Full factorial DOE to determine the influence of [624078]

Full factorial DOE to determine the influence of
the process parameters in cleaning water jets used in sewer cleaning
Nicolae Medan1,/g13, Mircea Lobontiu1, and Mihai Banica1
1Technical University of Cluj Napoca, North University Center Baia Mare, 62A, Dr. Victor Babes
Street, 430083 Baia Mare, Romania
Abstract. Industrial cleaning is a classic application of water jets
technology. In the late 1950s, when reliable high pressure pumps were built,
the usage of water jets spread widely in the field of pipes and sewerage
cleaning. In our particular case, water jets using pressure between 100 and
200 bars are being used. The operational behaviour of these systems is
dependent on the process parameters, which can vary, causing variations in
the impact force. The experiment consists in the research method used in the
study of the impact forces that occur in the sewerage cleaning head system.
To determine the influence process parameters have on impact forces, the
full factorial method was used. In order to measure the impact forces
between the water jet and a flat and rigid surface, a stand was designed and
built for generating pressure water jets, as well as a device to measure the impact forces.
1 Introduction
Phenomena that occur in th e cleaning water jets are complex. Ad ler [1] describes mechanisms
occurring at the impact of a jet with a surface. Leach et al [2], Leu et al [3] and Guha et al [4] analysed pressure distribution along the centreline of the water jet. A number of papers have
studied the influence of nozzle geometry on water jet [5-7].
The aim of this paper is to determine the influence of process parameters on impact forces
produced by water jets from the sewerage system cleaning head, impact forces that depend
on the process parameters. In order to measure th e impact forces between the water jet and a
flat and rigid surface, a stand for generating pressure water jets, as well as a device to measure the impact forces have been designed and bu ilt. In the measurements, water jets using
pressure between 100 and 200 bars have been used. The values of these pressures correspond
to low pressure water jets [8].
To carry out an experimental research, it is recommended to follow a series of steps [9]:
1) recognition of and statement of the problem, 2) selection of the response variable, 3) choice
of factors (process parameters), levels, and range s, 4) choice of experimental design, 5)
performing the experiment, 6) statistical analysis of the data, 7) conclusions and
recommendations.

/g13 Corresponding author: Ni [anonimizat]
DOI: 10.1051/ , (2017) 79407005 94 matecconf/201 MATEC Web of Conferences
CoSME'1607005
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative
Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).

To determine the influence of process parame ters on impact forces produced by water
jets from the sewerage system cleaning head the research method used is full factorial
method.
2 Apparatus used and methodology of the measurements
In order to measure the impact forces between the wat er jet and a flat and rigid surface, a
stand for generating pressure water jets, as well as a device to measure the impact forces were
designed and built [10].
2.1 The stand to generate pressure water jet
Schematic diagram of the stand to generate a pressure jet is shown in figure 1.
The component parts of the stand are: 1) electric motor 2) flexible coupling; 3) high
pressure pump, 4) pressure regulat or, 5) pressure gauge, 6) nozzle, 7) tap water, 8) water
tank, 9) chassis.
Water coming out of the high pressure pump (3 ) goes into the pressure regulator (4). The
pressure regulator adjusts the pressu re and flow of the water in the path of the high pressure
water. This pressure corresponds to the one at the outlet of the nozzle.

Fig. 1. Schematic diagram of th e stand to generate pressure jet.
2.2 The device to measure the impact forces
Figure 2 represents the prin ciple diagram of the device for the measurement of the impact
force between the water jet and a flat and rigid surface.
The main component parts of the device are: 1) high-pressure water hose, 2) support
nozzle, 3) nozzle block, 4) nozzle , 5) water jet, 6) flat and rigi d target plate, 7) collection path
water, 8) scaled container, 9) piezoelectric sensor mounting, 10) piezoelectric sensor, 11)
data acquisition Personal Daq/3000, 12) computer for the processing of data; 13) support
plate, 14) acrylic tube, 15) rods for adjusting distance x.
From the high pressure water hose (1) the wa ter comes at a certain pressure p desired. A
water jet is generated at the outlet of the nozzle (5) that strikes the target plate (6), which it
located at a certain distance x in front of the nozzle. The jet (5) generates an impact force at
a time when it meets the target plate (6). This force produces axial movement of the target
plate. This movement is converted into an electric signal by the piezoelectric sensor (10).
Electrical signals are collected by data acqui sition Personal Daq/3000 (11), which forwards
data to a computer (12) using DaqView soft processes. Thus, accurate data is obtained.
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Fig. 2. Diagram of the device for the measurement of the impact force of the water jet.
2.3 Process parameters and geometric configuration of nozzles
In the water jet cleaning process a series of parameters are involved [8]. These parameters
can be divided into two major groups, namely: 1) target parameters which shall be defined
according to the contact area between the water jet and the surface to be cleaned and 2)
process parameters. In the measurement of the impact forces of a stationary water jet and flat
and rigid surface the process parameter s are involv ed (figure 3).

