Yoshitake GD-6 is a direct-acting diaphragm pressure reducing valve designed for cold and hot water, oil, air, and other non-dangerous fluids. It features highly accurate controllability of reduced pressure even at small flow rates.

Features

1. High accurate controllability of reduced pressure even at small flow rate.
2. Simple in structure, less prone to fail and easy to maintain.
3. Compact and lightweight.

Specifications

Model	GD-6
Application	Cold and hot water, Oil, Air, Other non-dangerous fluids
Inlet pressure	0.1-1.0 MPa
Reduced pressure	(A) 0.02-0.1 MPa (Nameplate color: yellow) (B) 0.1-0.4 MPa (Nameplate color: blue)
Minimum differential pressure	0.05 MPa
Maximum pressure reduction ratio	10:1
Application temperature	5-80℃
Valve seat leakage	None
Fluid viscosity	300 cSt or less
Body Material	Ductile cast iron *1
Valve, valve seat Material	Brass and bronze (FKM disc incorporated) *2
Diaphragm Material	Stainless steel
Connection	JIS Rc screwed

*1 Available with stainless steel wetted parts and all stainless steel made on request. *2 Available with stainless steel made valve disc and valve seat on request. Also available with PTFE disc on request. Available with anticorrosive (fluororesin-coated) type on request.

Dimensions and Weights

Nominal size	d	L	H	H1	E	Weight (kg)
10A	Rc 3/8	165	243	57	155	5.5
15A	Rc 1/2	165	243	57	155	5.5
20A	Rc 3/4	185	267	76	175	8.2
25A	Rc 1	185	267	76	175	8.2

Characteristics

Flow Characteristic Chart

Pressure Characteristic Chart

This chart shows variation in reduced pressure when the inlet pressure of 0.3 MPa is changed between 0.3 MPa and 1.0 MPa while the reduced pressure is set at 0.2 MPa.

Nominal Sizes Selection

For Water

For Air

• Set the safety factor at 80 to 90%.

Operation

When the adjusting screw [15] is screwed in, the adjusting spring [17] is compressed, which lowers the diaphragm [19] and opens the valve assembly to allow the fluid to flow to the secondary side. When the secondary side pressure increases or decreases, the diaphragm [19] and adjustment spring [17] balance, adjust the valve opening, and maintain the secondary side pressure constant.

Installation

Example of Piping

For Air

For Water

Precautions Before Operation

• Depending on the water quality, brass parts may corrode or be promoted, causing product malfunction. In an environment where corrosion may occur, select a product made of a compatible material such as stainless steel.
• If components having negative influence on internal parts are included in fluid or surroundings, deterioration of rubber parts is accelerated and then outside leakage or functional disorder is caused.
• The product or parts will be damaged if an impact due to sudden pressure fluctuations such as water hammer is applied.
• If the product is in a closed pipe state, the fluid in the pipe will expand in volume due to the rise in fluid temperature, and the product will be damaged.
• Sticky fluids can cause parts to stick together and cause malfunctions.
• Do not disassemble the valve unreasonably.
• Remove foreign matter and scales from the lines before connecting the valve.
• Install a strainer at the valve inlet side.
• Install a safety valve at the valve outlet sides for alarms.
• Install a pressure gauge at both the inlet and outlet sides of the valve.
• For gas application, install a trap to the inlet sides of the valve to prevent drainage problem.
• When installing quick open and close valves, such as a solenoid valve, secure at least 3 m from the valve.
• When reducing pressure in two stages, secure at least 3 m between the valves.
• Do not apply excessive load, torque or vibration to the valve.
• Install the valve in proper direction of the fluid flow. Also, install the product so that it faces vertically upward with respect to horizontal piping.
• Do not use dissimilar metal piping that causes a potential difference.
• If the large valve is used for gas, install a reducer to prevent excessive flow speed. (The flow speed made in piping is appropriate, if it is 15m/s or less.)

Maintenance Space

In order to have easy maintenance, be sure to have enough space for inspection.

• 10A, 15A: A=120mm, B=100mm
• 20A, 25A: A=130mm, B=130mm

Adjustment Procedure

Warning

Do not touch the valve directly with bare hands. Doing so may result in burns.

1. Close the stop valves at both sides of the pressure reducing valve, and thoroughly purge the system through the by-pass line, with the by-pass valve opening adjusted so that the safety relief valve is not activated. When completed, be sure to close the by-pass valve.
2. Slowly open the inlet stop valve, then open the outlet stop valve slightly, allowing a trickle to be discharged.
3. Loosen the lock nut [16], and slowly turn the adjusting screw [15] (clockwise to increase, counterclockwise to reduce) while observing the pressure gauge on the outlet side.
4. Slowly open the outlet stop valve to its full-open position.
5. After the adjustment, tighten the lock nut [16].

Maintenance and Troubleshooting

Problem	Causes	Solutions
Pressure does not rise to desired level.	1. Incorrect pressure is being used. 2. Nominal size is too small. 3. Incorrect adjustment. 4. Strainer is clogged. 5. Pressure gauge malfunction. 6. Reduced pressure sensing port is clogged.	1. Correct the pressure. 2. Replace with the correct size. 3. Re-adjust. 4. Disassemble and clean. 5. Replace the pressure gauge. 6. Disassemble and clean.
Reduced pressure exceeds prescribed level.	1. Foreign matter is embedded in valve/seat, or scratches exist. 2. By-pass valve is leaking.	1. Disassemble and clean. If scratches exist, replace them. 2. Repair or replace the valve.
External leakage	1. Diaphragm is broken. 2. Gasket is broken.	1. Replace the diaphragm. 2. Replace the gasket.
Abnormal noise is heard.	1. Nominal size is too large. 2. Pressure reduction ratio is too large. 3. Air problem is caused (Liquid use). 4. An abrupt OPEN/CLOSE valve is too close.	1. Replace with correct size. 2. Use a two-stage reduction. 3. Install an air trap. 4. Keep distance at least 3m.

Consumables Replacement

• 3 years: Disc [9], O ring [27]
• 5 years: Disc [9] is replaced as a valve assembly.