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  1. #1
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    Stainless steel valves observation



    Been meaning to post this for quite some time, but never got around to it.

    First noticed the phenomenon maybe 10 years ago when stainless steel valves started dropping in price.

    As long as the system is under pressure, everything is fine.
    during depressurizing and pulling vacuum, everything is fine.
    When charged with ammonia, the valves start leaking between the housing and insert.

    After the first few times, I made it a habit to check/tighten the bolts on all stainless valves while the system was under full vacuum, and it's not uncommon to be able to tighten the bolts 2-3 full turns.

    Now stainless steel has a lower tensile strength than carbon steel, and I am guessing that it is a combination of the valves being alternated between warm and cold, stretching the bolts, and maybe the gasket getting squashed while pulling vacuum.

    Now, knowing that stainless steel bolts doesn't have the same tensile strength as carbon steel, I'm wondering if we will be looking at valve inserts popping out after 10-20 years when the bolts have been tightened again and again

    Anyone else observed this?


    -Cheers-

    Tycho

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    Re: Stainless steel valves observation

    Tycho,
    We don’t use hardly any stainless steel valves, but bolts yes.
    Assuming we are talking Danfoss, standard valves have had stainless bolts for quite awhile.
    Danfoss say to tighten to “X” torque, we are dumb & tighten using our best judgment on the day.
    Mee usually alway use anti- seize on bolts as well.
    Have not heard of any issues at all.
    Since Danfoss went back to gasket seals from “0” rings, if not tight enough, maybe some gasket relaxation?
    Stainless valves may be more prone to expansion & contraction, don’t know.
    Why not report to supplier as serious safety issue if it concerns you (maybe that’s why you are confirming your observations).

    https://www.assda.asn.au/blog/221-st...less-fasteners

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    Re: Stainless steel valves observation

    Quote Originally Posted by RANGER1 View Post
    Tycho,
    We don’t use hardly any stainless steel valves, but bolts yes.
    Assuming we are talking Danfoss, standard valves have had stainless bolts for quite awhile.
    Danfoss say to tighten to “X” torque, we are dumb & tighten using our best judgment on the day.
    Mee usually alway use anti- seize on bolts as well.
    Have not heard of any issues at all.
    Since Danfoss went back to gasket seals from “0” rings, if not tight enough, maybe some gasket relaxation?
    Stainless valves may be more prone to expansion & contraction, don’t know.
    Why not report to supplier as serious safety issue if it concerns you (maybe that’s why you are confirming your observations).

    https://www.assda.asn.au/blog/221-st...less-fasteners
    Ranger, I first started noticing this back 10-15 years ago when grasso/herl stainless valves came on the market...

    On the first plant we used them, I noticed that after being vacuumed they would leak when you put pressure back in.... as in the vacuum would pull the insert down and squash the gasket... but funny thing is that this wouldn't happen with black steel valves or valves with black steel bolts.



    I thought it was the gasket shrinking after being vacuumed

    so I tightened the bolts and let it go...

    Then I came back to the same plant again and had to empty the system, and I figured "I'll check all the bolts" so I checked a system where they had the GEA/herl straightway DN80 valve,

    So on a plant with black steel valves and black steel bolts, I didn't have to check anything.

    while supervising on plants with danfoss valves, I have personally installed all inserts, stainless or carbon steel, I have personally inserted all inserts and tightened all bolts to the proper torque....
    And my observation is that even if the bolts on the inserts have been tightened to the proper torque initially it is that after some time the stainless bolts loosen up because the stainless steel bolts doesn't have the same tensile strength as the carbon steel bolts

    My question is if any of you have noticed this?

    Am I the only one?
    -Cheers-

    Tycho

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    Re: Stainless steel valves observation

    Tycho,
    I will ask at work as personally not heard of it.
    Danfoss are designed for very high pressures, so thought tensile strength on ammonia plant would low compared to its rating.
    Obviously gaskets shrink to a certain degree,
    but interesting observation.

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    Re: Stainless steel valves observation

    Not Tycho, you're not the only one who noticed.
    Stainless material has great expansiveness - unfortunately, it is a tax for stainless steel.
    I recommend that you change the screws over time, so that the screw not can bite in the valve body and damage the threads.
    Experts recommend a stainless steel valve and mount a steel bolt, but it loses ground for a stainless steel valve point.

    Josef.

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    Re: Stainless steel valves observation

    Do you have any issues with Danfoss stainless bolts or valves if you use them. As Josef says try something else, even if a test to prove, then go back to manufacturer.
    It might take an accident before something happens.
    While your at it have Herl replaced their concrete gland packing for “0” ring glands yet.
    Go for Danfoss, at least they improve things generally if problems.
    I wonder when Parker took over in 2005 it started to occur?
    Serms a coincidence, or am I sceptical��

    https://www.crunchbase.com/organizat...-locked-charts
    Last edited by RANGER1; 22-06-2019 at 08:21 PM.

