Yoshitake OB-4 and OB-4G are direct acting temperature regulator valves designed specifically for cooling applications. They are widely utilized in systems for ocean vessels, industrial plants, air conditioning equipment, and the chemical industry to accurately adjust cooling temperatures.

These temperature regulators feature a dual-valve structure, providing a larger flow rate compared to single-valve models. They are equipped with an adjusting handle, eliminating the need for special tools and allowing for easy temperature adjustment. The OB-4G model incorporates an external pressure type bellows, ensuring distinguished temperature resistance. Excellent accuracy is maintained since special packing is used for the spindle gland packing, which affects the opening and closing operation of the valve.

Related Models

The shared operation manual for this series also covers the OB-3 and OB-3G models (JIS Rc screwed connections, bronze body, 15-40A). The specifications below focus on the primary OB-4 and OB-4G flanged models.

Specifications

Model	OB-4	OB-4G
Nominal size	15-150A	15-125A
Application (Heating)	Cold water, Refrigerant	Cold water, Refrigerant
Application (Heated)	Cold and hot water, Oil, Non-dangerous fluid	Cold and hot water, Oil, Non-dangerous fluid
Max. pressure (Body)	15-40A: 0.7 MPa [1.0 MPa] 50A: 0.5 MPa [0.7 MPa] 65A: 0.5 MPa [0.7 MPa] 80A: 0.4 MPa [0.5 MPa] 100A: 0.4 MPa 125A: 0.2 MPa [0.35 MPa for OB-4] 150A: 0.2 MPa	15-40A: 0.7 MPa [1.0 MPa] 50A: 0.5 MPa [0.7 MPa] 65A: 0.5 MPa [0.7 MPa] 80A: 0.4 MPa [0.5 MPa] 100A: 0.4 MPa 125A: 0.2 MPa
Max. pressure (Thermal bulb)	1.0 MPa	1.0 MPa
Maximum temperature	180°C	180°C
Temperature adjusting range	40-120°C (For liquid/air)	15-100°C (For liquid/air)
Ambient temperature	Set temp. -10°C or less	Set temp. +30°C or less
Material (Body)	Cast iron	Cast iron
Material (Valve, valve seat)	Bronze (Stainless steel)	Bronze (Stainless steel)
Material (Valve spindle)	Stainless steel	Stainless steel
Material (Bellows)	Phosphor bronze	Phosphor bronze
Material (Thermal bulb)	Stainless steel (with fin for air)	Stainless steel (with fin for air)
Standard capillary length	15-80A: 2 m 100-150A: 3 m	15-80A: 2 m 100-125A: 3 m
Connection	JIS 10K FF flanged	JIS 10K FF flanged

Note: If the ambient temperature is higher than the set temperature or less than 40°C, use the OB-4G (with external pressure type bellows). Available with capillary of up to 5 meters. Available with thermal well (SUS304 made or with a PTFE cap) for liquid.

Temperature Adjusting Range

The term "Withstand temperature" means the temperature from pressure resistance of the bellows.

OB-4

Temperature adjusting range (°C)	Withstand temperature (°C)
40-60	70
50-70	80
60-80	90
80-100	110
100-120	130

OB-4G

Temperature adjusting range (°C)	Withstand temperature (°C)
15-35	50
20-40	50
35-55	70
40-60	90
50-70	100
60-80	110
70-90	120
80-100	130

Performance Data

Temperature Accuracy from Set Point

Depending on capillary length. The preset temperature error is the maximum temperature width ranging from the time when the valve closes until the time when the valve starts to open, not the value expressing the control width.

Standard capillary length	OB-4 (Liquid)	OB-4 (Air)	OB-4G (Liquid/Air)
2m	± 2°C	± 3°C	± 3.5°C
2-3.5m	± 2.5°C	± 3.5°C	± 4°C
3.5-5m	± 3°C	± 4°C	± 4.5°C
(If the preset temperature is higher than 100°C, add ± 1.0°C)

Cv Value Table

Nominal size	15A	20A	25A	32A	40A	50A	65A	80A	100A	125A	150A
OB-4	2	2	4	7	10	14	21	27	42	72	94
OB-4G	2	2	4	7	10	14	21	27	42	72	—

Valve Seat Leakage

Unit: water (L/h). Measured under the condition of 0.5 MPa or max pressure at the temperature of "set temperature - 5°C" for cooling.

Nominal size	15A	20A	25A	32A	40A	50A	65A	80A	100A	125A	150A
OB-4	1.5	1.5	1.8	2.4	3.0	3.6	4.8	6.0	7.2	9.0	10.8
OB-4G	1.5	1.5	1.8	2.4	3.0	3.6	4.8	6.0	7.2	9.0	—

Dimensions and Weights

Structure will be a little different depending on sizes. OB-4G has a little difference in bellows structure.

Nominal size	L (mm)	H1 (mm)	H (mm)	Weight (kg)
15A	126	60	520	15
20A	130	60	520	16
25A	140	70	540	18
32A	150	75	550	21
40A	160	75	550	23
50A	180	110	620	29
65A	215	125	650	38
80A	260	135	670	48
100A	300	160	750	58
125A	360	190	810	76
150A (OB-4 only)	382	220	980	125

Nominal Size Selection Chart (For Water)

How to use the chart: When inlet pressure is 0.3 MPa, outlet pressure is 0.15 MPa, and flow rate is 9 m³/h, first find the intersection point (a) with the differential pressure (ΔP) 0.15 MPa (0.3 MPa – 0.15 MPa) before and after the valve and the flow rate 9 m³/h. Since this intersection point (a) locates between nominal sizes 32A and 40A, select the larger one, 40A. (Chart of the flow rate is a reference value.)

Structure

Installation and Piping

Installation Recommendations

• Make sure to install a strainer (60 to 80 mesh) on the inlet side of the product.
• Install pressure gauges on the inlet and outlet sides of the product to confirm operation.
• Install a thermometer near the thermal bulb.

Cautions

• High Temperature: In case of high temperature fluid, do not touch the product directly with bare hands. There is danger of scald.
• Capillary Tube: The bending radius of the capillary tube must be 40 mm or more. Do not bend it at an acute angle, nor twist it or pull it forcibly.
• Ambient Temperature: Install the product in a place where the temperature does not exceed the preset temperature.

Example of Piping

Installation of Thermal Bulb

Make sure that more than 3/4 of its total length is in direct contact with the fluid to be heated. Install a thermal bulb in a posture in which the top of the thermal bulb is higher than the other side (connecting part to the tube), and in which the marking (on flange or nut) is always at the highest position.

Troubleshooting

Trouble	Cause	Remedy
Temperature does not rise	1. Inadequate adjustment. 2. Nominal size is too small. 3. Temperature range of sensor is not proper. 4. Ambient temperature is higher than preset. 5. Insufficient drainage from trap.	1. Readjust. 2. Replace with proper size. 3. Replace the Upper part set. 4. Install ventilation to decrease ambient temp. 5. Open trap's bypass line.
Temperature rises excessively	1. Inadequate adjustment. 2. Foreign substances stuck in main valve. 3. Leakage from bypass pipe. 4. Thermal bulb or bellows is damaged.	1. Readjust. 2. Repair by factory is necessary. 3. Repair or replace. 4. Replace the Upper part set.
Large error of temperature control	1. Spindle/guide do not move smoothly. 2. Bellows/valve shaft deformed. 3. Thermal bulb/thermometer in wrong positions.	1. Disassemble and clean, or replace. 2. Replace the product. 3. Reinstall at points with best circulation.