Jack Up Cranes How They Work

TEL: 1-608-238-6001 Email: greg@electricship.com

Jack-up cranes are fascinating machines — they blend elements of cranes, offshore platforms, and giant screw jacks into one system

Quick Overview:

A jack-up crane is usually mounted on a jack-up barge or vessel, which is a floating platform equipped with large legs that can be lowered to the seafloor. Once positioned, the barge jacks up out of the water, lifting itself above the waves to form a stable, stationary platform — perfect for heavy lifting offshore (wind farms, oil rigs, etc.).

How it Works — Step by Step:

1. Floating to Site

• The jack-up vessel floats like a ship or barge to the desired location.

• The legs are raised during transit.

2. Deploying the Legs

• At the site, the legs are lowered vertically to the seabed.

• These legs are massive steel trusses or tubular structures — some can be over 100 meters long.

3. Jacking Up

• Giant hydraulic or electric-powered pinion drives (gear mechanisms) walk the platform up the legs.

• Some systems use rack-and-pinion, others use screw-jack type systems.

• The vessel rises out of the water — sometimes 10-30 meters above the surface — completely isolated from wave motion.

4. Crane Operations

• The crane (either lattice boom or telescopic) does its lifting work from this stable platform.

• Because the platform is jacked up on rigid legs, the crane isn't affected by wave motion — critical for precision offshore lifting.

5. Jacking Down and Moving

• Once lifting is complete, the platform is jacked back down.

• Legs are retracted.

• The vessel floats to its next location.

Why Use Jack-Up Cranes?

Advantage | Reason

Stability | No wave-induced motion during lifting.

Heavy Lifts | Can handle extreme loads (1000+ tons).

Offshore Versatility | Perfect for wind turbines, oil & gas structures, bridges, etc.

Key Components:

• Legs: Usually 3 or 4. Can penetrate soft seabeds or sit on hard rock.

• Jacking Mechanism: Hydraulic or electric — some use rack and pinion, others use screw threads.

• Crane: Often modular — can be lattice boom, telescopic, or custom.

• Hull/Barge: Floats the entire system to location.

Example Applications:

• Offshore Wind Farm Installation

• Decommissioning Oil Platforms

• Bridge Section Lifting (over water)

• Harbor and Coastal Mega-Projects

Cool Engineering Note:

Some modern jack-up vessels have moveable cranes that can slide or rotate along the platform to handle multiple lift points without repositioning the vessel.

Land-based tower cranes are engineering icons — super simple in principle but elegant in design

Tower Cranes = Vertical + Rotating + Lifting Machine

They're basically a tall mast bolted to a giant concrete block, with a rotating arm (jib) on top that lifts loads using counterweights for balance.

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Basic Parts of a Land Tower Crane:

1. Concrete Base

• Giant poured concrete block (tons of weight).

• Anchors the crane to the ground.

• Prevents tipping.

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2. Mast (Tower Section)

• The vertical steel structure.

• Built from modular lattice sections.

• Can climb higher as building rises.

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3. Slewing Unit (Rotation Bearing)

• Top of mast.

• Allows the entire jib and machinery deck to rotate 360°.

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4. Jib (Working Arm)

• Horizontal arm extending out.

• Load hook runs along this arm.

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5. Counter-jib

• Shorter arm on the opposite side.

• Holds counterweights (concrete or steel blocks).

• Balances the crane.

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6. Trolley & Hook

• Trolley runs along jib carrying the hook.

• Lifting cable winds/unwinds from the winch drum.

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7. Operator Cab

• Usually mounted near the slewing unit.

• Controls rotation, trolley, and hook winch.

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How it Works — Simple Flow:

```plaintext

1. Concrete base → Provides stability.

2. Mast → Vertical support, height.

3. Slewing unit → Allows rotation of entire upper structure.

4. Jib → Extends to reach loads.

5. Counter-jib → Balances loads with counterweights.

6. Winch + Trolley → Moves hook in/out along the jib.

7. Operator lifts → Using radio control or from the cab.

```

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Cool Feature — Climbing the Building

Some tower cranes can self-climb:

• A hydraulic climbing frame (climber) fits between mast sections.

• It pushes the upper part up.

• A new mast section is inserted below.

• Repeat = Taller Crane!

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Example Applications:

| Use | Example |

|-----|---------|

| Skyscrapers | Concrete & steel beam placement |

| Bridges | Heavy component placement |

| Powerplants | Heavy equipment positioning |

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Diagram Available?

Want me to generate a clean labeled diagram for you like the jack-up one? It’ll show the:

• Mast

• Jib

• Counter-jib

• Slewing unit

• Hook & trolley

• Counterweights

Self-climbing (jack-up) system

The crane lifts itself up using a hydraulic jack system, allowing workers to insert new mast sections beneath the slewing unit (rotating part). This is called top climbing.

Step-by-step: How Tower Crane Jack-Up Climbing Works

1. Climbing Frame Installed

A climbing collar or climbing frame is installed around the mast, just below the slewing unit (where the operator sits).

> Think of it like a hydraulic-powered elevator for the upper crane structure.

2. Hydraulic Jacks Lift the Crane

• The climbing frame has hydraulic jacks or rams.

• These push the slewing unit (with jib and counter-jib attached) upwards about 3-6 meters — creating a gap between the top of the mast and the slewing unit.

3. Insert New Mast Section

• Workers slide in a new mast section horizontally into the gap.

• It’s bolted to the existing mast structure.

4. Lower the Crane Down

• The hydraulic system lowers the slewing unit down to sit on the new mast section.

5. Repeat

• This process is repeated for each new section.

• Cranes can climb inside the building (internal climbing) or be mounted externally.

Visual Flow:

| Step | Action | Result |

|------|--------|--------|

| 1 | Hydraulic rams push slewing unit up | Creates gap |

| 2 | New mast section inserted | Extends height |

| 3 | Crane lowered onto new section | Secured |

| 4 | Repeat | Crane gets taller |

Key Benefits:

• No need for giant mobile cranes for lifting mast sections high up.

• Crane grows with the building.

• Efficient use of time and resources.

Types of Climbing Systems:

| Type | Description |

|------|-------------|

| Internal Climbing | Crane climbs inside a building’s core or elevator shaft. |

| External Climbing | Crane climbs up its own external mast sections. |

1. Initial Setup:

The crane is installed on the foundation and connected to the building's structure.

2. Climbing Frame:

A "climbing frame" or "jack-up frame" is attached to the crane's mast. This frame houses the hydraulic cylinders that will lift the crane.

3. Jacking Mechanism:

Hydraulic cylinders within the climbing frame are pressurized, using hydraulic pumps, to lift the crane. This lifts the top section of the tower, creating a space for a new section to be inserted.

4. Adding Sections:

The crane operator uses the crane to lift a new section of the tower and insert it into the newly created space.

5. Ratchet System:

A ratcheting system ensures that the crane cannot fall back down as it's being raised.

6. Repeated Process:

The jacking and adding of sections is repeated, raising the crane higher with each cycle. The climbing frame is then moved to the newly installed section, and the process repeats.

7. Safety and Stability:

Counterweights are used to balance the crane and prevent tipping. The entire process follows strict safety procedures to ensure a safe and efficient increase in height.

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