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    Re: Stainless steel valves observation

    In Norway, stainless steel bolts have been on the market for a long time, but not steadily used on carbon steel inserts. the first valves I noticed it on were grasso valves maybe 20-15 years ago... these were isolating valves on the suction side of the evaportrator...
    First time I had to seal with stainless steel body and insert...
    Pressure out, then vacuumed, then ammonia introduced, and all the valves leaked between the housing and insert....

    Now on all the plants I supervise, I let the apprentices insert inserts, but I check every single one of them... "Every single one, personally. so when a ship comes back 3 months later and says no leak, that's good
    -Cheers-

    Tycho

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    Re: Stainless steel valves observation

    I'm not here to find faults in a product, I was just asking if any of you had seen the same to make sure that I wasn't seeng sights
    -Cheers-

    Tycho

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    Re: Stainless steel valves observation

    Quote Originally Posted by RANGER1 View Post
    Do you have any issues with Danfoss stainless bolts or valves if you use them. As Josef says try something else, even if a test to prove, then go back to manufacturer.
    It might take an accident before something happens.
    While your at it have Herl replaced their concrete gland packing for “0” ring glands yet.
    Go for Danfoss, at least they improve things generally if problems.
    I wonder when Parker took over in 2005 it started to occur?
    Serms a coincidence, or am I sceptical��

    https://www.crunchbase.com/organizat...-locked-charts
    also, it's not about danfoss "stainless" it's about stainless in general...

    black steel has a more, how to say it, rubbery consistency... black steel can expand and then return to their previous state...

    if you over torque a carbon steel bolt, it will expand, and then when you loosen it up, it will somewhat return to it's previous state

    The higher the carbon content in steel, the higher flexibility.

    Stainless steel, has much less carbon, so it will stretch if you over torque... but since it has less carbon, it will not return to it's previous state, it just stretches, then it stays there.


    Like Ranger1 mentioned earlier, we have a tendency to just tighten until it "feels right" so we may be under torquing or over torquing

    but no matter how we torque it, for some reason, after releasing pressure, and then pulling vacuum, most stainless bolts are in need of 2-3 turns of tightening...
    -Cheers-

    Tycho

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    Re: Stainless steel valves observation

    Tycho,
    Sorry can’t offer any advice.
    There is only seems to be a handful of people to comment unfortunately.

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    Re: Stainless steel valves observation

    Tyco is right.
    I have had various valve bodies of differing designs, which over 5 or six years sometimes.
    have started to leak from their flange bodies.
    Especially if they as already described expand and contract during the course of their normal operation.
    Historically (for me at least.) these have almost entirely been on large Ammonia Plants.
    Usually a flange will start to emit small amounts of vapour (Smell).
    When that part of the plant has been isolated for a repair, resulting in the ice build up around the fitting (Or within its insulation jacket) to melt.
    Generally speaking the increase in the frequency of loosened flanges etc. had passed me by.

    But now you have highlighted it Tyco.
    You have got a point
    Grizzly
    Last edited by Grizzly; 29-06-2019 at 10:11 AM.
    Despite the High Cost of Living it still remains Popular!

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    Re: Stainless steel valves observation

    Interesting as Tycho, Josef & Grizzly have experienced it.
    In the chart I posted earlier it says 304 stainless has more tensile strength than high tensile steel in some cases.
    Tycho mainly mentions in pressure testing & vacuum they require re- tensioning.
    With Danfoss stainless bolts have found no issues ourselves with standard carbon steel valves under any circumstances.
    In article is also mentions very low grade stainless which could have some give, or is more malleable.
    A lot of things sourced from China in the past are questionable quality, if suppliers not checking quality when sourced which could be possible.
    We received 50% magnetic ones that rust on components, other 50% ok.
    If a bolt stretched like indicated manufacturer should be informed as a matter of urgency if you followed torque instructions as a duty of care.
    As far as expansion & contraction with full stainless valves, only makes sense to me if it has been through a number of temperature/ pressure cycles.
    Tycho,I think you have to try some high tensile bolts on a few, torque bolts on type supplied & new high tensile, mark bolt position with permanent marker & see results.
    Maybe not an issue now, only in the past???
    We weld mild steel valves to stainless pipe, no problem with correct Tig wire��
    Last edited by RANGER1; 29-06-2019 at 09:32 PM.

