Welding inspection thread 10

[RatsepAndre]

First of all I’d like to say hello everybody in community as I am new in forums and putting down my first post. It is truly good to see so many professionals in one place sharing their knowledge and experience with others.

I am at the very beginning of my engineering career in a small European country Estonia. Engineering profession is not very popular here so sometimes it is very difficult to progress and get all the necessary information that is required to become a professional. I hope that I can always address my questions and problems to this community to get practical information without too much judging cause of my inexperience.

So this is where I come to the problem. I am working for a company producing electrical machines. My job is to inspect semi-finished production and my main duties unfortunately contain lots of physical work and labour as I need and want to make sure that those products really stand up to the quality we have stated. To put it simply in my case... in the end of the day it is just a little bit more important to get the job done rather than improve as a inspector. That just means I have to work constantly by myself to keep my inspecting skills on a appropriate level. At the moment I am trying to get into welding inspection basics and have come across with some simple questions I just need to get some light in (Google just does not answer all your personal questions ). I hope this thread gives me the chance to post questions now and in the future so I dont have to make a different thread for every single problem.

NOTE: I am not native English speaker, so if I am hard to understand please ask and all other notes on my language and terminology are more than welcome. If you are about to answer the questions please use similar form trough the thread to keep it organized and make it easier to follow for other beginners, for example „Answer Question 1“ etc. All the imperfections and reference numbers are derived from ISO 6520-2007 and 5817-2007 standards.


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Question 1

502 Excess weld metal and 5211 excessive weld thickness

I have the understanding of the difference between two as well how to measure them but still would like to hear some more information on their practical application in welding quality. 502 limits the reinforcement of the butt weld but why? Is it cause to bring attention to the wrong welding parameters, for example too high amperage or is it perhaps some other reasons.

Same with the 5211. Why is it exactly necessary to limit thickness of the weld? As I understand thicker welds cause just more penetration and higher reinforcement.

 

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Question 2

Co-occurrence of 5072 linear misalignment and 502 excessive weld metal

Lets say those two imperfections occur together and 5072 linear misalignment stays within allowable tolerances. As I understand the base for measuring the 502 should be the lower plate surface or other words where the value of the imperfection is greater?

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Question 3

514 irregular surface

Does it refer to any particular type of imperfection or is it just a overall reference to note any irregularities of the weld?


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Question 4

602 spatters

Spatters are well known problem when welding and there are quite a few methods to avoid or minimize them. Welding standard ISO 5817 states that the acceptance for spatters depends on application for example material, corrosion protection... As we are working with electrical machines my believe is that in a rotating mechanisms with high magnetic fields presented and expected to have 10 to 20 years of service time should be held as clean as possible from spatters to avoid any consequences. Time to time I am still hesitating where runs the line between acceptable and not acceptable. For example big loose spatters must be removed...but what about those that are not loose but still possible to remove with mechanical tools, like pneumatic chisel. What about spray spattering that are very small in size but still cover wide areas? And so on. If anyone has a good reference for any articles or texts I would appreciate it. I also would love to hear your experience and views.


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Question 5

617 incorrect root gap for fillet weld

Definition is clear, but the standard states that „gap exceeding the appropriate limit may, in certain cases, be compensated for by corresponding increase in throat“. Do those cases have any particular lines to follow or it depends mostly on application and usually are developed inside of the individual manufacturing process?


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Question 6

Lets imagine a circular body with some short beams on sides distributed evenly around it. Following welding note is given as seen on picture below. I get confused about annotation „pcs“ as I believe it means „pieces“. Does it mean that there has to be 12 welding seams in total on left side and there is no requirement for the right side? Or does it means that both sides of the body have to be welded regarding to the requirement (24 welding seams in total)? I am thinking the second option but got into discussion about it lately and just wanted to be sure.

