# Tape And Dope



## Mike01 (Oct 11, 2016)

All,
I have a question regarding the use of Teflon Tape and Pipe Dope together. I have been in the Navy for 15 years and I am now currently a gas turbine engineer. I have worked on many fuel systems and never seen this and I am wanting to know if this is good, bad or makes know difference. I have looked into this from every aspect and can not get a strait answer on it. I looked into,

NPTF Manual Says - NPTF threads are designed so that when the threads are mated, they actually deform to creat a mechanical seal. Since the seal is created by the threads themselves a thread seal agent is not required (though may be used as a lubricant).

Straight Threads For Fuel - When working with fittings with straight threads, paste dope should ALWAYS be used. Tape dope is too thick, and can actually prevent a good seal in straight threads joints. 

Also wouldn't a product company say on there product for best results use both. I just can't get a straight answer on this and all I get is that this is how I was trained or I have been doing this for years. With all that does not mean it is the right way. Because if you sit there and put all this on is it masking the actual problem e.g bad threads. So I am looking for paper work, data or something on this because the equipment I work on is very very expensive and if there is a better way of doing something then I am all about it plus I am always looking to further my knowledge.
Thanks,


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## Gargalaxy (Aug 14, 2013)

I use one step brand.


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## GAN (Jul 10, 2012)

Two steps are better as long as you get the UV resistant purple brand........


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## ShtRnsdownhill (Jan 13, 2016)

and your not gona get a straight answer here either..


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## Debo22 (Feb 15, 2015)

Thank you for serving


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## Mike01 (Oct 11, 2016)

Yeah I am thinking this is going to be a difficult one to get a solution on.
Debo22 - Thank you for your support...


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## GAN (Jul 10, 2012)

Mike01 said:


> Yeah I am thinking this is going to be a difficult one to get a solution on.
> Debo22 - Thank you for your support...


I'll be respectful since your a Veteran. The site is for "Plumbing Professionals" only. Home owners, salesmen or other Non-plumbers often get raked through the coals.


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## ShtRnsdownhill (Jan 13, 2016)

Mike01 said:


> All,
> I have a question regarding the use of Teflon Tape and Pipe Dope together. I have been in the Navy for 15 years and I am now currently a gas turbine engineer. I have worked on many fuel systems and never seen this and I am wanting to know if this is good, bad or makes know difference. I have looked into this from every aspect and can not get a strait answer on it. I looked into,
> 
> NPTF Manual Says - NPTF threads are designed so that when the threads are mated, they actually deform to creat a mechanical seal. Since the seal is created by the threads themselves a thread seal agent is not required (though may be used as a lubricant).
> ...


ill give you a freebee for serving......why dont you call the equipment manufacture and ask their recommendation on what to use...


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## ace4548 (Feb 10, 2015)

I don't know what kind of equipment you are working on. Before becoming a plumbing apprentice for the past 2 years. I spent 9 years repairing military vehicles. A lot of fittings for hydraulic lines were nptf. We used a special kind of thread sealant . Locktite 545 I believe. But as stated above, I would call manufacturer , and ask what they advise.


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## Mike01 (Oct 11, 2016)

This is for a fuel system for a new hospital I was called to come in and take a look at see why there were so many leaks in the new fuel piping. Due to my background in designing and installing fuel systems, reverse osmosis systems and open and closed loop water systems. I have never seen this type of set up by using both pipe dope and Teflon tape on a NPTF system. When i approached the plumber he said that he done this for many years and was trained that way from the union. But in no standard does it say it is authorized to use both and when you are on a federal job at a children's hospital and the diesel generator has to be shut down because leaks start occurring all over the place. So they send some one like me as a 3rd party to find out why this happen. So instead of raking this plumber over the coals i look at every possible way to come to a conclusion and i decided to turn to his brothers and find out why this practice is occurring. When in the NPTF manual it clearly says to not do that and even on the manufacturing bottle of pipe dope or Teflon tape it does not say to use both for a better outcome. As for ShtRnsdownhill I have called many manufacturing companies and even UL's main office and all say the same thing that plumbers should follow the instructions on the bottle. That all products go through vigorous testing phase and the product will do as listed on the bottle. As for me being a plumbing professional, I am...
I have plenty of certifications in plumbing and have designed and built many systems. But I am always interested in learning new ways of doing things and also why some one would veer off of a standard on a job like this with no documentation.


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## Mike01 (Oct 11, 2016)

ace4548 said:


> I don't know what kind of equipment you are working on. Before becoming a plumbing apprentice for the past 2 years. I spent 9 years repairing military vehicles. A lot of fittings for hydraulic lines were nptf. We used a special kind of thread sealant . Locktite 545 I believe. But as stated above, I would call manufacturer , and ask what they advise.


