Butterfly Valve

Butterfly Valve Advantages and Disadvantages

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Butterfly Valve Advantages and Disadvantages

A Butterfly Valve is a shut-off valve with a relatively simple construction. In a closed position, the disc blocks the valve bore while in an open position, the disc turn allows flow. A quarter turn takes the valve from fully open to a fully closed position or the opposite, and thus the butterfly valve allows for quick opening and closure.

Butterfly valves can be used for a broad range of applications within water supply, wastewater treatment, fire protection, and gas supply, in the chemical and oil industries, in fuel handling systems, power generation etc. Some of the advantages for this type of valve are the simple construction not taking up too much space, and the lightweight and lower cost compared to other valve designs.

The valves can be operated by handles, gears or actuators according to any specific need.

Types of Butterfly Valves

Butterfly valves have been around for a long time, and are used for a variety of applications. They made their first appearance during the 1930s, and have been utilized by several industries ever since.

Often made out of cast iron, butterfly valve’s name is based on the functionality of its disc. There are a few different types of butterfly valves, however, they fall into two basic types – Lug and Wafer valves.

LUG BUTTERFLY VALVE

The lug version of the butterfly valve’s design is similar to a 3-piece ball valve in that one end of the line can be taken off without having an effect on the opposing side. This can be executed by using threaded inserts, flanges, along with two sets of lugs (bolts) that don’t utilize nuts since each flange features its own bolts. It’s also important to note that you don’t need to shut down the entire system in order to clean, inspect, repair, or replace a lug butterfly valve (you would need to with a wafer butter valve).

WAFER BUTTERFLY VALVE

A wafer butterfly valve’s function is to retain a seal to protect against dual-directional pressure differential in the flow of fluid. In other words, the wafer version of butterfly valves was designed to hold a tight seal, safeguarding against bi-directional pressure differential in order to avoid any backflow in systems that have been manufactured for uni-directional flow.

This is accomplished by using a tightly fitted seal, such as an O-ring, gasket, precision machined, along with a flat valve face on the downstream and upstream sections of the valve.

Both lug and wafer butterfly valves are used in a number of applications for industrial sectors that include food processing, pharmaceutical, chemical, oil, water as well as wastewater management.

Butterfly valves, for the most part, have replaced ball valves in a lot of industries. This is especially the case for those dealing with petroleum because they are less expensive and easy to install. It’s important to note that pipelines that contain butterfly valves can’t be ‘pigged’ for cleaning. “Pigging” is the process of making use of devices referred to as “pigs” to carry out a variety of maintenance operations.

BUTTERFLY VALVE APPLICATIONS

  • Cooling water, air, gases, fire protection.
    • Slurry and similar services.
    • Vacuum service.
    • High-pressure and high-temperature water and steam services.
    • Compressed air or gas applications.

Advantages of a Butterfly Valve

  • The compact design requires considerably less space, compared to gate, globe, or other valves.
  • Light in weight.
  • Quick acting; as a quarter-turn valve, it requires less time to open or close.
  • Butterfly Valve is available in large sizes, ranging from NPS 1¹⁄₂ (DN 40) to over NPS 200 (DN 5000).
  • They have low-pressure drop and high-pressure recovery.
  • Provide bubble-tight service.

Disadvantages of a Butterfly Valve

  • Butterfly Valve Throttling service limited to low differential pressure.
  • Cavitation and choked flow are two potential concerns.
  • Butterfly Valve disc movement guides and affects by flow turbulence

 

Needle Valve

Needle Valve

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Needle Valve

A Needle Valve is used to make relatively fine adjustments in the amount of fluid flow. The distinguishing characteristic of a needle valve is the long, tapered, needle-like point on the end of the valve stem. This “needle” acts as a disk.

The longer part of the needle is smaller than the orifice in the valve seat and passes through the orifice before the needle seats. This arrangement permits a very gradual increase or decrease in the size of the opening. Needle valves are often used as component parts of other, more complicated valves. For example, they are used in some types of reducing valves.

Needle Valve Application

Most constant pressure pump governors have needle valves to minimize the effects of fluctuations in pump discharge pressure. Needle valves are used in almost every industry in an incredibly wide range of applications – anywhere control or metering of steam, air, gas, oil, water or other non-viscous liquids is required.