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[dhengr]

RatsepAndre:
What a refreshing and humble first post, from a young aspiring engineer. You should get along just fine here at E-Tips, given your approach and presentation. You might do well to start a reference library on welding, weld design and weld inspection. The U.S. AWS and Lincoln Electric are two good sources of information (info). You might also take a college or vocational/technical level class in welding and/or weld inspecting. Try to ask your questions in a form where others do not need that exact code or standard to look at, to start to answer your question. Try to frame them in a way were general knowledge of the subject (welding and weld inspection here) and not a specific sentence in a specific code paragraph is that critical, unless that truly is the issue in question. Not everyone here has a copy of every code and standard. But, there are plenty of smart people here willing to offer help. Your method of showing sketches and verbiage is very good in terms of presenting your question in a complete way. We can’t see it from here, so you do have to do a good job of explaining your problem and giving enough detail to start to address or solve it.

1.) Those welds with a high surface like 502 have a tendency to crack during weld solidification; on the surface and along the length of the weld. It also wastes weld metal, and adds to the grinding and clean-up work if they need to be ground smooth. RE: (regarding) 5211 and 5212, the weld is just to large for the joint involved, it is too wide and thus it is too high. The welder should be filling the joint with however many passes are needed so that the finished weld profile is above the base metal level. The welder should not leave undercuts and the like at the edge between (btwn.) the weld filler metal and the base metal.

2.) Most manufacturing specs./codes will have some max. allowable limits on the amount of offset as a function of pipe diameter or wall thickness. Most welding codes will too. This has to do with quality of product and workmanship and weld. Weld joint fit-up is always important w.r.t. (with respect to) the quality of the finished weld, and in many instances that mis-fit will also have negative design and stress consequences. I don’t know how to answer the second sentence of your question, except to say, the welder will try to kind of blend the two together and this leads to excessive weld size. It might also lead to a difficult root condition on the inside.

3.) no comment

4.) What causes spatter? Clean up your act, and process, procedures and methods, and things should settle down. Various finished products tolerate more or less of this.

5.) The normal geometry of a fillet weld assumes a certain configuration and a max. gap, before you have to do something to compensate for a larger gap to assure the weld throat and strength are still achieved. And, the weld will be of a lesser capacity, if corrective action is not taken, because the throat is reduced as the gap increases. And, the problem is that the corrective action or increased weld size may not be applied to compensate for the larger gap. Draw a full size Tee fillet welded joint, with a small gap, which means a good root and good root penetration. Draw the full throat and measure and calculate (calc.) its size. Now, start increasing the gap, and the root follows the gap up, and the throat gets smaller, unless you make the weld size larger. But, the drawing show a fillet weld size and all they can inspect from the outside is that weld size, so too large a gap may cause a weaker fillet weld.

6.) “pcs” = pieces. I can’t read your sketch very well, it’s too light. I would show a weld arrow as I think I see in the sketch; with fillet weld symbols near side and far side (both sides), with size and length as required (req’rd.); then with a note which said “12 thus” or “6 thus this end of tube, and 6 thus opp. (opposite) end of tube.” That’s kinda what the 2x6 pcs says. It is a good idea that you always ask yourself, ‘are my notations crystal clear to anyone else who has to read and follow them?’ Are my drawings and notes clear as to what is intended in the finished pc. (piece). Maybe I should clean it up, or rethink the notes and the way I’ve shown it, if I think it can be misinterpreted by someone else.

 

[RatsepAndre]

dhengr:

Thank You for Your response and good words. It means lot to me get feedback from older and more experienced.

Yes, bringing in too many codes and requirements can make simple things look overly complicated. ISO standard is at the moment the best tool I have at my hands to get adequate references for welding inspection. That's why I ask about specific standards. I'll take your advice and try to explain my problems in future in a more practical and simple manner if possible to make them more comfortable to answer.

I am going to look for additional reference sources as soon as I have a chance (at the moment I have filled my moments with work, school and hobbies already). Thanks for pointing out AWS and Lincoln Electr. Going to give it a shot in google. The good news is that I might have a chance to get VT2 training in 2014 which I am looking forward.

1. Waste of material and clean-up really make sense. Cracking is something I wasn't thinking about here and I really needed to know that. Now I also get the idea of the 5211 and 5212.

4. Well to be honest your answer look obvious We have a problems with spatters time to time, especially in places where spatters can get inside of the structure. Good approach on welding techniques/parameters should fix the major problem. I am also thinking of improved spatter cover to avoid spatters actually get inside of the structure if presented.

