Key to Quality: The Sea Lawyer
by Joseph Sorrentino
August 24, 2009
For 20 years, I served in the United States Navy Nuclear SUBSAFE program. Fifteen of those years I spent as a Level III ASNT TC-1A Examiner in the visual, magnetic particle, liquid penetrant, ultrasonic and radiography testing methods. The U.S. Navy Nuclear SUBSAFE program was a high-stress work environment. Each day we performed repair, modification and overhaul of U.S. Navy submarines.
One day, someone asked me how I was able to survive in this type of work environment, and I replied that it was due in large part to my becoming a “sea lawyer.” It was only after spending time on a newly commissioned submarine tender in San Diego that I came to realize the only way I could survive was through the sea lawyer method.
As a young sailor, I felt that I had no say in what was going on, and marveled at the knowledge that some people possessed, until I was given a well-kept secret by a lieutenant commander with whom I had an argument—an encounter that changed my life forever.
As the division commander was escorting the lieutenant commander out of the nondestructive testing laboratory on the ship after our argument, the lieutenant commander threatened to get even with me. About two weeks later, I received a call to report to his office. I remember saying to myself on the way down to his office that this was payback time.
As I stood in front of the lieutenant commander, he proceeded to tell me how much he disliked me, and that he would never like me. However, he needed my help. He said he was being tasked to establish the nuclear systems repair department, which would achieve certification to perform nuclear repairs within three months. He needed a leader and a work coordinator who was intelligent and respected by the enlisted workers. I told him I did not believe it would be good for me to work with him. He said that if I did work with him, he would teach me everything I wanted to know about nuclear submarines and support me 100% in my decisions. However, if I made a mistake, he would come down hard on me.
Shortly after I accepted his offer, his knowledge and mentoring was a light in my life, and one of the techniques he shared with me was the proper use of and interpretation of standards, and specifications. The sea lawyer was a title I gave myself early in my career, and later spent four years teaching this valuable technique to students at the Navel Sea System Training Center, and continued to use throughout the rest of my career.
I found that by understanding standards, specifications and the hierarchy of directives, I could accomplish what others could not. As in the law of the land, there was the law of the sea, and in the U.S. Navy the rules were established and orders handed down from the president of the United States (commander in chief) to the secretary of the Navy, and all the way down to me.
It was during this time that I also realized that the sea lawyer method could be used in corporate policies, manufacturing, fabrication and even government agencies. Here, I will use fabrication standard requirements as an example.
Fabrication standards are important because they contain all pre-engineered acceptable workmanship and fabrication requirements. We all know that engineers design and architect the system, but a non-engineer can determine if the engineer’s drawing is correct in relationship to the fabrication document.
For example, if I’m working on a super heated steam-piping system to run a turbine for the U.S. Navy, all I need to know is how much steam pressure, temperature and volume is required. I can then verify the piping system and material of pipe, its criticality class, its acceptance criteria, the welding requirements and joint designs, the inspection method and objective evidence required to document the completeness and acceptability of the installation.
The lead document is the bible of fabrication, which can solve any vague or ambiguous work instructions. Both the MIL-STD 278 and AWS D1.1. documents define from start to finish all necessary requirements for fabricating a specific type of work. AWS D1.1 is a fabrication document in the commercial structural document, and MIL-STD 278 is for piping, machinery, pressure vessels, castings and forging for U.S. Navy ships.
These are similar documents because they give specific instructions for workmanship, welding, machining and materials. These documents also give directly or reference specific acceptance criteria, requirements for fabrication, methods of inspection, workmanship requirements and many other important fabrication requirements.
Fabrication standards are just one example of how the sea lawyer method can be applied in today’s NDT environments. It all comes down to your ability as an NDT professional to properly use and interpret standards and specifications.
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By: Ennio Curto
Posted: September 21, 2009 4:27 PM
NDE RESIDUAL STRESS - NEW METHOD
Introduction
Internal stresses are to be considered as the following: 1) Operational strains referring to loads that the material is subject and calculated 2) Residual stresses in the material caused by heat treatments or stresses caused by welding, forging, casting, etc. The new technique is able to measure the applied load and residual stress that are balanced on the surface of the material, and in a relatively large volume, at times even the same size as the entire structures. This stress is part of the metal’s elasticity field and has a three axis spatial orientation.
