Stress Distribution at the Fillet of an Internal Flange

Stress Distribution at the Fillet of an Internal Flange
This paper deals with the determination of the stress distribution at the fillet of a ANSI B16.5 flanges attached internally to a hollow cylinder. A load parallel to the axis of the cylinder and of variable eccentricity acts on a bearing plate which rests on the flange. The strains are measured by means of electrical resistance wire strain gages. The ratios of the mean cylinder diameter to the cylinder wall thickness and of the mean cylinder diameter to the flange thickness are varied. The principal stresses at the fillet are given as functions of these parameters. The experimental results are compared with the stresses calculated on the basis of an approximate theoretical solution for both an axial and an eccentric load.
Abstract Joining of steel pipes and pipe flanges use today the conventional method of fusion welding, where the flange is girth-welded onto the pipe. However, fusion welding of flanges to pipes is associated with many disadvantages such as the final quality of the weld, degradation of the mechanical properties of the base pipe near the heat affected zone, defects and cracks appearing in the weld, misalignments, to mention a few. The current study proposes a novel pipe-flange connection to replace the fusion welding process of steel pipes with a method based on cold working. The method is based on that the steel pipe is inserted into the neck of the flange, in which two circumferential grooves are manufactured. An expansion tool having two teeth is entered from the open side of the connection and is expanded hydraulically such that the teeth deform the pipe and cold work it plastically into the grooves. This will provide a strong joint between the flange and pipe. In this study the performance of the connection is maximized by optimizing the design of the flange and the expansion tool.
The use of bolted flange connections in the offshore wind industry has steeply risen in the last few years. This trend is because of failings observed in other modes of joints such as grouted joints, coupled with enormous economic losses associated with such failures. As many aspects of bolted flange connections for the offshore wind industry are yet to be understood in full, the current study undertakes a comprehensive review of the lessons learned about bolted connections from a range of industries such as nuclear, aerospace, and onshore wind for application in offshore wind industry. Subsequently, the collected information could be used to effectively address and investigate ways to improve bolted flange connections in the offshore wind industry. As monopiles constitute an overwhelming majority of foundation types used in the current offshore wind market, this work focusses on large ANSI welding neck flanges in the primary load path of a wind turbine foundation, such as those typically found at the base of turbine towers, or at monopile to transition piece connections. Finally, a summary of issues associated with flanges as well as bolted connections is provided, and insights are recommended on the direction to be followed to address these concerns.
As per recent reports, the offshore wind sector could bring in £17.5 bn investment to the U.K. economy over the next few years after faster than expected cost-cutting slashed subsidies for the technology by half [1]. On top of that, the baseline scenario for the United Kingdom’s installations by the end of 2030 is to reach the capacity levels of 40 GW, four times the current state [2]. Additionally, the target of £100 per MWh set for the year 2020 regarding the levelised cost of energy (LCOE) of offshore wind was achieved in U.K. projects four years earlier in 2016 [3]. The above figures reinforce the need for new technological developments that will enable the utilisation of larger and more efficient offshore wind turbines (OWTs). In this direction, one of the most important concerns is the support structure of the turbine’s tower, which requires further study concerning not only the feasibility of future installations, but also current problems that need to be better understood and addressed.
OWT structures, which are quite large in thickness and diameter, operate in the hostile marine environment, where variable amplitude loads are constantly applied on different parts of the structure [4,5]. In the offshore industry, grouted connections were initially used to charge the transition piece (TP), with a certain overlap length, on the monopile (MP) foundations. Therefore, there is a tube-in-tube connection, wherein the space between the two tubes is filled with grout (Figure 1) [6]. Towards the end of last decade, numerous grouted connection joints between large diameter monopiles and connecting tubular steel transition pieces at the base of overlying support towers were found to be failing. For the majority of U.K. offshore MPs that experienced grout cracking and failures, the issue was recognised to be primarily owing to the widespread absence of shear keys (or weld beads) on straight MP and TP surfaces. Bending moments as a result of complex wind (which was the main difference in loading conditions compared with oil and gas platforms) and wave loading were important design considerations that were not accounted for during design of grouted connections for OWTs. Furthermore, axial connection capacity was found to be significantly lower than that assumed previously owing to the MP scale effect, lack of manufacturing and installation tolerances, and abrasive wear due to the sliding of contact surfaces when subjected to large moments. Typical failure modes included dis-bonding, cracking, wear, and compressive grout crushing failure.
