Temporary works Crane Pad Design Guide
Table of Contents
What is a Crane Pad?
A crane pad, also known as an outrigger pad, is a safety tool used under the outriggers, shoes, floats, or feet of heavy equipment such as cranes to distribute the load over a larger area and enhance stability. These pads are essential for preventing the ground underneath the equipment from shifting, displacing, or collapsing, which could lead to the equipment toppling over.
Crane pads are available in various materials, including wood, steel, aluminum, plastics, and composites, each offering different benefits in terms of strength, durability, and environmental impact.
Crane pads are designed to be durable and have excellent load-bearing capabilities to support the weight and operations of heavy machinery. They are particularly useful in environments with soft or unstable ground but are versatile enough for use on various types of landscapes. The use of crane pads is critical not only for the safety of the equipment and operators but also for protecting the ground surface from excessive pressure and damage.
Crane Pad Design and types
Crane pads come in various types, each designed to support different weights, machinery, and environmental conditions. Here are the different types of crane pads available:
1.Fiber Reinforced Polymer (FRP) Crane Pads:
– FiberMax® Crane Pads are made from FRP and are designed to support and stabilize mobile cranes up to 500 tons. They offer similar strength and stiffness characteristics as steel crane mats but are up to 60% lighter, which can reduce transportation costs and speed up setup and teardown times. These pads are resistant to fluids, chemicals, UV, and do not rust, rot, or degrade in extreme environments.
- Various Types of Timber Crane Mats:
– Standard Crane Mats: Often made from hardwood timbers like oak or fir, used for a wide range of projects.
– Transition Mats: Designed to create a smooth, level surface on uneven terrain.
– Swamp Mats: Engineered for use in wet or soft ground conditions.
– Rig Mats: Specialized for use in the oil and gas industry and other heavy-duty applications.
– Outrigger Pads: While not technically mats, these are used to support the outriggers of cranes and heavy equipment.
- High-Density Polyethylene (HDPE) Crane Mats:
– These crane mats and Multi-Mat systems are made from HDPE, which is resistant to water, oil, and chemicals. They are lighter than steel pads and have a greater load-bearing capability of up to 200 tonnes. The interlocking Multi Mat system provides a flexible solution for cranes, allowing various configurations depending on space and load capacity requirements.
- Aluminium, Composite, Plastic, and Timber Systems:
– ALIMATS® is a patented handleable interlocking outrigger mat system made from recycled certified extruded aluminium modules. Other handleable systems are manufactured in HDPE or timber.
- Geogrid Reinforced Crane Pads:
– Tensar manufactures geogrid systems that reinforce crane pads, increasing safety against bearing failure and reducing vertical settlement.
- Plywood Outrigger Pads:
– These are made from certified exterior plywood with exterior polyurethane glue and are designed to increase stability and reduce “point load” on hydraulic cranes with extended support outriggers.
- Recycled High-Density Polyethylene Pads:
– Outrigger pads made from 100% recycled HDPE, which are hard-wearing, do not splinter, and maintain their supporting capabilities under normal use.
- Steel Crane Mats:
– Steel crane mats are usually the most resilient in tough environments and are available in various types.
Each type of crane pad is designed with specific features to meet the demands of different construction sites and heavy machinery. The choice of crane pad depends on factors such as the type of machinery used, the weight it needs to support, the terrain of the construction site, and the environmental conditions.
Crane Pad Design Procedure and Sizing
To determine the appropriate size of a crane pad for a specific crane operation, you need to follow a systematic process that involves several key steps. These steps ensure that the crane pad selected can adequately support the load and distribute it safely over the ground. Here’s a detailed breakdown of the process:
- Calculate the Force Exerted on the Ground:
– First, calculate the total force exerted by the crane on the ground. This includes the weight of the crane itself, any attachments, and the load being lifted. The force is typically given in pounds or kilograms.
- Determine Ground Bearing Pressure:
– Obtain the allowable ground bearing pressure for the soil or surface on which the crane will operate. This is the maximum pressure the ground can handle without yielding. It can be determined through soil testing or consulting a geotechnical engineer.
