Pressure vessel features

Shape of a pressure vessel

Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, and cones are usually employed. A common design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished (torispherical). More complicated shapes have historically been much harder to analyze for safe operation and are usually far more difficult to construct.

Theoretically, a spherical pressure vessel has approximately twice the strength of a cylindrical pressure vessel with the same wall thickness. However, a spherical shape is difficult to manufacture, and therefore more expensive, so most pressure vessels are cylindrical with 2:1 semi-elliptical heads or end caps on each end. Smaller pressure vessels are assembled from a pipe and two covers. For cylindrical vessels with a diameter up to 600 mm, it is possible to use seamless pipe for the shell, thus avoiding many inspection and testing issues. A disadvantage of these vessels is that greater breadths are more expensive, so that for example the most economic shape of a 1,000 litres (35 cu ft), 250bars (3,600 psi) pressure vessel might be a breadth of 91.44 centimetres (36 in) and a width of 1.7018 metres (67 in) including the 2:1 semi-elliptical domed end caps.

• 

  Spherical gas container.
 
• 

  Cylindrical pressure vessel.
 
• 

  Picture of the bottom of an aerosol spray can.

Construction materials

Composite overwrapped pressure vessel with titanium liner.

Many pressure vessels are made of steel. To manufacture a cylindrical or spherical pressure vessel, rolled and possibly forged parts would have to be welded together. Some mechanical properties of steel, achieved by rolling or forging, could be adversely affected by welding, unless special precautions are taken. In addition to adequate mechanical strength, current standards dictate the use of steel with a high impact resistance, especially for vessels used in low temperatures. In applications where carbon steel would suffer corrosion, special corrosion resistant material should also be used.

Some pressure vessels are made of composite materials, such as filament wound composite using carbon fibre held in place with a polymer. Due to the very high tensile strength of carbon fibre these vessels can be very light, but are much more difficult to manufacture. The composite material may be wound around a metal liner, forming a composite overwrapped pressure vessel.

Other very common materials include polymers such as PET in carbonated beverage containers and copper in plumbing.

Pressure vessels may be lined with various metals, ceramics, or polymers to prevent leaking and protect the structure of the vessel from the contained medium. This liner may also carry a significant portion of the pressure load.

Pressure Vessels may also be constructed from concrete (PCV) or other materials which are weak in tension. Cabling, wrapped around the vessel or within the wall or the vessel itself, provides the necessary tension to resist the internal pressure. A "leakproof steel thin membrane" lines the internal wall of the vessel. Such vessels can be assembled from modular pieces and so have "no inherent size limitations".There is also a high order of redundancy thanks to the large number of individual cables resisting the internal pressure.

Safety features

Leak before burst

Leak before burst describes a pressure vessel designed such that a crack in the vessel will grow through the wall, allowing the contained fluid to escape and reducing the pressure, prior to growing so large as to cause fracture at the operating pressure.

Many pressure vessel standards, including the ASME Boiler and Pressure Vessel Code and the AIAA metallic pressure vessel standard, either require pressure vessel designs to be leak before burst, or require pressure vessels to meet more stringent requirements for fatigue and fracture if they are not shown to be leak before burst.

Safety valves

Example of a valve used for gas cylinders.

As the pressure vessel is designed to a pressure, there is typically a safety valve or relief valve to ensure that this pressure is not exceeded in operation.

Pressure vessel Design

Scaling

No matter what shape it takes, the minimum mass of a pressure vessel scales with the pressure and volume it contains and is inversely proportional to the strength to weight ratio of the construction material (minimum mass decreases as strength increases).

Scaling of stress in walls of vessel

Pressure vessels are held together against the gas pressure due to tensile forces within the walls of the container. The normal (tensile) stress in the walls of the container is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls. Therefore pressure vessels are designed to have a thickness proportional to the radius of tank and the pressure of the tank and inversely proportional to the maximum allowed normal stress of the particular material used in the walls of the container.

