FAQ
Answers to the most frequently asked questions
We place great value on personalized advice for each customer and on a trust-based collaboration. If your question is not answered here, please contact us personally.
FAQ
Flow Theories
Hört man den Begriff Massendurchfluss, so stellt man sich in der Regel Einheiten wie kg/h oder g/min und dergleichen vor. Betrachtet man jedoch die Praxis, stellt man fest, dass das Arbeiten mit Volumeneinheiten vorherrscht. Nun musste man sich nur noch auf Normbedingungen einigen, bei denen Masse in Volumen umgerechnet werden sollte.
Normbedingungen (ln/min): Als Normbedingungen wurden 0 °C und ein Druck von 1013,25 mbar absolut festgelegt. Gekennzeichnet werden die betreffenden Volumeneinheiten durch den tiefgestellten Buchstaben n: ln/min.
Standardbedingungen (ls/min): Eine weitere Festlegung zur Umrechnung von Masse in Volumen sind die Standardbedingungen, die auf 20 °C anstatt auf 0 °C bezogen sind und entsprechend mit einem s anstelle des n gekennzeichnet sind: ls/min.
Hinweis: International wird häufig die Angabe sccm (standard cubic centimeters per minute) und slm (standard liter per minute) benutzt, hier gilt die gleiche Definition wie für mln/min (0 °C, 1013,25 mbar abs).
Hinweis: Wird der Unterschied ln/min und ls/min nicht beachtet, resultiert hieraus ein Fehler von ca. 7%.
Sie können uns gerne Ihre Bezugspunkte nennen, Ihr Instrument wird dann dahingehend ausgelegt.
Diese Abkürzungen der Maßeinheiten der Massendurchflüsse, die mit einem „S“ beginnen, verweisen auf die üblichen Referenzbedingungen: 1013,25 hPa(abs) und 0 °C.
Hinweis: Referenztemperatur und Druckbedingungen der Durchflusseinheit der Instrumente werden immer auf dem Kalibrierzeugnis aufgeführt.
Die Messspanne oder der Regelbereich (engl.: Turndown ratio) eines Instrumentes gibt den Bereich an, in dem ein Durchflussmesser oder -regler eine Flüssigkeit genau messen kann. Mit anderen Worten: Es entspricht dem oberen Grenzwert eines Messbereichs im Vergleich zum unteren. Dies wird als Verhältnis ausgedrückt und mithilfe einer einfachen Formel berechnet:
Messspanne = maximaler / minimaler Durchfluss
Wenn ein bestimmter Durchflussmesser beispielsweise eine Messspanne von 50:1 hat, kann er den maximalen Durchfluss bis auf 1/50 genau messen. Angenommen, ein Durchflussmesser hat einen Skalenendwert von 20 ln/min, dann misst der Durchflussmesser den Durchfluss bis zum Ende des Bereiches von bis 0,4 ln/min. Behalten sie im Hinterkopf, dass der maximal bzw. minimal mögliche Durchfluss eines Messgeräts oder Reglers eine größere Messspanne als der einstellbare mess- und regelbare Bereich haben kann. So wäre es zum Beispiel möglich, dass ein Massendurchflussregler eine Messspanne von minimal 0,16 ln/min bis maximal 25 ln/min hat, der tatsächliche Messbereich aber von dem Reduzierverhältnis bestimmt wird. Auf dieses Beispiel bezogen heißt dies: Wenn der kalibrierte hohe Durchfluss 25 ln/min beträgt, entspricht der niedrigste messbare Wert 0,5 ln/min (1/50 von 25). Wenn die Anwendung erfordert, dass der kalibrierte minimale Durchfluss 0,1 ln/min beträgt, dann entspricht der messbare maximale Durchfluss 5 ln/min (50 Mal 0,1).
Bronkhorst hat eine Datenbank entwickelt, in der über 1800 Fluiddaten gespeichert sind. Mithilfe der Applikationssoftware können verschiedenste Berechnungen online auf unserer Website www.fluidat.com ausgeführt werden. Wir laden unsere Kunden ein, diese Website nach einer kostenlosen Anmeldung zu nutzen. Nach Erhalt Ihrer Zugangsdaten können Sie Konversionsfaktoren und Tabellen für thermische Gas- und Flüssigkeitsmesser von Bronkhorst, Kv-Werte und Öffnungsgrößen von Bronkhorst-Regelventilen, den Druckverlust von Coriolis-Durchflussmessern sowie Einlassfiltern berechnen und Berechnungen durchführen, die für Ihr CEM-Verdampfungssystem wichtig sind.
