API 7K Drilling Rig Drawworks For Hoisting Operations

The drawworks is the primary hoisting mechanism on a drilling rig. Essentially, it is one large winch that spools off or takes in the drilling line — a heavy-duty wire rope — to raise or lower the drill stem, drill bit, casing strings, and completion equipment through the crown block and traveling block system. The drawworks converts prime mover torque into the vertical lifting force that controls weight on bit and manages the entire drill string during every tripping operation. It is the central power transmission unit of every rotary drilling rig worldwide.

The drilling line is spooled over the crown block and traveling block (which moves up and down), creating a block and tackle system that multiplies the prime mover force into hook load capacity. A 3,000 hp drawworks on a 12 line reeving configuration can generate over 1,350 tonnes of hook load.

All our drawworks are designed and manufactured in compliance with API Spec 7K (Specification for Drilling and Well Servicing Equipment), which governs design, manufacture, testing, rated capacity, drum dimensions, gear ratios, brake torque requirements, and documentation standards for new drilling and well servicing equipment.

Key Features – Precision Engineering for Demanding Drilling

How Drawworks Work – From Prime Mover to Hook Load

The drawworks drum is a large-diameter steel cylinder — typically 800 mm to 1,400 mm (31.5 to 55 in) — around which multiple layers of drilling line wire rope are spooled. The wire rope runs from the drum up through the crown block sheaves at the derick top, down through the traveling block, and its free end is anchored to a deadline anchor on the rig substructure.

The prime mover — originally direct diesel engines through mechanical transmissions, but now frequently AC electric motors driven by diesel-generator sets — drives the drum through a transmission providing multiple speed ranges. High gear gives fast line speed for tripping operations (typically 150–300 m/min or 490–980 ft/min at low hook load). Low gear provides high torque for lifting heavy casing strings at slow speeds.

AC VFD (variable frequency drive) systems eliminate mechanical gear changes entirely, providing continuously variable speed and torque across the operating range. This gives the driller precise control over weight on bit, adjustable in increments as fine as 0.5 tonne (1,100 lb) — critical for optimising rate of penetration (ROP) in heterogeneous formations.

Serial Rig Drawworks – Technical Specifications

Our SDW series drawworks offers five power ratings to suit rigs from 350 HP up to 1,000 HP, with applications ranging from workover operations to medium-depth drilling.

Note: All SDW series drawworks are manufactured in compliance with API Spec 7K. The sand drum (auxiliary winch) can be fitted optionally on all models.

Brake Systems – Understanding Main and Auxiliary Brakes

The braking system is arguably the most safety-critical component on any drawworks. Brake failure with a fully loaded drill string can result in a freefall event, potentially driving the bit through the bottom of the hole and causing catastrophic wellbore damage or a well-control incident.

Main Brake – Band Brake or Hydraulic Disc Brake

Band Brake: A traditional mechanical brake consisting of a steel band lined with friction material that wraps around a brake rim (drum). Simple, robust, and field-repairable. Suitable for lower-speed, lower-duty applications. Heat build-up can be a limitation during extended lowering operations.

Hydraulic Disc Brake: Modern disc brakes use calipers squeezing brake discs mounted on the drum shaft. They offer consistent braking torque, better heat dissipation, and smoother control than band brakes. The brake disc is water or air-cooled. Hydraulic disc brakes are increasingly the preferred option for deeper wells and higher load applications.

Auxiliary Brake – Hydromatic or Water-Cooled Disc Brake

The auxiliary (or "secondary") brake is used to control lowering speed over extended periods, allowing the main brake to be reserved for stopping and holding. Two primary types are available:

Hydromatic Brake: A hydrodynamic brake that uses fluid shearing to absorb energy and control lowering speed. Provides smooth, continuous braking without mechanical friction wear. Available in 122 and 22" SR models.

Water-Cooled Disc Auxiliary Brake (WCB series): An air-controlled, water-cooled disc brake system. Suitable for high-duty cycles where large amounts of energy must be dissipated during deep tripping operations.

Single Drum vs. Double Drum Configuration

The auxiliary (sand) drum on the SDW series has a diameter of Φ324 mm (12¾"), with lengths varying from 1,016 mm to 1,254 mm depending on model. It uses a band brake system and ATD124H push-disc clutch.

How to Select the Right Drawworks for Your Rig

Choosing the correct drawworks requires balancing horsepower, fastline pull, drilling depth, and intended application. Use this selection guide:

Additional selection considerations:

Drilling line diameter — Thicker wirelines (Φ32 mm / 1¼") handle higher loads but require larger drum capacity.

Brake type — Disc brakes recommended for deeper wells and longer lowering cycles; band brakes suitable for shallower, less demanding operations.

Auxiliary brake requirement — Deeper wells with long tripping runs require a reliable auxiliary brake (WCB series recommended for high-duty cycles).

 Drum configuration — Single drum sufficient for most operations; double drum recommended if the rig also performs significant light-hoisting tasks.

Why Partner with Sunrise for Drawworks

As a specialized trading company with strong API-certified manufacturing partnerships, Sunrise offers:

API Spec 7K certified drawworks — Full compliance with API Q1, 7K, and relevant API specifications.

Complete model range — From SDW350 (350 HP) to SDW1000 (1,000 HP) and beyond.

Flexible options — Single or double drum; band or disc main brake; hydromatic or WCB auxiliary brake.

Custom manufacturing — Can design and manufacture to meet specific project requirements.

Global logistics support — Export documentation, sea/air freight, and delivery to remote drilling sites worldwide.

Contact us to order the right drawworks for your drilling or workover rig. We provide the correct power rating, drum configuration, and brake system for your specific well depth and operational requirements — with full API compliance and on-time delivery.