Because (for a given pressure) the thickness of the walls scales with the radius of the tank, the mass of a tank (which scales as the length times radius times thickness of the wall for a cylindrical tank) scales with the volume of the gas held (which scales as length times radius squared). The exact formula varies with the tank shape but depends on the density, ρ, and maximum allowable stress σ of the material in addition to the pressure P and volume V of the vessel. (See below for the exact equations for the stress in the walls.)

Spherical vessel

For a sphere, the minimum mass of a pressure vessel is

,

where:

•  is mass,
•  is the pressure difference from ambient (the gauge pressure),
•  is volume,
•  is the density of the pressure vessel material,
•  is the maximum working stress that material can tolerate.

Other shapes besides a sphere have constants larger than 3/2 (infinite cylinders take 2), although some tanks, such as non-spherical wound composite tanks can approach this.

Cylindrical vessel with hemispherical ends

This is sometimes called a "bullet" for its shape, although in geometric terms it is a capsule.

For a cylinder with hemispherical ends,

,

where

• R is the radius
• W is the middle cylinder width only, and the overall width is W + 2R

Cylindrical vessel with semi-elliptical ends

In a vessel with an aspect ratio of middle cylinder width to radius of 2:1,

.

Gas storage]

In looking at the first equation, the factor PV, in SI units, is in units of (pressurization) energy. For a stored gas, PV is proportional to the mass of gas at a given temperature, thus

. (see gas law)

The other factors are constant for a given vessel shape and material. So we can see that there is no theoretical "efficiency of scale", in terms of the ratio of pressure vessel mass to pressurization energy, or of pressure vessel mass to stored gas mass. For storing gases, "tankage efficiency" is independent of pressure, at least for the same temperature.

So, for example, a typical design for a minimum mass tank to hold helium (as a pressurant gas) on a rocket would use a spherical chamber for a minimum shape constant, carbon fiber for best possible , and very cold helium for best possible .

Stress in thin-walled pressure vessels

Stress in a shallow-walled pressure vessel in the shape of a sphere is

,

where  is hoop stress, or stress in the circumferential direction,  is stress in the longitudinal direction, p is internal gauge pressure, r is the inner radius of the sphere, and t is thickness of the cylinder wall. A vessel can be considered "shallow-walled" if the diameter is at least 10 times (sometimes cited as 20 times) greater than the wall depth.

Stress in the cylinder body of a pressure vessel.

Stress in a shallow-walled pressure vessel in the shape of a cylinder is

,

,

where:

•  is hoop stress, or stress in the circumferential direction
•  is stress in the longitudinal direction
• p is internal gauge pressure
• r is the inner radius of the cylinder
• t is thickness of the cylinder wall.

Almost all pressure vessel design standards contain variations of these two formulas with additional empirical terms to account for wall thickness tolerances, quality control of welds and in-service corrosion allowances.

For example, the ASME Boiler and Pressure Vessel Code (BPVC) (UG-27) formulas are:

Spherical shells:

Cylindrical shells:

where E is the joint efficient, and all others variables as stated above.

The factor of safety is often included in these formulas as well, in the case of the ASME BPVC this term is included in the material stress value when solving for pressure or thickness.

Winding angle of carbon fibre vessels

Wound infinite cylindrical shapes optimally take a winding angle of 54.7 degrees, as this gives the necessary twice the strength in the circumferential direction to the longitudinal.

Carbon Water filters are almost as Popular as Air Coolers

Carbon water filters are very effective in removing contaminants from your water supply.
A water filter will remove toxins and contaminants from the water supply, so if you are interested in clean water for drinking, cooking and washing, it is a good idea to install one. One of the most popular types of water filters is the carbon water filter. If you have decided to install such a system, you may be interested in understanding exactly how it works.

Carbon has long been used to eliminate impurities and so it is only logical that activated carbon would be used in water filtering systems. They are one of the most effective ways to filter water, so it is no surprise that carbon filter systems are the most popular among home owners. They are almost as popular as air cooler.

The carbon water filter has a contaminate removal rate that is much higher than other systems have. There are two key elements that will improve the efficacy of the carbon system: how much carbon is in the unit, and how long the contaminants in the water are in contact with the carbon.