FAQ
Electrics
There is a wide variety of possibilities for electrical connection and communication. All Bronkhorst mass flow/pressure meters and controllers can generally be supplied with 15 or 24 Vdc. For analog inputs and outputs, 0-5 Vdc, 0-10 Vdc, 0-20 mA and 4-20 mA are optionally available. We can also offer other options on request.
The digital communication of most product lines includes RS232, PROFIBUS DP, DeviceNet™, Modbus-RTU/ASCII, EtherCAT®, PROFINET, CANopen, Modbus TCP, EtherNet/IP, Powerlink and FLOW-BUS (Bronkhorst® fieldbus).
We offer a variety of options for fieldbus interfaces that are integrated into the flow/pressure meter and controller. Typically, the additional current consumption for the interfaces is < 75 mA for instruments used at 15 V supply voltage and < 50 mA for instruments used at 24 V supply voltage.
Additional power consumption of onboard fieldbus interfaces
In the table you can see the exact values for each fieldbus type.
Fieldbus | with 15 V supply | with 24 V supply |
|---|---|---|
PROFIBUS DP | 53 mA | 30 mA |
PROFINET | 76 mA | 48 mA |
EtherCAT® | 66 mA | 41 mA |
CANopen® | n.a. | 48 mA |
DeviceNet ™ | n.a. | 48 mA |
EtherNet/IP | 51 mA | 35 mA |
Modbus-TCP | 51 mA | 35 mA |
POWERLINK | 51 mA | 35 mA |
Questions about measurement technology in general
Basics
Unlike mass-related units such as the gram, a measure of volume is always dependent on its ambient conditions. The volume changes when the temperature and/or pressure changes. If the temperature is increased, the space occupied by the medium increases. If the pressure increases, it becomes smaller. Consequently, when specifying a volume, the reference temperature and the reference pressure must always be specified.
If I enclose a liter of air at 0 °C and an ambient pressure of 1013.25 mBar, this is referred to as a standard liter in measurement technology. If the temperature is increased to 20 °C, the gas expands by 7.3 %. This is called a standard liter. Each industry sets its own standard.
If you measure the volumetric flow rate, this refers to the volume of a medium that moves per unit of time. The corresponding units are m3/h, m3/min, CFM or ACFM. If the medium is a gas, its volume expands depending on the temperature and pressure conditions. This must be taken into account when measuring the volume. However, the weight of a gas, i.e. its mass, does not change. The mass flow rate is the measure of the movement of a mass per unit of time. The units for mass flow are kg/h and lb/min.
The clearest reference pressure for pressure measurement is absolute zero (vacuum = 0 bar), which prevails in the vacuum of the universe. A pressure that is related to this reference pressure is called absolute pressure. With relative pressure, the reference pressure is not the zero point, but the actual ambient pressure (atmospheric pressure = 1 bar). A relative deviation of the air pressure from the ambient air pressure is called gauge pressure.
FAQ
Installation
What is FLOW-BUS?
FLOW-BUS is a fieldbus developed by Bronkhorst based on RS485 technology for digital communication between multiple digital devices. This communication protocol offers the possibility of host control by a PC.
What is FlowSuite?
FlowSuite is a Windows PC application for monitoring and servicing Bronkhorst digital instruments via a single interface in a multi-device window. It provides a good insight into the dynamic behavior of the flow meters and controllers.
How to connect FLOW-BUS and FlowSuite in practice?
Bronkhorst instruments are equipped with a micro-controller to exchange parameter value information with other devices connected to the same FLOW-BUS system or via RS232 to a PC.
Here are some examples of how to correctly install Bronkhorst instruments using FLOW-BUS with FlowSuite:
- Bronkhorst instruments are connected via FLOW-BUS, RS485 (red cable).
- The USB port of the PC is connected to the first instrument via RS232 (green cable).
- Bronkhorst FlowSuite™ displays the PV (process variables), controls the SP (set point), together with graphing and data logging for up to 4 graphs. The number of instruments to be connected depends on the performance of your hardware.
