CASTING SULFUR PIPE ISAAC BENCOWITZ Texas Gulf Sulphur Company, Inc., New York,N. Y.
line steel pipe. Steel pipe so lined, as well as pipe made entirely of sulfur combined with an aggregate, have proved to be resistant to attack by salt water and corrosive bleed water after 4-year exposure. It is suggested that possibly such pipe can be used for the conveyance of corrosive liquids. Since sulfur is comparatively inert, it should be proof against attack by certain acids and certain salt solutions and should also act as a thermal insulating material.
Preliminary studies indicate that sulfur may be used as the cementing agent in the centrifugal casting of pipe. Best results were obtained when the sulfur was used in combination with sand and a rather coarse aggregate such as coke. The strength of the pipe, together with :its resistance to thermal changes, was further improved by the addition of shredded asbestos. Such pipe withstands a hydraulic pressure of 95 pounds per square inch. Similar mixtures of an aggregate and sulfur can also be used to
F
OR many years sulfur was utilized variously as a construction material. It has been used to grout anchor bolts in foundation (IO). Mixed with sand it serves in the preparation of foundations for machinery. As early as 1921 L ‘ a l m every ~ ~ t conceivable thing was mixed with sulfur to obtain a suitable cement” (3), and recently extensive research a t Mellon Institute (6) resulted in material improvements of such products. In Ohio, sulfur plasticized with various materials has been used with considerable success as a jointing material ( B , I 2 , I S ) in the construction of brick roads. The inertness of sulfur towards many corrosive liquids suggests its possible use in the construction of pipes for the conveyance of troublesome fluids encountered in industry. It is realized, however, that the success of sulfur cements in numerous fields of applications does not necessarily lead to an a priori conclusion that a sulfur pipe can be successfully constructed. There is a likelihood that the crystallization of sulfur might develop internal stresses in the walls of the pipe and thurl cause cracks and deterioration. The work here reported, therefore, is of an exploratory nature. No attempt is made t o develop a final product suitable for immediate commercial exploitation.
patented his process in 1914 was centrifugal casting commercially feasible. After many years of experimentation he finally designed a mold in which the temperature could be controlled during casting. His machine (4) was water-cooled, and the pipes cast by his process were removed from the mold as soon as solidified and annealed to relieve internal strains. This annealing was eliminated in the Henry-Weitlung-Peake process in which the mold is kept a t the proper temperature by means of circulating mercury vapor. Following the experience gained in the production of cast-iron pipe, a machine was designed for the casting of sulfur pipe in which the temperature could be controlled.
Casting Machine The casting machine (Figure 1) consisted of a mold made of a 3 - f O O t length of standard 10-inch pipe jacketed by a 12-inch pipe. The two pipes were welded to 12-inch standard forged steel flanges on which the mold revolved. The feeding end of the mold carried an adapter flange held in place by means of four bolts. This adapter flange was intended to hold the molten mass in the mold while casting. Later it served to determine the thickness of the pipe wall. It can be easily removed when the finished pipe is to be withdrawn. The other end of the mold carried a blind flange which terminated in the driving shaft. The driving shaft consisted of two extra heavy concentric pipes welded together so that steam or water entering through the center could circulate around the mold and leave through the annular space of the shaft. The feeding mechanism consisted of a conveyor screw which moved the molten mix into the rotating mold. The conveyor is housed in a steam-jacketed pipe carrying a steam-jacketed hopper. During casting with the mold revolving, the feeding mechanism is advanced until it reaches the far end. The required material is then placed in the hopper, and as the feeding mechanism is gradually withdrawn from the mold, the molten mass is deposited continuously over the entire surface. The feeding is completed in 40 seconds. The mix, falling tangentially on the inside of the mold, is held in place by centrifugal force and forms a uniform pipe. During casting, steam circulates around the feeding apparatus and cold water around the mold. The mold is belt-driven and rotates a t 1000 r. p. m.