The scientific principals by which carbon filters remove contaminants from water are called catalytic reduction and absorption. What occurs is that negatively charged ions of the contaminant are attracted to the positively charged activated carbon, and the carbon absorbs organic compounds. In addition, certain materials present in the water, such as choloramines or chlorine are removed during the catalytic reduction process.



You can be assured that you and your family will be drinking the cleanest water possible if you install a carbon water filter system. When we consider how much we rely on our water supply, it seems like a small investment to keep it as clean and pure as possible.

You may be one of the lucky ones who does not really need a water filtering system. The only way to find out whether or not you do is to have it analyzed. Just take a sample to a lab that does that kind of testing. The results are available quickly, within a day or two, and then you can make the decision as to whether you want to install a system.

Carbon filtration systems are a good choice for your home to remove certain contaminants, but you have to realize that they cannot remove every element that may be found in the water supply, such as radio nuclides, thallium, sulfate, selenium, nickel, mercury, copper, chromium, barium, asbestos, arsenic, antimony and mineral salts, most of which are found in trace amounts in some water.

Heat Exchanger Tube Bundles Inspection

Heat exchangers are used by many industries, especially in oil refineries and chemical plants. Their purpose is to exchange heat from one place to another, usually from one liquid to another liquid. The continued efficiency of this device demands regular heat exchanger inspection to determine whether or not the integrity of the equipment.

Where are Heat Exchangers Found?

Most homes also have a heat exchanger of some kind. The most common household heat exchanger can be found in a refrigerator. In hot countries air conditioners are common; another kind of heat exchanger. Cars contain them too - the radiator removes the excess heat from the radiator fluid by making use of the natural airflow caused by the car's forward progress.

A similar principle applies in large industry where heat needs to be transferred from one place to another. The most common type of heat exchanger found in oil refineries and other large plants is the "shell and tube heat exchanger".

This design employs a large shell, usually a very large diameter tube that can withstand high pressures. It contains a bundle of tubes inside. The heat exchanged is from two different fluids. One fluid flows through the shell of the exchanger while the other flows through the tube bundle. The two fluids do not make direct contact with each other, but the difference in their respective heat values is changed through the indirect contact that is made.

A shell and tube heat exchanger is a complex design. The internal tubes are often of differing types and design in order to achieve different results. Some tubes may be plain while others may be finned horizontally or longitudinally. The tubes may also be composed of different materials and different thermal conductivity. They may be made from stainless steel, carbon steel, brass, copper or cupronickel, for example.

Because of their complex nature it is necessary to have a regular the equipment regularly inspected. This can determine the wall thickness of the tubes, which are subject to pitting and corrosion as well as erosion over time. The condition of the entire tube bundle can be charted and evaluated through a highly detailed inspection using a device called an Internal Rotary Inspection System.

The Internal Rotary Inspection System works through ultrasonic testing and it is non-destructive in nature. The Internal Rotary Inspection System probe has to be inserted into a tube which is then filled with water.

The Internal Rotary Inspection System probe has a small mirror that rotates and focuses an ultrasonic beam onto the wall of the tube. The mirror rotation is driven by a small turbine, which in turn is driven by water pressure as it is pumped into the tube. The Internal Rotary Inspection System probe is slowly pulled out of the tube at a rate of about one inch or 25 millimetres per second, recording the condition of the internal wall of the tube as it progresses.

The results gained from a heat exchanger inspection using an Internal Rotary Inspection System probe is generally extremely accurate. Its accuracy can be as good as to within .005 inches, or .13 millimetres. Of course, in order to gain this level of accuracy it is necessary for the tubes to be thoroughly cleaned down to bare metal prior to the inspection.

Get Organized and Install a Water Filter Along with an Air Cooler

Choosing the right water filtering system from a good company is important.

There are many companies to choose from if you have decided to install a water filter in your home. There are many good, reputable companies offering these products, so you have a wide array of great products from great companies to choose from. A little research on your part will get you the best deal around.

One of the best, and also one where you will always find the most competitive prices is the Home Water Purifiers and Filters Company. This company with the obvious sounding name carries a full selection of all of the popular systems for water filtration. They carry one of the most popular and effective, the point of use osmosis system. This multi stage system is the newest in sophisticated technology designed to produce clean, healthy water.