6 Yes, thanks for bringing out good points. Those kind of uncertainties just need to be cleared out as I (prospective engineer) should be able to read and design technical drawings unambiguously.


Thanks for You response again. Lots of useful information out here. I will keep posting my questions as they develop.

 

[RatsepAndre]

Question 7

Sometimes when short fillet welds are welded a crater similar to end crater occurs anywhere within the length of the seam. When it doesn’t occur at the end of the weld I assume it should be assessed as a insufficient throat thickness rather than end crater. I wonder if it is techincally the right way to to do it?

 

[RatsepAndre]

Okay this is the best I got at the moment to describe it. You can notice crater right in the middle of the fillet weld.

 

[gtaw]

502 - Excessive reinforcement (AWS terminology) produces a notched stress riser at the toes (edges) of the weld. The issue is more of a concern if the nature of the stresses are cyclic. Fatigue cracks can initiate at the toe of the weld where he reentrant angle approaches 90 degrees.

5211 - see 502 above.
5212 - excessive weld width may refer to the width of a single bead. In cases where heat input must be controlled as a means of ensuring fine grain, improved toughness, the width of the weave is proportional to the travel speed. If the travel speed is low as a result of using weave beads, the heat input increases and the slow cooling that results may promote coarse grains which typically are notch sensitive when compared to a weld bead that was deposited with higher travel speed (stringer bead).

5072 - Misalignment - forces must be transferred from one member to the next. The forces can be treated as vectors. Due to the eccentricity, the resulting forces can be rather large and can exceed the tensile strength of the weld deposit or the adjacent base metal causing a crack along the toe of the weld.

514 - Irregular surface, same as profile discontinuities ranging from incomplete fusion at the weld toe (overlap - AWS), underfilled grooves, etc. All of which can b considered to be notch like discontinuities. Notch like discontinuities can result in cracks when subjected to cyclic stresses.

602 - Spatter may be considered to be unsightly, a cosmetic concern when the spatter is visible to the consumer, it can interfere with subsequent NDT such as penetrant testing, ultrasonic testing, etc. While some spatter is expected when welding with SMAW, GMAW, or FCAW, excessive spatter is an indication the welding parameters are not optimum. Excessive arc length, excessive welding current, incorrect current polarity, magnetic arc blow, etc. can result in excessive spatter. In other cases, spatter can cause premature failure of coats applied to the weldment.

617 - Excessive root gap (root opening - AWS) reduces the effective throat dimension, thereby reducing the length of the "failure path" through the fillet weld throat.

Weld craters, whether they are located at the ends o the weld or along the length of the weld can reduce the throat dimension and reduce the load capacity of the weld. Concave, unfilled craters may crack during solidification.

I hope this helps.

Best regards - Al

 

[RatsepAndre]

Thank you for your valuable feedback Al.

Your shared knowledge on different imperfections and how they can be influenced by cyclic stress, heat input and alignment of stresses is just those things I needed to know to get more clarification into understanding the strict standards in terms of practicality.

Your comment on spatters makes sense and looks like there is actually relatively clear line between normal process (where eventually some spatters occur) and incorrect process with excessive spattering.

Cheers

 

[moltenmetal]

Sincere thanks (and stars!) to the OP and to gtaw for excellent questions and answers. This is perfect evidence of exactly how Eng-Tips SHOULD work. Now I finally have a reference to point to when a young engineer asks me why excess reinforcement is a problem!

 

[gtaw]

Happy to help.

Best regards - Al

 

[RatsepAndre]

I am glad You found this thread helpful moltenmetal. Eng-Tip seems like a promising community from many aspects to all level of engineers. I picked out this community particularly to complement my studies and work related experience. Lots of welding specific forums out there but this one looks much more applicable to me.

I am sure that if we rookies (referring to myself here) keep our questions and curiosity in organized form and well explained then people with industry's experience won't mind to share some knowledge and experience. We just need to ask right questions and not only wait for the answers come to us.


