The Yoshitake OB-30 and OB-31 series are direct-acting bellows temperature regulators designed for precise temperature control in heating and cooling applications. Featuring a bronze body and a soft PTFE valve seat, these regulators offer excellent durability and high sealability. The single valve and balance bellows structure ensures stable temperature control without being affected by inlet pressure fluctuations.

Features

1. Red handle type is for heating and blue handle type for cooling. It is possible to identify their application at a glance.
2. Excellent durability and high sealability ensured by valve part of stainless steel and fluororesin.
3. Single valve and balance bellows structure offers stable temperature control without being affected by inlet pressure fluctuations.
4. Easy changeable thermal specification by easy attachment and detachment of the body and thermal bulb.
5. Wide temperature adjusting range, applicable to a wide variety of applications.
6. The thermal bulb is usable for heating and cooling, which is common for all sizes (15 to 25A). It is possible to select models considering the temperature adjusting range only.
7. Easy setting of the initial temperature by handle operation.

Specifications

Body Specifications

Model	OB-30	OB-30U	OB-31	OB-31U
Purpose	For heating	For heating	For cooling	For cooling
Application	Steam, Hot water	Steam, Hot water	Cold water, Refrigerant	Cold water, Refrigerant
Maximum pressure	1.0 MPa (1.7 MPa for hot water)	1.0 MPa (1.7 MPa for hot water)	1.7 MPa	1.7 MPa
Max. differential pressure	1.0 MPa	1.0 MPa	1.0 MPa	1.0 MPa
Valve seat leakage	0.05% or less of rated flow rate	0.05% or less of rated flow rate	0.05% or less of rated flow rate	0.05% or less of rated flow rate
Max. temperature	185°C	185°C	185°C	185°C
Material (Body)	Bronze	Bronze	Bronze	Bronze
Material (Valve)	Brass (PTFE)	Brass (PTFE)	Brass (PTFE)	Brass (PTFE)
Material (Valve seat)	Stainless steel	Stainless steel	Stainless steel	Stainless steel
Connection	JIS Rc screwed	JIS Rc screwed (union joint)	JIS Rc screwed	JIS Rc screwed (union joint)

Sensor Specifications

Specification	Details
Heated/Cooled fluid	Cold and hot water, Oil, Liquid
Maximum pressure	1.0 MPa
Material (Thermal bulb)	Copper pipe (nickel chrome plated) *
Material (Capillary)	Copper pipe
Material (Capillary tube)	Stainless steel
Standard capillary length	2 m
Connection	JIS R 1/2

• Available with thermal well (stainless steel made).
• In the case of attached to thermal bulb, the bush of thermal bulb will be unnecessary.
• Available with capillary of 3 or 5 meter.

Temperature Adjusting Range

Temperature adjusting range (°C)	Withstand temperature (°C)
0-35	75
25-70	110
40-100	140
60-130	170
70-150	190

INFO

• The term “withstand temperature” means the temperature from pressure resistance of the bellows.
• The maximum temperature of the thermal bulb for cooling is 100°C.

Dimensions and Weights

Body Dimensions

Nominal size	d	L (OB-30/31)	Weight (OB-30/31)	L (OB-30U/31U)	Weight (OB-30U/31U)
15A	Rc 1/2	75 mm	2.1 kg	160 mm	3.1 kg
20A	Rc 3/4	80 mm	2.2 kg	160 mm	3.1 kg
25A	Rc 1	90 mm	2.4 kg	160 mm	3.1 kg

Sensor Dimensions

Capillary length	Weight
2 m	0.6 kg

OB-30

OB-31U

Nominal Size Selection

OB-30 / OB-30U (For Steam)

How to use the chart: When selecting the nominal size of a temperature regulator whose inlet pressure (P1), outlet pressure (P2), and steam flow rate are 0.2 MPa, 0.15 MPa, and 20 kg/h, respectively, first find intersection point (a) of the inlet pressure of 0.2 MPa and the outlet pressure of 0.15 MPa. Trace down vertically from this intersection point (a) to find intersection point (b) with the flow rate of 20 kg/h. Since this intersection point (b) lies between nominal sizes 15A and 20A, select the larger one, 20A.

