The engineering design and laboratoryanalysis of a sand sampler for horizontal pipes

Item Type text; Thesis-Reproduction (electronic)

Authors Anderson, Carl Elmer, 1940-

Publisher The University of Arizona.

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THE ENGINEERING DESIGN AND LABORATORY ANALYSIS OF A SAND SAMPLER FOR HORIZONTAL PIPES

byCarl E, Anderson

A Thesis Submitted to the Faculty of theDEPARTMENT OF AGRICULTURAL ENGINEERING

In Partial Fulfillment of the Requirements . For the Degree ofMASTER OF SCIENCE

In the Graduate CollegeTHE UNIVERSITY OF ARIZONA

1 9 6 5

STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfillment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author.

SIGNED:

APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below:

HAROLD C. SCHWALEN DateProfessor of Agricultural Engineering

PREFACE

This thesis is part of a continuing study of the effect of length of service and changing operating conditions‘upon the field efficiency of deep well turbine pumping plants sponsored by the James Go Boswell Foundation Grant to the Arizona Agricultural Experiment Stationo During the first phase of this work it was found that the major cause of pump wear and loss of efficiency was the erosive action of sand particles in the pumped water,/ A quantitative and qualitative determination of the total sand pumped was needed in order that a direct correlation could be made with changing efficiency. No satis­factory method of obtaining a representative sample of the sand pumped over a long period of operation was found. This study was therefore undertaken for the purpose of developing and testing a sand sampler for field pumping plants.

The author would like to acknowledge the advice and guidance of Professor Harold C, Schwaten of the Agricultural Engineering Depart­ment , His many ideas and helpful criticism in the planning and writing of this thesis were much needed and appreciated.

The author would also like to thank Mr, W, G, Matlock of the Agricultural Engineering Department for the many hours he spent guiding and helping with the research for this thesis, and the several other members of the department who helped with ideas and work time in building equipment.

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TABLE OF CONTENTS

PageLIST OF ILLUSTRATIONS0 . . . . . . . . . . . . . . . . . . . . . . . viLIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . ixABSTRACT . . . . . ........ . . . . . . . . . . . . . . . . . . . . xINTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

General Discussion. . . . . . . . . . . . . . . . . . . . . . . 1Statement of the Problem. . . . . . . . . . . . . . . . . . o . 2Review of Literature. . . . . . . . . . . . . . . . . . . . . . 3Summary of Literature Review. . . . . . . . . . . . . . . . . . 8

SAMPLER DESION . . . . . . . . . . . . . . . . . . . . . . . e . . . 9Design Considerations . . . . . . . . . . . . . . . . . . . . . 9Details of Sampler. . . . . . . . . . . . . . . . . . . . . . . II

TESTING EQUIPMENT . . . . . . . . . . . . o . . . . . . . . . . . . . 15Laboratory Requirements . . . . . . . . . . . . . . . . . . . . 15Laboratory Size .. . . . . . . . . .. . * . . . . # . . . . . 15Pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Tank Construction . . . . . . . . . . . . . . . . . . . . . . . 16Flow Metering and Regulating Facilities . . . . . . . . . . . . 1 8P i p l u g 18 Sand Injector . . . . . . . . . . . . . . . . . . . . . . . . . 18Sand Mixtures . . . . . . . . . . . . . ........ . . . . . . . 22Sample Recovery Equipment . . . . . . . . . . . . . . . . . . . 2 2

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V

TABLE OF CONTENTS--Continued

PageEXPERIMENTAL PROCEDURE, . . . . . . . . . . . . . . . . . . . . . . 27

Preparation of the Sand Mixture« 27Adjustment of Sampler Position » ........ • « • . . . . . • • 29Preparation of Settling Tanks, 32Test Procedure . . . . . . . . . . . . . . . . . . . . o . . . 32

RESULTS AND DISCUSSION, 36Particle Size Distribution . . . . . . . . . . . . . . . . . . 36Sand Concentration . . . . . . . . . . . . . . . . . . . . . . 45Location for Best Sampling . . . . . . . . . . . . . . . . . . 49Analysis of Errors . . . . . . . . . . . . . . . . . . . . . . . 51

CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54SUGGESTIONS FOR FURTHER STUDY . . . . . . . . . . . . . . . . . . . 56SELECTED BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . 57

LIST OF ILLUSTRATIONS

Figure1, Volume of material discharged versus position in

four-inch pipe - Sand„2e Sampler tube with packing gland and a short section

of pipe showing method of installing tube and sampler hose,

3. Sampler hose with regulating clamp discharging into settling tank.

4. Single stage, end suction centrifugal pump and 10 horsepower motor.

5. Piping arrangement showing flowmeter, gate valve and section simulating a vertical pump column, discharge elbow and horizontal discharge pipe.

6. Sand injector mounted in vertical section of pipe showing motor and belt drive mechanism.

7. Motor-driven portable sieve shaker with nest of sieves, automatic timer and sand fraction collection cans.

8. Plastic lined settling tanks and hoses from samplers discharging into spreading cans.

9. Small pump and motor used to return flow from settling tanks to supply tank.

10. Diagram of laboratory layout.11. Diagram showing sampled positions in flow cross-section.12. Location of sampled points with relation to the dis­

charge elbow.13. Rinsing plastic liner to recover sand samples on 200

mesh cloth, .14. Particle size distribution of samples and injected

hand washed sand for a test 14 inches from the elbow. Velocity 7.5 feet per second and sand concentration49.5 parts per million.

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12

14

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19

21

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263031

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viiFigure15o Particle size distribution of samples and injected

machine washed sand for a test 14 inches from the elbow. Velocity 7,5 feet per second and sand concentration 35,7 parts per million,

16. Particle size distribution of samples and injected reused sand for a test 14 inches from the elbow.Velocity 7,4 feet per second and sand concentration21.0 parts per million.

17. Particle size distribution of samples and injectedsand for a test 14 inches from the elbow. Velocity7.5 feet per second and sand concentration 9.8 parts per million.

18. Particle size distribution of samples and injectedsand for a test 14 inches from the elbow. Velocity4.9 feet per second and sand concentration of 72.5 parts per million.

19. Particle size distribution of samples and injectedsand for a test 14 inches from the elbow. Velocity4.9 feet per second and sand concentration 18.2 parts per million.

20. Particle size distribution of samples and injectedsand for a test 26 inches from the elbow. Velocity7.0 feet per second and sand concentration 37.2 parts per million.

21. Particle size distribution of samples and injectedsand for a test 38 inches from the elbow. Velocity7.4 feet per second and sand concentration 40.8 parts per million.

22. Particle size distribution of samples and injectedsand for a test 38 inches from the elbow. Velocity4.9 feet per second and sand concentration 55.1 parts per million.

23. Particle size distribution of samples and injected sandfor a test 62 inches from the elbow. Velocity 7.4 feetper second and sand concentration 37.3 parts per million.