- A standard RJ45 shielded (F)TP patch cable or an M12 cable supplies the FLOW-BUS signal and the 24 Vdc voltage.
- 1A @ 24Vdc or 24 watts is the maximum power for RJ45 Shielded (F)TP patch cables, 4A for the M12 cables.
Digital multi-bus instruments (operated via the analog interface) are pin-compatible with Bronkhorst analog instruments.
Note: If you have previously set the instrument to a setpoint via a potentiometer, please let us know when you make your request. We can offer you an adapter for this operating mode. The same applies to instruments with circuit board coding HC, HD, FC and FD.
The measured values are always available simultaneously as analogue and RS-232 signals. The setpoint specification can be either analogue or via RS-232. This must be configured beforehand.
Gas properties vary according to temperature and pressure fluctuations. The EL-FLOW Prestige thermal models use the actual measurement temperature (and pressure, if applicable) for the on-board calculation of fluid properties in real time. For this reason, these devices have an embedded database in which gas properties are stored (“Fluidat-On-Board”).
The following gases are included:
EL-FLOW® Prestige models built until Dec. 2018 | EL-FLOW® Prestige models built from Jan. 2019 |
|---|---|
formula | designation | formula | designation | formula | designation |
|---|---|---|---|---|---|
Air | Air | Air | Air | CH3CI | Chloromethan |
AR | Argon | AR | Air | CH3F | Fluoromethan |
C2F6 | Freon-116 | AsH3 | Arsin (Arsan) | CH4 | Methan |
C2H2 | Acetylen (Ethin) | B2H6 | Diboran | CH4S | Methanthiol |
C2H4 | Ethen | BCI3 | Bortrichlorid | CH5N | Methylamin (Aminomethan) |
C2H6 | Ethan | BF3 | Bortrifluorid | CHCl2F | Dichlorofluoromethan |
C3H6 #2 | Propen | C2CI2F4 #2 | Freon-114 | CHClF2 | Chlorodifluoromethan |
C3H8 | Propan | C2Cl3F3 | Freon-113 | CHF3 | Freon-23 |
CH4 | Methan | C2ClF5 | Freon-115 | Cl2 | Chlor |
Cl2 | Chlor | C2F4 | Perfluoroethen | ClCN | Cyanchlorid |
CO | Carbon monoxide | C2F6 | Freon-116 | ClF3 | Chlortrifluorid |
CO2 | Carbon dioxide | C2H2 | Acetylen (Ethin) | CO | Carbon monoxide |
H2 | Hydrogen | C2H2F2 #1 | Freon-1132A | CO2 | Carbon dioxide |
H2S | Hydrogen sulphide | C2H3Br | Vinylbromid | COCl2 | Carbonylchlorid |
He | Helium | C2H3Cl | Chloroethen | COF2 | Carbonylfluorid |
Kr | Krypton | C2H3F | Fluoroethen | COS | Carbonylsulfid |
N2 | Nitrogen | C2H4 | Ethen | CS2 | Carbon disulphide |
N2O | Nitrous oxide (laughing gas) | C2H4O #2 | Epoxyethan | D2 #1 | Deuterium |
NF3 | Nitrogen trifluoride | C2H5Cl | Chloroethan | F2 | Fluorine |
NH3 | Ammonia | C2H6 | Ethan | GeH4 | German |
NO | Nitric oxide | C2H6O #1 | Dimethylether | H2 | Hydrogen |
O2 | Oxygen | C2H7N #2 | Dimethylamin | H2S | Hydrogen sulphide |
SF6 | Sulphur hexafluoride | C2H7N #3 | Monoethylamin | H2Se | Hydrogen selenide |
SiH4 | Silan | C2N2 | Dicyan (Ethandinitril) | HBr | Hydrogen bromide |
– | – | C3F8 | Perfluoropropan | HCl | Hydrogen chloride |
– | – | C3H4 #1 | Allen | HCN | Hydrogen cyanide |
– | – | C3H4 #2 | Methylacetylen | He | Helium |
– | – | C3H6 #1 | Cyclopropan | HF | Hydrogen fluoride |
– | – | C3H6 #2 | Propen | HI | Hydrogen iodide |
– | – | C3H8 | Propan | Kr | Krypton |
– | – | C3H9N #3 | Trimethylamin | MoF6 | Molybdenum hexafluoride |
– | – | C4F8 | Freon-C318 | N2 | Nitrogen |
– | – | C4H10 #1 | n-Butan | N2O | Nitrous oxide (laughing gas) |
– | – | C4H10 #2 | Isobutan | Ne | Neon |
– | – | C4H6 #3 | 1,3-Butadien | NF3 | Nitrogen trifluoride |
– | – | C4H6 #4 | 1-Butin | NH3 | Ammonics |
– | – | C4H8 #1 | Cyclobutan | NO | Nitric oxide |
– | – | C4H8 #2 | 1-Buten | O2 | Oxygen |
– | – | C4H8 #3 | Buten (2-) (cis) | OF2 | Oxygen difluoride |
– | – | C4H8 #4 | Buten (2-) (trans) | PH3 | Phosphin |
– | – | C4H8 #5 | 2-Methylpropen | SF4 | Sulphur tetrafluoride |
– | – | C5H12 #2 | 2,2-Dimethylpropan | SF6 | Sulphur hexafluoride |
– | – | C5H12 #3 | n-Pentan | Si2H6 | Disilan |
– | – | CBr2F2 | Dichlorodifluoromethane | SiH2Cl2 | Trichlorosilan |
