ANSYS DESIGN OPTIMIZATION OF FOOT VALVE

ANSYS DESIGN OPTIMIZATION
OF
FOOT VALVE
by
Emre SİPAHİ
July, 2004
İZMİR

ABSTRACT
In this study, 500mm diameter Foot Valve components, which are drafted by
DOĞUŞ VANA VE DÖKÜM SANAYİ LTD. ŞTİ for mass production with casting,
were optimized by using ANSYS program to obtain minimum weights.
Volumes of two main parts of the foot valve were reduced to get minimum casting
costs, which is a function of weight of the part to be produced. Relevant parametrical
dimensions were obtained from manufacturers design criterias and international
standards.
Optimum dimensions and weights of foot valve components are evaluated by
considering minimum casting costs and final component designs are completed.
Valve components weights are reduced 6.36% due to optimization processes.
ÖZET
Bu çalışmada, DOĞUŞ VANA ve DÖKÜM SANAYİ LTD. ŞTİ. firması
bünyesinde seri üretimi yapılmak üzere tasarlanan 500 mm. anma çaplı Dip
Klepesinin, döküm tekniği ile üretilecek olan parçalarının minimum ağırlığa sahip
olması için dizayn optimizasyonu, ANSYS programı kullanılarak yapılmıştır.
Üretici firmanın döküm maliyetlerini minimuma düşürmek için, dip klepesinin iki
ana döküm parçasının hacimleri, dolayısıyla ağırlıkları minimuma düşürülmüştür.
Kullanılan parametrik ölçüler, üretici firmanın dizayn kriterleri ve ilgili uluslar arası
standartlardan alınmıştır.
Elde edilen optimum değerler doğrultusunda, dip klepesi parçalarının son ölçüleri
ve nihai ağırlıkları minimum döküm maliyeti açısından değerlendirilmiş ve tasarım
tamamlanmıştır. Optimizasyon işlemleri sonucunda parçalarda ortalama % 6.36
ağırlıktan tasarruf sağlanmıştır.

1. Introduction
In our contemporary world of competition, all companies should supply their
goods and services with high quality in shortest period with lower prices than its
competitors in order to keep their capacity and power to compete. Especially, in the
manufacturing sector, beside to supply the goods in good quality, maximum discount
in prices that companies can provide are being examined heedfully by the customers.
Since it is a must in the business sector to try to obtain goods with high quality and
best price in shortest time period, companies who have that capability will be chosen
by the purchasers.
From the beginning of the last century, the development in the techniques of mass
production and incredible improvement in technology has become the most
significant motive for the companies, which pursue a competitive and open policy.
The companies involving with mass production pay great attention to the
reliability of the product that is the product quality. Thanks to the ongoing
developments in technology, the techniques of new product design has been
improved and facilitated.
The first design of a product that has been in the head of the engineers is
illustrated in computers and then produced by computer-aided machines.
The analysis and optimization processes of a product of which solid modeling
have been accomplished can be carried out by ANYSYS and similar analysis
programs in digital environment, before starting manufacturing. These processes give
the companies flexibility in the development of a new product by providing design
capability with minimum cost and minimum waste of time. ANYSYS program,
which has been used in this study, can make the analysis and design optimization of
the substances in many subjects including static, dynamic, thermal, harmonic and
electromagnetic. Thus, this program can obtain necessary design requirements for a
product in good quality with minimum cost.

Because the weight increases the cost of the product, in order to get a product with
good quality and minimum cost, the weight of the materials should be revised.
However, the companies try to keep their quality level stable when trying to lower
the cost. In this regard, they apply a strict design optimization process in the process
of new product development.
It is widely known that in mass production even small fluctuations in input costs
can affect the overall production costs and sales prices of the companies
dramatically. If the companies have the lowest production costs then they can
decrease their sales prices accordingly which led to an increase in their market share.
In this study, using ANYSIS the static analysis and design optimization of foot
valve with 500 mm nominal diameter and suitable for 16 bar working pressure which
has been newly designed at research and development department of Doğuş Vana ve
Döküm San. Tic. Ltd. Sti. By this optimization process, the thickness of foot valve’s
parts, which are decided to be manufactured from ductile iron, has been minimized
which has a decreasing effect in the volume and weight accordingly. Thus, while
having the lowest cost of casting, the manufacturer will be assured by the quality and
reliability of its product and add this item to its production range at earliest.
2. What is Foot Valve?
Foot valve, as shown in Figure 1, is a kind of valve that is placed at pump intake,
provides water during the starting of pump operation by preventing back flow of
water.
In general, after pump starts operation, the sealing disc of foot valve opens
because of pressure difference and allows water flow. Figure 2 shows the working
principle of the foot valve.