Historical Review One of the processes used in the preparation of pipes is known as centrifugal casting. In the application of this process to the casting of a sulfur pipe, it must be noted that molten sulfur mixed with a solid aggregate, in so far as it is a heterogeneous mass, is similar to concrete. Since the formation of a sulfur pipe, however, is due to the solidification of a molten mass, which results in various internal stresses, the technic of casting sulfur pipes is more likely to be similar to processes used in the production of cast-iron pipe than those in the concrete industry. For that reason an attempt was made to apply the technic of casting iron pipe to the fabrication of sulfur pipe. Though centrifugal casting of cast-iron pipes was not used on a commercial scale until 1922 (S), the advantages of centrifugal casting were realized a century ago. As early as 1809 Eclrhard patented a method of casting by centrifugal force. Many patents followed, but not until de Lavaud (3) 759
760
INDUSTRIAL AND ENGINEERING CHEMISTRY
ROTATING
FIGURE1.
VOL. 30, NO. 7
MOLD
MACHINEFOR CASTINGSULFURPIPE
Control of Wall Thickness Centrifugally cast iron pipe sometimes shows evidence of R spiral ribbon of metal. This is accounted for by imperfect balance and faulty axial alignment of the revolving mold (16). The machine was not built massive enough to enable perfect balance or accurate alignment to be maintained. The pipes cast in this machine, therefore, showed a decided spiral ribbon effect, and after the machine had been in operation one month, the ribbons became heavy spiral ridges. The sulfur was centrifuged out of these ridges, and practically pure sulfur remained in the low places. Needless to say, these pipes were worthless as they cracked on standing ‘or on being removed from the mold. It was undesirable to remedy the defects noted by making the casting mold and machinery heavier; therefore a makeshift procedure was adopted. The fluid material in the revolving mold is held against the wall by centrifugal force and is confined in the mold by the adapter flange. The 6-inch opening of this flange was large enough to allow free travel of the feeding mechanism. The initial aim had been to control the thickness of the pipe cast by regulating the volume of mix fed into the machine. This would also make it possible to determine the effect of the proportion of sulfur on the pipe. Since it was found that many of the pipes cast possessed spiral ridges and that these ridges could be avoided if an excess of sulfur was used, arrangements were made to enlarge the opening in the adapter flange so that the excess sulfur could be removed through this opening. The adapter flange a t the feed end of the mold was then made so that it held inside the mold only enough material to give the desired wall thickness. Anything beyond this volume flowed out of the mold. T o allow for this overflow, the volume of mix fed to the mold was one and one-third times that needed to give the desired pipe.
Segregation of Sulfur and Solid Aggregate Since Talbot and Richart (15)applied the concept of absolute volume in their extensive and systematic studies on concrete, the question of obtaining proper grading of aggregate to yield the strongest material was greatly simplified. The proper grading to obtain the densest combination and yet to contain the least voids, the least volume of fines, and the maximum amount of coarse material, is coordinated with such concepts as the fineness modulus ( I ) , surface modulus (14), surface area (7), and, more recently, the coefficient or effective fine-
ness. All this work has cleared the way for anyone working in cements. For centrifugal casting, however, much of this information is inadequate; in this field a density modulus becomes equally as controlling a factor as volume and surface factors. I n Centrifugal casting the particles do not “stay put:” Segregation occurs, and the magnitude of this segregation is a function of the volume and density of the aggregate particles. This is very much aggravated when sulfur is used as the binding medium, because the low heat conductivity of sulfur causes it to remain fluid for a considerable length of time and does not undergo changes in viscosity but freezes sharply a t one temperature. Segregation due to the formation of spiral ridges during centrifugal casting can be largely eliminated by increasing the fluidity of the mix. This, however, does not eliminate segregation along the entire length of the pipe. No matter what the aggregate, whether sand which is heavier than sulfur or coke which is lighter, some sulfur is centrifuged out of the mix and solidifies on the outside surface. The surface of the pipe is therefore richer in sulfur. Similarly, when the aggregate contains carbon black or a considerable proportion of fines, the centrifuged sulfur washes these fines to the outside surface. In either case the outside layer of the pipe is either rich in sulfur or rich in very fine aggregate, and the strength of the pipe is decreased. Obviously, this weakness can be avoided only by incorporating in this sulfur-rich surface sufficient aggregate of suitable particle size to give the densest combination with the least volume of binding sulfur. This can be accomplished by introducing into the mold prior to the introduction of the sulfur-aggregate mix, a definite quantity of sulfur-free aggregate. This dry aggregate must be sufficiently coarse to allow free penetration of the sulfur and must be of such particle size as to form a dense mass with the fines washed out by the sulfur. Materials passing through a 10-mesh and retained on a 20-mesh screen are satisfactory for the purpose. Generally, 20 per cent of the total volume of aggregate required in the formation of the pipe may be introduced as sulfur-free aggregate.