24. Particle size distribution of samples and injected sandfor a test 62 inches from the elbow. Velocity 5.0 feetper second and sand concentration 48,1 parts per million.

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38

38

40

40

41

42

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44

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Figure25 o Percent of total weight caught at individual sampling

points in tests at 14, 38, and 62 inches from the discharge elbow in a water velocity of 7»4 feet per second and a sand concentration of 38.5 parts per million.

26. Percent of total weight caught at individual sampling points in tests at 14, 38, and 62 inches from the discharge elbow in a water velocity of 4.9 feet per second and a sand concentration of 57.6 parts per million.

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47

LIST OF TABLES

Percentage by Which Sampler Weights Caught 14 Inches From the Elbow Deviated From the Weight Needed to be Representative of the Sand Concen­tration.Data for Samples Caught 14 Inches From the Elbow in the Center of the Pipe.A Comparison of the Measured Sand Distribution and the Corrected Distribution for a Typical Injected Mixture.

ABSTRACT

Wear on pumping equipment has been traced in part to the sand content of the pumped water. The purposes of this study were to design a sand sampler that could be installed and operated under field con­ditions for accurately sampling the pumped water, and to conduct labo­ratory tests of the sampler,

A sampler was designed similar to a pitot tube and inserted through a hole drilled into the discharge pipe. Flow through the sampler was regulated to obtain approximately one percent of the pump discharge.

Laboratory tests were conducted in 6,25-inch pipe with flow velocities from 4,9 to 7,5 feet per second, sand concentrations from 10 to 70 parts per million and various known particle Size distributions. Tests were conducted at distances of 14, 26, 38 and 62 inches from a simulated pump discharge elbow with seven sampled points on the vertical diameter of the pipe.

Only samples collected 14 Inches from the elbow were repre­sentative of both the particle size distribution of the injected sand and the sand concentration in the pumped water. The most representative samples were found 1 7/8 inches from the inside top of the pipe 14 inches from the elbow. The range of flow velocities used only affected the results for sampled positions more than 14 inches from the elbow. The sand concentration in the range used did not affect the results.

The use of a low number of velocities and only one pipe diameter did not permit extension of the results.

INTRODUCTION

General Discussion:

Water is necessary for maintaining any civilisation and is essential to profitable agriculture* Two-thirds of Arizona’s irri­gation water is pumped from underground sources* The water supply for Tucson comes entirely from ground water* As water usage in Arizona has increased in recent years, the water table has steadily been lowered and well capacities decreased* This has caused an increase in pumping costs through two factors, the first obviously being the increased lift necessary to get the water to ground level* The second factor has been the excessive wear on the pump machinery caused by increased pumping of sand from increased drawdown in an effort to maintain well capacities*

Pump efficiency is a major concern to the pump owner* In Pinal County, Arizona in 1951 (7) average figures showed that a decrease in efficiency for electrically powered pumping plants from 46 to 39 percent increased pumping costs by about 16 percent, and an increase in ef­ficiency from 46 to 54 percent decreased costs by about 19 percent* Repair costs were exceeded only by power costs in operating a deep well pumping plant* Most of the repair expense was for overhauling the pump bowls, and was as high as $2277 for one pump in a single pumping season*

The wear on pumping equipment which causes these high costs in repairs and losses in pumping efficiency has been traced in part to the

1

sand content o£ the punq>ed water. Therefore a method of making quanti­tative as well as qualitative studies of this sand is of interest to pump owners and operators.

Statement of the Problem:

In the study of the effect of sand on the operation of a field pumping plant the investigator would be interested in answering a number of questionss:

1, How much sand is being removed from an area by the pumping plant over an extended period of time?

2, What is the normal particle sise distribution of sediments coming from the pumped well?

3, What effect does the particle shape and mineral composition have on the wearing characteristics of the sand?

To answer these questions a method is needed to obtain a sample of the sand being pumped which will accurately represent the quantity, size distribution, and character of this sand.

The purpose of this study was to design a device which could be easily installed and operated in remote locations for sampling the flow in the horizontal discharge pipe of pumping plants to obtain an accurate sample of the sand content of that flow, and to conduct laboratory tests to determine the performance characteristics of the device. The resulting device was designed to operate under conditions existing in the majority of field installations.

- One such device was designed and tested with one size Of discharge pipe0 Velocities and sand concentrations used in the testing were those which could reasonably be expected to occur in field pumping plants. Ho field tests were included in the study.

Review of Literature and Previous Works

A review of available literature showed that little has been published on sampling sediments in pipes, Matlock (5) compared field . pump performance with laboratory performance. Comprehensive pump tests were made on field pumping plants and corrected for all losses to obtain the efficiency of the pump alone. In comparing the field data with laboratory data* samples of the sand content of the pumped water for each well were obtained by holding a pint container at the end of the discharge pipe. Samples, taken at intervals after the first flow reached the end of the discharge pipe, provided only a rough estimate of the sand content of the pumped water, but did show that pumps discharging the largest quantity of sand experienced the greatest loss in efficiency, Matlock concluded that sand was the greatest cause of pump wear in the pumps he tested, and that a better method of measuring the sand content of the pumped water was needed. In later work (6) a sand sampler which consisted of three 1/2-inch pipes Inserted into the open end of the pump discharge was field tested. The samples were caught in 5-gallon settling buckets and analyzed. These field tests were made on a very limited scale, and the sampler was not laboratory tested or calibrated,

Durand (3) investigated the use of pipelines for transportation of mine or quarry products in France, He discovered that particles less

than 50 microns in size always remained in suspension, those between 50 microns and 0.2 millimeters followed the turbulent fluctuations and thus moved throughout the entire flow, and those greater than 2.0 millimeters moved only by successive jumps on the bottom of the pipe. He defined a limit velocity as the velocity below which deposits occurred on the bottom of the pipe. He found this to be directly proportional to the one-half power of the pipe diameter. The value of the limit velocity in­creased as grain size increased between 0.05 mm and 1.0 mma and also as concentration increased up to 4 percent by volume. For particles larger than 1.0 mm the concentration and grain diameter had no particular influ­ence on the limit velocity. Durand found the values of the limit ve­locity for solids exceeding 1.0 mm in diameter to be 9.66 feet per second for 150 mm diameter pipe and 12.29 feet per second for 250 tm pipe. The friction losses and velocity distribution approached those for clear water as the concentration approached 2 percent, the lowest concentration used in his tests.

Howard (4) conducted experiments on the transportation of sand and gravel in 4-inch pipe. Tests were conducted with a sand mixture and a pea-gravel mixture. During each test series the pipeline velocity was varied from 5.5 feet per second to 13.0 feet per second and the sand concentrations were varied from 10 to 40 percent.

Sand concentrations over the pipe cross-section were determined by inserting an L-shaped tube, 7/16-inch in diameter, into the end of the pipe. The sample tube was mounted so that it could be moved to any location in the pipe cross-section. Sand concentrations were determined

by using a calibrated basin mounted on scalese The point of sampling #as 86.25 diameters from the nearest elbow along a horizontal pipe.

