Moser A.P., Folkman S. Buried Pipe Design

Подождите немного. Документ загружается.

Steel and Ductile Iron Flexible Pipe Products 379

Figure 6.64 Elbow and thrust restraint for condensate pipe.

Figure 6.65 External connection and thrust restraint.

380 Chapter Six

The power input to the heater will be measured and the heat

loss from heaters to outside ambient calibrated so that the net elec-

trical energy input to the test sections can be accurately measured.

The pipe system shall have a 5 percent slope, with the lower exit

being the low point of the system. After the installation is com-

pleted, the tank cover is bolted in place. A water source is attached

to the drain/fill, and a 5-gal surge tank is attached to the vent with

a tee fitting. The surge tank shall have a water slight glass and a

0 to 15 lb/in

static pressure gage. The other tee line shall contain

a shutoff valve on the side open to the atmosphere. With the vent

shutoff valve open, water is admitted into the tank through the

drain/fill until the tank is full and water spills from the open vent.

The vent valve is then closed and filling continues until the pres-

sure reaches 9 lb/in

gage (the surge tank should be about two-

thirds full as observed in the sight-glass). Tank pressure shall be

maintained for 48 h, and water up to 450F shall be circulated

through the carrier pipe to 24 h and drained. The hot water system

Figure 6.66 Condensate pipe in test cell.

Steel and Ductile Iron Flexible Pipe Products 381

shall be disconnected, and pipe ends shall remain open for the

remaining 24 h. The lower end of the carrier pipe shall be moni-

tored for water leakage during the next 24 h. At the end of the

48 h, the pressure is relieved by opening the vent valve, and the

water is drained from the tank through the vent drain/fill fitting.

c. Results: At no time during the test period shall water be

observed coming from the low end of the open pipe to indicate

water has entered the insulation through the pipe or end seals.

2. Resistance to water damage

a. Apparatus: The same system configuration used for the ground-

water infiltration test shall be used for the water damage test-

ing, except no pressure will be applied to simulate groundwater.

A “zero” groundwater pressure will produce a more critical test

situation for water damage. After the 48-h groundwater infiltra-

tion test has been inspected and approved, a system similar to

the system used in the groundwater infiltration tests, except for

the 0.25-in NPT female fitting, shall be set in the outer casing of

one of the sections and firmly epoxied and mechanically

anchored. The system will be connected externally with the

heater, pump, and valving system. The 0.25-in water line shall

be connected to the 150 lb/in

gage water system. Thermocouples

shall be set, as shown on the drawing, to record the surface tem-

perature of the conduit and water temperature entering and

leaving the carrier pipe.

b. Procedure: Circulation is begun and the heater is turned on. After

24-h later the heater is turned off for 24 h. This cycle is repeated

for 14 days. The cycle is continued, except that 150 lb/in

gage

water-dye solution is introduced into the 0.25-in pipe and “leaked”

into the insulation cavity between the core and casing. This test is

continued for 14 days or until water is flowing from the casing

relief valve or end seal. At the conclusion of the test, the leak is

stopped. The tank is drained, the pipe water system is drained,

and each section is examined for migration of leaking water.

c. Results: The spread of the “leak” at which the dyed water is intro-

duced shall be confined to one section of pipe. It shall be under-

stood that water leakage through the casing or end seals does not

constitute a failure.

3. Resistance to mechanical or structural damage (balance loading test)

a. Apparatus: A 3-ft-wide by 4-ft-deep by 11-ft-long steel tank is

equipped with vertically sliding panels in the end plates.

b. Procedures: A steady and constant vertical load of 200 lb/ft

applied to a 13-ft length of buried conduit system for 14 days. A

13-ft conduit system with a field joint in the center of the length

(the field joint is the same as will be used in the casing of a 20-ft

382 Chapter Six

length of pipe), pipe anchor, pipe supports, and a 4-in carrier pipe

and end seals will be anchored at one end of the tank with carrier

pipe lengths protruding from the sliding panels. This system is

installed on at least 12 in of firmly tamped soil over 6 in of sand.

