Project Report No. 30

TESTS OF A WIRE MESH WATER FILTER

Prepared by

R. G. Dittig and John B. Herbich

Prepared for

Research and Development DepartmentPuro1ator Products, Inc.

Rahway, New Jersey

Hydraulics DivisionFritz Engineering Laboratory

Department of Civil Engineering

July 1958

I

II

III

IV

V

VI

TABLE OF CONTENTS

Introduction

D~scription of the Test Set-up

Procedure

Test Results

Conclusions and Comments

Appendix

A. Illustrations

B. TestData

C. Sample Calculation

1

1

2

3

4

5

LIST OF ILLUSTRATIONS

Fig. 1 Sketch of Filter Used

Fig. 2 Sketch of Test Setup in the Hydraulic Laboratory

Fig. 3 View of Pumps, Piping and Test Housing

Fig. 4 View of Manometers and Pressure Booster

Fig. S View of Weir Tank with Baffles, etc.

Fig. 6 Pressure Head Loss as a Function of Flow-Test No. 3-7

Fig. 7 Pressure Head Loss as a Function of Flow-Test No. 8-10

TESTS OF A WIRE MESH WATER FILTER

.I. INTRODUCTION

The Hydraulic Laboratory of the Fritz Engineering Laboratory was

approached by the Puro1ator Products, Inc., of Rahway, New Jersey to

determine pressure head losses across a wire mesh fiLter for various

rates of flow. The tests were to cover a range of discharges from zero

to 2,000 gallons per minute with possible pressure drop range from 0

to 30 pounds per square inch. The filters were made of stainless

steel wire and fitted over a cage as indicated in sketch No.1. An

orifice plate with a number of circular openings was installed at the

bottom of the filter. Two alternate designs of cage and orifice plate

were tested as well as two sizes of wire mesh openings of 0.002

inches and 0.005 inches. The filters were installed in a specially

designed test housing supplied by the Purolator Products, Inc.

II. DESCRIPTION OF THE TEST SET-UP

.".. '., ....

The tests were performed on the ground floor-of- the Hyd~aulic

Laboratory. Two pumps were employed in the tests, which when operated

in series had a capacity of between 1900 and 2000 gallons per minute

at pressures sufficient to overcome the an~~~~ted pressure head

loss across the filter. The housing was installed a short distance

from the pumps as indicated in Figure 2 in order to cut_head losses

in the supply system to a minimum. Water was discharged from the

housing into a 20-ft x 4-ft Weir Tank, then passed through a s~ries of

baffles and over a rectangular weir at the end of the tank. Inlet and

outlet pressures were measured with mercury manometers and in addition

Bourdon type pressure gages were installed as a check on the manometer

system. The discharge was measured with the rectangular weir. Figures 3

through 5 show the experimental set-up.

I II. PROCEDURE

Two designs of filter cage and orifice plate were tested as well

as two sizes of wire mesh. Tests were performed on the original design

first (Test No.1 through 7), then on the improved design (Test No.8

through 10). Test N(L 1, for a filter with .002" spacing, was

unsuccessful because of faulty construction of the filter. Tests

No.2, 5, and 10 were performed on .a filter with 0.005" spacing

while Test No.6 was ona :£;ilter with 0.002" spacing. Test No.3' and

4 and 7 were carried out for various combinations of housing, cage,

and orifice plate of the original design; and Test No.8 and 9 were

performed on the cage and orifice plate of the new design. In the

new design the orifice openings could be adjusted to give a bigger or

a smaller opening. Test No.8 covered the orifice fully open while

Test No.9 was for the orifice fully closed. The test procedure was

essentiat1y to take measurements of the inlet pressure and outlet

pressure corresponding to various rates of discharge. Each test con­

sisted of 4 to 8 rates of discharge (or runs) and for each run the

following data were taken: (a) a hook gage reading giving the head

on the weir, (b) an inlet manometer reading,. (e) an inlet pressure

gage reading, (d) an outlet man.ometer reading, (e) and an outlet gage

pressure and pressure booster reading. At the higher rates of discharge

it was nOted that a partial vacuum formed on the downstream or discharge

'side of-~ .fllter and a fairly high pressure was observed on the inlet. .

