Competence at work for service and innovation

Take a look on some CST Success Stories

OFF-SHORE GAS LIFT COMPRESSOR

OFF-SHORE GAS LIFT COMPRESSOR

Minor branches failure


Country :
Mediterranean sea
Application :
Floating production storage and offloading (FPSO)
Compressor Type :
Reciprocating compressor – 3 stg.
Service :
Gas lift compressor
Power :
1050 kW
Pressure :
120 bara

PROBLEM

Sudden welding ruptures on minor branches

  • high vibrations since the first start-up
  • skid design failed to consider alternating forces
  • poor support design

SOLUTION

  • acoustical study revealed the need for:
    • restriction orifices
    • new support installation

Vibrations reduced below the SWRI danger value
No failures occurred after modifications

HIGH PIPING VIBRATIONS

HIGH PIPING VIBRATIONS


Country :
Italy
Compressor Type :
n°2 Reciprocating compressors – 3 stg.
Service :
C2H2 feed gas
Power :
355 kW
Pressure :
29 bara

PROBLEM

Unexpected trips for gas leakage

  • welding ruptures of the inlet nozzle on piping
  • acoustic resonance and poor piping clamping

SOLUTION

  • installation of restriction orifices
  • stiffening of the existing piping structure
  • optimization of clamps disposition

Unscheduled trips avoided

SHORT PISTON RINGS LIFE

SHORT PISTON RINGS LIFE


Country :
Italy
Application :
Paper mill
Compressor Type :
Reciprocating compressor – 1 stg.
Service :
30 MW Gas turbine fuel supply
Power :
500 kW
Pressure :
37 bara

PROBLEM

Forced maintenance every 3 months due to fast wearing of PTFE piston sealing elements

SOLUTION

  • high performance PEEK material suggested
  • scheduled temperature monitoring program

Compressor reached 8000 hours of correct operation

REFINERY COMPRESSOR SEALS

REFINERY COMPRESSOR SEALS

Quick wear


Country :
Italy
Application :
Refinery
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
Penex process compressor
Power :
90 kW
Pressure :
80 bara

PROBLEM

Rod packing elements life was <1000 hours

  • recurrent rod scratching
  • chromium on the rod surface

SOLUTION

  • roughening treatment to increase the transfer film capacity
  • suggested high performance PEEK material

Piston rod packing life exceeding 8000 hours

LDPE HIGH PRESSURE COOLER

LDPE HIGH PRESSURE COOLER

Repeated piping ruptures


Country :
Italy
Application :
Low Density Polyethylene Plant
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
LDPE process secondary compressor
Power :
5800 kW
Pressure :
3200 bara

PROBLEM

Ruptures on cooler and HP piping (every 2-3 months)

  • high vibrations (up to 250 mm/s rms)
  • modifications to be performed in one week

SOLUTION

  • FEM study of the mechanical system to define modifications to existing supports and structure
  • foundations reinforced through grouting
  • follow-up survey to confirm root cause analysis and resolution

Vibrations reduced below SWRI danger value

LDPE COMPRESSOR

LDPE COMPRESSOR

High Piping Vibration


Country :
Taiwan
Application :
Low Density Polyethylene Plant
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
LDPE process secondary compressor
Power :
7400 kW
Pressure :
2500 bara

PROBLEM

High vibrations since first start-up

  • vibrations above SWRI danger curve in some points
  • acoustic analysis verified through strain gage measurements
  • both acoustic and mechanical resonances found

SOLUTION

  • inserted restriction orifices in key points
  • modified supporting structure to shift MNF
  • inserted fabric pads between clamps and pipes

Vibrations reduced below SWRI danger value

FROM GAS ENGINE TO ELECTRIC MOTOR

FROM GAS ENGINE TO ELECTRIC MOTOR


Country :
Canada
Application :
Boil Off Gas
Compressor Type :
Reciprocating compressor – 4 stg.
Service :
Natural gas
Power :
450 kW
Pressure :
45 bara

SCOPE

User wanted to change driver type from gas engine to electric motor

SOLUTION

  • Design of the new train arrangement with:
    • Brake and Starting torque Analysis
    • Torsional Analysis
    • New coupling and flywheel selection
  • On site installation and commissioning through Blackstone (CST Canadian partner)

Compressor in operation with full customer satisfaction

SOUR GAS COMPRESSOR

SOUR GAS COMPRESSOR

Too short Seal Life


Country :
Kuwait
Application :
Sour gas
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
Vapour recovery
Power :
835 kW
Pressure :
6 bara

PROBLEM

Extremely fast rings consumption

  • rings provided by OEM failed after less than 100 h
  • major damages to pistons and liners due to inadequate protection system
  • alternate material from OEM’s competitor lasted for 1500 h

