The chemical heat transfer oil reactors and heating circulation pipelines have a wide temperature range of media. Conventional mineral heat transfer oil operates at temperatures ranging from 180 to 300℃ for long periods, while synthetic high-temperature heat transfer oil can reach temperatures of 320 to 350℃. Ordinary room temperature transmitters and seals may experience black screens, drift, and seal failure when exposed to high temperatures. Therefore, it is necessary to match the actual temperature of the medium with a corresponding temperature-resistant high-temperature transmitter. The Longlv PTL512H has multiple temperature-resistant specifications, suitable for all types of heat transfer oil reaction conditions.

The chemical heat transfer oil reactor and heating circulation pipeline have a wide range of medium temperatures. Conventional mineral heat transfer oil operates at 180~300℃ for a long time, while synthetic high-temperature heat transfer oil can reach 320~350℃. Ordinary room temperature transmitters and seals will black out, drift, and fail to seal when exposed to high temperatures. Therefore, it is necessary to match the actual temperature of the medium with a corresponding temperature-resistant high-temperature transmitter. The Longlv PTL512H has multiple temperature-resistant specifications, suitable for all types of heat transfer oil reaction conditions.

1. Temperature range of heat transfer oil pipeline and corresponding temperature resistance classification of instruments

1. Operating conditions for low-temperature heat transfer oil (within 180℃, small heating reactor)

If the long-term temperature of the medium is ≤180℃, a high-temperature transmitter with a medium temperature resistance of 200℃ can be selected.

The ordinary short heat dissipation structure can isolate heat and prevent it from conducting to the meter circuit, making it suitable for conventional low-temperature synthesis and drying of heat transfer oil pipelines.

2. Mainstream standard heat transfer oil operating conditions (200-280℃, covering the vast majority of chemical reactions)

The rated operating temperature of mineral heat transfer oils on the market is mainly concentrated in this range, with the lowest temperature resistance of the selected medium being 300℃, which is also the standard main model of PTL512H.

Equipped with extended multi-layer heat sinks, the device increases the heat dissipation distance, effectively isolating the high-temperature heat transfer oil at the pressure tapping end. This ensures that the electronic components of the meter head are always maintained within a safe temperature range, eliminating temperature drift and screen malfunctions.

3. High-temperature synthetic heat transfer oil operating conditions (280~350℃, fine chemical industry, resin polymerization reaction)

When the medium temperature exceeds 300℃, the standard cooling model becomes insufficient. It is necessary to choose the high-temperature resistant isolation model PTL512H, which can withstand 350℃, paired with an extended cooling rod and high-temperature filling isolation silicone oil for dual heat insulation. For extreme operating conditions exceeding 350℃, a condensation pressure guiding tube can be used as an auxiliary cooling measure.

Hard rules for temperature selection

The upper temperature limit indicated on the instrument for the medium must be 30-50°C higher than the long-term operating temperature of the heat transfer oil, with an overtemperature buffer reserved to avoid instrument damage caused by instantaneous overtemperature due to exothermic reaction.

II. Four major fault points where ordinary transmitters cannot be used in high-temperature heat transfer oil pipelines

 High-temperature aging drift of circuit board

 The electronic components of conventional transmitters can only withstand an ambient temperature range of -20 to 80℃. When exposed to continuous high-temperature conduction from the heat transfer oil, the chips and resistors may fail due to heat, leading to a wide range of pressure value drift and malfunction of the overpressure interlock protection.

 Leakage due to high-temperature hardening of sealing rubber

 Ordinary nitrile rubber seals undergo rapid aging and cracking at temperatures above 200℃, and have strong permeability to heat transfer oil, leading to leakage from threads and gauge head gaps, posing a fire safety hazard.

 Diaphragm deformation at high temperature, measurement of linear distortion

 The elasticity of ordinary diaphragms without high-temperature heat treatment changes over long periods at high temperatures, leading to a continuous increase in full-range measurement deviation, which cannot be stabilized even with frequent calibration.

 Carbon buildup in the heat transfer oil blocks the pressure chamber

 High-temperature oil cracking produces carbon residue, which can easily clog the small pressure taps, leading to pressure buildup. This results in the inability to return to zero under no-load conditions and a lag in pressure feedback.