Many homeowners choose the full house system, as compared to the point of use ones, since the water is treated as it enters the home, and the flow rate is consequently much higher. It is like comparing a window air cooler to an whole air conditioning system. If the water supply to your home has a lot of sediment in it, this is really the ideal system for you.

The mechanics of these systems is made up of a filter cartridge enclosed within a housing. The cover of the housing has a spanner wrench opening for easy access to the filter. It is recommended that a plumber install these systems, although a knowledgeable homeowner can probably do it.

Every one of the water filter systems offered by Home Water Purifiers and Filters Company are NSF certified and are designed for easy installation and maintenance, high water flow and long lasting filters. This means that you will get a lot of value from the unit since it is inexpensive to install and keep in good working order.

It is important to choose the right size system for filtering your water. If you over sue the system, you will have to change the filter more frequently. If you don' change the filter when it needs to be changed, you will have a system that is not doing anything at all. Make sure you get a system with a feature that will advise you automatically when the filter requires changing.

Pressure Vessel Testing

Pressure vessels store liquids and gases under pressure for use in industrial and domestic settings. In domestic settings, examples include hot water storage tanks, compressed air cylinders as used in diving, and oxygen cylinders. Industrial applications are more interesting in terms of inspection, and include natural gas storage, chemical storage and various applications in the process, petrochemical and oil industries.

Operation of these vessels carries an inherent danger, and design, manufacture and operation is often backed by strict regulations and law. For this reason, often the exact definition of a pressure vessel varies from country to country, with a typical definition including any vessel with a maximum operating pressure of above 15 psi.

Pressure vessels are typically constructed of steel, though any material with a good tensile strength, and chemical stability for the chosen application could be used. Standards and design codes such as those proposed by ASME provide a list of suitable materials and guidelines for use at various temperatures, and these are generally used.

Welding on pressure vessels is also an issue, as the design of cylindrical or spherical pressure vessels using forged or rolled parts, generally requires welding, and this can introduce weakness. The heat of welding can weaken the material, and introduce cracking and other defects into the vessel. To detect these defects we use non-destructive testing techniques.

Inspection of pressure vessels ensures they're operating safely, and helps avoids accidents, downtime and loss of profits. For these reasons alone, regular inspection is a good idea. And generally inspection is carried out at regular intervals in order to pre-empt problems and build up a reliable pattern of data. In the event something should go wrong, these records can show that maximum action was taken prevent problems, and protect staff.

NDT or Non Destructive Testing is used for inspection, due to its non-invasive nature. Technologies such as ultrasonic testing and electromagnetic testing are the main technologies used, however dye penetrant and magnetic particle can also be used for a more thorough inspection.

The American Petroleum Institute also provides standards for the non-destructive inspection of pressure vessels, and requires an API qualified technician with the right certification to perform the inspection. This can be more thorough, though provides more coverage, and is an option depending on the thoroughness the client requires.

Techniques such as LFET (Low Frequency Electromagnetic Technique) are used for the inspection of the wall plates, and techniques such as BFET (Balanced Field Electromagnetic Technique)are used for the inspection of welds.

Fresh Air Technologies Commercial Wet Steam Condenser Coil Restoration

Fresh Air Technologies Commercial Wet Steam Condenser Coil Restoration

Ideas for Water Filtering Can be Used for Air Coolers

There are many types of water filters to choose from, depending upon the kind of water you have, what criteria you have, and how much you want to spend.

The best way to choose a filter system for your home's water supply is to make sure you get as much information as possible. There are many differences of opinion, so you have to research in order to find the best one for you. The type of unfiltered water you currently have, what you consider the most important characteristics in your water supply, and how much money you are willing to pay.

A simple, inexpensive system may satisfy your needs if you don't want to spend too much, and you will be content with just eliminating heavy particles from your water. If you find it necessary to to eliminate even the smallest particles, you will have to use a system that employs reverse osmosis, to remove particles as small as.01 microns. For home drinking water, it is preferable to eliminate all of the bacteria in the water, as well as any sediment that can be found in the water.

