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 Precision Case Studies



Citric Passivation System For Disposable Surgical Tools


Citric Acid Passivation



Stainless steel derives its corrosion resistant properties from its chromium content. The chromium, in the presence of air, especially oxygen, forms a thin, hard adherent film of chromium oxide on the surface of the alloy. It is this chromic oxide layer that is inert (passive) to the surrounding environment and gives stainless steel its corrosion resistant properties.

 

Passivation, according the ASTM A380, is "the removal of exogenous iron or iron compounds from the surface of stainless steel by means of a chemical dissolution, most typically by a treatment with an acid solution that will remove the surface contamination, but will not significantly affect the stainless steel itself." ASTM A380 also describes passivation as "the chemical treatment of stainless steel with a mild oxidant, such as a nitric acid solution, for the purpose of enhancing the spontaneous formation of the protective passive film."

 

Simply stated, utilizing a mild oxidant, such as a mineral or organic acid solution, to promote the removal of excess iron from the surface of the stainless steel will enhance the formation of a chromic oxide layer thereby enhancing its corrosion resistant properties.

 

Typically, passivation is performed with a nitric acid bath from 20 to 50% by volume. Temperatures range from ambient to 160 degrees F. Immersion times can be as long as two hours and even include the addition of a chromate salt. Nitric acid is by far the most accepted means by which passivation is performed. Recently, however, there has been an increase in the amount of industries that have successfully implemented citric acid into their passivation procedures.

 

Citric acid is an organic acid unlike nitric which is a mineral acid. It reacts with the iron much better than nitric and does not attack elements in stainless steel alloy which nitric acid does. And citric acid, overall, is a less harmful chemical than nitric acid. Nitric acid raises problems with environmental disposal, health and safety, environmental pollution, increased environmental liability and regulation, and overall complexity to utilize it. Citric acid on the other hand is derived from oranges, utilized in food and beverage products, is acceptable in some instances to go right to drain, depending upon contaminants and local environmental regulations, and much more friendlier when it comes to worker health and safety.

 

Even the process aspect of citric acid passivation is easier. Stainless steel must be cleaned prior to any passivation procedure. All surfaces contaminated with oil, grease, chips, grinding dust, lapping compound, buffing compound, coolant, and/or swarf must be removed.

 

For more information on this and other passivation system call 909-800-0920



Bearing Wash System


Bearing Washing Systems - 2500 to 6000 pounds



These Aja-Kleen Systems were designed for cleaning and preserving large bearings using solvent. The customer wanted to quickly and effectively remove machining oils and debris from heavy duty bearings. The process required using directional turbulence to clean the parts. The system below had to be capable of easily handling bearings up to 2500 pounds. The construction was heavy gauge carbon steel. The tank rear wall was made of heavy gauge plate with exterior welded structural angles. Roller bearings mounted externally at critical locations evenly distributed the load.

The system uses an oscillating elevator built of heavy wall rectangular tubing to transport the bearings into and out of the processing chamber and to position and move the bearings within the washing zone. Using the normal up/down agitation stroke of the elevator combined with a comprehensive solution turbulation system provides dynamic cleaning, better coverage and accelerated processing times. The system is electrically heated and includes Nema 12 panels with lockout-tagout disconnects, digital indicating temperature controllers, solution low level safety cut-outs and automatic digital cycle timers.

Solution turbulation is provided using vertical immersion pumps located in a rear recessed blisters. Each pump is connected to bottom mounted closed looped manifolds using multiple solution jets directed within the chamber to provide uniform turbulence of the solvent throughout the working zone.

The photo below is of a similar system built for the same customer and designed to handle larger and heavier bearings. The picture, taken during load testing, shows a 6000 pound load on the elevator platform which was easily lifted and agitated.



Aerospace Fastners Automated Cleaning System


Automated "U" Shaped Console System


RAMCO has built many unique automated washing systems. This system was built to adapt to a particular customers work flow. The line was configured in a U to run from the left around to the right using two standard RAMCO MKD SERIES. A zero pressure power feed conveyor was used at the start of the line to accumulate up to six baskets and progressively feed them into the RamTough loading position. The RamTough System as shown above uses a walking beam assembly with multiple arms to move baskets through the processing stages over roller conveyor sections. The unload conveyor at the end of the line (below) shuttles baskets ninety degrees into a final accumulation zone.



Click Here to see Automation movie

The heart of each RAMCO system is the adroit use of the elevator within each processing chamber. The elevator is used to transport components into and out of each chamber. However, its most important function is to position and move the components within the working zone. It is this aspect of its function that allows RAMCO systems to achieve superior results in washing, rinsing and drying. We call this Dynamic Flow Combination. The effect of Dynamic Flow Combination is better coverage of component surfaces, more consistent results and accelerated processing times. Click Here to see Turbo video 1

 

THE PROCESS:

PreWASH and WASH with Turbo/Filter and Oil Removal Systems - The first two stages are designed to remove all the dirt and oil using Turbo/Filters and OR6VB Oil Removal Systems with SurfaceSweep. Vertical immersion pumps are used as part of the Turbo/Filter systems. The use of vertical pumps eliminates seal problems inherent with centrifugal pumps. This is especially beneficial when using high pH, low pH or abrasive chemicals. The OR6CVS Oil Removal Systems removes floating oils from the surface of the prewash and wash stations to a remote quiet tank for separation. SurfaceSweep prevents floating oil from redepositing onto cleaned parts.