- Calculate the Required Pad Area:
– Divide the total force by the allowable ground bearing pressure to determine the required area of the crane pad in square feet or square meters. This calculation ensures that the pad size is sufficient to distribute the load within the limits of the ground bearing capacity.
- Determine Pad Dimensions:
– Once the total required area is known, you can calculate the dimensions of the pad. If assuming a square pad, take the square root of the area to find the length of each side of the square pad. Always round up to ensure safety.
- Select Pad Material and Thickness:
– Choose a material that can withstand the load and environmental conditions. Common materials include high-density polyethylene (HDPE), steel, or reinforced composite materials. The thickness of the pad should also be sufficient to prevent bending or breaking under load. Manufacturers often provide recommendations based on the pad’s material and size.
6.Consult Manufacturer’s Guidelines and Safety Standards:
– Always refer to the crane manufacturer’s guidelines for specific recommendations on outrigger pad usage. Additionally, adhere to local safety standards and regulations to ensure compliance and safety during crane operations.
By following these steps, you can accurately determine the appropriate size and material for crane pads, ensuring safe and efficient lifting operations.
Safety Considerations when using crane pads
When using crane pads, also known as outrigger pads, there are several safety considerations to keep in mind to ensure the stability of the crane and the safety of the operation.
Ground Conditions:
– Ensure that ground conditions are firm, drained, and graded to a sufficient extent to support the crane and outrigger pads.
– Conduct a thorough site assessment to identify potential hazards and evaluate ground stability, including soil type, compaction, slope, and underground utilities.
Proper Sizing and Material Selection:
– Select outrigger pads of appropriate size, material, and strength to distribute the crane’s load and reduce ground-bearing pressure to acceptable levels.
– Materials should be chosen based on the specific needs of the operation, considering factors like weight, resistance to chemicals, and environmental conditions.
Load Capacities:
– Be aware of the crane’s load capacity and ensure that outrigger pads can handle the maximum load without exceeding their capacity.
– Factor in additional weight components such as counterweights when calculating the pressure on outrigger pads.
Proper Setup and Levelling:
– Use outrigger pads specifically designed for the crane model and ensure they are in good working condition.
– Outrigger pads should be large enough to distribute the load evenly and prevent excessive ground pressure.
– Always keep the outrigger shoe in the centre of the pad and ensure complete contact with the ground.
Regular Inspections and Maintenance:
– Regularly inspect outrigger pads for signs of damage, corrosion, or wear and perform maintenance as per the manufacturer’s guidelines.
– Conduct load testing when required to ensure the pads can support the intended loads.
Operator Training and Communication:
– Ensure that crane operators are adequately trained in outrigger and crane pad setup, understanding load capacities, setup procedures, and safety protocols.
– Establish effective communication between the crane operator, signal person, and other personnel involved in the operation.
Cribbing and Blocking:
– Use cribbing blocks to support the outriggers on slopes or uneven ground, enhancing stability.
– Cribbing should not be split, warped, or excessively worn, and should be laid at a bias when constructing cribbing pads.
Environmental and Aesthetic Considerations:
– Use outrigger pads to prevent damage to delicate terrains like asphalt, grass, or landscaped areas, thus avoiding unsightly damage and potential repair costs.
Safety Protocols:
– Follow all local safety standards and guidelines, including OSHA regulations and manufacturer’s specifications for safe operations.
– Ensure that the setup complies with the crane manufacturer’s specifications and that the load charts are specific to the crane.
Emergency Preparedness:
– Have an emergency and rescue plan in place to ensure that operators can be rescued safely in the event of an incident.
By adhering to these safety considerations, crane operations can be conducted more safely and efficiently, reducing the risk of accidents and ensuring the stability of the crane during lifting operations.
How to repair parapet wall
Repairing parapet walls involves several steps and techniques to address common issues such as moisture ingress, structural instability, and aesthetic deterioration. Here’s a comprehensive guide on how to repair parapet walls:
Initial Assessment
– Identify Problems: Conduct a thorough inspection to identify issues such as cracks, crumbling mortar, water seepage, or structural weaknesses.
