Machinery Versus Hand Labor in Pipe Laying
How Both Time and Money is Saved by the Adoption of Labor Saving Devices—Some Interesting Figures
THE great saving both in time and expense that follows the use of machinery in trenching, pipe laying and backfilling makes the adoption of this method as against the cumbrous and unsatisfactory hand labor very attractive to the water works superintendent. The following article (fives some important details in the work of use of labor saving machinery for this purpose and will be found of use to those contemplating the adoption of this means of doing the work:
The replacing of hand labor by machinery on the larger jobs is interesting as showing how much can be done by that method with a few men. In 1920 the New Bedford water works contemplated laying 6,600 ft. of 36″ cast iron pipe, in addition to the ordinary annual extensions which are necessary to keep pace with new building operations constantly creeping out beyond the limits of existing mains. Labor at that time was very scarce: to say nothing of the excessively high wages demanded. It was decided to purchase a 14B Bucyrus steam shovel with an extended dipper arm and a special trenching dipper of half yard capacity, which permits the digging of a trench with perpendicular sides and sufficient depth. We afterward used a 5/8 yd. dipper on the same machine with good results for the wider trenches.
Shovel Moved on Platforms
The shovel travels over the trench on platforms made of 10 x 10″ or 12 x 12″ green oak timbers made up in sections. These sections are long enough to give a good bearing on the sides of the trench and about six or seven feet wide. Three or four sections are used and the shovel quickly picks up the section behind and places it ahead as the work progresses.
In 1921 work was started on a line of 48-inch cast iron pipe about 10,000 ft. long. This work was located eight to eleven miles from the center of the city and the laborers had to be either boarded near the job or transported to and from the city each day.
“Clamshell” and Derrick Used
In order to facilitate handling the pipe, which weighed four to four and one-half tons each, a 14B Bucyrus “clamshell” and derrick, mounted on caterpillar traction was purchased. With this outfit and gasoline driven air compressors for handling ledge and large boulders, and gasoline driven pumps for handling water in wet trenches the work was accomplished by a crew of from fifteen to twenty men and two or three trucks with dump bodies.
The shovel travelled over the trench on platforms, as previously described, depositing the excavated material into trucks which dumped it into the back fill close by. The derrick closely followed the shovel, thus keeping the haul from the truck to a minimum. With the outfit described and reasonably good earth conditions from 120 to 180 ft. of trenching, pipe laying and backfilling per day was accomplished. The crew was so small that transportation to and from the job daily was an easymat ter.
Worked Alongside Trench in Sandy Soil
Some sections of the work were in sand, too soft to carry the steam shovel over the trench. Under that condition the excavating was done by a clamshell bucket on the derrick, laying alongside the trench. The banks were so slippery that it sometimes required quick work to get a pipe in the trench before the bank slid in. The work, with the exception of a little filling in of a low section which was completed early in the third season, was completed in two seasons laying off during the winter months.
All sorts of earth conditions were encountered; hard pan, with large boulders, quicksand, dry, sliding sand and even swamp where pile driving was necessary. The same derrick with the 30 ft. beam made an excellent pile driver. I can heartily recommend the outfit described to anyone having a big job of pipe laying to do.
We have used the shovel for some of the smaller jobs in the city; but for short lines scattered in various sections of the city it does not pay, as the cost of moving long distances is excessive.
Laying a Curve in the Pipe Line
Another interesting feature of the laying of the 48″ cast iron pipe was laying a curve of approximately 14° or 1,740 ft. radius with straight pipe. It was pronounced by all who saw it as a pretty piece of pipe laying, and was perfectly tight when the water was turned on. This curve was in swampy country and mostly laid above the surface of the swamp. It was well braced to prevent the joints from blowing out.
Leadite Used in Joints
Practically all the joints on both the 36″ and 48″ lines were made with Leadite and braided jute packing, which resulted in a great saving of labor, especially in wet trenches, where the digging and maintaining of larger bell holes would have entailed much more labor and expense.
As an illustration of the difference in cost of joints made with lead and Leadite; two lead joints were made at a cost for packing, lead and labor of $18.06 each, whereas the same items for Leadite joints cost about $4.42 each. It took three men one hour and forty minutes to make a lead joint, whereas the same three men averaged from six to eight joints per hour with Leadite. This does not take into account the extra cost for bell holes when lead joints are made.
Cost of the Two Jobs
The cost of the two jobs described was as follows:
Cost of 48-Inch Main Laid in 1921-1922-1923.
Class “B,” “C,” “D,” N. E. W. W. A.
Pipe $46.50 per ton, 18,813 ft.
Specials $130 per ton
Cost of 36-Inch Main.
Laid in 1920-21, 6,846 ft. Class “D,” N. E. W. W. A.
Pipe, $64.00 per ton.
Specials, $145.00 per ton.
Excerpts from paper read before the annual convention of the New England Water Works Association, at New Bedford.