambient that destroys aluminium-bodied alternatives within a year or two.

WPWO Flange-Mount Installation Best Practices

Installing a flange-output worm gear reducer differs from a coupled drive in a few small but critical ways. Following the four-step procedure below at commissioning prevents the most common warranty issues we see on returned units.

1. 1
   Verify flange face perpendicularity. Measure the perpendicularity of the driven machine's mating flange to the input shaft axis. Acceptable tolerance is 0.05 mm per 100 mm of PCD. If it exceeds that, the WPWO output bearing will see edge-loading from day one and bearing life will fall by 60–80%.
2. 2
   Tighten flange bolts in cross-pattern sequence. Use a torque wrench, two passes — first pass at 50% of final torque, second pass to full torque. The cross-pattern sequence avoids cocking the flange face. Final torque values are listed on the WPWO commissioning sheet shipped with each unit.
3. 3
   Confirm input-shaft fit before driving the bolt train home. If the driven machine's input shaft does not slide into the WPWO output bore with light thumb pressure, do not force it. Forcing causes the worm wheel to side-load the worm shaft on day one. Re-machine the input shaft slightly undersized rather than risk premature wheel wear.
4. 4
   Run the worm gear reducer unloaded for one hour, then check oil level. Run the WPWO worm gear reducer at no-load for 60 minutes after commissioning. Stop, wait 30 minutes for air to settle out of the bath, and verify oil level on the sight glass. Top up if necessary — first running often shows the oil level dropping by 3–5 mm as air pockets clear.

Quality Certification & Acceptance Testing

Every WPWO worm gear reducer leaving the worm gear reducer production line passes a four-stage acceptance test. The first is dimensional inspection — bearing seats, output flange runout, motor flange bolt pattern, all measured against ISO 9001-controlled drawings. The second is no-load run-in: 30 minutes at rated input speed in both rotational directions, monitoring temperature rise and listening for bearing noise. The third worm gear reducer test is the loaded test: 60 minutes at 75% of rated input power, monitoring oil temperature stabilisation. The fourth is a final visual and seal-leak check after 24 hours of cool-down.

The factory test record ships with every WPWO worm gear reducer unit, signed by the QC inspector and traceable to the worm shaft heat-treatment batch and bronze wheel casting heat. Korean customers requiring third-party witness inspection on critical orders — typically WPWO175 frames upwards used in chemical mixer drives — can specify a Bureau Veritas, SGS or TÜV witness at quotation stage; the cost is added per-unit and arranged through their Korean offices to keep audit logistics simple.

Standard certifications shipping with every unit include the ISO 9001:2015 manufacturing certificate, the CE conformity declaration for sale into the European Economic Area, and material certificates for the worm shaft (20CrMnTi heat-treatment batch) and bronze wheel (ZQSn10-3 casting heat). Korean Industrial Standard (KS) reference documentation is available on request for buyers needing it for KS-marked end-machine assembly.

Drive-Train Complements & Sister Reducer Lines

Drive trains around a WPWO worm gear reducer typically combine a worm gear reducer with three categories of supplementary product with three categories of supplementary product, plus one parallel reducer line from our Korean worm gear reducer manufacturer catalogue. The four below are listed in order of how often they appear together with WPWO units on the same purchase order.

Drive shafts (transmission companion). Although the WPWO output mounts directly to the driven machine, the input side often connects to its motor via a drive shaft when the motor is remote — typical of installations where the motor sits at floor level and the gearbox is high above on a mixer or pump skid. Telescopic and CV-jointed drive shafts handle the small angular and axial misalignments inevitable on welded skid frames. See PTO & CV joint drive shafts for matched-length assemblies.

Worm and worm wheel pairs (internal spare parts). The bronze worm wheel and steel worm shaft are the principal wear components inside any WPWO unit. After 25,000–35,000 hours of duty, the wheel typically reaches its wear limit while the cast-iron housing and tapered roller bearings remain serviceable. A worm-and-wheel rebuild kit lets a maintenance team restore the gearbox in place at roughly one-third the cost of a complete unit replacement. Sized for every WPWO frame at worm and worm wheel pairs.

Planetary gear reducers (sister product line). Where the application requires high mechanical efficiency (≥ 95%) or very low backlash for accurate positioning — for example servo-driven indexing rotaries or precision agitator-shaft positioning — a planetary reducer is the right alternative family. Same supplier, different drive principle. See planetary gear reducers for in-line and right-angle ranges that complement the WPWO worm gear reducer where worm efficiency is insufficient.

Agricultural gearboxes (industry-specific sister line). For tractor PTO drives, irrigation pump drives, feed-line conveyors and rotary tiller heads, our agricultural gearbox catalogue applies similar bronze-wheel-and-steel-worm technology in field-rated housings with reinforced sealing for outdoor exposure. Browse agricultural gearbox replacements for sizing.

WPWO Specification & Sizing FAQ

The questions below are the ones our applications team handles most often during quotation review and post-installation support for the WPWO worm gear reducer family. Answers reflect bench-test data and field experience rather than catalogue marketing language.

Field Reports from Industrial Plants

Feedback below is from process engineers, plant maintenance leads and OEM designers across Korea, Japan, Vietnam and Thailand who specified or serviced WPWO units over the past 12–18 months. Where customers have given written permission, technical detail and frame size are preserved verbatim alongside the worm gear reducer frame size.