ss pipeline fracture or leakages on welding joint

It would be interesting (and helpful) to know the process that you are using to weld the pipe. If it is being Tig welded I would say offhand that there has not been sufficient flushing of the pipe prior to welding and the backshield gas has not been ample to prevent contamination of the weld on the inside of the pipe.

i am very much convinced that there is contamination with soap when we r doing welding. please let me know how can i control this contamination. what is this backshield gas. please inform me

Before start of any welding it is essential that the fit up for the joint has been inspected for the following

1) Clean metal surfaces at weld area and no fluid inside the pipeline.

2) Uniform gap all through the fit up.

3) Pipe outside surfaces are in same alignment.

Metal surfaces should be free of any foreign materials. Presence of foreign materials like dirt, paint, contaminated product etc in the metal will get deposited in the weld while welding and affect the weld quality.

Regarding your operations, it is always better to go for emptying the line after each pumping or keep it in circulation even by providing additional bye passes. In your case I cannot confirm but you can also keep the line empty by pigging the pieline after each pumping.

Your entire process need to be studied to arrive at a solution.

Regards

Srijit

Welds done on SS316NG, will not crack. This piping was developed just for this and other industries some 30 or more years ago.

Dear Sir,

The pipe leakage through the welding joints or even pipe bursting under high pressure is a very common failure in process industries esp. steam and chemicals etc.

Without shutting down the plant also the specialist is in a position to plug the steam leakage or any other leakage of base liquid in a chemical process plant.

If you call such a specialist he will be in aposition to attend the said leakage problem meticulously.

Regards,

Ulhas Pradhan

P.S. Otherwise one has to train in plant specialist to attend the leakages on line.

I agree with Thrudd, it sounds like the pipe is getting bound up because it isn't designed for steam. I know the process fluid is probably basic, but have you looked at the possibility of chloride stress corrosion cracking or some other form of chemical attack on the piping?

Are you referring to "soap" as a by product of black liquor drying in a paper mill that is refined into tall oil? I am assuming this is the case and if so allot of people may not understand that this is not the usual soap they are thinking of. In the paper mill where I work we use carbon steel for soap transfer piping and have very little problems with it. After it is mixed with sulfuric acid and made into tall oil then it is transferred via 316L or in some places of high brine content hastelloy. It sounds to me that you may have one or more reasons for your problems with the stainless steel pipe. Although stainless is very good for corrosion it needs to be welded very carefully with a proper purge so that you get the full benefit of using it.

1. faulty welds with bad root pass (if the root is not 100% fused all around the pipe it makes for a very good place for a crack to start)

2. improper supports (allows excessive stress and movement on the piping)

3. over pressuring with steam (this is pretty hard to do when applying steam to soften and free up a soap plug, most stainless pipe can handle the 150 lb. steam that is usually used for this with no problems).

4. high vibration from pump (It is my experience that more 316 stainless steel welds fail for this reason than any other but it is usually associated with item 1 or 2 above) I am assuming you are using sch. 10 piping and anywhere you can isolate vibration in the pipe will be helpful.

pipewelder

Take shut down of the pipeline if necessary and check/ensure the following.

1) Whether gaskets used are compatible to higher temperatures?

2) Ensure pipeline is sufficiently supported and no additional load is acting on the pipeline by means of any strainers/flow metres or self weight due to vertical/inclined portion of the line.

3) Flange faces remain aligned to hold the gasket uniformily.

4) Flange faces are not permanently damaged during maintenance activities.

5) Cracks in weld joints can be due to poor quality of weld joints. One of the reasons can be due to wrong selection or poor quality of welding rods (or welded during bad conditions of weather). Hope it has been welded by a competent/qualified welder. You can go for radiography of weld joints to ensure that weld joint is free of weld defects like porosity, lack of fusion, hair line cracks which can develop later, etc...etc...Can you specify the pipe size & schedule/thickness.?

6) Ensure no abnormal vibrations occur while soap transfer/pumping which can lead to weld cracks. Can you specify the density and solidification temperature of product, Is it Plam Fatty Acid PFAD which gets solidified at normal temperatures?

7) Also please specify the type of steam tracer if it is in the subjest pipeline under discussion.

8) However take hydro testing of the pipeline at 1.5 times its design pressure before taking the line back to service.

The welds should be properly tested prior to usage so that slag inclussions could be remove through the use of chipping hammer. secondly, the number of elbows should be reduced because elbows are the most stressed point on your line.

If pipe is suspended on hangers you should have no problems with expansion breaking welding if you use flex at both ends. Joints are another issue depending on alkalinity of soap ss steel gaskets with embeded gasket rings again choosen to avoid chemical reaction may help or good old fashioned varnish used with gaskets may work better than most modern gasket seals. If pipes are held rigid you will have on going problems loosening up the hangers to allow movement may help with flex at both ends. Usually if gaskets go after putting steam though, the gaskets were already on their last legs the same with welded joints and if this is the case your preventive maintenance system is not up to scratch and you need to improve it before some one gets hurt and your down time increases.

I am agreed with u as our preventive maintenance system is not that much good. we have three soap sophonification plant and four driers which are running continuously. so we have to wait for breakdown to do the preventive for other things.please guide me to implement some good systems for maintenance.

for the leakage from the flanges i suggest you to use RTJ flange with Oval ring SS gasket (same grade for example if the flanges SS-316L use gasket also in SS-316L).