Soil surrounds the conduit and comes to within 4 in of the tank

top. The soil used in this test is a fine blow sand and has been

selected because of the relative ease with which it can be handled

and because it can be used to simulate clay soil. A steel plate lid

is placed on top of the soil. The lid dimensions are 10 ft 10 in by

2 ft 10 in (allowing a 1-in clearance on all sides between the lid

and the tank perimeter). Hydraulic jacks are used to apply a

steady loading to the steel plate lid of 2000 lb/ft

.This load is

maintained for 14 days. During the 14-day loading period, ambi-

ent and water up to 450F, 500 lb/in

is alternately circulated

through the carrier pipe at 24-h intervals. The vertical positions

of the two end pipes are recorded every 8 h during the 14 days.

c. Results: The differential deflection shall not have been sufficient

enough to allow conduit or system to be damaged or deformed

enough to impair functioning of the system. The conduit envelope

shall not rupture or deform. The pipe supports shall not be

crushed, cracked, or abraded. Pipe anchors shall not fail.

4. Resistance to mechanical or structural damage (unbalanced

loading)

a. Apparatus: The test tank, conduit section, and jacking apparatus

used in the loading test, a steel plate 3 ft by 2 ft 10 in and a

source of 500 lb/in

gage water.

b. Procedures: With one end of the protruding carrier pipe capped,

introduce 500 lb/in

gage dyed water into the other protruding

end. Place the 3-ft by 2-ft 10-in steel plate at one end of the tank

over the buried conduit system. Apply a steady load of 2000 lb/ft

to the plate for 5 min. After removing the load and draining the

carrier pipe, uncover the conduit system. Disassemble the con-

duit and insulation at the field joint, and inspect the joint area

for water leaks. Inspect the entire system for mechanical or

structural damage.

c. Results: No water leakage from the carrier pipe to the surround-

ing insulation shall occur. Casing and insulation integrity must

be maintained.

5. Joint leakage test

a. Apparatus: Same as used in water damage test.

b. Procedure: The joint leakage test is performed simultaneously with

the water damage test. Each joint is misaligned with its mate by

1.5 with at least two of the misalignments in the horizontal plane.

As with the water damage test, water up to 450F is circulated in

Steel and Ductile Iron Flexible Pipe Products 383

the system for 24 h, at which time the heater is turned off for 24 h.

This cycling is continued for 14 days. At the conclusion of this

period, the tank is drained and the outer casing is removed.

c. Results: With the exception of field joints connecting the one section

with the 0.24-in female fitting, no other joints shall have allowed

any of the circulating water to have leaked into the surrounding

insulation.

6. Expansion/contraction test

a. Apparatus: Same as used in the joint leakage test.

b. Procedure: The expansion/contraction test is performed simulta-

neously with the joint leakage tests. Each joint is misaligned with

its mate by 1.5,with at least two misalignments in the horizontal

plane. As with the other tests, water up to 450F is circulated in the

system for 24 h, at which time the heaters are turned off for 24 h.

This cycling is continued for 14 days. With anchors at the ends and

at the elbow, the carrier pipe will expand and contract at the joints.

There is sufficient space between each carrier pipe and on the

machined surface of the ends to allow an uneven distribution of the

expansion/contraction. A schematic of the test setup is shown in

Fig. 6.53.

c. Results: With the expansion/contraction caused by the cycling

above, the system shall have performed satisfactorily without

any damage to the joint or leakage into the insulation.

Test procedures for condensate return piping The purpose of the tests

specified in this section is to demonstrate that the condensate

return piping meets the criteria specified by the Federal Agency Pre-

Qualification Procedures for Underground Heat Distribution Systems.

