Yoshitake GD-26GS User manual

EPDT-089a
MODEL GD-26GS, GD-27GS
Pressure Reducing Valve
PRODUCT MANUAL
Thank you very much for choosing the Yoshitake’s product. To ensure the correct and safe use of the product,
please read this manual before use. This manual shall be kept with care for future reference.
The symbols used in this manual have the following meanings.
Warning
This symbol indicates a potentially hazardous situation that, if not avoided, could
result in death or serious injury.
Caution
This symbol indicates a hazardous situation that, if not avoided, may result in
minor or moderate injury or may result in only property damage.
Table of Contents
Overview····································································· 1
1. Feature···································································· 1
2. Specifications
2.1 Specifications······················································ 1
2.2 Nominal size selection ······································ 2 - 3
2.3 Flow rate characteristics chart ································ 3
2.4 Pressure characteristics chart································· 4
3. Dimensions and weights·········································· 5 - 6
4. Operation································································· 7
5. Maintenance and inspection
5.1 Precaution for operation ···································· 7 - 8
5.2 Warning and caution for operation ··························· 8
5.3 Piping example···················································· 8
5.4 Adjusting procedure·············································· 9
5.5 Troubleshooting··················································· 9
5.6 Warning for disassembly and inspection ··················10
5.7 Disassembly ······················································10
6. Exploded view····················································11 - 12

1 EPDT-089a
Overview
This product can be used for a wide range of pressure control in facility of chemical plant and so on since
stainless steel which has high durability, chemical resistance and is hygienic is used for wetted parts.
1. Feature
(1) Stainless steel is used for wetted parts.
(2) Pressure balance structure can keep the reduced pressure at a constant level without being affected by
inlet pressure.
(3) Maintenance and inspection can be conducted easily by disassembling simply from upper side.
2. Specifications
Caution
(1) Please collate with attached nameplate and specification of ordered model.
※Please consult factory in case they do not match each other.
2.1 Specifications
Model GD-26GS GD-27GS
Nominal size 20A - 50A 20A - 100A
Application Air, Other non-dangerous fluids
Inlet pressure 1.0 MPa or less
Reduced
pressure A 0.05 - 0.35 MPa
B 0.30 - 0.70 MPa
Min. differential
pressure 0.05 MPa
Max. pressure
reduction ratio 10:1
Application
temperature 5 - 90°C
Material
Body Cast stainless steel
Valve seat Cast stainless steel
Valve disc EPDM
Diaphragm EPDM
Connection JIS Rc screwed JIS 10K FF flanged
The products of the nominal size 20A to 50Aincorporate a strainer (40 mesh).
Pressure gauge connection port is JIS R1/4.
Caution
(1) For medium including oil, use fluorine rubber for disc and diaphragm.
* If not, disc and diaphragm may be broken.

2 EPDT-089a
2.2 Nominal size selection
<For Air>
●Nominal size selection chart
[Example]
When selecting the nominal size of a pressure reducing valve whose inlet pressure (P1), reduced pressure
(P2), and flow rate are 0.3 MPa, 0.2 MPa, and 200 m3/h (standard condition), respectively, first find intersection
point (A) of the inlet pressure (P1) of 0.3 MPa and the reduced pressure (P2) of 0.2MPa.
Trace down vertically from the intersection point to find intersection point (B) with the flow rate of 200 m3/h
(standard condition). Since intersection point (B) lies between nominal size 25A and 32A, select the larger one,
32A.
Nominal size
(A)
(B)
P
2
: Reduced pressure MPa
P
2
: Reduced pressure MPa
Q: Flow rate m
3
/h (standard condition)
Q: Flow rate m
3
/h (standard condition)

3 EPDT-089a
Flow
rate
Set pressure
Shut-off pressure rise
(0.02 MPa)
Min. adjustable
flow rate
Rated flow
Offset
Reduced pressure
●Nominal size selection calculation formula
•Cv value calculation formula
Nominal size 20A
25A 32A 40A 50A 65A 80A 100A
Rated Cv value 2.3 3.5 6 7 11 21 26 38
2.3 Flow rate characteristics chart
Offset
Pressure range Reduced pressure range Offset
A 0.05 - 0.35 MPa 0.05 MPa or less
B 0.30 - 0.70 MPa 0.10 MPa or less
Q: Max. Fluid flow rate [m
3
/h (standard
condition)]
P1: Inlet pressure [MPa･A]
P2: Reduced pressure [MPa･A]
ΔP: P1－P2 [MPa]
G: Specific gravity
(Specific gravity per air)
t: Fluid temperature [℃]
2
P
P
1
2 >
)PP(P t)G273( 2940
Q
Cv
21
+∆ +
=
2
P
P
1
2 <
1
P2550
t)G273(Q
Cv + =