Structural Repairs
– Reinforcement: If structural instability is a concern, consider adding more wall ties to increase lateral stability, or tie the parapet back to adjacent structures if possible.
– Masonry Repair: Replace damaged bricks or stones, and repoint the mortar joints where necessary. Use materials that match the existing masonry to maintain aesthetic consistency.
Moisture Control
-Coping Replacement: Remove and replace damaged coping stones or caps. Ensure that new copings are properly installed with an overhang to direct water away from the wall.
– Waterproofing Membranes: Apply waterproofing membranes or sealants to prevent water ingress. This is particularly important at the top of the parapet where the coping sits.
– Flashing and DPC Installation: Install or replace flashings and damp proof courses (DPC) to prevent water from penetrating the masonry.
Aesthetic Improvements
– Cleaning: Clean the parapet walls to remove dirt, stains, and biological growth. This can involve gentle washing or chemical treatments depending on the severity of the soiling.
– Rendering or Painting: Apply new render or paint if the original surface is extensively damaged or to improve the wall’s appearance.
Preventative Measures
– Regular Inspections: Schedule regular inspections to catch and address new issues before they become severe.
– Proper Drainage: Ensure that gutters and drainage systems are clear of debris to prevent water from pooling on or near the parapet.
Advanced Techniques
-Tuckpointing and Grinding: Use tuckpointing to restore mortar joints and grinding to smooth out uneven surfaces.
– Use of Modern Materials: Consider using modern, durable materials for repairs to enhance longevity and performance.
What are the common reasons for crane pads/outigger failures?
The most common reasons for outrigger failure include:
Ground Conditions:
– Inadequate assessment of ground conditions can lead to outrigger failure. Ground that is not firm, drained, or properly graded can cause outriggers to sink or shift, leading to instability and potential collapse of the crane.
Improper Sizing and Use of Pads:
– Using outrigger pads that are too small or not designed for the load can result in excessive pressure on the pad, leading to shear failure or physical breaking of the pad.
Material Failure:
– Outrigger pads can fail due to material defects such as cracking, warping, rotting, or permanent deformation. Materials not engineered for the specific application, like wood, can degrade over time due to moisture, UV light, insects, and stress from previous use.
Excessive Load:
– Overloading the crane beyond its capacity can cause outriggers to fail due to the excessive force exerted on them. This can lead to shear failure, where the material bends or deforms past its yield point.
Improper Setup and Levelling:
– Failing to set up outriggers within the level tolerances required by the manufacturer can reduce the equipment’s lifting capacity and lead to instability or tipping.
Lack of Inspection and Maintenance:
– Outriggers can fail if they are not regularly inspected and maintained. Issues such as hydraulic failures, worn-out components, or mechanical defects can go unnoticed and lead to failure.
Inadequate Cribbing and Blocking:
– Insufficient cribbing or blocking under outrigger floats, especially on soft ground, can cause the outriggers to punch through the ground, leading to accidents.
Failure to Follow Manufacturer’s Guidelines:
– Not adhering to the manufacturer’s guidelines for the use and inspection of outrigger pads can result in improper use and potential failure.
Environmental Factors:
– Environmental conditions such as wet, unstable, or uneven surfaces can compromise the stability of outriggers and lead to accidents.
Human Error:
– Operator error, such as failing to properly secure outriggers, not using outrigger pads, or not following established procedures, can contribute to outrigger failure.
Mechanical Failure:
– Mechanical issues, such as hydraulic failures or structural defects, can lead to the unexpected retraction or extension of outriggers, causing instability.
Communication Failures:
– Miscommunication or lack of clarity regarding the setup and operation of the crane can lead to improper use of outriggers and subsequent failure.
These factors highlight the importance of proper assessment, setup, and maintenance of outriggers and their pads, as well as adherence to safety guidelines and manufacturer’s instructions to prevent outrigger failure.