The carrier pipe shall meet MIL-P-28584 with one exception: The joint

to be supplied and tested in this protocol is a rubber ring joint not cov-

ered by MIL-P-28584. For that reason only, the following tests shall be

performed:

1. Joint leakage test and expansion/contraction test

a. Apparatus: Same as used for joint leakage tests for the high-

temperature pipe.

b. Procedure: A 3-in system consisting of 40 ft of insulated test pipe

and a 90 ell installed in the tank in gravel soil. Each joint is mis-

aligned with its mate by 1.5

with at least two misalignments in

the horizontal plain. The installation shall be made in strict

accord with installation guidelines, except for misalignments.

Water shall be alternately passed through the carrier conden-

sate pipe at a temperature of 65F (5) for a minimum of 2 min

and 300F (5) for a minimum of 3 min. Time intervals at each

384 Chapter Six

temperature level shall begin when the temperature of the water

reached the required range. The test shall continue until a min-

imum of 100 cycles shall be completed.

c. Results: No joints shall have allowed any of the circulating water

to have leaked into the surrounding insulation or soil.

2. Resistance of groundwater-infiltration.

a. Apparatus: The same apparatus as used for the groundwater infil-

tration and water damage tests for high-temperature pipe.

b. Procedure: A 3-in system consisting of 40 ft of test pi pe with

at least two 20-ft sections, a 90 ell, and one anchor at the ell

installed in the tank in a gravel soil. Each joint is misaligned with

its mate by 1

 with at least two of the misalignments in the hori-

zontal plane. The installation shall be made in strict accord with

installation guidelines, except for the misalignments.

The pipe system shall have a 5 percent slope with the lower

exit being the low point of the system. After the installation is

completed, the tank cover is bolted in place. A water source is

attached to the drain/fill, and a 5-gal surge tank is attached to

the vent with a tee fitting. The surge tank shall have a water

sight glass and a 0 to 15 lb/in

gage static pressure gauge. The

other tee line shall contain a shutoff valve on the side open to the

atmosphere. With the vent shutoff valve open, water is admitted

into the tank through the drain/fill until the tank is full and

water spills from the open vent. The vent valve is then closed,

and filling continues until the pressure reaches 9 lb/in

gage (the

surge tank should be about two-thirds full as observed in the

sight glass). Tank pressure shall be maintained for 48 h and

water up to 300F shall be circulated through the carrier pipe for

24 h and drained. The hot water system shall be disconnected

and pipe ends shall remain open for the remaining 24 h. The

lower end of the carrier pipe shall be monitored for water leak-

age during the next 24 h. At the end of the 48 h, the pressure is

relieved by opening the vent valve, and the water is drained from

the tank through the vent drain/fill fitting.

c. Results: At no time shall water leaks be allowed at the end seals

or shall water be observed coming from the low end of the open

carrier pipe.

References

1. American Association of Civil Engineers and Water Pollution Control Federation.

1982. Gravity Sanitary Sewer: Design and Construction.

2. American Iron and Steel Institute. 1971. Handbook of Steel Drainage and Highway

Construction Products. New York: Donnelley.

3. Armco Drainage and Metal Products, Inc. 1955. Handbook of Drainage and Con-

struction Products.Middletown, Ohio.

Steel and Ductile Iron Flexible Pipe Products 385

4. American Water Works Association. AWWA Standards M11, M9, M23, C150, C200,

C206, C300, C301, C303, C400, C401, C402, C403, C900, C901, C905, C909 and

C950. Denver.

5. Bishop, R. R. 1983. Course Notebook. Logan: Utah State University.

6. Boscardin, M. D., E. T. Selig, R. S. Lin, and G. R. Yang. January 1990. Hyperbolic

Parameters for Compacted Soils. ASCE Journal of Geotechnical Engineering 116(1).

7. Burns, J. Q. and R. M. Richard. 1964. Attenuation of Stresses for Buried Cylinders.

In Proceeding of the Symposium on Soil Structure Interaction, pp. 378–392. Tucson:

University of Arizona.

