An Overview of the Milling Machine, Its Processes, and Components

The process in which allows the creation of the variety of features on a part from cutting the unwanted material, such process is known as “Milling Process”. Milling is an important form of machining. Milling process requires tools like a milling machine, workpiece, cutter, and fixture. The workpiece is a pre-shaped material that joins to the fixture, attached to a platform on the milling machine. Along with this, there is a fixation of a cutter in the milling machine, the cutting tool has sharp teeth that rotate at high speed. The machine cuts away the material from the workpiece in the form of small chips by feeding the workpiece into the rotating cutter that allows the creation of desired shape.

As far as the construction of the machine is concerned, the parts of the milling machine are not axially symmetric; they have many features, such as slots, holes, pockets, and three-dimensional contours. Some parts can be completely fabricated by the help of milling process; as components of these parts are used in limited quantity, like prototypes, custom designer fasteners or brackets. One of the most common applications of milling is the fabrication of tooling for other processes. For example, milling the three-dimensional molds. The parts manufactured by using a different process applies to add or refines features of these parts by using milling as a secondary process. The milling process can offer high tolerance and surface finish. Therefore, for that reason milling is an ideal for adding precise features to a part whose basic shape has already been formed.

Components of Milling Machine

Milling machines can be available in several of sizes and designs. However, they have the same components that enable the work performed on three-dimensional that is about the tool. The components of the milling machine include the following sub-parts:

• The base is a simple platform that provides support to the machine, normally fixed on the ground surface. A column attached to the base connects to the other components.
• A table has “T” shaped slots along its surface. The milled workpiece is mounted onto the table surface.  The workpiece can be joined in a fixture called a vise. The vise has fixation into the T-slots, or they can be clamped directly into these slots.
• The saddle is a platform that provides support to the table and allows its longitudinal motion. The saddle is also able to move and provide the horizontal motion of the workpiece in the Y-direction by sliding along another platform.
• There is another platform that supports to saddle and table is called “Knee.”

All of the above-given components of milling machine can operate on both orientations either in vertical or horizontal which allows the creation of two distinct form of the milling machine. Horizontal milling machine sometimes called arbor milling because horizontal milling machine uses a cutter that is mounted on a horizontal shaft, which is called an arbor. On the other hand, a vertical milling machine orients the cutter vertically. It has cutter fixed inside a piece, which is called collet, and then it is attached to a spindle that is orients vertically. The spindle is located inside the milling head, which attaches to the column. On the vertical milling machine, all the milling operations performed to remove the material by using both the bottom and sides of the cutter.

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Pressure Testing: Purpose, Regulation Requirements and Its Risk Factors

Pressure Testing has a great importance among industrial processes, as it is a non-destructive test that verifies the system’s integrity of pressure shell on new or old installed tools and equipment; this mechanism also has the ability to detect tightness of a system against leakage.

Pressure Testing has equally importance in the fabrication process, and it is a last physical quality test that performs in a controlled environment. Most of the piping codes require this test, to ensure that repaired or a new piping system is capable to maintain its safety against rated pressure and leakage. 

Most of the regulatory and enforcement agencies compliance to piping codes that mandates for the construction of the system. Nowadays, Pressure testing is mainly preferred due to good safety considerations, whether Pressure Testing is legally backed or not, it serves constructively by protecting works and public.

Pressure Testing establishes a pressure rating for required components. It may also be used to establish a safe rating by calculating various special systems. Before start-up of new systems, Pressure Testing is performed to confirm the integrity of vessels and to obtain relevant certification.

Regulation Requirements for Pressure Test

Pressure Testing is also demanded by the regulation requirements. The important points of these regulation requirements are given below:

• By using the hydrostatic method, all the pressure piping leak tests must be conducted.
• A pressure piping system will not test at a temperature that is colder than its minimum allowed temperature.
• When conducting a Pressure Test, a contractor must considered the ductile-to-brittle transition temperature and the possibility of brittle fracture.

The biggest advantage of Pressure Testing is that it can be performed at low working pressure. The fatal disadvantage of pressure testing, exposure to aged equipment with poor toughness could result in the brittle fracture.

