Glossary entry (derived from question below)
French term or phrase:
poids-moment
English translation:
moment weight
Added to glossary by
Jennifer Levey
Feb 18, 2018 21:22
6 yrs ago
7 viewers *
French term
poids-moment
French to English
Tech/Engineering
Engineering: Industrial
Steam turbine blades
This is a parameter to be measured for a LP steam turbine blade — NOT the entire turbine, but for each blade, individually, and statically.
I have found out that poids-moment is expressed in kg/m — the same units as are used to express torque; but I can't quite get my head round the idea of torque as a static measurement on a component?
I have found "weight mass moment", but very few instances of it, and all of them apparently from multi-lingual translated sites which don't inspire me with confidence.
Even allowing for minor syntax differences, I have not found anything at all on Termium, GdT, nor IATE — not to mention here on KudoZ!
There aren't that many examples of it on the 'Net even in FR, and I can find virtually no convincing refs. where it is meaningfully collocated with 'torque' in a bilingual context.
Can anyone with specialist knowledge of mechanics please help me out here, as my deadline is looming and I am rushing...
Thanks in advance!
I have found out that poids-moment is expressed in kg/m — the same units as are used to express torque; but I can't quite get my head round the idea of torque as a static measurement on a component?
I have found "weight mass moment", but very few instances of it, and all of them apparently from multi-lingual translated sites which don't inspire me with confidence.
Even allowing for minor syntax differences, I have not found anything at all on Termium, GdT, nor IATE — not to mention here on KudoZ!
There aren't that many examples of it on the 'Net even in FR, and I can find virtually no convincing refs. where it is meaningfully collocated with 'torque' in a bilingual context.
Can anyone with specialist knowledge of mechanics please help me out here, as my deadline is looming and I am rushing...
Thanks in advance!
Proposed translations
(English)
4 +3 | moment weight | Jennifer Levey |
References
refs. | Rachel Fell |
Change log
Feb 21, 2018 10:43: Jennifer Levey Created KOG entry
Proposed translations
+3
22 mins
Selected
moment weight
Explained here:
https://www.space-electronics.com/KnowHow/pan_weight_vs_mome...
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Note added at 26 mins (2018-02-18 21:49:33 GMT)
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It has the same units as torque because it involves the apparent "weight" at the centre of gravity of the rotating blade, hence a mass term (kg) and a distance term (m), as distinct from the "pan weight" (dead-weight - kg only) of the blade when at rest.
https://www.space-electronics.com/KnowHow/pan_weight_vs_mome...
--------------------------------------------------
Note added at 26 mins (2018-02-18 21:49:33 GMT)
--------------------------------------------------
It has the same units as torque because it involves the apparent "weight" at the centre of gravity of the rotating blade, hence a mass term (kg) and a distance term (m), as distinct from the "pan weight" (dead-weight - kg only) of the blade when at rest.
Peer comment(s):
agree |
Rachel Fell
: Was about to answer with the same term - will post other refs. below
2 mins
|
agree |
philgoddard
18 mins
|
agree |
B D Finch
20 hrs
|
neutral |
Daryo
: but your explanation is wrong - weight is a force measured in kgf (kilogramme-force) as opposed to mass [quantity of matter] measured in plain kg (kilogramme) // the difference: in space your are "weight-less" but not "mass-less" ...
21 hrs
|
neutral |
chris collister
: See Space Electronics' own definition of "moment weight" but note discussion above of mass vs. weight!
1 day 30 mins
|
4 KudoZ points awarded for this answer.
Comment: "Thanks a lot Robin! This is indeed the correct term in my context, as validated by the end customer.
Your explanations have been very helpful for me in order to try and grasp these concepts more clearly."
Reference comments
26 mins
Reference:
refs.
https://www.space-electronics.com/contentAssets/...Papers/Ne...
Space Electronics has designed a special static balance machine to measure turbine blade moment. Previously this task has been accomplished using knife edge and load ... This paper discusses the various steps in the process of balancing a turbine rotor. The .... identical to the moment weight of the blade 180 o away .
https://tinyurl.com/ybslo86l
50 ton Skoda lathe, Schenck balancing machines, conventional milling machines, blade tip grinding machine, Schenck moment weight balancing machine, welding machines, radial drilling machine, a spare parts depot, along with 2 overhead cranes with a load bearing capacity of 60 and 15 tonnes each
http://www.corrtechenergy.com/rotor_repair_overhaul_services
Space Electronics has designed a special static balance machine to measure turbine blade moment. Previously this task has been accomplished using knife edge and load ... This paper discusses the various steps in the process of balancing a turbine rotor. The .... identical to the moment weight of the blade 180 o away .
https://tinyurl.com/ybslo86l
50 ton Skoda lathe, Schenck balancing machines, conventional milling machines, blade tip grinding machine, Schenck moment weight balancing machine, welding machines, radial drilling machine, a spare parts depot, along with 2 overhead cranes with a load bearing capacity of 60 and 15 tonnes each
http://www.corrtechenergy.com/rotor_repair_overhaul_services
Note from asker:
Many thanks, Rachel, for finding those very informative and totally relevant references for me! |
Discussion
I'm sorry if I misled anyone: the units used do not appear in my document, they simply cropped up as a result of my own research into this and related terms; the use of / instead of . may be the result of my rushed misinterpretation of a not-terribly-clear reference.
And no, Daryo, there are no formulæ given anywhere — this just appears in a list of operations to be carried out.
Indeed, any variation in the moment weight may also be due to some quite alarmingly large amounts of machining that may be done to these blades as part of the reconditioning process. Hence I suppose why re-balancing becomes even more important than usual.
The widespread cavalier [mis]use of "kg" when "kgf" should be used (= "linguistics") can not change basic physics.
"The academic distinction between mass and weight (not to mention “kilogram-force * meter”) is somewhat irrelevant in this context."
The distinction between mass and weight is fundamental/basic physics, NOT some "academic semantics" and is extremely relevant in this context.
4. One more for good measure: as Chris has said already, “mass moment” is somewhat meaningless – especially when the term “moment weight” is already used in the relevant literature.
2. The academic distinction between mass and weight (not to mention “kilogram-force * meter”) is somewhat irrelevant in this context. Since the two blades are tested in identical conditions, the ratio of the measurements on a pair of blades (which indicates the “quality of balance”) will be the same, regardless of the units used. Superfluous factors introduced by the mentioned academic distinctions will all cancel out in the engineering context.
It is not entirely impossible that what they wanted to measure was really a mass (in kg, not in kgf or N), [at a certain distance form the axis of rotation] in which case it would more have to do with "rotational inertia" and/or balancing the turbine.
The US Space Electronics company seems to be one of not many organisations to use this term. They define "Moment Weight = (Mass of the blade) x (Distance from the engine centerline to the center of gravity of the blade)" (of course they mean "weight" of the blade, not mass), using the utterly bizarre unit of oz.inches. If only engineers understood physics, there would be much less confusion!