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    Re: Stainless steel valves observation

    Now I'm no expert on this subject but it seems that stainless steel can suffer problems, below is a text explaining some of them. Whether it helps or hinders I'm not sure...
    +
    How To Stop Thread Galling On Stainless Fasteners

    By fastener expert Joe Greenslade: www.greensladeandcompany.com


    A few times each year we receive calls from fastener suppliers who are in conflict with their customer over the quality of stainless steel bolts and nuts. The customer's complaint is that during installation the bolts are twisting off and/or the bolt's threads are seizing to the nut's thread. The frustration of the supplier is that all required inspections of the fasteners indicate they are acceptable, but the fact remains that they are not working.

    This problem is called "thread galling." According to the Industrial Fastener Institute's 6th Edition Standards Book (page B-28),

    Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium, and other alloys which self-generate an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.

    Carpenter Technologies, the fastener industry's largest supplier of stainless steel raw material, refers to this type of galling in their technical guide as "cold welding." Anyone who has seen a bolt and nut with this problem understands the graphic nature of this description.

    The IFI and Carpenter Technologies give three suggestions for dealing with the problem of thread galling in the use of stainless steel fasteners:

    1. Slowing down the installation RPM speed will frequently reduce, or sometimes solve completely, the problem. As the installation RPM increases, the heat generated during tightening increases. As the heat increases, so does the tendency for the occurrence of thread galling.
    2. Lubricating the internal and/or external threads frequently eliminates thread galling. The suggested lubricants should contain substantial amounts of molybdenum disulfide (moly), graphite, mica, or talc. Some proprietary, extreme pressure waxes may also be effective. You must be aware of the end use of the fasteners before settling on a lubricant. Stainless steel is frequently used in food related applications, which may make some lubricants unacceptable. Lubricants can be applied at the point of assembly or pre-applied as a batch process similar to plating. Several chemical companies offer anti-galling lubricants. One such source, EM Corporation, suggests their Permaslik¨ RAC product for use at the point of assembly. They suggest Everlube¨ 620C for batch, pre-applying to stainless steel fasteners.
    3. Using different stainless alloy grades for the bolt and the nut reduces galling. The key here is the mating of materials having different hardnesses. If one of the components is 316 and the other is 304 they're less likely to gall than if they're both of the same alloy grade. This is because different alloys work-harden at different rates.
    Another factor affecting thread galling in stainless steel fastener applications is thread roughness. The rougher the thread flanks, the greater the likelihood galling will occur. In an application where the bolt is galling with the internal thread, the bolt is usually presumed to be at fault, because it is the breaking component. Generally, it is the internal thread that is causing the problem instead of the bolt. This is because most bolt threads are smoother than most nut threads. Bolt threads are generally rolled, therefore, their thread flanks are relatively smooth. Internal threads are always cut, producing rougher thread flanks than those of the bolts they are mating with. The reason galling problems are inconsistent is probably due largely to the inconsistencies in the tapping operation. Rougher than normal internal threads may be the result of the use of dull taps or the tapping may have been done at an inappropriately high RPM.

    Fortunately, stainless steel bolt and nut galling problems do not occur everyday, but when they do it usually creates a customer crisis. Knowledge of why this occurs and how to remedy it can save the supplier much grief and many headaches.

    Below are the questions that should be asked and the suggestions that should be made immediately when you are confronted with a customer's complaint about thread galling:

    Questions:
    Suggestions:

    1. Are you using the same driver RPM you have used in the past to install these stainless fasteners?
    If they say they are driving them faster than in the past or if they say this is a new application, suggest they immediately try slowing the driver RPM and see if the problem goes away. In general, a stainless bolt of a given size should be driven slower than a steel bolt of the same size.

    2. Are the bolts and/or internal threads lubricated?
    If they say, "no", suggest they try lubricating the bolts and/or internal threads with one of the lubricants listed above. If this eliminates the galling, you might want to batch lubricate the remainder of the order to eliminate the extra work of applying lubricant at the point of assembly.

    In applications where galling is a repetitive problem, it is advisable to supply the fasteners with pre-applied lubrication to eliminate future problems

    3. Are you using the same grade of stainless steel for the bolts and nuts?
    If the answer is, "yes", you can suggest changing one or the other to a different grade.

    Be sure the suggested grade meets their corrosion needs and changing the material does not cause a procurement problem.

    When thread galling occurs in stainless steel bolt and nut applications, don't panic. Try the suggestions listed above. One, or a combination of these, will probably resolve the problem immediately.
    Stainless Steel Information
    +
    Brian - Newton Abbot, Devon, UK
    Retired March 2015
    Please support http://the100project.net/Home

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    Re: Stainless steel valves observation

    Quote Originally Posted by Brian_UK View Post
    Now I'm no expert on this subject but it seems that stainless steel can suffer problems, below is a text explaining some of them. Whether it helps or hinders I'm not sure...
    +
    How To Stop Thread Galling On Stainless Fasteners

    By fastener expert Joe Greenslade: www.greensladeandcompany.com


    A few times each year we receive calls from fastener suppliers who are in conflict with their customer over the quality of stainless steel bolts and nuts. The customer's complaint is that during installation the bolts are twisting off and/or the bolt's threads are seizing to the nut's thread. The frustration of the supplier is that all required inspections of the fasteners indicate they are acceptable, but the fact remains that they are not working.

