Yoshitake GD-30 is a direct-type pressure reducing valve designed specifically for steam applications. It utilizes an external pressure type bellows for internal sensing and is equipped with a built-in 60 mesh strainer to protect the stainless steel valve and valve seat from dirt. Pressure adjustment is easily handled without the need for tools, making it a highly reliable and maintenance-friendly choice for industrial steam control.

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-resistant and durable stainless steel 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 the pressure sensing part.

Specifications

Specification	GD-30	GD-30S
Nominal Size	15A-25A, 40A-50A	15A-25A
Fluid	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 (B) 0.05-0.4 MPa (C) 0.35-1.0 MPa
Min. Differential Pressure	0.05 MPa	0.05 MPa
Max. 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	Stainless steel	Stainless steel
Bellows	Phosphor bronze	Stainless steel
Connection	JIS Rc screwed, NPT, BSPT	JIS Rc screwed

Dimensions and Weights

Nominal Size	d	L (mm)	H1 (mm)	H (mm)	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, NPT 1-1/2, BSPT 1-1/2	140	77	307	10.1
50A	Rc 2, NPT 2, BSPT 2	150	77	307	10.4

Note: The values in parentheses are the dimensions of the GD-30S.

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 Size Selection Chart (For Steam)

Note: 40A and 50A have a different structure and utilize the chart below:

Selection 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.

The nominal sizes selection chart is based on measured data. Set the safety factor at 80% to 90%.

Installation

Example of Piping

Precautions During Installation

Safety Relief Valve Piping

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

Installation Guidelines

• Do not disassemble the valve unreasonably, as it may affect original performance.
• Remove foreign matter and scales from the lines before connecting the valve.
• Install a strainer (80 mesh) at the valve inlet side to ensure correct pressure control.
• Install a safety valve at the outlet side as a safety device for equipment.
• Install a pressure gauge at both the inlet and outlet sides of the valve for correct adjustment.
• Install a steam trap at the inlet side to prevent drainage problems.
• When installing quick open and close valves (such as a solenoid valve), secure at least 3 meters from the reducing valve.
• When pressure reducing in two stages, secure at least 3 meters between the valves.
• Install the valve in the proper direction of the fluid flow, perpendicularly to horizontal lines.
• Provide a bypass line.
• The set pressure of the 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 at 30 m/s.

Operating Procedure

Burn Hazard

Do not touch the valve directly with bare hands. Doing so may result in burns. Before allowing steam in the pipeline, make sure steam can flow safely at the end of the pipeline and that the pipeline is connected tightly.

Pre-operation Steps

Close the stop valves before and after the reducing valve, and remove all foreign matter and scales via the bypass line before operation. Open each stop valve slowly to prevent hunting or water hammer.

Adjustment Procedure

1. Lift the handle to unlock.
2. Slowly turn the handle in the direction of the (+) symbol on the name plate to raise reduced pressure. Turning in the direction of the (-) symbol reduces pressure.
3. The handle goes back to its original position (locked) when your hand is released.

Handle Adjustment Precaution

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.

Note for 40A and 50A sizes: There is a possibility that the handle is stuck and cannot be removed. It is easier to turn the handle to obtain high reduced pressure if a screwdriver (axis diameter φ6) is inserted through the notches and turned left or right.

Maintenance Procedure

Troubleshooting

Problem	Cause	Solution
Pressure does not rise to the desired level	Incorrect pressure is used. Nominal size is too small. Incorrect adjustment. Screen is clogged. Pressure gauge malfunction.	Correct the pressure. Replace with correct nominal size. Re-adjust. Disassemble and clean. Replace gauge.
Reduced pressure exceeds prescribed level	Foreign matter is embedded in valve/seat, or scratches exist. Sensing hole is clogged. 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.	Use a two-stage reduction. Install a trap. Maximize distance between the valves.

Precautions During Maintenance

Residual Pressure Hazard

Completely discharge internal pressure from the valves, lines, and equipment, and cool the valve down to a level where you can touch it with bare hands before disassembly and inspection. Failure to do so may result in injury or burns due to residual pressure or steam spillage.

Disassembly Precautions

• The pressure reducing valve shall be disassembled and inspected by a qualified person or manufacturer.
• While disassembling, drain flows out from the valve, so catch it with a container.
• Close the stop valves before and after the reducing valve and remove all foreign matter before resuming operation.

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-clockwise direction (minus direction) until the spring is free (no-load).
3. Unscrew the bolts which secure the Spring Chamber and remove the Spring Chamber (handle etc. cannot be disassembled), the adjusting spring, the bellows, and the spindle.
4. Remove the cap by turning it counter-clockwise, then extract the valve spring, screen, and valve from the body.
5. Assemble in the reverse order of disassembly. Tighten the bolts evenly and accurately.

Exploded Drawings

For 15A, 20A, 25A:

For 40A, 50A:

(Part names shown in boxes in the source drawings are consumable items)