For the leakage and cracks at weld joint please make the WPS, WPQ and PQR as per the job and get the welding done on the samples and see the following test results:-

1. DP testing of weld joint
2. Radiography of the weld joint
3. Tensile test
4. Root Bend
5. Face bend
6. Impact
7. Hardness

Please also check the compitability of the filler metal and the welding electrode with the parent metal. I suggest to use the following welding process for the welding:-

1. GTAW for root run
2. SMAW for filling and caping

The weld joint construction should be as per ASME section - 9 also the welding procedure format is available in ASME Section - 9 with all the guidlines.

Hope this will help you

i m very much thankful for ur advice please let me know about GTAW AND GMAW welding where i can get more knowledge about ASME section 9

what is this WPS,WPQ AND PQR

Hi

WPQ-Welder Procedure Qualification

WPS-Welder Procedure Specifiation

PQR-Procedure Qualification Reords

These are terms connecetd to welding or QA/QC requirements in which sample testing of weld joints is done for qualification of Welders as well as welding procedures which need to be complied before any welding operation on the job.

Standard sample test pieces so welded are tested for radiography, tensile strength, hardness etc for ensuring welder/weld quality.

Srijit

please tell me about jacketed line is it adviceable or not if yes why if not why

now we r doing 3/8 inch copper tracing suggest us good copper tracing

My dear friend

Please give the product & pipeline specifications for any one to analyse the problem. You mentioned earlier that you have tracer lines not giving results. Now you are going for copper tracers. You already have weld and flange leakages. I think you are trying some short cut methods without analysing the problem.

Srijit

thanks for ur advice what ur saying its true without analysis management is going for jacketed pipeline which will be more costly. so let me do analysis first.our product is soap and line is dn 80.

Why dont you check with some experts or even try whether pigging of pipeline will solve your problem of product contamination rather than going for costlier jacketing?

what is this pigging process

i m not on my home ground to consult somebody

please advice me

Pigging is the process of passing soft/hard pig through the pipeline using compressed air. This is advisable for pushing the line product into the tank/mother vessel by air compressor pressure applied behind soft/hard pigs so that pipeline is kept empty. Repeating the process twice or thrice will make the pipeline inner surface clean.

There are different types of pigs available in market.

Soft Pigs for pigging are mere cylindrical sponge of diameter larger than pipeline diameter.

Hard Pigs are two or more Polyurethane hard cups or cup shaped discs mounted on a rod one behind the other. These assembled pigs are available in the market in different sizes suitable for various pipe sizes and products or can be designed by the manufacturer. Your pipeline elbows need to be of 6D radius or more for passing hard pigs.

Also you need to install pig launchers (pipe spool of larger dia to insert the pig) at one end and pig receivers at the other end for pigging operations. Pig launchers are also readily available in the Indian market to my knowledge or can be fabricated and welded.

Again coming back to your plans, I would not prefer to go for jacketing (even though I do not know much of jacketing) unless your weld leaks are confidently arrested. Analysing your case it seems that your welds are defective and to add the problem repairs have been attended without PQR/WPS (I guess).

Still to add options, but not on lines with defective welds, at the same time costlier, you can provide electrical heat tracers where the pipelines can be maintained at higher temperatures and thereby the products so that pumping will be easier and avoids any solidification or contamination.

I am not from soap industry, hence do not know the product specifications and requirements to suggest among these options. But I remember you have only 60 M of pipeline and is not a difficult issue to maintain once properly implemented.

Hope this will help you.

Srijit

where does this pigging process normally used in oil, water. in which type of pipe ss , ms. what are the advantages against the steaming

is it that much strong to break the solidification of soap or oil

Pigging can be used to move/push liquid produts in the pieline to mother tank. It can be used for palmolein, palm fatty acid, white oils or any other LIQUID PRODUCTS. You cannot do pigging once the product gets solidified. Pigging need to be done immediately after pumping.

Mr.Sandeep

To be correct pigging to be done immediately after pumping for products like Palm Fatty Acid, LSHS, etc as these products solidifies at or above ambient temperature. For rest of the normal liquid products pigging can be done at any time.

Initially I have asked you the product specification for analysing this, which you had not replied. I assume that you pump the soap solution at higher temperature and after pumping the left product solidifies and later make further pumping difficult. To melt this solidified product you pass steam and clear the line. If this is your problem, my question is immediately after pumping can you not remove the product in the pipeline before it solidifies by means of pigging process? You need to analyse this depending on your frequency of operation too.

Regards

Srijit

what is the advantage of pigging process against the steaming.

Dear Mr. Sandeep

I do not know what process you have adopted, but steaming to my knowledge will increase moisture content in the product or even results in presence of water at the vessel bottom. Even I feel you can have pumping problems especially with centrifugal pumps due to air entrapped in the product. Again I cannot confirm, whether prolonged pumping can result in cavitation. Hope some GURU will react to this.

Steaming is costlier for its generation, maintenance, transfer and handling. To add, you need your entire infrastructure with high temperature materials. I time and again remind you to get your entire process reviewed by an expert which will be the economical solution.

Let me continue...

Certain liquids when solidifies require prolonged passing of steam as it need to pierce the solid mass and then to melt it completely.

Certain products or chemicals cannot afford to have even moisture traces where steaming is ruled out.

Also Petroleum products with low flash points / white oils like Motor Spirit, Benzene, cannot be steamed due to Safety reason.

Pigging is advisable in the above situations.

I hope to have reasonably answered your query.

Many thanks

Srijit