Needle Valve application in industries

  • Zoological sciences
  • Gas and liquid dispensation
  • Instrumentation control
  • Cooling
  • Power generation
  • Automatic combustion control systems
  • precise flow regulation

Needle valves can also be used as on/off valves or for throttling service.

ADVANTAGES OF NEEDLE VALVES

Needle valves give us great control over the flow rate of a liquid or gas which in reality, gives us the luxury to consume the fuel according to our desire. For example, in a motorcar engine, it is a needle valve which is responsible to regulate the fuel flow rate.

These valves can work both ways. Whether you want to increase the flow rate or decreasing it.

Besides the control on flow rate, it also stables the pressure too. The pressure loss is on the minimum side as compared to the other same as valves that are available in the market.

DISADVANTAGES OF NEEDLE VALVES

Unlike other types, you can’t visually observe the position of the screw or the handle used to control the positioning of the screw in the valve that determines if the valve is open or closed. To tackle it, other devices are often included in the equipment design that makes it possible to monitor the flow and use the valve to adjust that flow accordingly.

Needle valve selection

Items that you should consider when selecting a needle valve:

Pressure

The working pressure is an important factor in selecting the right needle valve. Robust needle valves can handle pressures of up to 4000-5000 psi (275-413 bar) at 100°F (38°C). When still higher pressures are required, high-performance valves are available that can handle up to 10000 psi (689 bar) pressure at 100°F (38°C).

Size

Needle valves are available in a wide range of sizes and end connections. Male/female connections with inch/metric threads can be used. The most commonly available valves have the size from 2 to 12 mm or 1/8” to 2”. Using the right valve size facilitates efficient flow and system operation with fewer chances of wear and leakage.

Temperature

Needle valves can be operated at high or low temperatures. For extreme temperatures, the packing/sealing used is particularly relevant. Two most commonly used packing materials are PTFE (Teflon) for a temperature range of -65°F to 450°F (-54° C to 232°C) and PEEK (Polyether Ether Ketone) for increased temperature resistance up to 600°F (315 °C).

Materials

Different materials are used in needle valve construction. The commonly used materials include brass, 304 or 316 stainless steel, carbon steel and Alloy 400 (Nickel based alloy).

Stainless steel is widely used for its corrosion resistance, chemical stability, and high-temperature resistance. Brass needle valves are used in hydraulic systems, high-temperature applications, and gas piping. Alloy 400 is used for its high strength, corrosion resistance and used mainly in marine and chemical processing applications.

 

 

Positive Displacement Compressor

Positive Displacement Compressor

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Positive Displacement Compressor

An air compressor is a device which sucks the atmospheric air and pressurizes it and to a higher pressure and gives it to the system. Compressors can be classified as

  1. Positive displacement
  2. Dynamic displacement

difference between positive displacement compressors and dynamic compressors

A positive displacement compressor, compress the air by forcing air into a compression chamber and by decreasing its volume

A dynamic displacement compressor compresses the air by imparting the kinetic energy of the rotating parts to the air. Centrifugal and axial compressors are dynamic compressors.

The basic one-line difference between positive displacement compressor (PDC) and dynamic compressor (DC) lies in the fact of how they apply the pressure on a fluid. In PDC a mechanical linkage reduces the volume of fluid physically to increase the pressure whereas in DC the fluid is provided some velocity which undergoes a diffuser resulting in the increase in pressure.

An easy way to memorize the fact is in the name itself. Positive displacement compressor means a system which compresses the air by the displacement of a mechanical linkage reducing the volume (since the reduction in volume due to a piston in thermodynamics is considered as a positive displacement of the piston). The dynamic compressor brings out a change in the velocity of the fluid eventually resulting as the rise in pressure.

Types of positive displacement compressor

Piston Compressors

The piston compressor is the oldest and most common type of industrial compressor. It’s available in single-acting or double-acting, oil-lubricated or oil-free variants, with various numbers of cylinders in different configurations.

Oil-free piston compressors have piston rings made of polytetrafluoroethylene (PTFE) or carbon. Alternatively, the piston and cylinder wall can be profiled as on labyrinth compressors. Larger machines are equipped with a crosshead and seals on the gudgeon pins, and a ventilated intermediate piece to prevent oil from being transferred from the crankcase into the compression chamber. Smaller compressors often have a crankcase with bearings that are permanently sealed.