2.1 Forces Acting on Foot Valve Components
After the check valve in the pump line, even while the pump does not work, there
is pressure required in the line. Pump suction line and foot valve are under system
pressure due to a small water leakage of check valve. So PN 16 Bar pressure is
applied to foot valve at the system.
Figure 1. Foot Valve
Check valve Gate valve
Pump suction line
Pump
Pressure line
System
Soil
Water
Level
Foot valve
Water Well
Figure 2. Working Principle of Foot Valve
For a foot valve that will work under these conditions, the manufacturer should
test the foot valve 1.5 times as working pressure as a requirement of ISO 2508

standard. It has been used 25 bar pressure in the analysis and optimization processes,
taking into consideration the maximum test pressure that will be applied after
production.
Figure 3 and Figure 4 show pressure forces on the disc and body parts of foot
valve.
25 bar = 2.5 mpa
Figure 3. Pressure Force on the disc
Sealing Face
Klepe Kapatma
(sızdırmazlık) Yüzeyi
25 bar = 2.5 mpa 25 bar = 2.5 mpa
Figure 4. Pressure Force on the Body
2.2 Valve Material
In this study, International Standards and formulations about Cast Iron Pipes are
used in order to get minimum thickness of components by considering valve
structure, required pressure of pipeline and manufacturer preferences. Valve material
is determined as GGG40 Ductile Cast Iron.

2.3 Material Specifications
ρ ( density) = 7.3 x 10 -6 kg/mm 3
µ ( poisson ratio ) = 0.3
E ( Young Modulus )
= 165.000 MPa
“ Construction σ yield = 125 MPa DIN 1663” (Anık, S., 1999, p.181)
Safety coefficient of stress S safety = 1.2. So ;
σ Safety = σ yield / S safety
σ Safety = 125 / 1.2 = 104.16 ≈ 104 MPa
is determined as upper limit for stress.
2.4 Design Constrains
Cast iron pipes can be studied as four main groups by considering their pressure
strengths as shown at Table 1. However flanged pipes such as Foot Valve are studied
in groups B and C.
German Cast iron norm DIN2431 is related with DIN2531 to determine the
formulation to calculate thickness of cast iron pipes as below;
Group A thickness = 1.1 LA group thickness ( χ = 11 )
Group B thickness = 1.2 LA group thickness ( χ = 12 )
Group C thickness = 1.3 LA group thickness ( χ = 13 )
( Okday, Ş., 1975 p.14 )

Table 1. Max. Pressure values to applied cast iron pipes ( kg / cm 2 )
Pressure ( kg/cm 2 )
Nominal
Manufacture
LA
Diameter
A GROUP B GROUP C GROUP
Type
GROUP
( DN )
Test Pipeline Test Pipeline Test Pipeline Test Pipeline
50 ... 70 20 12,5 25 16 - -
Centrifugal
>70...600 20 10 25 12,5 30 16 N/A
Casting Pipes
>600 15 10 20 12,5 25 16
Casting Pipes
50 ... 70 20 12,5 - - - -
>70...600 N/A 20 10 25 12,5 30 16
>600
15 10 20 12,5 25 16
Thickness of cast iron pipes can be calculated by using χ coefficient and the
formula given below:
Thickness = ( χ / 12 ) x ( 7 + 0.02 DN ) mm. ( 2.1 )
DN is nominal diameter of pipe or valve.
Thickness tolerance can be determined by using formula ( 2.2 ) .
Tolerance = - ( 1 + 0.05 x thickness ). ( 2.2 )
For this study, minimum thickness limit is determined using the following
calculations:
Foot Valve can be studied in Group C;
Test Pressure = 25 Bar
Pipeline Pressure = 16 Bar
DN = 500 mm.
So χ is determined as 13.
Appling Equation ( 2.1 ) to get thickness value,
Thickness = ( 13 / 12 ) x ( 7 + 0.02 x 500 ) = 1.08 + ( 7 + 10 ) = 18.08 mm
Tolerance = - ( 1 + 0.05 x 18.08 ) = -1.904 mm