Howard found that for velocities below 6 feet per second most sand moved on the bottom, and above 7.5 feet per second the sand m s carried in suspension. However, this varied somewhat for different solid concentrations.

Figure 1 is a curve by Howard showing the relationship between the quantity of material discharged and vertical position in the pipe for a water velocity of 8.88 feet per second and a sand concentration of 14.4 percent. From this he concluded that the largest quantity of material is transported in the lower one"third of the pipe rather than along the bottom. The greatest concentration of solids occurs on the bottom of the pipe, but the velocity is lower, and thus reduces the actual amount of material carried in this area.

Yamell and Nagler (12) investigated the flow of water around bends in pipes. As part of their work tests were made on a standard 6-inch elbow with a 5.25-inch inner radius. The approach and discharge tangents were each 25 feet long. Velocity and pressure measurements were made at nine different sections on both the approach and discharge pipes, and at22.5 degree intervals on the bend.

The position of maximum velocity moved from the inside to the outside as the water traveled around the bend. The greatest velocity was found next to the inside wall, midway around the elbow. The velocity distribution in the pipe did not approach normal until the flow was more than five feet beyond the elbow. These conditions were altered slightly when the velocity distribution in the approach pipe was other than uniform.

DISTANCE FRO

M TOP OF

PIPE

IN INCHES

6

100 15050 200 2500SAND DISCHARGE (in3/see)

Figure !<, Volume of material discharged versus position in four-inch pipe - Sand. After Howardg Transactions, Am. Soc. Civ. Engineers. 1939.

Rossum (8) reported on the control of sand in water distribution systems supplied by wells. He found samples taken immediately downstream from fittings which create turbulence such as elbows are generally satis­factory if water velocities are at least five feet per second0 Rossum also stated that a sampler must operate over a substantial period of time with Infrequent attention to obtain a sample representative of the natural variation in sand concentratione

Winn (11) explained that Equipment Engineers Incorporated Invest!-\

gated sand sampling procedures in the design of their Krebs Centrifugal Sand Separatorse He disclosed that their work had confirmed the con- . elusions reached by Rossum concerning the sampling pointg velocity* etCo He also stated that settling methods were the most satisfactory for sepa­rating sand from water in the sample and that approximately one-quarter pound of sand was necessary for accurate mechanical analysis» Minn indicated that they tested wells which had sand concentrations ranging from 0.8 to 35,0 parts per million. Particles larger than 74 microns were usually considered to be harmful to hydraulic machinery,

Anderson (1) discussed a sampler design for suspended load in streams which used a tube pointed upstream to collect a sample. Because of energy losses and backpressure the velocity within the tube was normally less than the velocity of the stream being sampled. Thus the cross-sectional area of the filament of water being sampled was less than the area of the sampler tube. As the filament approached the tube open­ing its area gradually expanded to equal the tube area with a corre­sponding reduction in velocity. The inertia of the sediment particles just outside the filament tended to keep them moving in a straight line

and Into the tube opening. Thus the sand concentration in the sample m s increased slightly. Also since the inertial force on the particle m s dependent on mass a higher concentration of larger particles resulted. Tests were conducted to determine a correction factor to use in computing the actual concentration of the sampled stream.

Summary of Literature Review;

The work done by Matlock (5»6) showed the need for a sand sampler for deep well pumping plants, Durand (3) and Howard (4) described the flow of sand through horizontal pipes of sufficient straight length for the sand travel to have reached some degree of equilibrium, Howard de­scribed briefly a method of sampling the flow for sediment content,

Yarnell and Hagler'a (12) work indicated the velocity pattern to be expected near an elbow. Since Howard' s work demonstrated that the total quantify of sand passing any given point is dependent both on the concentration and the velocity at that points, a combination of these re* suits shows where the most sand might be found just downstream from an elbow, .

Rossum (8) indicated several requisites for obtaining repre­sentative samples from horizontal pipes, Winn (11) suggested the minimum sample size for analysis* methods of separating the sand from water in the samples and a range of sand concentrations to expect in the field, Anderson (I) discussed the problems caused by the sampler tube velocity being different from that of the stream for a suspended load sampler.

SAMPLER DESIGN

Design Considerations,; ,

Several basic requirements have to be met by any design to make a useful tool for field investigations0 The sampler should;

1« Be easily installed on typical field pumping plants02. Sample at a point where sand is uniformly distributed.3. Be useable in pipe sizes and with water velocities commonly

found in field installations«4. Disturb the stream being sampled as little as possible at

the point of sampling.5. Be portable and require no external power.6. Operate over extended periods of time with infrequent

attention.In the design of a sand sampler several methods of sampling were

considered. One was to pass the flow from the discharge pipe through a flume and sample with a traversing sampler similar to those used in sampling concentrates in milling ores. This requires an open discharge near the pump and equipment difficult to install in the field, and is thus unable to fulfill requirement number 1 above.

A second method considered was for a sampling device which could be inserted from the open end of the discharge pipe so that the point of sampling would be near the discharge elbow. This method was used in the sampler field tested by Matlock (6)„ and obtained several samples at once.

9

10however9 it was dependent on a relatively short discharge pipe with an open end which also did not meet requirement number 1 above.

The third method considered was a sampling device which could be inserted into the discharge pipe through a hole drilled and tapped near the pump. This method was independent of the discharge pipe arrangement on the pumping plant and could fulfill requirements 1, 23 and 3 above. This method was selected as the most desirable of those considered be­cause features could be included to make it fulfill all the basic re­quirements.

Of the possible designs for a sampler using a hole in the dis­charge pipe the simplest was to fasten a hose to a fitting in the hole flush with the wall of the pipe. This method is employed in the Rossum sand tester (8), but allows samples to be taken only from the outer edges of the flow9 and disturbs the natural conditions by taking a sample at right angles to the mean direction of motion of the stream, thus failing to satisfy requirement number 4 above,

A second design was the use of a slotted tube extended across the discharge pipe to intercept a sample from a finite strip of the flow.This tube would cause a disturbance because it would be perpendicular to the flow at the point of sampling and thus did not satisfy requirement number 4,

A third design was a tube similar to a simple pitot tube which could extend upstream from the point of entry, thus minimizing the dis­turbance at the point of sampling. This sampler could sample only one point at a time, but that point could be located exactly. This design

11was used for the sampler because it would fulfill all the basic requirements.

Details of Sampler:

The tube size chosen for the sampler was one which could be passed through a reasonably small hole, and which had a cross-sectional area of approximately one percent of the pipe area which was also the desired percentage of total flow for a sample. One-half inch electrical conduit was chosen because it was a strong, thin walled tubing which could be easily obtained. The sampler used for these tests was con­structed with a 9-inch vertical section, and a 4-inch horizontal section, and was made by cutting a 90-degree notch from a length of the conduit, and bending and soldering the conduit to form a rigid elbow at the correct point (Figure 2). The dimensions of this elbow allowed it to pass through a hole drilled and tapped for 3/4-inch pipe fittings. A packing gland, made from 3/4-inch pipe fittings held the tube.rigidly in place and formed a water-tight seal around the sampler tube when tightened.

