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What is 'Bubble Tight Shutoff' ?

What is 'Bubble Tight Shutoff' ?

What is 'Bubble Tight Shutoff' ?

Gents, I have researched this subject on these forums and found some good reference ANSI FCI 70-2 (old B16.104) and API 598 forum. I'm still confused though.
I have a vendor who quoted me 'bubble tight shutoff' for several full bore ball valves. No mention even of FCI 70-2 (Classes I thru VI for control valves - some ball valve companies do) or even API 598 on his literature. I looked through all the specs and can't find a definition of the Bubble Tight Shutoff term. (I've 'googled' it to death.)
Can anybody relate the term to a 'spec/standard/test' at all ?


RE: What is 'Bubble Tight Shutoff' ?

Bubble tight means different things to different people, if your buying a valve from these guys specify the test you want to conform to there are several classifications that are used for valve tests as you have mentioned. Go back and have them confirm they conform to your requirements. That said my experience is bubble tight is synonomous with class V test level (but it wouldnt stand up in a court).

RE: What is 'Bubble Tight Shutoff' ?

The term "bubble tight seal" is very old.  My understanding is that it originated from a test where a valve was installed in an air system with an open end pointing up.  Some soap was poured into the open end and air was applied to the other side.  The valve passed if no bubbles formed in the soap.  I'm not sure if this is true or not, but it was the only explanation I ever heard that was at least plausible.


RE: What is 'Bubble Tight Shutoff' ?

     I would interpret the requirement depending on the valve function, i.e.:
          -     as Class VI (to FCI-70-2 and/or IEC 60534-4 standards)      for control valves;

          -     as compliant to Table 5 of API 598 standard      for on-off valves.   

     But, as monaco8774 correctly says, this is just an interpretation (based on particular experiences...) and the best thing should be having the requirement explained by the Specifier himself.  

     About similar issues, see also thread408-172347: Drip drip drip and thread408-150132: "Zero Leakage" conept and EN 1779 std... within this Forum (if you did not read them already).

Hope this helps,                 'NGL

RE: What is 'Bubble Tight Shutoff' ?

Thanks guys for the info and insight.
I checked the valve manufacturer's website and they directly state that many of their valve are available as per API 598, FCI 70-2.
I think I'm just dealing with a lazy salesman with limited technical knowledge of his product.
FYI, in my search of ball valve seat leakage info, I found another 'world' of specs out there developed by the "Manufacturers Standardisation Society".
They produce an MSS SP (Standard Practice) range for almost everything. (I came across MSS SP-61 Pressure Testing of Steel Valves.)

Thank again to all for their input.

RE: What is 'Bubble Tight Shutoff' ?

Several MSS specifications may be applicable.  A list follows:

SP-6-2001    Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings

SP-9-2001    Spot Facing for Bronze, Iron and Steel Flanges

SP-25-1998     Standard Marking System for Valves, Fittings, Flanges and Unions

SP-42-2004    Class 150 Corrosion Resistant Gate, Globe, Angle and Check Valves with Flanged and Butt Weld Ends

SP-43-1991    Wrought Stainless Steel Butt-Welding Fittings
(R 2001)     

SP-44-1996    Steel Pipeline Flanges
(R 2001)     

SP-45-2003    Bypass and Drain Connections

SP-51-2003    Class 150LW Corrosion Resistant Cast Flanges and Flanged Fittings

SP-53-1999    Quality Standard for Steel Castings and Forgings for Valves, Flanges and Fittings and Other Piping Components - Magnetic Particle Exam Method
(R 2002)    

SP-54-1999    Quality Standard for Steel Castings for Valves, Flanges, and Fittings and Other Piping Components - Radiographic Examination Method
(R 2002)    

SP-55-2001    Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components - Visual Method for Evaluation of Surface Irregularities

SP-58-2002     Pipe Hangers and Supports - Materials, Design, and Manufacture

SP-60-2004    Connecting Flange Joint Between Tapping Sleeves and Tapping Valves

SP-61-2003    Pressure Testing of Steel Valves

SP-65-2004    High Pressure Chemical Industry Flanges and Threaded Stubs for Use with Lens Gaskets

