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Q: What is the purpose of the ventable & non-ventable fill plug/relief plug?
A: A fill plug seals the fill hole in a pressure gauge case. On liquid filled pressure gauges, a ventable fill plug is used to relieve internal case pressures that occur due to thermal expansion of the fill fluid. In non-filled dry gauges, a non-ventable fill plug is used to occasionally drain the interior of the case from condensate or relieve internal case pressures. Ventable fill plugs incorporate a vent pin to open and close a hole for relieving internal case pressures and do not have to be removed from the case hole like non-ventable fill plugs.
Q: What are the designed overpressure ratings for XRT gauges?
A: Overpressure ratings are specific to the gauge type, pressure range and accuracy ratings of the gauge. When selecting a pressure gauge, it is recommended that the normal system pressure be maintained around 2/3 of the full range of the gauge as to avoid overpressure conditions.
Q: How often does a gauge need to be calibrated?
A: According to international standards, the calibration cycle for pressure gauges is typically recommended to be once a year. If the pressure gauge is used in harsh environments, such as those with vibrations, significant temperature fluctuations, or corrosive substances, more frequent calibration may be necessary. For applications that require extremely high accuracy of pressure readings, a shorter calibration cycle, such as every six months, might be needed. In all cases, the environmental limitations specified for the pressure gauge series should be observed. Therefore, the frequency of calibration is best determined by the user based on actual conditions.
Q: When is a diaphragm seal used, and when would you apply a diaphragm seal and capillary?
A: A diaphragm is used to isolate and protect the instrument from the process media. Damaging process media may include corrosives, particulates, temperatures, or any state that is not suitable for direct contact with the measuring element. Diaphragms indirectly transmit system pressures by segregating the process pressure with a thin flexible membrane that in turn transfers the pressure through a fill fluid to the instrument. Diaphragms are often used in conjunction with capillaries to further distance the instrument from the process media. Capillary tubes transmit the diaphragm fill fluid to the instrument. Capillary tubes come in several lengths and provide the user a means to measure in a remote location and may also act as heat dissipaters in high temperature applications.
Q: What is the purpose of liquid filling a gauge, and in what applications would a liquid filled gauge be used?
A: Primarily, in applications that have vibrations or pulsations, liquid filling enables reading the dial pointer by dampening the movement. Liquid filling should be considered in any system that has high dynamic operating conditions. In general, liquid filling helps extend the life of a gauge. It reduces damaging resonance induced fracturing, reduces frictional wear, prevents aggressive ambient air from entering, prevents condensation formation, and improves reliability.
Q: How does temperature affect the accuracy of a pressure gauge?
A: Temperature changes affect the stiffness of a bourdon tube. The stiffness change is produced by a combination of changes in the elastic (Young’s) modulus and a change in linear dimensions due to linear expansion and contraction. The error caused by temperature change will follow the approximate formula:
± 0.04 x (t2 – t) % of the span.
Q: How do you size a pressure gauge relative to process pressures, normal operating pressures, and maximum pressures in the process? (Dynamic or static process pressures)
A: The pressure range of a gauge should be a minimum of 10% over the maximum working pressure in static conditions (no pressure fluctuations). In dynamic conditions, the gauge range should be a minimum of 40% over the maximum working pressure. Ideally, the pressure gauge range should be selected for a midscale reading during normal operating pressures.
Q: What does a gauge accuracy statement really mean? (Examples: 1.6% of span)
A: Accuracy is the difference between the true value and the gauge indication expressed as a percent of the gauge span. It is determined by comparing a gauge indication to a known standard or certified true value and combines the effects of method, observer, apparatus, and environment. Accuracy error also includes hysteresis and repeatability errors. For example, “1.6% of span” indicates that the reading error of the pressure gauge will not exceed 1.6% of the full scale range throughout the entire measurement range.
Q: In what situation would a pigtail syphon be used?
A: Pigtail syphons should be used in steam applications and systems that contain superheated vapor. The pigtail buffers the instrument from the damaging effects high temperature steam by holding system fluid in the coil to provide a steam trap for the fluid to condensate and dissipate the heat.
Q: What fill fluids options are available, and in what applications would each be used?
