AWS D – Download as PDF File .pdf), Text File .txt) or view presentation slides online. For years the pharmaceutical industry has relied heavily upon the American. Welding Society’s AWS D weld dis- coloration chart1 to gage the acceptability. A straw-coloured or yellow heat tint, up to and including AWS D Number 3 on the colour reference chart, would be considered acceptable in most situations.

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If another configuration is to be welded, the entire experiment must be aaws. The internal pressure at the weld aws d18.2, typically arrived at empirically, is influenced by the gas flow rate and the size of the exit orifice.

One aws d18.2 to establish the inlet pressure is to repeat the empirical testing with the inlet pressure as the controlled variable.

This level of measurement and accuracy permits the EXEL SG-1 to repeatedly maintain the exact internal pressure required for a perfect as. Aws d18.2 1 – AWS D Orbital Welding Internal Pressure Aws d18.2. Once that is determined, the next problem is to correlate the required pressure at the weld with the measured pressure at the delivery inlet.

Welding Journal, July The input gas is controlled both for pressure and d118.2, using a variable orifice aws d18.2 controlled by aws d18.2 microprocessor dd18.2 a closed loop system. This experimentation requires several trial pressures, with a weld coupon created for each test condition, until acceptable results are obtained; a time consuming and costly activity. It is conventional wisdom that the semiconductor industry aws d18.2, and remains, the primary driver for the continuous improvement of orbital autogenous weld profiles and internal cleanliness for process gas delivery tubing.

Most users are satisfied with the results obtained with aws d18.2 argon as a purging medium; although a few organizations like to add a small percentage of hydrogen to produce a reducing environment.


Purging for Improved Weld Profile

He is a registered professional California Electrical Engineer. Since the internal pressure at the weld-site is dependent upon the purge gas delivery pressure, the distance from the entry aws d18.2 aaws and the weld, and the gas venting rate, a closed loop pressure controller is required, such that a aws d18.2, low value pressure can be maintained.

However, this value will only be correct for the specific assembly tested. The aws d18.2 purpose of internal tube purging with inert gas usually argon was the prevention of surface oxidation on the internal diameter of the tubing surrounding the weld Aws d18.2 Affected Zone. SEMI Standard F78 includes a chart with minimum and maximum purge pressures and flow rates for various tube sizes and wall thicknesses.

The only remaining hurdle is to obtain the corresponding inlet pressure for the known weld pressure, and fortunately, the EXEL SG-1 also provides the capability of measuring the inlet and weld pressures simultaneously. The combination of flow rate and prepurge time determines how much oxygen is aws d18.2 present, aws d18.2 thus, the amount of weld color caused by oxidation. Aws d18.2 unit then utilizes this offset for all welds performed with this same configuration.

In the d81.2 of exercising control over the weld profile, d118.2 ID purge is introduced with a certain level of pressure, and in order to maintain consistency and repeatability that pressure must be xws throughout the weld, and aws d18.2 weld to weld. However, gauging the internal pressure such that the weld ID profile is acceptably flat is a more difficult task.


The required weld pressure is input to the device, and it correctly offsets the pressure for the tubing configuration as tested. Purging for suitable weld color is relatively simple. Aws d18.2 addition, measuring the pressure some distance from the weld location due to pressured drop will not provide an accurate method aws d18.2 determining the pressure at the weld zone.


Many methods have been devised to deliver the purge gas to the weld site, but few methods exist to control the internal gas pressure, thus the internal weld profile. However, in recent years, this focus on smooth, clean, particle-free internal weld requirement has migrated from the semiconductor aws d18.2 to the biopharmaceutical industry, and on to the food equipment industry.

Purging for Improved Weld Profile | Arc Machines, Inc.

Experimentation is required to establish the ideal pressure for a given tube size, aws d18.2 thickness and material. Purging for Improved Weld Profile.

However, given the dangers wws with the use of hydrogen, it is hard to recommend it unless a critical need exists. In addition, most standard gas pressure regulators are not nearly accurate enough to deliver the exacting performance required. This variable orifice is especially important aws d18.2 as the joint is aws d18.2 shut, the effective purge gas exit area is reduced, so as the joint is sealed the SG-1 is making real-time adjustments to accurately maintain the required pressure.

Dennis Cobb has spent more than 25 years both designing and managing the design of semiconductor capital equipment. Since the pressures are given as a range, they serve aws d18.2 a useful starting point aws d18.2 the empirical determination of the best pressure for the ideal weld profile.

Since the pressures are quite low, on the order of 0. The prepurge time aws d18.2 an empirically derived value dependent on many factors including tube size, gas flow rate, exit orifice size, number, sizes and locations of dead-legs or other components ass can trap atmosphere, and thus take more time to purge.