– | – | CCl3F | Fluorotrichloromethan | SO2 | Sulphur dioxide |
– | – | CClF3 | Chlorotrifluoromethan | WF6 | Tungsten hexafluoride |
– | – | CF4 | Carbon tetrafluoride | Xe | Xenon |
– | – | CH3Br | Bromomethan | – | – |
Electronic pressure regulators are often used to precisely control the pressure in a process chamber or to regulate the pressure in your system. Such a pressure regulator controls a control valve, allowing the pressure in the process chamber to be increased. To reduce the pressure again, vent valves are often used to ensure continuous venting to the environment.
However, this solution is not recommended for expensive or hazardous process gases. In this case, an additional valve with a valve control unit is often used to regulate the venting. These additional components make the system very complex. The process pressure regulator of the P-800 series combines both functions, i.e. it has an integrated venting valve and a venting valve, which reduces the number of components and avoids continuous venting into the environment. The advantages at a glance:
The following gases are included:
Conventional solution with venting to the atmosphere | Process pressure regulator |
|---|---|
– Higher gas consumption due to constant venting – Not suitable for hazardous gases | – Low gas consumption – Safe solution for all gases |
Conventional solution with separate relief valve | Process pressure regulator |
|---|---|
– Connection of different components requires more space – Purchase, assembly and testing of different components is less efficient and more expensive | – Compact, integrated solution – Economical “plug-and-play” solution |
Questions about testing the devices
Calibration
If you click on the link below, you can open an example calibration certificate with explanations of the different sections.
All process instruments are subject to wear and tear due to the process conditions to which they are exposed. Temperature, changes in electronic component tolerance, contamination that accumulates over time and other factors affect accuracy. Your instruments should therefore undergo at least one calibration check, if not recalibration, on a regular basis.
As all applications are different, Bronkhorst does not provide specific due dates for calibration of its instruments. We recommend an annual calibration of the devices. Based on a company’s application conditions and possibly quality assurance procedures, it is up to each customer to determine when to send an instrument in for recalibration. Properly calibrated instruments are more accurate and reliable, ensuring consistency and helping to improve production yields. On-site testing can reduce downtime and costs.
In general, operation with other media is also possible. However, it is important to ensure that the sealing material used is suitable for the new gas or liquid beforehand. In addition, a conversion factor must be used when using a thermal mass flow meter, as the thermodynamic properties of the various media differ. Another influencing factor is the Kv value of the valve. The use of a different medium can significantly change the flow range for which the instrument was designed.
In contrast to thermal mass flow meters, flow meters based on the Coriolis or ultrasonic measuring principle are independent of the medium and do not require a conversion factor. However, if a liquid flow meter is switched to a different medium, the pressure loss may change.
Yes, Bronkhorst instruments can be adapted. After adaptation, the flow meter is recalibrated. The instrument limits must of course be taken into account. We offer repairs and recalibrations throughout Austria.
It is possible to calibrate an instrument by checking the measured value yourself using an exact reference value. It is also possible to restore the function of instruments if no parts are irreversibly damaged. However, this may affect the accuracy of the instruments.