SP-67-2002a    Butterfly Valves

SP-68-1997    High Pressure Butterfly Valves with Offset Design
(R 2004)     

SP-69-2003    ANSI/MSS Edition Pipe Hangers and Supports - Selection and Application

SP-70-1998     Cast Iron Gate Valves, Flanged and Threaded Ends

SP-71-1997     Gray Iron Swing Check Valves, Flanged and Threaded Ends

SP-72-1999    Ball Valves with Flanged or Butt-Welding Ends for General Service

SP-73-2003    Brazing Joints for Copper and Copper Alloy Pressure Fittings

SP-75-1998    Specification for High Test Wrought Butt Welding Fittings

SP-77-1995    Guidelines for Pipe Support Contractual Relationships
(R 2000)    

SP-78-1998      Cast Iron Plug Valves, Flanged and Threaded Ends

SP-79-2004    Socket-Welding Reducer Inserts

SP-80-2003     Bronze Gate, Globe, Angle and Check Valves

SP-81-2001    Stainless Steel, Bonnetless, Flanged Knife Gate Valves

SP-82-1992     Valve Pressure Testing Methods

SP-83-2001    Class 3000 Steel Pipe Unions, Socket Welding and Threaded

SP-85-2002    Cast Iron Globe & Angle Valves, Flanged and Threaded Ends

SP-86-2002    Guidelines for Metric Data in Standards for Valves, Flanges, Fittings and Actuators

SP-88-1993    Diaphragm Valves
(R 2001)     

SP-89-2003    Pipe Hangers and Supports - Fabrication and Installation Practices

SP-90-2000     Guidelines on Terminology for Pipe Hangers and Supports

SP-91-1992    Guidelines for Manual Operation of Valves
(R 1996)    

SP-92-1999     MSS Valve User Guide

SP-93-1999    Quality Standard for Steel Castings and Forgings for Valves, Flanges, and Fittings and Other Piping Components - Liquid Penetrant Exam Method
(R 2004)      

SP-94-1999    Quality Standard for Ferritic and Martensitic Steel Castings for Valves, Flanges, and Fittings and Other Piping Components - Ultrasonic Exam Method
(R 2004)    

SP-95-2000     Swage (d) Nipples and Bull Plugs

SP-96-2001    Guidelines on Terminology for Valves and Fittings

SP-97-2001    Integrally Reinforced Forged Branch Outlet Fittings - Socket Welding, Threaded and Buttwelding Ends

SP-98-2001    Protective Coatings for the Interior of Valves, Hydrants, and Fittings

SP-99-1994    Instrument Valves
(R 2001)     

SP-100-2002     Qualification Requirements for Elastomer Diaphragms for Nuclear Service Diaphragm Type Valves

SP-101-1989 (R 2001)     Part-Turn Valve Actuator Attachment - Flange and Driving Component Dimensions and Performance Characteristics

SP-102-1989 (R 2001)     Multi-Turn Valve Actuator Attachment - Flange and Driving Component Dimensions and Performance Characteristics

SP-103-1995 (R 2000)    Wrought Copper and Copper Alloy Insert Fittings for Polybutylene Systems

SP-104-2003    Wrought Copper Solder Joint Pressure Fittings

SP-105-1996 (2001)    Instrument Valves for Code Applications

SP-106-2003     Cast Copper Alloy Flanges and Flanged Fittings, Class 125, 150 and 300

SP-108-2002    Resilient-Seated Cast Iron-Eccentric Plug Valves

SP-109-1997    Welded Fabricated Copper Solder Joint Pressure Fittings

SP-110-1996    Ball Valves Threaded, Socket-Welding, Solder Joint, Grooved and Flared Ends

SP-111-2001    Gray-Iron and Ductile-Iron Tapping Sleeves

SP-112-1999 (R 2004) Quality Standard for Evaluation of Cast Surface Finishes - Visual and Tactile Method.

