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1
Section III:
Turboexpanders: Bits and pieces...

2
Introducing
A
Turboexpander and its
Major Components

3
First…
Do you need a
Turboexpander?

5
Next:
What size Turboexpander
do you need?

6
India
Auraiya, Uttar Pradesh
Project
2340 Kw @
222,731 kg/hr

7
Auraiya, Uttar Pradesh
Project
2340 Kw @
222,731 kg/hr
A MTC Frame 4.0 Turboexpander

11
Establish design criteria and
operational limitations…
Example:
MTC-464, EC-4.0

12
The Auraiya
Turboexpander:
Machine
Characteristics…

13
The Auraiya Turboexpander:
Machine Characteristics, Gas Analysis…

14
Machine Characteristics, flows, inlet and
discharge pressures and temperatures…

15
Perform sizing calculations
and select construction
material…

16
Machine Characteristics, Gas
Analysis…

17
Construction material:
Housings: Stainless & Carbon steel
Wheels: Aluminum alloy
Shaft: 17-4 Stainless steel
Seals: Brass, Teflon, Neoprene,
Micarta (various grades), etc.

18
Expander Sizing
Frame 5
Family
Frame 4
Family

19
Expander Sizing
Frame 5
Family
Frame 4
Family

20
Size Speed Flowkg/hr HP
Frame 1: 85K 25K 300
“ 2: 50K 40K 600
“ 2.5: 40 K 50K 800
“ 3: 30K 70K 1000

21
Flange Size
Frame
Size
Approx. max
Power (kW) Exp Comp
Frame 1 200 3”/4” 6”/6”
Frame 2 1200 4”/6” 8”/8”
Frame 2.5 2000 6”/8” 10”/10”
Frame 3 3500 8”/10” 12”/12”
Frame 3.5 6000 10”/12” 18”/18”
Frame 4 8000 12”/14” 20”/18”
Frame 5 10000 20”/24” 24”/24”
Frame 6 18000 24”/30” 36”/36”

22
Flange Size
Frame
Size
Approx. max
Power (kW) Exp Comp
Frame 1 200 3”/4” 6”/6”
Frame 2 1200 4”/6” 8”/8”
Frame 2.5 2000 6”/8” 10”/10”
Frame 3 3500 8”/10” 12”/12”
Frame 3.5 6000 10”/12” 18”/18”
Frame 4 8000 12”/14” 20”/18”
Frame 5 10000 20”/24” 24”/24”
Frame 6 18000 24”/30” 36”/36”

23
Process Information
• Expander Side
–Inlet Pressure and Temperature
–Outlet Pressure
–Mass flow
–Gas composition

24
Process Information
• Compressor flow
–Gas composition Compressor
side
–Inlet pressure and temperature
–Mass

25
Sizing steps
• Run process simulation software
–Peng-Robinson Equation of State
–Soave-Redlich-Kwong (SRK)
Equation of State
• To obtain
–Expander isentropic enthalpy
drop
–Expander outlet volumetric flow
–Compressor inlet volumetric flow

26
Selection of Expander Tip Speed
90%
92%
94%
96%
98%
100%
40 60 80 100 120 140
ISENTROPIC ENTHALPY, BTU/LB
PERCENT
OF
OPTIMUM
EFFICIENCY
OPTIMUM EXPANDER TIP SPEED
0
500
1000
1500
2000
0 20 40 60 80 100 120 140
OPTIMUM
TIP
SPEED,
FT/SEC

27
Specific Speed
  4
/
3
H
Q
N
Ns


• Ns = specific
speed
• N = shaft speed
• Q = discharge
flow
• H = isentropic
enthalpy drop

28
Sizing Turboexpanders
RADIAL INFLOW EXPANDER EFFICIENCY
50.0
55.0
60.0
65.0
70.0
75.0
80.0
85.0
90.0
95.0
0 0.2 0.4 0.6 0.8 1 1.2
Dimensionless Specific Speed
Maximum
Isentropic
Efficiency,
%

