relation between process and compressor reliability · 2019. 1. 8. · 4. pulsations on both...

RELATION BETWEEN PROCESS AND COMPRESSOR RELIABILITY

Xi’an, 21.06.2018Dr. Meinke

Meinke-Consulting for LDPE- and EVA-TechnologyGermany

FilenameDate

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

FilenameDate

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

FilenameDate

Relation between process and compressor reliability

General process flow sheet for LDPE – tubular design

Meinke-Consulting for LDPE-and EVA-Technology

FilenameDate


FilenameDate

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

FilenameDate


FilenameDate


Shutdown time in percentage for the first 6 month after first start-upPlant A Plant B

xxx

x

FilenameDate


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

FilenameDate


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

FilenameDate


J. Dowdell et all –

Evaluating CompressorReliability…Gas Machinery Conference 2011

FilenameDate


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

FilenameDate

Relation between process and compressor reliabilityGraph 1: Bönsel, H.; Luft, G.Chem. Ing. Techn. Vol. 67, (7), p. 862

Range of Polymerisation and Decomposition

FilenameDate


FilenameDate


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

FilenameDate


Peroxide solvents:

» ISO – Paraffine» N - Paraffine» White oil

» – condensation in Booster-Primary Compressor

Problems with the pumpability» Crystallisation» Using of higher Temperature

FilenameDate


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

FilenameDate


FilenameDate


Becker, M.„Thermischer Selbstzerfallvon verdichtetem Ethen“

Der Einfluß vonMetallverbindungenund Reaktorverunreinigungen

DissertationDarmstadt, 1999

FilenameDate


FilenameDate


DSC results - from differentProducts found in theHyper compressor

FilenameDate


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

FilenameDate


Meinke-Consulting for LDPE- and EVA-Technology

[email protected]

Germany

mailto:[email protected]

relation between process and compressor reliability · 2019. 1. 8. · 4. pulsations on both...

Documents