Yoshitake GD-21 User manual

EPDT-255b
MODEL GD-21
Differential Pressure Regulating 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. Usage ofthe product ·················································· 1
2. Features·································································· 1
3. Specifications···························································· 1
4. Dimensions and Weight ·············································· 2
5. Operation································································· 3
6. Nominal Size Selection··············································· 4
6.1 Nominal sizes selection chart·································· 4
6.2 Calculation formula for Cv value······························ 4
7. Installation································································ 5
7.1 Precautions for installation ····································· 5
7.2 Piping example···················································· 6
8. Operating Procedure·················································· 7
8.1 Precautions for operation······································· 7
8.2 Precautions for air vent ········································· 7
8.3 How to use air vent··············································· 7
9. Maintenance····························································· 7
9.1 Precautions for disassembly and maintenance··········· 7
9.2 Disassembly······················································· 8
9.3 Reassembly························································ 8
9.4 Precautions for reassembly···································· 9
10. Troubleshooting······················································· 9
11. Exploded Drawing···················································10
Warranty Information

EPDT-255b
1
1. Usage of the Product
The GD-21 is used for pump in a closed circuit of air-conditioning or heating equipment in mid-rise and
high-rise buildings. While an open circuit requires a primary pressure reducing valve as relief valve for pump,
a closed circuit requires a differential pressure regulating valve since it is necessary to operate the pump at a
constant flow rate no matter how back pressure fluctuates.
2. Features
1. The product is the most suitable for pump in a closed circuit.
2. Since the main valve features a single-seat valve and a disc, leakage is prevented when closed.
3. Specifications
Model GD-21
Application Cold and hot water
Nominal size 15A-80A 100A-150A
Regulating differential pressure
(A) 0.05-0.25 MPa
(B) 0.26-0.7 MPa (A) 0.05-0.25 MPa (B) 0.26-0.5 MPa
Fluid temperature 5-80˚C
Material
Body Ductile cast iron
Valve seat Stainless Steel or Bronze
Valve disc NBR
Diaphragm NBR
Connection JIS 10K FF Flanged
Inside surface treatment of body Electrodeposition coating
Caution
Please confirm that the indications on the product correspond with the
specifications of the ordered model before use.
* If they are different, do not use the product and contact us.
■Flow rate characteristics chart
* Accumulation
Set range (MPa) Accumulation (MPa)
0.05-0.25 0.05 or below
0.26-0.7 0.105 or below
* Accumulation
Adjusteddifferentialpressure
Flow rate
Differential pressure to
determine rated flow
Rated flow rate
Shut-off pressure drop 10%
of set pressure (gauge pressure)
(Min. value 0.02 MPa)
Min.adjustableflowrate
Set differential pressure

EPDT-255b
2
4. Dimensions and Weight
(mm)
Nominal size L H H1b Weight (kg)
15A 145 298 57 36 8.3
20A 150 298 57 36 8.3
25A 150 320 67 36 10.1
32A 195 400 76 48 17.4
40A 195 400 76 48 17.4
50A 195 414 81 48 19.3
65A 270 572 110 63 40.1
80A 270 597 125 63 43.8
100A 308 665 143 68 70.1
125A 380 866 179 115 144.1
150A 400 936 204 115 173.1

EPDT-255b
3
5. Operation
Size 15A-50A
No. Parts Name
1 Body
2 Spring Chamber
3 Retainer
4 Retainer Guide
5 Spindle
6 Valve Seat
7 Valve
8 Diaphragm
9 Spring Plate
10 Spring Plate
11 Adjusting Spring
12 Adjusting Screw
13 Lock Nut
14 Cap
15 U Nut
16 Conductor Pipe
17 Air Vent
18 Bolt
19 Bolt
20 O Ring
•The shapes differentiate slightly depending on the nominal size.
When fluid flows into the product, the inlet pressure is applied to the bottom side of the
diaphragm [8] via the conductor pipe [16] and the outlet pressure is applied to the top side of
the diaphragm [8] via outlet pressure sensing port.
The product is kept closed while the pressure difference between before and after the product
is less than the set pressure.
When the pressure difference goes over the set pressure, the load of the differential pressure
between the top and bottom sides of the diaphragm [8] overcomes the load of the adjusting
spring [11] to lift up the valve [7] apart from the valve seat [6], opening the product.
When the pressure difference falls below the set pressure, the product closes again so that
the pressure difference between before and after the product can be kept at constant level.
Outlet pressure
sensing port Rc 3/8

