Whenever manhole covers are removed and replaced it usually involves the use of a key lifting system. Different manhole covers will have different shaped holes so most engineers will carry a variety of keys so they can remove the cover that they are faced with. These lifting keys can be handheld or operated by hydraulics and both methods have their own advantages.
Handheld Lifting Keys
These keys are very simple pieces of equipment and can be transported easily, often on the person of the engineer. Even if the engineer carries a number of keys so they are prepared for any manhole cover, then they should be able to be carried easily.
Manhole cover lifting can be carried out by one or two people depending on the type of cover. If it is being lifted by two people then they will both need to use a separate key. Using a handheld key requires the cover to be removed manually so engineers will need to be trained in health and safety issues related to manual handling. If two people are lifting the manhole cover then they will need to make sure that they are both lifting at the same time so that the weight of the cover is distributed evenly.
Hydraulic Manhole Lifters
Manhole lifters that use hydraulics to do the lifting means that the engineers do not have to exert any physical effort in order to lift the cover. This helps reduce the risk of injury to engineers as well as making it easier and quicker for them to remove the cover so they can complete their job in less time. Most hydraulic lifters have a variety of attachments which means they can be used to open most covers in the same way handheld lifting keys can. The small dimensions of hydraulic lifters means that they can be transported in a van easily and if space is an issue then they can be taken apart and reassembled again in less than a minute.
Are There Any Alternatives?
There are some devices that use magnets to lift the manhole cover but these are not in common use. These machines often resemble hydraulic lifters. As with hydraulic lifters, no physical strain is placed on the person operating the lifter. These types of lifters also have the advantage of not needing a key to be able to lift the manhole cover which can save the engineer a lot of time and effort that might otherwise be spent in finding the right key that fits the cover.
Can Manhole Covers Be Lifted By Hand?
It is not recommended to carry out manhole cover lifting by hand because of the risks of personal injury. Prising the cover over open with a crowbar and then attempting to get the fingers underneath is a method that was used in the past but it places the engineer at risk. The problem with not using any type of tool is that the engineer has to get their hands between the cover and its frame in the ground and if their hand were to become trapped then it would cause a serious injury.
So there you have it, all of the different methods of removing a manhole cover in order to gain access to the manhole itself. It is, however, important to remember that inspecting a manhole is not a task that should be taken lightly. Making sure that you have both the necessary skills and equipment before attempting to carry out an inspection or repair in a confined space is imperative.
Further reference: http://www.hse.gov.uk/pubns/indg398.pdf
Health and Safety Executive – Making the best use of lifting and handling aids