Addition to question 1 and 3

Cracking due to the cyclic stresses

As GTAW already mentioned notch like discontinuities like overlapping, underfilled grooves etc bu also butt weld reinforcement approaching 90 degree angle can develop cracks in weld seams if cyclic stresses are presented. Now...am I on the right way if I assume that that happens mainly cause in materials strength science stresses always get most critical on sharp corners (same as adding fillet to 90 degree corner on a flange to make it stronger). If that is true then removing an geometrical feature from weld (for example grinding the off the wrong angle of the weld toe) that is the cause of it can help to eliminate the problem?
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Addition to question 6

Welding note

Let's say the welding drawing above (question 6) is exactly the same except the welded beams on the right side are longer than on the left side. Does the original weld note still applies to both sides then? I am asking that cause in technical drafting many simplifications are allowed to apply only to symmetrical parts.
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[gtaw]

Unacceptable weld profiles such as undercut, overlap, excessive reinforcement, etc. can be corrected by grinding and/or welding. The goal is to remove the unacceptable condition by grinding and then if it is necessary additional weld metal can be deposited to bring the weld back to the required size.

Even conditions such as misalignment can be corrected by the deposition of additional weld metal to produce a better contour, i.e., transition between the two member. Several welding standards specify the taper/slope to be no less than 1 x 2.5.

Transitions between wide and narrow members can be improved if there is a generous radius or taper at the connection . Likewise, a generous taper or radius between thick and thin members will improve the performance of connections subject to cyclic stresses.

Europe uses a different system of welding symbols than does the US. In the US, the notation "Typical" in the tail of the welding symbol is applicable if the joints are identical. I cannot speak for the system of welding symbols used in Europe.

Regardless of which system of welding symbols you are using, the welding symbol used should be unambiguous and should be drawn to ensure it cannot be interpreted more than one way. When there is a situation where the welding symbol simply cannot adequately indicate required weld, a section view or detail can be used to represent the welding requirements. An example of situation where a separate detail of the weld joint is preferred is the skewed T-joint when the governing welding standard is AWS D1.1. A skewed T-joint having a dihedral angle between the connecting members of less than 55 degrees is neither a fillet weld or a groove joint. As such, the fillet weld symbol that specifies the required leg dimension does not fulfill the code requirement that the structural design drawing (contract drawing) specify the effective throat. The fabrication, i.e., shop, drawing is required to show the required leg dimension plus any Z-loss specified by AWS D1.1. The standard fillet weld symbol can be easily misinterpreted in this case. The question must be asked, "Did the Engineer provide the dimension for the effective throat or is the dimension shown by the symbol the required leg dimension that includes the Z-loss?" The simplest solution is to show a section through the joint with the required dimension. The detail leaves no doubt what the required weld size is.

Best regards - Al

 

[tbuelna]

RatsepAndre-

Besides the excellent answers provided to your questions regarding the specific requirements of welding standards from ISO or AWS, I would add that you are free to create your own internal QA standards that are based on the ISO/AWS standard but permit variances for your specific qualified manufacturing process.

As a weld inspector, you should consider how will you be able to verify that your production process is producing welds that meet the ISO/AWS standards. In most cases, it is not cost effective to perform a 100% NDI on all welds to check penetration, mismatch, etc. So it is common to rely on a qualified weld process for QA of the product rather than 100% NDI. The ISO/AWS standards are a good starting point for your QA procedures, but you should also work with engineering, manufacturing, M&P, etc. to develop your own internal weld process that is optimized for your specific product.

A good example is your question 4 regarding weld spatter. Large weld spatter that might break free during service can present a debris hazard for some applications, but for other applications even tiny surface damage created by weld spatter or by removing it can be a big concern in terms of fatigue/fracture. Another example is that some types of welds are more difficult to NDI than others. A butt weld is far easier to inspect by mag particle, ultrasound, radiographic or eddy current than a fillet weld usually is.

 

[RatsepAndre]

To GTAW

Thank you for excellent answers you provided again. An example of skewed t-joint was good way to make your point. I have very little experience with designing actual product drawings, so it was something worth to but in my bag of knowledge. I am though hesitating little bit if I am interpreting your thoughts in a right way on first question, so i am going to touch the same subject again. With transition between misaligned members did you mean something like that:

And could you give a additional example of wide and narrow member application. I am just little bit confused, that's all.

To tbuelna

Thank you. You did nail the subject from the inside. This is exactly what has come to my mind in recent months.