The flow rates through the sampler were adjusted to produce velocities equal to the mean velocity in the discharge pipe. In this way the velocity in the sampler would be approximately equal to the velocity at the point of sampling and would disturb the natural conditions in the flow the least. A vinyl hose was attached to the outlet of the tube with its discharge lower than the sampled point in the pipe to produce suf­ficient head to overcome any friction losses within the sampler tube and

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Figure 2. Sampler tube with packing gland and a short section of pipe showing method of installing tube and sampler hose.

13hose0 The flow rate through the sampler was regulated by means of a pinch clamp on this hose (Figure 3)„

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Figure 3. Sampler hose with regulating clamp discharging into settling tank.

TESTING EQUIPMENT

Laboratory Requirementst

A laboratory for testing a sand sampler required the following:la A pump which would operate at low discharge heads«2. A source of sand-free water„3. Flow regulating and metering facilitiese4. A system of piping to simulate a field pumping plant»50 A method for injecting sand at known rates®6® Equipment for preparing sand mixtures of known size

distribution®7® Equipment for recovering the sample after collection®

Laboratory Size: ■ '

Discharge pipe sizes commonly found on field pumping plants range from 4 to 12 inches in diameter, and water velocities in these pipes mayrange from 4 to 10 feet per second. Below 5 feet per second the coarsesand in the flow is generally found on the bottom of the pipe, and above 8 feet per second it is always found in suspension (4), therefore, flow velocities in this range were desirable for testing.

Because a clear water source of sufficient quantity was una­vailable, a circulating hydraulic system was designed, A large tank was constructed to serve as a source of water and a settling tank to remove sand from the flow. The study was limited by available space and funds

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to the construction of a supply tank 4-feet by 4-feet in cross-section by 27-feet in length.

The smallest sand particles of interest were those which would be retained on a 200 mesh sieve. Using Stoke’s Law9 computations showed that these would settle about one foot in 55 seconds, or 3,5 feet in 190 seconds. These particles would settle to this depth in a tank with an effective settling length of 24 feet if the flow was 790 gallons per. minute or less, A 6-inch pipe would produce a pipeline velocity of 8 feet per second with a discharge of 705 gallons per minute,

Bump:

Only enough hydraulic head was needed in the laboratory to overm come losses in the pipe system and lift the water to the top of the supply tank, a distance of about five feet, A Universal, single stage, end suction centrifugal pump was used (Figure 4), When operated at 1540 revolutions per minute this pump could deliver 715 gallons per minute at approximately 10 feet of head.

Tank Constructions

The dimensions of the tank as given permitted a minimum flow cross-section of 4-feet by 3,5-feet with a settling basin 24 feet in length, A short entrance section and a sump for the pump suction utilised the remaining 3 feet of the tank. Baffling was included at the entrance to minimize turbulence and a low weir was installed in the sump to reduce velocities near the bottom. The tank was constructed with a wooden frame covered with plywood and lined with 24-gauge sheet metal.

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Figure 4. Single stage, end suction centrifugal pump and 10 horsepower motor.

18Flow Metering and Regulating Facilities:

To conduct tests under varying conditions a means of regulating and measuring the water flow was required, A gate valve was installed in the pipeline, and a Sparling flowmeter was used to measure discharge. Sparling meters are guaranteed to be accurate to within 2 percent for all flows above the minimum specified flow rate. The 6-inch meter used was recommended for a flow range from 100 to 900 gallons per minute.

Piping; '

Pipe with an inside diameter of 6,25 inches was used for all piping in the laboratory to produce a pipeline velocity of about eight feet per second with the maximum discharge used. The pipe arrangement (Figure 5) was made to simulate the vertical pump column and the hori­zontal discharge of a field pumping plant. The pipe discharged into an open flume for return to the tank, allowing access to the open end of the pipe.

Sand Injector;

Sand concentrations from 1 to 100 parts per million were con­sidered to be important in the study. Therefore any device for injecting sand had to be capable of operating at nearly one hundred times its slowest speed. The sampler was to operate at a point where the sand con­tent of the flow was uniformly distributed over the pipe cross-section.To achieve this an injector was designed which would mechanically inject a wet sand mixture into the pipe just below the elbow to the horizontal

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Figure 5. Piping arrangement showing flowmeter, gate valve and section simulating a vertical pump column, discharge elbow and horizontal discharge pipe.

20discharge section,, taking advantage of increased turbulence to distribute the sando

The first injector tried consisted of a V»shaped sand hopper with a 9/16-inch auger for the injecting mechanism,, The auger was located at the bottom of the hopper in a length of 1/2-inch electrical conduit open at the top to allow the sand to flow onto the auger« The end of the conduit protruded into the pipe through a gland like that used for the sampler tube. The auger was driven by a system of V-beIts and inter­changeable pulleys to provide various speeds. The water in the pipe at the point of sand injection was under pressure8 and could move into the hopper. Since either dry or saturated sand would flow, but moist sand tended to bridge, the injector was located to allow the sand in the hopper to be saturated.

This initial model was installed and used in tests with the sampler. From these tests it was noted that the sample caught was con­sistently made up of more fine particles than had been in the injected sand mixture. Therefore a test was run in which sand of only one size, that passing a number 16 sieve and caught on a number 30 sieve, was in­jected. When a sample was caught and analyzed, 30 percent of the sample passed the number 30 sieve. It was concluded that the auger was grinding the sand, and was thus unusable.

A second injector model was built using the same hopper arrange­ment with a continuous roller chain moving across the bottom to drag the sand into the pipe (Figure 6). The chain moved around the circuit inside 1/2-inch electrical conduit except for a small section at the top where it traveled across a drive sprocket. The sprocket was in turn driven by

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Figure 6. Sand injector mounted in vertical section of pipe showing motor and belt drive mechanism.

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a variable speed V-belt system similar to that used with the augere The chain speed could be regulated from 4 feet per minute to less than 1/2-inch per minute. This model proved satisfactory and was used in the testing.

Sand Mixtures:

River sand was used as the sediment in the water because this closely conformed to that which might be pumped from wells. This sand had to be first divided into its various size fractions., and then recom­bined in known mixtures for injection. This was accomplished by dry sieving all the sand using Tyler Sieves and a Tyler Portable Sieve Shaker (Figure 7), U, S, Standard sieve sizes of 8, 16, 30, 50, 100, and 200 were used for all tests.

Sample Recovery Equipment:

Settling was considered to be the best method for recovering the sand from the water in the sample. Aluminum boxes were available 7-feet long by 1 1/2-feet wide by 9-inches deep. These would have a detention time of more than seven minutes for the highest sampler discharge rate tested, and would allow time for the smallest particles to settle out.The tanks were lined with sheets of plastic to facilitate the recovery of small quantities and small size particles from the bottom (Figure 8).

