4480新热播影院手机版

4480新热播影院手机版

Instrumentation Reference Book, Fourth Edition

Instrumentation embraces the equipment and systems used to detect, track and store data related to physical, chemical, electrical, thermal and mechanical properties of materials, systems and operations. While traditionally a key area within mechanical and industrial engineering, it also has a strong presence in electrical, chemical, civil and environmental engineering, biomedical and aerospace engineering.

The discipline of Instrumentation has grown appreciably in recent years because of advances in sensor technology and in the inter-connectivity of sensors, computers and control systems. In turn, this has meant that the automation of manufacturing, process industries, and even building and infrastructure construction has been improved dramatically. And now with remote wireless instrumentation, heretofore inaccessible or widely dispersed operations and procedures can be automatically monitored and controlled.

he new 4th edition of this already well-established reference work, will reflect these dramatic changes with improved and expanded coverage of the both the traditional domains of instrumentation as well as the cutting edge areas of digital integration of complex sensor/control systems.


Thoroughly revised, with up-to-date coverage of wireless sensors and systems, as well as nanotechnologies role in the evolution of sensor technology

Latest information on new sensor equipment, new measurement standards, and new software for embedded control systems, networking and automated control

Three entirely new sections on Controllers, Actuators and Final Control Elements; Manufacturing Execution Systems; and Automation Knowledge Base

Up-dated and expanded references and critical standards

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Rules Of Thumb : Filtration

  1. Processes are classified by their rate of cake buildup in a laboratory vacuum leaf filter: rapid, 0.1–10.0 cm/sec; medium, 0.1–10.0 cm/min; slow, 0.1–10.0 cm/hr.
  2. The selection of a filtration method depends partly on which phase is the valuable one. For liquid phase being the valuable one, filter presses, sand filters, and pressure filters are suitable. If the solid phase is desired, vacuum rotary vacuum filters are
    desirable.
  3. Continuous filtration should not be attempted if 1/8 in. cake thickness cannot be formed in less than 5 min.
  4. Rapid filtering is accomplished with belts, top feed drums, or pusher-type centrifuges.
  5. Medium rate filtering is accomplished with vacuum drums or disks or peeler-type centrifuges.
  6. Slow filtering slurries are handled in pressure filters or sedimenting centrifuges.
  7. Clarification with negligible cake buildup is accomplished with cartridges, precoat drums, or sand filters.
  8. Laboratory tests are advisable when the filtering surface is expected to be more than a few square meters, when cake washing is critical, when cake drying may be a problem, or
    when precoating may be needed.
  9. For finely ground ores and minerals, rotary drum filtration rates may be 1500 lb/(day)(sqft), at 20 rev/hr and 18–25 in. Hg vacuum.
  10. Coarse solids and crystals may be filtered by rotary drum filters at rates of 6000 lb/(day)(sqft) at 20 rev/hr, 2–6 in. Hg vacuum.
  11. Cartridge filters are used as final units to clarify a low solid concentration stream. For slurries where excellent cake washing is required, horizontal filters are used. Rotary disk filters are for separations where efficient cake washing is not essential. Rotary drum filters are used in many liquid- solid separations and precoat units capable of producing
    clear effluent streams. In applications where flexibility of design and operation are required, plate-and-frame filters are used.

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Submerged Arc Welding SAW | Submerged Arc Welding Deposition Rates | Submerged Arc Welding Flux Composition

Submerged arc welding: (SAW)

In submerged arc welding also known as hidden arc welding, submerged melt welding, or sub-arc welding the arc is struck between a metal electrode and the work piece under a blanket of granular flux. The welding action takes place under the flux layer without any visible arc, spatter, smoke or flash.

Here the weld arc is shielded by granular flux, consisting of Lime, Silica, Manganese Oxide, Calcium Fluoride, and other elements.


The filler wire used may be bare or slightly copper coated. The consumable electrode is a coil of bare round wire 1.5 to 10 mm in diameter.


Operation of Submerged Arc welding Process:

The welding action can be initiated by introducing a piece of high resistance conducting material like steel wool or carbon between the electrode and the work piece. Once the welding action has been initiated the intense heat produced by the flow of current in the high resistance path melts a path of the flux around the electrode forming a conducting pool. The molten filler displaces the liquid flux and fuses with the molten base metal forming the weld. The molten flux coating over the molten metal pool forms a blanket that eliminates spatter losses and protects the welded joint from oxidation. As welding proceeds, the molten weld metal and the liquid flux cool and solidify under a layer of unused flux. The molten flux on solidification forms a brittle slag layer which can be easily removed.


Unused granular flux material can be reclaimed and reused.

Characteristics of Submerged Arc welding Process:
Electric current is 300 to 2000A.
Power supply is 440 V.
Velocity is 5m / Min
The SAW process provides very high welding productivity, depositing 4 – 10 times the amount of weld metal per hour.


