Part 54 (2/2)

Where--

c = cost per bbl. of cement, or $4.45.

n = cu. ft. in one bbl. (taken at 3.5 here).

s = ratio of sand to cement, or 4.

d = inside diameter in inches.

t = thickness of pipe in inches.

l = length of pipe considered, or 1 ft. here.

Then:

c l [pi] (dt + t) Cement-cost per foot = --------------------------, n s 1.1 144

which gives here =

4.45 1 3.142(dt + t) ------------------------------- = 0.00631(dt + t).

3.5 4 1.1 144

This gave the following cement costs per lineal foot:

Diameter, Thickness, Cost ins. ins. per foot.

6 1 $0.0571 8 1 0.0730 10 1-3/8 0.0998 12 1 0.1278

The sand cost was based on 15 cts. per cubic yard for loading, and a haul of two miles of 1 cu. yd. to the load, making five trips per day, at $4 for man and team. It bears a constant ratio to cement cost, being 11.2 per cent. of the cement cost. The labor cost of making was based on the foreman's estimate that a foreman, tamper, mortar mixer, and water man should finish 250 joints a day of 6 or 8-in. pipe. For the 10 and 12-in. pipe, the labor was a.s.sumed to be greater in proportion to the material. The foreman was taken at $3, one man at $2.50 and two at $2.

The cement for painting the inside was neglected. Hauling the pipe to place was taken at twice the cost of hauling the sand per mile, and a haul of 4 miles was a.s.sumed. The cost of laying was based on a foreman's estimate of 2 cts. per foot for trench, and that one man to lay, one man to plaster the joints, one helper and one man to back-fill would lay 600 ft. per day of 6 or 8-in. pipe. The larger sizes were a.s.sumed to cost more in proportion to their material.

These various costs gave the following results for small size pipe:

--Cost per foot for-- 6-in. 8-in. 10-in. 12-in.

pipe. pipe. pipe. pipe.

Cement $0.057 $0.073 $0.099 $0.128 Sand 0.006 0.008 0.011 0.014 Labor 0.019 0.019 0.026 0.034 Hauling 0.024 0.032 0.044 0.056 Laying 0.024 0.024 0.032 0.042 Trench 0.020 0.020 0.020 0.020 ------ ------ ------ ------ Totals. $0.15 $0.176 $0.232 $0.294

The above costs show that the pipe in place costs about twice as much as pipe in the yard, even with cement at $4.45.

[Ill.u.s.tration: Fig. 270.--Bordenave Pipe for Swansea, England, Water Works.]

~MOLDED PIPE WATER MAIN, SWANSEA, ENGLAND.~--As a good example of foreign practice in molded pipe conduit work a water main constructed at Swansea, England, has been selected. This pipe line had to operate under a head of 185 ft.; it was constructed under the patents of the French engineer, Mr. R. Bordenave, who has built many miles of the same type of conduit on the Continent.

Fig. 270 shows the construction of the pipe, the drawing being a part longitudinal section through the sh.e.l.l at the joint. The pipe consists of an inner and an outer reinforcement separated by a sheet steel tube and all embedded in a 1-2 mortar. Both inner and outer reinforcements consists of longitudinal bins of cruciform (+) section wound by a spiral bar of the same section wired to them at every intersection. Only the outer reinforcement and the steel tube are considered in calculating the strength of the pipe, the inner reinforcement being considered as simply supporting the mortar.

_Fabrication of Reinforcement_.--The steel tube is made of 1 mm. (0.04 in.) thick sheets of steel bent to a cylinder and jointed longitudinally by welded b.u.t.t joints, welded by a blow pipe using acetylene and oxygen.

Tests of this welded joint by R. H. Wyrill, Waterworks Engineer, Swansea, showed it to be quite as strong as the unwelded steel cut from the sh.e.l.l. The circ.u.mferential joints of the tube were made by turning up the edges of the sheets and welding them; this gives a flexible watertight joint. The tube was made in lengths of 9 ft. 9 ins. and its ends were turned up all around; just back from the turned-up ends a vertical sheet steel collar was welded to the tube to form a strip end for the external coating. These details are shown in Fig. 270. When the tube for a length of pipe is completed the inside sh.e.l.l reinforcement previously made is slipped into it and the outside sh.e.l.l reinforcement is formed on it as a mandril, as shown by Fig. 271.

[Ill.u.s.tration: Fig. 271.--Applying External Reinforcement to Bordenave Pipe.]

[Ill.u.s.tration: Fig. 272.--Casting Bordenave Pipe at Swansea, England.]

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