We have strongly formed production processes in our factory which relay on years of experience and practice. Most of the factory workers do not keep up with necessary qualifications and everybody are aware that the products are designed with large safety factors. It all leads to the situation where workers perform their work with traditional ways as they are used to for years and quality controls' work is to find any defects caused. This unfortunately doesn't fix the problem, cause inspecting every millimeter of product is not rational and even if one does that, the cause of the problem will still stay in the process. It ruins the functionality of quality control and communication between quality inspectors and factory workers.

That means it is necessary to fix the problems from the very beginning. Look over the welding processes, make improvements and provide training if necessary. Test welds and inspections would be good to establish reliable processes but also complement experience and knowledge of workers associated with quality control (like myself). The quality of the product should relay on visible and controlled process and quality inspectors work should rather be keeping the eye on processes and make improvements as required. It is easier and cheaper to control the process rather than fix every single product with recurring defects if talking welding or any other subject.

Well this is at least how i see things at the moment. In other hands making those kind of rearrangements in production is very complicated and time consuming process. As you mentioned it requires intense work between different departments to establish optimized processes for our specific production. Far as I am concerned this demands a very good plan. For me to make any quick changes in a large enterprise is out of question. At the moment international standards are good starting point for me. I am going to have VT2 training coming week (well there is a big problem with it though) and I am soon finishing reading few references about GMAW basics. At holidays I am planning to heat up a GMAW machine I have at home and see what the book knowledge looks like on metal. With the notes I have made from books I might start a personal reference for welding inspecting and hopefully those would be the first steps towards making things better.

 

[RatsepAndre]

Hi again to everybody after a little brake. The last post was by me discussing some questions about welding geometry and general problems in welding QA process. It might look like this thread has been already faded, but I don’t see any reasons to think that way. I have received lots of good answers and gained valuable knowledge on welding inspection subject trough this thread. Thus I will keep up with posting questions and problems as they develop and hope people to get involved.

Meanwhile I have been busy with all the other activities as we all know and I didn’t had a chance to practice some actual welding. In overall though I see a slow but stable improvement on my intentions. I have started a personal welding reference for myself which is in a very coarse form at the moment and needs lots of work. But at the end of the day You just have to have one if You want to get into assessing welding processes. I also participated in a visual inspection training and are working on a welding spark covers idea for our particular manufacturing process.

Now I will start off as usual, with few questions about welding inspection and standards:


Question 8

Excessive fillet weld throat

To be based on previous discussions I understand that too large of throat thickness is mainly concerned cause of excessive heat input that can affect materials’ internal structure. If the throat thickness is exceeding the allowed limits set by standards it might point out the problem that the excessive heat input into parent material has affected the material grains. In this kind of situation grinding down the face of the fillet will bring the weld back to allowable geometrical limits but the problem of heat input still exists as the grains have already been affected. In that case in practice it would be much more important to work with welding techniques and avoid the excessive heat input rather than concentrate on grinding down fillet face to make it look visually appropriate. Am I having a right lead here ?

Question 9

Incorrect weld toe

Incorrect weld toe is referred in ISO welding standards in two forms, angle and radius. As most of the cases I have came across the situation where angle between the plane parallel to parent material and plane tangential to weld toe is measured, thus incorrect weld toe angle. When exactly the radius on the weld toe should be taken into account? When there is a radius on the weld toe and measuring an angle is not possible or in cases where it is specified that way?

Thanks in advance
Andre

 

[gtaw]

Question 8
Few welding standards concern themselves with fillet welds that are larger than that specified by the drawing. Fillet welds that are larger than necessary is a workmanship issue that increases the cost in both time and filler metal. As the weld size is doubled, the volume is increased by the dimension of the fillet leg to the second power. In short, if you double the leg dimension, the volume is increased by a factor of four. It takes more time and more filler metal, thus increases the cost.

As for the heat input, that should not be a major issue unless the application involves operating in a low temperature environment and where notch toughness is important. There are ways to control heat input by controlling the arc voltage and amperage (minor considerations) and travel speed (major factor). The number of passes is not an issue unless the interpass temperature (temperature of the base metal adjacent to the weld)is not controlled between weld beads. In the case of austenitic stainless steels, interpass temperature control is important to mitigate the probability of sensitization and the resulting possibility of intergranular stress corrosion and possible intergranular stress corrosion cracking. In the case of carbon steel or high strength low alloy steels, the heat input is not a major concern if notch toughness is not an issue.

