What is an Isometric Drawing?
An isometric drawing is a type of pictorial drawing in which three sides of an object can be seen in one view.
It’s popular within the process piping industry because it can be laid out and drawn with ease and portrays the object in a realistic realistic view. view.
Sometimes it is used in lieu of plans and elevations but typically it is used to supplement the plan drawings
Isometrics are used as fabrication & shop drawings for pipe run fabrication
Isometrics also provide a drafter with the ability to calculate angular offsets in the pipe run.
Isometric Layout:
Isometric lines: one vertical & two at 3! from hori"ontal Isometric lines can be measured #on$isometric lines: lines: lines #% parallel parallel to the isometric isometric lines ' these lines cannot cannot be measured
()ample of isometric a)is *ou will use the isometric a)is on A++ of your isometric drawings, In the e)ample at left- note that all directions of the pipe match the three isometric a)is lines
Scale
isometrics are seldom drawn to scale ' istrometric him s/hi v0 theo t1 l2
however- pipe lengths should be shown proportionately
many companies draw isometrics on $si"e paper 4556 ) 5768 which is a limited space so sometimes proportion may be
because of the lac/ of scale in an an isometric- it’s it’s I9%; I9%;A# that that the written dimensions dimensions are accurate
Direction & location:
location and direction help to properly orient the isometric drawing
a north arrow give direction and should A+
structural reference points that provide location can be shown on isometric
dimensions 9=S always be given to points of reference> such as structures- e)isting e?uipment@etc
coordinates should also be shown on the isometric drawing
Isometric planes:
there are three planes that e)ist in isometric drawings
with three planes- there are a number of ways for valves and fitting to be shown
the illustration shown above and on page 5B in your boo/ shows the planes and possible positions of fittings & valves
remember that if pipes or features are parallel in the piping layout- they they’ll be parallel in the isometric view
Fitting symbols and orientation:
when orienting fittings and valves it’s important to /now that there are methods in this orientation process
good methods and poor
the general rule for producing an isometric using C%%D techni?ues- is to draw the fittings so they are parallel to the last direction change or branch in the pipe
#ot ice how the flow of of the isometric is continuous continuous and provides a clear clear picture of the pipe run
#ot following the the Egeneral rule6 leads to a chaotic chaotic loo/ing isometric isometric @ it doesn’t loo/ loo/ professional
fittings are drawn the same shape as they appear on the plan & elevation drawings (FG( they’re they’re at an isometric angle
elbows can be drawn a couple of ways@ chec/ with company standards
In this class we will use s?uare corner elbows '
not only is this the most typical method used- but it’s also ?uic/er to draw.
Gurved (lbow ;epresentation
S?uared (lbow ;epresentation Connected piping:
one run of pipe per isometric drawing branches of the pipe run or continuations are placed on other drawings @ typically t ypically shown as short portion of dashed line line on main pipe run
usually a note indicates he name or specification of the branch line
e)isting piping is sometimes shown using double line method or dashed lines ' in this class we will use dashed lines
either method is useful in that it distinguishes new pipe from e)isting piping
Isometric drawing techniques:
o increase drawing efficiency:
Greate a prototype for isometric drawings
set up grid- snap- isometric plane orientation- border and title bloc/- %9- te)t styles & dimension settings
Develop library of isometric symbols
valves- fittings- instrumentsinstruments- e?uipment@ common drawing components
Greate dimension styles in all three isometric planes
Gonstruct menus that you can pic/ symbols from
Drawing Isometric !!sets:
Offset:
indicates that a piece of pipe is shifted from one line of direction to another
is done with a fitting 4typically a H! elbow8
one of the few times you might have Eartistic license6 in ma/ing a piping drawing
Horizontal offsets: offsets:
If you draw a hori"ontal pipe with a H! elbow running form southeast to northwest technically correct- it would loo/ li/e a vertical line@ to prevent confusion- the offset is drawn J ! from vertical to give the illusion of the angle.
hat’s why many companies use a Es?uaring$in6 plane within the plane of the offset
Vertical Offsets:
hese offsets can get just as confusing as the hori"ontal hori"ontal offsets. =sing the same techni?ues> techni?ues> J ! and the Es?uaring ' in6 planes help remedy the visuali"ation of these offsets as well. K*I: As a drafter- you should always be aware of some of the confusing ?ualities inherent to isometric piping drawings drawings and ta/e measures to ensure ensure the drawings are easily understood. understood.
Calculating Isometric !!sets
Although you can Eget away6 with an educated guess as to ma/ing an angular offset easy to see when laying out an isometric- you can"t ma/e a Eguess$ti$mate6 when it comes to determining pipe lengths and angles. So- pull out the old calculator- paper- pencil & a IC eraser and let’s get started. he Ebasic6 calculations any pipe drafter uses are those involving trigonometry and right angles. ythagoras- a Lth century .G. Cree/ philosopherphilosopher- came up with a way to deal with calculations involving right angles@ and it’s called the@ anyoneM @. AnyoneMMM #ythagorean $heorem
SimplySimply- what ythagoras concluded was that when wor/ing with right angle triangles the s?uare of the hypotenuse is e?ual to the sum of the s?uares of the two sides. c% a% ' b%
()ample: #ythagorean $heorem 4p. 38
5. Start off off with what’ what’ss given given or what you you can determin determinee from the pipe pipe drawing drawing itself. itself. a8
b8 y doing simple subtractionsubtraction- we can come up with the the length for side : 55’$N O6 ' L’$36 P ’$L O6 %; you can subtract subtract the elevations elevations given and get the same same dimension for for side A. c8 Since Since P A: A: side side A P ’ $L O6 O6 as well. well.
. #ow all all you have have to do is plug the the numbers numbers into into your your formula: formula: a8 cQ P 4’ 4’ $L O68 O68QQ R 4’ 4’ $L O68 O68QQ b8 cQ P 4.B8Q R 4.B8Q c8 cQ P 3. 3.H7 H7N N R 3. 3.H7 H7N N d8 cQ P L.NBH e8 c P L.NBH f8 c P 7.B7 g8 c P 7’ $N 55T5L6 T5L6 Sol*ing Compound +ngles:
;=#: +ength of total offset in direction of pipe run
S(: Depth of offset
;%++: readth of offset
;AU(+: rue length of pipe through offset
K*I: Separate tutorial E
wo wo planes are used in dimensioning and labeling$hori"ontal and vertical. DIMENSIONING PRACICES: PRACICES:
5. est way way to dimensio dimensionn a pipe is to its center centerline line at the interse intersectio ctionn point point . ry to to /eep all all dimensio dimensions ns outside outside the piping piping view when when possib possible le 3. Dimensions should A+< A+
Iso!etric lettering: lettering:
asic guidelines for lettering isometric drawings: 5. If the pipe’s pipe’s verticalvertical- the the lettering lettering should should be written written vertica vertically lly and at 3! 3! angle angle . If pipe is in hori"ontal hori"ontal plane- the the lettering will appear as if it is lying lying down and will be oriented on both 3! angles 3. Dimensio Dimensions ns appear appear to be lying lying down if the the pipe is hori"on hori"ontal tal or standin standingg on end if the pipe pipe is vertical.
