Is it necessary to use a dual-thread differential pressure transmitter for measuring wind pressure (micro-pressure)?
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For pressure measurement in fluidized beds and kilns, the values are generally in the range of a few hundred pascals to 5 kilopascals. Some people believe that in such cases a differential pressure gauge with double threads is necessary in order to measure low pressures accurately; however, EJA and Rosemount suggest that if an accuracy of 0.5% is required, their gauges with single threads will suffice, allowing for cost savings of ten million per set. Does anyone have any insights on this? Thank you for your replies. The ones shown in the red box above are single-threaded models (EJA’s 530E and Rosemount’s TG series), while those below are double-threaded models (EJA’s 110E and Rosemount’s CG series). The latter ones are more expensive than the former ones.
It’s not called single-thread or double-thread; essentially, one is a pressure transmitter used for measuring gauge pressure, while the other is a transmitter for measuring differential pressure. In the case of the differential pressure transmitter, one end is also connected to the atmosphere. The difference is that the range of the differential pressure transmitter can usually be smaller, and its accuracy is also higher. Although the furnace pressure can range from a few hundred pascals to even several thousand pascals, it is generally kept within the range of dozens of pascals; using a differential pressure sensor is better for this purpose.
Your question concerns the selection of equipment for accurately measuring small pressure differences. Dual-thread differential pressure transmitters are often considered to have higher accuracy for measuring low pressures, and they exhibit greater resistance to environmental factors such as tearing and vibration, which can be important when dealing with processes in fluidized beds and kilns. However, single-thread differential pressure transmitters can also measure micropressures, as long as their accuracy meets your requirements. The key here is the requirement for precision and the project budget. Manufacturers such as EJA and Rosemount have self-sustaining products, and they tend to recommend their own equipment. If they recommend a differential pressure transmitter with a single thread that can meet your 0.5% accuracy requirement, it is undoubtedly an option worth considering. In this case, economic benefits become extremely important. For the products marked with a red box in your image, it can be seen that devices with dual threads are indeed quite expensive. This is because the manufacturing process for double threads is more complex and requires higher technical skills. If your budget is limited and single-threaded equipment can meet your needs, then single-threaded equipment is more suitable for you. In short, whether to use a dual-thread or single-thread differential pressure transmitter should be determined based on your specific requirements and budget. In some cases, a higher initial investment may yield long-term benefits due to its accuracy and stability. In other cases, a lower initial cost may also be the best option. .
Actually, what you call a single-thread gauge is also used to measure gauge pressure; the atmospheric pressure has already been deducted from it, but this value is fixed. The one with double threads is a differential pressure gauge; the high-pressure side is connected to the equipment via pressure lead pipes, while the low-pressure side directly measures the actual atmospheric pressure. This results in more accurate gauge pressure readings and higher precision.
To measure the pressure in a furnace, it is the correct choice to use a differential pressure transmitter; a gauge pressure transmitter is not suitable for this purpose. In the diagram shown by the original poster, the device used is a gauge pressure transmitter. Such transmitters have poor accuracy when measuring very small pressure differences compared to atmospheric pressure. The poster had better understand the principles and structure of pressure and differential pressure transmitters; otherwise, they will be laughed at by the people in the workshop.
I’m sorry; I work in the manufacturing field, and we don’t have any instrumentation engineers here. We have to proceed despite this difficulty. Thank you for your advice
If there are any uncertainties regarding the instruments, it’s good to ask the instrument engineers in the workshop; there are technicians available right nearby. Process and instrumentation should complement each other; problems should not be addressed with an attitude that treats these areas as completely separate from one another.
You’re absolutely right. I’ve left the factory floor and now work for a foreign-owned company; I started working in water treatment, but recently I’ve been involved in sludge drying and incineration. There’s no dedicated department for instrumentation, so I have to figure things out on my own
For several hundred Pa to several thousand Pa, use the second type of differential pressure. The first type of pressure sensor cannot measure differential pressure either. If two pressure transducers are used and their readings are subtracted from each other, the accuracy cannot be guaranteed at all. The accuracy of a single pressure transducer is acceptable, but there are deviations in the transmission of the two signals; the synchronization issue is quite severe.