Rotary Screw Compressors 

Developed in the 1930s, rotating displacement compressors in twin screw form have two main parts — the male and female rotors, which rotate in opposite directions while the volume between them and the housing decreases. Each screw element has a fixed, built-in pressure ratio that is dependent on its length, the pitch of the screw and the form of the discharge port. To attain maximum efficiency, the built-in pressure ratio must be adapted to the required working pressure.

Modern oil-free screw compressors have asymmetric screw profiles that reduce internal leakage and improve energy efficiency. Their external gears are most often used to synchronize the position of the counter-rotating rotors. Because the rotors never come in contact with one another, no lubrication is required in the compression chamber and the compressed air produced is completely oil-free.

Liquid-injected screw compressors use liquid lubrication in their compression chamber and often with their compressor bearings as well. The liquid cools and lubricates the compressor element’s moving parts, which cools the air being compressed and reduces the return leakage to the inlet. Today, oil is the most commonly used liquid due to its good lubricating and sealing properties. Other liquids used include water.

Tooth Compressors

Tooth compressors contain two rotors that rotate in opposite directions inside a compression chamber. Its compression process consists of intake, compression and outlet phases. During the intake phase, air is drawn into the compression chamber until the rotors block the inlet.

The air is then compressed in the compression chamber, which gets smaller as the rotors rotate during the compression phase. In its final phase, the outlet port is blocked during compression by one of the rotors while the inlet is open to draw in new air into the opposite section of the compression chamber.

Scroll Compressors 

A scroll compressor is usually a type of oil-free orbiting displacement compressor, which compresses a specific amount of air into a continuously decreasing volume. The compressor element consists of a stator spiral fixed in a housing and motor-driven eccentric, orbiting spiral.

The spirals are mounted with 180° phase displacement to form air pockets with a gradually varying volume, which provides the scroll elements with radial stability. When the orbiting spiral moves, air is drawn in and captured in one of the air pockets, where it is gradually compressed as it moves toward the center.

 

 

Vane Compressors 

Most vane compressors are oil-lubricated and operate using the same principle as many compressed air expansion motors. A rotor with radial, movable blade-shaped vanes is eccentrically mounted in a stator housing.

When it rotates, the vanes are pressed against the stator walls by centrifugal force. Air is drawn in while the distance between the rotor and stator increases. The air is captured in the different compressor pockets, and decreases in volume with rotation and is later discharged when the vanes pass the outlet port.

 

 

 

 

Roots Blowers

A Roots blower is a valve-less displacement compressor without internal compression. When the compression chamber comes in contact with the outlet port, compressed air flows back into the housing from the pressure side.

Subsequently, further compression takes place when the volume of the compression chamber further decreases with continued rotation. Accordingly, compression takes place against full counter-pressure, which results in low efficiency and a high noise level. Roots blowers are frequently used as vacuum pumps and for pneumatic conveyance in low pressure applications.

Types and application of Check Valves

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Types and application of Check Valves

Check Valves , also known as non-return or one-way valves, are designed to allow fluid to flow one way in a pipeline. They’re constructed of a clapper which hangs from a hinge, the clapper shaft or pin, which is mounted to the underside of the bonnet, inside the valve body. The basic design of a check valve inhibits backflow in a line.

Check valve applications

  • Protect drinking water from contamination by backflow resulting from gravity, back siphonage or backpressure (e.g. Hose connected kitchen spray or shower hand spray).
  • Protect sensitive equipment against possible damage or contamination resulting from a reversal of flow direction (e.g. water meter, pump or filter).
  • Hold water in a system or pipe after the flow has been turned off to prevent drainage or facilitate restart (e.g. pumping systems).
  • Prevent crossover flow in systems with unequal line pressures (e.g. cold and hot water inlets in thermostatic mixers).
  • Reduce the risk of backflow or leakage in case of valve failure (e.g. solenoid valve at the inlet of an appliance).
  • Allow complex systems to function properly by ensuring unidirectional flow (e.g. multi-zone heating system or booster pumps).

Types of the Check Valve

Swing Check Valve

A hinged disc assembly is suspended from the body to allow it to move freely. This configuration minimizes pressure loss and eases the fluid flow. Swing check valves can be used for either horizontal or vertical (fluid flowing upward) pipe layouts.