A: Glycerin is the most common fill fluid. Because of its unique fluid properties, Glycerin has become the standard for liquid filled gauges (see “What is the purpose of liquid filling a gauge?”). Glycerin’s clarity, viscosity, stability, cost, solubility, low toxicity make Glycerin an ideal fluid for many applications. Mineral oils and silicone fluids are used when temperature extremes, chemical compatibility or viscosity fall outside of Glycerin use. Halocarbon is an inert fluid that is compatible with chlorine, oxygen service some high temperature applications. Keep in mind that Glycerin is not compatible with strong oxidizers such as oxygen, chlorine, hydrogen peroxide, or nitric acid. Glycerin & Silicone are explosive in contact with chlorine. Halocarbon is explosive in contact with aluminum and magnesium.
Q:How does a Bourdon tube pressure gauge measure pressure?
A:Fluid like air or water goes through the process connection and up into the Bourdon tube. As pressure inside increases, the tube straightens out. A gear transfers the motion to the dial pointer. In fancy engineering terms, the tube deflects, and the movement converts that deflection into a rotary movement of the pointer.
Q:What is the difference between a transducer and transmitter?
A: When these terms originated there was a distinctive difference between the two. A transmitter was referred to as an instrument with a current signal (i.e. 4 mA to 20 mA) and a transducer was referred to as an instrument with a voltage signal (i.e. 0 Vdc to 10 Vdc). As time has progressed these terms are now commonly interchanged for reference to either output signal.
Q:How to choose the appropriate transmitter range?
A:Selecting the appropriate transmitter range is crucial to ensure measurement accuracy and system safety. To correctly choose the range, first consider the actual operating pressure range to ensure that the selected range can cover both the lowest and highest working pressures with sufficient safety margin. Typically, it is recommended that for static applications, the range should exceed the maximum working pressure by at least 10%, whereas for dynamic or pulsating pressure applications, this margin should be over 40%. Moreover, the ideal normal operating pressure should fall within approximately one-third to two-thirds of the range to ensure optimal accuracy. Consideration must also be given to potential extreme conditions such as instantaneous overpressure or the impact of temperature changes on pressure, as well as the possibility of future system expansion. Finally, in conjunction with the technical specifications of the transmitter, such as linearity, repeatability, and long-term stability, determine the most suitable range setting for the application scenario. This approach not only enhances measurement reliability but also extends the service life of the transmitter.
Q: What does RFI, EMI and ESD mean related to pressure transducers and transmitters?
A: Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) refer to the effects electrical noise can have on instruments. RFI frequently comes from hand held walkie-talkies and EMI comes from AC motors in the vicinity of the instrument. ESD (Electrostatic Discharge) comes from many sources including the application itself. CE compliant transmitters and transducers incorporate protection techniques and components to minimize most of the interference.
Q: Can traditional diaphragm seals or gauge protectors be used with pressure transducers and transmitters?
A: Most diaphragm seals can be used with pressure transducers and transmitters. The real key is to assemble and fill the seal properly, being careful not to entrap air in the fill fluid.
Q: Are pigtail steam syphons used in transmitter applications?
A: The steam syphon is necessary in steam pressure applications. It is important to isolate the transmitter sensing diaphragm from the high temperature encountered with steam pressure applications.
Q: What is the reason for the vent tube in the cable of the series 612 and 627 submersible level transmitters?
A: All pressure measurements are inherently differential in theory. Gauge pressure is referenced to ambient atmospheric, absolute pressure is referenced to vacuum contained in an evacuated chamber within the transmitter. The level measurement is also a differential measurement, with its reference to ambient atmospheric pressure. In order for the submersible level measurement to be referenced to atmospheric, the cable contains a vent tube which runs the complete length of the cable and “vents” into the atmospheric pressure at the junction box connection which is out of the liquid.
Q: What is a turndown ratio?
A: A turndown ratio is also commonly known as rangeability, and refers to the ratio between the full-scale range and the minimum point of measure, indicating the range in which an instrument can accurately measure the media. Example: a pressure transmitter has a maximum calibration range of 0 to 300 psi, and a turndown ratio of 10:1. This means that the span can be adjusted anywhere between 0 to 30 psi and 0 to 300 psi. The higher the turndown ratio, the higher the rangeability, which can also minimize required inventory.
Q:What are the common output signal types for transmitters?
A:Common output signal types for transmitters include:Analog Current Signals (such as 4-20mA, which is suitable for long-distance transmission and applications requiring high immunity to electrical noise).Analog Voltage Signals (such as 0-5V or 0-10V, ideal for short-distance applications that demand high precision).Digital Communication Protocols (like HART, Modbus, Profibus PA, Foundation Fieldbus, etc., which support bidirectional data exchange, enabling remote configuration, diagnostics, and multi-variable transmission, making them particularly suitable for integration into modern automation systems).Selecting the appropriate output signal type depends on specific application requirements, including measurement range, environmental conditions, transmission distance, and system compatibility factors.