Since each home has a different water supply, different aged pipes and different preferences, so there is no one size for all solution to which type of water filter you should choose. Well water usually has a better taste than water supplied from a municipality, but often it has microbes or particles that may make it look unappetizing and maybe even smell badly. The homeowner can do a water test to find out the composition of his home water supply and then determine how much he wants to filter it.

A lot of homeowners believe that any filtering of the water before drinking it will improve the quality and make it healthier. Others insist on filtering their drinking water to the finest possible degree. It is important to know the quality of the water; even the best water filter system will not render extremely contaminated water drinkable.

There are different forms of water filter systems, just as there are different types of air coolers, from ones that you just connect to each faucet to others that installed at the entrance of the water supply into the home, so that all of the water is filtered. There are electrical systems that will eliminate all of the contaminants, and others that Will only eliminate down to particles of.4 microns. These will really only remove sediment from the water. If your water is high in iron, the water will have an unpleasant odor of sulfur and only the very efficient water systems will remove all of the smell.

If you want to get the most life out of your water filtering system, you should consider using a water conditioner, which will protect the cartridges for the filter, in addition to supplying your home with water that is more pleasant for bathing and cooking. the type of filter you use will be totally dependent upon the type of water you have to filter, and you will have to have a water analysis in order to determine that.

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Things to Know About Metal Fabricated Pressure Vessels and Their Technical Integrity

Industrial sectors that buzz with several operations running at the same time require an end number of technical equipment and devices to support the manufacturing processes and systems of different mechanisms. There are multiple applications that need to transmit and contain certain high volume liquids and gases with safety and efficiency, and metal fabricated pressure vessels are the perfect solutions for these applications. Let's know more about these indispensably important industrial devices.

What are Pressure Vessels?

These are strategically and precisely constructed metal-clad closed containers that are critically designed to transmit or contain industrial gases or fluids (which may or may not be toxic), at a pressure that is substantially different than the ambient pressure outside the vessel.

Most of these are fabricated with metal in order to make them completely capable of carrying, containing, transferring or disposing harmful liquids, toxins, solid, semi-solid or gaseous substances. These are widely used in production or manufacturing units

Engineers who are involved to design or fabricate these metal-clad vessels make sure that they perform the assigned application with utmost security, protection and safety. Many a times, these metal fabricated pressure vessels are used under cryogenic atmosphere in order to provide maximum efficiency without any risk factors.

What Is the Technological Integrity Used to Fabricate?

When it comes to fabricating metal-clad pressure vessels, it is most crucial to pay the highest level of attention to technical supremacy and engineering knowhow, as even the slightest of lapse in this regard can lead to fatal accidents and damage of related equipment. Hence, all the technical and engineering elements that are involved in designing and manufacturing a full-proof metal fabricated pressure vessel are thoroughly looked at by manufacturing companies of repute.

Keeping the importance of these technical aspects in mind, government has empowered certain authoritative bodies to provide official certificates to that would conform that a particular pressure vessel is manufactured according to the set standards of security and safety guidelines.

As a matter of fact, metal fabricated pressure vessels that are constructed to hold liquids and gases within its chamber under highly divergent pressures are expected to possess high levels of tensile and mechanical strength and durability. It is meant to withstand adverse conditions and to avoid any chances of explosion or leakage.

Ideally these are constructed out of stainless steel for its favorable properties like versatility, malleability, durability and resistance to corrosion. Stainless steel also supports varied fabrication techniques to be carried out for achieving the perfect and precise design parameters.

The three major types of engineering technologies that are used for metal fabrication are work hardening, welding and machining.

What are the Basic Industrial Applications of Metal Fabricated Pressure Vessels?

