|Wells Construction: Hand Dug and Hand Drilled (Peace Corps, 1980, 282 p.)|
|Section two: Hand dug wells|
At some point most materials and equipment involved in hand dug wells construction will be lowered into or pulled out of the well. This raising/lowering operation is so basic to wells construction that it will be discussed here in some detail. (See Fig. 5-1)
The raising and lowering operation will eventually become routine because it must be performed so often. Before the real well sinking work is begun, you should try to plan that routine, by considering what equipment will be used and how the workers should be organized to use the equipment safely.
FIG. 5-1. RAISING AND LOWERING OPERATION
Most major accidents or injuries that happen during the construction of a well result from faulty raising and lowering procedures. Accidents usually occur because someone forgot, didn't understand, or wasn't ready to perform his/her part of the operation. Remember that people's lives depend on how carefully this operation is performed.
There are many tools, pieces of equipment and items of knowledge that can help in this operation by making it easier and safer. They include:
· tripod, headframe;
Everyone coming in contact with this raising/ lowering operation should be thoroughly familiar with it. It is a good idea to do a couple of practice runs so that everyone understands exactly what is involved. Switch people around to help them understand what is happening at different points in the operation. It is also useful to have well workers lowered in and out of the well to help resist any later tendencies for joking while pulling on the rope. That way, everyone understands the reality of being suspended on a rope with no way to help yourself if a problem occurs.
Certain safety features should be followed:
· All workers in the well should wear hard hats;
· People are most safely raised or lowered in the well on a bosun's chair made of a board, log or other appropriately strong seat firmly tied to a rope (see Fig. 5-2).
· Nothing should ever be left lying on the ground near the opening of the hole. In a working situation, people can easily trip and fall, knocking loose materials into the well.
· It is also necessary to be concerned with the safety of people other than the well workers. Passersby have a natural curiosity and wish to find out what is happening. Before construction is begun, it is very useful to establish some kind of perimeter, or even a fence, which is to be crossed only by those actually involved in construction. This may be difficult enough to enforce during working hours but becomes more important and more difficult at night and on nonworking days. It may then be necessary to use a guard to remind passersby that they are not supposed to be in the area. The guard can also make sure that tools and supplies are not taken from the site.
FIG. 5-2. TWO SUGGESTED DESIGNS FOR A BOSUN'S CHAIR
It is very helpful to have a set of signals to control raising and lowering. These should be voice commands as well as hand signals. Four simple signals will usually cover most of your needs (see Fig. 5-3).
FIG. 5-3. HAND SIGNALS
C. Lowering Supports, Tripod, Headframe
Some type of lowering support is necessary when digging, except in very shallow wells. It provides a much safer and easier way to lower tools and materials for use in the well and remove the soil and rock dug up in the hole. Such a structure usually has 1 or 2 pulleys which can be suspended over the center of the hole or offset. The offset arrangement is often easier to work with.
Choose the type of lowering support most suitable for the kind of work you expect to be doing and the materials you have available. (See Figs. 5-4, 5-5, and 5-6.)
FIG. 5-4. WOOD LOWERING SUPPORTS
FIG. 5-5. TRIPOD
FIG. 5-6. HEADFRAME
If they will not obstruct other operations,the lowering supports can be erected before you begin digging. Or, more often, erect them after you have dug a meter or two and passing buckets by hand in and out of the well begins to get difficult.
It is the operation of this unit which will largely determine the safety of the workers in the hole. Emphasize this major point to all workers and visitors at the well site. Also, observe these six points on safety:
1) Lowering and raising materials and people should always be done with enough people on the rope. It is dangerous to rely on one or two strong individuals. Using several people assures control of the load even when a hauler trips or is otherwise unable to continue supporting the load, when people are in the well, or when someone is on the rope being raised or lowered in the well.
2) Someone should always be posted at the well edge, watching the load being worked within the well. In case of a problem this person can alert the haulers or other workers. The same individual could also hook and unhook buckets, loads, and people from the rope and ease them into and out of the well.
3) When pulling large buckets full of soil, rock and water from the well, two people may be needed to pull the heavy bucket out of the well and place it on the ground next to the well for later dumping.
4) There should be an established set of signals which the person at the well head will use to direct those hauling on the rope. (See Fig. 5-3) These signals should be taken very seriously and are to be used only when necessary, but with no hesitation when they are necessary. Practice in using and understanding the signals is advisable.
5) Throughout the well sinking process be especially careful that nothing falls into the well. Even a small pebble unknowingly knocked into the well can cause serious injury to a worker at the bottom if it falls from a distance. Take preventive measures. Be careful how you work around the edge of the well.
6) Always leave a safety line hanging in the hole. This is a rope tied off at the ground surface which can be used in an emergency as an exit from the well.
D. Other Raising/Lowering Arrangements
While lowering supports have been found to be the easiest and safest form of entry and exit, many other methods have been used. In these other methods tools and materials are lowered by rope by people standing next to the hole. People may be raised and lowered in this way but it is usually easier for individuals to make their own way in and out of the hole by climbing up and down:
· an anchored stationary rope which may be knotted at regular intervals; a rope ladder; or
· a regular wooden ladder which may be constructed in stages for use in deeper wells and anchored to the walls of the hole.