29
Optimum Tip Speed
• U2/Co = speed
parameter
• N = shaft speed
• D = wheel
outside diameter
• H = isentropic
enthalpy drop
H
D
N
C
U 

0
2

30
Optimum Tip Speed
Efficiency Correction
0
0.2
0.4
0.6
0.8
1
1.2
0 0.2 0.4 0.6 0.8 1
U2/Co
Efficiency
Correction
Factor

31
Sizing (continued)
• From Specific Speed and Speed
Parameter, calculate Expander Isentropic
Efficiency.
• Calculate Expander Power. Check
torque and power density. Select
bearings.

32
Compressor Sizing
• Calculate Compressor power by
subtracting losses from expander
power
• Estimate Compressor efficiency
and calculate compressor
polytropic head rise.

33
Specific Speed
  4
/
3
H
Q
N
Ns


• N = shaft speed
• Q = inlet flow
• H = polytropic
enthalpy rise
• Ns = specific
speed

34
COMPRESSOR PERFORMANCE
50%
60%
70%
80%
90%
100%
0 0.5 1 1.5 2 2.5
Polytropic
Efficiency,
%

35
Compressor Sizing
p
H
U


2
• U2 = Tip speed
• H = Polytropic
head rise
• Psi = Head
coefficient
• N = Shaft speed
• D = Wheel
outside diameter
N
U
D 2


36
COMPRESSOR SIZING
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1 1.5 2 2.5
Polytropic
Head
Coefficient

37
Optimizing Performance
U2/Co
Q2/N
Contours of constant
efficiency

38
• Trim Compressor wheel to increase
speed
–Result: more optimum U2/Co for
expander and higher efficiency.
• Trim Compressor wheel, plus new
follower
–Result: “Shift” compressor
performance curve to lower flow
and avoid recycle.

39
• Trim Inlet Guide Vanes to pass more
flow
–Flow that bypasses the expander
through the J-T valve has zero
efficiency. By trimming the IGV’s,
or adding to their height, more flow
can pass through the expander,
producing more efficiency, more
power, and therefore more product!

40
• If process flows or pressures are
significantly different from the
original design, then a “redesign”
may be called for.
–Replace all old aerodynamic
parts with new parts optimized to
the new process conditions.

41
The replacement of select aerodynamic
parts can improve performance as long
as you remain within the limits of the
original housings.

42
For example: Replace Expander and or
Compressor Wheel(s) and Followers
as required.

43
Replace Expander wheel, small for
big, to increase capacity up to the
housing’s limit…

44
Replace Compressor wheel, small for really big…

45
Not too big though: The housings limit to a point!

46
Replace Expander discharge diffuser
cone…

47
Go for a really large one…

48
Replace Inlet Guide Vanes (IGV’s)…

49
They come in a variety of sizes…

50
Replace Compressor Diffuser
spacers as needed…

51
Compressor Discharge Diffuser
Spacers determine this gap’s size…

52
The size of this gap is thereby adjusted to
optimize Compressor performance…

53
Turboexpander
Documentation:

54
Documentation:
1. Manuals
2. Engineering
Drawings and Prints

55
Vol I = Operations &
Maintenance Manual
Vol II = Sub-Vendor data
Vol III = Certificates
1. Manuals

56
Vol I = Operations &
Maintenance Manual
1. Manuals

57
Vol 1:
Typical
Operations
& Maintenance
Manual

58
Vol 1:
Typical
Operations
& Maintenance
Manual

61
2. Engineering Drawings
and Prints:

62
A partial listing of
selected Engineering
prints.

63
MAFI-TRENCH CORPORATION
3037 INDUSTRIAL PARKWAY, CALIFORNIA 93455 USA THE
STANDARD OF EXCELLENCE IN TURBOEXPANDERS
PIPING AND INSTRUMENTATION DIAGRAM
SCALE FRAME SIZE DRAWING No. REV. SHEET 1
None ECM4.0 464D3 D OF 3
The Drawing/Print Legend...