 

 

 

 

 

 

Lift Check Valve

The structure of the lift check valve is the globe valve without the handwheel and any parts which related to manual operation. And have the cover in lieu of the bonnet. Because of its large fluid resistance, this valve is used primarily for small-bore applications.

 

 

 

Wafer Check Valve

Thanks to its wafer shaped design, this swing check valve is far thinner and lighter than conventional water hammer absorbing check valves. It features a built-in bypass circuit and superior closing action and is multifunctional high performance water hammer absorbing check valve.

 

 

 

 

Advantages and Disadvantages of Check valve

ADVANTAGES

The check valve’s operation is completely self-automated. Therefore, should a facility lose power, the valve would still function, preventing damage to pumps and other equipment, as well as other problems upstream.

DISADVANTAGES

Noise (slamming), water hammer, and reverse flow are common problems with check valves. It is very important to note, however, that these problems generally occur because of improper sizing and/or selection for the application.

These types of valves commonly (and mistakenly) selected/sized as an on/off valve would be. Doing so could cause premature wear, high-pressure drop, and increased the expenditure of pump energy as it works harder to satisfy the system.

If you’re experiencing issues with a check valve, or need to select a new one for your process, talk to an engineer experienced in the selection/sizing of these types of valves. Doing so will help your system perform at its highest efficiency while requiring a lot less maintenance.

 

 

 

Globe Valve

Globe Valve

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Globe Valve

A globe valve regulates flow in a pipeline. It is used to control or stop the flow of liquid or gas through a pipe. Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle.

Working principle

When the valve is actuated to open the disk will perpendicularly move away from the seat. When compared to a gate valve, a globe valve generally yields much less seat leakage. This is because the disk-to-seat ring contact is more at right angles, which permits the force of closing to tightly seat the disk.

Globe valves can be arranged so that the disk closes against or in the same direction of fluid flow. When the disk closes against the direction of flow, the kinetic energy of the fluid impedes closing but aids opening of the valve.

When the disk closes in the same direction of flow, the kinetic energy of the fluid aids closing but impedes opening. This characteristic is preferable to other designs when quick-acting stop valves are necessary.

Advantages and disadvantages and applications of Globe valves

ADVANTAGES

  • Good shutoff capability
  • Moderate to good throttling capability
  • Shorter stroke (compared to a gate valve)
  • Available in tee, wye, and angle patterns, each offering unique capabilities
  • Easy to machine or resurface the seats
  • With disc not attached to the stem, a valve can be used as a stop-check valve

DISADVANTAGES

  • Higher pressure drop (compared to a gate valve)
  • Requires greater force or a larger actuator to seat the valve (with pressure under the seat)
  • Throttling flow under the seat and shutoff flow over the seat

applications of Globe valves

  • Cooling water systems where flow needs to be regulated
  • Fuel oil system where the flow is regulated and leak-tightness is of importance
  • High-point vents and low-point drains when leak-tightness and safety are major considerations
  • Feedwater, chemical feed, condenser air extraction, and extraction drain systems
  • Boiler vents and drains, main steam vents and drains, and heater drains
  • Turbine seals and drains
  • Turbine lube oil system and others

Positioner

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Positioner

A Positioner is used on an actuator (hydraulic or pneumatic) to provide feedback to the controller in response to the required and actual movement of the valve stem. This ensures the valve responds to system requirements.

Valve positioners compare a control signal to a valve actuator’s position and move the actuator accordingly. They are used with both linear valves and rotary valves. Valve positioners are used when the 0.2 to 1 bar pressure in the diaphragm chamber is not able to cope with friction and high differential pressures.

Valve positioners are usually mounted on the yolk or top casing of a pneumatic actuator for linear control valves, or near the end of the shaft for rotary control valves. For either configuration, the positioner is connected mechanically to the valve stem or valve shaft. This allows for the valve’s position to be compared with the position requested by the controller. When a control signal differs from the valve actuator’s position, the valve positioner sends the necessary feedback to move the actuator until the correct position is reached.