The number of bolts depends on the ANSI plate flanges radius and thickness, type of tool used, size of the bolts, and predicted loads on the structure. These bolts serve the purpose of exerting a clamping force to keep the joint together [20]. The behaviour and life of the bolted joint depend on the magnitude and stability of that clamping force. The preload is created by the tightening process during the assembly of bolt and nut in the joint to provide enough clamping force on the joint. Therefore, the bolts need to be preloaded at the assembly stage in the flange connection. An intuitive analogy would be to think of the bolts and the joint members as elastic parts. In that way, they can be modelled as spring elements, where the bolts are stretched in their elastic region when tightened, in order to compress the joint. The joint has a much stiffer elastic constant compared with the bolts, depending on material and dimensions.
It is possible to consider the bolt as an energy storage device, which accumulates the necessary potential energy to clamp the joint and is subjected to several environmental and operative conditions that may affect its behaviour [20]. The objective is for the preload on the bolt to be maintained at a certain level, but, owing to a large number of influencing factors, it is almost impossible to achieve or retain the desired state. It must be noted though, that the main concern is not the value of preload on the bolt, but maintaining the sufficient level of clamping force that holds the joint together. Moreover, if the clamping force is too low, the joint could loosen and be subjected to more severe consequences owing to cyclic loads. On the other hand, if the bolt is over-tight, it could exceed its proof load and may break under external load. In fact, during the tightening process, a torque is applied to turn the nut and the bolt stretches. This operation creates preload in the bolted joint. This sequence of events, at any point, controls the preload. It is possible to control the preload through torque or turn or stretch or through a combination of all of them. In all of the control strategies, the torque is used to tighten the fastener even if other mechanisms are used to control the tightening. There are a lot of uncertainties in the relationship between the control parameters like torque and the preload, which could be minimised by measuring and controlling the build-up of bolt tension. This is the motivation for creating the family of tools called bolt tensioners. Using the bolt tensioner is nowadays a common practice during the installation of offshore wind turbines.
The employment of ANSI blind flanges connections for OWTs has considerably increased in the past decade owing to the failures and subsequent economic losses associated with grouted connections. In this study, the issues and opportunities associated with bolted flange connections have been thoroughly reviewed and discussed for application in the offshore wind industry. The key conclusions drawn from this study are as follows:
The advantages of bolted flange connections include the provision of direct load path through the primary steel alone, thereby avoiding slippage, reducing steel requirements compared with grouted connections, the absence of curing time, and easiness to inspect and monitor the MP–TP connection.
The challenges associated with bolted flange connections include material selection issues, short-term relaxation of bolts, issues associated with load distribution in threads, and static failure of bolted flange.
The main cause of short-term relaxation is the embedment that occurs mostly owing to surface irregularities as well as time-dependent creep deformation.
The consequence of temperature differential can either increase or decrease the clamping force depending on the thermal expansion and contraction coefficient of the materials employed in bolted connections.
The setups associated with bolted joint such as washers, lubricants, coatings, and gaskets play a pivotal role in creating and maintaining integrity in bolted joints.
The failure modes observed in bolted joints include self-loosening, fatigue failure, corrosion, and galling.
An expected trend in the bolted flange connection is the increased usage of tensioning tools compared with torqueing applications.
Further studies in the offshore wind industry can enable the optimal use of ANSI threaded flanges connections in design, manufacturing, installation, operation, maintenance, and decommissioning phases.
Ring flange connections for tubular towers, like those for wind turbines or chimneys, are subjected to significant fatigue loading. Next to the bolts, the weld connecting the flange to the tower shell also needs to be checked against fatigue failure. The flange causes local bending moments in the shell, which increase the meridional stress, i. e. stress concentrations occur. In this paper, the influence of geometrical imperfections on such stress concentrations is quantified and the influence of flange geometry on resulting stress is investigated. Recommendations are given for flange dimensions and the design procedure.