III. Core Advantages of Longlv PTL512H High-Temperature Pressure Transmitter Adapted to Heat Transfer Oil Pipeline

1. Multi-position temperature-resistant specifications, fully covering the temperature range of heat transfer oil

Standardly equipped with three temperature-resistant versions for media at 200℃, 300℃, and 350℃, suitable for low-temperature, conventional, and ultra-high-temperature heat transfer oil reaction pipelines; featuring an extended layered heat dissipation structure that relies on air convection for rapid heat dissipation, blocking high temperatures from being conducted to the meter head, eliminating the need for additional water cooling devices, and making installation easier.

2. High-temperature resistant seals and diaphragms, capable of resisting high-temperature carbonization and corrosion from heat transfer oil

The liquid-contacting diaphragm is made of heat-treated and strengthened 316L stainless steel, which is resistant to deformation at high temperatures. It is equipped with perfluoroethylene high-temperature sealing components, which remain non-hardened and non-leaky even after long-term use at 300°C. The flush, cavity-free pressure measurement end face prevents the accumulation of heat transfer oil and carbon residue in dead zones, thereby avoiding measurement drift caused by blockage at its source.

3. Special compensation circuit for high temperature, ensuring stable values under both high and low temperature conditions

The entire machine is equipped with a wide-temperature digital compensation program, ensuring that even with drastic fluctuations in medium temperature, the zero point and span temperature drift are controlled within a very small range. The pressure readings remain linearly stable throughout the entire heating and cooling process of the reaction kettle, guaranteeing precise triggering of overpressure shutdown and pressure relief interlocking.

4. Local digital display + remote automatic control dual output, facilitating operation and maintenance in high-temperature workshops

The integrated explosion-proof/ordinary digital display head allows for on-site direct reading of pressure during high-temperature pipeline inspections, eliminating the need to verify with the central control room. The buttons on the device enable zero point calibration and alarm threshold setting to be completed on-site, with quick adjustments after shutdown and pressure relief, eliminating the need to disassemble the instrument for inspection. The 4-20mA standard signal seamlessly interfaces with DCS and PLC, enabling real-time recording of the heat transfer oil circulation pressure curve.

5. High vibration resistance and protection, suitable for reaction kettle stirring and circulating pump vibration

The integrated laser-sealed and welded housing features multi-layer sealing to isolate high-temperature oil vapor and condensed water vapor from the workshop. The internal components are shock-absorbed and reinforced, ensuring that continuous vibration from the stirring equipment and hot oil circulating pump does not cause signal jitter, allowing for stable operation for 24 hours a day over the long term.

IV. Selection and implementation plan for different heat transfer oil reaction scenarios

 Small low-temperature reaction kettle, heat transfer oil ≤180℃

 The PTL512H 200℃ basic cooling model is chosen for its high cost-effectiveness and ability to meet conventional pressure monitoring requirements.

 General chemical heating system, mineral heat transfer oil at 200~280℃ (most commonly used)

 The standard configuration is the PTL512H 300℃ extended heat dissipation model, which is a universally applicable model in the industry and compatible with most resin, coating, and synthetic reaction heat transfer oil pipelines.

 High-temperature polymerization in fine chemical industry, synthesis of heat transfer oil at 280～350℃

 Upgrade to the PTL512H 350℃ isolated high-temperature model, featuring an extended cooling rod paired with high-temperature filling fluid to isolate ultra-high-temperature media.

 Flammable and explosive heat-conducting oil reaction workshop

 The PTL512H explosion-proof high-temperature version is chosen, which combines high temperature resistance and explosion-proof dual safety attributes, meeting chemical safety supervision regulations.

V. Precautions for the use of high-temperature heat transfer oil instruments

 When installing the instrument, tilt the meter head upward and utilize the heat dissipation rod for natural cooling. It is prohibited to place the meter head in close proximity to high-temperature pipelines or furnace walls;

 Under operating conditions where the medium temperature exceeds 320℃, the pressure guiding tube can be extended for natural cooling, further reducing the temperature at the pressure-bearing end of the instrument;

 Regularly clean the carbon deposits and oil stains on the membrane surface to prevent pressure conduction lag and numerical drift caused by the adhesion of carbon residue;

 It is strictly prohibited to use ordinary rubber-sealed transmitters, as high-temperature heat transfer oil infiltration can easily lead to leakage and fire risks;

 After replacing the heat transfer oil during each overhaul, perform zero calibration on PTL512H simultaneously to eliminate the baseline deviation caused by high-temperature carbon buildup.