There are different types of control valve positioners

  • pneumatic positioner
  • Electro-pneumatic valve positioner
  • Electronic positioner

 

  • Pneumatic positioners. These devices receives a pneumatic (air) signal from the controller and output a pneumatic signal to the actuator.
  • Analog, or electro-pneumatic, positioners. Here, the input signal is electrical, rather than pneumatic.
  • Digital, or smart, positioners. These positioners also receive an electrical signal, but it’s digital as opposed to analog.
  • Digital positioners came on the scene about 20 years ago, but they only really started gaining popularity recently as automation has started to take off in plants and along pipelines.
  • The main reason digital positioners are popular is that they can do much more than just control the position of the valve. The newest positioners on the market can also collect data about the valve to automatically alert users about how the valve and its assembly are performing, and even aid in diagnostics and maintenance.
  • Since they have fewer mechanical moving parts, digital positioners last longer than their traditional pneumatic and analog counterparts. Plus, they don’t bleed any air while the valve is at rest, which reduces energy consumption.

Applications

Oil and Gas
• All process applications
• Petro-chemical: Production, Transportation, Refining
• ESD applications
Chemical
• All chemical process applications
• Fugitive Emission Monitoring
Pulp & Paper
• Treatment and production process
Food and Beverage
• Utilities and process control
Power
• Coal fired power plants, renewables power generation, nuclear power plants
Other
• Metal, Mining & Minerals (MMM)
• Water and Wastewater
• Biopharmaceutical

 

 

Rotameter

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Rotameter

Rotameter is simple industrial flow meter that measure the flow rate of liquid or gas in a closed tube.

Rotameters are popular because they have linear scales, a relatively large measurement range, low pressure drop, and are simple to install and maintain.

Rotameters are a subset of meters called variable area flow meters that measure the flow rate by allowing the fluid to travel through a tapered tube where the cross sectional area of the tube gradually becomes greater as the fluid travels through the tube.

The flow rate inside the rotameter is measured using a float that is lifted by the fluid flow based on the buoyancy and velocity of the fluid opposing gravity pulling the float down.  For gasses the float responds to the velocity alone, buoyancy is negligible.

The float moves up and down inside the rotameter’s tapered tube proportionally to the flow rate of the fluid.  It reaches a constant position once the fluid and gravitational forces have equalized.

Changes in the flow rate cause rotameter’s float to change position inside the tube.  Since the float position is based on gravity it is important that all rotameters be mounted vertically and oriented with the widest end of the taper at the top.

It is also important to remember that if there is no flow the float will sink to the bottom of the rotameter due to its own weight.

The operator reads the flow from a graduated scale on the side of the rotameter, which has been calibrated to a specific fluid with a known specific gravity.

Rotameters can be calibrated for other fluids by understanding the basic operating principles.  Rotameter accuracy is determined by the accuracy of the pressure, temperature, and flow control during the initial calibration.

Any change in the density and weight of the float will have impacts on the rotameter’s flow reading.  Additionally any changes that would affect the fluid such as pressure or temperature will also have an affect on the rotameter’s accuracy.  Given this, rotameters should be calibrated yearly to correct for any changes in the system that may have occurred.

There are several advantages to a rotameter over a more complicated flow meter including:

Rotameter Selection

  • What are the minimum and maximum flow rate for the flow meter?
  • What are the minimum and maximum process temperature?
  • What is the size of the pipe?
  • Would you like a direct reading rotameter or is a look-up table acceptable?
  • What accuracy do you need?
  • Do you require a valve to regulate the flow?
  • Will there be back pressure?
  • What is the maximum process pressure?

 

advantages

  • Simple to install and maintain
  • The cost of the rotameter is low.
  • It provides a linear scale.
  • It has good accuracy for low and medium flow rates.
  • The pressure loss is nearly constant and small.
  • Usability for corrosive fluid.
  • Rotameters can be installed in areas with no power since they only require the properties of the fluid and gravity to measure flow, so you do not have to be concerned with ensuring that the instrument is explosion proof when installed in areas with flammable fluids or gases.
  • Rotameters are simple devices that are mass manufactured out of inexpensive materials keeping investment costs low.
  • Pressure loss due to the rotameter is minimal and relatively constant because the area through the tapered tube increases with flow rate.  This results in reduced pumping costs.
  • The rotameter’s scale is linear because the measure of flow rate is based on area variation.  This means that the flow rate can be read with the same degree of accuracy throughout the full range.

disadvantages

  • When opaque fluid is used, the float may not be visible.
  • It has not well in pulsating services.
  • Glass tube types subjected to breakage.
  • It must be installed in the vertical position only.

Rotameter application

  • The rotameter is used in process industries.
  • It is used for monitoring gas and water flow in plants or labs.
  • It is used for monitoring filtration loading.
  • No external power required – suitable for hazardous areas and remote areas where it would be expensive to supply power.

