Yoshitake GD-30S and GD-30 are direct-acting pressure reducing valves designed for steam applications. The GD-30S model features a cast stainless steel (SCS14A) body, making it highly durable for steam lines up to 2.0 MPa inlet pressure. Both models incorporate a pressure sensing part with an external pressure type bellows, ensuring excellent workability and stable pressure reduction.

Features

• Sophisticated design, compact and lightweight.
• Simple structure, great durability, and easy maintenance.
• Easy to install due to screwed connections.
• Pressure adjustment is handle-operated without any tool.
• Highly wear-resistance and durability of stainless steel made valve and valve seat.
• A screen (60 mesh) is incorporated to protect the valve and valve seat from dirt.
• Excellent workability accomplished by the external pressure type bellows of pressure sensing part.

Specifications

Model	GD-30	GD-30S
Nominal size	15A-25A, 40A-50A	15A-25A
Application	Steam	Steam
Inlet pressure	1.7 MPa or less	2.0 MPa or less
Reduced pressure	(A) 0.02-0.1 MPa (yellow spring) (B) 0.05-0.4 MPa (blue spring) (C) 0.35-1.0 MPa (yellow-green spring)	(A) 0.02-0.1 MPa (yellow spring) (B) 0.05-0.4 MPa (blue spring) (C) 0.35-1.0 MPa (yellow-green spring)
Minimum differential pressure	0.05 MPa	0.05 MPa
Maximum pressure reduction ratio	10:1	10:1
Maximum temperature	210°C	220°C
Valve seat leakage	0.1% or less of rated flow rate	0.1% or less of rated flow rate
Body material	Cast bronze	Cast stainless steel (SCS14A)
Valve, valve seat material	Stainless steel	Stainless steel
Bellows material	Phosphor bronze	Stainless steel
Connection	JIS Rc screwed	JIS Rc screwed

Note

For GD-30S sizes 15A, 20A, and 25A, connections are available in JIS Rc Screwed, NPT Screwed, and BSPT Screwed.

Dimensions and Weights

Nominal size	d	L	H1	H	Weight (kg)
15A	Rc 1/2, NPT 1/2, BSPT 1/2	80	47 (50.5)	191 (196)	1.9
20A	Rc 3/4, NPT 3/4, BSPT 3/4	85	47 (50.5)	191 (196)	1.9
25A	Rc 1, NPT 1, BSPT 1	95	47 (50.5)	191 (196)	2.0
40A	Rc 1-1/2	140	77	307	10.1
50A	Rc 2	150	77	307	10.4

• The values in parentheses are the dimensions of the GD-30S. 40A and 50A are only available for GD-30.

Operation

When the adjusting screw connected to the handle pushes the adjusting spring, the bellows are extended and the spindle opens the valve. When the valve opens, the steam flowing to the outlet side passes through the reduced pressure detection hole, and becomes an upwardly directed pressure under the bellows and balances the force of the adjusting spring. The degree of valve opening is adjusted by the balancing of inlet and reduced pressures, thereby stabilizing reduced pressure.

Nominal Sizes Selection Chart (For Steam)

40A and 50A have different structures. W: Flow rate kg/h.

Example: When selecting the nominal size of a pressure reducing valve whose inlet pressure (P1), reduced pressure (P2), and flow rate are 1.3 MPa, 0.6 MPa, and 200 kg/h, respectively, first find the intersection point of the inlet pressure of 1.3 MPa and the reduced pressure of 0.6 MPa. Trace down vertically from this intersection point to find the nominal size with a flow rate of 200 kg/h or over. In this case, the nominal size is 20A.

Safety Factor

Set the safety factor at 80 to 90%.

Installation

Example of Piping

Precautions During Installation

Installation Warnings

In case installing a safety valve as a safety device at the outlet side, joint relief pipe at the outlet of the safety valve and guide it to a safety place where steam can relief out. Failure to do so may result in burns.

• Do not disassemble the valve unreasonably.
• Remove foreign matter and scales from the lines before connecting the valve.
• Install a strainer (80 mesh) at the valve inlet side.
• Install a safety valve at the valve outlet sides as a safety device for equipment.
• Install a pressure gauge at both the inlet and outlet sides of the valve.
• Install a steam trap to the inlet sides of the valve to prevent drainage problems.
• When installing quick open and close valves, such as a solenoid valve, install it at the inlet side as much as possible, and secure at least 3 m from the valve.
• When pressure reducing in two stages, secure at least 3 m between the valves.
• Install the valve in the proper direction of the fluid flow.
• Install the valve perpendicularly to horizontal lines.
• Provide a by-pass line.
• Set pressure of safety relief valve should be higher than the pressure reducing valve's pressure.
• When the reducing ratio is large, install a reducer to keep the flow velocity in the pipe 30 m/s.

Operating Procedure

Operating Warnings

• Do not touch the valve directly with bare hands. Doing so may result in burns.
• Before flow the steam in pipeline, make sure steam can flow without any dangerous at the end of pipeline and pipeline is connected tightly.

Close the stop valves before and after the reducing valve, and remove all foreign matter and scales via the by-pass line before operation. Open each stop valve slowly. When adjusting pressure, slowly turn the handle.

Adjustment Procedure

Lift the handle to unlock. Then turn the handle in the direction of the (+) symbol on the name plate raises reduced pressure. Turning in the direction of the (-) symbol reduces pressure. The handle goes back to original position when your hand is released.

WARNING

Excessive turning of the handle may damage the spring chamber. Be sure to turn the handle within the range where the spring plate and spring chamber do not come into contact with each other. Use working gloves because there is a possibility that the handle gets heated.

Maintenance and Troubleshooting

Problem	Cause	Solution
Pressure does not rise to the desired level.	Incorrect pressure is being used. Nominal size is too small for these specifications. Incorrect adjustment. Screen is clogged. Pressure gauge malfunction.	Correct the pressure. Replace with the correct nominal sized item. Re-adjust according to the adjustment procedure. Disassemble and clean. Replace the pressure gauge.
Reduced pressure exceeds prescribed level.	Foreign matter is embedded in the valve and/or valve seat, or else scratches exist. Reduced pressure sensing hole is clogged with foreign matter. By-pass valve is leaking.	Disassemble and clean. If scratches exist, polish them away. Disassemble and clean. Repair or replace the valve.
Abnormal noise is heard.	Pressure reduction ratio is too large. Drainage problem. An abrupt open/close valve is located too close to the pressure reducing valve.	Use a two-stage reduction. Install a trap. Move distance as much as possible between the valves.

Disassembly Procedure

1. Discharge the valve's internal pressure until a zero-pressure condition is established.
2. While lifting the handle, turn it in the Counter-Clock Wise direction until the adjusting spring is free (no-load).
3. Unscrew the bolts which secure the spring chamber and remove the spring chamber, the adjusting spring, the bellows, and the spindle.
4. Remove the cap by turning it in the Counter-Clock Wise direction then extract the valve spring, Screen, and valve from the body.
5. Assemble in the reverse order of Disassembly. And tighten the bolts evenly.