Yoshitake GDK-2000 User manual

EPDT-021a
MODEL GDK-2000
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 references.
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. Specifications···························································1-2
2. Dimensions and Weights·············································2
3. Operation································································3-5
4. Nominal Size Selection method
4.1 Pressure reducing valve specification selection chart ···6
4.2 Safety valve setting pressure chart···························6
4.3 Characteristic chart ·············································7
4.4 Nominal size selection chart ··································8
4.5 Nominal size selection calculation formula ·················9
5. Installation
5.1 Precaution for installation·····································10
5.2 Installing accessories··········································10
5.3 Piping before and after the pressure reducing valve···11
5.4 Piping example··················································12
6. Operation procedure
6.1 Precaution for operation ······································13
6.2 Adjusting procedure············································13
7. Maintenance Procedure
7.1 Troubleshooting·················································14
7.2 Precaution for maintenance and inspection··············15
7.3 Disassembly·····················································15
7.4 Precaution for reassembly····································15
7.5 Exploded drawing ··············································16
Warranty Information

1
EPDT-021a
1. Specifications
Model
GDK-2000
Connection
Screwed
Flanged
JIS Rc
JIS 20K RF
JIS 10K FF
Nominal size
15 ~ 50A
15 ~ 100A
Application
Steam
Inlet pressure
0.1 ~ 2.0 MPa
0.1 ~ 1.0 MPa
Reduced pressure (*)
0.05 ~ 1.4 MPa
0.05 ~ 0.9 MPa
90% or less of Inlet pressure (gauge pressure)
Min. differential pressure
0.05 MPa
Max. pressure reducing ratio
10:1
Max. temperature
220 °C
Valve seat leakage
0.01% or less of rated flow
Material
Body
Ductile Cast Iron
Main valve
Stainless Steel
Main valve seat
Stainless Steel
Main diaphragm
Stainless Steel
(*) Refer to “Standard Loading Pressure - Setting Pressure Chart Lines”for system air pressure.
Caution
Please confirm that the indications on the product correspond with the
specifications of the ordered product model before use.
* If they are different, please contact us without using the product.
[Standard Loading Pressure - Setting Pressure Chart Lines]
The setting pressures corresponding to the loading pressures are shown below. As slight deviations
from the “loading pressure - setting pressure” chart lines shown below may occur depending on
conditions such as the length of the air line, etc., a setting pressure which is high enough to cover such
deviations should be selected.

2
EPDT-021a
[Screwed]
[Flanged]
* Explanation of Chart Lines
For a nominal size of 25A, the loading pressure for an inlet pressure [P1] of 1.0MPa and a reduced
pressure[P2] of 0.2MPa can be obtained as follows: Find point[A] where a vertical line drawn upward
from the valve’s inlet/reduced pressure differential (ΔP) (1.0 - 0.2 = 0.8MPa) intersects the 25A
nominal size line. Next draw a horizontal line from point[A] to the left border of the chart to obtain the
ΔPα (loading pressure[Pα] - set pressure[P2]) = 0.037MPa value. The loading pressure can then be
calculated as follows: Loading pressure[Pα] = ΔPα+ P2 = 0.037 + 0.2 = 0.237MPa.
2. Dimensions and Weights
The structure differs for nominal sizes 65A to 100A.
(mm)
Nominal
size
Screwed (JIS Rc)
Flanged (JIS 20K RF)
d
L
H1
H
A
Weight
(kg)
L
H1
H
A
Weight
(kg)
15A
Rc 1/2
150
74
244
200
12.4
146
74
244
200
13.9
20A
Rc 3/4
150
74
244
200
12.4
146
74
244
200
14.4
25A
Rc 1
160
76
251
226
16.4
156
76
251
226
19.2
32A
Rc 1-1/4
180
90
282
226
19.9
176
90
282
226
22.4
40A
Rc 1-1/2
180
90
282
226
19.9
196
90
282
226
22.9
50A
Rc 2
230
103
319
276
30.5
222
103
319
276
33.5
65A
------
-----
-----
-----
-----
-----
282
122
373
352
61.8
80A
------
-----
-----
-----
-----
-----
302
135
399
352
69.1
100A
------
-----
-----
-----
-----
-----
342
167
488
401
108.6
● Different Length(L) and Weight values apply for JIS 10K FF.
● Other standard connections are available upon request.