To minimize turbulence in the sample settling tank the sample stream was passed through a spreading can made by perforating a gallon can with holes just large enough to pass the largest sand particles. This

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Figure 7. Motor-driven portable sieve shaker with nest of sieves, automatic timer and sand fraction collection cans.

Figure 8. Plastic lined settling tanks and hosesfrom samplers discharging into spreadingcans.

24can was suspended at one end of the settling tank with its base under water but not resting on the bottom0

Three samplers and settling tanks were used in the laboratory simultaneously so that more information could be obtained from each test run* At the maximum flow rate the three samplers could empty the large tank in a few hours0 To avoid this a water return system was installed for the sampler tanks (Figure 9), The tanks were joined by 2-inch pipe0 and a small pump was installed to pump water back into the supply tank at a rate regulated by a 1-inch gate valve* This pump was also used to completely drain the sample tanks at the end of a test.

The laboratory equipment was arranged as shown in Figure 10,

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Figure 9. Small pump and motor used to return flow from settling tanks to supply tank.

27'

Baffles

SUPPLY TAIIKSmall Return Flow Pump and Motor

Sand Injector

Gate Valve

Return FlumeFlow Meter

^ Spreading Cans Pump and Motor _^ -Sample Settling Tanks

Figure 10. Diagram of Laboratory Layout.

EXPERIMENTAL PROCEDURE

Preparation of the Sand Mixture:

The first source of sand used was from the Rillito Creek bed at the University of Arizona River Road Farm, A screen was used to remove large particles from the sand, producing an upper size limit for this sand which was between the number 8 and number 16 sieve sizes. Unwashed river sand was undesirable because a long period of shaking was required to separate the silt and clay from the sand. Also unsepa­rated silt and clay caused errors in the weight of any size fraction being injected. The fine particles also caused the sand to clog in the Injector, hopper. Hand washing of this sand was tried, but was too time consuming to be of practical use.

The second source of sand was from the finest sizes produced by local sand companies. This also was river sand which had been washed and screened. Because this sand was usually wet it was dried on a forge and then sieved. Although better than unwashed river sand, this sand was not as good for testing as the hand washed sand because it still contained enough clay to cause some of the fine particles to stick together and not pass through the screens. However, most of the sand used in the first part of the testing was from this source.

A third source of sand, and one which proved very useful during later portions of the testing program, was that which had been passed

27

28through the laboratory once and was reclaimed from the bottom of the supply tank0 This sand had received intensive washing when it passed through the discharge pipe in lot# concentrations

The sand from any of the three sources was first dry screened to separate it into size fractions. The sand used for testing was that which could pass a number 8 sieve and would be caught on the remaining sieves up to number 200s The time of sieving was determined as that time necessary to shake one screen pan full of sand so that further shaking would not change the resultant sample passing any one sieve by more than 5 percent. This time for air dry sand was found to be about 25 minutese After the sand had been separated into the five fractions it was stored in Covered metal bins.

To accurately make a mechanical analysis of a sand sample: it must■;v

weigh approximately one quarter pound (11). Because the samplers were taking approximately one percent of the total flow, 25 pounds of sand would have to be injected for each sample to be large enough. To insure a sufficient sample 30 pounds of sand were injected for each run.

The size mixtures used for the injected sand were determined by the amount of the various size fractions available, so that no one size fraction would be used up before any other. This procedure was followed somewhat loosely because various size mixtures were desired, and even percentages were used to calculate mixing values.

Using the above means the required weights were calculated to make a 30 pound mixture. Each size fraction was weighed separately on a scale to the nearest one-tenth gram. The fractions were then mixed thoroughly and poured into the dry injector hopper. The sand was leveled off and

29the depth from the top of the hopper to the sand measured and recorded* If the run had to be stopped for some reason before all the sand in the hopper had been injected, the amount of sand needed to refill the hopper to the recorded depth would be a measure of the sand injected*

Adjustment of Sampler Position;

The position of the samplers in the discharge pipe was adjusted by loosening the nut on the packing gland and moving the sampler to the desired location using the scale marked on the side of the sampler tube* The alignment of the sampler tube with the flow was adjusted by aligning a mark on the tube with the discharge pipe centerline* The packing nut was then tightened and the fine alignment of the tube made by looking up the end of the pipe and aligning the horizontal section of the tube with the pipe*

The sampler positions used were chosen so that one test of seven points across the pipe could be sampled in three runs with the velocity, sand concentration and distance from the elbow constant*Figure 11 represents the points sampled* The sampler which entered the pipe vertically from the top sampled the three points at the top* The sampler which entered the pipe vertically from the bottom sampled the bottom three points* The sampler which entered the pipe horizontally from the side sampled only the center point. Each test included one sample from each of the outer six points and three samples from the center point.

A series of these tests was repeated for distances of 14, 38, and 62 inches from the inside corner of the elbow (Figure 12). One run

30

Position 1

osition 2

Position 3

osition 4

Posit ion 6W^ ^Position 7

Figure 11. Diagram showing sampled positions in flow cross-section

Figure 12. Location of sampled points with relation to the discharge elbow

32with samplers in positions one, four, and seven (Figure 11) was conducted at a distance of 26 inchesc

Preparation of Settling Tanks;

The sample settling tanks were prepared by lining them with plastic on which the sand sample was collected. The water spreading cans were placed at one end of the tanks, and the hoses from the samplers were fixed to the cans in the appropriate tanks. The tanks were then covered with plastic to prevent dirt and sand from contaminating the sample.

Test Procedures

The Sparling meter reading was first recorded as the initial reading for the run. The pump was started and the time of start recorded. The flow rate used in each run was regulated with the gate valve, and measured with the Sparling meter and a stopwatch. The maximum velocity was 7,5 feet per second, and the minimum velocity was 4,9 feet per second.

The cross-sectional area of the sampler tube was 1,03 percent of that for the discharge pipe, and the sampler discharge was made to be that same percent of the total pipe discharge. This discharge was regu­lated by measuring with a 5-gallon container and a stopwatch, using a trial and error process. The sampler discharge was checked at least once during the run to insure its accuracy. As the sample settling tanks filled, the return pump was started and regulated to equal the sampler discharge.

33The sand injection rates were determined both by the speed of the

injector action and the relative particle size of the sand mixture being injected. The injection rate of the sand was directly proportional to the speed of the injector chain, although the relationship was not linear, A sand mixture which contained a large percentage of coarse fractions passed through the injector faster than a mixture containing more fines for the same chain speed. No investigation was made to determine why this happened, but this did affect the sand injection rates. The highest concentration used was determined by a combination of the lowest dis­charge and the fastest chain speed. With a relatively coarse sand mixture this resulted in a concentration of about 68 parts per million. The lowest concentration of about 10 parts per million was obtained when the highest discharge and the slowest chain speed were combined.