Minimum thickness value for foot valve components is calculated as;
Minimum Thickness = 18.08 – 1.904 = 16.176 mm.
Due to the capability of sand casting process used for the manufacturing of the
foot valve components, 16mm thickness value is used for the lower limit.
Flange dimensions are complying with ISO 7005 / 2, face to face dimensions are
determined by manufacturer for the following sizes of foot valve DN400 mm., DN
500 mm. and DN 600mm. Inner shape of the body seen in Figure 5, so as to permit
the pass of required water flow rate when the valve is fully open
In order to obtain required flow rate, water volume that passes around the sealing
disc, must be equal to valve inlet water volume. So we have to get diameters by
considering the equality of these volumes. Diameters are shown in Figure 5.
D = Ø700
d1 = Ø490
DN = Ø500
Figure 5. Inner shape calculation
By using inlet diameter and outer diameter of sealing disc (490 mm) inner shape
diameter can be calculated as follows:
( π x DN 2 ) / 4 = ( π x D 2 ) / 4 - ( π x d1 2 ) / 4
DN 2 = D 2 - d1 2 D 2 = DN 2 + d1 2
D 2 = 50 2 + 49 2 = 2500 + 2401 = 4901
D = 70 cm. = 700 mm..

1
For sealing disc, outer shape of disc is same with body sealing face. So it’s
dimensions are constant. ANSYS axissymetric feature is used to optimize symmetric
components. Except the six rib of sealing disc, sealing disc body is optimized with
axissymetric feature. However, six rib weights are not negligible values for sealing
disc weight. Consequently, ribs are optimized separately from sealing disc body.
2.5 Design Parameters
Inner shape, flange dimensions and face to face dimensions are considered as
manufacturer constants. Other appropriate dimensions are optimized. Edge radius
and thickness dimensions are optimized for reducing body weight by considering
state variables maxstress. Edge radius and thickness are determined as parameters
and optimized to reduce sealing disc weights. Height and width dimensions are
appropriate parameters for rib optimization.
Parametric dimensions are shown as drawings in Figures 6, 7 and 8. Also
parameters that are used for optimization are shown in Table 2.
s
r2
s
Figure 6. Parametric dimensions of sealing disc
R3
R2
R2
R3
s
s
s
s
s
s
R4
R1
R1
R4
Figure 7. Parametric dimensions of body

R10
175
135.5
R20
y = 25
g = 16
Figure 8. Parametric dimensions of rib
Table 2. Parameters
Body
Parameter Value Lower Limit Upper Limit
s 18 16 25
r1 10 7 15
r2 18 15 20
r3 10 7 15
r4 18 15 20
Sealing Disc
Parameter Value Lower Limit Upper Limit
s 22 16 25
r1 20 10 25
r2 10 5 20
Rib
Parameter Value Lower Limit Upper Limit
g 16 10 20
y 25 20 30
3. ANSYS Analysis and Optimizations
ANSYS parametric model is drafted by using parameters that are determined at
Section 2. Two kinds of finite elements, quadrilateral two dimensional Plane42 or
Plane82 can be used for analyzing body and sealing disc. Both elements support
axissymetric ANSYS analysis. Plane42 has 4 nodes, Plane82 has 8 nodes. In order to
obtain accurate analyze results, analyzer must use as much as nodes or element
number that he/she can. (Moaveni, S., 1999)

Consequently in this study Plane 82 with 8 nodes is used for axissymetric analyze
processes of body and sealing disc. And 3D Solid 92 element wtih 10 nodes is used
for analyze of rib.
Meshed body, sealing disc and rib model are shown at Figure 9, 10 and 11.
Figure 9. Meshed body model
Figure 10. Meshed sealing disc model

Figure 11. Meshed rib model
For body totally 745 pieces quadrilateral finite elements, 2560 pieces nodes, for
sealing disc 148 pieces quadrilateral finite elements, 537 pieces nodes, for rib 4044
pieces finite elements and 6772 pieces nodes are obtained during the meshing
processes. 25 Bar = 2.5 Mpa pressure is applied on the parts. Figure 12, 13, 14 and
15 shows results of solutions.
Figure 12. Element stress on body before optimization

Figure 13. Symetry expansion view of stress on body before optimization
Figure 14. Element stress on sealing disc before optimization
Figure 15. Symetry expansion view of stress on sealing disc before optimization