Removal of Pipe from Mold Unlike cast-iron pipes, a sulfur pipe does not shrink sufficiently on cooling to make withdrawal from the mold a simple matter. In this respect sulfur casting is similar to concrete casting. Furthermore, attempts to melt just enough of the outside of the pipe to facilitate withdrawal failed. The out-
JULY, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
side surface of the pipe does not melt evenly, and wherever melting does occur, the sulfur drains away, leaving the dry aggregate concentrated in places to form a tight packing. This difficulty was overcome by casting in the mold a skin of sulfur about I/4 inch thick. After solidification this layer is sprayed with a parting powder such as carbon black or finely ground coke. The regular sulfur mix is fed into the machine following the parting powder. After the pipe has been formed, the cooling water circulating around the mold is turned off and steam is introduced. After a few minutes enough of the outside layer of sulfur is melted and the pipe may be readily removed. Because of the parting powder, the outside layer of sulfur which comes out with the pipe peels off, leaving the surface of the pipe smooth, dense, and even. This process of casting a layer of sulfur against the mold is similar to that employed in'the Hume process (9, 1 1 ) of casting concrete pipes in which a layer of paraffin is employed.
Casting Procedure The following procedure was adopted in the casting of the pipes described in this paper. The mold is started with cold water circulating around it. The feeding mechanism is advanced until it reaches the further end of the mold, and as it is withdrawn, 0.2 cubic foot or approximately 22.5 pounds of molten sulfur are gradually fed into the mold. The mold is then allowed to rotate 15 minu6es until the sulfur solidifies into a layer inch thick. The feeding mechanism is again advanced, and as it is withdrawn, 0.05 cubic foot or approximately 3 pounds of fine coke are introduced gradually. This serves as the parting powder. Following this parting powder, 0.15 cubic foot of coarse aggregate (7.5 pounds of the coke passing through 10-mesh and retained on 20-mesh screen) is gradually fed into the mold, and this is immediately followed by the molten sulfur-aggregate mix which has been prepared in a steam-jacketed kettle. The mold is allowed to rotate for one hour. It is then stopped, the circulating cold water drained, and steam turned on. Two or three minutes suffice for enough of the outside layer of sulfur to melt allowing the withdrawal of the pipe from the mold. The pipe carries with it the remaining shell of outside sulfur which readily peels off. Sone of the pipes made in this investigation were annealed. Unless otherwise indicated, all of them had a wall thickness of 17/9 inches.
Procedure AGGREGATE. The aggregate used in the experiments is described in Table I. The asbestos, grade 7D, was obtained from Johns-Manville Corporation. The sand of the variety commonly used for locomotive traction was washed and dried. The coke and carbon black were petroleum products.
761
(71.8" to 77" F.). After each such thermal shock the pipe was subjected to a maximum hydraulic pressure of 45 pounds per square inch. If the pipe did not fail at this pressure, the cycle was repeated. The number of thermal shocks (T. S.) and the hydraulic pressure at failure were recorded.