SOLUTION

  • new lubrication system
  • improved cylinder cooling system
  • stronger material (PEEK) with optimized dimensions
  • new piston desing

POLYPROPILENE SCREW COMPRESSOR

POLYPROPILENE SCREW COMPRESSOR

Piping support failure


Country :
Italy
Application :
Polypropylene
Compressor Type :
Screw compressor
Service :
Polypropylene plant
Power :
50 kW
Pressure :
30 bara

PROBLEM

Frequent piping support failure

  • inadequate type and position of supports
  • piping weight applied on compressor flange
  • wood layer between steel supports

SOLUTION

  • FEM analysis to find better supports design
  • new “spring type” supports
  • new antifriction damping layer between steel supports

No more piping support failures

STEEL MILL IGCC

STEEL MILL IGCC

Start-up Failure


Country :
Latvia
Application :
Steel mill
Compressor Type :
Integrally geared Centrifugal Compressor
Service :
Furnace air compressor
Power :
4000 kW
Pressure :
50 bara

PROBLEM

Impeller destroyed twice at first Start-up

SOLUTION

  • RCA with rotor-dynamic and metallurgical analyses revealed wrong clearance on bearings
  • New bearing arrangement defined and installed

Compressor started up successfully and running correctly

POWER GENERATION STEAM TURBINE

POWER GENERATION STEAM TURBINE

Start-up Failure


Country :
U.A.E.
Compressor Type :
N. 2 Steam Turbines
Service :
Power generation
Power :
10 MW

PROBLEM

Turbine trip during start-up on both units. Severe damage to the rotors due to rubbing against the stator

SOLUTION

  • RCA indicated casing bow (non uniform expansion), resulting from an insufficient thermal insulation of the casing
  • Re-calculation of the thickness of the thermal insulation
  • Suggested new procedure for turbine warm-up
  • Revised seal radial clearance

Turbine started up and running correctly

POWER GENERATION GAS TURBINE

POWER GENERATION GAS TURBINE

Start-up Failure


Country :
Egypt
Application :
Natural gas extraction plant
Compressor Type :
N. 2 Two-shaft Heavy-duty Gas Turbines
Service :
Power generation
Power :
5 MW

PROBLEM

After a maintenance stop, Turbine could not start due to high vibrations (both low and high frequency)

SOLUTION

  • RCA results: not appropriate bearing clearances and oil inlet design
  • Bearings replaced with 4-lobe types (low-frequency vibration)
  • Trim balancing (for synchronous vibration)

Gas Turbine started up and running correctly

GAS TURBINE/CENTRIFUGAL COMPRESSOR

GAS TURBINE/CENTRIFUGAL COMPRESSOR

Cabinet Explosion


Country :
Algeria
Application :
Gas extraction plant
Compressor Type :
Heavy-duty Gas Turbine
Service :
Centrifugal Compressor drive
Power :
10 MW

PROBLEM

Explosion of the Gas Turbine cabinet

SOLUTION

  • RCA indicated explosion due to a failure of lube oil trap level control loop and vent line clogged
  • Lube oil vent system modified
  • Lube oil tank fill-up procedure established

Event occurrence eliminated

OLD CENTRIFUGAL COMPRESSOR

OLD CENTRIFUGAL COMPRESSOR

Instrumentation Upgrade


Country :
Italy
Application :
Industrial Gas Production
Compressor Type :
Centrifugal Compressor manufactured in 1961
Service :
ASU Main Air Compressor
Power :
5000 kW
Pressure :
6 bara

PROBLEM

OEM no longer available. User wanted to extend the operating life of this old unit by upgrading machine monitoring

SOLUTION

  • Design and implementation of mechanical modifications to house new sensors
  • Supply and installation of a new vibration monitoring cabinet, linked to the plant DCS

Shaft vibration and thrust position now monitored

CENTRIFUGAL COMPRESSOR

CENTRIFUGAL COMPRESSOR

Performance Recovery


Country :
Italy
Application :
Sulfuric Acid Production
Compressor Type :
Overhung Centrifugal Compressor
Service :
Combustion Air
Power :
2.6 MW

PROBLEM

Performance loss (efficiency and flow rate) caused by  increased clearance between impeller and casing due to corrosion

SOLUTION

  • Labyrinth seal insertion
  • Clearance reduction

+6% Volume Flow rate,   +1% efficiency

NITRIC ACID CENTRIFUGAL COMPRESSOR

NITRIC ACID CENTRIFUGAL COMPRESSOR

Casing Revamping


Country :
Mexico
Application :
Nitric Acid Production Plant
Compressor Type :
Horizontally Split Centrifugal Compressor
Service :
N2 + NOx compression
Pressure :
11.5 bara