4 EPDT-089a
2.4 Pressure characteristics chart
This chart shows variation in the reduced pressure when the inlet pressure of 0.60 MPa is changed
between 0.15 MPa and 1.0 MPa after the reduced pressure is set at 0.10 MPa.
Inlet pressure MPa
Reduced pressure MPa

5 EPDT-089a
3. Dimensions and Weights
No. Parts name Material No. Parts name Material
1 Body SCS13 9 Diaphragm EPDM
2 Spring chamber ADC12 or FC200 10 Strainer SUS304
3 Valve seat SCS13 11 Strainer cap SUS304
4 Spindle SUS303 12 Diaphragm shell Brass
5 Retainer SUS304 13 Spring plate C3604
6 O-Ring NBR 14 Adjusting screw SUS416
7 Disc cover SUS304 15 Spring SWOSC-V
8 Disc EPDM
●GD-26GS
Nominal
size d L H1H Weight (kg)
20A Rc 3/4 135 41 170 2.2
25A Rc 1 135 41 170 2.2
32A Rc 1 1/4 180 57 224 4.7
40A Rc 1 1/2 180 57 224 4.5
50A Rc 2 200 61 239.5 6.5

6 EPDT-089a
● GD-27GS 20A-50A
●GD-27GS 65A-100A
(mm)
Nominal
size L H1H JIS 10K FF flanged Weight (kg)
d D C t n-φh
20A 160 41 170 20 100 75 14 4-15 3.9
25A 160 41 170 25 125 90 14 4-19 4.8
32A 200 57 224 32 135 100 16 4-19 8.0
40A 200 57 224 32 140 105 16 4-19 8.3
50A 220 61 239.5 50 155 120 16 4-19 10.8
65A 220 77 329 65 175 140 18 4-19 20.6
80A 230 82 345 80 185 150 18 8-19 22.0
100A 270 94 412 100 210 175 18 8-19 34.5

7 EPDT-089a
4. Operation
The spring is compressed by the adjusting screw,
the diaphragm is pushed down, and thereby the
disc directly connected to it is opened.
Fluid coming in from the inlet side flows out from
the upper part of the disc to the outlet side, and
passes through the reduced pressure detection
hole, and is led to the bottom of the diaphragm.
The load of the spring and the reduced pressure act
to the diaphragm, and the upper and lower force
keeps a balance and regulates the valve opening.
As a result, the diaphragm keeps the reduced
pressure constant.
5. Maintenance and inspection
5.1 Precaution for operation
Caution
1. Do not disassemble the product unless it is necessary.
* Unnecessary disassembly prevents the product from functioning properly.
2. Before installing the product in the piping, be sure to remove foreign substances and scale from the
piping.
*Ingress of foreign substances, scale or seal agent into the product leads to valve leakage or
malfunction of the product.
3. Be sure to install a strainer at the inlet side of the product of nominal size 65A to 100A.
*Ingress of foreign substances or scale into the product leads to malfunction of the product. It is
recommended to use a strainer of 40 mesh or more.
4. Install a safety relief valve for equipment protection at the outlet side of the product.
* Failure to follow this notice may result in damage of the equipment.
5. Be sure to install pressure gauges at the inlet and outlet sides of the product.
* Failure to follow this notice hampers correct pressure adjustment.
6. If a quick operating valve such as a solenoid valve is installed, place it at a distance of at least 3 meters
from the product.
* Failure to follow this notice may result in malfunction or a drastically shortened service life of the
product.
7. For two-stage pressure reduction, keep a distance of at least 3 meters between each product.
*Failure to follow this notice may prevent the product from functioning properly due to malfunction.
8. Install the product properly by checking the inlet, outlet and proper posture.
* Installing the product in wrong directions prevents the product from functioning properly.
9. Install pipes so that excessive load, torque or vibration is not applied to the product.
* Failure to make durability lower or cause malfunction.
(1) The product can be installed either horizontally or vertically.
(2) A space more than the value shown as H2in the table below is required for disassembly and inspection.
A space more than the value shown as H3in the table below is required for the inspection of the built-in
strainer (nominal size 15A to 50A).
Adjusting
screw
Diaphragm
Reduced pressure
detection hole
Disc
Spring

