Photos courtesy of National Pile Croppers
Hydraulic pile croppers are becoming the must-have equipment on sites and projects throughout the world. National Pile Croppers (NPC) managing director Simon Price explains what exactly a hydraulic pile cropper is and how to get the best from it.
Precast concrete piles are used for various civil engineering and construction structures with common applications ranging from small housing developments to major inner-city renovation, construction and infrastructure projects. These piles can come in custom lengths and are suitable for a huge range of applications and ground conditions, thereby offering a cost-effective precision piling solution once reduced.
Previously, concrete piles were reduced using methods such as hydraulic or diesel hammers, among other methods. Previous methods also gave rise to health problems such as hand-arm vibration syndrome (HAV) and risks associated with manual work within unstable/subterranean ground conditions. As a result, hydraulic pile breakers were developed to make the task of reducing these piles safer and more efficient.
The first major steps in producing the pile cropper as it’s known today began in the ’90s, with the development and refinement of the technology being undertaken by members of the current NPC team. New equipment has been developed for the various types of piles and applications that are found within the global construction industry. The work undertaken by the NPC team led to a set of pile cropping standards being incorporated into the U.K.’s health and safety executive Guide of Current Practice. The new generation of pile croppers have also been widely advocated by health and safety professionals and engineers alike. As a result, hydraulic pile croppers have become essential in making the task of reducing piles much safer and more efficient.
Defining what a pile cropper is
A pile cropper (also known as a pile cutter or pile breaker) is a precise hydraulic shear with defined angles of deflection and points of contact, ensuring a clean cut of the excess pile that does not interfere with the efficacy of the remaining pile. There are a breadth of different types and sizes available, depending on the task at hand. For example, augured, bearing, contiguous, secant, CFA, trench and helical displacement with croppers are available from NPC and other companies in varying sizes, ranging normally from 300 mm to 1,200 mm in diameter.
Mounted on a 360° excavator via quick release fittings, pile croppers have proved their versatility and effectiveness in all sectors of the construction industry. When lowered onto the concrete pile, the hydraulic system operates the jaws, which allow the pile cropper to cut a de-bonded pile, causing the concrete to break away, leaving a horizontal finish. In doing this, the chisels penetrate in a precise direction up to the rebar to make the fracture. On bonded piles, the chisels will penetrate further, and due to the shape of the chisels and the reaction forces of the rebar, the concrete will break in pieces and can easily be lifted off the pile enabling recycling of the cut away concrete.
Using a hydraulic pile cropper
The connection between the excavator and the pile cropper is made via quick-release fittings on excavators with pressures ranging from 150 bar to 275 bar. The excavator lifts the pile cropper over the pile and addresses the pile cut-off level where a complete horizontal fracture is made. The chisels penetrate in a horizontal direction up to the rebar to make the fracture. On bonded piles, the chisels will then penetrate further, and due to the shape of the chisels and the reaction forces of the rebar, the concrete will break in pieces and can easily be lifted off the pile.
When using a pile cropper, it is advised that the piles should be cast higher than the desired finish level. This is to ensure that any impurities or damage at the top of the pile is removed as part of the cropping process. In addition, it’s important to consider whether a protrusion of the rebar (a reinforced steel bar that is contained within the concrete to offer extra stability) is required for the final height to allow construction to take place.
To avoid damage to piles during cutting, it’s important to ensure that the right type of cropping equipment is chosen. This is essential for a successful pile-cutting project, especially when specific time frames need to be considered (NPC, for example, has a trained and experienced in-house help desk that advises users on how to get the best results). A common problem often experienced during pile cutting is when fracturing or spalling occurs beneath the surface of the concrete. This is very frustrating, time-consuming and expensive for construction teams. Therefore, damage to piles should be avoided at all costs, which is something that using the correct pile cropper for the job can help to avoid.
Advantages of using a hydraulic pile cropper include:
- Considerably faster than conventional methods able to crop up to 100 piles per day
- Very compact dimensions
- Low cut-off level
- Easy to operate
- No noise, no vibrations
- No cracks below cut level when used with reinforced debonding methods
- The reinforcement remains fully intact
- Leaves a perfect horizontal concrete fracture at pile cut-off level
- Easy adjustment
- Complies with health and safety guidelines for HAV injuries
Bridging the gap
Over the past eight years, NPC has created a complete range of in-house designed, manufactured and maintained pile cropping equipment which has revolutionized the pile cropping industry. NPC is a fully vertically integrated pile cropper company taking its products from 3D CAD models through manufacture and into operation in the field.
NPC has developed and supplied its own line of patented customer-focused pile cropping solutions to a wide span of customers. These range from multinationals and specialist piling companies, regional contractors and local ground workers.
For more information, go to www.nationalpilecroppers.com.