8. Concrete Pipe Division of U.S. Pipe and Foundary Company. Bulletin No. 200.

Birmingham, Ala.

9. Devine, Miles. 1980. Course Notebook. Logan: Utah State University.

10. Ductile Iron Pipe Research Association. 1984. Thrust Restraint Design for Ductile

Iron Pipe.Birmingham, Ala.

11. Duncan, J. M., P. Byne, K. S. Wong, and P. Mabry. 1980. Strength, Stress-Strain and

Bulk Modulus P

arameters for Finite Element Analyses of Stresses and Movements in

Soil Masses. Department of Civil Engineering Report UCB/GT/80-0. University of

California, Berkeley.

12. Dunn, I. S., L. R. Anderson, and F. W. Kiefer. 1980. Fundamentals of Geotechnical

Analysis. New York: Wiley.

13. Federal Aviation Authority (FAA). Aircraft Pavement Design and Evaluation. AC

150/5320-6C.

14. Federal Aviation Authority (FAA). Aircraft Data. AC 150/5325-5C.

15. Howard, Amster K. 1977. Modulus of Soil Reaction (E’) Values for Buried Flexible

Pipe. Journal of the Geotechnical Engineering Division, ASCE 103(GT). Proceedings

Paper 127000.

16. Janbu, N. 1963. Soil Compressibility as Determined by Odometer and Triaxial Tests.

In Proceedings of European Conference on Soil Mechanics and Foundation Engi-

neering, pp. 19–25. Wissbaden, Germany: Soil Mechanics Foundation.

17. Katona, M. G., J. B. Forrest, F. J. Odello, and J. R. Allgood. 1976. CANDE—A

Modern Approach for the Structural Design and Analysis of Buried Culverts. Report

FHWA-RD-77-5. U.S. Department of Transportation.

18. Katona, M. G., P. D. Vittes, C. H. Lee, and H. T. Ho. 1981. CANDE-1980: Box

Culverts and Soil Models. Springfield, Va.: National Technical Information Service.

19. Konder, R. L., and J. S. Zelasko. 1963. A Hyperbolic Stress-Strain Formulation of

Sands. In Proceedings of the Second Pan American Conference on Soil Mechanics

and Foundation Engineering 1:209.

20. Krizek, R. J., R. A. Parmelee, N. J. Kay, and H. A. Elnaggar. 1971. Structural Analysis

and Design of Buried Culverts. National Cooperative Highway Research Program

Report 116. Washington: National Research Council.

21. Kulhawy, F. H., J. M. Duncan, and H. B. Seed. 1969. Finite Element Analysis of

Stresses and Movements in Embankments during Construction. Report TE-69-4.

Berkeley: Office of Research Services, University of California.

22. Marston, A. 1930. The Theory of External Loads on Closed Conduits in the Light

of the Latest Experiments. Bulletin 96. Ames: Iowa Engineering Experiment

Station.

23. Moser, A. P. 1990. Buried Pipe Design, 1st ed. New York: McGraw-Hill.

24. Moser, A. P. 1983. Course Notebook. Logan: Utah State University.

25. Nyby, D. W. 1981. Finite Element Analysis of Soil Sheet Pipe Interaction. Ph.D. dis-

sertation. Logan, Utah: Department of Civil and Environmental Engineering, Utah

State University.

26. Ozawa, Y., and J. M. Duncan. 1973. ISBILD: A Computer Program for Analysis of

Static Stresses and Movements in Embankments. Report No. TE-73-4. Berkeley:

Office of Research Services, University of California.

27. Paris, J. M. November 10, 1921. Stress Coefficients for Large Horizontal Pipes. Engi-

neering News Record 87(19).

28. Piping Systems Institute. 1980. Course Notebook. Logan: Utah State University.

29. Spangler, M. G. 1950. Field Measurements of the Settlement Ratios of Various High-

way Culverts. Bulletin 170. Iowa State College.