After all adjustments had been made the injector was started and the time of start recorded. During the run the sand level in the in­jector hopper was checked regularly to make sure the sand was being in­jected properly. As the sand level neared the bottom of the hopper it was checked more frequently until all the sand was gone. The time when the last sand was injected was recorded to the nearest minute. The pump was then stopped and that time recorded. The Sparling meter reading at that time was also recorded as the final reading for the run.

After the run had been completed the water in the sample settling tanks was pumped back into the supply tank. The plastic liners were removed and put on a wooden frame. The sand which had collected on the liners was rinsed into a 200 mesh cloth (Figure 13), then washed from the cloth into a can. The sample was allowed to settle to the bottom of

Figure 13. Rinsing plastic liner to recover sand samples on 200 mesh cloth.

the can and the excess water poured off 0 The samples were then dried with a gasoline stove and screened0 The weights of the different size fractions in the sample were recorded to the nearest one-tenth gram0

The average pumping rate was calculated from the total pumping time and the difference in the Sparling meter readings0 Using this, the total injection time, and the total amount of sand injected the sand flow rate was calculated in parts per million0

RESULTS AND DISCUSSION

Particle Size Distribution;

A requirement of the sampler was to collect a sample having the same particle size distribution as the sand in the flow. Samples taken at various distances from the elbow (Figure 12) were analyzed to de­termine how the particle size distribution for various positions in the pipe cross-section changed with distance downstream from a point of high turbulence. Turbulence caused by the elbow was assumed to distribute the sand so that the particle size distribution over the pipe cross- section would be uniform.

Figures 14 through 17 show a comparison of a series of samples taken 14 inches from the elbow for an average flow velocity of 7.5 feet per second and different sand concentrations. Figure 14 shows the parti­cle size distribution for samples taken at the top, middle, and bottom of the pipe compared with the distribution of the injected sand, which was a mixture of hand-washed river sand. The points show little differ­ence between samples taken at the three positions, and are in good agreement with the curve for the injected sand. In Figure 15 the results are shown from a run with a mixture of machine-washed river sand with the remaining conditions the same as in Figure 14. Again there is no ap­preciable difference between samples taken at the three positions but all three had a range of distribution finer than what was assumed to be in­jected. This indicates that finer particles which had held together

37

100

30

IEi

. Ulr-stifflE lIl. aij _ A - sompler jLn siiod (} - sampler ba4t<

-4- - In je c ted sand

40

4.0 6.0 100.4 0.6 1.0 2.00.1 0.2PARTICLE SIZE (millimeters)

Figure 14. Particle size distribution of samples and injected handwashed sand for a test 14 inches from the elbow. Velocity 7.5 feet per second and sand concentration 49.5 parts per million.

100

80

C4It=4

I60

saiop[ler at s mpjler :.n m iddle

()- samp|Ler botjtora :=--- -injected sand----

40

0.4 0.6 1.0 4.0 6.0 100.1 2.00.2PARTICLE SIZE (millimeters)

Figure 15. Particle size distribution of samples and injected machine washed sand for a test 14 inches from the elbow. Velocity 7.5 feet per second and sand concentration 35.7 parts per million.

33

100

30

JH _r_JL agam U t, %S A - sampler in m^llje 3 - sampler at b< ti:oin- - jLid ct:# s4*<:________-

40

20

0.1 0.4 0.6 1.0 4.0 6.0 100.2 2.0PARTICLE SIZE (millimeters)Figure 16. Particle size distribution of samples and injected reused

sand for a test 14 inches from the elbow. Velocity 7.4 feet per second and sand concentration 21.0 parts per million.

100

80

W1=4H

J3 -. sampler a*t top A - sampler in m:.d lie O - sampler at, botfopi

- — r inj 6cted sAtu t_____

40a

0.1 0.4 0.6 1.00.2 4.0 6.0 102.0PARTICLE SIZE (millimeters)

Figure 17. Particle size distribution of samples and injected sand for a test 14 inches from the elbow. Velocity 7.5 feet per second and sand concentration 9.8 parts per million.

39during sieving had broken down in the water„ Figure 16 is another comparison under the same test conditions with the exception that the injected mixture was made from sand recovered from the supply tank.Again there are only minor differences between samples taken at the three positions, and all are very close to the distribution curve of the injected sand.

The concentration in the run illustrated by Figure 17 was the lowest used in this series, but this did not affect the results signifi­cantly. In all four of these tests the sample particle size distributions are a good representation of the actual distribution since all samples for any one test are in such close agreement.

Figures 18 and 19 represent sand distributions for samples taken 14 inches from the elbow with a flow velocity of 4.9 feet per second.The sand concentration used in the run from which Figure 18 was derived was the highest used in the testing. These figures show that the parti­cle size distribution was not notably changed over the pipe cross-section at this low velocity.

Only one set of samples was collected 26 inches from the elbow, and the particle size distributions found are shown in Figure 20. The water velocity was 7.0 feet per second, but even at this relatively high velocity the effect of gravity on the particle size distribution over the pipe cross-section was apparent. The size distribution graded from finest at the top to coarsest at the bottom.

The size distributions found 38 inches from the elbow are shown in Figures 21 and 22 for flow velocities of 7.4 feet per second and 4.9 feet per second respectively. In both tests the particle size

100

30

S Q — sampla? 9*9---A - sapplet in mijd L<: Q - s a m p le r a^: t o t tout ^--;.;lnrteeWn«tTd:---

0.1 0.4 0.6 1.00.2 4.0 6.0 102.0PARTICLE SIZE (millinetors)

Figure 18. Particle size distribution of samples and injected sand for a test 14 inches from the elbow. Velocity 4.9 feet per second and sand concentration of 72.5 parts per million.

100

30

I

I ,ef flkJsi _.cf i;i utittdtie

: lot.tMi___

40

0.1 0.2 0.4 0.6 1.0 2.0 4.0 6.0 10PARTICLE SIZE (millimeters)

Figure 19. Particle size distribution of samples and injected sandfor a test 14 inches from the elbow. Velocity 4.9 feet per second and sand concentration 13.2 parts per million.

PERCEN

T FINER

41

100

80

60

40 er

20

00.4 0.6 1.00.1 4.0 6.0 100.2 2.0

PARTICLE SIZE (nillineters)Figure 20. Particle size distribution of samples and injected sand

for a test 26 inches from the elbow. Velocity 7.0 feet per second and sand concentration 37.2 parts per million.

PERCENT

FINER

j1

PERCENT

FINE

R

42

100

30

60

40

20

0

ire 21. Particle size distribution of samples and injected sand for a test 33 inches from the elbow. Velocity 7.4 feet per second and sand concentration 40.3 parts per million.

sampler at} sarap .er ir eaispter at Lnjeited aaml

0.4 0.6 1.0 2.0 4PARTICLE SIZE (millimeters)

100

80

60

Q^-sainplet nf tQ*---A - sampled lA nladLe O - sapplet at totjttmi

40

20

00.2 0.4 0.6 1.0 2.0 4

PARTICLE SIZE (millimeters)Figure 22. Particle size distribution of samples and injected sand

for a test 33 inches from the elbow. Velocity 4.9 feet per second and sand concentration 55.1 parts per million.