64
The MTC Drawing Number

65
Engineering Prints are
numbered sequentially,
regardless of size...
(See page 8-1 in Vol I)
Print/Drawing Sizes:
A = A4, B = 2X A4,
C = 6X A4, D = 8X A4

66
Numbering prints:
464D1 = Expander Service Assembly
464D2 = Machinery Arrangement
464D3 = Piping and Instrumentation
464D4 = Electrical Control System
464D5 = Local Gauge Board Layout
464D6 = Junction Box Layout
464B15 = Assembly Set-up Dimensions
464A45 = Control system Setpoints
464D68 = Control System Overview
464A10, A12, A13, A37, etc., etc.

67

68

69
Drawing Produced by MTC…

70
Drawing Title…

71
Scale, if any…

72
Type machine and Frame size:
Expander-Compressor, Magnetic
Bearings, Frame 5.0

73
Drawing number based on:
assigned machine number: 589

74
None EC5.0 464D3 D OF 3
Print Size (original engineering print
on file at MTC factory): A = A4, B
= 2X A4, C = 6X A4, D = 8X A4

75
File sequence number:

76
NOTE:
Engineering Prints are
numbered and filed sequentially,
regardless of size, according to
the “File Sequence Number”
(See page 8-1 in Vol I)
For example: 1,2,3,4,5,6, etc.

77
Revision Indicator: A, B, C, D, etc.

78
Sheet counter/indicator…

79
Turboexpanders Up Close
Our study of the turboexpander
will be addressed in the following sequence:
 Major Components:
 Inlet Guide Vanes (IGV’s)
 Seals,
 Bearings

80
Turboexpanders Up Close
 Seal Gas and Lube Oil Systems
 Automatic Thrust Equalization (ATE)
 Surge Control System
 Instrumentation & Control Systems
 Operations & Maintenance

81
Construction material for
each component based on:
1. Operating pressures
2. Process temperatures
3. Contents of process gas

82
Construction material:
Housings: Stainless & Carbon steel
Wheels: Aluminum alloy
Shaft: 17-4 Stainless steel
Seals: Brass, Teflon, Neoprene,
Micarta (various grades), etc.

83
The Turboexpander Has Four Major Sections

84
All sections are bolted together for superb
mechanical strength

90
The Bearing Housing holds:
Wheels; Bearings; Shaft; Seals

94
3: The Compressor Housing...

95
Comp Inlet Spool Piece
4.
This facilitates maintenance actions

96
4: Compressor Inlet Spool Piece

97
Expander Compressor
Bearing Housing
Inlet Spool Piece

98
Major Components;
Following the Inlet Gas
Flow Path

99
The Gas Flow Path:
1. Piping and machine housings
2. Inlet Guide Vane Assembly (IGV’s)
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

100
Expander
Inlet
The horizontal inlet to this expander
model is designed to meet the plant’s
piping configuration...

101
Vertical Expander
Inlet
The vertical inlet to this expander model is designed
to meet the plant’s piping configuration...

102
The Gas Flow Path:
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

103
Flow of gas into an expander loop...
E

104
High-pressure gas from Inlet
Scrubber
(222,731 kg per hour)
52 kg/cm²
@ -68° C
22kg/cm²
@ -98° C
Inlet gas flow is expanded and chilled...

105
High-pressure gas in to the expander,
Expander Gas Flow Path
Inlet
52 kg/cm²

107
Low-pressure, cold gas exits the expander,
Discharge
22kg/cm²
@ -98° C

108
Expander discharge to Low Temperature
Separator…

109
Then, enters the Gas/Gas Heat Exchanger

110
…to the turbine-driven Compressor.

111
Compressor Gas Flow Path
After passing through the Gas/Gas Heat
Exchanger, the now-dry, warm gas returns to the
compressor inlet...

113
…from the turbine-driven Compressor.