From the above discussion, it can be concluded that the pressure test procedure confirms safety. The purpose of such procedure is to ensure pressure tests are conducted safely and effectively. They apply to mechanics, supervisors, inspectors and subcontractors responsible for pressure tests. Pressure tests are performed to verify the reliability, and leak tightness of pressure systems. A pressure test is required for a new pressure system before use or an existing pressure system after repair or alteration.

Understanding The ASME Standards

ASME (American Society of Mechanical Engineers) is technological association that maintains standardization of equipments for the industries of processing & mining, which involves with items like pressure vessel, boiler and inspection piping. The role of the society is to maintain checks and balances for industrial inspection by the help of volunteer engineers, which are entitled to monitor about predefined aspects of standard for manufacturers and operators operating those mechanical equipments in machining shop. Manufacturers tend to acquire ASME U-Stamp certification, so they could reveal to their consumers about the maintenance of standards while using modern equipment, and they can acquire their services without any hassle. Moreover, it further reflects that firm endows a healthy reputation among industry wide professionals, and certification has bound the company to adopt standards of optimal safety in the production of their products or services.

The certification of ASME U-Stamp also assures that manufacturing company is using pressure vessels and boilers in the synthesis of industrial process are not threat to life. Such kind of industrial apparatus contains excessive pressure & elemental wear and tear, so their usage needs to adopt those standards and protocols of certification, useful in reducing the aspect of malfunction & optimization of productive efficiency of equipment. The welding or other technical equipments that use pressure vessels and machinery must be capable of regular refurbishments, repairs and parts replaceable.

Maintenance Of Quality Assurance:
To achieve optimal operation of welding, there is more than one factor that supervises the whole process from preliminary point to production of product. To get into the listing of certified welding shops, the two levels i.e. machine operation refurbishment and repair must be adopted for future mechanical upgradation of apparatus, so manufacturers or retailers of such an equipment caters to include reusability factor in the machinery. For that sake, pressure vessel manufacturer as well as engineering board of ASME U-Stamp certification inspects the equipment for optimal output.

Generally, physical magnitudes of industrial equipment aren’t small, the large welding machineries comprise of small components which need to be refurbished during different phases of production. Having engineered at component level enables these machines to undergo raw and hard materials in rough condition. The process of excavation and production demands different mechanisms, capacities and orientations. The mechanical operation of these large machines may get damaged during completion of required processes, so machining and repair at component level becomes more easy. Concisely, certification benchmarks ASME U Stamp companies for optimal function of equipment involved in the industrial synthesis.

The achievement of ASME U-Stamp Certification doesn’t involve complex procedure, the inspection to monitor about standards is conducted by respective field experts. The professionals and engineers constituting this association, utilize their skills to prove durability and capability in technology related industrial processes involved in machining shop. Maintaining these procedures for machinery ensures continuity in production and optimal return of investment for the costs along with safety measures for workers.

Metal Fabrication: Its Processes & Applications

A process in which metal structure undergoes the cutting, bending and assembling processes is known as Metal Fabrication.

Processes of Metal Fabrication

Now we will discuss one by one of each process in detail:

Cutting

Metal cutting is done with the help of different automated and manual tools such as saw, chisel or shear. It also includes process of torching that completes by use of torches and via Computer Numerical Controls (CNC) cutters.

Bending

Metal bending is done with the help of manual or powered hammering. It can also be done with the use of pressure brakes. Most of the CNC-Controlled backgauges utilize hard stops to position cut parts, in order to place bend lines in the correct position. As technology is getting advance, now there are several offline programming software, which can configured to make program for any CNC controlled press brakes machines.

Assembling

The process of assembling joins the pieces of metals through welding and binding with adhesive materials. Sometimes, metal bends appear in the form of crimped seam. For fabrication, structural steel and metal sheets are the usual starting materials.
These materials are mostly present along with welding wire, flux and fasteners that can be used to join the pieces. Human labor and automation manufacturing processes are commonly used products of fabrication, and the shop that specializes in these types of metalwork is called Fabrication Shop.
Most of the end products are not classified as fabrication, either they have similar shape and function. The end products of metalworking, such as machining, metal stamping, forging and casting are not classified as fabrication.

