How to choose pressure regulating valve for thermal oil working conditions？

According to the characteristics of the thermal oil system, the selection of the pressure regulating valve should focus on high temperature, permeability, pressure difference and other characteristics.The following are the key selection points that consider by our JUDU:

Material and structure selection

High temperature resistant materials

The valve body should be made of chrome-molybdenum steel, chrome-molybdenum-vanadium steel or stainless steel (such as 304/316L), and the temperature resistance range should cover the actual working conditions (up to 600℃).

The pressure regulating valves with metal to metat seat,if the temperature is above 400℃ ,to prevent high temperature from being transmitted to the actuator, need with cooling fin, and the valve body needs to be forged (not cast), the actuator also needs to be equipped with a heat shield.

Sealing construction

The valve stem movement of traditional packing seals can easily cause leakage. Bellows seals isolate the medium through metal, achieving zero leakage and no wearing parts, significantly improving safety. The permeability of thermal oil is 50 times that of steam. Leaked thermal oil evaporates in the air to form a flammable vapor cloud, which will instantly explode when encountering an ignition source (such as electrical sparks, high-temperature equipment). In such a high-risk working condition, the JUDU thermal oil regulating valve adopts a bellows + packing double sealing design, which is more reliable and safer to seal.

Valve type

High pressure differential conditions: Use cage-type regulating valves, multi-stage pressure reducing valves or labyrinth valve cores. Stepped pressure reduction can prevent cavitation, flashing and erosion damage.

Conventional conditions: Bellows-sealed single-seat valves (high leakage level) or sleeve valves (strong anti-clogging).

Key design parameters

Flow characteristics

Equal percentage characteristics (applicable to 60%~70% working conditions) are preferred to adapt to load fluctuations; linear characteristics are only used for simple liquid level control.

Caliber calculation (Cv value)

Ensure that the opening is ≤90% at maximum flow and ≥10% at minimum flow to avoid small opening scouring or oscillation.
The theoretical Cv value needs to be corrected by 10 according to the hot oil viscosity.

Pressure grade

The rated pressure must be ≥1.1~1.2 times the maximum working pressure of the system, and the allowable stress of the material must be checked according to the temperature (e.g. the strength of carbon steel decreases at 200°C).

Actuators and accessories

Selection of actuators

Pneumatic actuators need to have a larger thrust margin (high temperature weakens the output force); electric actuators need high temperature resistant motors (environment ≤ 80℃).

Explosion-proof type (Ex d IIC T4 or above) is used for flammable environments

Necessary accessories

Pre-filter (to prevent particles from getting stuck);

Air filter pressure reducing valve (to ensure clean air source);

Flow limiting orifice (to reduce pressure under high pressure difference conditions).

Special working conditions

Medium containing particles: Use V-type valve core or ceramic lined valve to enhance wear resistance .

Frequent start and stop: Avoid fast opening characteristics and reduce water hammer damage .

The above-mentioned factors and designs can ensure the long-term stable operation of the regulating valve in the thermal oil system.