Manufacturing and development of a bolted GFRP flange joint for oil and gas applicati

Manufacturing and development of a bolted GFRP flange joint for oil and gas applications
The manufacturing industry saw a significant rebound, and oil prices started to recover as well. Both of these trends are expected to continue in 2017.

At Allied Valve, we also saw some big changes this year. We expanded our product line to include Masoneilan control valves, CDC rupture discs, and Groth relief valves and flame arresters. We also beefed up our service capabilities with a new Mobile Lab trailer and new control valve testing systems.

Finally, we continued our initiative to bring you valuable content related to valves, actuators, and the many industries we serve. Here are our top 5 industrial valve articles of 2016.

Maximizing Your Control Valve Performance: A Guide to Control Valve Selection, Maintenance, and Repair
Process plants can contain thousands of control valves, responsible for keeping process variables like flow, level, pressure, and temperature within the desired operating range. Despite their importance to product quality, efficiency, and a company’s bottom line, control valves are often neglected. This article provides an in-depth look at the factors that affect control valve performance and how to keep your valves always working their best.
It came to our attention earlier this year that some safety valves containing Thermodiscs (e.g., Consolidated 1811 and Consolidated 1711 series) were being put through hydrostatic testing. These valve parts are designed for steam service only and water can cause damage, potentially beyond repair. This article describes the problems that hydrostatic testing can cause and what you can do to mitigate these problems.
The American National Standards Institute (ANSI) and the International Society of Automation (ISA) provide standards for the hydrostatic testing of control valves. The goal of the test is to verify the valves’ structural integrity and leak tightness. This article summarizes the fluid, pressure, and time requirements of hydrostatic testing as well as the standards for acceptable performance.
To work properly when they’re needed, all valves must be maintained. It used to be that preventative maintenance was the only option. But with the diagnostic tools available today, it’s possible in some cases to use a data-based predictive approach instead. Both of these approaches are part of an effective valve discmaintenance program. This article helps you understand when each of them is most appropriate.
Sand casting can be used for the majority of metals. Even highly reactive magnesium is sand cast provided care is taken and the correct materials used by adding what are called inhibitors into the sand.