Metal fabricated pressure vessels are used for multiple industrial, domestic and commercial applications of high significance. The machine plays an important role in several operational and functional activities. some of them are listed below:

• Pressure reactors
• Recompression chambers
• Industrial compressed air receivers
• Oil refinery and mining operations
• Autoclaves
• Petrochemical plants
• Hydraulic reservoirs
• Pneumatic reservoirs
• Rail vehicle airbrake reservoirs
• Distillation towers
• Nuclear reactor vessels
• Storage vessels for liquefied gases like ammonia, chlorine and the cabin pressurization loads.
• Submarine and spaceship habitats
• Domestic hot water storage tanks
• Diving cylinders

Apart from keeping all these significant aspects in mind, the most crucial factor is the selection of the right pressure vessel apt to meet a specific application provided by a reliable and expert manufacturer.

The Best Water Filters and Air Coolers

There are not only many types of water filters, there are many purposes for them. Most of the water filters ta ht people are familiar with are for filtering impurities out of the water they drink. But you can also filter the water in your shower and even the water that goes to your washing machine. If you have a lot of minerals, sediment and other particulates in your water, you may want to filter the water you wash your clothes in to make sure that they will come out clean and white.

Most of these filters work to capture the sediment in the water before it goes into the tub of the washing machine where your clothes are going to go. This is done at a screen on a valve at the inlet to the washer. This allows the water to flow through, while taking out sediment.

Since a washer uses a lot of water at a time for each wash, make sure you get the proper sized filter. Otherwise you will have to be changing hate filter constantly to make it work properly.

There are many brands of washing machine water filters, just as there are many brands of air coolers and they are manufactured both by water filter companies and washing machine companies.

Even among this wide range of manufacturers, there is a wide range of types of filters for your washer. There are quick change filters, garden filters, ceramic filters and many speciality filters. You have to be careful to pick the right filter for your washer; not all brands of washers will supp port all brands of washing machine filters. Just to be sure, work with a company that will give you a warranty on their filter so that you can return it if anything goes wrong.

One of the most important elements in how well a filter of any kind will work is keeping the filter clean. This is a very small but necessary bit of maintenance that you have to keep up in order for the filter to work at its optimum.

Shut off the power to the washer to avoid any electrical shock, then find the water inlet valve. Visually check the filter for debris that may have collected on it. If there is a great deal of debris, you need to change the filter.

You will be very surprised at how nice your clothes will come out if you use a washing machine filter to keep the water that washes your clothes clean in the first place.

From Steel Sheets to Space Shuttles an Inside Look at Pressure Vessels

Pressure vessels are described as a closed container that is fabricated to hold gases or liquids. The key feature of pressure vessels is that they are designed to hold its content at a pressure which is different from the ambient pressure. In theory they can be almost any shape. In most cases they are constructed using sections of spheres, cylinders and cones. More complex designs have been used but have come at a much higher cost and are more difficult to analyze when it comes to safety. One of the most common designs also incorporates end caps which are often called heads.

When it comes to strength spherical pressure vessels have at least twice the strength of a cylindrical pressure vessel with the same exact wall thickness. However, the downfall for using a spherical shaped design is that it is more expensive and more difficult to manufacture. With this being said most pressure vessels are cylindrical shaped using the end cap design. When it comes to smaller vessels they are usually assembled from a pipe, along with two covers.

Next we take a closer look at a pressurized water vessel. They deal with extremely high pressures so during construction safety is at a premium. They use a core container which is difficult to build but provides the most security in case of an accidental explosion. The cylinder walls are constructed from single sheets of high-strength steel that are rolled together and welded. The steel that is used can be up to 25 cm thick. The inside of these pressure vessels are also lined with stainless steel to resist corrosion. To build a pressure vessel it takes a specialized skill and specific equipment. Highly skilled welders must weld the material so it is as strong as the steel plates. This welding is vital so that the vessel remains structurally sound.

Regardless of what shape your vessel takes, the minimum mass of a vessel scales with the pressure and the overall volume. This is inversely proportional to the strength to weight ratio of the material used for construction. Simply said, minimum mass decreases as the strength increases. They are held together against the pressure from the forces inside the walls of the container. Normal stress within the walls of the container is always proportional to the radius of the vessel and inversely proportional to the overall diameter of the walls. After all of this you might be asking yourself, how and why is all of this important and how is it used? Pressure vessels are used in many different applications. Some examples include diving cylinders, distillation towers, oil refineries and even space shuttles.

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