Refrences:

 

Air Compressor

Air Compressor

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Air Compressor

An Air Compressor is a device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air).

By one of several methods, an air compressor forces more and more air into a storage tank, increasing the pressure. When tank pressure reaches its upper limit the air compressor shuts off.

The compressed air, then, is held in the tank until called into use. The energy contained in the compressed air can be used for a variety of applications, utilizing the kinetic energy of the air as it is released and the tank depressurizes.

When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank.

There are numerous methods of air compression, divided into either positive-displacement or negative-displacement types.

When air is compressed, it is under pressure greater than that of the normal atmospheric pressure and it characteristically attempts to return to its normal state.

Since energy is required to compress the air, energy is released as the air expands and returns to atmospheric pressure. Air compressors were designed to compress air to higher pressures and harness this potential energy source.

Unlike other sources of power, no conversion from another form of energy such as heat is involved at the point of application. Compressed air or pneumatic devices are therefore characterized by a high power-to-weight or power-to-volume ratio.

Application of Compressor

Air compressors are found in a wide range of environments for an even wider range of uses. You’ll see gas stations offering compressed air to inflate your vehicle’s tires and your tire shop using compressed air with an air tool to remove your tires.

You may have seen small desktop air compressors used with an airbrush or a trailer-style gas-powered air compressor at a construction site powering jackhammers and concrete compactors.

In fact, you’ve likely been around many different kinds of air compressors and didn’t even know it — they may be hidden away in your refrigerator or the HVAC system at your local arena.

  • Blowing up balloons or inflatable products
  • Adding air to tires on bikes and on vehicles
  • Cleaning crevices and tight spaces on equipment or other durable items with directed air pressure
  • Painting with an airbrush for small precision projects or on larger surfaces like bikes and the body of vehicles and recreational vehicles
  • Using various pneumatic tools for home projects
  • Painting vehicles in an auto body shop
  • Sanding in an auto body shop or in woodworking
  • Making snow at ski hills or for entertainment uses
  • Using pneumatic nail guns for roofing
  • Providing dental and medical services
  • Using pneumatic drills and hammers on construction sites
  • Powering various air tools in an automotive repair shop
  • Using an air blowgun to clean machinery
  • Sandblasting in a machine shop and manufacturing facilities
  • Moving feed and grain to and from silos with conveyors
  • Glasshouse ventilation systems
  • Spraying crops
  • Powering dairy machines
  • Operating pneumatic material handling equipment
  • …..

Compressor Types

Dynamic

  1. Axial
  2. Centrifugal

Positive Displacement

1.Rotary

  • Screw
  • Blower

2.Reciprocating

  • Single Acting
  • Double Acting

References:

Temperature Transmitter

Temperature Transmitter

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Temperature Transmitter

Temperature Transmitter converts the input signal from a wide range of sensors, such as resistance sensors and thermocouples, but in some cases also from potentiometers, into a standardized output signal (e.g. 0 … 10 V or 4 … 20 mA).

With digital temperature transmitters, the sensor type and the measuring span can be freely configured, along with many further options such as the error signalization or a measuring point identification.

Type Of Temperature Transmitter

There are many different types of Temperature Sensor available and all have different characteristics depending upon their actual application. A temperature sensor consists of two basic physical types:

Contact Temperature Sensor Types

These types of temperature sensor are required to be in physical contact with the object being sensed and use conduction to monitor changes in temperature. They can be used to detect solids, liquids or gases over a wide range of temperatures.

Non-contact Temperature Sensor Types

These types of temperature sensor use convection and radiation to monitor changes in temperature. They can be used to detect liquids and gases that emit radiant energy as heat rises and cold settles to the bottom in convection currents or detect the radiant energy being transmitted from an object in the form of infra-red radiation (the sun).

Temperature Sensor

Negative Temperature Coefficient (NTC) thermistor

A thermistor is a thermally sensitive resistor that exhibits a large, predictable, and precise change in resistance correlated to variations in temperature.

An NTC thermistor provides a very high resistance at low temperatures. As temperature increases, the resistance drops quickly. Because an NTC thermistor experiences such a large change in resistance per °C, small changes in temperature are reflected very fast and with high accuracy (0.05 to 1.5 °C).