Sand castings inevitably have a slow cooling rate because of the large insulating mass of sand surrounding the liquid metal as it cools. Grain sizes and dendrite arm spacings tend to be larger than in equivalent section sizes in die-castings.
Sand casting involves the pouring of molten metal into a cavity-shaped sand mould where it solidifies (Fig. 6.8). The mould is made of sand particles held together with an inorganic binding agent. After the metal has cooled to room temperature, the sand mould is broken open to remove the casting. The main advantage of sand casting is the low cost of the mould, which is a large expense with permanent mould casting methods. The process is suitable for low-volume production of castings with intricate shapes, although it does not permit close tolerances and the mechanical properties of the casting are relatively low owing to the coarse grain structure as a result of slow cooling rate.
The goal of this experimental study is to manufacture a bolted GFRP forged flange connection for composite pipes with high strength and performance. A mould was designed and manufactured, which ensures the quality of the composite materials and controls its surface grade. Based on the ASME Boiler and Pressure Vessel Code, Section X, this GFRP flange was fabricated using biaxial glass fibre braid and polyester resin in a vacuum infusion process. In addition, many experiments were carried out using another mould made of glass to solve process-related issues. Moreover, an investigation was conducted to compare the drilling of the GFRP flange using two types of tools; an Erbauer diamond tile drill bit and a Brad & Spur K10 drill. Six GFRP flanges were manufactured to reach the final product with acceptable quality and performance. The flange was adhesively bonded to a composite pipe after chamfering the end of the pipe. Another type of commercially-available composite flange was used to close the other end of the pipe. Finally, blind flanges were used to close both ends, making the pressure vessel that will be tested under the range of the bolt load and internal pressure.
In manufacturing of the steel bridge, fillet welded T-joint is widely used and angular distortion is often generated. So, reduction or control of angular distortion without additional processes to welding is strongly demanded because it takes great time and effort to correct the angular distortion. In this study, the effectiveness of welding with trailing reverse-side flame line heating for preventing angular distortion was investigated through the welding experiment and numerical simulation in submerged arc welding of fillet T-joint with three different thick flange plate. First, the heat source models for numerical analysis of both submerged arc welding and flame line heating were constructed based on the comparison with the measured temperature histories and angular distortion. And then, these heat source models were used in combination with various kinds of distance between two heat sources to make clear the appropriate distance condition for smallest angular distortion was 150 mm, and it does not depend on thickness of flange plate. It was also confirmed that the experimental angular distortions were in good agreement with those calculated. With a focus on the influence of thickness of flange plate, the reduction of angular distortion by welding with trailing reverse-side flame line heating becomes smaller with increasing thickness of flange plate. However, angular distortion could be adequately prevented under the appropriate flame line heating condition in either thickness of flange plate because the welding-induced angular distortion also becomes smaller with increasing thickness of flange plate. Thus, it was concluded that welding with trailing reverse-side flame line heating could be useful for preventing angular distortion of fillet T-joint, which is a component of steel bridge, enough not to correct it after welding.
Garlock offers a range of Butterfly Valves for different applications. Ranging from GAR-SEAL Butterfly Valves are used extensively where corrosive, abrasive and toxic media, to STERILE-SEAL valves are used in applications where sterile processes need to be maintained in the pharmaceutical and food industries.
Depending on your application, different air valve material and design type should be used. For a better understanding on which type of Garlock Butterfly Valve will best fit the application, you can refer to our Chart
The mechanism of opening of the aortic valve was investigated in dogs by attaching radiopaque markers to the commissures and the leaflets. Analysis of abnormal cardiac cycles demonstrated that, when the ventricular pressure first equalled the aortic pressure, the intercommissural distances increased 9 percent, and the valve opened with a stellate orifice without forward flow and without a rise in aortic pressure. Further opening of the aortic valve was dependent on forward flow over a narrow range. A new mechanism of aortic valve opening is proposed. This mechanism results in minimal flexion stresses on the leaflets and is important for the longevity of the normal aortic valve. It can occur only if the leaflets arise from an expansile aortic root.
Original LESER spare parts are the guarantee that also after maintenance works your safety valve precisely fulfills its task to protect people and environment. Learn with the spare pare finder which subassemblies are installed in your individual safety valve to be able to order the correct LESER spare part. The spare part finder shows the bill of materials of your individually configured valve body.
The list shown contains all components, regardless whether they are needed as spare parts. As initial spare parts supply for API, High Efficiency, High Performance, Compact Performance and Modulate Action safety relief valves, we recommend the Spare Part Kits. For the other product groups please contact us for an inital spare part offer. Find out more about LESER-Spare Parts Kits.
Please enter a combination of a serial number (SerNr.) and an article number (ArtNr.) to bring up the right spare parts (e.g. SerNr: 10202021, ArtNr: 4411.4443). You can find the serial and article numbers on the name plate of the valve or on the Certificate for Gobal Application, which you can download in the CERTIFICATES-area.
Please pay attention to the following user instruction:
The spare part finder currently only shows bills of materials for valves assembled in our Hohenwestedt plant. For spare parts lists of other valves, please contact your local partner.
Some items in the bill of materials are subassemblies which contain one or several of the following items. In most cases the subassembly should be ordered as a spare part.

What is a Steel Flange?

THE BASICS OF STEEL FLANGES
Stainless steel flanges provide an easy access for cleaning, inspection or modification. They usually come in round shapes but they can also come in square and rectangular forms. The flanges are joined to each other by bolting and joined to the piping system by welding or threading and are designed to the specific pressure ratings; 150lb, 300lb, 400lb, 600lb, 900lb, 1500lb and 2500lb.
A flange can be a plate for covering or closing the end of a pipe. This is called a blind flange. Thus, flanges are considered to be internal components which are used to support mechanical parts.
 