43distribution graded from fine at the top to coarse at the bottom with the greater spread associated with the lower velocity.

Figures 23 and 24 show the particle size distributions for samples collected 62 inches from the elbow for flow velocities of 7.4 and 5.0 feet per second respectively. In these tests there was a very large spread in the particle size distributions with the coarsest being at the bottom and the finest being at the top of the pipe. The differ­ence was so great in these samples that it could be easily detected by observation. Velocity had a negligible effect.

The samples taken 14 inches from the elbow reinforced the as­sumption that the turbulence caused by the elbow distributed all the particle sizes uniformly over the pipe cross-section in that area. Any differences between the sample and the injected particle size distri­bution were probably caused by errors in preparing the injected sand mixture. At this location the velocity and sand concentration ranges used did not appear to have any effect on the distribution of particle sizes in the pipe.

As the distance from the elbow was increased from 14 to 26 inches the uniform distribution of particle sizes over a cross-section was altered by gravity so that the larger particles were more concentrated on the bottom. This was more pronounced at 38 inches, where the effect of gravity was magnified by the lower velocity. The sample collected at the center of the pipe was representative of the injected size distri­bution at the higher velocity, but none of the samples were representative at the lower velocity. Sixty-two inches from the elbow the distribution

PERCENT

FINER

PERCENT

FINER

44

100

30

60

[“I • sa: nplet a ; t op..A -• sampler in s ltd Us G - sample]: ai: lot t am

*i injected ;?ard___

40

20

04.0 6.0 100.4 0.6 1.0 2.00.1 0.2

PARTICLE SIZE (millimeters)igure 23. Particle size distribution of samples and injected sand

for a test 62 inches from the elbow. Velocity 7.4 feet per second and sand concentration 37.3 parts per million.

100

80

60

U - sampler ar joj-..A - sampler in middle O *| satnplei: a:: Iottm ln[1ect d iid

40

20

04.0 6.0 100.4 0.6 1.00.1 0.2

PARTICLE SIZE (millimeters)Figure 24. Particle size distribution of samples and injected sand

for a test 62 inches from the elbow. Velocity 5.0 feet per second and sand concentration 48.1 parts per million.

45of particle sizes did not change with velocity. None of the samples taken at this distance were representative.

Sand Concentration;

Another requirement was that the sampler would obtain an accurate sample of the sand concentration of the pumped water. Using the total weight of the samples caught at the seven points (Figure 11) for any one test as a base, the percent which was caught at each point was found and plotted in Figures 25 and 26. The value plotted for the center point was the average of the three samples collected. Near the discharge elbow the greatest quantity of sand was found at the top of the pipe with decreasing quantifies for points lower in the cross-section except for a slight in­crease at the bottom. For the locations farther from the elbow the quantify of sand caught was lowest at the top point and increased gradu­ally with distance from the top of the pipe, The difference between thequantity of sand caught at the top and bottom was greatest for the lowervelocity 48 inches from the elbow, and this was about equal to thedifference found for both velocities 62 inches from the elbow.

For every sample taken the sampler flow rate was adjusted to be1.03 percent of the total pipe flow. To be representative of the sand concentration the sample weights had to be 1.03 percent of the total weight of sand passing through the discharge pipe. The deviation of the weight of each sample from this desired weight was calculated as a per­cent. The percent deviations for samples collected 14 inches from the elbow are shown in Table 1. Samples collected at position 3 were most nearly representative with an average percent deviation qf only 4.8,

DISTANCE FRO

M TOP OF

PIPE

(INCHES)

46

PERCENT OF TOTAL HEIGHT CAUGHT 5 10 15 20 25

1

2

O- 14 inches from elbowA- 33 inches from elbow□ - 62 inches from elbow3

4

5

6

Figure 25. Percent of total weight caught at individual sampling points in tests at 14, 33, and 62 inches from the discharge elbow in a water velocity of 7.4 feet per second and a sand concen­tration of 38.5 parts per million.

DISTANCE FRO

M TOP OF

PIPE

(INCHES)

47

PERCENT OF TOTAL WEIGHT CAUGHT

10 15 20 255

1

2

3O - 14 inches from elbowA- 38 inches from elbow□ - 62 inches from elbow

4

5

6

Figure 26. Percent of total weight caught at individual sampling points in tests at 14, 38, and 62 inches from the discharge elbow in a water velocity of 4.9 feet per second and a sand concen­tration of 57.6 parts per million.

48

TABLE 1

Percentage by Which Sample Weights Caught 14 Inches From the Elbow Deviated From the Weight Needed to be Representative of the Sand Concentration.

Sampler Distance*Position (inches) Percent DeviationNumber

11) Test 1 Test 2 Test 3 Test 4 Test 5 Ave.1 3/8 17.2 39.1 26.3 16.5 18.1 23.42 1 1/8 0.6 14.7 16.1 5.1 20.0 11.33 1 7/8 5.1 0.9 9.7 3.1 5.1 4.84 3 1/8 2.6 16.5 7.0 18.4 18.9 12.75 4 3/8 30.6 31.4 23.2 40.5 29.7 31.16 5 1/8 34.9 39.1 32.2 44.5 39.3 38.07 5 7/8 5.8 23.0 19.0 28.1 22.6 19.7

*Distances measured from the inside top of the pipe to the center of the sampled point.

49The variation in weight caught at the same position for different

runs was an indication of the consistency.of the samples, since a constant amount of sand was injected for each run. Seventeen samples were collected at the center of the pipe 14 inches from the elbow. This was the greatest number of samples for any location and consequently the best opportunity for an analysis of sampling consistency. The velocity, sand concentration and weight of sample caught at this position for 17 runs are shown in Table 2. These samples had an average weight of 121.7 grams with a standard deviation of 10.8 grams. Position number 3 was most nearly representative of the sand concentration. Five samples taken at this position had an average weight of 142.4 grams and a standard deviation of 8.5 grams. Neither the velocity nor the sand concentration had a notable effect on the amount of sand caught per sample at any par­ticular position 14 inches from the elbow, and the consistancy of the weight of samples caught at this location was considered acceptable.

The percent deviations in weight for samples caught 26, 38, and 62 inches from the elbow were calculated and found to vary with the velocity. One sample from each of two different tests was found to have less than 10 percent deviation, but too few samples were taken to give any check on their consistancy.

Location for Best Sampling;

.The location within the pipe at which the most representative sample could be obtained had to be one where the sample caught was inde­pendent of the sand concentration and particle size distribution, and was representative of both. At least one sample taken at every distance from

TABUS 2

Data For Samples Caught 14 Inches From the Elbow in the Center, of the Pipe.