Because of its exponential nature, the output of an NTC thermistor requires linearization. The effective operating range is -50 to 250 °C for glass encapsulated thermistors or 150°C for a standard.

Resistance Temperature Detector (RTD)

An RTD, also known as a resistance thermometer, measures temperature by correlating the resistance of the RTD element with temperature. An RTD consists of a film or, for greater accuracy, a wire wrapped around a ceramic or glass core.

The most accurate RTDs are made using platinum but lower-cost RTDs can be made from nickel or copper. However, nickle and copper are not as stable or repeatable. Platinum RTDs offer a fairly linear output that is highly accurate (0.1 to 1 °C) across -200 to 600 °C. While providing the greatest accuracy, RTDs also tend to be the most expensive of temperature sensors.

Thermocouple

This temperature sensor type consists of two wires of different metals connected at two points. The varying voltage between these two points reflects proportional changes in temperature.

Thermocouples are nonlinear, requiring conversion when used for temperature control and compensation, typically accomplished using a lookup table. Accuracy is low, from 0.5 °C to 5 °C.  However, they operate across the widest temperature range, from -200 °C to 1750 °C.

Semiconductor-based sensors

A semiconductor-based temperature sensor is placed on integrated circuits (ICs). These sensors are effectively two identical diodes with temperature-sensitive voltage vs current characteristics that can be used to monitor changes in temperature.

They offer a linear response but have the lowest accuracy of the basic sensor types at 1 °C to 5 °C. They also have the slowest responsiveness (5 s to 60 s) across the narrowest temperature range (-70 °C to 150 °C).

Application Of Temperature Transmitters

  • monitoring temperature of a remote process
  • drive equipment such as meters, data loggers, chart recorders, computers or controllers.

Advantages of temperature sensor

Thermocouple measures temperature in -200oC to +2500oC range, RTD measures in -200oC to +850oC range, thermistor measures in -100oC to +260oC range and IC sensors measures in -45oC to 150oC range.

(Advantages of thermocouple are): No external power required, simple and rugged in construction, cheaper, support for wider temperature range etc.

  • (Advantages of RTD are ): More stable, higher accuracy, more linearity compare to thermocouple
  • (Advantages of thermistor are): Higher output, faster in operation
  • (Advantages of IC sensor are): Highest output, cheaper, most linear than all types

Disadvantages of temperature sensor

  • (Disadvantages of thermocouple are): Non linearity, least stability, Low voltage, Reference is needed, least sensitivity etc.
  • (Disadvantages of RTD are ): Lower absolute resistance, expensive, current source needed, less rugged compare to thermocouples etc.
  • (Disadvantages of thermistor are): Nonlinearity, limited support for temperature range, current source needed, fragile, self heating etc.
  • (Disadvantages of IC sensor are): Power supply needed, slower in operation, self heating, limited configurations, temperature upto 150oC etc.
Flange

Flange

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Flange

The Flange is the second most used joining method after welding. Flanges are used when joints need dismantling. It Provides flexibility for maintenance.

Flange Connects the pipe with various equipment and valves. Breakup flanges are added in the pipeline system if regular maintenance is required during plant operation.

Flange Materials Specification

Dimensions from carbon steel and stainless steel flanges are defined in the ASME B16.5 standard. The material qualities for these flanges are defined in the ASTM standards.

These ASTM standards, define the specific manufacturing process of the material and determine the exact chemical composition of pipes, fittings, and flanges, through percentages of the permitted quantities of carbon, magnesium, nickel, etc., and are indicated by “Grade”.

For example, a carbon steel flange can be identified with Grade F9 or F11, a stainless-steel flange with Grade F316 or Grade F321 etc..
Below you will find as an example a table with chemical requirements for fittings ASTM A403 Grade WP304, WP304L, WP316L and a table with frequent Grades, arranged on pipe and pipe-components, which belong together as a group.

As you may be have noted, in the table below, ASTM A105 has no Grade. Sometimes ASTM A105N is described; “N” stands not for Grade, but for normalized.

Normalizing is a type of heat treatment, applicable to ferrous metals only. The purpose of normalizing is to remove the internal stresses induced by heat treating, casting, forming etc.

Carbon Steel Flanges

The Carbon Steel Flanges are available in various dimensions. Exhibiting the properties such as high strength, high toughness, excellent fatigue strength, superior chemical resistance and high stress-corrosion cracking resistance, these flanges are ideal for connecting various pipes and are significant while support is required for mechanical parts.