Description
Elastic oscillations (also called vibrations) of an elastic material consisting of elementary masses alternately moving around their respective balance positions; these movements cause a transformation of the potential energy into kinetic energy. This phenomenon takes place due to reactions (elastic forces) that the aforementioned masses produce in opposition to elastic movements; these reactions are proportional according to Hooke’s Law to the same movements. The elastic waves that are produced propagate according to a fixed speed that depends on how rapidly the elemental masses begin to oscillate.
Elastic waves of this type are called “permanently progressive”, and they propagate at a constant speed which is absolutely independent of the speed with which the elemental masses move during the oscillating motion, and therefore also their respective oscillations. It is easy to verify that the elastic oscillations, from a material point P (in which the elemental mass m is supposedly concentrated) are harmonic. In reality, due to the fact that in any moment the elastic force that is applied to P is proportional to the distance x of the point from its position of balance 0, P acceleration (caused by the proportionality between the forces and the corresponding accelerations) is also proportional to x; this is demonstrated in the harmonic movement. The impulse creates in the metallic mass a harmonic oscillation (vibration) which is characterized by a specific frequency ù² and by a width equal to dx (movement of the relative mass). If a constant impulse is produced in the metallic material, the elastic oscillation generated in the P point will also produce a sinusoidal wave with specific width, acceleration, speed and period values.
This wave is longitudinal when the direction of the vibration is equal to the P point movement, or is transversal, and in both cases the values of the results are identical; the only difference is the ¼ delay of the phase.
Impact with the metallic surface results an elastic deformation energy.
Ed = Ei – ( Ek + Ep )
Ei = Impact energy Ek = Kinetic energy
Ed = elastic deformation energy Ep = plastic deformation energy + lost energy
Ed = ½ K dx² = ½ m ω² dx² K = constant elastic material (stiffness)
Behavior elastic metals, due to new discovery
Fig. 1 Fig.2
The system works through the accelerometer mounted with a magnetic base to generate the acceleration value of the vibrations created by the device impacting on the metal surface. The acceleration value, in combination with other parameters, permits obtaining the exact value of the residual stress or load applied in the desired point. This value will appear on the display directly in N / mm ². For non-magnetic metals, wax or gel will be used to mount the accelerometer.
The system doesn’t recognize the compressive from tensile stress.
Fig .3
Quality of surface
The test method requires smooth surfaces free of oxides, paint, lubricants, oil. The indentation deep and the accurately of the test depend from the roughness of the surface. For the preparation of the surface, is necessary, must be careful not to alter the surface over certain values of heating or hardening. More practical results can be realized by using a high-speed grinder (> 12000 rpm).
Conclusion
Application of this type of non-destructive method NDT provides the possibility to measure residual stress and the effect of the service load in a very rapid and simple way on any point of the metallic surface. The testing method requires smooth surfaces free of oxides, paint, lubricants and oil. Precision depends on the roughness of the surface. This technology has demonstrated its validity over years of mechanical experimentation and has confirmed its theoretical basis. The new system provides a full-field, large area inspection, in real time to point-by-point inspection too rapid and easy
About residual stresses
The residual stress in a metal doesn’t depend on its hardness, but from the elasticity module or Young module and from its chemical composition.
The hardness of a metal indicates its ability to absorb elastic or plastic energy, but through it not possible to determine the value of residual stress. In a metal with the same hardness we will have different values of this stress. .
The residual stresses tend to equilibrate themselves in the surface of the material.
The measurement made with all the major methods, X-ray, string gauge (destructive), optical etc. the residual stress is determined between the measuring the displacement of the equilibrium point the reticule crystalline.
The method discovered analyzes the value of frequency and vibratory acceleration generated by an impulse with the subsequent reaction elastic (elastic field) from the metal.
You will realize the convenience of this technique.
1) Portable system easy to use and very swift.
2) NDT non-destructive test.
3) Repeatable in unlimited number of points.
4) All metals type (a-magnetic)
5) Don’t expensive. Effective for welding, hardened treatments, vessels control,
bridges, pipes line, aeronautics, NDT inspection for every metal types.
p.i. Ennio Curto.
Via E. di Velo, 84
36100 Vicenza (Italy)
T. 0039+0444+511819
E. enniocurto@astwebnet.it
Web site: www.scribd.com/doc/6067883/New-Technique-for-Residual-Stress-Measurement-NDT-