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... December 2011 |
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Small Cover Lifters page added. Access through menu bar above .... |
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Manhole Cover Lifters
including the Manhole Buddy range
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This site provides an overview of manhole and drain cover lifting practices with numerous links to detailed information on our various product offerings
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Francais
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Nederlands
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November 2011
New folding Manhole Buddy KeyTecTM design
New Manhole Buddy VacTecTM vacuum lifting attachment
Summary information within this page
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Manhole cover lifters come in all shapes and sizes, but most share a common feature - they attach to the manhole cover using a form of lifting key. These lifting keys fit into slots in the manhole cover. The one exception is the Manhole Buddy MagTec, a magnetic attached manhole cover lifting system. Significantly, no cover lifting keys are needed with the MagTec. However, whilst Manhole Buddy MagTec excels in the most common applications, there is still a place for key-based attachment, most notably on non-metallic covers. First off, it is worth reviewing the general methods and issues associated with lifting manhole covers. The subject has been divided into sections and you can skip to any using the links below:
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Lifting Manhole Covers by Hand .... best advice “DON’T”
There are still people who will lift manhole covers using levers to pry the cover out of the frame and then by applying their hands directly onto the cover. By any measure, this is an extreme foolhardy activity. Manhole covers come in all shapes, sizes and weights. Amongst the multitude of dangers present when trying to directly handle manhole covers, the greatest is the risk of trapping hands or feet between the cover and the frame or the ground. Thereafter, the thickness and weight of a cover will probably only become apparent once lifting is in progress - that could be a nasty surprise. And the environment surrounding the manhole cover will influence the ability to lift it – if the manhole cover is in a raised position, bordered by a wall or fence, surrounded by an uneven, broken or slippery surface or temporarily obstructed by a vehicle, it becomes difficult to adopt any form of safe lifting posture. And of course the vast majority of manhole covers weigh significantly more than the manual handling limits advised by the Health & Safety Executive – back injuries are part and parcel of manually handling manhole covers. Put simply, manhole covers should never be lifted by hand!
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Lifting Manhole Covers with Handheld Lifting Keys
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More commonly, people manually handling covers use manhole cover lifting keys. These too come in all shapes and sizes, because there is a range of sizes and shapes of key slot. Drainage engineers usually carry a number of manhole lifting keys to cover the range of manhole covers they are likely to encounter. And one of the obvious risks is the temptation to improvise when the correct key is not available. An ill fitting key increases the risk it will not be retained in the manhole cover slot and the manhole cover will become detached.
However, assuming the correct manhole lifting key is available, the user now needs to adopt a good lifting posture. Consider for the moment that a typical manhole cover will be at least 600 mm wide, many much wider. The user must straddle the cover, feet at least 700 mm apart, and attempt a lift with straight back and bent knees (see HSE Manual Handling Guidance).
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Many 600 mm square drainge chambers are covered by two triangulars manhole covers, fitted with inter-connecting bolts. When lifting such an arrangement, the natural movement between the two parts creates an ungainly load, which increases the dangers for the user as they stand astride the drainage chamber. Even if two people share the load, each having one manhole lifting key, they need to achieve good co-ordination of movement and be able to react in unison to any unexpected movement. And the potential risks associated with refitting a manhole cover over an open chamber are probably greater, than when removing it.
And once again, there is the issue of weight. Most covers will exceed the advisable lifting limit for one person, many will be more than double the limit, hence beyond the range for a two-person lift. The dangers inherent in manually handling any manhole cover, whether by direct application of hands, or through hand-held manhole cover lifting keys, are clearly considerable - so in all but the most exceptional circumstances, it makes sense to adopt the approach that manhole covers should not be lifted manually!
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Traditional Manhole Cover Lifting Systems
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There are a myriad of manhole cover lifters on the market, reflecting the requirements of different sizes, shapes and designs of manhole cover systems. The majority of manhole cover systems require the cover to be lifted vertically to clear the frame. A minority of designs try to minimise the lifting requirement and instead facilitate sliding of the cover out of the frame. This approach has the potential to minimise lifting risks but the inherent installation constraints imposed by the design (usually only being able to withdraw in one direction) result in only a very small proportion of such covers being deployed. And even with these, it is still necessary to find some means of unseating the cover …..
Unseating or freeing a manhole cover from its frame is a significant part of the overall cover lifting activity. The manhole cover will invariably be well embedded in the frame as a result of passing traffic (foot or vehicular), dirt that has been deposited into the gap between the cover and the frame (whether naturally or otherwise) or perhaps just the effect of corrosion if the manhole cover has not been lifted for some time. The traditional (and highly inadvisable) method is to thump the manhole cover with a sledge hammer. Yes, it can often achieve the required result, but at what cost:
- damaged or broken covers
- strain or impact injuries to the person wielding the sledge hammer
- flesh or eye injuries from detached pieces of metal
- risks to other persons in the vicinity
Similarly, wedges, pry bars and crowbars can be used to force the cover out of the frame. These methods often involve hammering such tools into the gap between the manhole cover and the frame, so the same risks of physical injury, broken covers and flying metal particles apply.