    This problem is called "thread galling." According to the Industrial Fastener Institute's 6th Edition Standards Book (page B-28),

    Thread galling seems to be the most prevalent with fasteners made of stainless steel, aluminum, titanium, and other alloys which self-generate an oxide surface film for corrosion protection. During fastener tightening, as pressure builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped off, and interface metal high points shear or lock together. This cumulative clogging-shearing-locking action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.

    Carpenter Technologies, the fastener industry's largest supplier of stainless steel raw material, refers to this type of galling in their technical guide as "cold welding." Anyone who has seen a bolt and nut with this problem understands the graphic nature of this description.

    The IFI and Carpenter Technologies give three suggestions for dealing with the problem of thread galling in the use of stainless steel fasteners:

    1. Slowing down the installation RPM speed will frequently reduce, or sometimes solve completely, the problem. As the installation RPM increases, the heat generated during tightening increases. As the heat increases, so does the tendency for the occurrence of thread galling.
    2. Lubricating the internal and/or external threads frequently eliminates thread galling. The suggested lubricants should contain substantial amounts of molybdenum disulfide (moly), graphite, mica, or talc. Some proprietary, extreme pressure waxes may also be effective. You must be aware of the end use of the fasteners before settling on a lubricant. Stainless steel is frequently used in food related applications, which may make some lubricants unacceptable. Lubricants can be applied at the point of assembly or pre-applied as a batch process similar to plating. Several chemical companies offer anti-galling lubricants. One such source, EM Corporation, suggests their Permaslik¨ RAC product for use at the point of assembly. They suggest Everlube¨ 620C for batch, pre-applying to stainless steel fasteners.
    3. Using different stainless alloy grades for the bolt and the nut reduces galling. The key here is the mating of materials having different hardnesses. If one of the components is 316 and the other is 304 they're less likely to gall than if they're both of the same alloy grade. This is because different alloys work-harden at different rates.
    Another factor affecting thread galling in stainless steel fastener applications is thread roughness. The rougher the thread flanks, the greater the likelihood galling will occur. In an application where the bolt is galling with the internal thread, the bolt is usually presumed to be at fault, because it is the breaking component. Generally, it is the internal thread that is causing the problem instead of the bolt. This is because most bolt threads are smoother than most nut threads. Bolt threads are generally rolled, therefore, their thread flanks are relatively smooth. Internal threads are always cut, producing rougher thread flanks than those of the bolts they are mating with. The reason galling problems are inconsistent is probably due largely to the inconsistencies in the tapping operation. Rougher than normal internal threads may be the result of the use of dull taps or the tapping may have been done at an inappropriately high RPM.

    Fortunately, stainless steel bolt and nut galling problems do not occur everyday, but when they do it usually creates a customer crisis. Knowledge of why this occurs and how to remedy it can save the supplier much grief and many headaches.

    Below are the questions that should be asked and the suggestions that should be made immediately when you are confronted with a customer's complaint about thread galling:

    Questions:
    Suggestions:

    1. Are you using the same driver RPM you have used in the past to install these stainless fasteners?
    If they say they are driving them faster than in the past or if they say this is a new application, suggest they immediately try slowing the driver RPM and see if the problem goes away. In general, a stainless bolt of a given size should be driven slower than a steel bolt of the same size.

    2. Are the bolts and/or internal threads lubricated?
    If they say, "no", suggest they try lubricating the bolts and/or internal threads with one of the lubricants listed above. If this eliminates the galling, you might want to batch lubricate the remainder of the order to eliminate the extra work of applying lubricant at the point of assembly.

    In applications where galling is a repetitive problem, it is advisable to supply the fasteners with pre-applied lubrication to eliminate future problems

    3. Are you using the same grade of stainless steel for the bolts and nuts?
    If the answer is, "yes", you can suggest changing one or the other to a different grade.

    Be sure the suggested grade meets their corrosion needs and changing the material does not cause a procurement problem.

    When thread galling occurs in stainless steel bolt and nut applications, don't panic. Try the suggestions listed above. One, or a combination of these, will probably resolve the problem immediately.
    Stainless Steel Information
    +
    Brian,
    Your above is definitely relevant & stainless is a dog if you don’t use anti-seize.
    After you seize the first number of nuts & bolts you never forget.
    Do them up nice tight, that’s it, no tighter & no looser, have to cut them off.

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