Question 9
The reentrant angle at the toe of a groove weld or a fillet weld (5051) represents a notch like stress riser where cracks can incubate as the angle approaches 90 degrees. The best case is when butt joint reinforcement is ground flush with the surface of the adjacent base metal, i.e., the reentrant angle is 180 degrees. The same is true with the reentrant angle at the toe of a fillet weld. The influence becomes more pronounced as the reentrant angle approaches 90 degrees. An increase in the reentrant angle reduced the for cracks to initiate in the toe of the weld.

The absence of a radius at the toe of the weld also represents a notch like stress riser, i.e., the weld does not blend uniformly into the adjacent base metal surface.

Both the reentrant angle and toe radius become concerns when fatigue is a concern. Cyclic loads within the elastic range can cause fatigue cracks to form in locations where there are notch like stress risers. Efforts to eliminate notches is important when cyclic loads are encountered. One way to minimize the notch at the toe of a weld is to improve the toe condition with a round end rotary file (carbide burr).

Best regards - Al

 

[racookpe1978]

Question 8

Excessive fillet weld throat

To be based on previous discussions I understand that too large of throat thickness is mainly concerned cause of excessive heat input that can affect materials’ internal structure.

Be aware that the European standard for fillet welds is "across the throat" (as you have shown in the sketch) but the US standard is "leg size", so the US throat across a 90 degree fillet fillet joint would be .707 as thick as an equal European notation.

Having said that, your 50 mm fillet weld throat thickness for those 12x very short, very small ribs appears excessive: too much time, too much labor cost, too much material (excess weld filler material and gas expense) and too much heat input into the bast metal where there is no apparent reason for that much stress.

A fillet weld can never be stronger than the thinner of the two base metals being joined: Otherwise, the base metal will pull through, rather than the weld metal. Evenly loaded - and your ribs are welded on both sides - neither fillet weld should be thicker than either the casing or the rib. Even if the weld is to increase heat flow from the casing to the rib (a fin in this case) the heat transfer ability is still limited by the thickness: total cannot exceed the thickness of the rib.

 

[Ron]

RatsepAndre....welcome to the forums and as dhengr noted, it is refreshing to see how diligently you are approaching your responsibilities. You already have many of the qualities of the professional you are striving to become...good luck.

I have nothing to add technically to the above discussion. You have received some excellent responses from very experienced and knowledgeable professionals. If I had anything to add I would certainly do so; however, they have covered it nicely.

I would suggest that you start a new thread from this point when you have a new question. If threads get too long, it is difficult to get through them to find appropriate answers. The forum management would prefer that technical threads not extend too long except on a single subject.

Another reason for starting a new post is that the title of the post is searchable, easier than the body text of the thread, so it helps others who might have the same or similar issues.

Best of luck and your English is quite good. Certainly better than my attempt would be at the native language of Estonia.

 

[gtaw]

I agree with Ron on all points!

Best regards - Al

 

[RatsepAndre]

Gtaw, Thank you for your response covering the subject in deeper manner. It took me quite a few times to read your post and translate it right, but really got some good answers - professional and clear as always.

Racookpe thanks for pointing out those things. The welding drawing with welded ribs was really just a example and I didn’t put any effort into designing it right. But again thanks for pointing that out, it gives me something to think about.

I agree with You as well Ron. This thread is already a bit uncomfortable to manage to myself as well. Have got really good answers in this thread and having good feeling about being in forums. I will stop adding new questions at this point and if somebody want’s to add something in they are free to do so. I am trying to post problems and questions in separate threads in the future. Thanks for the good words though…Well and don’t try to spend too much time with Estonian, I find it rather difficult language to learn But if you have chance to visit the place let me know. I will cover it up for you.

With best regards
Andre

 

[Ron]

Andre....best of luck. Keep posting and asking questions. That's how we all learn. You have tapped in to some of the most knowledgeable professionals in the world. Their answers are invaluable. I learn something daily from these forums and I have over 35 years of experience!