Why does the food industry have to use high-temperature-resistant diaphragm pressure gauges？

The high-temperature resistant diaphragm pressure gauge is a precise pressure measurement instrument specially designed for industries with extremely strict hygiene requirements such as food, pharmaceuticals, and biotechnology. It combines the measurement functions of ordinary pressure gauges with the hygienic, corrosion-resistant, and high-temperature-resistant characteristics of the diaphragm sealing system.            
The core structure involves installing a diaphragm sealing system (commonly known as a "diaphragm clamp" or "flange") between the ordinary pressure gauge and the measured medium. The pressure is transmitted through a sealing liquid called "filling fluid" (such as silicone oil), so that corrosive, viscous or high-temperature food media do not directly contact the sensitive elements (Bourdon tube) of the pressure gauge, thereby protecting the instrument and ensuring the accuracy and hygiene of the measurement.   

In the food, beverage, pharmaceutical and bioengineering industries, these types of pressure gauges are commonly referred to as "hygienic diaphragm pressure gauges" or "sterile diaphragm pressure gauges". 

Special requirements for diaphragm pressure gauges used in the food industry            
In addition to the basic functions of high-temperature resistance and isolation, the core requirements of the food industry are: hygiene, easy cleaning, anti-contamination, and resistance to corrosion (including resistance to cleaning agent corrosion). 

1，Core Design and Features

Sanitary Design：            
·No blind spot design: The connection points between the instrument and the pipelines or tanks must be smooth and unobstructed, without any depressions or gaps that could accumulate materials or breed bacteria.            
·Surface finish: All parts in contact with the material (especially the diaphragm and connectors) must undergo high-precision polishing, typically requiring an Ra value of ≤ 0.8 μm or even ≤ 0.4 μm for a mirror-like effect. This not only facilitates cleaning but also prevents bacterial attachment.            
·Open-ended cleaning (CIP - Clean-in-Place): The instrument must be capable of withstanding the on-site cleaning (CIP) and on-site sterilization (SIP - Sterilize-in-Place) processes. This means it must be able to withstand the repeated impacts of cleaning agents at high temperatures and high pressures (such as caustic soda, acidic solutions), hot water, and steam. 

2，material requirements  

·Diaphragm material: The preferred material is 316L stainless steel. For highly corrosive foods (such as fruit juices, acidic beverages, salt solutions, etc.), Hastelloy C276 can be selected or a PTFE (polytetrafluoroethylene) coating can be applied on the 316L surface to ensure absolute inertness and prevent any reaction with the food or contamination of the product.            
·The material of the connecting parts: Also 316L stainless steel            
·Filling liquid: Food-grade silicone oil or fluorine oil must be used to ensure that even in extreme situations such as diaphragm rupture, the filling liquid will not pose a safety threat to the product.

3，standard interface    

For quick disassembly, assembly and cleaning, the common threaded connection is usually not adopted, but the internationally recognized sanitary quick-installation interface is used. The most common ones are:            
·Clamp Connection: such as DIN 11851 standard.            
·Threaded Connection: such as the SMS standard.            
·International standard quick assembly (Tri-Clamp Connection) : Such as ISO 2852 standard (the most commonly used), it is connected through one clamp and two sealing rings, and disassembly and cleaning are very convenient. 

4，Typical application scenarios            
·CIP/SIP system: Monitors the pressure of hot water, steam and chemical cleaning agents during the cleaning and sterilization processes.            
·Fermentation tank/reaction vessel: Monitor the pressure during the fermentation process while maintaining a sterile environment.            
·Filling equipment: Measure pressure on filling lines for beer, beverages, milk, etc.            
·Food processing pipeline: Pressure monitoring for pipelines transporting viscous or corrosive materials such as jam, syrup, oil, and dairy products.            
·Distillation and extraction equipment: Monitor the pressure of the high-temperature steam.

Selection Guide (For Food Industry)    
When you are selecting a model for the food industry, please be sure to make the following points clear to the supplier:            
·Medium properties: What kind of food material is it specifically? What is the pH value and viscosity of juices, milk, soy sauce, beer, etc.            
·Process temperature: What is the normal temperature of the material? What is the maximum temperature during CIP/SIP? The steam temperature of SIP often reaches over 130℃.            
·Pressure range: The required range.            
·Connection method: Confirm the device interface standard (the most important!)" Is it Tri-Clamp (ISO 2852), DIN 11851 or something else?            
·Material requirement: 316L is usually the default. When there are special corrosive media, it is essential to request PTFE coating or Hastelloy alloy.            
·Certification requirements: Are specific industry certifications required? Such as 3-A certification (a common standard for the food and drug industry in the United States) or EHEDG (European Sanitary Engineering Design Group) certification, etc.

Summary：

In summary: When choosing diaphragm pressure gauges for the food industry, "hygiene" is the top consideration. What you are looking for is not just a pressure gauge that can withstand high temperatures, but rather a key component that can integrate into a sterile production system, is easy to clean thoroughly, and does not contaminate the products. When making a purchase, be sure to choose brands and suppliers with experience in designing and manufacturing hygiene-level products.            
If you have specific application scenarios or selection questions, you can provide more information and I can offer you more detailed suggestions