Yeah I worked on those type of fittings to and I believe that is what we used. But this is for type 2 diesel fuel, 2" black pipe... NPTF for black pipe is pipe dope and i only use it as a thread lubricant because if the threads are correct it is supposed to make a mechanical seal. Thanks for the suggestion...


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## ace4548 (Feb 10, 2015)

I would never use Teflon on a fuel line. Most of our fuel lines, we did not use anything. The fittings were designed this way.. Just tighten to the proper torque. How big of pipe were you running? We had hydraulic lines like this as well that went up to 2.5"... Anything bigger we used flanged fittings typically.. Without seeing your fittings, and how it was engineered o specd, I can't say what you should do. I would say Teflon tape and dope would not be something I would do, and goes against what I was trained.


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## wyrickmech (Mar 16, 2013)

Mike01 said:


> This is for a fuel system for a new hospital I was called to come in and take a look at see why there were so many leaks in the new fuel piping. Due to my background in designing and installing fuel systems, reverse osmosis systems and open and closed loop water systems. I have never seen this type of set up by using both pipe dope and Teflon tape on a NPTF system. When i approached the plumber he said that he done this for many years and was trained that way from the union. But in no standard does it say it is authorized to use both and when you are on a federal job at a children's hospital and the diesel generator has to be shut down because leaks start occurring all over the place. So they send some one like me as a 3rd party to find out why this happen. So instead of raking this plumber over the coals i look at every possible way to come to a conclusion and i decided to turn to his brothers and find out why this practice is occurring. When in the NPTF manual it clearly says to not do that and even on the manufacturing bottle of pipe dope or Teflon tape it does not say to use both for a better outcome. As for ShtRnsdownhill I have called many manufacturing companies and even UL's main office and all say the same thing that plumbers should follow the instructions on the bottle. That all products go through vigorous testing phase and the product will do as listed on the bottle. As for me being a plumbing professional, I am...
> I have plenty of certifications in plumbing and have designed and built many systems. But I am always interested in learning new ways of doing things and also why some one would veer off of a standard on a job like this with no documentation.


Has less to do with the Teflon tape and dope and a lot more with the install. You are right in the theory that it is a mechanical seal but Teflon helps in the assistance to get that seal. Without extremely clean thread's you will not be able to tighten the joint tight enough before it will gauld. The use of Teflon tape and past is a good practice and aids in the tightening of the joint. Leaks are from joints not tight enough or threads that are to deep from someone that is not setting the threader up right.


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## Mike01 (Oct 11, 2016)

ACE4548 - Yes you don't use Teflon tape on hydraulic systems because the tape can get into the hydraulic system and cause issues. Also on the hydraulic system once you pass 2.5" you should flange due to pressure. 
The system I am inspecting is a 2" black pipe NFPT machined tapered threads and only pushing about 25 psi. When I throw black pipe down on a fuel system I use pipe dope for fuel systems and make sure i get the threads lubricated enough to get the threads in good so i get that good mechanical seal and allow the dope to set for 24hrs before sending fuel down the line. But the question i have is the use of both tape and dope on a NFPT fitting. I have never seen that and nor was i trained to use both. I don't use Teflon tape on a fuel system for one it can allow the Teflon to get in the fuel system and clog inline filters, injectors, fuel nozzles and things of that nature.


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## Mike01 (Oct 11, 2016)

Wyrickmech - I see where you are coming from on the tape and the dope. But as I look into the NFPT manual it states the following-
NPTF - Pipe threads are designed so that when the threads are mated, they form a mechanical seal and a sealant agent is not required but can be used as a lubricant only.
also when when speaking about straight threads it says not to use tape do to the tape being to thick and can cause the mechanical seal from occurring.


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## ShtRnsdownhill (Jan 13, 2016)

Mike01 said:


> This is for a fuel system for a new hospital I was called to come in and take a look at see why there were so many leaks in the new fuel piping. Due to my background in designing and installing fuel systems, reverse osmosis systems and open and closed loop water systems. I have never seen this type of set up by using both pipe dope and Teflon tape on a NPTF system. When i approached the plumber he said that he done this for many years and was trained that way from the union. But in no standard does it say it is authorized to use both and when you are on a federal job at a children's hospital and the diesel generator has to be shut down because leaks start occurring all over the place. So they send some one like me as a 3rd party to find out why this happen. So instead of raking this plumber over the coals i look at every possible way to come to a conclusion and i decided to turn to his brothers and find out why this practice is occurring. When in the NPTF manual it clearly says to not do that and even on the manufacturing bottle of pipe dope or Teflon tape it does not say to use both for a better outcome. As for ShtRnsdownhill I have called many manufacturing companies and even UL's main office and all say the same thing that plumbers should follow the instructions on the bottle. That all products go through vigorous testing phase and the product will do as listed on the bottle. As for me being a plumbing professional, I am...
> I have plenty of certifications in plumbing and have designed and built many systems. But I am always interested in learning new ways of doing things and also why some one would veer off of a standard on a job like this with no documentation.


ok then ask the plumber what brand tape and what brand pipe dope he is using and call the makers and ask them, could be defective batch from the factory, I have used both together and rarely have a leak or one develop, so something is wrong somewhere..