Effect of Adding Coke to Sand The first series of pipe was made of coke of several different screen analyses. In every case such pipes were weak. A series of pipe made of sand alone yielded a few of superior strength. Unfortunately, they could not be duplicated. It was found, however, that when coarse coke was added to the sand, the strength of the pipe was increased and the results were readily duplicated. The addition of relatively large volumes of coarse coke (Table 11) yields a strong pipe, whereas the addition of large volumes of coke smaller than 10 mesh has a detrimental effect. Small additions of coke are apparently without effect. As the volume of fine coke (through 10 mesh) increases, however, the strength of the pipe decreases. This is due, no doubt, to the fact that the fines do not remain evenly distributed among the coarser particles but are segregated towards the outside of the pipe. TABLE11. EFFECTOF COKEON SULFUR-SAXD PIPE Carbon Sand Coke I Coke I1 Coke I11 Black Volume 55.56.57 0.5 1 .. .. 48' 0.58 0.17 .. 0.5 0.53 39 .. 0:i7 .. 27,28 0.6 .. 44,45 0.8 0.5 .. o:i7 0.58 .. 35 .. .. 0.53 31, 32,33 0.5 0.38 .. .. .. 64,65 a 10 after 3 T. S. (thermal shock). Pipe No.
-..
Sulfur 7
.. ..
I .
Strength of Pipe Lb./sq. in. 27 30 +45Q 38 23 20 8 5
The added strength imparted by the addition of coarse coke may be the result of two factors-density and particle size. Visual inspection of the appearance and texture of a cross section of the pipe reveals that the strongest pipes do not have a layer or "skin" of sulfur on the inside of the pipe. Theoretically, an aggregate of low density should eliminate this skin, found in weak pipes, by segregating on the inside of the pipe and combining with the free sulfur. This behavior, however, does not always occur; it has been found that even aggregates of low density are washed by the sulfur to the outside of the pipe. On the other hand, when the particle size of the low-density aggregate is large, this does not happen. Thus, particle size as well as density is a factor influencing the strength of pipes containing coke.
Gravel as Aggregate If high-density aggregates are added to sand, results equivalent to those obtained with coke Coke Gravel Gravel may be realized, provided the particle size is Through On Sand I I1 I11 IV I I1 I11 large. It is well known that the addition of a 3 10 31.5 100 .. ... .. ... ... certain proportion of coarse particles to an ag... 10 20 2:5 30.1 45 ... 45 ... ... 20 35 55.5 .. .., .. ... .. ... gregate makes a superior grading and yields a 20 80 , . . ., .. ... .. ... io6 stronger cement (8). The coarsest particle pres20 3s:4 .., .. ... .. ... ... 35 46 38:5 , . , . . .. ... .. ... ... ent in the sand passes through a 10-mesh sieve, ... 40 .. 3.5 .. , . . .. .. ... ... 60 , . , . .. ... .. 100 .. ,.. 100 and only 2.5 per cent is retained on a 20-mesh sieve. The addition to the sand of a certain proportion of coarse particles having the same density as sand, such as gravel, should thereTESTS. The bursting strength of the pipe was determined by means of hydraulic pressure. During the test the internal presfore increase the strength of the pipe since there will be sure was held constant at each £ increment for 5 minutes. no tendency for segregation of aggregates of equal density. The bursting strength of of the Pipes as idhmced by To demonstrate this effect,pipes were made with 1 volume thermal shock was also determined. Pipes were submerged for of sand and 0.5 volume of gravel which will pass through 5 minutes in water at 96 ',to 100 c. (204.8 to 212 F.) and then immediately chilled for 5 minutes in water at 22 t o 25 C. 10- and be retained on 20-mesh screen. The strength of these
-- TABLE
I. SCREEN ANALYSISOF AGGREGATE
Standard Screen Mesh
Analysis, Per Cent by Weight Coke Coke Coke Gravel
7
INDUSTRIAL AND ENGINEERING CHEMISTRY
762
VOL. 30, NO. 7
t,he thinness of the jointing film of the cementing medium. This fact, no doubt, should be of greater importance with Composition Volume No. of T. 8. sulfur than with Portland cement. Obviously, to obtain the Pipe No. 'Sulfur Gravel I Giavel I1 Gravel II'I before Failure best results a n aggregate is needed which packs densely under Pipes Contain 1 Volume of Asbestos 83 0.7 1 1 .. 27 the centrifugal force and does not segregate. Asbestos sug84 0.7 1 1 .. 27 gests itself as such a material. It does not segregate and, 85 0.7 1 1 .. 13 86 0.7 1 1 27 when subjected to centrifugal force, packs close against the 81 82 0 ..235 1 01. 6 6 01: 3 3 3 9 wall, squeezing the excess sulfur towards the inside whence it flows out of the mold. A series of pipes containing asbestos Pipes Contain 0.5 Volume of Asbestos 75 0.38 1 .. .. 2 (Tables IV and V) was prepared. I n every case the presence 77 76 0 . 2303 ..1 .1. 10 1 of asbestos increased the strength of the pipe. The advantage of asbestos was especially pronounced when the pipes were subjected to thermal shock; the strongest pipe was the one containing the greatTABLE IV. COMPARATIVE EFFECT OF ASBESTOSON SULFUR PIPE est amount of asbestos. No. of T. S. beTABLE 111. EFFECT OF GRADED GRAVEL ON SULFUR PIPE
fore Failure With-' Composition, Volumeout With Coke Coke Carbon asbes- asbes- Asbestos, Sulfur Sand I I1 Black tos tos Volume
7 -
Original Pipe No.
