Yoshitake GD-28S-NE User manual

EPDT-351
MODEL GD-28S-NE, GD-29S-NE
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
1. pecifications
1.1 Specifications······················································ 1
1.2 Nominal size selection ······································ 2 - 3
1.3 Flow rate characteristics chart ································ 3
1.4 Pressure characteristics chart································· 4
1.5 Noise characteristics chart ····································· 4
2. Dimensions and weights·········································· 5 - 6
3. Operation ································································· 7
4. Installation
4.1 Piping example···················································· 7
4.2 Precaution for installation··································· 8 - 9
5. Operation procedure
5.1 Precaution for operation ········································ 9
5.2 Adjusting procedure········································ 9 - 10
6. Maintenance
6.1 Troubleshooting··················································10
6.2 Precaution for maintenance and inspection ·············· 11
6.3 Disassembly ················································11 - 12
6.4 Precaution for reassembly ···································· 12
6.5 Strainer cleaning procedure ·································· 13
7. Exploded view··················································· 14 – 15
After ales ervice

1
EPDT-351
1
. Specifications
1.1 Specifications
Model GD-28 -NE GD-29 -NE
Nominal size 20A - 50A 20A - 100A
Application Cold and hot water
Inlet pressure 2.0 MPa or less
Reduced pressure A0.20 - 0.35 MPa
B0.30 - 0.70 MPa
Min. differential pressure 0.05 MPa
Controllable range Refer to pecifications election Chart *1
Max. temperature 90°C
Material
Body tainless teel
Valve seat tainless teel
Valve disc ynthetic rubber
Diaphragm ynthetic rubber
Connection JI Rc screwed JI 20K RF flanged *2
 The products from 20A to 50A are equipped with built-in strainer (40 mesh).
 Pressure gauge connection port is JI R1/4.
 Products complying with the Water upply Act
*1: It can be used under the condition that the maximum pressure reduction ratio is 7: 1 within
the controllable range shown in the chart below.
*2: The flange is thicker than the standard value.
If it is out of controllable range, employ two-stage pressure reduction or select another model.
When inlet pressure is 2.0MPa, make sure that reduced pressure is 0.3MPa or more.
Caution
Please collate the plate or label attached to the product with specifications of ordered
model.
* If they do not match each other, please contact us without using the product.
Reduced pressure MPa
MPa
pecifications election Chart *1
1
Controllable range
range
The valve does not fulfill specified
performance in this range.
I
n
l
et pressure

2
EPDT-351
1.2 Nominal size selection
Procedure of nominal size selection
1. If the differential pressure before and after the valve is 0.15 MPa or more, select the nominal size
from the rated flow table below.
Rated flow table (The pressure difference before and after the product is 0.15 MPa or more)
Nominal size 15A 20A 25A 32A 40A 50A 65A 80A 100A
Rated flow (L/min) 30 40 60 100 150 240 300 450 700
2. If the differential pressure before and after the valve is less than 0.15 MPa, select the nominal size
from the nominal size selection chart (for 20A - 50A, 65A - 100A) below.
Nominal size selection chart
Nominal size 20A - 50A
Reduced pressure MPa
Flow rate
L/min
Inlet pressure
Reduced pressure + 0.1 MPa
Reduced pressure + 0.05 MPa
Nominal
size

3
EPDT-351
Flow
rate
et pressure
hut-off pressure rise
(0.02 MPa)
Min. adjustable
flow rate
Rated flow rate
Offset
Reduced pressure
Nominal size 65A -100A
1.3 Flow rate characteristics chart
Offset (Differential pressure after valve seat is 0.15MPa or more)
Nominal size
Pressure range
Reduced
pressure range
Offset
20A-100A
A
0
.2
0
-
0.35MPa
0
.1
0
MPa or less
B
0
.3
0
-
0.7
0
MPa
0.1
5
MPa or less
Reduced pressure MPa
Flow rate
L/min
Reduced pressure + 0.1 MPa
Reduced pressure + 0.05 MPa
Inlet pressure
Nominal
size