SP-113-2001    Connecting Joint between Tapping Machines and Tapping Valves

SP-114-2001    Corrosion Resistant Pipe Fittings Threaded and Socket Welding, Class 150 and 1000

SP-115-1999    Excess Flow Valves for Natural Gas Service

SP-116-2003    Service Line Valves and Fittings for Drinking Water Systems

SP-117-2002    Bellows Seals for Globe and Gate Valves

SP-118-2002    Compact Steel Globe & Check Valves - Flanged, Flangeless, Threaded & Welding Ends (Chemical & Petroleum Refinery Service)

SP-119-2003     Factory-Made Wrought Belled End Socket-Welding Fittings

SP-120-2002    Flexible Graphite Packing System for Rising Stem Steel Valves (Design Requirements)

SP-121-1997 (R 2002)    Qualification Testing Methods for Stem Packing for Rising Stem Steel Valves

SP-122-1997    Plastic Industrial Ball Valves

SP-123-1998    Non-Ferrous Threaded and Solder-Joint Unions for Use With Copper Water Tube

SP-124-2001    Fabricated Tapping Sleeves

SP-125-2000    Gray Iron and Ductile Iron In-Line, Spring-Loaded, Center-Guided Check Valves

SP-126-2000    Steel In-Line Spring-Assisted Center Guided Check Valves

SP-127-2001    Bracing for Piping Systems Seismic-Wind-Dynamic Design, Selection, Application

SP-129-2003    Copper-Nickel Socket-Welding Fittings and Unions

SP-130-2003    Bellows Seals for Instrument Valves
SP-131-2004    Metallic Manually Operated Gas Distribution Valves

SP-132-2004    Compression Packing Systems for Instrument Valves


RE: What is 'Bubble Tight Shutoff' ?

I have always crusaded against the term "Bubble tight shutoff".  
A leakrate is completely meaningless unless there is a standard by which it is tested.  

Many specifying engineers think that FCI 70.2 class VI is bubble tight, but there are specific numbers of bubbles allowed and there is a limited size range to which 70.2 Class VI applies. If an engineer specifies he wants class VI on a 10" valve...it's meaningless because 10" valves are not mentioned in that leak class.   

Another confusion is that the standards specify the test conditions, but users expect the valves to meet the same leakage rates installed at completely different pressures and temperatures, and on different fluids.  There is no predictable correlation.  

RE: What is 'Bubble Tight Shutoff' ?

     I completely agree with JimCasey.

     I only would like to add that "Leakage rate factors for Class VI" (see NOTE 2 to Table 3 of IEC 60534-4 and/or Table 2 of FCI-70-2) may be easily extrapolated also over the bigger size (DN 400 = ND 16") mentioned by the standards themselves, as it is clear that they are proportional to the square of the valve nominal diameter...    

     In general terms, extending the standards over their scopes and limitations is wrong and leads to contradictions or, at least, unpleasant messy situations... but unluckily it is a common practice among many Customers and Specifiers!!     ;-P

Bye to All,           'NGL

RE: What is 'Bubble Tight Shutoff' ?

Again gents, thanks to all for the insight and valuable help on this topic.

Best regards.

[two thumbs up]

RE: What is 'Bubble Tight Shutoff' ?

I thought that Class IV for control valve still has a leakage rate (therefore, not bubble tight).

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376: Eng-Tips.com Forum Policies to make the best use of Eng-Tips Forums?

RE: What is 'Bubble Tight Shutoff' ?

       yes, Class IV for has a large allowable leakage rate (1/1000 of the "rated valve capacity", whatever that is...).

       Class VI instead is the tightest for control valves, "usually specified for critical applications where the control valve may be required to be closed, without a blocking valve, for long periods of time with high differential pressures..." (see FCI-70-2, para. 4.2.5).

       Somebody finds appropriate to apply this Class to on-off valves too, especially when a measurement method more accurate than the visual one (e.g. with flow-meters) is used and gas test pressures are high, as the relevant allowable leak rates take in also test pressure in account (and not only valve size).