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## ShtRnsdownhill (Jan 13, 2016)

Mike01 said:


> Wyrickmech - I see where you are coming from on the tape and the dope. But as I look into the NFPT manual it states the following-
> NPTF - Pipe threads are designed so that when the threads are mated, they form a mechanical seal and a sealant agent is not required but can be used as a lubricant only.
> also when when speaking about straight threads it says not to use tape do to the tape being to thick and can cause the mechanical seal from occurring.


in theory that may be correct, but in reality it will never happen..in a high tech factory with precise threading machines yeah, out in the field threading pipe..not a chance..


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## Plumbus (Aug 4, 2008)

Mike
Here's a pretty clear definition of the difference between NFPT and NPT threads. It digs a little deeper into the differences between the two.
http://www.cutting-tool-supply.com/TechTips/Tapping/NPTvsNPTF/NPTVsNPTF.htm

As for testing:
http://www.ring-plug-thread-gages.com/ti-NPT-vs-NPTF.htm


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## Mike01 (Oct 11, 2016)

ShtRnsdownhill- Thank you for your input... But it falls upon the plumber to inspect those threads and to make sure that he meets the standard. So if NFPT says not to use it then you don't because if something happens they are going to fall back and say show me where it says you can use both and when you are talking about federal buildings they will send inspectors and mechanical inspectors to find out what happen. So as a master plumber of your craft, do you follow the standard or do you follow other plumbers that say this is what i have been doing and have no documentation to follow it up and place everything on the line for it.Because remember this is a government building and they will find any way to throw some one under the bus. So if a product says this will seal and it doesn't then they are not going to be in business for long now would they. So now how i was trained was to inspect your threads and then add only pipe dope on black pipe fuel systems because for 1 you don't want Teflon tape because pieces of tape have been known to come off and clog systems and 2nd Teflon tape is to thick and can cause issues with the mechanical seal.Then after you finish you let it sit for 24hrs to allow the dope to cure and then you pressurize your system with air and let it sit and then check for leaks because there is nothing like having a leak either underground and your veederoot system going off do to a detection of a leak under ground or in a overhead of say a hospital. I rather do it once and take the extra time then go back and look like a ass because my stuff is leaking and fork over $.


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## ShtRnsdownhill (Jan 13, 2016)

If I was working on a job such as a federal project and they had absolute specs, I would follow them..so what are the specs for that plumber and was he given them for this job? if he didnt follow the specs( hopefully the specs follow the manufactures recommendations for use of their product)then he is liable for the leaks, and either way he is liable for the leaks unless its a defect in the product, and then the manufacture would be liable, could be his threading dies are crap and all the threads are chewed up..not seeing or talking with the plumber and only getting one side and not knowing what your agenda is( are you the govmnt lynch man out to hang this guy) its hard to give you a direct answer on this issue..and if you have all this knowledge and design systems you should be able to answer your own question or find the correct people( manufactures or who put the specs together for this job) to ask these questions..I would say if your building the space shuttle then specs should be followed to the T..but installing oil fuel line is not rocket science and shouldnt be that difficult..why so many leaks..well without having the plumber to ask I cant tell you, I have installed plenty of fuel oil lines with out leaks..one cannot comment on anothers work without seeing it...
and by the way who called you in? to get involved with the project?


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## moonapprentice (Aug 23, 2012)

Nuff said^^^


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## Mike01 (Oct 11, 2016)

Plumbus - Thank you... I have that information. But again it says the same thing, NPT threads will require A sealant not sealants and NPTF threads class 1 requires a sealant and a class 2 does not require no sealant due to a mechanical seal. but you can use a small amount of dope as a thread lubricant only. Now also if you dig deeper it states that NPTF thread that is creating a mechanical seal that tape is to thick and could cause the mechanical seal to fail.


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## ShtRnsdownhill (Jan 13, 2016)

Mike01 said:


> Plumbus - Thank you... I have that information. But again it says the same thing, NPT threads will require A sealant not sealants and NPTF threads class 1 requires a sealant and a class 2 does not require no sealant due to a mechanical seal. but you can use a small amount of dope as a thread lubricant only. Now also if you dig deeper it states that NPTF thread that is creating a mechanical seal that tape is to thick and could cause the mechanical seal to fail.


see this is your problem, you are not a plumber and dont know what plumbers do in the field, and do not know plumbing work..how much fuel line have you personally installed?