E. Common Raising/Lowering Problems
· Lack of tools or materials from which to make the equipement necessary for the raising/lowering operation
This is rarely a real problem because some way can always be
found to raise and lower people
and supplies if you and the local people are committed to constructing the well.
· Equipment breakage
This is usually due to misuse by overstressing or old age.
Misuse can be prevented by careful
work habits and frequent inspection of the equipment.
Equipment will gradually wear out with time. While this cannot be prevented,it can be anticipated, so that old equipment is replaced before it becomes dangerous.
· Lack of sufficient people to perform raising/ lowering operation
This too is more of a perceived problem than a real one. If there are enough people in an area to warrens digging a new well,then there should be enough available to help with this aspect of the work.
If vehicles are available they can be more reliable pullers than people. Workers can also easily raise and lower themselves where necessary. (Figs. 5-7 and 5-8)
FIG. 5-7. WHEEL RIM CAPSTAN
FIG. 5-8. LOWERING/RAISING ROPE ATTACHED TO VEHICLE
F. Useful Equipment
The lives of you and your workers will depend on the ropes you use, so be very careful in selecting rope.
Make sure that the rope you use is strong enough for the loads you will impose on it. (See Rope Strength Appendix, p. 267.) It should be inspected regularly for flaws and traying. If possible, use new rope. As rope ages it loses up to half its strength. You should take this into consideration during selection and use.
Hemp rope is usually available and is very suitable for wells construction, although contact with cement will speed its natural aging and deterioration.
Nylon rope is often available and suitable, although it will stretch as a load is put on it.
Wire rope is excellent, combining strength and small size although it is really only suitable for use with a winch. Wire rope should not be pulled by hand without the use of gloves as it tends to fray, leaving ends sticking out which easily cut the skin.
A few basic knots, when used properly, can help make the work easier and safer.
· bowline - This knot can be tied to form a loop of whatever size you need that will not slip or come loose. Its most common use is in rescue operations where people have to be hauled or lifted out of dangerous situations. (Fig. 5-9)
FIG. 5-9. BOWLINE
· square knot - This knot is used to join two ropes together. (Fig. 5-10)
FIG. 5-10. SQUARE KNOT
· half hitch - This is very commonly used to attach a rope around a solid object. Once tied, it is difficult to tighten the rope although the knot itself will only become tighter if the rope is pulled. (Fig. 5-11)
FIG. 5-11. HALF HITCHES
The use of two or three different kinds of buckets is often convenient for work in a well.
To avoid the possibility of tipping over while being lowered or raised in the well buckets should have two features (Fig. 5-12).
· handles attached to the bucket along its upper rim. Any weight in the bucket will tend to keep it upright.
· buckets should be deeper than wide, which concentrates the weight further down making the buckets even harder to tip over.
FIG. 5-12. BUCKET
Buckets, like ropes, should be checked regularly for defects. Particularly look for:
· a weak bottom;
· a worn handle/bucket junction;
· cracks or broken places;
· worn handle.
Discard rejected buckets, if possible, to avoid possible future confusion and unsafe use in the well.
Buckets may be used for different operations and their desired features will vary accordingly. Buckets used in excavation, such as removing soil and rock from the hole should have:
· handles that connect to the bucket rim;
· greater depth than width;
· reinforced bottoms;
· handle safety latches; and
· hooks in the middle of the handles.
Buckets used for cementing (lowering cement into the well) should have:
· handles connecting to the rim of the bucket;
· wide rims for pouring.
Buckets used for lowering and raising tools should have:
· handles connecting to the rim of the bucket;
· greater depth than width.
The use of a pulley will greatly facilitate well construction work. If unavailable, arrange a cross piece with a smooth surface over which you can pull the rope. It is far more preferable to pull the rope over a pulley than try to stand at the well edge and pull the rope straight up hand over hand. Ropes will wear much faster when pulled over even a relatively smooth surface than when a pulley is used and should therefore be checked frequently.
· Pulleys are often available as a unit with a hook. (Fig. 5-13)
· Pulleys can also be built with shaft ends. (Fig. 5-14)
· Pulleys may be mounted in hard wood blocks anchored to solid frame. (Fig. 5-15)
FIG. 5-13. PULLEY WITH MOUNTING HOOK
FIG. 5-14. PULLEY ON A SHAFT
FIG. 5-15. PULLEY MOUNTED IN WOODEN BLOCKS
5. Brake Post
The brake post is a log set in the ground 4 to 5 m from the well which, when the raising/lowering rope is wrapped around it several times, acts as a friction brake. This can help, especially when lowering heavy objects into the well, by allowing much easier control of the lowering speed. A person standing behind the brake post controls the lowering speed by the amount of tension he/she keeps on the rope as it feeds around the post and on to the well.
A brake post should be:
· located 4 to 5 m from the well straight out from the pulley (See Fig. 5-1.);
· about 25 cm in diameter, round, and smooth;
· set in concrete 1 m into the ground;
· set at an angle of about 60° from the well.