No, the absolute pressure transmitter ranges from 0 mbara. A negative mbara value is not a valid input in pressure transmitters.
TPE is the square root of the sum of all the effects to the power ²; for diaphragm seals this encompasses: TPE= √((ProcT-Effect²)+(AmbT-Effect²)+(Mtg-Effect²)+(Acc²)+(StatP-Effect²)) (the last Static Pressure Effect obviously only for dP applications)
BF/BC have the diaphragm weld as a wetted part, this would lead with dissimilar materials to corrosion and/or weld strength problems. BRF/BRC have the diaphragm resistance welded to the body, which result in a weld as a non-wetted part, so allowing to create full wetted parts in exotic materials.
Accuracy is the uncertainty of the measurement of an instrument under laboratory conditions i.e. @ 20°C ±1°C. Total Probable Error (TPE) is the maximum deviation of the measurement including all effects of process and ambient temperatures and pressures and installation. In the vast majority of the applications the accuracy of the instrument is only a very minor part of the TPE. In this respect it is only sensible to consider the TPE whilst engineering a measurement application.
In order to guarantee corrosion protection, the polymer coatings must have a thickness of ≥ 1 mm. At that thickness the diaphragm flexibility is completely gone and thus no measurement anymore possible. The thickness of the polymer coatings on diaphragm seals varies from 30 – 80 µm. At that thickness the coating only serve as a protection against sticking of the process to the diaphragm.
Having said this, in reality, in some specific situations, it is know that some polymer coating may offer a certain enhanced corrosion protection.
Renowned large international end-users a.o. in petrochemical industries have defined that for regular monitoring and control applications a TPE of 5% is acceptable. There is no standard that defines that
Yes. For gold plating on AISI316L diaphragm in combination with AISI 316(L) flanges the temperature limitation is 430°C. For non AISI 316 constructions such as Alloy C276 or 625 the plating process require a different approach that leaves a risk of adhesion problems. The maximum allowed continuous process temperature is set at 275°C.
The difference between balanced and unbalanced system is the use of equal capillary systems on both sides of the transmitter. It is possible to have a direct mount or wet leg situation in combination with capillary on the other side of the transmitter. The unbalanced system has temperature errors due to the different fill fluid volume at HP & LP side and thus unreliable performance once installed in the filed hence we strongly recommend to use balanced capillary system for reliable measurement. Calculations to see the differences can be done with Basecal perfomance calculation tool.
A full weld construction is a diaphragm seal application where all potential leak point are welded. This includes fill holes, threaded connections, and gasket area’s. Badotherm is specialized in welding special cups on transmitter cells without compromising the functioning and accuracy of the transmitter. The Badotherm design of the full weld construction allows a full repair option when the any failure occur. When repairing the weld cup is removed from the transmitter in order to clean and visual inspect the transmitter cell.
The full weld construction is advised to be used in full vacuum applications, application with big temperature fluctuations, or high pressure applications as these circumstances are known for potential leakage through fitted connections or connections sealed with gaskets. Badotherm full welded construction is repairable and available with almost all transmitter brands.
None. RTJ and RJF are the same however as per ASME B16.5-2020 RJF relates to flanges and RTJ relate to the gasket hence RJF is the correct terminology for flange facing. This terminology is used by Badotherm.
Flat facing is over the full body of the seal and same as the gaskets. The flush ring only covers small portion of the gasket area of the blind flange seal and gasket. So, the principle of FF is not followed anymore. By using a flush ring there is a greater chance of leakage hence we recommend a flush flange (with bolt holes like a blind flange) with FF or Type A facing, instead of a flush ring.
In case of vacuum < the minimum allowed pressure of the pressure transmitters; the transmitter shall be mounted min. 500 mm below the (lowest) diaphragm seal in order to create sufficient static height, to protect the transmitter from irreversible damage
The span in this particular case is 0+4 bar, and that is the span at which we will calibrate the DP transmitter.
The settings of transmitter will be -2+2 bar, however the calibrated span 0+4 bar will be mentioned on the calibration certificate.
Modern chemical processing and process manufacturing procedures demand ever greater accuracy and reliability from their pressure, level and flow measuring instruments. This is important to minimise costs, and to keep production downtime and shut downs to an absolute minimum. In various situations it is necessary to isolate and therewith protect the pressure measuring instrument from the process medium in order to maintain the required accuracy and reliability objectives. This isolation or separation of the instrument and the process is typically done by means of Diaphragm Seals, to protect the vulnerable measuring instrument. This protection enhances the lifetime of the measuring instrument significantly.
Before the start of any project related to the pressure, level and flow applications one should understand the possibilities of Diaphragm Seals. Badotherm’s expertise and experience are there to ensure that the right solutions are offered to meet the needs from the start and prevent any problems at a later stage. When Diaphragm Seals are needed the material characteristics, operating conditions for the instruments, and choice of mounting should be taken into account.
Diaphragms are mounted in different variations to the pressure instruments in order to meet the specific situation in the plant. Multiple variations are possible in each situation. The challenge is to select the variant that has the most advantages in the light of accuracy, accessibility of the instruments, and maintenance. The most common instrument mounting configurations are a direct mount and a remote mount pressure instrument. When direct mounted the instrument is directly connected to the diaphragm seal by means of a rigid threaded nipple or welded to the diaphragm seal directly.
Remote mounted instrument uses a flexible capillary line between the diaphragm seal and the pressure instrument. When having DP measuring principle where two diaphragm seals are mounted the two instrument mounting variations can be combined where the high side (+) is direct mounted, and the low side (-) is remote mounted.
Harsh process conditions, high or low process temperatures, hygienic and sanitary environments, viscous or abrasive processes, vent and flush possibilities are only a few specifications seen in the industry. For all these conditions and much more Badotherm has options, materials, coatings and linings available. Each having their own specifications and limits. The main categories in the protective layers are polymer coatings, gold/silver coatings, linings, or PTFE sheets. All categories has their own specifications, chemical resistance and thus field of application.
Pressure instruments come in may forms and principles. Depending on the process to be measured the pressure instrument and the measuring principle is selected. Most of the pressure instruments are suitable to mount diaphragm seals or accessories. This allows the used to expand the field of applications. A pressure instrument combined with one of the diaphragm seals makes a diaphragm seal system.
The pressure instruments makes it possible to get the reading of the process pressure. Most types of pressure instruments can be mounted and filled with Badotherm diaphragm seals. Years of experience learned that standard
– pressure transmitters
– pneumatic transmitters
– pressure switches
– and pressure gauges
are suitable to mount diaphragm seals to. Of course, for each instrument, we need to take into account specific limitations of the instrument to engineer and select the best suitable diaphragm seal type, construction and filling fluid.
Instruments with Diaphragm Seals can be mounted in various positions. In a differential pressure measurement the instrument can be mounted between the nozzles, but the instrument can also be mounted above the highest or below the lowest nozzle. Also in a gauge pressure measurement the instrument can be mounted in various positions compared to the Diaphragm Seal.
Diaphragm seal systems are mounted to the process to measure pressure, level or even flow. This is done on pressure vessels, transportation pipes, or perhaps a distillation column. Each style requires a different configuration and location of the pressure instrument in order to use the physics of fluid columns in the advantage of the measurement. Positioning the pressure instrument below or above the nozzle can have big effect of the functioning and lifetime of the diaphragm seal system.
The mounting of the instrument is important to ensure the best possible measurement in the given circumstances. The specific gravity of the vertical fill fluid column between the instrument and the Diaphragm Seal is influenced by the ambient temperature deviation. These influences create a pressure variation within the Diaphragm Seal System. This is called the mounting effect.