114
Then, to Export Compressor...

115
The Gas Flow Path:
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

116
The IGV’s are used to control
the mass flow of gas through
the Turboexpander.

117
Expander Inlet Guide Vanes

118
High-pressure gas in to the expander,
Inlet

121
The Expander Inlet Guide Vanes

122
The Inlet Guide Vane (IGV) Assembly is located at the
inlet to the expander wheel.

123
Expander housing with IGV’s Installed…

124
Inlet gas is admitted to
the expander housing
and directed towards
the IGV’s…

125
IGV’s
Inlet gas at 52
kg/cm², pre-
cooled in the gas-
to-gas inlet heat
exchanger, enters
the expander
housing at point
number 1...
1

126
IGV’s
This inlet stream
is distributed
throughout the
interior of this
housing,

128
Process gas flows into IGV’s

129
High energy inlet gas flows into
the IGV’s
Inlet Gas
Inlet Gas

130
The Expander Inlet Guide
Vanes (IGV’s) provide a means
to control mass flow of gas
through the Turboexpander,

131
This results in operational
changes, such as high shaft
rotational speed, and low outlet
pressures and temperatures.

137
Note: Half of the total
pressure drop (30 Kg.cm²),
and half of the total
temperature drop (30°C) in
the expander, occurs across
the Inlet Guide Vanes...

138
... exchanging pressure energy for velocity energy over the
IGV’s, the resultant kinetic energy causes the turbine
wheel to spin, dropping pressure and temperature as that
work energy is transferred to the rotating shaft.

139
Question: How does the
apparently simple IGV
function?

140
The shape of the IGV defines
its function!

144
Process gas flows over the
Inlet Guide Vanes…

145
The velocity of the process gas flow
increases exponentially as it moves over the
airfoil-like shape of the vanes…

146
... exchanging pressure energy for velocity energy over the
IGV’s, the resultant kinetic energy causes the turbine
wheel to spin, dropping pressure and temperature as that
work energy is transferred to the rotating shaft.
Discharge

147
The actuator rod is
moved by a pneu-
matic positioner
mounted outside
the expander.

148
The pneumatic IGV positioner...

149
This positioner
opens and closes
the IGV’s to
control the mass
flow through the
expander.

150
Internal stops control position of
full open/full closed for IGV’s

154
The Inlet Guide Vane (IGV) Assembly is located at the
inlet to the expander wheel.

156
All components of the IGV Assembly are designed to
operated smoothly under operating pressure.

157
The Inlet Guide Vane
Pressure �龱�Բ�…

158
The Pressure Ring Assembly

159
The Pressure Ring, by exerting constant pressure
against the IGV’s axially, prevents the leakage of inlet
gas over or under them. The ring can move axially, but
not rotate, squeezing the IGV’s against the follower.

160
1. Pressure ring Guide and its Teflon Omni-Seal
2. Pressure Ring
1
2

161
The Pressure
Ring is installed
within the
expander
housing,
partially
covering the
Inlet Guide
Vanes, while
completely
surrounding the
expander
wheel…

162
The Pressure
Ring surrounds
the expander
wheel, but does
not rotate…

163
The IGV Pressure Ring, transparent in this
view…

164
The IGV Pressure �龱�Բ�…

165

166

167

168

169
The IGV Pressure
Ring prevents
loss of energy
over or under the
vanes.

170
The Pressure Ring, by exerting constant pressure
against the IGV’s axially, prevents leakage of inlet gas
over or under them, forcing the flow through the vanes.

171
Clamping Force Calculations

172
Clamping Force Calculations

173
Clamping Force
Calculations

174
The IGV’s are clamped between the
expander wheel follower (#1) and the
Pressure Ring (#2)
#1
#2

175
Considerable effort is expended to calculate
the required and actual “clamping” force
exerted by this vital component.