Q:What is the importance of the Ingress Protection (IP) rating?
A:The importance of the Ingress Protection (IP) rating lies in its direct relevance to the reliability and durability of transmitters under various environmental conditions. The IP rating is a standard established by the International Electrotechnical Commission (IEC) to clearly define an electrical device’s protection against intrusion by solid objects and water. For transmitters, selecting the correct IP rating ensures they can operate normally without damage in specific working environments such as outdoors, humid areas, dust-heavy locations, or corrosive settings. For instance, in places with high humidity or where frequent water washdowns occur, transmitters with higher water resistance ratings are necessary; whereas in environments containing large amounts of dust or other particulates, transmitters that can prevent these substances from entering their interiors should be chosen. An appropriate IP rating not only protects the transmitter from external factors, extending its service life, but also reduces maintenance needs and ensures stable system operation. Therefore, considering the proper IP rating based on the actual application environment is critical when selecting a transmitter.
Q: What is the maximum temperature rating on a bi-metal thermometer by itself?
A: Maximum temperature for a bi-metal thermometer in continuous use is 800°F but can be used in applications intermittently up to 1000°F.
Q: What is the definition of an RTD?
A: RTDs (resistance temperature device) are temperature sensors that are commonly used in a variety of industrial applications including industrial boilers, petrochemical, exhaust gas monitoring and food processing. RTD sensors have a higher accuracy than thermocouples and thermistors over a wide temperature range, and are more stable over time. Simply put, an RTD is a sensor whose resistance changes with temperature in a consistent repeatable manner.
Q: How does an RTD work?
A: An RTD can provide highly accurate and consistent temperature measurements because the change in resistance of certain materials is so predictable. Most RTD sensors have a response time between 0.5 to 5 seconds and commonly feature a platinum-based element, but can also be constructed with nickel or copper. RTDs made with platinum (also known as PRTs – platinum resistance thermometer) are used most often today due to their higher temperature capabilities, better stability and repeatability.
Probe type RTDs generally consist of a rigid probe with direct mounted connector or extension cable. Assembly type models usually incorporate a rigid probe assembled with a connection head (junction box). Direct immersion probes have the RTD protective sheath (the probe) welded to process fitting similar to temperature gauges – this offers better response but mechanical protection is limited. Access to a process under operation is also limited. Assemblies for Thermowells have the RTD probe typically spring loaded in the connection fitting – this ensures good thermal contact and removes dead space in well tip.
Q: Why and when would you use an RTD connection head?
A: An RTD connection head provides a clean, protected area for mounting a terminal block or transmitter, and can be rated for indoor or outdoor use providing protection against dust, rain, splashing and water from washdown hoses. RTD connection heads are available in cast aluminum, white polypropylene, and cast 316 Stainless Steel. White polypropylene is popular for sanitary and chemical applications, while Stainless Steel is often used in food, pharmaceutical, biotech and chemical applications. Aluminum and Stainless Steel are preferred for industrial applications. Intrinsically safe explosion-proof enclosures are also available for hazardous environments.
Q: What is the best way to protect an instrument’s stem against high velocity flow?
A: A thermowell would offer additional protection and be the preferred method if the application allows for one to be installed.
Q: Why are thermowells used?
A: A thermowell is used with a temperature-sensing instrument to provide a protective barrier between the instrument and the process media. Thermowells can provide protection from harmful process influences including flow, high pressure and harsh environments, reducing the possibility of damage to the temperature instrument and providing protection to the operator. Thermowells also allow easier service to the instrument and reduce operating costs by allowing the temperature instrument to be removed and replaced without shutting down and draining the process.
Q: What types of thermowells are available?
A: The most commonly used types of thermowells are threaded, socket weld, weld-in and flanged connections.
Q: What is lagging extension on a thermowell?
A: A lagging extension, often referred to as the thermowell’s “T” length, is located on the cold side of the process connection and is usually an extension of the hex length of the Thermowell. Usually the lagging extension enables the probe and thermowell to extend through insulation or walls.
Q: How do you calculate the stem length of a thermowell?
A: The bore depth “S” of a thermowell can be used as a reference for the maximum stem length. The “S” must equal or exceed the length of the sensitive portion of the instrument’s stem.
