Download - 1.6b Compressors Slides
-
8/13/2019 1.6b Compressors Slides
1/34
Where We Go Wrong -
With Compressors
Dick Hawrelak
Presented to ES-317y in 1999 at UWO
-
8/13/2019 1.6b Compressors Slides
2/34
Introduction
5% of large property damagelosses are caused by failures inpumps and compressors.
When a major failure takes place,the average trended Loss is$19.2MM.
C3H6 compressor,driver & spares
in a world scale ethylene plantcosts $17MM purchased.
-
8/13/2019 1.6b Compressors Slides
3/34
Compressors Costs FS LHC#1
Cost Summary By Elliott RAHEstimated
CG K-201/K-321 $17,239,800 $17,472,331
Propylene K-601 $8,667,000$6,674,797
Ethylene K-651 $6,014,000$5,478,011
$31,920,800
$29,625,139
-
8/13/2019 1.6b Compressors Slides
4/34
Compressor Problems
The following are some of the
problems found in compressordesign and operation.
The compressor train includes;compressors, drivers, KO Pots,
exchangers and storage vessels.
-
8/13/2019 1.6b Compressors Slides
5/34
ComplexComp
SystemsCan BeFound
In AnEthylenePlant
-
8/13/2019 1.6b Compressors Slides
6/34
Mass Balance Problems
Process start-up, shut down orupset conditions not well defined.
Refrigerant mass balances.
Steam driver mass balances
Hot gas turbine mass balance.
Designers did not consider allproblems associated with recycle
for turn-down or false-loadconditions.
-
8/13/2019 1.6b Compressors Slides
7/34
Typical Steam Balance
-
8/13/2019 1.6b Compressors Slides
8/34
Pressure / Temperature
Operating points not well located.
Poor data from the field. Poor data is useless for
determining compressor
performance.
-
8/13/2019 1.6b Compressors Slides
9/34
Interstage Conditions
If low stage pressure drops are
higher than designed, final stagedischarge pressure may not beachieved.
See NCOMP example fordemonstration.
-
8/13/2019 1.6b Compressors Slides
10/34
NCOMP Results
-
8/13/2019 1.6b Compressors Slides
11/34
Discharge Conditions
Discharge temperatures higher
than allowable limits. Indicateslower efficiency and pendingtrouble.
See NCOMP example fordemonstration.
-
8/13/2019 1.6b Compressors Slides
12/34
Composition
Actual plant feed stock differs fromdesign feed stock.
Condensate compositions differfrom one oil field to another.
Design for 100% ethane cracking
but operate with mixed HC feeds.
-
8/13/2019 1.6b Compressors Slides
13/34
Physical Properties
Vendor and customer did not
agree on physical properties. Non-ideal vapor / liquid systems.
VCM plant operates at 50% ofcapacity.
-
8/13/2019 1.6b Compressors Slides
14/34
Vendor Offering
Vendors often quote unusuallyhigh compressor efficiency to tryand win the contract.
Many customers are gullibleenough to swallow the offering.
Difficult to pin vendor down on finalperformance. Too many degrees ofwiggle freedom.
-
8/13/2019 1.6b Compressors Slides
15/34
Follow-up
Customer fails to up-date materialand energy balance after vendorshop tests confirm projectedadiabatic compression efficiency.
-
8/13/2019 1.6b Compressors Slides
16/34
Prototypes
Customer accepts vendorprototype offering with blind faith.
Ford Edsel example.
-
8/13/2019 1.6b Compressors Slides
17/34
Spare Parts
Customer fails to request a sparerotor. 6 months to fabricate.
Customer orders a spare rotor butstores it incorrectly.
Rotor must be balanced in a coffin,turned regularly and the coffinnitrogen purged under positivepressure.
-
8/13/2019 1.6b Compressors Slides
18/34
Shop Tests
Customer goes the cheap routeand specifies only a one point
shop test.
Customer fails to witnessconstruction and final shop test.
-
8/13/2019 1.6b Compressors Slides
19/34
Fabrication
Customer accepts vendor without
shop visit. Poor fabrication techniques.
-
8/13/2019 1.6b Compressors Slides
20/34
Interstage Seals
Poor seal selection.
Mechanical seal. Hot gas seal.
Water seal.
-
8/13/2019 1.6b Compressors Slides
21/34
Vibrations
Vendor fails to identify all criticalspeeds.
Vendor makes a poor vibrationcorrections.
Poor vibration monitors and trip
system.
-
8/13/2019 1.6b Compressors Slides
22/34
Bearings
Poor fabrication.
Poor alignment. Poor maintenance.
-
8/13/2019 1.6b Compressors Slides
23/34
Anti-surge Control
High vibrations on approaching
stonewall point. Anti-surge control does not
respond as required.
-
8/13/2019 1.6b Compressors Slides
24/34
Shut-down Trip Systems
Cheap trip systems do not identifywhat tripped the compressor by a
first out diagnostics trip system. Poor trip systems do not permit
good diagnostics following a
compressor trip.
-
8/13/2019 1.6b Compressors Slides
25/34
Lube Oil Systems
Insufficient lube oil reservoircapacity for roll-down.
Lube oil lines not cleaned beforestart-up.
Poor lube oil supply.
Non union lube oil systemreassembled by local union.
-
8/13/2019 1.6b Compressors Slides
26/34
-
8/13/2019 1.6b Compressors Slides
27/34
Compressor Gears
Poor gear design.
High noise.
Poor alignment on maintenance. Poor lubrication.
-
8/13/2019 1.6b Compressors Slides
28/34
Compressor
Configuration Over-hung lines on compressors
are poor for maintenance.
Bottom-hung lines on compressorsare good for maintenance butrequire taller compressor building.
-
8/13/2019 1.6b Compressors Slides
29/34
Typical Configuration
-
8/13/2019 1.6b Compressors Slides
30/34
3 Case C3H6 Compressor
-
8/13/2019 1.6b Compressors Slides
31/34
Foundations
Poor soil bearing tests fail todisclose soil loading problems.
Compressor experiences settling. Alignment suffers and compressor
wrecks.
One project manager doubles all
foundation specifications to be onthe safe side.
-
8/13/2019 1.6b Compressors Slides
32/34
Inlet Piping
Inlet lines too small.
Inlet vanes do not receive design
flow due to poor flow distribution.
-
8/13/2019 1.6b Compressors Slides
33/34
Driver Selection
Electrical motor.
Diesel motor.
Gas turbines. Steam turbines.
Drivers require as much attention
as the compressor.
P ibl E
-
8/13/2019 1.6b Compressors Slides
34/34
Possible ExamQuestions
In a multi-stage compressor, if the low stagepressure drops are higher than designed, how
will the final final discharge pressure beaffected?
What is the problem of running a compressorwith a very high discharge temperature?
Why do we install vibration monitors and highvibration trips on centrifugal compressors?
***