176
37 kg
Clamping Force Calculations: Typical,
using pressures indicated…

177
“Clamping” versus “Lift-off ��ǰ��”

178
Clamping Force
Calculations: Typical

179
Total Clamping Force
Calculations

180
Lift-off Forces
Calculations: EC-4.0

182
Process gas flows into the IGV’s

183
Inlet process gas @ 52
kg also flows into this
small open space behind
the Pressure �龱�Բ�…
52 kg

184
With inlet pressure at
approximately 52 kg,
a composite
Clamping force of
2350 kg/f is felt
against the Ring
(IGV’s open)
52 kg
37 kg

185
As a result, the IGV’s are clamped
between the expander wheel follower (#1)
and the Pressure Ring (#2)
#1
#2

186
IGV Clamping forces
with IGV’s open:
Net Clamping Force =
2350 kg/f
Total Effective
Clamping Force

187
IGV Clamping forces
with IGV’s closed:
Net Clamping Force =
1600 kg/f
Total Effective
Clamping Force

188
Gas is directed to the vanes…

189
The Pressure Ring holds the
IGV’s in place…

192
Expander Housing cover (right) with
Pressure Ring Installed...

193
Expander
Housing with
IGV’s in
place...

194
Pressure Ring
in normal
position over
IGV’s, but
Expander
Housing cover
removed…

195
Pressure Ring
clamping
forces…

197
The pressure ring, showing it extended
towards the IGV’s.

198
Expander Housing Cover closed...

199
Summary: The Expander Inlet
Guide Vanes (IGV’s) provide a
means to control mass flow of
gas through the
Turboexpander; they are not
designed to stop the flow of inlet
gas.

200
The Gas Flow Path:
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

202
Past the IGV’s, the inlet gas next flows
through the expander turbine wheel…

203
The turbine wheel is the heart of the
Turboexpander; it extracts the energy...

204
What makes an
expander run?

205
An expander runs on...
The energy contained
within the process gas!

206
There are no motors, no spark-plugs,
no batteries, no wind-up springs,
no counter-weights,
no mice running in a little round cage!
Just the high-pressure process gas
flowing through the expander wheel...

208
Expander Wheels; getting ��ٲ��ٱ��…

209
Expander Wheels; getting ��ٲ��ٱ��…

214
QP 17-4 Stainless steel wheel

215
How does an Expander Wheel
Extract Energy From the Gas
Stream?

217
Wheel Design
Wheel / IGV Mesh

219
Static Pressure Contour shows uniform Pressure drop
Expander Wheel

220
Pressure converted to velocity in Inlet Guide Vanes
Static
Pressure
Velocity

221
Low incidence
Expander Wheel

222
Removal of Angular Momentum:
High absolute velocity at impeller inlet
Low absolute velocity at impeller exit

223
Static Temperature -
Reduced as energy is removed
Refrigeration

226
Pressure energy is converted to
velocity energy, then into
kinetic, and finally into
rotational energy...

228
Selection of Expander Tip Speed
90%
92%
94%
96%
98%
100%
40 60 80 100 120 140
PERCENT
OF
OPTIMUM
EFFICIENCY
OPTIMUM EXPANDER TIP SPEED
0
500
1000
1500
2000
0 20 40 60 80 100 120 140
OPTIMUM
TIP
SPEED,
FT/SEC

229
Removal of Angular Momentum:
High absolute velocity at impeller inlet
Low absolute velocity at impeller exit

230
How does a Compressor Wheel
inject Energy back into the
Gas Stream?

234
Computational Fluid Dynamics (CFD)
Rotational energy on shaft spins the wheel...

235
The rotation of the wheel
increases the velocity of the gas…

237
The restrictions in the flow path,
represented by the blades of the wheel
and the Discharge Difffuser increase
the discharge pressure gradient...

239
Cool gas in, warm
gas out…

240
Warm, high pressure gas is
discharged…

242
The Gas Flow Path:
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

243
The Turboexpander is a
symmetrical, balanced machine…

244
The Shaft: 17-4 Stainless Steel

245
Aluminum bands have been applied
(“Flame Sprayed”) in the target areas
for the installed Bently-Nevada Series
3500 Vibration probes.

246
These Aluminum bands produce a
major reduction in the electrical run-
out noise signal which plagues 17-4
Stainless Steel.