  • ASTM A105, ASTM A350 LF1, LF2 CL1/CL2, LF3 CL1/CL2
  • ASTM A694 F42, F46, F48, F50, F52, F56, F60, F65, F70

Stainless Steel Flange

Stainless Steel Flanges are corrosion resistant and have a wide variety of uses. We carry a variety of threaded flanges, weld neck flanges and slip-on flanges and of course, we can custom build stainless steel flanges to your specifications.

  • ASTM A182 F304/304L, F316/316L, F316H, F310, F321, F44 (UNS S31254)
  • ASTM A403 WP316/316L
  • ASTM A403 WP304/304L
  • ASTM A182 F304, F304L, F316, F316L, F321

316 / 316L

316/316L is the most commonly used austenitic stainless steel in the chemical process industry. The addition of molybdenum increases general corrosion resistance, improves chloride pitting resistance and strengthens the alloy in high-temperature service.

Through the controlled addition of nitrogen, it is common for 316/316L to meet the mechanical properties of 316 straight grade while maintaining a low carbon content.

Applications of flanges

Flanges are integral parts of many engineering and plumbing projects.

In many applications, engineers need to find a way to close off a chamber or cylinder in a very secure fashion, usually, because the substance inside must differ from the substance outside in composition or pressure.

They do this by fastening two pieces of metal or other material together with a circle of bolts on a lip. This “lip” is a flange.

Plumbing

You can connect two sections of metal piping by soldering or welding them together, but pipes connected in this way are very susceptible to bursting at high pressures.

A way of connecting two sections of pipe more securely is by having flanged ends that you can connect with bolts. This way, even if gases or liquids build up to high pressures inside the pipe, it will often hold with no problem.

Mechanics

In order to connect two sections of a large, enclosed area, it is often best to used flanges and bolts. An example of this is the connection between the engine and the transmission in an automobile.

In this case, both the engine and the transmission contain a number of moving parts that can easily get damaged if they get dust or other small objects inside of them. By connecting the outer casings of the engine and transmission in this way, engineers protect the inner workings of both.

Electronics

Flanges have a specific purpose in cameras and other electronic devices. Though flanges in such items do not usually have to sustain high pressures, they do have to hold tight so they can keep out harmful particles.

These flanges are usually found connecting two different materials, such as the glass of a lens and the rest of the body of the camera.

TYPES OF FLANGES

The most used flange types in Petro and chemical industry are:

  • Welding Neck Flange
  • Slip On Flange
  • Socket Weld Flange
  • Lap Joint Flange
  • Threaded Flange
  • Blind Flange

SPECIAL FLANGES

Except for the most used standard flanges, there are still a number of special flanges such as:

  • Orifice Flanges
  • Long Welding Neck Flanges
  • Weld flange / Nipoflange
  • Expander Flange
  • Reducing Flange

Weld-neck

Complete with a tapered hub, these flanges are recognizable and used in high-pressure environments. The flange is particularly useful under repeat bending conditions.

Slip-on

A flange which is slipped over the pipe and welded both inside and outside to increase strength and prevent leakage. A favorite for engineers compared to the weld-neck due to their lower cost.

Socket-weld

With a static strength equal to the Slip-on flange, the Socket-weld is connected with the pipe with 1 fillet weld on the outside of the flange. Due to corrosion issues, some processes do not allow this flange.

Lap-joint

Used in conjunction with a lap joint stub end, the flange is slipped over the pipe but not fastened, unlike the slip-on. Instead, the flange is held in place by the pressure transmitted to the gasket by the flange pressure against the back of the pipe lap.

Threaded

Used in special circumstances, the threaded flange can be attached to the pipe without being welded. These are usually positioned on pipes with a deep wall thickness, used to create the internal thread.

Blind

Manufactured without a bore, these flanges are used to blank off the end of piping, valves and pressure vessel openings. They are also most suitable for high pressure-temperature applications.

References:

https://hardhatengineer.com/types-flanges-used-piping/

http://www.wermac.org/flanges/flanges_pipe-connections_pipe-flanges.html

http://www.sunnysteel.com/flange-material.php

https://blog.miragemachines.com/6-of-the-most-common-flange-types-used-in-the-oil-and-gas-industry