386 Chapter Six

30. Spangler, M. G. 1933. The Supporting Strength of Rigid Pipe Culverts. Bulletin 112.

Ames: Iowa State College.

31. Spangler, M. G., and R. L. Handy. 1973. Soil Engineering, 4th ed. New York: Harper

& Row.

32. Spangler, M. G., and W. J. Schlick. 1953. Negative Projecting Conduits. Report 14.

Ames: Iowa State College.

33. Steel Plate Fabricators Association, Inc. 1970. Welded Steel Water Pipe Manual. Des

Plaines, Ill. p. 24.

34. The Asphalt Institute. March 1978. Soils Manual for the Design of Asphalt Pave-

ment Structures. Manual Series No. 10 (MS-10). College Park, Md.

35. Timoshenko, S. P. 1961. Theory of Elastic Stability, 2d ed. New York: McGraw-Hill.

36. Timoshenko, S. 1956. Strength of Materials, Part 11, 3d ed. New York: D. Van

Nostrand.

37. Watkins, R. K., and M. G. Spangler. 1958. Some Characteristics of the Modulus of

Passive Resistance of Soil: A Study in Similitude. In Highway Research Board Pro-

ceedings 37:576–583.

38. W

ong, K. S., and J. M. Duncan. 1974. Hyperbolic Stress-Strain Parameters for Non-

linear Finite Element Analysis of Stresses and Movements in Soil Masses. Report

TE-74-3. Berkeley: Office of Research Services, University of California.

39. Zienkiewitcz, O. C. 1977. The Finite Element Method 3rd ed. New York: McGraw-

Hill.

387

Plastic

Flexible Pipe

Products

Thermoplastic Pipe Materials

There are several types of thermoplastics that are used in the manu-

facture of pipe. A brief discussion of thermoplastics and design bases

are contained in Chap. 4. There are four principal thermoplastics used

to make pipe: polyvinyl chloride (PVC), acrylonitrile-butadiene-

styrene (ABS), polyethylene (PE), and polybutylene (PB). Pipes made

from other thermoplastics command an extremely small market and

are primarily used for specialty applications, such as styrene rubber

(SR) and cellulose-acetate-butyrate (CAB).

Polyvinyl chloride

PVC pipe is available for both pressure and gravity applications

(Fig. 7.1). For gravity sewer applications, it is available in both solid-

wall and profile-wall varieties. Size ranges are as follows:

PVC pressure pipe:



to 36 in

PVC solid-wall gravity pipe: 2 to 27 in

PVC profile-wall sewer pipe: 4 to 48 in

The above listed sizes are generally available. However, sizes outside

the listed ranges may be available on special order from the manufac-

turer.

Chapter

Polyvinyl chloride is manufactured from ethylene and chlorine.

Ethylene is extracted from natural gas or crude oil, usually from natural

gas. It is also possible to use coal; however, that process is much more

expensive. Chlorine is manufactured via electrolysis from salt-water.

Vinyl chloride monomer is produced by oxychlorination (a reaction of eth-

ylene with chlorine). The vinyl chloride monomer (VCM) is polymerized to

make polyvinyl chloride resin. PVC resin is a white, powdery substance

having the consistency of table sugar.

This PVC resin is the basic “building block” for PVC pipe. To opti-

mize processabilty and performance properties, the pipe manufac-

turer takes PVC resin and compounds it with lubricants, stabilizers,

fillers, and pigments. After the mixing takes place at an elevated

temperature, the mixture is allowed to cool to ambient temperature.

This PVC compound is fed to a PVC pipe extruder (Fig. 7.2). The

extruders are usually of multiscrew design. The PVC compound is

388 Chapter Seven

Figure 7.1 PVC’s high strength-to-weight ratio is a real advan-

tage. (Reprinted by courtesy of Uni-Bell PVC Pipe Association.)