Fluorescent Penetrant Inspection

 

BACKGROUND


Fluorescent Penetrant inspection is a widely applied method used to locate surface-breaking defects in all non-porous materials (metals, plastics, or ceramics). FPI is used to detect casting and forging defects, cracks, and leaks in new products, and fatigue cracks on in-service components.

FPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, and a developer is applied. The developer helps to draw penetrant out of the flaw where a visible indication becomes visible to the inspector. Inspection is performed under ultraviolet light.

 

Dye penetrant inspection



1. Section of material with a surface-breaking crack that is not visible to the naked eye.
2. Penetrant is applied to the surface.
3. Excess penetrant is removed.
4. Developer is applied, rendering the crack visible.

Below are the main steps of Fluorescent Penetrant Inspection:


1. Pre-cleaning:

The test surface is cleaned to remove any dirt, paint, oil, grease or any loose scale that could either keep penetrant out of a defect, or cause irrelevant or false indications. The end goal of this step is a clean surface where any defects present are open to the surface, dry, and free of contamination. Surface Preparation prior to liquid penetrant application in accordance with ASTME 1417 states, "All surfaces to be examined shall be clean, dry, and free of soils, oil, grease, paint and other coatings, corrosion products, scale, smeared metal, welding flux, chemical residues, or any other material that could prevent the penetrant from entering discontinuities, suppress dye performance, or produce unacceptable background."

 

2. Application of Penetrant:

The penetrant is then applied to the surface of the item being tested. The penetrant is allowed time to soak into any flaws. The soak time mainly depends upon the material being testing and the size of flaws sought.

 

3. Excess Penetrant Removal:

The excess penetrant is then removed from the surface. Removal method is controlled by the type of penetrant used. Water-washable, solvent-removable, lipophilic post-emulsifiable, or hydrophilic post-emulsifiable are the common choices. This process must be performed under controlled conditions so that all penetrant on the surface is removed (background noise), but penetrant trapped in real defects remains in place.


4. Application of Developer:

After excess penetrant has been removed a white developer is applied to the sample. Developer should form a thin, even coating on the surface. The developer draws penetrant from defects out onto the surface to form a visible indication, a process similar to the action of blotting paper. Any colored stains indicate the positions and types of defects on the surface under inspection.

 

5. Inspection:

The inspector will use visible light with adequate intensity (100 foot-candles is typical) for visible dye penetrant. Ultraviolet (UV-A) radiation of adequate intensity (1,000 micro-watts per centimeter squared is common), along with low ambient light levels (less than 2 foot-candles) for fluorescent penetrant examinations. Inspection of the test surface should take place after a 10 minute development time. This time delay allows the blotting action to occur. The inspector may observe the sample for indication formation when using visible dye, but this should not be done when using fluorescent penetrant. Also of concern, if one waits too long after development the indications may "bleed out" such that interpretation is hindered.

 

APPLICATIONS

Semi-Automated System


This Semi-Automated System consists of five steps - Penetrant, Dwell, Spray Rinse, Dry, and Developer stages . It processes a complete family of parts used for aerospace. The line is constructed from four stainless steel modular MK Systems and runs left to right.

The penetrant stage, below left, is isolated and includes a long connecting conveyor with drain-back line for collecting penetrant. In this particular application two different penetrants are used and are isolated using separate penetrant tanks and dwell conveyors. The penetrant tanks are made on casters and the dwell conveyor sections free standing for ease of mobility.

The Spray, Dry and Developer Stations, photo below, is built upon a heavy duty I beam fabricated base for accuracy, stability, ease of shipping and installation. The control pedestal (far right) includes a main Nema12 panel.

 

Fully Automatic Dye Penetrant Systems

This RAMCO Fully Automatic Dye Penetrant System was designed for ceramic bearings. The bearings are processed in batches of 100 (shown below) in a fully automated system using RAMCO transport/oscillating elevators as the basic building block for each of the stages. The bearings are processed through penetrant application, excess penetrant removal and hot air knife dryer as per specification. Exclusive RAMCO features include Multiple Rollover, MultiPort Oscillation, RamTough Automation, and MultiZone Spray. RAMCO can design manual or fully automated systems to accommodate water soluble or oil based penetrant processes.

The operator loads a four tray carrier at the beginning of the line and unloads at the end of the line ready for inspection. A multi zone zero pressure power conveyor is used to pre-stage and feed carriers into the automation system. The entire process automated using RamTough Automation. Each stage is a standard modular RAMCO MK Series Immersion System that has been modified to fit the application. Automatic opening and closing covers are included on each stage. The bearings are immersed in a water soluble dye penetrant and allowed to drain under the closed cover for a preset cycle time.


RAMCO has built many more Fully Automated and Semi-Automated FPI systems. Please consult our factory for further information

This Fully Automatic Dye Penetrant System incorporates a number of key RAMCO attributes. Transport/oscillating elevators are the basic building blocks for each of the stages. Exclusive RAMCO features include MultipleRollover, MultiPort Oscillation, RamTough Automation, and MultiZone Spray. RAMCO can design manual or fully automated FPI systems to accommodate water soluble or oil based penetrants.



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