Rotary Table in Drilling Rig – Components, Working, Maintenance & Safety

Before the age of automated top drives, drilling rigs relied on a mechanical marvel — the Rotary Table in Drilling Rig.
This heavy-duty turntable, located on the rig floor, is responsible for transmitting rotational power to the drill string, allowing the bit to cut through subsurface rock.

It works hand-in-hand with the Kelly, Master Bushing, and Swivel, forming the core of the Rotating System that makes drilling possible.

Even today, thousands of onshore rigs across Asia, the Middle East, and Africa still use rotary tables due to their simplicity, low maintenance cost, and reliability.

📌 If the Hoisting System lifts the weight, the Rotary Table makes the hole.

Construction and Components of Rotary Table

The Rotary Table in Drilling Rig is built to handle immense torque and axial loads. It sits flush with the rig floor and forms a stable base for the rotating system.

Key Components

Component	Function
Rotary Table Base	Main structural housing, supports all internal gears and bearings.
Ring Gear & Pinions	Transfers power from drawworks or motor to rotate the table.
Main Bearing	Takes vertical loads from the drill string.
Hold-Down Bearing	Prevents upward lift when heavy torque is applied.
Mud Seal (Labyrinth Seal)	Prevents drilling mud and debris from entering bearing housings.
Master Bushing	Sits inside the table, supports kelly bushing and rotary slips.
Kelly Bushing	Connects to the kelly to transmit torque to the drill pipe.
Rotary Lock	Locks the table during connection or tripping operations.

In chain-driven models, power is supplied from the drawworks or separate rotary drive motor through roller chains and sprockets.
Modern versions use electric or hydraulic drives, reducing mechanical loss and improving RPM control.

Working Principle – How the Rotary Table Rotates the Drill String

1. Power Input: The table receives torque from the rig’s power system through chains, gears, or a direct motor connection.
2. Rotation Transmission: The ring gear turns the master bushing and kelly bushing, which grip the kelly (square or hexagonal pipe).
3. Torque to Drill String: As the kelly rotates, torque passes through the drill pipe down to the drill bit, cutting the rock.
4. Support & Slips: When adding or removing pipe sections, the table supports the drill string through rotary slips set in the master bushing bowl.
5. Locking Mechanism: The rotary lock secures the table when rotation must stop — preventing pipe rotation during makeup or breakout operations.

Typical rotation speed: 40–200 RPM, depending on formation hardness and bit design.
Torque capacity: 20,000 to 60,000 ft-lb, with load ratings up to 600 tons, per API 7K specifications.

Master Bushing and Kelly Bushing – The Driving Interface

These two parts are crucial links between the rotary table and the drill string.

Master Bushing

• Fits into the rotary table and supports rotary slips or the kelly bushing.
• Tapered internal bowl allows slips to grip the drill pipe securely.
• Common types: solid, split, and hinged.
• Load ratings: 100 to 600 tons (API 7K).

Kelly Bushing

• Locks into the master bushing with drive pins or square slots.
• Transmits torque from the rotating table to the kelly.
• Two drive types:
  • Square Drive (older rigs) – simpler, used on shallow wells.
  • Pin Drive (modern) – provides smoother torque transfer.

💡 Analogy: Think of the master bushing as the gearbox casing and the kelly bushing as the output shaft transmitting power.

Rotary Slips – Holding the Drill String Securely

Rotary slips are wedge-shaped steel segments that fit into the master bushing bowl to grip the drill pipe when the string is suspended.

• Each slip has dies or inserts that bite into the pipe surface.
• The tapered outer surface matches the bowl’s taper to evenly distribute the load.
• Slips must be inspected for wear and replaced regularly to prevent pipe damage.

Common Slip-Related Hazards

• Deformation of slip bodies from uneven load.
• Pipe crushing due to improper die seating.
• Dropped string if slips are set in a dirty or damaged bowl.

Safety Tip: Never stop the drill string with slips — always slow the rotation first and ensure mud pressure is balanced.

Lubrication System of Rotary Table

Proper lubrication ensures long bearing life and smooth torque transmission.

Key Lubrication Points

1. Main Bearing Housing – filled with oil bath or grease reservoir.
2. Ring Gear Teeth – coated with heavy-duty open gear lubricant.
3. Hold-Down Bearing – greased through central fitting weekly.
4. Mud Seal & Labyrinth Seal – checked for contamination and cleaned daily.

Recommended Maintenance Schedule

Frequency	Maintenance Task
Daily	Check oil level, clean mud seal, inspect chain tension.
Weekly	Grease main & hold-down bearings, inspect drive pins and gears.
Monthly	Change bearing oil, check alignment, test rotary lock.
Quarterly	Perform slip-test procedure, inspect bushing wear and replace if needed.

Maintenance, Inspection & Troubleshooting

Common Issues and Fixes

Problem	Likely Cause	Solution
Oil leakage from housing	Worn mud seal or loose bolts	Replace seal, torque bolts to spec
Overheating bearing	Insufficient lubrication	Refill oil bath, inspect circulation
Unusual vibration	Worn pinion or misaligned gear	Realign gears, replace worn teeth
Noisy operation	Chain too tight or dry	Adjust chain tension, apply grease
Difficulty in locking table	Damaged rotary lock pin	Replace locking mechanism

Slip-Test Procedure (API Recommended)

• Clean slip bowl and dies.
• Apply measured hook load incrementally.
• Wrap pipe with test paper to check die marks.
• Record load at which slip begins to slide.
• Compare against rated load; replace if below 80%.

Rotary Table Safety Precautions

• Always lock the rotary table before connecting or breaking out pipes.
• Never stand on the table while it’s rotating.
• Use safety clamps when handling drill collars or heavy tubulars.
• Keep mud and debris clear of master bushing bowl.
• Inspect chains, pins, and bearings during every shift change.
• During maintenance, use lock-out tags on the power line.

A well-lubricated, properly maintained rotary table is not just efficient — it’s safe for everyone on the drill floor.

From Rotary Table to Top Drive – The Modern Transition

While the rotary table system remains reliable for vertical and shallow wells, most modern rigs have shifted toward Top Drive Systems.

Key Differences:

Feature	Rotary Table	Top Drive
Torque Transmission	Indirect (via kelly drive)	Direct motor drive
Connection Speed	2–3 minutes	1 minute
Safety	Manual pipe handling	Automated control
Directional Drilling	Limited	Excellent
Cost	Low	High (but efficient)

Yet, in rugged onshore regions like Rajasthan, Oman, and Egypt, rotary tables still dominate because they’re mechanically simpler, easier to repair, and less power-dependent.

Rotating System in Drilling Rig – Rotary Table, Kelly, Top Drive & Swivel Explained

API Rotary Table Sizes and Load Capacities (Reference)

API Size	Opening (in)	Load Rating (tons)	Typical Use
17½	17.5	100–150	Shallow wells, water wells
20½	20.5	200–250	Light oil rigs
27½	27.5	300–350	Medium drilling rigs
37½	37.5	500	Heavy land rigs
49½	49.5	600+	Offshore or ultra-deep rigs

Source: API Spec 7K

FAQ – Quick Answers

The Rotary Table remains one of the most iconic and dependable pieces of equipment in drilling history.
While automation and top drives have changed the game, the rotary table continues to power rigs where simplicity, durability, and field serviceability matter most.

From the master bushing to the labyrinth seal, every part plays a vital role in keeping the rotation steady and the drilling safe.