..
55, 56,57 48 39
0.50 0.58 0.53
1 1 1
0.17 0.5
2 7 , 52, 3 8 , 53 29 51, 44,45 65,65
0.55 0.8 0.38
1 1 1
.. .. ..
.. .. ..
.. ..
0 0
97 87,98,110 108,100 101 105,106
Sulfur ,-0.83 0.65 0.40 0.20 0.75
i;2
-*
..
0.17 0.5
..
o:i7
10 10 5
0 0
o
TABLE v. EFFECTO F INCREASED PROPORTION STRENGTH OF PIPE Pipe No.
4 3
OF
0.43-0.5 0.21 0.65 0.75 0.5 0.5-0.65 0.5
ASBESTOSON
Asb,estos in Asbestos Aggregate Strength of Vol. Yo Lb./sq. i n . 12.5 20 0.3 26-33 45 0.7-1.0 2.0-2.3 50-53 65 4.2 67.7 85 1 100 95
.
Sand Coke 1 Volume 1 1 1 1 1 1 1 1 0 0
Pipe
Wall Thickness
Pipe No. after Asbestos Addition
To determine the relation between wall thickand strength, a number of pipes having a 58,59, wall thickness of l 7 / ~ , 11/2,and 1 inch were pre72,73 50 pared from several different mixes. These were 42 tested in the approved manner. The data in 94, 95, 96 04 Table VI show that the strength of the pipe de68, 69 creases as the wall thickness of the pipe is reduced. 66 This effect is more pronounced in the case of pipes made of asbestos alone than those made of other aggregates, so much so that asbestos pipe of 11/2-inch wall thickness is weaker than any of the others of similar thickness. Pipes of gravel and asbestos, on the other hand, are quite satisfactory.
T . S. 5 18 23 30
30
T i m e of Casting The capacity of a given machine for making centrifugally cast sulfur-cement pipe is determined by the time required for
OF W A L L THICKNESS ON STRENGTH O F PIPE TABLE VI. EFFECT Pipe Containing 1 Vol. Gravel Pipe Made U p of 100Yo
Pipe Containing 1 Vol. Sand, wall 1 Coke I, 1 Asbestos Thickness No. -Strength-L b . / s q . in. T . 5.
compared favorably with similar pipes made I, 1 Gravel 11, 1 Asbestos Asbestos No. -StrengthNo. --Strength-with coke. Lb./sq.in. T . S . L b . / s q . i n . T . S. T o illustrate further the influence that Inches 105,106 95 30 110 45 5 84 75 27 density and particle size of an aggregate have 112, 116 35 117 40 132, 133 40 0 on the strength of pipe, a series of pipe was 1 113,115 12 5 ... .. 20.. 134 5 0 made using only gravel and asbestos as aggregate. These data (Table 111) show that the inclusion of coarse gravel in the aggregate (gravel II), which apOF COOLING ON STRENGTH OF PIPE" TABLE VII. EFFECT proximates the sand in screen size, results in strong pipe. This -Cooling Time-Strength of Pipe-is no doubt due to thesuperior grading of this type of aggregate. Pipe No, Normal Air-cooled Lb./sq. i n . T. S. On the other hand, pipes containing fine gravel are weak as a Min. Min. 60 .. 40 10 result of the washing of the fines to the outside surface. 124
rk
126 123 125 127 128 129 130
Effect of Asbestos on Strength It was repeatedly observed that fines must be eliminated from the aggregate to obtain strong pipe. Experience in many fields, however, definitely established that the strength of a heterogeneous combination of solid surfaces depends upon
TABLE VIII. Pipe No.