EPDT-255b
4
6. Nominal Size Selection
6.1 Nominal size selection chart (For water)
[Example]
When selecting the nominal size of a differential pressure regulating valve with differential pressure (P) of
0.2 MPa and flow rate (V) of 5.5 m3/h, find the intersection point (a) of differential pressure (P) and the flow
rate (V).
Since the intersection (a) lies between nominal sizes 25A and 32A, select the larger one, 32A.
6.2 Calculation formula for Cv value
■ Cv value
Nominal size 15A 20A 25A 32A 40A 50A 65A 80A 100A 125A 150A
Cv value 1.5 2.7 4 8.5 11 14 23 32.5 48 75 108
■ Calculation formula for Cv value
P1: Inlet pressure [MPa･A]
P2: Outlet pressure [MPa･A]
P: P1- P2[MPa]
G : Specific gravity (relative to water)
V : Max. liquid flow rate [m3/h]
Cv : Cv value of each nominal size
P: Differential pressure (MPa)
Nominal size
V: Flow rate (m
3
/h)
V: Flow rate (m
3
/h)
(a)
PGV365.0
Cv ∆ =

EPDT-255b
5
7. Installation
7.1 Precautions for installation
Caution
1. As the product is heavy, support it securely by lifting device while installation.
* Failure to follow this notice may result in bodily injury due to a drop accident.
2. Do not disassemble the product unless it is necessary.
* Disassembly may prevent the product from functioning properly.
3. Be sure to remove foreign substances and scales from the piping before connecting the product.
* Foreign substances and scales may prevent the product from functioning properly.
4. Install the product vertically to the horizontal piping. If installing it to a vertical piping is inevitable
due to limited space, the product can be installed to the vertical piping as long as its size is less
than 100A.
* Do not install the product of 100A or larger to a vertical piping.
5. Be sure to install pressure gauges to both the inlet and outlet sides of the product. In addition,
install strainer and bypass line to the piping around the product.
* Failure to follow this notice may hamper correct pressure adjustment.
6. Be sure to install a strainer (60-80 mesh) at the inlet side of the product.
* Foreign substances or scales may prevent the product from functioning properly.
7. Quick operating valve shall be installed more than 3 meters away from the product.
* Failure to follow this notice may result in malfunction or a drastically shortened service life of the
product.
8. Do not apply excessive load, torque or vibration to the valve when piping.
* Failure to follow this notice may result in malfunction or a drastically shortened service life of the
product.
9. Place a drain pipe between the stop valve and the product for easier maintenance and
inspections.
* Failure to follow this notice may cause fluid spill when disassembling.
* Guide the drain pipe to a drain ditch if there is a risk of contamination on the surroundings due to
the fluid spill.
10. Install a needle valve to the outlet side of the product and plumb it to the pressure sensing pipe
using copper piping.
* Failure to follow this instruction hampers correct pressure adjustment.
(1) Joint for the outlet pressure sensing is not included with the product package.
(2) Secure the space specified in the table below (H2) since it is required for maintenance and inspection.
H2indicates the required height above the horizontal center line of the piping (see Fig. 1 below).
■ Space required for disassembly (mm)
Nominal size 15A 20A 25A 32A 40A 50A 65A 80A 100A 125A 150A
H2500 500 500 650 650 650 800 800 1000 1200 1400
Fig. 1 Space required for disassembly