PROBLEM

Gas leakage between upper and lower semi-casings

SOLUTION

  • RCA indicated a reduction of contact pressure due to corrosion and wrong maintenance
  • Static FEA to determine contact pressure distribution
  • Increased stud bolts diameter, added new tie rod

Correct and uniform contact pressure restored; No more gas leakage

CENTRIFUGAL COMPRESSOR

CENTRIFUGAL COMPRESSOR

Upgrading Study


Country :
Russia
Application :
Urea Production Plant
Compressor Type :
Centrifugal Compressors train
Service :
CO2 compressor
Pressure :
220 bara

PROBLEM

Performance improvement through upgrading of an old unit which has at present:

  • High vibration levels upon certain process conditions
  • Missed production targets due to high absorbed power
  • High bearing temperature on gearbox

SOLUTION

  • Site survey, gathering data from personnel & DCS
  • Action list including upgrade on seals, balancing drum and gearbox bearings
  • Study possible efficiency increase to improve plant productivity

Work in progress…

CENTRIFUGAL COMPRESSOR

CENTRIFUGAL COMPRESSOR

Temporary Strainer Clogging


Country :
Italy
Application :
Refinery
Compressor Type :
Centrifugal compressor
Service :
Mild Hydrocracking make-up compressor
Power :
900 kW
Pressure :
90 bara

PROBLEM

Δp on a temporary strainer quickly rose to ~1.3 bar

  • Customer could not stop production before scheduled maintenance

SOLUTION

  • Finite element analysis and a buckling analysis
  • Maximum sustainable pressure drop ~ 4 bar

Maintenance executed after one year, as originally planned

LDPE REACTOR

LDPE REACTOR

Stirrer Bearing Failure


Country :
Italy
Application :
Low Density Polyethylene Plant
Compressor Type :
Autoclave reactor

PROBLEM

Catastrophic failure of stirrer supporting bearing caused heavy damage to the reactor wall

SOLUTION

  • RCA revealed too little elasticity in bearing clamping system
  • New clamping system developed

System implemented by user succesfully

CYLINDERS LUBRICATION

CYLINDERS LUBRICATION

System Upgrade


Country :
Italy
Application :
Refinery plant
Compressor Type :
n°5 Reciprocating compressor – 3 stg.
Service :
Hydrogen make up
Power :
4200 kW
Pressure :
~200 bara

PROBLEM

Old PtP lubrication system with recurrent issues

  • Faulty sight glasses
  • Unstable lubrication (dry run occurred)
  • High oil consumption

SOLUTION

  • 5 units retrofitted with CST PLS-100 (full redundant + continuous monitoring)
  • Reduced oil consumption recovered the investment in less than one year

Unexpected shutdown prevented
Return on Investment: < 1 year

RECIPROCATING COMPRESSOR

RECIPROCATING COMPRESSOR

Catastrophic Valve Failure


Country :
France
Application :
LNG Terminal
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
Methane compression
Power :
1133 kW
Pressure :
82.5 bara

PROBLEM

Unexpected compressor shutdown

  • Cross-head pin failure
  • Crank-mechanism lubrication oil polluted by metal particles
  • Delivery valves failures (cracked guard)

SOLUTION

Root Cause Analysis based on:

  • Visual and metallographic inspection
  • Stress and fatigue simulation by means of FEM Analysis assessed sudden overpressure caused by liquid slug ingestion

Piping routing and draining procedures modified to prevent further failures

KNOCKING SOUND FROM  A CYLINDER

KNOCKING SOUND FROM A CYLINDER


Country :
Italy
Application :
Landfill biogas generation
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
Biogas compression
Power :
450 kW
Pressure :
16 bara

PROBLEM

Knocking sound from cylinder head

  • Piston-to-rod connection found loosened

SOLUTION

  • Trend analysis to highlight possible overpressures
  • Visual inspection and measurements revealed an “out of tolerance” dimension of rod to piston connection
  • FEM Analysis carried out on mating areas confirmed a tightening fault during assembly

Dimensional checks and new tightening procedure
implemented to prevent further problems

HYPERCOMPRESSOR

HYPERCOMPRESSOR

Foundation Refurbishment


Country :
Louisiana USA
Application :
Low density Poly-ethylene production
Compressor Type :
IR Reciprocating compressor – 2 stg.
Service :
Hypercompressor
Power :
10 MW
Pressure :
2345 bara

PROBLEM

Foundation corruption

  • Cracks on the foundation walls
  • Inefficient stiffeners
  • High vibrations

SOLUTION

Complete turn-key project

  1. Excitation reduction adopting a different crankshaft design. Engineering completed with:
    • Dynamic analysis for unbalanced forces and couples
    • Acoustic analysis for pulsations
  2. Foundation re-engineered
  3. Old Foundation demolition and refurbishment