247
A machined target for the speed probe

248
Counter-weight machining...

249
This shaft is designed to
operate well below the
First Bending Mode, as
well as below its own
Stressed Torsional
Resonant Frequency.

Rotordynamic mode shapes:
• The bending mode...

lateral
Bwd bending
conical
Natural Frequency Map :
• Shows natural frequencies, forcing frequencies
• (backward modes are not excited by unbalance)

Forced Response Analysis
• Shows rotor vibration amplitude from unbalance
• Does not analyze stability, only synchronous
response.
CRITICAL
SPEED
WELL
DAMPED

253
Attaching the wheels to the shaft

255
Shaft taper matches wheel bore

256
The “Stretch” Rod’s Job

258
Stretch Rod Installation
Correct Stretch Rod elongation is vital!
Follow all MTC Print Instructions

259
The Gas Flow Path:
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

260
SEALS:
Keeping high pressure out of the low
pressure areas, and cold process gas
away from hot oil and bearings...

262
Preserving Pressure Differentials Using Seals

263
1. Omni Seals (Pressure Act.)
2. O-rings, etc. (Contact)
3. Wheel Seals (Virtual/ Labyrinth)
4. Shaft Seals (Labyrinth)
5. Thermal barriers (Micarta)

264
Preserving Pressure Differentials
At Flange Interfaces

265
Cold Seals
(Omni-Seals)
52 kg 23 kg 56 kg

266
Omni-Seals:
Pressure activated
O-Rings:
Contact

267
Warm Seals
(O-Rings)
Cold Seals
(Omni-Seals)
52 kg 23 56
-98° C
+52° C

268
Warm area, O-rings
52 kg
-98° C
+50° C
-98° C
Cold Areas: Omni-seals

269
Preserving Pressure Differentials
At Rotating Joints:
Wheels and Shafts

270
1. Proximity Wheel Seals
(Non-contact, “Virtual” type)

271
The picture shows
streamlines of flow
particles which leak
through the tip
clearance gap. Design
of the MTC
turboexpander
minimizes this tip
clearance flow through
precision design of the
wheel and its follower.
Controlling this wheel-
to-follower gap carefully
greatly reduces energy
losses and flow
disturbances in the
downstream region.

272
2. Wheel Seals
(Labyrinth type)

275
The expander
wheel rotates
within the
confines of the
wheel seal. The
non-rotating
segment of the
labyrinth seal
prevents the
migration of high
pressure gas
behind the wheel

277
Labyrinth Seal “teeth”

282
Compressor Wheel and its seal...

283
Expander and Compressor wheels and
their respective wheel seals

286
Shaft seals are required to prevent cold,
high-pressure process gas from entering
the bearing housing.

287
Shaft Seals
A stainless steel ring on the
shaft, rotating within a fixed
Micarta Insert

289
Shaft Seal Insert: Micarta

291
Shaft Seals Ring: Stainless Steel

293
Shaft Seals
Alone, these are not 100%
effective...

294
Single Port Labyrinth Seal
Process gas
behind the
expander
wheel: 25 kg
@ -83° C
Bearing housing;
25 kg oil @
50° C

295
Add Seal Gas = 100% effective
No oil
migration into
Process gas
No cold
process gas
migration into
the hot oil

296
Preserving Temperature
Differentials

299
Cold process gas around
the expander wheel

300
Installation of a
Micarta Thermal
Barrier on the
Expander-end of
Rotating Assembly

302
Expander-side Thermal Barrier

303
Compressor-side Thermal Barrier

304
The Gas Flow Path:
3. Turbine Wheels
4. Shaft
5. Seals
6. Bearings

305
Turboexpander Bearings…
Supporting the rotating shaft and wheels

306
Bearings
• Lube Oil (Fluid Film) or Active Magnetic
• For these applications, fluid film bearings
were selected.

308
Turboexpanders: Bits and pieces...

�ݺ�ߣ

Section III _ Turbo Expense Components.ppt

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Section III _ Turbo Expense Components.ppt