Fig. 3. Process parameters.
They can be divided into two groups, namely hydraulic parameters and the performance
parameters. Hydraulic parameters characterized by the system’s high pressure pump-nozzle
are represented by work pressure (p), volume flow ( Q/g120) and nozzle diameter (D). The
performance parameters are more related to th e process performance and include the
following: cleaning distance (x), impact angle (/g302) and traverse rate (v T). For a stationary
water jet v T= 0 m/s.
Setting the values of process parameters, as follows:
1)The diameter D of the nozzle. The values used are D=1mm, 1.5 mm and 2 mm. These
are common values used in equipment designed for maintenance and cleaning of sewers. The
material used for the nozzles is stainless steel. Figure 4 sh ows the geometric configuration of
the nozzles used.

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Fig. 4. Geometric configuration of the nozzles.
2) The pressures p used to perform the m easurements have the va lues p=100 bar, p=120
bar, p=140 bar, p=160 bar, p=180 bar and p= 200 bar. For the maintenance sewers, maximum
pressure used are 200 bars to prevent the damage of the sewer pipe.
3) Cleaning distance x (dist ance from the nozzle to the target plate). Distance x has been
fixed at the values from x=25 mm to x=200 mm, with a step of 25 mm.
4) /g302 – impact angle (the angle formed by the jet with the target plate); in this work
/g302 =600, 750 and 900. For cleaning heads the usual value of the angle of impact /g302 is 750. If
impact angle /g302 decreases below 600 it leads to a drop in of the impact forces.
3 Results
For determining the influence of the proc ess parameters the method used shall be full factorial
design.
3.1 Choice of levels and values for process parameters
Table 1 presents the values of the paramet ers used for full factorial method.
Table 1. The values of the parameters.
Parameter Values
Nozzle diameter D [mm] 1, 1.5, 2
Pressure p [bar] 100, 120,140,160,180,200
Impact angle /g302 [0] 60, 75, 90
Distance x [mm] 25, 50, 75, 100, 125, 150, 175, 200
3.2 Performing the experiment
Taking into accoun t that there are four parameters, the number of values which they each
take and using the Full factorial design results in a number of 144 experiments. For each
experiment three measures of impact fo rce were performed and still it has worked with F med,
representing the arithmetic average of the three forces measured. As a result there are a
number of 432 measurements. With this in mind, for the brief of th is paper, we dare not
present the table with the values obtained.
Based on the values of impact forces obtained usi ng the full factorial method, figures 5,
6 and 7 present the values of impact forces F med which depend on process parameters (values
of process parameters presented in table 1).
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c) /g302 = 600

a) /g302 = 900 b) /g302 = 750
Fig. 5. Values of impact forces fo r nozzle diameter D=1mm for diff erent values of impact angle /g302.

c) /g302 = 600

a) /g302 = 900 b) /g302 = 750
Fig. 6. Values of impact forces for nozzle diameter D=1.5 mm for different values of impact angle /g302.

DOI: 10.1051/ , (2017) 79407005 94 matecconf/201 MATEC Web of Conferences
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c) /g302 = 600

a) /g302 = 900 b) /g302 = 750
Fig. 7. Values of impact forces for nozzle diameter D=2 mm for different values of impact angle /g302.
3.3 Determining the Influence of the process parameters
Using the Full factorial method has conducted an analysis of the variance to determine the
contribution of each parameter and their interactions on the impact force. Table 2 presents
the analysis of the variance, using Minitab 17.
Table 2. Analysis of Variance (Minitab 17).
Source DF
(degree of freedom) Seq. SS
(sum of square) Contribution
Model 103 163,747 99.87%
Linear 16 153,677 93.73%
Diameter 2 117,239 71.50%
Pressure 5 29,641 18.08%
Distance 7 410 0.25%
Angle 2 6,387 3.90%
2-Way Interactions 87 10,070 6.14%
Diameter*Pressure 10 7,626 4.65%
Diameter*Distance 14 333 0.20%
Diameter*Angle 4 1,636 1.00%
Pressure*Distance 35 55 0.03%
Pressure*Angle 10 414 0.25%
Distance*Angle 14 6 0.00%
Error 328 217 0.13%
Total 431 163,965 100.00%

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4 Conclusions
In this paper is presented an experimental research methodology, which uses full factorial
method. This allows determining the influe nce of process parameters to impact forces
produced by water jets.
In order to measure the impact forces between the water jet and a flat and rigid surface, a
stand was designed and built for generating pr essure water jets, as well as a device to measure
the impact forces.
Based on the results of experimental work presen ted in this paper it was determined that
the contribution of the pr ocess parameters and their interactions are, as follows:
-The most important parameter is the diameter of the nozzle, with a percentage of influence
of 71.50%;
-The second parameter is the pressure of water jet, with a percentage of 18.08%;
-The third parameter is the impact angle, with a percentage of 3.90%;
-The distance parameter, with a percentage of 0.25% is virtually insignificant;
-Between interactions only di ameter and pressure have an im portant contribution 4.65%;
-All other interactions have a low importance (from 1% to 0%).
For the experimental domain de fined, only three of the four parameters have influence on
impact forces. Distance x has an influence only 0.25%, so maybe neglected.
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