Hope this helps,             'NGL         

RE: What is 'Bubble Tight Shutoff' ?


Ooops. Sorry. mis-read the VI vs IV.

Class VI still has a "leakage rate", based on port diameter, and a differential pressure.

In any case, all control valve leakage classes has a leakage rate - or, "NOT" bubble tight.

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376: Eng-Tips.com Forum Policies to make the best use of Eng-Tips Forums?

RE: What is 'Bubble Tight Shutoff' ?

       Class VI allows from 1 (for ND 1" or less) to 45 (for ND 8") bubbles per minute, testing at 3.5 bar... but, for control valves, this may be still considered as a "TSO" (= tight shut off) or, better, a... "TESO" (= tight enough shut off)   winky smile

Bye,     'NGL

RE: What is 'Bubble Tight Shutoff' ?

OK. TESO it is.

"Do not worry about your problems with mathematics, I assure you mine are far greater."   
Albert Einstein
Have you read FAQ731-376: Eng-Tips.com Forum Policies to make the best use of Eng-Tips Forums?

RE: What is 'Bubble Tight Shutoff' ?

*P.S.:   "TESO" in Italian means strained, stretched, in tensione, worried... but why worrying about one bubble or two?    ;-P

Have a nice week-end!!    'NGL

RE: What is 'Bubble Tight Shutoff' ?

Good replies guys, and let me add a bit and summarize. First, I am glad you realize that "zero leakage" is not a reasonable expectation. The bubble test is size, pressure, media, and time dependent.

Most important, it is a bench test usually performed by the manufacturer, under clean conditions, at about 70deg.F. It is not valid after the valve is in service and contamination, different media,etc. will degrade the performance.

If one truly needs no leakage (and I am not defining that) then the system better accomodate leakage when it invariably will occur.


RE: What is 'Bubble Tight Shutoff' ?

Many applications require positive shutoff.  A double block and blead valve arrangement is often applied for positive shutoff.  Zero leakage is specified in API STD 598 for soft seated valves.  However, nasty hydrostatic testing fluid, welding slag and other such installation issues scratch surfaces thus eliminate "zero leakage" even if that was verified before the valve shipped.

RE: What is 'Bubble Tight Shutoff' ?

Bubble-tight is a relevant term if applied to a certain set of conditions.  It must be explained that way.  For example, if you do an seat leakage test with air as permitted by API 598, ASME B16.34, MSS SP-110, and other standards, you can place a layer of water over the top of the seat being tested and look for free flowing bubbles.  No bubbles during the test duration means it was "bubble-tight" and the valve passes the test.  You will waste a lot of time testing tight sealing valves if you try to measure minute amounts of leakage with flow meters.

It is important to recognize that the factory test is strictly for quality.  Are all the parts installed properly, are they manufactured correctly, etc.  Never try to correlate the factory test with proof of performance.  there are way to many variable and assumptions involved that the results are not vaild.

Bubble tight is a valid term provided it applies to specific, defined conditions.

RE: What is 'Bubble Tight Shutoff' ?

     Good post, bcd!

      From a NDE/NDT standpoint, bubbles detection technique is one of the many recognized and standardized Leak Testing (LT) methods, having its own defined range of accuracy and application fields (i.e. for leaks location purposes only and a minimum detectable leakage in the range of 10-3 รท 10-4 Pa*m3/s of gas flow, according to EN 1779 standard...).

      See, for example:

          -  ASME Boiler & Pressure Vessel Code (2004 edition with 2006 addenda), Section V, Article 10, Appendix I and Appendix II;

          -  ASTM E515-05 "Standard Test Method for Leaks Using Bubble Emission Techniques" ;

          -  http://www.assemblymag.com/Archives/d4526ddf8a5c9010VgnVCM100000f932a8c0____ ;

          -  http://www.atcinc.net/bubble-test.asp .

Hope this helps,                 'NGL

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