Difference between Fabrication Shop and Machine Shop

Fabrication work overlaps with various metal working specialties. Machine and fabricationshops have overlapping capabilities, but in conceptual manner, fabrication and machine shops are different from each other. In fabrication shop, manufacture deals with metal preparation and assembling processes. Whereas, machine shop enables cutting of metals, but they mostly deal with the parts of machining on different machine tools. Most of the companies, involves in both types of activities that includes in fabrication and machine work.

Practical Applications of Fabrication Work

Blacksmithing Process is the core of fabrication work.  From different aspects, welders, boilermaker, millwrights is also included in fabrication work.

Metal fabrication is one of most the important process in field installations. It involves in the construction of machines as well as structures made from different types of raw material. Fabrication shop may involve in most of the processes like welding, cutting, forming and machining. These large fabrication shops offer additional value to their customers by limiting the need for purchasing personnel to locate multiple vendors for different services.

A general overview to Pressure Vessel and its Components

What is a Pressure Vessel?

A Pressure Vessel is a closed container that holds liquids and gases, in which pressure is builds by the application of heat from an indirect or direct source, a direct or indirect source of heat builds the pressure in the chamber. It is designed in such a way that pressure at which it holds liquids or gases is different from the surrounding pressure. Difference in pressure can be very dangerous, as it is evident from history that pressure vessel development and operation caused many fatal accidents.

Components of the pressure Vessel

The components of the pressures vessels are as follows:

• Shell
• Head
• Nozzle
• Support

Shell: Shell is the primary component of the pressure vessel, which contains pressure. Shell of pressure vessel is in the form of different plates, welded together to form a specific structure that has common rotational axis. In most of the vessels, the shell is a component that provides the longitudinal length of the vessel. The thickness of the shell based on the pressure and on any additional loads that created by the supports, nozzles and other attachments. Shells are available in cylindrical, spherical or canonical in the shape. Most of the shells have circular shapes, so due to their circular form the equal distribution of forces applies on it.  Horizontal drums have cylindrical shells and constructed in a wide range of diameter and length.

Head: Head is another component of the pressure vessel. All pressure vessels must be closed at the ends by another shell section or by head. Heads are made in the shape of curved rather than flat because the curved configuration of head is stronger, which allows the heads to be thinner, lighter and less expensive than the flat heads. When heads are used inside a pressure vessel, then they are known as “intermediate heads”. These intermediate heads are separate sections of the pressure vessels that permit different design conditions.

Nozzles: Nozzles are also one of the major components of pressure vessel that has insertion in the shell, which later connects to the process pipe. Depending on the design of nozzles, they can also connect to flanges or threaded fitting. Depending on the following given factors manufactures design nozzles:

• Manufactures must consider the metallurgy of the shell and nozzle.
• They must checks the internal and external projections of the nozzle.
• Before designing, they must consider the orientation of nozzle & internal and external forces that acts on the nozzle, such as pressure and piping forces.

Supports:  Support is also a component of pressure vessel that can be used to bear all the loads like, earthquake and wind loads. Depending upon the orientation and size of the pressure vessel, different types of supports are available in market. The design of this component deals with external forces (wind forces and seismic zones) and physical dimensions of the vessel such as weight, length etc.

What are the Advantages of Pressure Vessel?

Pressure vessel has the following given uses in different manufacturing industries:

• Pressure vessels are used in different industries like Petroleum refining, Chemical, Power, Food & beverage and Pharmaceutical.
• They can be used as storage of high-pressure gas, gas scrubbers, two and three phase separators and some other functions.
• They can be used in different types of boilers such as steam boilers etc. 