EPDT-255b
6
Two-way
valve
Two-way
valve
Air-conditioning
equipment
Air-conditioning
equipment
Pump Freezer or
heat source
Supply
header
Return
header
SU-20
Strainer
GD-21
SU-20
Strainer
Needle
valve*
Approx. 1000 mm
Outlet pressure
sensing port Rc 3/8
* Install a needle valve to the outlet side of the
product and plumb it to the pressure sensing
pipe using copper piping
7.2 Piping example
Fig. 2
Fig. 3

EPDT-255b
7
8. Operating procedure
8.1 Precautions for operation
Warning
Do not touch the product with bare hands when the fluid has a high-temperature.
* Failure to this notice may scald your skin.
Caution
1. Before leading fluid into the product, close the stop valves before and after the product and
remove all foreign substances or scales via the bypass line.
* Foreign substance or scales may prevent the product from functioning properly.
2. Before leaving the product not operated for a long time, discharge the fluid inside of the product
and piping completely, and close the stop valves before and after the product.
* Failure to follow this notice may cause malfunction due to rust generated inside the product and
piping, or result in damage due to freezing.
* The fluid can be drained out of the product efficiently with the air vent valve (see “8.2 Precaution
for air vent”).
3. Pressure regulation of the product shall be performed while the fluid running. To increase the set
differential pressure, loosen the lock nut [13], and then slowly turn the adjusting screw [12]
clockwise. To decrease the set differential pressure, slowly turn the adjusting screw [12]
counterclockwise.
* The fluid leaks if the cap [14] is removed. In this case, use a waste cloth to wipe it out.
4. Remove air accumulated in top and bottom sides of diaphragm using the air vents in accordance
with the procedures described in “8.3 How to use air vent.”
* Air accumulated in the top and bottom sides of the diaphragm may cause malfunction of the
product.
8.2 Precautions for air vent
Warning
Do not stand in front of the air vent valve during use.
* Failure to follow this notice may result in scalds or bodily injury due to blow-off of
the fluid inside.
Caution
Do not rotate the air vents more than 1/2 turn when use.
* Failure to follow this notice may make the air vents detached from the body. In this
case, the air vents may not be reattached.
8.3 How to use air vent
(1) Rotate the screw of the air vent [17] counterclockwise to loosen it in order to discharge air.
(2) Rotate the screw of the air vent [17] clockwise to the original closed position after discharging air.
9. Maintenance
9.1 Precautions for disassembly and maintenance
Warning
1. Disassembling and inspections must be performed by experienced professional or valve manufacturer.
2. Before disassembly or inspection, completely release internal pressure of the product, piping and
equipment. When the fluid is hot, cool down the product to the condition that it can be touched with bare
hands.
* Residual pressure may cause bodily injury or scalds and may contaminate surroundings of the
product.

EPDT-255b
8
U nut
[15]
Spring plate [9]
Spindle [5]
Bolt [18]
Retainer guide [4]
9.2 Disassembly
(1) Release the internal pressure from the piping completely, and make sure that the pressure gauge
shows that the pressure is zero.
(2) Remove the cap [14] and slightly loosen the lock nut [13], and then turn the adjusting screw [12]
counterclockwise so that the adjusting spring [11] can be in no load condition.
(3) Remove the spring chamber [2] by unscrewing the bolt [19], and then take out the adjusting spring
[11] and the spring plate [10].
(4) Remove the diaphragm [8] by fixing the spindle [5] and loosening the U nut [15].
(5) To remove the retainer [3], by loosening the bolt [18] and pulling out the retainer guide [4] together
with the retainer [3].
If the retainer guide [4] is difficult to be removed, do as indicated in Fig. 4 or Fig. 5 below
Nominal size 15-50A
To remove the retainer guide [4] easily, reattach the spring plate [9] and U nut [15] to the spindle [5], then
pull up the spring plate [9].
Fig. 4
Nominal size 65-150A
To remove the retainer guide [4] easily, screw the bolt [18] to the retainer guide [4] and pull them out. (See
Fig. 5)
Fig. 5
9.3 Reassembly
To reassemble the product, take reverse procedure to disassembly.