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## Mike01 (Oct 11, 2016)

ShtRndsdownhill - very valid point and no i am not a government lynch to take out the small time plumber. i am called in as a 3rd party to inspect the work from a major failure. Now as to your comment about a space ship and following it to the T, So you are telling me when it comes to a hospital you don't follow it to a T and even more so a children's hospital. But even then I expect my guys to follow every job to the T and I don't expect them to cut corners. So as for your analogy you are saying you don't follow specs to the T and basically you are saying you cut corners. Great Job... But as for the plumber I try to find out why this has happen and to prevent this from happening again. Then I spoke to the hospital and was able to close this peacefully with every one happy. But I was curious and was looking for answers to push my knowledge a little bit more by learning from the people that have been doing this for years and see why they do this and if it is good practice or not. I can go off of owe because some guy told me to do it. that does not work... But maybe put a study together and see if it does work better and put it into documentation. That's all thanks for your time..


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## wyrickmech (Mar 16, 2013)

Mike01 said:


> Wyrickmech - I see where you are coming from on the tape and the dope. But as I look into the NFPT manual it states the following-
> NPTF - Pipe threads are designed so that when the threads are mated, they form a mechanical seal and a sealant agent is not required but can be used as a lubricant only.
> also when when speaking about straight threads it says not to use tape do to the tape being to thick and can cause the mechanical seal from occurring.


Like others have said in theory not real time. You always use thread sealants. In Europe they use horse hair on straight threads. In npt fittings and pipe there is no straight threads. Common practices on 2 inch and down is tape then dope. We only flange equipment above 2 in everything else is welded. Hydraulics and a low pressure fuel lines are not even in the same section in any speck book I have ever read. You might want to read the speck book for that job.


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## rwh (Dec 17, 2014)

Lubricant helps make the joint. Does not seal it. If you are letting screw joints "cure" for 24 hours, you are in need of some mentoring.


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## ShtRnsdownhill (Jan 13, 2016)

Mike01 said:


> ShtRndsdownhill - very valid point and no i am not a government lynch to take out the small time plumber. i am called in as a 3rd party to inspect the work from a major failure. Now as to your comment about a space ship and following it to the T, So you are telling me when it comes to a hospital you don't follow it to a T and even more so a children's hospital. But even then I expect my guys to follow every job to the T and I don't expect them to cut corners. So as for your analogy you are saying you don't follow specs to the T and basically you are saying you cut corners. Great Job... But as for the plumber I try to find out why this has happen and to prevent this from happening again. Then I spoke to the hospital and was able to close this peacefully with every one happy. But I was curious and was looking for answers to push my knowledge a little bit more by learning from the people that have been doing this for years and see why they do this and if it is good practice or not. I can go off of owe because some guy told me to do it. that does not work... But maybe put a study together and see if it does work better and put it into documentation. That's all thanks for your time..


dont take this personally, but you sound more of the engineer/design area than a hands on person( correct me if im wrong), and all you know is what you read that some other engineer/designer wrote( and we all know you guys never make mistakes) ( SARCASM), by never working in the field you dont know real life installations, you would be surprised what goes off spec to make things work, as said earlier if there was exact spec to install, but earlier you stated the equipment manufacture said let the plumber follow the directions on the can..??? so what does the job spec to use??? if left up to the plumber , we do what works, now I dont know what the issue with the leaks are until I can get a look at the work personally and cant go by what someone says happened, so in conclusion now that you stated you made all parties happy was the problem causing the leaks?


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## GAN (Jul 10, 2012)

Cut through the crude.

Architects, engineers of all sorts spec out the drawings.

Follow, drawing specs, follow manufactures approved installation instructions.

If the contractor does not and something happens, his fault. If contractor follows equipment specs & installation instructions, they are safe and fault goes to designers.

As ****runs stated if not specified, it is left up to the contractor. This said the contractor to be safe should always follow manufactures installation instructions on any "critical job" and used "approved materials" for the system they are working with or be ready to pay the piper. One product would not have to be utilized, but a mix of products on any one point better be able to back it up with installation instructions or they would be at fault.

http://https://www.permatex.com/pro...d-sealants/permatex-thread-sealant-with-ptfe/

http://http://www.nationalpetroleum.net/id47.html


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## ShtRnsdownhill (Jan 13, 2016)

links no worky....


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## GAN (Jul 10, 2012)

ShtRnsdownhill said:


> links no worky....



Hmmmm

That was weird. When I use the site tool to link it comes up invalid. When I just paste and copy it comes up.

https://www.permatex.com/products/t...d-sealants/permatex-thread-sealant-with-ptfe/ 


https://www.astm.org/Standards/petroleum-standards.html


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## ShtRnsdownhill (Jan 13, 2016)

now they worky.....


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## wyrickmech (Mar 16, 2013)

The other thing that may have went over your head is die setup. Very critical to a proper seal .thread sealants or tape are dependant on thread depths. National pipe thread standards are set for correct set die standard's.


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