Yoshitake GD-28S is a direct type pressure reducing valve designed for cold and hot water applications. This compact and lightweight valve features a cast stainless steel body and an EPDM valve disc. It supports an inlet pressure of up to 1.6 MPa and provides a maximum pressure reduction ratio of 10:1. The wetted parts are made of corrosion-resistant materials to prevent rusty water.

Features

• Wetted parts are made of corrosion-resistant material to prevent rusty water.
• Reduced noise.
• Pressure balance structure can keep the reduced pressure at a constant level without being affected by inlet pressure.
• Closed structure keeps fluid inside even if the diaphragm is damaged or broken.
• Maintenance and inspection can be conducted easily by disassembling simply from the upper side.
• Compact and lightweight design makes piping works easy (can be installed horizontally or vertically).

Specifications

Specification	Value
Application	Cold and hot water
Inlet pressure	1.6 MPa or less
Reduced pressure	(A) 0.05-0.35 MPa (B) 0.3-0.7 MPa
Minimum differential pressure	0.05 MPa
Maximum pressure reduction ratio	10:1
Application temperature	5-90°C
Body	Cast stainless steel
Valve seat	Cast stainless steel
Valve disc	EPDM
Connection	JIS Rc screwed

INFO

A strainer is not incorporated in this model. A strainer (40 mesh or more) is recommended to be installed at the inlet side. Pressure gauge connection port is JIS Rc 1/4 (select from φ42 - Max 1.0MPa, 0.4MPa, 0.2MPa).

Dimensions and Weights

Nominal size	d	L (mm)	H (mm)	H1 (mm)	Weight (kg)
20A	Rc 3/4	135	170	41	2.2
25A	Rc 1	135	170	41	2.2
32A	Rc 1-1/4	180	224	57	4.7
40A	Rc 1-1/2	180	224	57	4.5
50A	Rc 2	200	239.5	61	6.5

Rated Flow Rate

The following table shows the rated flow rate when the differential pressure before and after the valve is 0.15 MPa or more.

Nominal size	20A	25A	32A	40A	50A
Rated flow rate (L/min)	40	60	100	150	250

If the differential pressure before and after the valve is less than 0.15 MPa, refer to the flow rate chart.

Characteristics

Flow Rate Chart (15A to 50A)

Noise Characteristic Chart

Pressure Characteristic Chart

This chart shows variation in reduced pressure when the inlet pressure of 0.6 MPa is changed between 0.15 MPa and 1.0 MPa while the reduced pressure is set at 0.1 MPa.

Flow Characteristic Chart

Offset pressure:

Nominal size	Pressure range	Reduced pressure range	Offset pressure
20A-50A	A	0.05-0.35 MPa	Within 0.05 MPa
20A-50A	B	0.30-0.70 MPa	Within 0.10 MPa

Operation Principle

The spring is compressed by the adjusting screw, the diaphragm is pushed down, and thereby the disc directly connected to it is opened. Fluid coming in from the inlet side flows out from the upper part of the disc to the outlet side, and passes through the reduced pressure detection hole, and is led to the bottom of the diaphragm. The load of the spring and the reduced pressure act to the diaphragm, and the upper and lower force keeps a balance and regulates the valve opening. As a result, the diaphragm keeps the reduced pressure constant.

Installation

Piping Example

WARNING

1. Before leading fluid into the product, close the stop valves at the inlet and outlet of the product and remove foreign substances and scale from the piping completely by using a bypass line.
2. 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.
3. Install a safety relief valve for equipment protection at the outlet side of the product.
4. Be sure to install pressure gauges at the inlet and outlet sides of the product.
5. If a quick operating valve such as a solenoid valve is installed, place it at a distance of at least 3 meters from the product.

Adjusting Procedure

1. Close the stop valves at the inlet and outlet sides of the reducing valve, and take adequate time to blow out fluid by using a bypass line. In doing this, adjust the opening of the globe valve in the bypass pipe so as not to blow out the safety relief valve. After the end of blowing, close the globe valve without fail.
2. Fully open the stop valve at the inlet side slowly, and open the stop valve at the outlet side so that a little fluid can flow through.
3. Remove the domed cap nut, and turn the adjusting screw while watching the pressure gauge at the outlet side.
   • Turn the adjusting screw to the right (clockwise) to increase the reduced pressure.
   • Turn the adjusting screw to the left (counterclockwise) to decrease the reduced pressure.
4. Fully open the stop valve at the outlet side slowly.
5. After the adjustment is complete, tighten the domed cap nut.

TIP

To adjust the set pressure, turn the adjusting screw slowly. Failure to do so may result in damage to the product and other equipment due to hunting.

Structure and Parts