Acrow Props are an extremely versatile product which can be found on many construction sites. They are commonly used on building sites to provide a quick and simple method of providing temporary support for formwork for reinforced concrete floors and beams. Acrow props are equally useful as raking shores to support formwork for columns, walls and staircases. They are invaluable in repair work, demolition or for replacing a permanent support, for supporting canopies, lintels and the like while brick work or concrete is setting.
Acrow props consist of two circular steel tubes, an inner tube with a top plate that slides up and down freely inside an outer tube which is attached to the base plate. The inner tube has holes down its length so that you can quickly extend the inner tube to just below the desired height and insert a steel pin to lock in that length. To extend the prop to the correct height the top of the outer tube is threaded and a collar, which is similar to a nut on a bolt, picks up and supports the steel pin. So by rotating the collar and moving it up it extends the inner prop. This allows you to achieve the exact height required.
The ‘Acrow Prop Safe Installation Guide’ gives you a checklist of what to check before you even start and then shows you what you need to check to ensure the safe installation of your acrow props. Once installed there is a list of items that need to be checked regularly to ensure the continued safe performance of your acrow prop installation and then finishes off with a checklist for their safe removal.
Pre-installation Checklist
- Start by planning the job. Make sure you have the right number and sizes of props. Inspect the site and if necessary mark out the prop locations.
- Have you correctly selected the right sized props for the job? Do you have enough to support the weight? Never exceed the safe working load (SWL) for your specific size props. Refer to the manufacturers load charts. If unsure, consult your Engineer or other responsible person, who will consider the weight of the overhead structure that is to be supported and work out the correct size and quantity.
- It is the responsibility of the user to check the props each time before they start work. When inspecting the props, items to check include:-
- Check that the inner and outer tubes are straight and that they slide easily.
- Check to ensure that the collar rotates freely around the thread and that the tread is not damaged or blocked.
- Check to ensure that there is no damage to the pin. If the pin is secured by a chain, make sure that it is still attached. If it is fitted with a wrap around pin then it does not need to be secured by a chain. Only use the original pin, do not use any other pin.
- Do Not try and repair any faulty prop. If a prop is faulty it should be immediately tagged and isolated and is not to be used.
Installation Checklist
- Warning props which are designed to be used in compression CANNOT be used to in tension.
- Always wear the appropriate safety equipment when using this equipment.
- Ensure that the work area is cordoned off to prevent public access, only essential people should work in the area.
- Ensure that the props are installed by qualified people who have the necessary knowledge and experience to do the job safely.
- It is important that the prop is installed vertical to ensure that it can support its specified load. Props must never be used more than 1.5 degrees off vertical as this can substantially decrease its capacity. This is about 50 mm (2 inches) out of true vertical for every 1.8m (6 feet) of length.
- Make sure that the base plate and top plate of your prop is bearing directly on the surface. Ensure also that the floor surface and roof surface are sturdy enough to support the weight that will be placed upon it.
- When props are bearing on a flexible surface, such as a gravel surface, each prop should stand on a timber soleplate or equivalent. A timber soleplate should be at least 225mm (9 inches) wide by 38mm (1.5 inches) thick. It should be long enough to project at least 300mm (1 foot) either side of the prop’s base plate. A soleplate can also be used above the head plate to help spread the load if required. If you are unsure or have any doubts please refer to your engineer or other competent person.
- Acrow props come in 5 different sizes so Do not use props that are too short by making up the gap with timber. Always use the correct length Acrow prop.
Post Installation Checklist
- Props left to support a curing slab can loosen up with time. As the slab cures it naturally contracts which can cause the prop to loosen up so it is recommended that they be inspected by a competent person and retightened regularly.
- As a minimum, all props must be inspected at least once a week.
- Ensure that the area safe from the general public if props are to be left in position unattended.
- Do not string or tie anything to the props.
Prop Removal Checklist
- Start by planning the job.
- Always wear the appropriate safety equipment when using this equipment.
- Ensure that the work area is cordoned off to prevent public access, only essential people should work in the area.
- Ensure that the props are removed by qualified people who have the necessary knowledge and experience to do the job safely
- Do not remove or adjust any prop until you are certain that it is safe to do so.
- Always return the equipment to the hire company in a clean condition.
Always seek professional advice before undertaking any propping / shoring projects. A propping job that goes wrong can be disastrous, endanger lives and be an extremely expensive exercise to repair.