'side ~ In order to meas~re the high pressure accurate.ly a combination

)na:'l1Dtnet!i!r and pressure oooster was useq. Begulat.ion of the dischat'ge

was l1I8de at the pumps ~ some distance upstream from the test section~

<.figure 2).

IV'. TESTRE'SULTS

The test data have been calculated and are summarized in Table

No.1. Test No~ 1 was omitted from this table and Test No.2 is con-

sidered preliminary. Test No. 3 gives pressure head losses for housing

only for discharges up to 1900 gallons per minute. Test No.4 gives

pressure head losses for the housing, cage and orifice plate for

discharges up to 1560 gallons per minute. Test No. 5 is a test for a

complete filter with 0.005" spacing for discharges up to 1525 gallons per

minute. Test No.8 gives the pressure head losses for the new design of

cage and orifice plate for discharges up to 1580 gallons per minute~

while Test No.9 is for the new design gage and orifice plate with

orifice plate fully closed. The maximum dtschaxge for this test was

1435 gallons per minute. Test No. 10 was for a filter unit with O. 005"

spacing placed in the test housing without the customary cage or orifice

plate.

The data for tests No. 2 through No. 10 are presented in Figures

), and 4» where the pressure loss in pounds per squa~e inch was plotted

against the discharge in gallons per minute. Figure 3 presents the data

for the original design, while Figure 4 is for the improved cage and

orifice plate.

A sample calculation is attached to this report as Appendix A.

V. CONCLUSIONS AND COMMENTS

It will be noted in Figures 6 and 7 that lines connecting data

points for housing only (Test No.3) and for filter only (Test No. 10)

are essent~ally straight lines. This is not the case for the data from

the complete filter assembly, or cage and orifice plate, or orifice plate

only as the plots resulted in lines which for higher rates of flow seem

to curve asymptotically to some maximum discharge value. It is normally

expected that a straight line relationship on a logarithmic plot between

pressure head loss and discharge would be obtained. One of the possible

explanations is that cavitation occurred at high rates of flow through

the cage and orifice plate. This is characteristic nnly of the

experimental set-up or any similar installation where a partial vacuum

(pressures less than atmospheric) would exist on the outlet side.

(Table I, Column 3). It is understood that pressures will be considerably

higher in the actual installation (2000 - 3000 pounds per square inch)­

hence no cavitation will occur. It is suggested that for calculation of

actual pressure head loss a straight line should be drawn based on data

for the lower discharges.

VI. APPENDIX A

Illustrations - Figures 1 - 7

I t::::::===~. I

-6

LbJI---

III

WI..,. e.SCree",

-6

Fig. 3 - View of Test Housing and Main Pumps

Fig o 4 - View of Pressure Measuring Devices

Fig. 5 = View of Rectangular Weir

-11

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I :.j', l ;J :')

hut""'.dre.ds +hoUS~f"\d.s

- .o •

G. P. M.

Fig.6 Pressure Head Loss as a Function of Floy - Test No. 3-7

-12

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I .5 2. i ~ P ~ , , 1 ~ 2 2,J' 4 --'------'1l'-'--9'--"0

hu~dreds thousands

G.P.M.

Pig.' Pressure Head Lo88 as a lUnction or Flow - Test No. 8-10

VI. APPENDIX B

Tabulated Test Data

TABLE I

TEST #2 ". -: FIL'TER WI'THQ. 005" SPAGING

Inlet . Outlet Pressure..Pressure.. .Pressure. Head Loss Discharge Remarks

fj (Psi) (Psi) (Psi) GPM

1 1.46 -.12 1.58 372 preliminary2 12.72 - . .73 13.45 915 (11 1- 10)3 32.10 -1.40 32.60 127045 53 .. 10 -1.68 54.98 13906 57.00 -1.42 58.42 12807 . 23.50 -0.40 23.90 6788 3.14 1:'14 1939 48.60 -2.04 50.64 1530 *Filter clean

10 13.30 -0.40 13.70 678

TEST #3 - HOUSINGON~Y (NO FILTI;:R, NO CAGE)

11 2.60 0 2.60 109012 5.98 0 5.98 .149013 10.60 0 10.60 190014 1.33 0 1.33 825

TEST 14 HOUSING CAGE .AND ORIFICE PLATE

.15 5.12 0 5.12 66016 10 .02. 0 10.02 91017 22.28 0 22,.28 119018 33.80 3.34 37.14 138019 47.88 12.50 60.38 1560