3
EPDT-021a
Fig.1
3. Operation
The pressure reducing valve reduces pressure by the throttling the valve. The valve is composed of
the main valve, main valve seat, a pressure adjusting air chamber, and a main diaphragm for
pressure sensing and activation.
No.
Parts name
1
Body
5
Main valve
6
Main valve seat
11
Main diaphragm
12
Main valve spring
31
Main diaphragm chamber
32
Reduced pressure sensing port
33
Air pressure control space
(1) When the pressure reducing valve is mounted correctly, the main valve [5] should be closed by the
main valve spring [12] when a no-pressure condition is made by a standard control unit, etc. When
the inlet gate valve is gradually opened, allowing the high-pressure fluid to flow in, the inlet pressure
will be applied to the back side of the main valve. (Fig. 1)

4
EPDT-021a
Fig.2
Air pressure
Fig.3
Air pressure
(2) When air pressure is introduced into the air pressure control space [33] by a standard control unit,
etc., main diaphragm [11] will bend and when it overcomes both the pressure against the back of
the main valve, and the load of the main valve spring, thereby pushing the main valve open. The
fluid then begins to flow from the inlet side to the reduced pressure side. (Fig. 2)
(3) The flow of pressure proceeds from the reduced pressure sensing pipe through the reduced
pressure sensing port [32], and into the main diaphragm chamber [31]. The diaphragm then
balances the operating pressure with the reduced pressure. The amount of reduced pressure
applied to the diaphragm and operating pressure act on each other to maintain an appropriate
reduced pressure by controlling the main valve’s opening. (Fig. 3)

5
EPDT-021a
Fig.4
Air pressure
(4) In the absence of a reduced pressure load, the pressure in the diaphragm chamber increases,
thereby pushing the main valve spring to close the valve. (Fig. 4)

6
EPDT-021a
4. Nominal size selection method
4.1 Pressure reducing valve specification selection chart
To select the most appropriate pressure reducing valve, refer to the above selection chart. Find the
intersection point of the inlet pressure (P1) and the reduced pressure (P2). If the intersection point is
within the range (A), two-stage pressure reduction is required. In this case, maximize the distance
between the valves (at least 3 meters). The valve does not fulfill specified performance in the range
(C).
4.2 Safety valve setting pressure chart
Determine the reduced pressure of pressure reducing valve. Find the intersection point (A) with the
chart curve. Next, find point (B) by proceeds horizontally from point (A) to the left until the ‘Setting
pressure of safety valve’ axis. The setting pressure of the safety valve should be higher than the
pressure of the point (B).

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EPDT-021a
4.3 Characteristic chart
(1) Flow rate characteristics chart
● Shut-off pressure rise: 0.02 MPa or less
● Offset: 10% or less of set pressure at outlet side (Minimum value: 0.05MPa)
(2) Pressure characteristics chart
This chart shows variation in reduced pressure when the inlet pressure of 1.4 MPa is changed
between 0.2 MPa and 1.4 MPa while the reduced pressure is set at 0.14 MPa.

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EPDT-021a
4.4 Nominal size selection chart
[Example]
When selecting the nominal size of a pressure reducing valve with its inlet pressure (P1) is 0.6
MPa, its reduced pressure (P2) is 0.4 MPa and its steam flow rate is 600 kg/h, first find the
intersection point (a) of inlet pressure 0.6 MPa and reduced pressure 0.4 MPa. Trace down
vertically from this intersection point (a) to find intersection point (b) with the flow rate of 600 kg/h.
Since the intersection point (b) is between nominal sizes 20A and 25A, select the larger one, 25A.

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EPDT-021a
4.5 Nominal size selection calculation formula
An appropriate nominal size can be calculated by obtaining Cv value for the operating conditions
in question, as shown below.
•Calculation formula for Cv value
● Rated Cv value table
Nominal size
15A
20A
25A
32A
40A
50A
65A
80A
100A
Cv value
5.0
7.2
10.9
14.3
18.8
32
54
70
108
[Example]
The flow rate of the pressure reducing valve is calculated under the following conditions: Nominal
size 15A, saturated steam, Inlet pressure of 0.6 MPa = 0.7 [MPa A], Reduced pressure of 0.4 MPa
= 0.5 [MPa A], you can find that Cv value of 15A is 5.0 from the chart. The following formula is
established.
* Use a safety factor of 80 to 90% for nominal size selection in view of friction losses in piping.
W: Max. steam flow rate [kg/h]
P1: Inlet pressure [MPa･A]
P2: Reduced pressure [MPa･A]
ΔP: P1 - P2 [MPa]
k: 1+0.0013× {superheated steam
temp.[°C] - saturated
steam temp. [ °C]}
2
P
P1 2
)PP(P138
Wk
Cv 21 + =
2
P
P1 2
1120P
Wk
Cv =
2)7.0(
)5.0( 1 2= = P P
k
PPPCv
W)(138 21 + =
1
)5.07.0(2.00.5138 +
=
hkg/338=