OB-31 / OB-31U (For Water)

How to use the chart: When selecting the nominal size of a temperature regulator whose inlet pressure, outlet pressure, and flow rate are 0.3 MPa, 0.15 MPa, and 1 m³/h, respectively, first find intersection point (a) of the differential pressure (ΔP) of 0.15 MPa (0.3 MPa – 0.15 MPa) before and after the valve and the flow rate of 1 m³/h. Since this intersection point (a) lies between nominal sizes 15A and 20A, select the larger one, 20A.

INFO

• When the OB-30 or OB-30U is used and the fluid is hot water, use the selection chart shown above.
• Chart of the flow rate is a reference value.

Structure and Parts

OB-30U

OB-31U

No.	Part name	No.	Part name
1	Body	12	Handle
2	Spring chamber	13	Bellows follower
3	Disc	14	Bellows
4	Valve	15	Ring
5	Valve seat	16	Gasket
6	Balance bellows	17	Bolt
7	Spindle	18	Bushing
8	Nut	19	Washer of packing
9	Guide	20	Thermal bulb
10	Guide	21	Capillary tube
11	Spring	*22	Packing

The parts marked "" are available as consumable supply.*

Heating the thermal bulb [20] makes its inner pressure rise, while cooling it makes the pressure lower. The bellows [14] expands/contracts responding to the change in the internal pressure that is transmitted through the capillary tube [21], and this allows the valve [4] open/close.

Installation

Precaution for installation

1. Do not disassemble the product unless it is necessary. Disassembly may prevent the product from functioning properly.
2. Be sure to remove foreign substances and scale from the piping before connecting the product.
3. Be sure to install a strainer (60 to 80 mesh) at the inlet side of the product.
4. Be sure to install pressure gauges at the inlet and outlet sides of the product for operation check.
5. When installing, check the direction and posture of the product.
6. Install the product to a place where the ambient temperature does not exceed the set temperature.
7. Install a thermometer close to the thermal bulb.
8. Make sure that more than 3/4 of the thermal bulb's total length is in direct contact with the fluid to be heated or cooled.
9. The bend radius of the capillary tube should be more than 40 mm. Avoid bending at a sharp angle, twisting or pulling it with force.
10. Make sure that the capillary tube is not in contact with steam piping.
11. Do not apply excessive load, torque or vibration to the product.

Installation of body

1. Be sure not to lose the bellows follower [13] (attached component).
2. Install the body to horizontal piping with the handle [12] facing upward.
3. Check the direction of the product so that the fluid flowing and the arrow marked on the body [1] are in the same direction.
4. Be sure to install pressure gauges, a strainer and a bypass line to the piping.
5. The pressure of heating or cooling fluid should be reduced with a reducing valve if it exceeds the maximum pressure.
6. Before stopping operation of the product for an extended period, completely discharge the condensate inside the product and piping, and close the stop valves installed at before and after the product.
7. Before leading fluid into the product, be sure to remove foreign substances and scale from the piping completely by using a bypass line.

Installation of thermal bulb

1. Although the thermal bulb [20] can be mounted in any posture, make sure that more than 3/4 of its total length is in direct contact with the fluid to be heated or cooled.
2. Screw in the bushing [18] first, then use the washer of packing [19] to secure the thermal bulb.
3. The bend radius of the capillary tube [21] should be more than 40 mm. Avoid bending at a sharp angle, twisting or pulling it with force.
4. Install a thermometer close to the thermal bulb.
5. When inserting the thermal bulb into the piping for temperature detection, it should be installed at a point where the circulation is best.

TIP

The thermal bulb is made of copper and can be easily bent if it bumps against something. Handle with care.

Assembly of body and sensor

Place the bellows follower [13], which is packaged with the body, into the bellows [14] with its flat surface facing downward and then screw it into the lower surface of the body [1] by the ring [15].

It makes the assembly easier to loosen the handle [12] to direction of the "L" position. Be sure not to lose the bellows follower because the product does not function properly without it.

Piping Examples

OB-30, OB-30U (for heating)

OB-31, OB-31U (for cooling)

Operating Procedure

Precaution for operation

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. When blowing fluid via the bypass line, keep fluid temperature from exceeding the withstand temperature of the product.
2. Adjust set temperature while watching the thermometer with enough time.
3. Before stopping operation of the product for an extended period, completely discharge the fluid inside the product and piping, and close the stop valves installed at before and after the product.
4. If condensate accumulates while the product closes, install a trap to discharge the condensate.