TEST·iJ:5 - FILTER WITH 0.005" SPACING

20 3.31 0 3.31 50521 6.70 0 6.70 69222 11.24 0 11.24 89523 18.38 0 18.38 107024 32.03 0 32.03 130025 48.70 13.1 61.8 1525

TEST 16 - FILTER WITH 0 .002" SPACING

26 .2.04 0 2.04 35027 .4.94 0 4.94 52028 8;24 0 8.24 67029 11. 58 0 11.58 78530 15.98 0 15.98 92231 2A.82 0 24.82 107532 38.65 0 38.65 128033 51.82 -9.40 61.22 1420

..• TES:r ·.fn. - HOUS.INGAN:Q ,ORIFIGE PLATE ONLY" ', .."

.Inlet Outlet PressurePressure .Pressure He~dLoss ' Discharge .Remarks

.# (Psi) (Psi) (Psi) GPM

34 :1..23 0 1.23 40035 2.90 0 .2.90 70036 10.38 .0 10.38 100037 Fl .') 0 19.25 1240

19025 0 19,.• 25 ·],24038 26.60 -1. 74 28.34 .140039 44.50 -12.54 57,04 1650

.TESTD8 :- NEW .CAGE&9RI~ICEP4.1'E .- ORIFICE:FULLY.9P~

I"c...;'

4142·43·4445

1 • L~L:.

),156,38

12,8418.,38

... 27.4.6

oooo

0.332,78

1,.44.. 3,156.38

12.8418.71

. 30,24

525,720·950

.1.240U80

.1580

TEST #9 -NEW CAGE & .ORIFICE. PLA'l',E .-O);UFIC~FULL.y. CL.0SEP

46.4748

.49505152

1.85·4,78.9.0616,,373L5043.950.8

ooooo

-5,07-8.52

1.85.4,789.06

16.,3731. 5048,9759.32

.378.564765960

1195.13751435

.TEST,': #10 - 0.00 5" FI~~ER9~Y (NO .CAGE·OROR,IFICE)

5354555657

'1:422.24

.4,996.769,83

oooo

-1.63

L42'2.,24

4.996.76

11.46

720915

1215.14251825

VI. APPENDIX C

Sample Calculation

SAMPLE .CALCUlATIONS

Runs No. 2 and 3

Rectangular contracted .weirLength of crest = 2.565~ft.

Height of crest ~ 1.525-ft

Equation of flowQ ,CD 2/3 2g (L - 0.2 H) H3/ 2

where Q = discharge (cfs)L = length of crest (ft)H = head on .weir crest (ft)CD = coefficient of discharge -

varies between 0.615 and 0.660 depending on head.

For Run No. 3

-17

Hook gage reading:Less gage zero:Head on weir:

Coeff. of disch. (en) = 0.635

DiScharge (Q) = 2.84-cfs or 1270 gpm

INLET PRESSURE: Run No.2ope~ to G\\ \-

I))~erq- E... !!61

t0

oj- 0-

~erocu...) _ 13.\ 'rl.=

0.772-ft0.2870.485-ft

Left reading:Right reading:Differential:

+12.70-in-13 .3526.05-in

0.4545 ( l:::. Hit) = 0.875 = Inlet Pressure (psig)= 12.72 psig

INLET PRESSURE: ,Run No. 3(with air booster)

A,~R-essore.

Left reading (L):Right reading (a):Differential:

+2.20-in-2.404.60-in

-18

~-in dl'~

lY\\e-\ ~033\e.

Air pressure: (Pa) :144 Pa + (1.01 - L)

30 psig62.4 + 847 AW' /12 - (R ~ 1.01)

= Inlet Pressure (psfg)= 7517 psfgqr 32.1 psig

62.4

OUTLET PRESSURE: Run No. 3

o

b"d'\~

OuHe1No~~\e

Left reading:Right reading:Differential:

O. 45-i~'-0.450.• 90-in

0.491 A H" = 0 .07 = Outlet Pressure (psig)= 0.51 psig vacu~m. ''.,

PRESSURE DROP: Run No. 3

32.1 + 0.5 ~. 32.6 psig