Water Sand WeightVelocity Concentration of Samples

fps ppm gms4.9 18.0 119.84.9 18.2 117.04.9 18.2 104.74.9 66.7 118.94.9 66.7 125.34.9 72.5 99.47.4 21.0 127.77.4 25.7 133.47.4 26.2 130.37.4 33.7 138.47.4 38.9 116.87.5 9.8 118.47.5 11.2 117.37.5 11.8 115.97.5 33.1 135.27.5 35.7 136.17.5 49.5 114.9Average Weight 121.7 grams.Standard Deviation 10.8 grams.

51the elbow met one of these requirements, but only at 14 inches from the elbow was any one sample representative of both. At this distance from the elbow all samples were representative of the particle size distri­bution, and the consistency of the sample weights for each point was acceptable. The samples collected from position 3 had the least average deviation from the flow concentration, and this was the best location found by these tests for obtaining a representative sample of the sand- content of the water.

Analysis of Errors;

The injected sand was composed of known amounts of different size fractions which had been separated by sieving for 25 minutes. A test was conducted on this sand to determine the errors caused by dry sieving for this limited time. A 100 gram sample of each of the five size fractions was given an additional 15 minute sieving. The weight of sand caught on each of the remaining sieves was recorded as a per­cent of that sample. Table 3 shows the results of applying these percentages as a correction factor on an assumed 100 gram sample with a size distribution typical of those used in the sampler tests. The resultant quantity which would have passed any one sieve changed by no more than 2.68 percent.

The 30 pounds of injected sand may have had as much as 1.5 per­cent of its weight which would have passed the 200 mesh sieve and so would not be included in any sample weight. Also a very small amount of this sand may have been lost in preparing the mixture for injection.

52

TABLE 3A Comparison of the Measured Sand Distribution and the Corrected Distribution for a Typical InjectedMixture„

Size Measured ActualFraction Weight Weight

Gms. Gms.8 to 16 mesh 5.00 4.0516 to 30 mesh 20.00 19.7730 to 50 mesh 40.00 37.4550 to 100 mesh 25 = 00 26.13100 to 200 mesh 10.00 10.91

Measured Actual DifferenceDistribution Distribution Percent 7o Passing % Passing

95.00 95.88 0.8875.00 75.77 . 0.7735.00 37.68 2.6810.00 11.10 1.100.00 0.00 0.00

53

Some errors may have occurred in measuring the sampler discharges. Also during the tests, especially at lower velocities, the larger sand particles caught in the sampler hose at the pinch clamp and caused a reduction in the sampler flow rate for a short period of time until the situation was discovered and corrected. The maximum errors were esti­mated to be about five percent of the desired sampler flow rate.

Variations in the total amount of sand passing any one point in the pipe which were caused by turbulent fluctuations were impossible to control or evaluate, and may have been greater than any errors caused by test equipment or procedure. Therefore the results obtained by the sampler in these tests were considered acceptable.

CONCLUSIONS

lo Only samples collected 14 inches from the elbow were both representative of the particle size distribution and consistant in the

percentage of the total sand caught at any particular position in the

cross-section. The point at which the most representative samples

were obtained was 14 inches from the elbow and 1 7/8 inches from the

inside top of the pipe to the center of the sampled point.

2. The particle size distribution found at any position in the

flow cross-section 14 inches from the elbow was representative of that

for the injected sand* At 26, 38, and 62 inches from the elbow the

particle size distribution of the sample was dependent on the vertical

position in the flow cross-section with the coarser samples found near

the bottom. No sample taken 62 inches from the elbow was representative

of the particle size distribution of the injected sand.

3. The particle size distribution of any samples taken 14 inches

from the elbow was independent of the flow velocity. Thirty-eight inches

from the elbow the concentration of coarse material at the bottom was greater with the lower velocity9 but 62 inches from the elbow the distri­

bution was no longer affected by the velocities within the range used.

4. The particle size:distribution of samples collected in these

tests was not affected by the sand concentration within the ranges used.5. Fourteen inches from the elbow the larger quantity of sand

was located at the top of the pipe. This would result from a higher

54

55

velocity in this area with a uniform sand concentration over the flow cross-section. At points tested beyond 14 inches the largest quantity of sand was found at the bottom of the pipe,

6, The limited range of velocities and sand concentrations used in these tests does not permit extension of the results with any degree of confidence. No method of correlating the results with pipe diameter was found which would permit application of the results to other pipe sizes,

7, The sand used in conducting laboratory tests of a sampler must be thoroughly washed and sieved to insure that the size distri­bution of the injected sand is accurately known,

SUGGESTIONS FOR FURTHER STUDY

lo More tests should be conducted with a wider range of velocities and sand concentrations emphasizing locations within two feet of the discharge elbow to obtain sufficient data for a statistical analysis of sampler performance,

2, Testing should be done using different pipe diameters and discharge elbow designs to obtain information for locating the best sampling point under varying conditions, '

3, A study of the velocity distribution conducted in connection with the sand sampling tests would aid in understanding the sand distri­bution pattern.

4, Tests should be conducted on field pumping installations to correlate the quantity and character of the sand being pumped with pump wear.

56

SELECTED BIBLIOGRAPHY1. Anderson, Alvin G. A Combined Suspended-Load Sampler and

Velocity Meter for Small Streams. U.S.D.A. Soil Conservation Service Circular 599, 1941.

2. Bunker, G. C. The Determination of Sand in Well Water. Waterand Sewer Works 90;228, 1943.

3. Durand, R. Basic Relationships of the Transportation of Solidsin pipe-Experimental Research. Proceedings of the Inter­national Association for Hydraulic Research, 1953, p. 89.

4. Howard, G. W. Transportation of Sand and Gravel in a Four-InchPipe. Transactions, American Society of Civil Engineers.Vol. 104, 1334-1380, 1939.

5. Matlock, William G. Thesis, A Comparison of Field Performancewith Design Characteristics of Deep Well Centrifugal Turbine Pumps, University of Arizona, Tucson, Arizona, 1960.

6. Matlock, William G. Personal Communication. 1962.7. Rehnberg, Rex D. The Cost of Pumping Irrigation Water, Pinal

County, 1951. The University of Arizona. Agricultural Experiment Station Bulletin 246, 1953.

8. Rossum, John R. Control of Sand in Water Systems. Journal AmericanWater Works Association. Vol. 46, No. 2, 123-132, February 1954.

9. Schwalen, Harold C. Impeller Adjustments and Their Effect Uponthe Field Operating Characteristics of Deep-Well Turbine Pumps, Paper presented at the Pacific Coast Section Meeting of the American Society of Agricultural Engineers, Litchfield Park, Arizona, February 7, 1941.

10. Wilson, Warren E. Mechanics of Flow with Noncollodial InertSolids, Transactions, American Society of Civil Engineers.Vol. 107, 1576-1594, 1942.

11. Winn, B. B. Personal Correspondence with the Author. EquipmentEngineers Incorporated, Palo Alto, California. February, 1963.

12. Yarnell, David L. and Floyd A. Nagler. Flow of Water Around Bendsin Pipes. Transactions, American Society of Civil Engineers. Vol. 100, 1018-1043, 1935.

57