MATERIALS
Each flange material is to be considered for its application prior to ordering, this is due to the structural integrity of the application that the flange will be used on.
Currently, the most common materials for flanges are:
Carbon steel
  • ASTM A105/A266 Gr.2 (high temperature carbon steel flanges)
  • ASTM A350 LF1 to LF3 (low temperature carbon steel flanges)
  • ASTM A694 Gr. F42/F52/F56/F60/F65 (high yield carbon steel flanges to match API 5L linepipes)

Alloy Steel
  • ASTM A182 Gr. F1/F2/F5/F9/F11 Cl.2/F12 Cl.2/F22 Cl.3/F91 (alloy steel flanges)

Stainless / Duplex Steel
  • ASTM A182 F304/304L, 316/316L, 321, 347, 348 (stainless steel flanges), 904/904L
  • ASTM A182 F51 (duplex flanges)/F53-F55 (superduplex flanges)

Nickel Alloys / Superalloys
  • ASTM B166 UNS NO6600 (Inconel 600)
  • ASTM B564 UNS N06625 (Inconel 625)
  • ASTM B425 UNS-NO8800 (Incoloy 800)
  • ASTM B564 UNS N08825 (Incoloy 825)
  • ASTM B160 UNS N0200 (Nickel 200)
  • ASTM B564 UNS N04400 (Monel 400)
  • ASTM B564 UNS N10276 (Hastelloy C-276)

Titanium
  • ASTM B381 Gr.2 (Titanium)

In industry, flanges, including stainless steel flate flanges, stainless steel slip on flanges, and stainless steel weld neck flanges, form a vital connecting link for piping, valves and other equipment. They provide an easy point of access for cleaning, inspection, modification, and for necessary repairs. A flanged joint provides a strong seal in a closed system, and is made by bolting together a gasket flanked by two flanges.
In heavy industry, these flanges need to be especially resilient or they can prove to be the weak point in a system. It is important therefore, to ensure that the flanges you are choosing are up to the task.
Why are stainless steel flanges preferred for industrial use?
In all metal applications, corrosion is a constant consideration. Rust, chemicals and other environmental factors all take their toll on metals. Therefore, the choice of flange would need to be resistant to these factors. Stainless steel outperforms other metal flanges – including carbon steel – due to its high resistance to corrosion.
Stainless steel is incredibly strong and durable, capable of withstanding immense pressures. By comparison, aluminium may be a cheaper option but it is softer and not as reliable under heavy stress.
Any system or piece of equipment is only as strong as its weakest part. Joins and welds are traditionally a weak point, so it would be wise to make sure that your choice of metal is correct for the application.
Depending its use, a flange may need to withstand high very temperatures. The correct grade of stainless steel flange would ensure that there is no warping or deformation which would compromise the system.
Cheaper, lower grade metal flanges may be fine for certain applications, but if you want your system or equipment to work at maximum capacity, then you should consider spending a little more on stainless steel flanges.

WHAT ARE PIPE FLANGES AND HOW DO THEY WORK?
Offering a reliable way to connect pipe systems with the various equipment, valves, and other components of virtually any processing system, flanges are the second most used joining method after welding.
Using flanges adds flexibility when maintaining piping systems by allowing for easier disassembly and improved access to system components.
A typical flanged connection is comprised of three parts:

  • Pipe Flanges
  • Gasket
  • Bolting

In most cases, there are specific gasket and bolting materials made from the same, or approved materials as the piping components you wish to connect. Stainless Steel flanges are some of the most common, and mostly stainless steel threaded flanges. However, flanges are available in a wide range of materials so matching them with your needs is essential.
Other common flange materials include Monel, Inconel, Chrome Moly, and many others depending on the application.
The best option for your needs will depend on both the system in which you intend to use the flange and your specific requirements.
COMMON FLANGE TYPES AND CHARACTERISTICS
Flanges are not a one-type-fits-all sort of solution. Sizing aside, matching the ideal flange design to your piping system and intended usage will help to ensure reliable operation, a long service life, and optimal pricing.