Q: What is a gas regulator?
A:A gas regulator is a device used to control the pressure of gases or liquids. It reduces the pressure of high-pressure media to a lower, desired output pressure and maintains this pressure at a stable level. It works by using internal components such as springs, diaphragms, or pistons to sense changes in output pressure and automatically adjust the valve opening to maintain a set pressure level.
Q: How do I choose the right pressure reducer for my application?
A:Choosing a suitable pressure reducer for your application requires consideration of several key factors:
Q: How to address leakage issues at the connection points and inside the regulator?
A: Connection point leaks are typically caused by loose connecting nuts or aged/damaged sealing washers; these should be addressed by retightening the nuts or replacing the washers. For internal leaks, which may result from worn or damaged components like adjusting screws, springs, pressure-reducing valves, or seals, professional repair or replacement of the faulty parts is necessary.
Q: What should be done if the pressure gauge reads inaccurately or is damaged?
A: An inaccurate reading can be due to damaged internal components, a stuck pointer, or aging of the gauge, necessitating its replacement. If the gauge is damaged from impacts, vibrations, or corrosion, it must be promptly replaced to ensure safety and accuracy.，高
Q: How to handle malfunctioning adjustments or unstable output pressure in a regulator?
A: Malfunctioning adjustments could be due to internal component damage or improper settings, requiring inspection and repair or replacement by professionals. Unstable output pressure might stem from worn internal parts or fluctuating gas flow, so one should check the internal components, adjust the spring position, and stabilize the gas flow.
Q: What measures should be taken when encountering heating element failures, blockages or freezing, grease contamination, or vibration and impact problems?
A: For heating regulators with failed heating elements, inspect the circuit and connections to ensure proper operation. In cases of blockage or freezing, clean out any obstructions and use hot water or steam for thawing (avoid direct flame heating), ensuring the interior remains dry. If contaminated by grease, thoroughly clean the regulator before use to prevent internal part damage or fire hazards. To mitigate the effects of vibrations and impacts, secure the installation base firmly and protect against external disturbances.
Q: How to ensure the safe operation of a regulator?
A: Regularly inspect the regulator for tight connections, accurate pressure gauge readings, and flexible adjustment mechanisms. Follow operating instructions and safety guidelines strictly, train operators to have the necessary skills, and seek professional assistance when encountering complex faults.
Q: What is a welding and cutting torch?
A:A welding and cutting torch is a tool used for welding or cutting metal materials. It operates by mixing oxygen with combustible gases such as acetylene, propane, etc., to produce a high-temperature flame for the operation. It utilizes the heat generated from gas combustion reactions to melt metals for welding or preheat metals before cutting them using a jet of high-speed oxygen.
Q: How do I choose the right welding and cutting torch?
A:selecting the appropriate welding or cutting torch involves a comprehensive evaluation of several key factors to ensure optimal performance, safety, and cost-effectiveness. First, clearly define your application requirements, including the specific material types (such as steel, aluminum, or other alloys), material thickness, and expected workload. Next, assess the characteristics of the working environment, such as whether it’s for outdoor use, any special climatic conditions, or spatial limitations.
For material and thickness considerations, different torch types are suitable for various applications; for instance, thicker metal plates may require higher-power equipment to ensure adequate penetration and cut quality. For thin sheets, choose tools that offer fine control to prevent overheating and deformation of the workpiece.
The skill level of the operator is also a critical factor. If experienced technicians will be using the equipment, you can consider more complex but feature-rich automated systems. Conversely, for novice users or occasional use, simpler and user-friendly manual models are more appropriate.
Budget considerations are equally important. While high-performance products often entail a higher initial investment, they might prove more cost-effective in the long run due to greater efficiency and lower maintenance costs. Additionally, considering long-term operating costs and service support is a prudent approach.
Finally, it’s essential to consult with professional engineers and thoroughly review the technical specifications, user reviews, and after-sales service guarantees provided by manufacturers. By taking all these aspects into account comprehensively, you can make the most suitable choice for your needs, ensuring the best work results and safety.
Through this thorough evaluation, you can select the welding or cutting torch that best meets your requirements, optimizing both performance and safety.
Q: What safety precautions should be taken when using a welding and cutting torch?
A:Safety is crucial when using a welding and cutting torch. Key precautions include:
Q: Does a welding and cutting torch require regular maintenance?