Advantages of Submerged Arc welding Process:
Thin plates can be easily welded in one pass without any edge preparation while only a slight bevelling is necessary in most other cases.
The quality of welds produced in submerged arc welding is very high with good toughness, ductility and uniformity of properties.
Submerged arc welding is most suitable for welding in the down hand or flat position although welds can be made on a straight slope.
Materials successfully welded by the process include low carbon steel, medium carbon steel, heat resistant steel, corrosion resistant steel, high strength steels and non ferrous metals like Monel metal, nickel and others.


Highspeed of execution due to the use of high currents in one or more electrode wires


No smoke


The arc is concealed, enabling the operator to work without a mask and without disturbing others nearby

Limitations of Submerged Arc welding Process:
Solid flux submerged arc welding can be used only on alloy and non-alloy carbon steel, stainless and refractory steel
The use of a powder flux means that welds must be executed horizontally, unless special measures are taken
The process cannot weld plate less than 1.8 mm thick (due to its high penetration)
It is not possible to butt joint work pieces more than 16 mm thick ; thicknesses greater than 16 mm require special preparation (bevelling).


Application of Submerged Arc welding Process:
Shipbuilding
Heavy Duty Pressure vessels
Off shore engineering

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TIG Welding | GTAW Welding | Arc Welding Equipment’s Manufacturing Engineering, Manufacturing process, Manufacturing technology

Tungsten Inert Gas (TIG) or Gas Tungsten Arc welding (GTAW):

It is an arc welding process wherein coalescence is produced by heating the job with an electric arc struck between a tungsten electrode and the job. The electrodes used in this process are made of either Tungsten or Thoriated Tungsten. Thoriated Tungsten electrodes run cooler than plain tungsten electrodes and maintain square arcing ends but it is more expensive.


Shielding gas:

A Shielding gas (Argon, Helium, Nitrogen, Carbon dioxide or a mixture of gases etc.) is used to avoid atmospheric contamination of the molten weld pool. The inert gas blanket shields the entire weld area from the atmospheric attack eliminating the need for any flux. General inert gas used is Argon though Helium or a mixture of the two may also be used. A filler metal may be added if required.


Commercial grades (Shielding gas) used for welding are 99.9% pure. Argon is 0.38% heavier than air and about 10 times heavier than Helium. Both gases ionize when present in an electric arc. This means that the gas atoms lose some of their electrons that have a negative charge. These unbalanced gas atoms, properly called positive ions, now have a positive charge and are attracted to the negative pole in the arc.


When the arc is positive and the work is negative, these positive ions impinge upon the work and remove surface oxides or scale in the weld area. Argon is most commonly used of the shielding gases. So Argon is suitable for welding thinner material.


Whereas Helium produces a higher arc voltage than Argon. This makes it more suitable for welding heavy sections of metal that have high heat conductivity or for automatic welding operations where higher welding speeds required.

TIG Welding Polarity:

The current source may be either DC or AC depending upon application. DC straight polarity arc is used in metals other than aluminium and magnesium including copper alloys, cast iron, steel and stainless steel. It gives good heat concentration and produces welds that are deep and narrow. Welding rates are high and there is less distortion of base metal. DC reverse polarity is not generally used because it produces shallow and wide welds. AC arc is used for welding aluminium, magnesium, cast iron and a number of other metals. Penetration with AC arc is midway between the penetration produced by DC direct polarity and DC reverse polarity.


The process is most suitable for low gauge sheet metal welding and cannot compete with conventional shielded metal electrode welding for welding of heavier gauges due to the cost of inert gas.

TIG Welding Process:

A high frequency, high voltage (100 kHz to 2 MHz, 2000 volts) low amperage current supply is often used in TIG welding to initiate the arc. This is to avoid the contamination of the electrode caused when the arc is initiated by short circuiting with the work piece. When electrode tip reaches within a distance of 3 to 2 mm from the job, a spark jumps across the air gap between the electrode and the job. The air path gets ionized and arc is established.


The superimposed high frequency current causes a spark to jump the gap between the electrode and the work piece. If a high frequency source is not available the arc can be initiated by scratch starting using copper striker plate to limit electrode contamination. Tungsten inert gas welding can be done in any position. Welding speeds of the order of 400 to 1000 mm per minute have been attained by manual process. The process can also be adapted to mechanized and automatic operation.


Advantages:

1. No flux is used, hence there is no danger of flux entrapment when welding refrigerator and air conditioner components.

2. Because of clear visibility of the arc and the job, the operator can exercise a better control on the welding process

3. This process can weld in all positions and produces smooth and sound welds with less spatter.

4. TIG welding is very much suitable for high quality welding of thin materials (0.125mm)

5. It is a very good process for welding Nonferrous metals (Aluminum etc.) and Ferrous metals.


Disadvantages:

1. Tungsten if it transfers to molten weld pool can contaminate. It is Hard and Brittle.

2. Filler rod end can cause weld metal contamination

3. Equipment costs are higher than that for flux shielded metal arc welding.

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