105 101 100 84
Weight per Linear
Foot Lb. 34 35 35 3s
Sand
i
1
Coke
I
Gravel
I Volume
Gravel I1
a Length, 37 inches; wall thickness, l'/s
25 20 15 10 5
14i Composition: inches. sand, 1 volume: coke I, 1; asbestos, 1. Wall thickness,
COMPOSITION AXD STRENGTH OF BEST PIPE^ Asbes-
t os 1
1
1
t o l'/i inches.
15 0 0 0 0 0 15
50 20 15 35 25 40 50
46
Sulfur
Sand
Coke
Gravel
---Strength-Internal No. Thermal Asbes- hydraulic tos pressure Tensile Shocks
Lb. per
Weight per cent
i
1
60 5 5 5 5 10 15
4.2 2.3 1
83
66 57 35
i6 ..
23
..
.. ..
..
60
7 11
17 11 9 5
95 85 65 75
sq.
Density
in.
152 136 104 120
30 30 23 27
1.77 1.87 1.87 2.23
JULY, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
the pipe to cool in the mold. The rate of cooling naturally depends on the diameter of the pipe, its wall thickness, its composition, and the speed of the mold. Normally it was found that, in casting a pipe having a wall thickness of 17/8 inches, an hour sufficed for the complete solidification of the mix. When pipes were made of asbestos and sulfur alone, a t
763
cooling. It is important, however, to allow a certain preliminary cooling before the blast of air can be applied. The strength of the pipe is evidently in direct proportion to the length of this initial cooling period; it increases progressively as the initial period is lengthened from 5 to 15 minutes. These data seem to indicate that further improvement in the strength of sulfur pipes can be made by annealing, although annealing cannot be recommended as a means of reducing the period of cooling.
Composition and Physical Properties Since the primary object of this research was to determine whether a sulfur pipe could be made and how to make it rather than to develop a finished product, only factors which affect the strength of the pipe were determined; the methods of testing were those which were found sufficient to yield relative results adequately. However, the general characteristics of the best pipes will be discussed briefly. Table VI11 gives the volume and weight compositions and the corresponding physical properties of a few pipes. The weight percentage of sulfur was determined by analysis of sections of finished pipe. The tensile strength was determined by the equation : where p
=
r
=
gage
t =
FIGURE 2. CENTRIFUGALLY CAST SULFURPIPESUNDER COMPRESSION TEST
tensile strength = p r / t internal hydraulic pressure a t failure, lb./sq. in. radius of pipe, in. wall thickness, in.
The tensile strength and density data are only approximate, since both sets of figures depend upon the internal and the external diameters of the pipe. These measurements were taken
INDUSTRIAL AND ENGINEERING’ CHEMISTRY
764
at three sections, and the average was employed for the wall thickness and the radius. The transverse strength of the pipe was determined as shown in Figure 2. Two pipes are placed on two 4 X 4 inch timbers at a span of 21/2 feet. Fourteen hundred fire bricks, each w 3ighing 8 pounds, were placed on the top of the pipes and allowed to remain for 18 hours. None of the pipes listed in Table VI11 broke under these conditions.