New foundation solution successfully implemented

HYPERCOMPRESSOR

HYPERCOMPRESSOR

Fretting Issues On Conrod Bearings


Country :
Louisiana USA
Application :
Poly-Ethylene production
Compressor Type :
Clark Reciprocating compressor
Service :
Ethylene make up
Power :
3 MW
Pressure :
2000 bara

SCOPE

  • Fretting phenomena on the back side of connecting rod bearings and conrod body
  • Big end casted aluminum bearing failure

SOLUTION

  • RCA to assess the cause of the failure and confirm the fretting phenomena by FEM simulations
  • Big end bearing, studs and body reverse engineering and redesign to optimize contact pressure and avoid relative movement between bearing and big end

FLOW INDUCED VIBRATIONS IN A GAS COMPRESSION PLANT

FLOW INDUCED VIBRATIONS IN A GAS COMPRESSION PLANT


Country :
Libia
Application :
Gas compression plant
Compressor Type :
Centrifugal compressor
Service :
Gas booster
Power :
20 MW
Pressure :
75 bara

SCOPE

  • Determine the source of piping vibrations
  • Apply effective modifications to reduce them below the recommended values

SOLUTION

  • Identification of a source of flow induced vibrations in a Tee junction
  • Flow modelling to characterize the source of vibrations and the pulsation phenomenon
  • Piping FEM modelling to determine mechanical natural frequencies
  • Multiple solutions identified to find the best compromise between vibration reduction and cost of modifications

SCREW COMPRESSOR

SCREW COMPRESSOR

High Pulsation Induced Vibrations


Country :
Kuwait / 2020
Application :
Nitrogen generator
Compressor Type :
Screw compressor
Service :
Air compression
Power :
580 kW
Pressure :
11 bara

SCOPE

  • Determine the source of 1st stage side vibrations, causing continuous alarms and machine blocks
  • Apply effective modifications to reduce them below the recommended values

SOLUTION

  • On site vibration detection
  • Data analysis found a dominant frequency that characterizes the totality of plant components - 1st stage Pocket Pass Frequency
  • Countermeasures design focusing on the pipe affected by resonance phenomena
  • Torsional analysis of the screw compressor train

EFFICIENCY IMPROVEMENT ON RECIPROCATING COMPRESSOR

EFFICIENCY IMPROVEMENT ON RECIPROCATING COMPRESSOR


Country :
Switzerland
Application :
Pharmaceutical and Biotech Industry
Compressor Type :
Reciprocating compressor – 4 stg.
Service :
Oil free CO2 compression
Power :
220 kW
Pressure :
~63 bara

PROBLEM

  • The compressor ran at 80-90% capacity most of the time
  • The exceeding capacity is recycled to the compressor inlet and compression energy is wasted

SOLUTION

  • “Flux-to-Flow” system designed and installed on 1st stage
  • Compressor thermodynamic and torsional behaviour verified for reliable and safe operation

~20 KEur/Year saved (15%)

 RECIPROCATING COMPRESSOR

RECIPROCATING COMPRESSOR

High Vibration Diagnostics


Country :
Tunisia / 2014
Application :
Gas extraction plant
Compressor Type :
Reciprocating compressor – 1 stg.
Service :
Gas compression LP
Power :
700 kW
Pressure :
30 bara

PROBLEM

Recurrent high vibration on a variable speed compressor

SOLUTION

  • RCA revealed correlation between rotation speed and MNF
  • Speed variation limited to safe range

Potential failures avoided

RECIPROCATING COMPRESSOR

RECIPROCATING COMPRESSOR

Diagnostics leads to Compressor Revamp


Country :
Italy
Application :
Petrochemical plant
Compressor Type :
Reciprocating compressor – 2 stg.
Service :
HC Polymerization
Power :
1800 kW
Pressure :
40 bara

PROBLEM

Two cylinder-distance piece tie-rods found broken

  • High cylinder vibrations
  • High pin load caused by suction pressure higher than design

SOLUTION

  • 2nd stage cylinder bore diameter modified
  • High-resistance rolled thread tie-rods
  • Volume bottles size increased

Predictive maintenance leading to compressor improvement

DIAGNOSTICS PREVENTING COUPLING MAJOR FAILURE

DIAGNOSTICS PREVENTING COUPLING MAJOR FAILURE


Country :
Tunisia
Application :
Gas extraction plant
Compressor Type :
Reciprocating compressor – 3 stg.
Service :
Gas reinjection
Power :
1600 kW
Pressure :
150 bara

PROBLEM

Increasing vibration trend suggested machine stop and inspection: resilient element found heavily damaged

SOLUTION

Major compressor failure prevented by substituting resilient element

Unscheduled shut-down avoided