4
EPDT-351
1. Pressure characteristics chart
This chart shows variation in reduced pressure when the inlet pressure of 1.0 MPa is changed between
0.35 MPa and 2.0 MPa while the reduced pressure is set at 0.30 MPa.
1.5 Noise characteristics chart (Fluid: Water)
Noise
Noise
Noise
Inlet pressure MPa
Nominal size 20A – 25A
Inlet pressure: 0.6 MPa
Flow rate L/min
Nominal size: 20 A
Nominal size: 25 A
Nominal size 32A - 50 A
Flow rate L/min
Nominal size: 32 A
Nominal size: 40 A
Nominal size: 50 A
Nominal size 65A - 100 A
Flow rate L/min
Nominal size: 65 A
Nominal size: 80 A
Nominal size: 100 A
Reduced pressure MPa
Inlet pressure: 2.0 MPa
Reduced pressure: 0.3 MPa
Inlet pressure: 2.0MPa
Reduced pressure: 0.3 MPa
Inlet pressure: 2.0 MPa
Reduced pressure: 0.3 MPa
dB(A)
dB(A)
dB(A)

5
EPDT-351
2
.
Dimensions and
Weights
Model GD-28S-NE
(mm)
Nominal
size d L H1H Weight (kg)
20A Rc 3/4 135 41 170 2.3
25A Rc 1 135 41 170 2.3
32A Rc 1 1/4 180 57 224 4.9
40A Rc 1 1/2 180 57 224 4.7
50A Rc 2 200 61 239.5 6.7

6
EPDT-351
Model GD-29S-NE
Nominal size 20A - 50A
Nominal size 65A - 100A
(mm)
Nominal
size
L H
1
H d
JIS 20KRF
flanged
Weight
(kg)
g D C n-φh
20A 164 41 170 20 56 100 75 4－15 4.4
25A 164 41 170 25 67 125 90 4－19 5.4
32A 204 57 224 32 76 135 100
4－19
8.7
40A 204 57 224 32 81 140 105
4－19
9.0
50A 225 61 239.5 50 96 155 120
8－19
11.8
65A 225 77 329 65 116 175 140
8－19
21.0
80A 237 82 345 80 132 200 160
8－23
25.5
100A 290 94 412 100 160 225 185
8－23
40.5

7
EPDT-351
3
.
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.
.
Installation
.1 Piping example
* Install a strainer on the inlet side of the pressure reducing valve of nominal size 65A to 100A.
* Make sure that pipes 3m before and after the product, both the inlet side and outlet side, are of the same
diameter.
Outlet side
By-pass
Globe valve
Pressure gauge
Pressure
gauge
afety relief valve
Inlet side
top
valve
GD-28 -NE
Pressure reducing valve
top
valve
Adjusting
screw
Diaphragm
Reduced pressure
detection hole
Disc
pring

8
EPDT-351
.2 Precaution for installation
Warning
1. Please refer to “2. Dimensions and Weights.” for product weight.
* Failure to follow this notice may cause a falling accident of the product, resulting in an injury.
2. When installing a safety relief valve for equipment protection on the
outlet side of the product, connect
a blow-off pipe to the outlet side of the safety relief valve, and lead
it to a place where there is no risk
of physical damage even if fluid blows out.
* Failure to follow this notice may result in injury and scalds
in the event that high temperature fluid
blows out.
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 scales
from the
piping. Keep foreign substances from entering the piping, including seal tape or liquid seal agent for
piping connection.
*Ingress of foreign substances, scales
or seal agent into the product leads to valve leakage or
malfunction of the product.
* Repairs caused by foreign substances or scales will be charged even during the warranty period.
3. If components having a negative influence on internal parts are incl
uded in fluid or surroundings,
deterioration of rubber parts is accelerated and then outside leakage or functional disorder is caused.
4. Be sure to install a strainer on the inlet side of the product of nominal size 65A to 100A.
*Ingress of foreign substances or scales
into the product leads to malfunction of the product. It is
recommended to use a strainer of 60 mesh or more.
5. Install a safety relief valve for equipment protection on the outlet side of the product.
* Failure to follow this notice may result in damage of the equipment.
6. Be sure to install pressure gauges on both inlet and outlet sides of the product.
* Failure to follow this notice hampers correct pressure adjustment.
7.
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.
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.
10.
Make sure that pipes 3m before and after the product, the inlet side and outlet side, are of the same
diameter.
* If the pipe diameter is narrowed immediately before or after the product, the flow velocity may increase
and result in malfunction or a drastically shortened service life of the product.
11. The product can be installed either horizontally or vertically.
12. A space more than the value shown as H2 in the table below is required for disassembly and inspection.
A space more than the value shown as H3 in the table below is required for the inspection of the built-in
strainer (nominal size 20A to 50A).
13. 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.