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Oxy-Fuel Welding (OFW)

Oxy Fuel Welding (OFW) is a metal joining process, used to join metal end pieces by heating. This process is commonly used to join mild steel. Oxy-Fuel welding is also called oxyacetylene welding because in this process mixture of acetylene and oxygen burns at intense flame of 3500^oC. Oxyacetylene gas welding consists of a group of welding processes, which joins different type of metals by heating them whether it is used with gas flame or without filler metal. When the gas flame combined with metal, it melts the surface to molten form, by allowing the welding process to take place. Oxy-Fuel welding can be used for shaping metal, cutting and brazing of metals. Oxy-fuel welding is mostly used for prefabrication of tubes, steel sheets and plates.

Oxy-FuelWelding process includes welding operations that make use of oxygen, which can also be combined with fuel gas as a heating medium. In this process, gas, fuel and oxygen are mixed in a mixing chamber with proper proportion that also a part of the welding assembly. This welding process involves a filler metal and the melting of the base metal, which can be used by means of the flame produced at the tip of welding torch.

Oxy-Fuel Welding Processes

There are following three processes that involves in Oxy-Fuel Welding.

• Oxy-acetylene welding
• Oxy-hydrogen welding,
• Pressure gas welding.

Oxy Fuel welding also known as air acetylene welding because of its industrial significance, in which combustion of air and acetylene heat is obtained. Welding with Methyl acetone- propadiene gas (MAPP gas) also uses same procedure like Oxy-fuel welding.

Advantages of OFW

There are following given advantages of oxy Fuel welding:

• A welder can control temperature of weld zone, heat input and the oxidizing or reducing potential of the welding environment that controls the welding process.
• Welding process also controls the shape, weld bead size and weld puddle viscosity as it independently adds a filler metal of the welding heat source.
• Oxy Fuel Welding is used for welding of tubes, thin sheets and small diameter of pipe.
• OFW is also used to repair welding joints, welds of thick sections. However, its repair work is not very economical, so its use is not feasible at commercial level.

Oxy fuel welding process is used in welding shops, it is mostly used for torch brazing, soldering, and many other types of operations, where its heat transfer rates and flame characteristics are not the same like that of welding.

Inspection Overview Of Pressure Vessel

Simply, a pressure vessel appears as a storage container, fabricated to accumulate pressure more than 15 p.s.i.g. In several inspections of pressure vessels at workplaces, usually numerous cracks and damages are observed on their surface. Such cracks and damages on the surface of pressure vessel result in the form raptures & leakages, even they can be risky to health and safety measures in workplace due to air poisoning, suffocation, explosion and fire. In severe case, damages in vessel can result fatal and can bring harm to ecology and property assets. Therefore, to ensure safety & health of workers, the design, manufacture, operation and maintenance of pressure vessel should be according to designated procedures & standards.

Below, the techniques & technologies handy in pressure vessel repair after inspection, by preventing premature failure and shutdown of facility:

Inspection Techniques Of Pressure Vessel:
To ensure safe operation of pressure vessel, online inspection is in the benefit of plant processing as well as surrounding environment. To find out the thickness of vessel surface, ultrasonic testing is widely conducted over industrial level. The purpose of such testing is to check regularly the thickness of metal of suspected areas with necessary equipment, if thickness of surface reaches at minimum allowable limit, then precautionary measures should be taken in order to keep plant working.

Notably, the other inspection techniques incorporate designing & maintenance of pressure relief valves along with installation of corrosion coupons & sentinel holes.

Real Time Example:
A. J. Warner, a senior engineer, who works for a refinery plant in Texas, quotes an example "Consider, for example, that a key Gulf coast refinery develops a serious problem in a pressure vessel. This will likely cause a shutdown of that unit, lasting anywhere from one day to several weeks or longer. This causes a disruption or shortage in the supply of gasoline to the market, which will drive up the cost at the pump. Therefore, it is in the best interest of everyone that pressure vessel technology remains a key focus area for the refining industry and beyond."

Keeping it in same way, Millennium Industries, a pressure vessel manufacturer at industrial scale maintains health and safety measures at its facility. Company aims to provide those industrial solutions, which have less affect over environment, impact over employees’ health, control risk factors and safe work practices.