EPDT-255b
9
9.4 Precautions for reassembly
Caution
1. Make sure that there are no flaws on the diaphragm [8], the valve seat [6] and the valve [7].
* Flaws on them may prevent the product from functioning properly.
2. Apply silicon grease to the O-ring [20] after confirming that there are no flaws on it.
* Without silicon grease, the O-ring may be torn.
3. Confirm that the lip of the diaphragm [8] is fitted in the grooves on the body [1], and then attach the
spring chamber [2].
* Failure to follow this notice may prevent the product from functioning properly.
4. There should be a gap between the retainer guide [4] and the body [1] when properly assembled.
Tighten the bolts evenly to avoid over-tightening them.
10. Troubleshooting
Trouble Cause Remedy
Excessive leakage
Adjustment is
impossible.
1.
Foreign substances stuck
between valve [7] and valve seat
[6]. Or damage on valve [7]
and/or valve seat [6].
1.
Disassemble and clean, or replace.
2.
Damage on diaphragm [8]
and/or O
-
ring.
2.
Replace diaphragm [8] and/or O
-
ring
[20]
.
3.
Nominal size i
s too small for the
specifications.
3.
Replace the product
to obtain proper
nominal size (see “6.1 Nominal size
selection chart
”
).
4.
Pressure gauge is out of order.
4.
Replace.
Abnormal
sound is
observed
1.
Air
-
induced problem occurs.
1.
Install
exhaust equipment.
2.
Nominal size is too large for the
specifications.
2.
Replace the product
to
obtain
proper
nominal size (see “6.1 Nominal size
selection chart”).

EPDT-255b
10
Adjusting
screw
L
ock nut
Bolt
Spring chamber
Name plate
Rivet
O ring
Spring plate
Spring
U nut
Disc spring
Spring plate
Diaphragm
Retainer
O ring
O ring
O ring
O ring
Retainer
Bolt
O ring
O ring
Bolt
Retainer guide
Retainer guide
15A – 50A 65A – 150A
Spindle
Valve cover
Valve
O ring
O ring
O ring
Washer of disc
U nut
Valve seat
Body
O ring Joint A
Pipe
Joint B
Spindle guide
Air vent
Cap
O ring
Conductor pipe
65A – 150A
Needle valve
Cover gaske
Cover
Bolt
15A – 50A 65A –
150A
Air vent
Conductor pipe
15A – 50A
A
i
r vent
Cap
Gasket
11. Exploded Drawing
The parts name shown in the rectangle boxes are available as consumable supply.

2015.8
PDD-046e
Warranty Information
1. Limited warranty
This product has been manufactured using highly-advanced techniques and subjected to
strict quality control. Please be sure to use the product in accordance with instructions on
the manual and the label attached to it.
Yoshitake warrants the product to be free from any defects in material and workmanship
under normal usage for a period of one year from the date of receipt by the original user, but
no longer than 24 months from the date of shipment from Yoshitake’s factory.
2. Parts supply after product discontinuation
This product may be subject to discontinuation or change for improvement without any prior
notice. After the discontinuation of the product, Yoshitake supplies the repair parts for 5
years otherwise individually agreed.
3. This warranty does not cover the damage due to any of below:
(1) Valve seat leakage or malfunction caused by foreign substances inside piping.
(2) Improper handling or misuse.
(3) Improper supply conditions such as abnormal water pressure/quality.
(4) Water scale or freezing.
(5) Trouble with power/air supply.
(6) Any alteration made by other than Yoshitake.
(7) Use under severe conditions deviating from the design specifications
( e.g. in case of corrosion due to outdoor use).
(8) Fire, flood, earthquake, thunder and other natural disasters.
(9) Consumable parts such as O-ring, gasket, diaphragm and etc.
Yoshitake is not liable for any damage or loss caused by malfunction or defect of the product.
INTERNATIONAL DEPT.
955-5, Miyamae, Irukadeshinden, Komaki, Aichi, 485-0084, Japan
Phone: [phone] Fax: [phone]
E-mail: [e-mail]