Adjustment

Taking a wrong adjusting procedure may cause hunting, scale problems or water hammer, and can heavily damage the main parts of the product. Be sure to follow the procedure below.

1. Close the stop valves at the inlet and outlet sides of the product. Open the bypass stop valve and blow fluid through the bypass line with enough time. After discharging, be sure to close the bypass stop valve.
2. Turn the handle [12] and move the indicator to the desired temperature position on the scale. To raise the temperature, turn the handle clockwise (to direction of the "H" position). To lower the temperature, turn it counterclockwise (to direction of the "L" position).
3. Slowly open the inlet stop valve to its full open position, and then, open the outlet stop valve little by little to its full open position.
4. Adjust the handle till the desired temperature is obtained while watching the thermometer with enough time.

Scale reading and set temperature

Scale reading	OB-30, OB-30U (for heating)
	0-35°C	25-70°C	40-100°C	60-130°C	70-150°C
0	-10°C	14°C	28°C	-	-
1	5°C	30°C	47°C	58°C	67°C
2	20°C	46°C	66°C	81°C	91°C
3	31°C	62°C	86°C	105°C	119°C
4	42°C	78°C	106°C	132°C	162°C

Scale reading	OB-31, OB-31U (for cooling)
	0-35°C	25-70°C	40-100°C
0	-	-	-
1	-14°C	11°C	23°C
2	9°C	38°C	55°C
3	32°C	65°C	94°C
4	55°C	98°C	141°C

The tables above show the set temperature per scale reading as a guide. Because the temperature varies slightly according to the conditions of use, adjust the handle till the desired temperature is obtained.

Maintenance

Precaution for inspection

Inspection must be done by experienced professional or valve manufacturer. Completely discharge the pressure inside of the product, piping and equipment prior to disassembly and inspection. When fluid is hot, cool down the product to the condition that it can be touched with bare hands. Failure to follow this notice may result in scalds, injury or contamination on the surroundings due to the residual pressure.

WARNING

1. Do not disassemble the bellows while the thermal bulb is heated. Failure to follow this notice may damage the bellows and prevent the product from functioning properly.
2. Do not give any shock to the thermal bulb.

Troubleshooting

OB-30, OB-30U

Trouble	Cause	Remedy
Temperature does not rise.	1. Inadequate adjustment. 2. Insufficient drainage from the trap of heat exchanger, etc.	1. Readjust according to Adjustment procedure. 2. Check the trap and replace it if necessary.
Temperature rises excessively.	1. Inadequate adjustment. 2. Foreign substances stuck or damage on the disc [3] and valve seat [5]. 3. The thermal bulb [20] or bellows [14] is damaged.	1. Readjust according to Adjustment procedure. 2. Remove the foreign substances. If there is damage, replace the parts. 3. Replace the sensor.
Large error of temperature control.	1. The thermal bulb [20] and thermometer are installed in wrong positions. 2. Inlet pressure is too high.	1. Reinstall them at points where the circulation is best. 2. When steam consumption is small, lower the inlet pressure for better temperature control.
Outside leakage.	1. Leakage from the gasket [16]. 2. Balance bellows [6] is damaged.	1. Retighten the gasket, or replace the part. 2. Disassemble the product and replace the part.

OB-31, OB-31U

Trouble	Cause	Remedy
Temperature does not lower.	1. Inadequate adjustment. 2. The thermal bulb [20] or bellows [14] is damaged.	1. Readjust according to Adjustment procedure. 2. Replace the sensor.
Temperature lowers excessively.	1. Inadequate adjustment. 2. Foreign substances stuck or damage on the disc [3] and valve seat [5].	1. Readjust according to Adjustment procedure. 2. Remove the foreign substances. If there is damage, replace the parts.
Large error of temperature control.	1. The thermal bulb [20] and thermometer are installed in wrong positions. 2. Inlet pressure is too high.	1. Reinstall them at points where the circulation is best. 2. When steam consumption is small, lower the inlet pressure for better temperature control.
Outside leakage.	1. Leakage from the gasket [16]. 2. Balance bellows [6] is damaged.	1. Retighten the gasket, or replace the part. 2. Disassemble the product and replace the part.