A:Yes, to ensure the safety and reliability of the welding and cutting torch, it should be regularly inspected and maintained. This includes cleaning nozzles, replacing worn parts, lubricating moving parts, etc.
Q:How can I extend the lifespan of a welding and cutting torch?
A:Extending the lifespan of welding and cutting torches not only saves costs but also ensures operational safety and efficiency. To achieve this goal, the following points are crucial:
Follow Manufacturer’s Operating Guidelines: Adhere strictly to the operation manual provided by the manufacturer, including startup, operation, and shutdown procedures. Correct operating methods can prevent unnecessary wear and potential safety risks.
Regular Maintenance and Inspection: Establish a regular maintenance schedule to inspect all components of the torch, such as nozzles, gas hoses, regulators, etc. Clean carbon deposits and other impurities from nozzles promptly to ensure unobstructed gas flow and prevent damage caused by blockages.
Replace Worn or Damaged Parts: Regularly check and replace any parts that show signs of wear or have been damaged, such as seals, electrodes, and nozzles. Address minor issues before they escalate into major problems.
Proper Storage of Equipment: When not in use, store welding and cutting torches in a dry, cool place away from heat sources and high temperatures. Ensure all valves are closed, and store gas cylinders separately from the torch to prevent accidental leaks or collisions.
Avoid Overuse: Minimize using the torch beyond its designed capacity, such as working with excessively thick materials or in unsuitable environments. Overuse can accelerate the aging process of the equipment.
Train Operators: Ensure all operators receive adequate training on how to properly use and maintain the equipment. Skilled operators can help reduce damage caused by incorrect operations.
Use High-Quality Consumables and Accessories: Choose high-quality gases, welding wires, and other consumables, as well as replacement parts from reliable suppliers. Inferior materials can lead to decreased performance and equipment failure.
Maintain Good Ventilation Conditions: Keep the work area well-ventilated, which not only protects the health of the operators but also helps prevent the torch from overheating, thereby extending its lifespan.
By implementing these measures, you can effectively extend the life of your welding and cutting torches, enhance work efficiency, and ensure operational safety.
Q:What are the gas pressures and nozzle sizes used for cutting steel plates of general thickness?
A:Gas Pressure and Nozzle Size for Cutting Steel Plates of General ThicknessWhen cutting steel plates of general thickness, the gas pressure and nozzle size used will vary depending on the specific thickness of the steel plate. Below are some general guidelines:
For steel plates between 40mm and 50mm in thickness, it is recommended to use a torch model G01-100 with nozzle numbers 3-5. The oxygen pressure should be set at 0.5-0.69Mpa, while acetylene pressure should be around 0.01-0.12Mpa. The distance between the flame core tip and the workpiece should be maintained at 3-5mm, with a cutting speed of approximately 25-30mm/s.
For different thicknesses of steel plates, appropriate nozzle models are as follows:
For materials up to 50mm thick, typically choose nozzles numbered 1-4.
For materials between 50mm and 100mm thick, it is advisable to select nozzles numbered 4-5.
For materials thicker than 100mm, choose nozzles numbered 6-7.
Specific parameters such as cutting oxygen pressure, cutting speed, preheating flame energy rate, angle between the nozzle and the workpiece, and the distance between the nozzle and the surface of the workpiece all need adjustment according to the thickness of the steel plate. For example:
Oxygen Pressure: Thicker materials require higher oxygen pressure. However, the oxygen pressure should not be too high or too low, as this can affect the cutting quality. For thinner sheets, oxygen pressure can be appropriately reduced.
Cutting Speed: The thicker the workpiece, the slower the cutting speed should be; conversely, for thinner pieces, the cutting speed can be faster.
Preheating Flame Energy Rate: Adjust the preheating flame based on the thickness of the material to ensure sufficient heat reaches the metal to reach its burning temperature without melting the top edge of the cut.
Angle Between Nozzle and Workpiece: The angle of the nozzle varies with the thickness of the material to optimize heat distribution during the cutting process.
Distance Between Nozzle and Surface of Workpiece: Typically kept within a range of 3-5mm to provide optimal heating conditions and minimize carbon infiltration.
Additionally, it is important to note that the purity of the cutting oxygen should be as high as possible, generally required to be above 99.5%. Lower oxygen purity can lead to decreased cutting efficiency and poorer cut surface quality.
Since these specific parameter values may differ slightly depending on different manufacturers and equipment types, it is best to consult the technical manual of the specific cutting equipment you are using or contact the manufacturer for the most accurate data before actual operation.