Assembly and Installation of Roof Bolts.

Roof bolts having expansion units are assembled in two simple steps. The plate is dropped on the bolt, and the expansion unit is screwed on the bolt three or four turns. The assembly is then ready to insert in the drilled hole.

Due to the difficulty encountered in handling preassembled roof bolts, the roof-bolting materials are usually transported to the bolting machine in separate packages, and the bolts are usually assembled as needed.

After the bolt is assembled and ready for installation, it is then started in the hole by hand and pushed the last part of the way by the tightening socket of the machine. The roof-bolt unit should not be rotated until the plate is firmly against the roof, otherwise the plug may reach the end of the threads before the bolt is properly tensioned.

Operators of roof-bolting machines should use care when applying upward pressure during the wrenching process that little or no torque is used to overcome unnecessary friction between the bolt head, or the wrench, and the roof plate. The plate should be fitting snugly against the roof before wrenching begins so that no threads are wasted in taking up slack before expansion begins. It is generally agreed in the mining industry that roof bolts should be tightened to a torque of about 150 foot-pounds. Numerous experiments have indicated that 50 to 80 pounds of bolt tension are developed for each foot-pound of bolt torque, with the factor of 60 chosen to determine conservative values of bolt tension. Using this value, a roof bolt tightened to 150 foot-pounds would have a tension of approximately 9,000 pounds, which is considered proper for most roof conditions since it is below the elastic limit of a mild steel 3/4-inch roof bolt or a 5/8-inch high-strength type.

The effectiveness of the anchor of roof bolts is determined by the installed tension and the characteristics of the roof at the anchor zone.

Any condition which produces high friction between the bolt head and the roof plate, or between the bolt threads and plug, should be corrected.

Overtightening can cause anchor failure in soft strata, and when such a condition is encountered, it will be necessary to limit the installed torque to below the 150 foot-pounds limit. Regardless of the situation, the main point in the tightness of roof bolts is the following: Bolts should be tightened to the point where they will exert enough tension on the rock surface to prevent any movement of the strata..

The tension-to-torque ratio and uniformity of developed tensions in roof bolts can both be improved by using good materials, lubrication of bolt threads and head, and the use of hardened washers between plates and heads.

Angularity Effects in Bolt Installation

When roof bolt holes are being drilled, sufficient care should be exercised by the operator of the drilling machine to insure that the axis of the hole will be perpendicular to the roof-bolt plate after installation. Many bolts have been installed in which the angular deviations are so pronounced that the usefulness of the installation has been destroyed.

Angular bolt installations are caused by one of the following factors:

1. Incorrect drilling angle.

2. Roof surface irregularities.

The second of these drilling factors can be eliminated by using care in locating the position for holes or smoothing out roof surface irregularities by chipping. Incorrect drilling angle can usually be corrected by bolt machine maintenance and adjustment.

Many times during your tenure as a member of the mine safety committee, you will be confronted by some of your associates with problems or grievances that are causing them concern, and, of course, are looking to you for possible solutions.

There are many types of safety grievances some of which are real, some of which are exaggerated, and some of which are purely imaginative. A safety grievance, no matter how trivial, can grow to giant proportions, if it is ignored or brushed off, and you then have a serious problem for which to find a solution. Regardless of the type, the time to solve a safety grievance is while it is still in the complaint stage, before it has become important enough to become a major issue.

The safety grievance may be real or imagined, but it is still important to the individual. As leaders in your union, you should act quickly to prevent a minor gripe from developing into a major problem. Immediate and sympathetic attention should be given to every safety grievance coming to your attention and thus eliminate the possibility of creating a serious internal problem among your

associates.

Like all other people, we ourselves complain at times about one thing or another. Like everybody else, we want to have our complaints taken seriously. Nothing rubs us the wrong way more than to have our complaints greeted with a stony silence or passed over with an insincere promise to do something about it. These reactions of ours are no different from the reactions of your people when they come to you with complaints which are not promptly acted upon. Probably half or more of all the major grievances among people have grown out of very minor complaints.

Before continuing with our discussion, we need to consider the question, "What is a grievance?" Before answering this particular question, suppose we explore the following:

1. Are grievances only the complaints which come to your attention through the regular grievance procedure?

2. If a man complains to a supervisor informally, is that a grievance?

ance?

3. If a man complains to a fellow worker, is that a griev

4.

If a man harbors a grudge but makes no complaint, is that

a grievance?

If a man thinks that something is wrong, but is silent, is that a grievance?

5.

The answer to our original question is, of course, that a grievance is anything which an individual thinks is wrong. Remember that as far as the individual is concerned and your concern as a member of the safety committee, in eliminating the trouble, there is no such thing as an imaginary safety grievance. The cause may be imaginary, but the grievance is real.

As a member of the mine safety committee, concerned with the safety and well being of your associates, should you be concerned with grievances brought to your attention? Consider the following factors involving reasons for finding quick solutions to mine safety grievances:

Does not each of these items affect the attitude of your associates toward their particular work duties, usually of a negative nature and in such a state of mind are more likely to relax their vigilance, forget their safety training, and thus become easy prey for injuries. Any grievances, whether within your particular jurisdiction or not, affects the safety of your fellow men, and you must be concerned and attempt to find a solution.

Dealing with Safety Grievances

In attacking this sort of problem, there are certain steps that you should follow in developing a solution, such as:

Talk with all people concerned to find out just what kind of trouble lies behind the grievance.

2. Make an independent investigation of the reasons given and determine whether they are justified or not.

3. Get the important or decisive facts together and make sure they are pinned down exactly before going any further.