Please note that once an instrument has been opened, the factory calibration and pressure and leak test are no longer valid. Bronkhorst cannot accept any warranty for instruments that have not been opened by certified service partners such as AcuraSens, but by third parties.
In general, we recommend contacting our technical team for repair, cleaning and calibration of contaminated or defective instruments.
Adjusting the measurement signal means that we can adjust the settings of the measuring device to the values of the reference device used. This is to rule out systematic measurement deviations.
Matching is important if the output signal of the measuring device is not only expected to be repeatable, but also to measure the true value. Instead of adjusting the meter, the end user can also use the deviation listed on the calibration certificate to make an adjustment in the computer.
As-found calibration
An as-found calibration is a calibration that is performed before a repair or adjustment. It is often performed when a flow meter has been returned to a service center. This calibration determines the condition the flow meter is in when it is received. On the other hand, there is the as-left calibration.
As-left calibration
The as-left calibration is a calibration that is carried out after a repair or adjustment. It confirms that repairs or adjustments have been successful.
All instruments we offer are calibrated according to ISO 9001. The standard calibration according to this standard is included in the purchase price. It is possible to perform an additional calibration according to ISO 17025 on request.
The specification limit is the maximum permissible value of a measurement deviation. This can be either a positive or a negative deviation.
Questions about our service
Service
You can reach our service team either by e-mail at service@acurasens.com or, in emergencies, by telephone at
on +43(0)662 439484-10. We respond reliably within 24 hours.
Each customer decides for themselves whether and how often they want to send their appliances in for a service. We are happy to provide individual plans and take care of the process. In the event of problems such as deviations or malfunctions, our technical team will carry out a telephone analysis in advance and then decide whether the appliance needs to be sent in or whether an on-site service is possible.
A service always starts with an analysis and a cleaning of the instruments. We clarify any malfunctions and decide whether and how they can be rectified. In any case, the customer must submit a declaration of decontamination in advance.
A declaration of decontamination is used to document all safety-relevant information for the return of instruments and components. The customer is responsible for the health and safety of everyone who may have contact with a returned device. This responsibility extends from the customer’s own personnel to the shipping company and the entire AcuraSens and Bronkhorst team. Any contamination of the device must be identified, even if it has been removed. You can download the decontamination declaration here:
You will receive a cost estimate based on a device analysis carried out by our technicians before each service. AcuraSens offers its customers a three-year warranty on all components.
Calibration is the process of checking the accuracy of a device. In short, calibration is the comparison of the output to a reference. This regular check is important because devices are subject to wear and tear due to process conditions, which can lead to small deviations over time. For some applications, this regular check is even required by law or guidelines. Regular calibration can prevent malfunctions and demonstrably increase the efficiency of a system.
The calibration itself takes a maximum of one hour per device. In the case of on-site calibration, the actual duration depends on how accessible the instruments are to our technicians. For a calibration at our AcuraSens headquarters in Lenzing, the duration of the postal route must be taken into account. We can calibrate most of the instruments ourselves, we only very rarely have to send instruments to Bronkhorst.
Yes, customers can book us for an on-site calibration. From a certain number of devices, this option is even more efficient and cheaper than dismantling and sending in the devices yourself. What is important: For an on-site calibration, we need a test specimen and a reference device. There must also be an area in which our technicians can install the measuring device.
Yes, we are happy to provide your team with advice and ideas over the phone. We offer this form of support free of charge. Please make an appointment and contact service@acurasens.com.