Stresses, volumes and weights of body, sealing disc and rib are shown in Table 3.
Table 3. Analysis results
Volume
Body Sealing Disc Rib
26038741.8
mm 3 5115262.9
mm 3 61707.12 mm 3
Weight 190.08 kg. 37.34 kg. 0.45 kg.
Maxstress 47.3132 MPa 66.96 MPa 2.962 MPa
3.1 Optimization
Values that are shown in Table 2 and 3 are used as optimization variables for
optimization processes.
Parametric values shown in Table 2, are used as Design Variables of optimization
processes. Maxstress values that are shown at Table 3, are used as State Variables of
optimization processes and volume values that are shown at Table 3, are used as
Objective Functions of optimization processes.
Upper limit of Maxstress value is 104 Mpa and lower limit is 30 Mpa. Upper and
lower limits of design variables are shown at Table 2. Tolerance of Objective
Function is determined as 10000 mm 3 .
The most accurate optimization method named First-Order Method is used at all
optimization process in this study. For this method maximum iteration number is 10.
Figure 16, 17, 18, 19 and Table 5 show the result of optimizations. Also final
parameter results are shown in Table 6.

Figure 16. Element stress on body after optimization
Figure 17. Element stress on sealing disc after optimization

Figure 18. Symetry expansion view of sealing disc stress after optimization
Figure 19. Element stress on rib after optimization
Table 4. Optimization results
Volume
Body Sealing Disc Rib
24773357.2
mm 3 4500072.82
mm 3 41552 mm 3
Weight 180.845 kg. 32.85 kg. 0.3 kg.
Maxstress 51.705 MPa 101.64 MPa 30.128 MPa

Table 5. Optimized parameter value
Body
Parameter Initial Value
Optimized Design Value
Value
s 18 16 16
r1 10 8.2078 8
r2 18 15.783 16
r3 10 7.840 8
r4 18 17.101 17
Sealing Disc
Parameter Initial Value
Optimized Design Value
Value
s 22 17.398 17.5
r1 20 19.893 20
r2 10 9.8823 10
Rib
Parameter Initial Value
Optimized Design Value
Value
g 16 14.616 15
y 25 20.789 20
1/6 Symmetric model is drafted and analyzed by using dimensions that obtained
from main disc body and rib optimization. There are the final Sealing Disc results as
below;
Table 6. Analysis results of Sealing Disc
Body
790241.9 mm 3 x 6 = 474145.14
Volume
mm 3
Weight
34.612 kg.
Maxstress
90.901 MPa

Figure 20. Element stress on 1/6 sealing disc model
Maximum stress is gathered at intersection region of ribs and main disc body.
Stress on disc that is drafted without radius, exceeded the safe stress value. Casting
part has radius at this region. So this 5 mm radius reduces stress values to 90.901
MPa as seen at Figure 20.
4. Results and Discussion
In this study design optimization of main parts of a foot valve, sealing disc and
body, is carried out using ANSYS® package. The aim of the study was to minimize
the weight of these components, which are manufactured by sand casting.
Results obtained from optimization process are as follows:
• Weight of Sealing Disc is reduced 13.5%.
Initial total weight of Sealing Disc = 40.0 kg.
Optimized weight of Sealing Disc = 34.6 kg.
• Weight of the valve Body is reduced 4.85 %.
Initial total weight of Sealing Disc = 190.08 kg.
Optimized weight of Sealing Disc = 180.845 kg.
• Total Weight of the valve is reduced 6.36 %.
Initial total weight of the valve = 230.08 kg.
Optimized total weight of the valve = 215.445 kg.

In this study, Sealing Disc was optimized at two steps. Disc body and ribs were
optimized separately and then Sealing Disc Body was designed by drafting radius.
In the optimization of valve body, the lower limit of thickness was obtained
without reaching the safe stress value. Therefore, the optimization process provided
the minimum body weight.
More accurate optimization results could be obtained by using computers with
higher capacity.
Weight reduction obtained by the optimization process decreases the casting cost
of the valve. 6.36% weight reduction might be useful to get discount of selling prices
of the valve. As a result of this study, manufacturer has a big chance to sell its
product in competitive market of the world.
References
Anık, S., Dikicioğlu, A. & Vural, M. ( 1999 ). İmal Usulleri
Istanbul : Birsen Yayınevi
Moaveni, S., ( 1999 ). Finite Element Analysis
New Jersey : Prentice Hall Inc.
Okday, Ş., ( 1975 ). Makine Elemanları, Boru ve Kapama Armatürleri ( 5 th ed. )
Istanbul : Matbaa Teknisyenleri Basımevi
Yıldırım, A., ( 2002 ).
Yıldırım, A., ( 2003 ).
Yıldırım, A., ( 2004 ).