Archive for August, 2011

Shaft Bearing Failure

Introduction:

A bearing that had been in service for a year and a half was sent to undergo failure analysis (Figure 1). This bearing had been installed in the drive centrifugal pump in the R-8 plant.

Figure 1. Photograph of bearing setup
Figure 2. Photograph of inner ring showing spalling in groove
Figure 3. SEM photograph of spalling, flaking and cracking, in the groove. 200X

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Rider Roller Shaft Failure

Introduction :

A section of a failed “rider roller” shaft was sent for failure analysis (Figure 1). This shaft is designed to ride on top of cardboard as it is being rolled. It was first installed in December 97 replacing a shaft in which cracks were observed near the ends. In March 98 a crack was observed in the centre of the roll.

Figure 1. Photograph of “rider roller” indicating approximate point of fracture

Since no replacements were available at the time, welding was used to repair the crack. This caused the shaft to become out of round by 0. 140″. To repair this a hydraulic Jack was used at the centre of the roll to bend it back leaving a 0.040″ deflection that was corrected by machining. Nine days later, on April 11th 98 at 21: 00, the shaft broke on the key-way side while the machine was being set up at low speed. The roll usually operates at 550 meters per minute, approximately 630 RPM.

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Analysis of 316L Reducer Failure

Introduction:

An 8″ x 6″, 316L stainless steel reducer was sent for failure analysis (Fig 1). It had been in service for 13 months when a leak was noticed. The reducer was installed on acid storage tank, equipment number 50-200. The anodically protected carbon steel tank, contained off specification concentrated 93% sulphuric acid. The flow rate through the reducer was 400 gal/min.

Figure 1. Photograph of reducer

The tank was originally designed with a 4″ diameter carbon steel nozzle, at floor level, that connected directly to a valve (Fig  2). This lasted seven to eight years without incident. The design was changed to accommodate renovations so that an 8″ carbon steel nozzle was installed 6″ above the tank floor.

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What is Fiber Optic?

An optical fiber is a flexible, transparent fiber made of very pure glass (silica) not much wider than a human hair that acts as a waveguide, or “light pipe“, to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of optical fibers is known as fiber optics.

Fiber Optic

Optical fibers are widely used in fiber-optic communications, which permits transmission over longer distances and at higher bandwidths (data rates) than other forms of communication. Specially designed fibers are used for a variety of other applications, including sensors and fiber lasers.

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What is Silver?

Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal.  Most silver is produced as a byproduct of copper, gold, lead, and zincrefining.

Silver Coin

Among metals, pure silver has the highest thermal conductivity (the nonmetal diamond and superfluid helium II are higher) and one of the highest optical reflectivities. Aluminium slightly outdoes silver in parts of the visible spectrum, and silver is a poor reflector of ultraviolet light.

A nugget of silver

Silver also has the lowest contact resistance of any metal. Silver has been known since ancient times. Silver mining was a driving force in the settlement of western North America, with major booms for silver and associated minerals (lead, mostly) in the galena ore silver is most commonly found in. Naturally occurring silver is composed of two stable isotopes, 107Ag and 109Ag, with 107Ag being the most abundant (51.839% natural abundance).

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