With the notable exception of the magnetic attached manhole cover lifter (the Manhole Buddy MagTec), virtually all manhole lifting systems use the key slots to connect with the manhole cover. Whilst these fixed positions might ensure a cover is lifted evenly and uniformly, they sometimes create the need for undue force when trying to unseat the manhole cover – or put another way, they do not permit an unseating effort to be applied right at the edge of the cover, which is precisely where it is needed. That said, a commonly used method with this fixed position design of lifter is to apply the lifting force and then use some ‘shock tactics’ on the edge of the manhole cover, repeating the process until the seal is eventually broken. Such a method is an improvement on the ‘sledge hammer only’ approach but still introduces undesirable risks to people and equipment. There is a better way ....
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Manhole Buddy - Manhole Cover Lifting Options
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Manhole Buddy systems comprise two functional elements - a cover attachment device and a lifting trolley. Four cover attachment devices are now available:
MagTec magnetic attachment
KeyTec key-attached system
ChainTec 4 leg chain array
VacTec manually energised vacuum lifting device
All four attachments use a common lifting trolley, available in steel or aluminium. During lifting operations, the user is positioned well clear of the suspended cover and the open chamber, as can be seen in the images above.
Manhole Buddy MagTec is highly effective on a wide range of metallic covers and is generally unmatched in its speed of deployment and use. Inherent in its design are a number of significant advantages:
- Firstly, it requires no form of manhole lifting key - ask any drainage engineer how much time is spent cleaning out key slots in manhole covers and you’ll quickly appreciate the simplicity and efficiency of the configuration. Instead, you place the magnet on the manhole cover and operate the On-Off lever. Permanent magnets are used, so no external power or recharging is ever needed.
- Secondly (and in common with all Manhole Buddy configurations) it requires no physical lifting effort. The human input required is a downward action and the mechanical advantage inherent in the design reduces that by a factor of 2.3:1, relative to the weight of the cover. So it’s easy to lift and move heavy loads.
- The most effective method of unseating a jammed cover is to apply force nearest possible to the edge. With the Manhole Buddy MagTec, you can place the magnet wherever you choose, so you apply localised force where most appropriate on the cover. And better still, the Manhole Buddy lifting trolley has a secondary lifting position, delivering a mechanical advantage greater than 5:1 - this makes unseating covers a doddle!
- Portability and speed of deployment are unrivalled. The lifting trolley (whether Steel or Aluminium) can be comfortably carried in one hand and unfolded within 15 seconds. You then hook the trolley into one of three positions on the magnet lifting frame and start work. Up and running within 30 seconds at the most. Refolding the trolley at the end of the job is no more than a 15 seconds task, whereupon it can be stored neatly in the boot of a car!
Full product information, images and video clips can be found at www.manholebuddy.co.uk
Manhole Buddy KeyTec can be used on any cover with traditional key slots but is most commonly used on non-metallic covers, or large metallic covers where the capacity of the magnet might be exceeded. Central to the KeyTec configuration is a load spreader bar, which is secured to the manhole cover using threaded lifting keys. Connection to the lifting trolley is through the rotating lifting hanger (again, common to all three attachments). In this way, the unseating and lifting functions, first introduced with the MagTec configuration, are fully replicated. So, save for the fact that the keyholes now need to be cleaned out, Manhole Buddy KeyTec delivers safe and effective cover removal with unrivalled speed and portability.
Click here for detailed information on the Manhole Buddy KeyTec
Manhole Buddy ChainTec was created as a low-cost solution to lifting concrete-topped pavement covers with ovalised 20 mm key slots, but the universality of the lifting hook attachment has made it suitable for many other lifting applications. As with the other attachments, the rotating lifting hanger means a cover can be approached from any angle.
Click here for more detailed information on the Manhole Buddy ChainTec.
Manhole Buddy VacTec mirrors the basic functions of the MagTec magnetic system in that the lifting key slots are not used to make a connection with the cover. And just like the MagTec magnet, the VacTec attachment needs no external power or recharging - the user generates the vacuum state by 3 or 4 downward strokes of the charging handle. VacTec is most likely to excel on relatively smooth and flat surfaces such as concrete-topped pavement covers or paving slabs
Click here for more detailed information on the Manhole Buddy VacTec.
There are numerous alternative manhole cover lifters on the market. All are capable to varying degrees of lifting drainage covers. Many fall out of favour due to their size and complexity, including the need to assemble multiple parts, whereupon the user then reverts to the faster, albeit more risky, approach – using handheld manhole lifting keys. By contrast, the Manhole Buddy range delivers a common approach to handling the widest range of covers, in probably the fastest and safest manner. It is probably the manhole lifter most likely to deter workers from reaching for the handheld lifting keys. And that will undoubtedly save backs from injury!
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