8 EPDT-089a
(mm)
Nominal size 20A 25A 32A 40A 50A 65A 80A 100A
H2250 250 300 300 320 450 450 550
H390 90 120 120 150 - - -
5.2 Warning and caution for operation
Caution
1. Before leading fluid into the product, close the stop valves at the inlet and outlet of the product and
remove foreign substances and scale from the piping completely by using a bypass line.
* Failure to follow this notice may prevent the product from functioning properly due to the ingress of
foreign substances and scale into the product.
2. To adjust the set pressure, turn the adjusting screw slowly.
* Failure to follow this notice may result in damage to the product and other equipment due to hunting
or other cause.
3. When the product is not used for an extended period, completely discharge fluid from the product and
pipes, and close the stop valves at the inlet and outlet sides of the product.
* Failure to follow this notice causes malfunction of the product due to rusting inside the product and
the pipes.
5. The set pressure may be affected by ambient temperature (external temperature) and fluid temperature.
Install pipes so that the product may not be exposed to direct sunlight.
5.3 Piping example
Warning
When the product is used for hot fluid, do not touch the product with bare hands.
* The product having hot fluid may scald your skin.
By-pass Globe valve
Pressure gauge
Inlet side Stop valve GD-26GS Stop valve
Pressure
gauge Safety valve
Outlet side

9 EPDT-089a
5.4 Adjusting procedure
Following a wrong adjusting procedure may cause hunting, scale problems or other problem, and can
heavily damage the main parts of the valve. To avoid these problems, be sure to follow the procedure
given below
1. Close the stop valves at the inlet and outlet sides of the reducing valve, and take adequate time to
blow out fluid by using a bypass line. In doing this, adjust the opening of the globe valve in the by-
pass pipe so as not to blow out the safety relief valve.After the end of blowing, close the globe valve
without fail.
2. Fully open the stop valve at the inlet side slowly, and open the stop valve at the outlet side so that a
little fluid can flow through.
3. Remove the domed cap nut and turn the adjusting screw [14] while watching the pressure gauge at
the outlet side.
•Turn the adjusting screw to the right (clockwise) to increase the reduced pressure.
•Turn the adjusting screw to the left (counterclockwise) to decrease the reduced pressure.
4. Fully open the stop valve at the outlet side slowly.
5. After the adjustment is complete, tighten the domed cap nut.
5.5 Troubleshooting
Trouble Cause Remedy
Abnormal pressure
rise at the outlet side.
1. Foreign substances stuck between
the disc [8] and the valve seat [3], or
scratch on them.
1. Disassemble the product and remove
the foreign substances. If scratch is
observed on the valve disc or valve
seat, replace it.
2. The O-ring [6] is damaged. 2. Replace the O-ring.
3. The diaphragm [9] is damaged. 3. Replace the diaphragm.
4. There is a leakage from the globe
valve of the by-pass line. 4. Repair or replace the globe valve.
Reduced pressure
does not reach the
desired value.
1. The working pressure is improper. 1. Correct the working pressure. (See
“2.1 Specifications” on Page 1.)
2. The nominal size of the product is
too small for the flow rate for use. 2. Replace the product with the proper nominal size.
3. Pressure adjustment is improper. 3. Readjust the pressure in accordance
with the given procedure.
4. Strainer built in the product is
clogged. 4. Clean the strainer.
5. Pressure gauge is broken. 5. Replace pressure gauge.
Abnormal sound
1. The nominal size of the product is
too large for the specifications of the
system.
1. Replace the product with the proper
nominal size. (See “2.2 Nominal size
selection” on Page 2.)
2. The pressure reduction ratio is too
large or the maximum pressure
difference is exceeded.
2. Reduce pressure in two stages. (See
“2.1 Specifications” on Page 1)
3. A quick operating valve is located
near the product. 3. Keep a distance between them as large as possible.
Most of problems with the pressure reducing valve are caused by foreign substances and scale in the
piping. Avoid the ingress of dust and dirt to the product with caution.
A phenomenon similar to valve failure could occur due to the failure of the pressure gauge, leakage or
insufficient tightening of the globe valve in the by-pass line, clogging of the strainer, and other causes.
Check the above possible causes and take a proper remedy and preventive measures.

10 EPDT-089a
5.6 Warning for disassembly and inspection
Warning
1. Completely discharge the pressure inside of the product, piping and equipment before disassembly and
inspection. Disassembly and inspection must be done by experienced professional or valve
manufacturer.
* Failure to follow this notice may result in scalds, injury or contamination on the surroundings due to the
residual pressure.
5.7 Disassembly
1. Exhaust pressure in the piping completely and check if pressure is 0MPa by pressure gauge.
2. Remove the domed cap nut, turn the adjusting screw [14] counterclockwise, and set the spring [15]
free (no load).
3. Remove the bolts of the spring chamber [2] and remove the spring chamber [2]. Then take out the
spring [15] and the spring plate [13].
4. Remove the nut, and then the diaphragm shell [12], and diaphragm [9].
5. Remove the set screws of the valve seat [3], and remove a set of the valve seat.
Nominal size 15A to 50A: Attach the diaphragm shell [12] to the spindle [4], and pull it up.
Nominal size 65A to 100A: Screw the bolt into the valve seat [3], and pull it up.

11 EPDT-089a
6. Exploded view
Nominal size 20A - 50A

12 EPDT-089a
Nominal size 65A-100A