ISO specifies the general requirements and tests for safety devices for fuel gases and oxygen or compressed air incorporating a flame (flashback). Gas welding equipment -- Safety devices -- Part 2: Devices not incorporating a flame (flashback) arrestor. IBEDA offers dry-type flashback arrestors (FBA) with flame barriers, gas non- return valves, thermal shut-off valves according to EN and ISO
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Title of Legally Binding Document: Flash Back Arrestor (Flame Arrestor) Number of Amendments: Equivalence: Superceding: Superceded by. A flashback arrestor or flash arrestor is a gas safety device most commonly used in oxy-fuel welding and cutting to stop the flame or reverse flow of gas back up. Regulator (DG91N) High Gas Flow Flash Arrestor available in CGA “B”-9/16, 3/8” & CGA “C” ½” In Line and Point of Supply Flashback Arrestors The DEMAX Flame Tech Flash Cover of "Epub Flame in the Mist (Flame in the Mist, #1.
While developing, closely watch as the photoresist is removed from the wafer and dissolved. For the given parameters, the photoresist takes approximately 30 seconds to develop.
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When most of the unwanted photoresist has dissolved in the developer, rinse the samples thoroughly under running water, gently blow dry the samples using a nitrogen or air gun, and inspect the samples with a microscope to ensure all undesired photoresist has been removed. If needed, the samples can be immersed again in developer; however, one should be careful not to overdevelop the samples as the desired photoresist patterns could also be damaged. If the desired patterns are damaged or defective, the photoresist can be removed with acetone and steps 2.
This step heats the photoresist above its glass transition temperature, reflowing the photoresist and partially repairing roughness which occurred during the developing process. Using Teflon containers and the necessary protective equipment, immerse the samples in improved buffered oxide etchant BOE.
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BOE contains HF, which etches the silica not covered by photoresist to form circular silica pads on the silicon wafer Figure 2a-c. Improved buffered HF produces a smoother etch, minimizing roughness in the resulting silica circles. After approximately minutes depending on the patterns, sample sizes and number of samples , remove the samples from the BOE using Teflon tweezers. Carefully rinse the samples in running water.
The silica has been removed when the samples become hydrophobic.
After etching, rinsing, and drying the samples, inspect them using an optical microscope. Check to make sure the desired patterns have been etched completely and all the unwanted silica has been removed. If needed, return the samples to the BOE for further etching. One should be careful not to overetch the samples, or the circular patterns underneath the photoresist may be damaged. Once BOE etching is complete, thoroughly rinse the samples in deionized water and blow dry.
If the samples are on large pieces of silicon wafer, it is also recommended to cut them using a dicing saw or diamond scribe into smaller pieces with individual rows of silica circles. Individual rows of circles are etched more quickly and uniformly in the XeF2 etching step 2. Silicon dust produced by the cutting is removed during cleaning in the next step.
Using a XeF2 etcher, undercut the silicon beneath the circular silica pads to form silica microdisks Figure 2d-f. The number of XeF2 pulses and the duration of each pulse depends on the amount of silicon in the chamber and the type of XeF2 etcher used. Depending on the exact size of the disk and the amount of XeF2 undercut, a slightly higher or lower intensity and exposure time may be needed to form a microtoroid. It is important that the center of the laser beam and the center of the microdisk are aligned, so that the silica microdisk will form a smooth, circular microtoroid.
Representative Results The microsphere and microtoroid devices can be imaged using both optical microscopy and scanning electron microscopy Figure 1d, e and Figure 2h, i. Today the industry standard is to use dry flashback arrestors with at least two safety elements. Dry type[ edit ] Dry flashback arrestors typically use a combination of safety elements to stop a flashback or reverse flow of gas. This type is typically found in cutting and welding applications all over the world.
They work equally effectively in all orientations, and need very little maintenance. The simplest flashback arrestor consists of a metalic tube filled with iron wool, which cools the flame below the ignition temperature. Depending on the application they are also often used at the torch side as an additional safety device.
Flashback arrestors help prevent: Further gas flow in the case of pressure shocks. The combustion of petroleum products containing sulfur compounds produces undesirables such as sulfuric acid and sulfur dioxide.
Catalytic hydrotreating processes such as hydrodesulfurization remove sulfur compounds from refinery product streams. Sweetening processes either remove the obnoxious sulfur compounds or convert them to odorless disulfides, as in the case of mercaptans.
Oxygen Compounds. Oxygen compounds such as phenols, ketones, and carboxylic acids occur in crude oils in varying amounts. Nitrogen Compounds. Nitrogen oxides can form in process furnaces. The decomposition of nitrogen compounds in catalytic cracking and hydrocracking processes forms ammonia and cyanides that can cause corrosion. Trace Metals.
Metals, including nickel, iron, and vanadium are often found in crude oils in small quantities and are removed during the refining process. Burning heavy fuel oils in refinery furnaces and boilers can leave deposits of vanadium oxide and nickel oxide in furnace boxes, ducts, and tubes.
It is also desirable to remove trace amounts of arsenic, vanadium, and nickel prior to processing as they can poison certain catalysts. Crude oils often contain inorganic salts such as sodium chloride, magnesium chloride, and calcium chloride in suspension or dissolved in entrained water brine. These salts must be removed or neutralized before processing to prevent catalyst poisoning, equipment corrosion, and fouling.
Salt corrosion is caused by the hydrolysis of some metal chlorides to hydrogen chloride HCl and the subsequent formation of hydrochloric acid when crude is heated. Hydrogen chloride may also combine with ammonia to form ammonium chloride NH4Cl , which causes fouling and corrosion.
Carbon Dioxide. Carbon dioxide may result from the decomposition of bicarbonates present in or added to crude, or from steam used in the distillation process. Naphthenic Acids. Major Refinery Products Gasoline. The important qualities for gasoline are octane number antiknock , volatility starting and vapor lock , and vapor pressure environmental control.
Additives are often used to enhance performance and provide protection against oxidation and rust formation. Kerosene is a refined middle-distillate petroleum product that finds considerable use as a jet fuel and around the world in cooking and space heating.
When used as a jet fuel, some of the critical qualities are freeze point, flash point, and smoke point.
Kerosene, with less-critical specifications, is used for lighting, heating, solvents, and blending into diesel fuel. LPG, which consists principally of propane and butane, is produced for use as fuel and is an intermediate material in the manufacture of petrochemicals.
The important specifications for proper performance include vapor pressure and control of contaminants. Distillate Fuels. The desirable qualities required for distillate fuels include controlled flash and pour points, clean burning, no deposit formation in storage tanks, and a proper diesel fuel cetane rating for good starting and combustion.
Residual Fuels. Many marine vessels, power plants, commercial buildings and industrial facilities use residual fuels or combinations of residual and distillate fuels for heating and processing. The two most critical specifications of residual fuels are viscosity and low sulfur content for environmental control.The most critical quality for lubricating-oil base stock is a high viscosity index, which provides for greater consistency under varying temperatures.
Additives such as demulsifiers, antioxidants, and viscosity improvers are blended into the base stocks to provide the characteristics required for motor oils, industrial greases, lubricants, and cutting oils. Other Refining Operations include: light-ends recovery; sour-water stripping; solid waste and wastewater treatment; process-water treatment and cooling; storage and handling; product movement; hydrogen production; acid and tail-gas treatment; and sulfur recovery.
More example sentences. By fitting the spectrum to a dual-Lorentzian, the Q factor of both modes can be determined.
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