By Colin Rice
Colin Rice Exploration Drilling Advisory - www.colinrice.co.za
Let’s take a look at some examples of guards and barriers and see how they compare to the characteristics of good guards.
This is the fourth article in Part 1 of our Technical Series on Guarding and Safeguarding. Click here for an outline of the entire Technical Series on Guarding and Safeguarding.
The previous article discussed the characteristics of effective guards, now let’s look at the design and construction of some examples.
A good guard?
The guard shown below has been erected to prevent a person making contact with a series of V-belts and pulleys. The guard is also there to prevent a failed V-belt impacting a person.
Does this guard meet all of our criteria?
The guard is manufactured from what appears to be light gauge expanded metal and a steel cowling – the construction appears to be robust and clearly it would not be possible for a person to make contact with the rotating parts. The construction is strong enough to prevent a failed V-belt impacting a person.
The openings in the expanded metal allow easy visual access of the parts being guarded (this is so that the components can be inspected on a daily basis) and the guard is bolted to the machine.
I suggest that this is an example of a well designed and constructed guard. Let’s now look at some examples from drill rigs.
The photograph below shows a guard placed to cover an opening in the base of a mechanical spindle drill rig. The purpose of the guard is twofold;
to prevent a failed prop shaft flying out of the opening and
to prevent a person making contact with the rotating prop shaft.
Does the guard meet the criteria for an effective guard?
The guard is manufactured from heavy gauge expanded metal with small openings and so it probably would contain any debris that may fly out of the opening in the event that the prop shaft fails. The small openings and the position of the guard will prevent a finger for example, from making contact with the rotating prop shaft.
The guard allows visual access and it has clearly been designed (with hinges) so that it can be easily opened so that the component that is being guarded can be inspected on a regular basis. The hinges however have been welded to the base of the drill rig and this is not recommended – we should never weld on drill rig mast or support structure.
It is not terribly clear in the illustration, but the guard is secured by two “wing nuts” – these have been fitted so that the guard can be quickly removed for pre-start inspections – it is understandable why the contractor did this but in terms of our criteria it is a defect.
All in all, the guard is probably effective save for the welding and the wing nuts.
The second example shows two sets of guards. The large structure separating the drillers work deck from the quill rod / rotation head is placed to prevent the driller from making contact with the rotating quill rod and to prevent him being impacted by a failed quill rod or failed part of the rotation head.
The guard also extends over the top of the drillers deck and so also acts as “fall-on” protection in the event that a component falls from above the drillers deck.
These guards appear to be robust and so they would probably be effective in protecting the driller from being impacted by a failed component as long as he remains on the work deck.
It is not clear from the photograph if the structure is removable.
The photograph also shows a smaller hinged guard, this smaller guard is placed to prevent a person from making contact with the rotation head and / or the rotating quill rod. This guard must also prevent a failed component impacting a person.
Again it is unclear how the guard is secured but even if it is well secured, it is too short to be effective. In the photograph the rotation head is at its lowest point on the feed frame – if it were higher, then a person near the drill rig would be exposed to any potential flying debris.
Guards such as the one in this example are commonly seen on drill rigs operating in South Africa and they are fitted to suit our legislative requirements. Understandably, manufacturers do not supply this level of guarding - every mine has a different view on what should be guarded and what a guard should look like - manufacturers can be excused therefore for supplying drills with no guarding at all !!
Hoists and winches
Winches and hoists are potentially extremely hazardous and so it is essential that we address the hazards posed by these components.
All modern hydraulic longstroke drills have a main hoist and a wireline winch mounted on the deck of the rig. Whether it is the main hoist or the wireline winch, the moving wire rope has to move across the width of the hoist drum and also, as the depth of rope on the drum changes, the path of the moving rope also changes. Any guard on the hoist or winch must therefore have an opening that is large enough to allow the wire rope to travel without impinging on the guard. This means that the opening must be large and so to a great extent, negates the effectiveness of the guard.
In most commonly available hydraulic long stroke drills, both the main hoist and the wireline winch are mounted on the deck and so can be easily accessed from ground level even if the drill is jacked up in its set-up position ready to drill. In addition, on most drills, the Driller does not have good visual access of the winches. Given these constraints, the question is – how do we adequately guard a hoist or winch?
I am not certain that we can adequately “guard” a hoist or winch but we have to make an effort to prevent a person from making contact with the equipment. I believe that this an excellent application for an interlocked barrier mounted on the drill deck - this would be easier to engineer and would provide a far greater level of protection for the crew.
The main components of a drill rig that will get hot enough to cause injury is the exhaust system and possibly the diesel motor itself. Exhausts and silencers have attracted a great deal of attention and I have seen many different attempts at guarding these components, but these are often not very effective. The attempt shown in the photograph below is an example of a poorly designed guard!
I believe that exhaust pipes and silencers are best guarded by wrapping in insulating materials. A number of different materials are available and they provide a much neater and more elegant solution. An example is shown below.
Barriers or barricades are required to prevent people or animals from entering an area where there is danger. In a drilling context, the danger may be represented by the drill rig itself or other piece of equipment, chemicals stored on site or open sumps for example.
Barriers must therefore be strong enough to prevent access and they must be positioned so that access is not possible by a person stretching his arm out for example .
We must distinguish between barricades used to prevent access and barriers used to demarcate areas on a drill site
In the picture on the right hand side, expanded plastic barricading has been used essentially to demarcate an area where waste bins are placed. In this instance, the expanded plastic does a decent job of demarcating the area but it will not prevent access to the waste bins by an animal.
In the picture on the left hand side, expanded plastic barricading has been used to prevent access to an series of open sumps. The sumps are very close to the drill rig and I am not sure that the expanded plastic would prevent a person falling into one of the sumps if he slipped.
In this particular case, the drill site was on a hillside in an area that was very difficult to access, I would argue therefore that, in this instance the expanded plastic was adequate.
In easier to access locations where it is practical, hard barricading of open sumps is preferred as shown in the picture below.
We must be practical!