9
EPDT-351
Model GD-28 -NE, GD-29 -NE
(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
.
Operation procedure
5.1 Precaution for operation
Caution
1. Before leading fluid into the product, close the stop valves on the inlet and outlet sides
of the product
and remove foreign substances and scales 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 scales 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 an
d other equipment due to hunting
or other causes. ee 5.2 Adjusting procedure.
3. If outlet side of the product is closed while fluid is kept
inside the product for an extended period, sliding
parts become stuck and it causes malfunction of the product.
*Check if the product operates normally when resuming the product.
4.
When the product is not used for an extended period, completely discharge fluid from the product and
pipes, and close the stop valves on 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.
5.2 Adjusting procedure
Following a wrong adjusting procedure may cause hunting, scale problems or other problems, 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 on the inlet and outlet sides of the product, 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 that the safety relief valve will not blow out. After finishing blowing, close the globe valve without
fail.
2. After slowly fully opening the stop valve on the inlet side, open the stop valve on the outlet side slightly
so that fluid flows through slightly.
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.

10
EPDT-351
3. Remove the domed cap nut [17] and turn the adjusting screw [14] while watching the pressure gauge
on 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.
*If the pressure is not set under the condition that the stop valve on the outlet side is
slightly opened, closing the stop valve on the outlet side while operation may lead to shut-off
pressure rise exceeding the set pressure.
4. Fully open the stop valve on the outlet side slowly.
5. After the adjustment is complete, tighten the domed cap nut [17]
6
. Maintenance
6.1 Troubleshooting
Trouble Cause Remedy
Reduced pressure
exceeds the
set pressure.
1. Foreign substances are stuck
between disc [8] and valve seat [3],
or either of the parts is damaged.
1. Disassemble the product
and remove
the foreign substances. I
f 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. By-pass globe valve leaks. 4. Repair or replace the by-pass globe
valve.
Reduced pressure
does not reach the
desired value.
1. Working pressure is improper. 1. Correct the working pressure. (
See
“1.1 Specifications”.)
2. Nominal size of the product is too
small for the specifications of the
system.
2. Replace the product with
one of
proper nominal size. (See “1.
2
Nominal size selection”)
3. Pressure adjustment is improper. 3.
Readjust the pressure in accordance
with the given procedure. (See “5
.2
Adjusting procedure”)
4. Strainer [10] built in the product is
clogged.
4. Disassemble and clean it. (See “6
.5
Strainer cleaning procedure”)
5. The strainer installed on the inlet
side of the product is clogged.
5. Clean the strainer.
Outside leakage
1. Bolt [18] or [39] got loose. 1. Tighten the bolts.
2. O-ring [30] is damaged. 2. Replace the O-ring.
3. Strainer cap [11] or plug [31] got
loose.
3. Tighten the strainer cap or plug.
Abnormal sound
1. Nominal size of the product is too
large for the specifications of the
system.
1. Replace the product with one of
proper nominal size.
2. The pressure reduction ratio is too
large or the maximum pressure
difference is exceeded.
2. Reduce pressure in two stages. (
See
“1.1 Specifications”)
3. Air-induced trouble. 3. Install an air vent.
4. An on-off valve is installed near the
product.
5. The pipe diameter is narrowed within
3m before and after the pressure
reducing valve.
4.
Take as large distance as possible
from the on-off valve.
5. Make sure that pipes at least
3m
before and after the pressure reducing
valve are of the same diameter.
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 measure.

