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Technical Discussions
aldo
Engineering
Italy, Joined Jan 2009, 39

aldo

Engineering
Italy,
Joined Jan 2009
39
13:36 Oct-23-2009
viscosity of penetrant

Hy everybody.... I have readed on siste www.ndt-ed.org the follow sentence: " the viscosity has little effect on the ability of a penetrant material to enter a defect but it does have an effect on the speed at which the penetrant fills a defect.". On quiz recenly for second livel MPT there was a question on viscosity:
"the speed with wich a penetrant penetrate a surface flaw is influenced to the greatest extent by wich of the following properties? :
a) densisty
b) surface tension and weat ability
c) viscosity
d) capillary action"
On base of the sentence on internet site i replied the "C" option but the exact option was "D"...
Who is right?
N.B. : the quiz are ASNT......

    
 
 
Jim Draper
Consultant, ASNT Level III MT PT RT VT
Draper NDT, USA, Joined Jul 2009, 99

Jim Draper

Consultant, ASNT Level III MT PT RT VT
Draper NDT,
USA,
Joined Jul 2009
99
15:48 Oct-23-2009
Re: viscosity of penetrant
In Reply to aldo at 13:36 Oct-23-2009 (Opening).

I would say C, viscosity. Capilary action is just a term that has to with "the possitive force that causes movement of certain liquids along narrow or tight passages." Viscosity is a veriable that can change, and changing the viscosity changes the rate of capilary action.

    
 
 
Roger Duwe
NDT Inspector, API-510, 570, 653
MISTRAS, USA, Joined Jan 2009, 148

Roger Duwe

NDT Inspector, API-510, 570, 653
MISTRAS,
USA,
Joined Jan 2009
148
21:27 Oct-23-2009
Re: viscosity of penetrant
In Reply to Jim Draper at 15:48 Oct-23-2009 .

I will agree with the test. Answer 'D' is the most correct. For any given penetrant, capillary action is the most important factor in penetration rate. Changing viscosity is a second-order variable: if the viscosity of a given penetrant changes, the rate of penetration will change; but the major influence on rate of penetration is still the capillary action.

    
 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 520

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
520
22:08 Oct-23-2009
Re: viscosity of penetrant
In Reply to Roger Duwe at 21:27 Oct-23-2009 .

Can't agree with that, capillary action is not a property of the penetrant. Its the process that occurs.

    
 
 
anjafo79
NDT Inspector
Norway, Joined Aug 2009, 204

anjafo79

NDT Inspector
Norway,
Joined Aug 2009
204
22:47 Oct-23-2009
Re: viscosity of penetrant
In Reply to Joe Buckley at 22:08 Oct-23-2009 .

which would you change if you were manufacturing it to make it penetrate faster or slower? the only reason I can think off why you would need to know this.

you wouldn't (or couldnt) change capillary action as its a process?
you could change wetting ability or viscosity though?

    
 
 
Jim Draper
Consultant, ASNT Level III MT PT RT VT
Draper NDT, USA, Joined Jul 2009, 99

Jim Draper

Consultant, ASNT Level III MT PT RT VT
Draper NDT,
USA,
Joined Jul 2009
99
15:50 Oct-24-2009
Re: viscosity of penetrant
In Reply to anjafo79 at 22:47 Oct-23-2009 .

The viscosity of the penetrant can change due to tempurature. The manufacturer also controls the viscosity of the penetrant. In colder tempuratures, the penetrant gets thicker, resulting in the capilary action moving slower. This will mean a need for an increased dwell time.

    
 
 
ezio
Other, Retired ex Laboratory Technical Manager
OMECO Research Centre, Italy, Joined Sep 2008, 273

ezio

Other, Retired ex Laboratory Technical Manager
OMECO Research Centre,
Italy,
Joined Sep 2008
273
16:21 Oct-24-2009
Re: viscosity of penetrant
In Reply to aldo at 13:36 Oct-23-2009 (Opening).

Caro Aldo,
anch'io sono d'accordo sulla viscosità (C).
Però l'ASNT ai miei tempi metteva per ciascuna domanda anche un riferimento ad un testo di riferimento, se lo trovi fammelo sapere.



ASNT my day gave also the reference to the page of any NDT-book, I suggested Aldo to search it and tell me.
However I think answer C is correct.
ciao,Ezio

    
 
 
chen zhiqiang
Teacher, - - engineering for
HEBEI UNIVERSITY COLLEGE OF Qlty.&Tech., China, Joined Oct 2009, 5

chen zhiqiang

Teacher, - - engineering for
HEBEI UNIVERSITY COLLEGE OF Qlty.&Tech.,
China,
Joined Oct 2009
5
03:03 Oct-25-2009
Re: viscosity of penetrant
In Reply to Jim Draper at 15:50 Oct-24-2009 .

I think 2 concepts will be cleared: 1 is SP( STATIC STATE PENETRATION) IS NOTHING TO DO WITH viscosity and this is the nature bility of liquid penetrant;but KP(Danamic penetrant) is relative with viscosity,and it will affect the penetrant speed rate that mean dwell time will be long and another will be affect the developing time or mask the defect. for such status,you should do contrast test between block and testing specimen to assure the dwell time and developing time.

    
 
 
J.K
J.K
06:28 Oct-25-2009
Re: viscosity of penetrant
In Reply to aldo at 13:36 Oct-23-2009 (Opening).

