The Efficiency of Pipe Jointing Compounds
Comparison of Their Performance to That of Lead—Three Questions That Must Be Answered—A Case in Point—Behavior Under Crushing Stresses
THE great difference in cost between lead and the non-lead joint materials make it an obligation on the part of water works engineers and executives to satisfy themselves as to the efficiency of the non-lead products. Although these materials have been in the market for about sixteen years, and have been used in increasing quantities during that period they are still regarded by the great majority of water works men with more or less skepticism.
The facts of the case, as set forth in a discussion before the New England Water Works Association, at its March meeting, are that lead has proved to be such an excellent material for joints, and workmen have become so well trained in its use, that engineers and superintendents have naturally and rightly hesitated to substitute for it a substance with which they are unfamiliar and upon which there is a relatively small amount of data as to its efficiency.
The writer has used the two substitutes known as Leadite and Lead-Hydro-Tite for over eight years in various localities and under varying conditions, with very satisfactory results, and as a consequence has acquired a great degree of confidence in them. The water works profession, however, must be from the very nature of its work, very conservative in adopting untried methods and materials and is bound to demand something more than the testimony of a few of its members, that a certain thing “works all right as far as they know.”
The purpose of this short review, then, is not to take a partisan stand in favor of any joint material, but to impress upon the members of the Association the fact that these substitutes for lead are worthy of careful consideration and investigation in view of the present prices of lead and labor. It is to be hoped that a general discussion may bring out some new facts and stimulate further investigations.
To the manufacturers the writer would suggest that, having now established the comparatively low cost of their products in the minds of the water works trade, they devote more energy to experimental work, to enable them to answer with definite figures the questions to which a thorough and thoughtful water works man must have an answer before making what would otherwise appear to him a hazardous change.
The most important of these questions are as follows:
- How do joints of these materials compare with those of lead as to tightness under normal conditions?
- What of the possibility of blown joints under high pressure due to water hammer, etc.?
- Will the joint have sufficient strength to resist stresses due to bending moment when support is removed from a considerable length of pipe as a result of settlement of hack-fill or nearby excavations for services, etc.?
On the first question the writer is able to submit evidence derived from actual experiment. In the summer of 1917, the Weymouth Water Works laid 3,400 feet of 8″ pipe from which no services were taken until the following season. The joints were of Lead-Hydro-Tite and the new gate controlling this line was by-passed with a 5/8″ Empire meter testing 99% in 1/32″ opening. For the final measurements the flow was too small for accurate measurement by meter, and a force pump was used pumping from a pail, into which water was fed by a standard gallon measure. The results as to leakage per linear foot of joint are shown in the following table, and would, according to available data on the subject, be considered excellent for lead joints:
Tests for Leakage from Lead-Hydro-Tite Joints Idlewell Extension, North Weymouth, Mass.
* By pump and gallon measure.
Pipe was 8-inch Class E. New England weights.
Average pressure, 7Q pounds.
Leakage measured by 5/8-inch Empire Meter, registering 99 per cent. on 1/32-inch opening at 70 pounds gage pressure.
This work was done by a man having one season’s experience with leadite, exercising the ordinary degree of care usually required by the writer on this class of work and the results should give a fair indication of the degree of tightness to be expected under average conditions.
As to the matter of joints blowing out, the writer can only say that he has never known of a Leadite or Hydro-Tite joint blowing out. In fact the strength of these materials and their adhesion to the metal as demonstrated when a joint is dug out seems to be sufficient evidence of their safety in this direction without extensive experiment.
Behaviour Under Crushing Stresses
As to the behavior of this type of joint when subject to crushing stresses such as occur when portions of a pipe line are left unsupported by the settlement of backfilling, the writer has been until very recently in doubt, in fact, uncertainty on this one point has prevented him from giving these materials his unqualified endorsement as substitutes for lead. This doubt has been pretty much dispelled by the results in a case that has recently ccme to his attention.
The Berlin Water Company, of Berlin, N. H., built last year a new dam from which an 18-inch cast iron main was to lead to the city distribution system. About two lengths of this pipe were in the dam, and on the end of the first length on the down stream side an 18-inch valve was placed. Joints were all of Lead-Hydro-Tite. Before any more pipe was laid the reservoir was filled and some time later a washout occurred which completely undermined this length of pipe, leaving it and the gate suspended in the air and supported solely by the material in the joint near the masonry. Just what the maximum stresses were in the joint it is neither easy nor necessary to compute, but it seems to the writer that they are as great as are apt to be encountered under ordinary working conditions. (See illustrations).
The writer has not attempted to take up the methods of using these compounds or the minor difficulties attending their use for the first time with inexperienced men and incomplete equipment. These points have been covered in previous papers before the association and in the literature with which the manufacturers keep us abundantly supplied.
Requires Courage to Adopt Substitutes
It does unquestionably require considerable courage and considerable faith to give up the good old lead and substitute these new materials in the face of the inevitable opposition from caulkers and doubt as to the outcome of the first day’s work. The point that the writer wishes to make and to urge very strongly, however, is that we water works managers and engineers cannot, with a clear conscience, go on using an dspecifying lead, if these other substances are safe and suitable substitutes. And it is “up to us” to find out whether or not they are safe and suitable or to make every possible effort to find out.
The bulk of the evidence so far all points in one direction—in favor of the substitutes. In the discussion that is to follow, let us hear from the other side the unsatisfactory experiences, which for our present purpose of getting at the truth, are perhaps the most valuable of all.
Commissioner of Public Safety Hamilton recently appointed 28 men to the fire department, their appointments becoming effective April 1.
Four-State Section to Meet
The 4-State Section of the American Water Works Association will hold a meeting at noon on Friday, April 16, at the Belevue-Stratford Hotel, Philadelphia, at which time the mayor of Philadelphia will outline the needs of the city in connection with its increased water supply. A good attendance of the members is expected, and an interesting session.