RELATION BETWEEN PROCESS AND COMPRESSOR RELIABILITY Xi’an, 21.06.2018 Dr. Meinke Meinke-Consulting for LDPE- and EVA-Technology Germany
RELATION BETWEEN PROCESS AND COMPRESSOR RELIABILITY
Xi’an, 21.06.2018Dr. Meinke
Meinke-Consulting for LDPE- and EVA-TechnologyGermany
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Content
General information about LDPE process
Raw materials
Fresh ethylene, no other comonomers
Other chemical components
– Lubrication oils
– Modifier
– Peroxides
During Radical polymerisation produced additional chemicals– What are the chemical components?
– Waxes, high molecular products
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Relation between process and compressor reliability High Pressure recycle gas system
– Main chemical components
– Others
From the Compressors
Booster-Primary Compressor
– Heat-exchanger, Water content
– strainer
Hyper Compressor
– Using of materials, which have contact with the process
Summary
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Relation between process and compressor reliability
General process flow sheet for LDPE – tubular design
Meinke-Consulting for LDPE-and EVA-Technology
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Relation between process and compressor reliability
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Relation between process and compressor reliabilityReciprocating machines
» – very high sophisticated system » - mainly to the high pressure» - over the years by experience it was improved» - monitoring system» - 2 out of 3 for reducing not related trips
Different approach by the clients» - preventive maintenance» - preventive shut down for cleaning» - or run up to the shut down, which is the most case
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Relation between process and compressor reliability
Shutdown time in percentage for the first 6 month after first start-upPlant A Plant B
xxx
x
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Materials
The valve body parts are made of standard material X12 stainless steel (AISI 416). Other proprietary materials are available on request.
•Premium grade X5 stainless steel (AISI 630)
•Hastelloy C276 for very corrosive environment
•High performance thermoplastic polymers (e.g. PEEK , PTFE )
Cu, Sn, Cr, Ni, Mo, V etc
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Statistical methods for failure analysis:» RAM factors constitute a strategic approach for integrating
reliability, availability and maintainability, by using methods, tools and engineering techniques ( such as Mean Time to Failure, Equipment down time and System Availability values
Technology:» Here – the process is very important, therefore the Licensor
has to give information to the designers» Raw Materials – not only Ethylene!
» Modifier» Lubrication oils» Different Peroxide
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J. Dowdell et all –
Evaluating CompressorReliability…Gas Machinery Conference 2011
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H.P. Bloch, J.J. Hoefner
“Reciprocating Compressors
Operation and Maintenance”
p. 157
Partwise and modified
Failure Reason or Action to be taken ProcessSuction valves only 1. Liquid carryover X
2. Intake pulsations
Discharge valves only 1. Discharge pulsations
2. Over lubrication X
Both suction and
discharge valves
1. Discharge failures due to broken pieces from
suction valves
2. Rust, scale, or foreign matter X
3. Insufficient or improper lubrication X
4. Pulsations on both suction and discharge
Rapid wear of suction
valves only
1. Incorrect or insufficient oil X
2. Cylinder jacket water temperature is lower than
incoming gas temperature
X
3. Gas may be wet and washing inlet lubrication from
valves
X
Seasonal failure of
valves
1. If failures occur in winter months only, liquid is the
probable cause – piping should be insulated,
knockout pots placed close to the cylinder
X
Valve seat gasket
failure
1. Gasket improperly installed and pinched
2. Valve loose due to improper tightening or being
knocked loose due to liquid slugs
X
Valve seat fractured Different reason, but valve loose due to liquid slugging X
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Relation between process and compressor reliabilityGraph 1: Bönsel, H.; Luft, G.Chem. Ing. Techn. Vol. 67, (7), p. 862
Range of Polymerisation and Decomposition
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Compressor lubrication oils
➢ Mineral oils➢ solvable from ethylene➢ normally needs additives for viscosity increasing (PIB)➢ some oils without additives, but 220 ct by 40°C
➢ Synthetic oils➢ Polyglycols
➢ unsolvable or very low amount from ethylene➢ hygroscopic – air and water from ambient condition➢ increase of polymerisation 1. stage hyper
compressor➢ deposit in the interstage cooler➢ Inhibitor request
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Peroxide solvents:
» ISO – Paraffine» N - Paraffine» White oil
» – condensation in Booster-Primary Compressor
Problems with the pumpability» Crystallisation» Using of higher Temperature
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Decomposition products of the using peroxidesPO1 PO2 PO3 PO4
tert. Butylalcohol x x x xAceton x x x xMethane x x x xEthane x x x xMethyl-tert. Butylether x x x xCO2 x x xPivalic acid xIsobutane xIsobutene x2-Ethylhexylhexanoic acid xHeptane xHeptene x3,5,5-Trimethylhexylhexanoic acid x2,4,4-Trimethylpentane x2,4,4-Trimethyl-1-pentene xtraces x x x x
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Relation between process and compressor reliability
Becker, M.„Thermischer Selbstzerfallvon verdichtetem Ethen“
Der Einfluß vonMetallverbindungenund Reaktorverunreinigungen
DissertationDarmstadt, 1999
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DSC results - from differentProducts found in theHyper compressor
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Summary
➢ Main topic is the high pressure and high temperatures➢ Different gas components➢ Radicals, not only oxygen➢ Slightly polymerisation under different condition compare to
reactor polymerisation➢ Different properties lead to special behaviour of the
polymers➢ Water content, hydroperoxide➢ Strainers – collect dirty particles, but after cleaning?➢ Heat exchangers in the compressor units
➢ All these points lead to different behaviour of the machine and reduce the reliability of the compressors
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Meinke-Consulting for LDPE- and EVA-Technology
Germany