Yoshitake GD-41N series are direct type pressure reducing valves designed specifically for cold and hot water applications. The GD-41N (screwed connection) and its flanged counterpart, the GD-43N, conform to the Japanese Water Supply Act (JWWA) and feature wetted parts made of stainless steel (SCS14A and SUS316) for superior corrosion resistance. A pressure balance structure is incorporated to maintain a constant reduced pressure regardless of fluctuations in the inlet pressure, making them highly reliable in plumbing and water supply systems.

Features

• Space and Resource Saving: Compact design with used materials clearly marked on the body and lower cap for easy resource recycling.
• Corrosion Resistant: Cast stainless steel (SCS14A) is used for the body and wetted parts.
• Durable Diaphragm: PTFE covers the diaphragm contact surface to the fluid, making it less liable to deteriorate.
• Stable Control: The pressure balance structure keeps the reduced pressure at a constant level without being affected by inlet pressure changes.
• Closed Structure: Prevents fluid from flowing to the outside in the event of an internal failure.
• Compliance: Models conforming to the Japanese Water Supply Act (JWWA approval for GD-41N, GD-43N).

GD-41N

GD-43N

Specifications

Specification	GD-41N	GD-43N-10	GD-43N-20
Connection	JIS Rc screwed	JIS 10K FF Flanged	JIS 20K RF Flanged
Nominal Size	15A, 20A, 25A	15A, 20A, 25A	15A, 20A, 25A
Application Fluid	Cold and hot water	Cold and hot water	Cold and hot water
Inlet Pressure	0.07 - 2.0 MPa	0.07 - 1.0 MPa	0.07 - 2.0 MPa
Reduced Pressure	Spring A (yellow): 0.02-0.1 MPa Spring B (red): 0.1-0.25 MPa Spring C (black): 0.25-0.5 MPa	Spring A (yellow): 0.02-0.1 MPa Spring B (red): 0.1-0.25 MPa Spring C (black): 0.25-0.5 MPa	Spring A (yellow): 0.02-0.1 MPa Spring B (red): 0.1-0.25 MPa Spring C (black): 0.25-0.5 MPa
Min. Differential Pressure	0.05 MPa	0.05 MPa	0.05 MPa
Max. Reduction Ratio	10:1	10:1	10:1
Operating Temperature	5 - 90°C	5 - 90°C	5 - 90°C
Cv Value	15A: 0.4, 20A: 0.6, 25A: 0.8	15A: 0.4, 20A: 0.6, 25A: 0.8	15A: 0.4, 20A: 0.6, 25A: 0.8
Pressure Characteristic	Set pressure ±0.05 MPa	Set pressure ±0.05 MPa	Set pressure ±0.05 MPa

Dimensions and Weights

GD-41N (Screwed)

Nominal Size	d	Weight (kg)
15A	Rc 1/2	1.2
20A	Rc 3/4	1.1
25A	Rc 1	1.0

GD-43N (Flanged)

Size	D	C	g	t	f	n-h	Weight (kg)
15A	95	70	51	14 (12)	1	4-15	2.8 (2.6)
20A	100	75	56	16 (14)	1	4-15	3.0 (2.9)
25A	125	90	67	16 (14)	1	4-19	4.0 (3.7)

(Note: Values in parentheses are the weights and dimensions for the GD-43N-10 10K version. All other dimensions represent JIS 20K RF flange).

Internal Structure and Materials

Component	Material
Body / Cap	Cast Stainless Steel (SCS14A)
Spring Chamber	Stainless Steel (SUS316)
Disc (Valving Element)	Special Synthetic Rubber (FKM) & Stainless Steel (SUS304)
Spindle	Cast Stainless Steel (SCS14A)
Diaphragm	Heat-resistant Synthetic Rubber (FKM) and PTFE
Diaphragm Shell	Stainless Steel (SUS316)
Adjusting Spring	Alloy Steel (SWOSC-V)
Adjusting Screw	Brass (C3604)
O-Rings	FKM

Nominal Size Selection (For Cold and Hot Water)

Selection Example: To determine the nominal diameter for a pressure reducing valve with a primary pressure of 0.5 MPa, a secondary pressure of 0.3 MPa, and a flow rate of 40 m³/h (standard condition):

1. Find the intersection point of the inlet pressure of 0.5 MPa and the reduced pressure of 0.3 MPa.
2. Trace down vertically from this intersection to find the point matching the flow rate of 40 m³/h.
3. If the intersection lies between nominal sizes 15A and 20A, always select the larger size, 20A.

Performance Note

Performance values in the Selection Chart are referential. Since performance can change according to piping conditions and the usage environment, secure a safety factor of 80% to 90% (or 20% margin) when sizing.

Installation and Piping

Installation Precautions

• Strainer Installation: Attach a strainer (60 mesh or more) to the inlet of the pressure reducing valve. Ingress of foreign substances or scale degrades performance and may damage the valve.
• Safety Valve: Install a safety valve at the outlet side of the pressure reducing valve to protect the downstream equipment. The set pressure of the safety valve must be higher than that of the pressure reducing valve.
• Quick Opening/Closing Devices: When installing a solenoid valve or similar device, the distance between it and the pressure reducing valve must be at least 3 meters to prevent water hammer and short life.
• Two-Stage Reduction: If two-stage pressure reduction is used, maintain at least 3 meters between the two pressure reducing valves to prevent hunting.

Adjustment Procedures

1. Close the stop valves located upstream and downstream of the pressure reducing valve. Open the bypass stop valve to fully discharge foreign materials from the piping. Be aware of the secondary pressure to ensure the downstream safety valve is not activated. Close the bypass stop valve after flushing.
2. Gradually open the primary stop valve.
3. Remove the hexagon cap nut. Observing the secondary pressure gauge, gradually turn the adjusting screw to the desired pressure. To increase pressure, turn the screw clockwise; to reduce pressure, turn it counterclockwise.
4. Finely adjust the secondary pressure by gradually opening the secondary stop valve. Replace the hexagon cap nut once completed.

Troubleshooting and Maintenance

Many faults in pressure reducing valves are due to the existence of foreign materials. Before disassembling, verify that the strainer is not clogged (which decreases secondary pressure) and that the bypass valve is not leaking (which increases secondary pressure).

Common Symptoms and Corrective Actions

Symptom	Possible Cause	Corrective Action
Reduced pressure is higher than set pressure	Damaged diaphragm.	Replace the diaphragm unit.
	Foreign material pinched between valving disc and valve seat, or dents/scratches are seen on the seat.	Clean the assembly. If the disc or seat is damaged, replace the damaged part (or the valve casing).
	Poor seal of valve stem O-ring.	Replace the valve stem O-ring with a new one.
Reduced pressure is lower than desired pressure / Fluid fails to flow	Valve stem O-ring is locked.	Replace the valve stem O-ring with a new one.
	Valving element and valve seat are locked due to foreign material or damage.	Clean the disc and valve seat. Replace if damaged.
Exterior Leakage	Loose cross-recessed pan head screws on the spring cover.	Retighten the screws evenly in a crisscross pattern.
	Loose lower cap.	Retighten the lower cap.
	Broken O-ring on the lower cap.	Replace the O-ring for the cap with a new one.

Disassembly Warning

When disassembling or checking, completely release the pressure from the valve and piping. Ensure the valve has cooled down. Residual pressure or hot drain may cause bodily injury. Replace O-rings upon every maintenance and coat them with fluorine grease before reassembly.

Periodic Replacement:

• Diaphragm Set: Approximately 3 years.
• Disc: Approximately 3 years.
• O-Rings: Approximately 3 years.