Questions about technical problems
Technology
You can find the type of seal in the following table:
model – series | Sealing surface |
|---|---|
EL-FLOW Base | BSPP RS-type based sealing surface |
EL-FLOW Prestige | BSPP RS-type based sealing surface |
EL-FLOW Select | BSPP RS-type based sealing surface |
LOW-dP-FLOW | BSPP RS-type based sealing surface |
EL-PRESS | BSPP RS-type based sealing surface |
EX-FLOW | BSPP RS-type based sealing surface |
IN-FLOW | BSPP RS-type based sealing surface |
IN-PRESS | BSPP RS-type based sealing surface |
LIQUI-FLOW | BSPP RS-type based sealing surface |
MASS-STREAM D-6300 | BSPP RP-type based sealing surface |
MASS-STREAM D-6400 | BSPP type ISO 1179-1 flat sealing surface |
MASS-VIEW | BSPP type ISO 1179-1 flat sealing surface |
FLEXI-FLOW | BSPP type ISO 1179-1 flat sealing surface |
IQ+FLOW | 10-32 UNF Class 2B sealing surface |
EL-FLOW Metal | no sealing surface – welded or part of the body |
EL-PRESS Metal | no sealing surface – welded or part of the body |
ES-FLOW | no sealing surface – welded or part of the body |
µ-FLOW | no sealing surface – welded or part of the body |
(mini) CORI-FLOW | no sealing surface – welded or part of the body |
IN-FLOW/EX-FLOW F-107/117 | no sealing surface – welded or part of the body |
IN-FLOW/EX-FLOW F-106 | F-106 no sealing surface – wafer type |
IP-Rating
The IP-rating of an instrument consists of the letters IP (abbreviation for “Ingress Protection”) followed by two code numbers and an optional letter. As defined in the international standard IEC 60529, it classifies the degree of protection against the ingress of solid foreign bodies including body parts such as hands and fingers, dust and against accidental contact (the first digit after IP) as well as water (the second digit after IP) in electronic housings.
First digit: Protection against solid foreign bodies
Digit | Protection against solid foreign bodies |
|---|---|
0 | No protection |
1 | Protected against solid foreign bodies with a diameter of 50 mm or more, access with the back of the hand |
2 | Protected against solid foreign bodies with a diameter of 12.5 mm or more, access with one finger |
3 | Protected against solid foreign bodies with a diameter of 2.5 mm or more, access with a tool |
4 | Protected against solid foreign bodies with a diameter of 1.0 mm or more, access with a wire |
5 | Protected against dust in damaging quantities, complete protection against contact |
6 | Dust-tight, complete protection against contact |
Second digit: Protection against liquids
Digit | Protection against solid foreign bodies |
|---|---|
0 | No protection |
1 | Protection against vertically falling dripping water |
2 | Protection against dripping water if the housing is inclined up to 15° |
3 | Protection against falling spray water up to 60° against the vertical |
4 | Protection against splashing water on all sides |
5 | Protection against water jets (nozzle) from any angle |
6 | Protection against strong water jets |
7 | Protection against temporary immersion between 15 cm and 1 m |
8 | Protection against permanent immersion |
NEMA-Rating
The US National Electrical Manufacturers Association (NEMA) also publishes protection values for enclosures that are comparable to the IP protection system of the International Electrotechnical Commission (IEC). However, NEMA also prescribes other product characteristics that are not covered by the IP codes, such as corrosion resistance, the ageing of seals and construction techniques.
Therefore, while it is possible to equate IP codes to NEMA classifications that meet or exceed the IP code criteria, it is not possible to equate NEMA protection classes to IP codes because the IP codes do not provide for the additional requirements.
IP-Code | min. NEMA protection classes of enclosures to comply with the IP Code |
|---|---|
IP20 | 1 |
IP54 | 3 |
IP65 | 4, 4X |
IP67 | 6 |
IP68 | 6P |
The standard material used in the manufacture of all Bronkhorst instruments is 316 stainless steel or equivalent. On request we can also offer some wetted parts in Monel or Hastelloy.
The instruments of the MASS-STREAM, FLEXI-FLOW and IQ+FLOW series are also available in aluminum. Standard seals for thermal mass flow meters and controllers for gases are made of Viton® (FKM) and for thermal mass flow meters and controllers for liquids of Kalrez® (FFKM). (mini) CORI-FLOW Coriolis mass flow meters are metal sealed.
The regulators include internal seals made of Viton® (FKM) (factory standard), EPDM or Kalrez® (FFKM). The sealing materials can also be supplied with FDA certification.
The choice of suitable elastomer seals must be based on chemical resistance under the relevant operating conditions. We are happy to advise our customers on the selection of suitable gaskets. However, our recommendations are to be regarded as guidelines for which no guarantees can be given.
Bronkhorst uses compression or vacuum fittings (VCR/VCO) with BSPP threads as standard for its instruments. BSPP (British Standard Pipe Parallel) is a parallel fitting. The screw threads are used to hold the two pieces together and not to create a seal.
Sealing is achieved using an elastomer seal outside the thread. As the seal is made outside the thread, there is no risk of foreign bodies in the threads being forced into the gas flow path. For this reason, we do not recommend NPT fittings with PTFE sealing tape.
