The Yoshitake VB-7 and VB-7S are vacuum relief valves designed to protect devices and piping by adjusting vacuum and preventing accidents resulting from vacuum pressure. The VB-7 is constructed with a brass body and bronze valve, while the VB-7S is made of stainless steel for improved corrosion resistance. Both models feature a special valve structure that ensures stable performance without chattering and hunting, in a compact, lightweight design that is easy to handle.

Features

• Protects devices and piping by adjusting vacuum and preventing accidents resulting from vacuum pressure.
• Special valve structure ensures stable performance without chattering and hunting.
• Compact, lightweight and easy to handle.
• Made of corrosion resistant material (VB-7S).

Seat Leakage and Vibration

• Do not use this product in equipment or devices where seat leakage is not allowed. The product has seat leakage within the allowable range and cannot be completely closed (zero seat leakage).
• Cannot be used in equipment or devices generating vibration. Vibration may cause product malfunction.

Specifications

Model	VB-7	VB-7S
Application	Steam, Air	Steam, Air
Working Pressure	1.0 MPa	1.0 MPa
Pressure Regulating Range (Spring A)	-0.5 to -21 kPa (Standard set: -4 kPa)	-0.5 to -21 kPa (Standard set: -4 kPa)
Pressure Regulating Range (Spring B)	-21 to -48 kPa (Standard set: -21 kPa)	-21 to -48 kPa (Standard set: -21 kPa)
Pressure Regulating Range (Spring C)	-48 to -81 kPa (Standard set: -48 kPa)	-48 to -81 kPa (Standard set: -48 kPa)
Maximum Temperature	200°C	200°C
Body Material	Brass	Stainless steel
Valve Material	Bronze	Stainless steel
Valve Seat Material	Brass	Stainless steel
Connection	JIS Rc screwed	JIS Rc screwed

Dimensions and Weights

Nominal Size	d	H (mm)	A (mm)	Weight (kg)
15A	Rc 1/2	100.0	35	0.50
20A	Rc 3/4	100.0	35	0.50
25A	Rc 1	112.5	41	0.75
32A	Rc 1-1/4	113.5	50	1.05
40A	Rc 1-1/2	130.0	55	1.45
50A	Rc 2	156.5	65	2.45

Construction

No.	Name of Parts	Material (VB-7)
1	Body	Brass (C3604)
2	Cap	Brass (C3604)
3	Valve	Bronze (CAC406)
4	Valve Seat	Brass (C3604)
5	Spindle	Brass (C3604)
6	Plug	Brass (C3604)
7	Spring	Stainless Steel (SUS304)
8	Adjusting Screw	Brass (C3604)
9	Lock Nut	Brass (C3604)
10	Gasket	Copper (C1100)
11	Gasket	Copper (C1100)
12	Name Plate	Stainless Steel (SUS304)
13	Rivet	Carbon Steel (S15C)

Operation

When the negative pressure in the equipment or piping increases and approaches the set pressure (suction pressure), the force of the fluid opening valve (3) balances with the force of the adjusting spring (7) closing valve (3), and slight pre-leakage occurs. If the negative pressure increases further, valve (3) will open. The degree of opening of valve (3) changes according to the variation of negative pressure in the equipment and piping, thereby controlling the amount of induced air and maintaining a predetermined vacuum level.

Sizing and Selection

Note: The flow rate in the chart above is for reference only.

Piping Examples

Example piping for temperature control equipment

Example piping for silencer without check valve

Installation and Adjustment

Installation Precautions

• Do not disassemble the product casually. Disassembly may compromise product function.
• When installing, tighten the hexagonal part of the body (1) with a wrench. Never tighten the hexagonal part of the cap (2). Loosening the body (1) and valve seat (4) may cause fluid leakage, resulting in burns or injury.

• Flush the inside of the piping thoroughly to remove foreign matter before installation.
• Install the product vertically with the cap (2) positioned on the upper side. It will not function correctly if installed in other positions.
• Ensure the connection is fully secure with no fluid leakage. Insufficient connection can lead to leakage due to vibration, posing a risk of burns with high-temperature fluids.
• Brass products may corrode depending on water quality, leading to malfunction. Select stainless steel products (VB-7S) for corrosive environments.

Adjustment Method

1. Remove the cap (2) and slightly loosen the lock nut (9).
2. To increase the set pressure (decrease the vacuum level), turn the adjusting screw (8) counterclockwise.
3. To decrease the set pressure (increase the vacuum level), turn the adjusting screw (8) clockwise.
4. When tightening the lock nut (9), hold the adjusting screw (8) fixed with a wrench or similar tool.

Troubleshooting

Symptoms	Causes	Countermeasures
Leakage confirmed visually from the cap or by sound	1. Foreign matter/scale caught between the contact surfaces of the valve (3) and valve seat (4). 2. Scratches on the contact surfaces of the valve and seat. 3. Product malfunction caused by excessive vibration from connected piping. 4. The difference between the set pressure and the normal working pressure is too small. 5. Unsmooth operation of the sliding parts of the valve and seat.	1. Repair at the factory is required. 2. Disassembly and part replacement are required (repair at factory). 3. Do not use this product in equipment or devices with excessive vibration. 4. Increase the difference between the set pressure and normal working pressure. (Readjustment requires factory repair). 5. Disassembly and cleaning are required (repair at factory).
Operates below the set pressure	1. Product specifications and operating conditions are incompatible. 2. Pressure gauge malfunction. 3. Deviation in product pressure setting.	1. Check the pressure setting value on the nameplate (12). Change the product if operating conditions differ. 2. Calibrate or replace the pressure gauge. 3. Repair at the factory is required.
Does not operate when set pressure is reached	1. Product specifications and operating conditions are incompatible. 2. Pressure gauge malfunction. 3. Deviation in product pressure setting. 4. Unsmooth operation of sliding parts.	1. Check the pressure setting value on the nameplate (12). Change the product if operating conditions differ. 2. Calibrate or replace the pressure gauge. 3. Repair at the factory is required. 4. Disassembly and cleaning are required (repair at factory).

INFO

The seat leakage of this product is within the allowable range and cannot be completely closed (zero seat leakage).