VOL. 30, NO. 7
hydraulic pressure after being subjected to thirty cycles of extreme temperature variation. During the hydraulic tests, lasting more than an hour, no sweating of the outside surface was noted, which indicated sufficient density of wall structure. Their crushing strength is estimated to be in excess of 860
Linings for Steel Pipe Sulfur may also be used to line steel pipe. To demonstrate the merits of sulfur-lined steel pipes, several specimens were prepared. Sections of pipe 8 inches in diameter and 6 feet long were first sprayed with a bituminous composition. A 61/&ch core, machined to a slight taper and wrapped in heavy kraft paper, was then centered in the interior of the pipe; a mixture, consisting of sulfur combined with an aggregate comprising 1 volume of asbestos, 1 volume of gravel I, and 1 volume of gravel 11,was poured into the annular space. Steam was maintained inside the core prior to and during the casting. After casting, the lining was allowed to cool. Pipes were thus produced having a 3/4-inch lining of sulfur cement (Figure 3). The lining in these pipes is apparently unaffected by thermal fluctuations of the steel shell due to the presence of the bituminous intermediate lining. The external pipe can be heated locally with an acetylene torch without cracking or otherwise affecting the lining.
Resistance to Corrosion
FIGURE5 . ORDINARYSTEEL NIPPLE LESS THANA YEAR OF BRINE SERVICE
AFTER
Two of the pipes made of sand and coke were placed in sulfur-mine bleed water, an exceedingly corrosive sulfurous fluid, so that the water flowed through the lower half of the pipe and on each side of it, and left the upper half exposed to the air. The pipes have withstood this treatment for almost 2 years without any visible deleterious effects (Figure 4).
pounds per square inch. They are highly resistant to corrosive fluids and weathering. Pipes retain their original characteristics after 5 years of outdoor exposure. It is suggested that the resistance to corrosion as well as the high insulating value of these pipes might be advantageous in the conveyance of certain solutions. Emphasis is laid, not on the excellence of the pipes thus far prepared in this research, but rather on the fact that pipes of such considerable strength can be made in an imperfect makeshift mold. This emphasis is felt to be justified in view of the fact that in centrifugal casting the product is highly susceptible to slight imperfections of the casting mold. It may be assumed that pipes of superior strength and thinner walls can be produced in a more solidly built machine.
Literature Cited
FIGURE 4.
CEKTRIFUGALLY
CAST SULFUR
PlPES
YEARSIN MINE BLEEDWATER
AFTER
2
An 8-inch sulfur-lined steel pipe was placed in service in the discharge line of a brine well on November 23, 1934. The saturated salt brine, mixed with air, which flowed through this line generally caused an ordinary steel pipe to fail in 4 months. The sulfur-lined pipe, after approximately 3.5 years of service, is still in good condition. The only visible effect is a 5/16-inchlayer of soft iron sulfide between the steel and the sulfur a t the ends of the pipe. This layer should not form when the ends are finished properly. Figure 5 shows an ordinary steel nipple taken from this line after less than a year’s service.
(5) Dueoker, W. W., Chem. & Met. Eng.,41,583-6 (1934). (6) Dueoker, W.W., and Schofield, H. Z., Bull. Am. Ceram. SOC.,16 (Il),435-8 (1937). (7) Edwards, L. N., Proc. Am. SOC.Testing Materials, 18, 482 (1918). ( 8 ) Furnas, C.G . , IND. ENQ.CHEM.,23, 1052 (1931). (9) Gibbs, F.H.,Can. Engr., 63,25 (1932). (10) Holly, C.E., Eng. Mining J.,107,279 (1919). (11) Niekerk, P.le R. van, I n d i a n Engr., 80,82 (1926). (12) Rueckel, W.C.,and Duecker, W. W., Bull. Am. Ceram. Soc., 14 (lo),329-32 (1935). (13) Schofield, H.Z.,Proc. 51st. Ann. Convention Natl. Paving Brick Assoc., Jan. 28, 1937. (14) Talbot, A. N.,Proc. Am. SOC.Testing Materials, 19,482 (1919). (15) Talbot, A. N., and Richart, F. E. Univ. Illinois Bull., 21, No. 7 (1923). (16) Wood, R.F.,Mech. Eng., 43,727 (1921).
Summary Pipes made of centrifugally cast sulfur pipe by the method outlined can withstand 95 pounds per square inch of internal
RECEIVED March 28, 1938. Presented before the Division of Industrial and Engineering Chemistry at the 95th Meeting of the American Chemical Society, Dallas, Texas, April 18 to 22,*1938.
