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Improving Valve Sealing Performance and Reliability

Improving Valve Sealing Performance and Reliability

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A Primer on Fugitive Emissions

A Primer on Fugitive Emissions

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The State of Industrial Distribution in 2017

The State of Industrial Distribution in 2017

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Industry Headlines

ITT Reports 2016 Fourth-Quarter, Full-Year Results

Thursday, 16 February 2017  |  Chris Guy

On a GAAP basis, ITT Corporation delivered revenue of $588 million in the fourth quarter of 2016, reflecting a 12% decline that included a 2% negative...

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Industry Headlines

ITT Reports 2016 Fourth-Quarter, Full-Year Results

3 DAYS AGO

On a GAAP basis, ITT Corporation delivered revenue of $588 million in the fourth quarter of 2016, reflecting a 12% decline that included a 2% negative impact from foreign exchange. GAAP segment operating income decreased 12% .

In the Industrial Process segment, total revenue decreased 29% to $212 milli...

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Delta Centrifugal Rejoins VMA

4 DAYS AGO

This week VMA welcomed back associate member Delta Centrifugal Corporation of Temple, TX after a one year absence from the association.

Delta produces custom-made castings. Delta’s operations include Texas Stainless, Inc. Texas Stainless is a metals distributor and sells castings produced by Delt...

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How New U.S. Policies Will Affect the Chemical Industry

5 DAYS AGO

“In 2017, barring a recession in the U.S. and Europe or a slowdown in China, Moody’s Investor Service expects EBITDA in the chemicals industry to slip by 1 or 2% year-over-year.”

A new report from PwC predicts that the Trump administration “is likely to embrace policies that are...

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$2.2 Billion Investment Approved for Mad Dog Phase 2 Project

6 DAYS AGO

BHP Billiton has approved expenditure of $2.2 billion for its share of the development of the Mad Dog Phase 2 project in the Gulf of Mexico. During the fourth quarter of 2016, BP, which holds a 60.5% participating interest, sanctioned the Mad Dog Phase 2 project.

Mad Dog Phase 2, located in the Green...

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Philly Fed Manufacturing Conditions Continued to Improve in February

4 DAYS AGO

The index for current manufacturing activity in eastern Pennsylvania, southern New Jersey and Delaware increased from a reading of 23.6 in January to 43.3 this month and has remained positive for seven consecutive months. The share of firms reporting growth continues to increase: More than 48% of the ...

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Industrial Production Down 0.3% in January

5 DAYS AGO

Industrial production decreased 0.3% in January following a 0.6% increase in December. In January, manufacturing output moved up 0.2%, and mining output jumped 2.8%. The index for utilities fell 5.7%, largely because unseasonably warm weather reduced the demand for heating. At 104.6% of its 2012 avera...

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Checking Metal Materials With a Magnet

materials_q_and_a_graphicQ: I’ve seen people checking metal materials with a magnet. Is this a useful method of sorting materials, and if so, how does it work?

A: Valve companies deal with a large number of pure metals and alloys due to the variety of applications in the process industry. Occasionally, alloy identification must be performed on parts due to customer inquiries, mix-ups in bar stock, questionable machining characteristics or for some other reason. Although positive material identification (PMI) has become quite common, a PMI tester is not always available in a timely manner. One common identification/sorting technique that is often overlooked—and sometimes misapplied—is magnetic inspection. Magnetic inspection can save a lot of time by quickly proving a material is not what it is supposed to be.

Categorizing Materials by Magnetic Attraction

Magnetic inspection refers to categorization of a material by observation of its magnetic attraction force. Various alloy groups behave differently when exposed to a magnet. However, virtually all alloys fall into one of four behavior categories:

  • F - Fully magnetic:Materials such as carbon steels, alloy steels.
  • N - Never magnetic: Materials such as aluminum alloys, copper alloys, most nickel-base alloys, some stainless steels, etc. These materials exhibit no perceptible attraction to a magnet.
  • P - Partly magnetic: Materials such as some stainless-steel castings and wrought products. These materials exhibit some attraction to a magnet, but less than the fully magnetic materials.
  • V - Varying:Materials such as some stainless steels, nickel-copper alloys, etc. These materials may or may not be attracted to a magnet, and when attracted to a magnet, the attraction strength may vary significantly, depending upon the exact composition and processing history.

Information on magnetic characteristics can usually be found in material product literature.

An unknown material’s magnetic characteristic is determined by placing a magnet against the material and observing whether it is attracted or not. If there is no perceptible attraction, the material falls into category “N”. If there is attraction, decide whether it is full or partial. This is best done by placing the magnet against the unknown material and then bringing a piece of carbon steel into contact with the opposite end of the magnet. If the carbon steel easily removes the magnet from the unknown material, then the unknown falls into category “P”. If the magnet is attracted with approximately equivalent force by both materials, then the unknown falls into category “F”. In performing this comparative test, it is important that the surface contour and finish of the unknown piece and the carbon steel piece be the same (preferably flat). It is also important that both parts are more massive than the magnet or, in the case of sheet materials, that both parts have approximately the same thickness.

Limitations of Magnetic Inspection

The most important thing to keep in mind regarding magnetic inspection is that, although it can prove that a part is not a particular material, it cannot prove that a part is a particular material.

Here are some example applications of magnetic inspection:

  • Example 1: Records have been lost for a valve shaft that has been stored for several years. It is assumed the shaft is probably either S17400 or S20910, since these are the standard materials of construction for this part. Magnetic inspection determines that the shaft is fully magnetic. S17400 is fully magnetic, whereas S20910 is never magnetic. Therefore, the shaft is not S20910, and may be S17400. It could also be some other fully magnetic material.
  • Example 2: A customer orders a “316” valve body, but upon receipt of the body finds that it is slightly magnetic. The customer calls and complains that he did not receive a “316” body as ordered, because he knows that 316 stainless steel is never supposed to be magnetic. The problem with this logic is that the body is not 316, but rather is a CF8M casting, the equivalent of 316 wrought material. The chemistry of the cast material is adjusted to intentionally produce a small percentage of “ferrite,” which is a magnetic phase. This renders the casting partly magnetic, and often leads to this type of confusion. This highlights the importance of accuracy in material designation and product form (cast, wrought, etc.) when using magnetic inspection.
  • Example 3: A casting is sent to inspection for a material check because the machine operator noticed its machining characteristics were unusual. The casting is supposed to be CW2M. Magnetic inspection may save a great deal of time vs. performing a PMI. The casting is found to be partly magnetic. This proves that the casting is not CW2M, which is never magnetic.
  • Example 4: Same situation as example 3. This time, the material is found to be non-magnetic. This does not mean that the material is CW2M. This is one of the most important limitations in magnetic inspection. Magnetic inspection can prove that a part is not a particular material, but it cannot prove that a part is a particular material. In this case the casting should be further evaluated by PMI or some other method to determine if it is CW2M or some other non-magnetic material.

Remember that magnetic inspection can be a valuable, time-saving technique, but if used improperly it can produce erroneous identification of materials.

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