As in the ASNT Guide ' Viscosity affects the rate of penetration ' . Higher the Viscosity slower the Penetration & Lower the Viscosity faster the penetration, But if a liquid has to penetrate it has to have low contact angle & good wettability which are responsible for the cappillary action of a liquid. A liquid with high contact angle & low viscosity may not even penetrate a flaw. So 'D' would be right choice

    
 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 520

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
520
11:36 Oct-25-2009
Re: viscosity of penetrant
In Reply to J.K at 06:28 Oct-25-2009 .

Bit worrying this, as a 15 year level III (admittedly not in PT) i would have said 'answer is wrong, you were right, its C' and wished they could have a higher standard of test papers. But it seems we can't even get a consensus here is the group....

    
 
 
aldo
Engineering
Italy, Joined Jan 2009, 39

aldo

Engineering
Italy,
Joined Jan 2009
39
18:33 Oct-25-2009
Re: viscosity of penetrant
In Reply to Joe Buckley at 11:36 Oct-25-2009 .

Hi all and tanks for your words and your opinio... While i was reading your opinions i readed on same above inetrnet site the expression of the fill time. In this formula i have not viscosity term but i have only the capilarity term (wite angle and energy surface). So on base of this i think that the viscosity i have not influence on speed of penetrant to penetrate into flaw...Is correct my opinion? and is possibile to have relation between the fill time and the speed ?
tanks and best regards....

    
 
 
Theo Micottis
Theo Micottis
16:23 Nov-09-2009
Re: viscosity of penetrant
In Reply to aldo at 18:33 Oct-25-2009 .

Ciao Aldo, sometimes the questions are wrong not the answers. On the web-site you mentioned , the formula of fill times Fill time = (2l2m)/ rcosq sLG include the viscosity m.

    
 
 
aldo
Engineering
Italy, Joined Jan 2009, 39

aldo

Engineering
Italy,
Joined Jan 2009
39
17:42 Nov-09-2009
Re: viscosity of penetrant
In Reply to Theo Micottis at 16:23 Nov-09-2009 .

tanks and sorry for my error....
Aldo

    
 
 
pratchaya kittisakkul
pratchaya kittisakkul
21:36 Nov-09-2009
Re: viscosity of penetrant
In Reply to aldo at 13:36 Oct-23-2009 (Opening).

I think vicosity is a major influence in wetting ability and the contact angle.But minor in ability to enter a defect,that could be capillary action.Some highly viscous fluids, such as molasses, have very good penetrating ability, while some low viscosity liquids, such as pure water, have very poor penetrating ability. However, from an application viewpoint, viscosity affects the speed with which a penetrant enters a discontinuity.Therefore both viscosity and capillary action can determine to apply the time to penetrate or Dwell Time.

    
 
 
John Brunk
Engineering, NDT Level III
Self employed, part-time, USA, Joined Oct 1999, 159

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
159
18:10 Nov-10-2009
Re: viscosity of penetrant
In Reply to pratchaya kittisakkul at 21:36 Nov-09-2009 .

I think this multiple choice question should not even be on an exam, whether Level I, II or III. Capillary action is an event that happens. Density and viscosity are properties of the penetrant. Wetability is a property of the solid surface. Surface tension is related to the solid surface and to cohesive or adhesive properties of the penetrant. I'm not sure that the exact mechanism is really all that well understood and I don't think NDT personnel need to be experts in this. we do need to understand its practical aspects. One thing we can tell from using test blocks is that penetration time may have to be increased at very low ambient temperatures when the viscosity of the penetrant (or any liquid) is higher. This establishes a relationship between viscosity and the speed with which a penetrant enters a surface flaw.

    
 
 
Kunal
Kunal
11:34 Feb-13-2012
Re: viscosity of penetrant
In Reply to aldo at 13:36 Oct-23-2009 (Opening).

Dude, it's 'B'

    
 
 
balwinder singh
Other,
India, Joined Nov 2011, 16

balwinder singh

Other,
India,
Joined Nov 2011
16
12:25 Feb-16-2012
Re: viscosity of penetrant
In Reply to Joe Buckley at 11:36 Oct-25-2009 .

Mr.Joe,

i agree with you actually peoples confusing with capillary action fundamentals and speed. according to me speed of filling ,its "C".

    
 
 
Miles Simmons
Miles Simmons
20:56 Oct-18-2012
Re: viscosity of penetrant
In Reply to balwinder singh at 12:25 Feb-16-2012 .

The key to the question is the word "speed". The answer should be viscosity. Low viscosity equals a greater rate of speed in which the penetrant penetrates the defect. And obviously, higher viscosity means decreased speed. Caplliary action is just the ability of the pentrant to be effective penetrating into tight flaws. It doesn't have much to do with the speed in order to accomplish it.

    
 
 
Amir Malik.
Amir Malik.
15:03 Aug-19-2013
Re: viscosity of penetrant
In Reply to aldo at 13:36 Oct-23-2009 (Opening).

viscosity is property of liquid and control the rate of flow but capillary action is the ability of liquid to flow in narrow spaces without the assistance of, and in opposition to, external forces such as gravity.It occours because of intermolecular attractive force between the liquid and solid surrounding sufrace.Both Answers C & D are very close and both have affect on rate of penetration.but the closest answer will be (D) in my opinion.which seems to me more acurate.

    
 
 

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