Yoshitake GDK-2000 Manuale utente

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

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.

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)

Weight

(kg)

Weight

(kg)

15A

Rc 1/2

150

244

200

12.4

146

244

200

13.9

20A

Rc 3/4

150

244

200

12.4

146

244

200

14.4

25A

Rc 1

160

251

226

16.4

156

251

226

19.2

32A

Rc 1-1/4

180

282

226

19.9

176

282

226

22.4

40A

Rc 1-1/2

180

282

226

19.9

196

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.

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

Body

Main valve

Main valve seat

Main diaphragm

Main valve spring

Main diaphragm chamber

Reduced pressure sensing port

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)

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)

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)

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).

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.

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.

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

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

)PP(P138

Cv 21 +

2

1120P

Cv =

2)7.0(

)5.0( 1

= P

PPPCv

W)(138 21 +

)5.07.0(2.00.5138 +

hkg/338=

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