MAKING THE CONNECTION: FLANGE FACING TYPES
Flange design is only the start when considering the ideal flange for your piping system. Face types are another characteristic that will have a major impact on the final performance and service life of your flanges.
Facing types determine both the gaskets needed to install the flange and characteristics related to the seal created.
Common face types include:

  • Flat Face (FF): As the name suggests, flat face flanges feature a flat, even surface combined with a full face gasket that contacts most of the flange surface.
  • Raised Face (RF): These flanges feature a small raised section around the bore with an inside bore circle gasket.
  • Ring Joint Face (RTJ): Used in high-pressure and high-temperature processes, this face type features a groove in which a metal gasket sits to maintain the seal.
  • Tongue and Groove (T&G): These stainless steel blind flanges feature matching grooves and raised sections. This aids in installation as the design helps the flanges to self-align and provides a reservoir for gasket adhesive.
  • Male & Female (M&F): Similar to tongue and groove flanges, these flanges use a matching pair of grooves and raised sections to secure the gasket. However, unlike tongue and groove flanges, these retain the gasket on the female face, providing more accurate placement and increased gasket material options.

Many face types also offer one of two finishes: serrated or smooth.
Choosing between the options is important as they will determine the optimal gasket for a reliable seal.
In general, smooth faces work best with metallic gaskets while serrated faces help to create stronger seals with soft material gaskets.

Duplex alloys were originally created to counter the corrosion problems caused by chloride-bearing cooling waters and other aggressive chemical process fluids. They are known to be Duplex because of its mixed microstructure with about equal proportions of ferrite and austenite, duplex stainless steels are a family of grades, which range in corrosion performance depending on their alloy content. The term “Super-Duplex” is used to denote highly alloyed, high-performance Duplex steel with a pitting resistance equivalent of >40 (based on Cr % + 3.3Mo % + 16N %).
With a high level of chromium, Duplex steel plate flange provides outstanding resistance to acids, acid chlorides, caustic solutions and other environments in the chemical/petrochemical, pulp, and paper industries.
Super Duplex contains 25% chromium, 7% nickel, 3.6% molybdenum as well as copper, tungsten, and nitrogen, they are highly alloyed steel with high PREN for use in aggressive environments.
The alloy consists of around 40-50 percent ferrite in the annealed condition. The super duplex microstructure has the high strength of the ferritic grades in spite of retaining the corrosion resistance of the austenitic grades. It is common to see Super Duplex Steel being used as a practical solution to chloride-induced stress cracking. It also has outstanding resistance against sulfide-stress corrosion cracking in sour-gas environments.
Super Duplex UNS S32750 Flanges help the material withstand pitting and crevice corrosion. These duplex steel blind flanges are also resistant to chloride stress corrosion cracking, to erosion-corrosion, to corrosion fatigue, to general corrosion in acids. They have good weldability and very high mechanical strength.
Benefits of Super Duplex Flanges

  • High strength,
  • High resistance to pitting, crevice corrosion.
  • High resistance to stress corrosion cracking, corrosion fatigue, and erosion,
  • Excellent resistance to chloride stress- corrosion cracking
  • High thermal conductivity
  • Good sulfide stress corrosion resistance,
  • Low thermal expansion and higher heat conductivity than austenitic steels,
  • Good workability and weldability,
  • High energy absorption.

Applications of Super Duplex Steel Flanges

  • Heat exchangers, tubes and pipes for production and handling of gas and oil,
  • Heat exchangers and pipes in desalination plants,
  • Mechanical and structural components,
  • Power industry FGD systems,
  • Pipes handling solutions containing chlorides,
  • Utility and industrial systems, rotors, fans, shafts and press rolls where the high corrosion fatigue strength can be utilized,
  • Cargo tanks, vessels, piping and welding consumables for chemical tankers.

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