11
EPDT-351
6.2 Precaution for maintenance and inspection
Warning
1.
Completely discharge the pressure inside 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 injury or contamination on the surroundings due to the residual
pressure.
2. If the fluid is hot, do not touch the product directly with bare hands.
* Failure to follow this notice may result in scalds or injury.
Caution
1. If problem occurs for a cause other than listed in "6.1 Troubleshooting", please contact us.
2. When the product is disassembled, internal fluid flows out. Receive it in a container.
* Failure to follow this notice may result in making the surroundings dirty.
3.
ynthetic rubber is a consumable part. The replacement interval of the synthetic rubber part greatly
varies depending on the use conditions. The general guide for the replacement interval is shown below.
ervice life Part name, Part No.
Three years Diaphragm [9], O-ring [6], Disc [8]
Five years O-ring [20], [24], [26], [28], [30], [45] seal washer [42]
6.3 Disassembly
1. Remove the domed cap nut [17], turn the adjusting screw [14] counterclockwise to release the
compression of the spring [15] (no load).
2. Remove the bolts [18] of the spring chamber [2] and remove the spring chamber [2]. Then take out
the spring [15] and the spring plate [13].
3. Remove the nut [22], and then the diaphragm retainer [12], and diaphragm [9].
4. Remove the set screws [25] (bolts [25] in the case of nominal size 65A to 100A) of the valve seat [3],
and remove a set of the valve seat (valve seat [3], spindle [4], disc [8], and O-ring [28]).
Nominal size 20A to 50A: Attach the diaphragm retainer [12] to the spindle [4], and pull it up.
Nominal size 65A to 100A: crew the bolt into the valve seat [3], and pull it up.

12
EPDT-351
U-nut
Part A
Washer of disc
O-ring
Disc cover
D
isc
(5) ecure the part A of the spindle [4] (two faces), loosen the U-nut [29] with a tool, and remove the disc
[8], and O-ring [28].
6. Precaution for reassembly
Caution
1. Check that there are no foreign substances inside the body and on each part.
*Foreign substances prevent the product from functioning properly.
To avoid the problem, remove
foreign substances.
2. Check that there is no damage or scratch on the disc or O-ring.
*Damage or scratch on the relevant part prevents the product from functioning properly.
Replace the
damaged part.
3. Apply silicone grease (harmless to humans) to the O-ring.
*Failure to follow this notice may damage the O-ring.
Assemble the parts in reverse order of disassembly.
Tighten the bolts [18] of the spring chamber [2] evenly in the diagonal order.
*Bolt [18] of Spring chamber [2] Tightening torque
Size Torque
20 - 50A 10N・m
65 ‐ 100A 30N・m
* Nut [22] of Diaphragm [9] Tightening torque
Size Torque
20 - 25A 8N・ｍ
32 - 50A 12N・ｍ
65 - 80A 18N・ｍ
100A 23N・ｍ
* et screws [25] (bolts [25] in the case of nominal size 65A to 100A) of the valve seat [3]
Tightening torque
Size Torque
20 - 50A 15N・ｍ
65 - 100A 30N・ｍ
*U-nut [29] of spindle [4] Tightening torque （※Replace the U-nut.）
Size Torque
20 - 25A 8N・ｍ
32 - 40A 12N・ｍ
50A 13N・ｍ
65 - 80A 18N・ｍ
100A 23N・ｍ
*Strainer cap [11] Tightening torque
Size Torque
20 - 25A 40N・ｍ
32 - 50A 80N・ｍ

13
EPDT-351
6.5 Strainer cleaning procedure
Warning
1. If fluid is hot, do not touch the product directly with bare hands.
* Failure to follow this notice may result in scalds.
Caution
1. Clean the strainer regularly at least once or twice a year.
*
Too much deposit of scales or the like decreases the flow rate, which prevents the product from
functioning properly.
2. When the strainer cap is removed, receive fluid in a container. ( ee the Figure below.)
1. Close the stop valve on the inlet side and open the stop valve at the end, and discharge the internal
pressure from the product completely.
2. Turn the strainer cap counterclockwise, and remove it.
3. Remove the strainer from the strainer cap, and wash it in water, and remove deposited scale.
4. After cleaning, assemble the strainer and strainer cap to the body.
5. Open the stop valve on the inlet side, and check that there is no leakage from the strainer cap. When
there is a leakage, replace the O-ring.
6. Open the stop valve at the end, and check that the product operates normally.
Container
O-ring
trainer
trainer cap

14
EPDT-351
7
.
Exploded view
GD-28 -NE, GD-29 -NE
Nominal size 20A - 50A
Note) The parts shown in the rectangle boxes are available as consumable supply.
Washer of disc

15
EPDT-351
GD-29 -NE
Nominal size 65A - 100A
Note) The parts shown in the rectangle boxes are available as consumable supply.