lesson learn from petrochemical plant rev1

8/10/2019 Lesson Learn From Petrochemical Plant Rev1

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M&R Day

Iwan - Abadi


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One of the biggest HDPE Plant in Indonesia located at Cilegon, Banten Indonesiaexperienced failures on two extruder screw shafts of 1-X-840 (extruder shaft #1) and

2-X-840 (extruder shaft #2).
https://www.youtube.com/watch?v=WaB-dsB1Kfk


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Extruder Process Design Data1. Feed Materials : HDPE or LLDPE2. Feed Matl Melt Index: 0.1 to 50 (LLDPE 0.1 30; HDPE 5 to 50)3. Feed Matl Water content: less than 700 ppm4. Process Temperature:


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Extruder Zone

Broken Area atKneading zone


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Fracturesurface

2

Multiple crack origins

Initiation 1 created astable crack

Initiation 2 did notcreate a stable crack

2


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Extruder screw shaft #1 Extruder screw shaft #2


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Extruder Operational Data and Failure History1. Installation date : 19912. Both extruder were used to extrude Polyethylene with similar operational data history.3. Processing temp. : Below 240 C4. 1991 1998 : 15 - 16 ton/hour operating capacity5. 1998 : Modification on kneading screw

6. 1998

2002 : Low operating capacity7. 2003 2006 : Idle, not operated8. 2006 current : 21 ton/hour operating capacity9. 2008 2009 : Barrel temp. inverter was in troubled10. 2009 : Indication of vibration increased, Gland packing leakage11. 2009 : Shaft gear pump coupling was broken (extruder #1)12. 2010 : The temperature inverter problem was solved.

13. 2010 : Trial of HMW-PE on both extruder, very low MFI (0.02 up to 0.05)14. 9 April 2010 : Extruder shaft #1 was failed, Broken shafts were on the right side of the

extruder (from motor view), After replacement, the gear box was broken15. 2010 : The original screw was re-installed after the extruder shaft #1 was broken.16. 9 Mei 2011 : Extruder shaft #2 was failed, Broken shafts were on the right side of the

extruder (from motor view)


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The failure point of the two extruder shaft #1 and #2 was locatedbefore kneading/mixing zone, where the high pressure ofpolyethylene melt was built up and high bending moment on shaftwas exist.

Visual examination and SEM data strongly indicates a strong

contribution of fatigue bending moment failure with largepropagation area and minor contribution of torsion fatigue.

Crack initiation sites on both extruder shafts have multiple crackorigins, although only one crack origin developed a stable crack andpropagated through shaft cross section and developed largepropagation area.

Large propagation area indicated the applied stress after crackinitiation was considerably low. The crack initiation was likelyoccurred when the loading was not distributed evenly to allhexagonal surfaces and during overload period .


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Physical Cause : The concentrated load was only possible when the fitness between shaft

surface to inner hexagonal surface of the screw is not zero clearance .Non zero clearance will cause inhomogeneity contact between both surfaces;the torsion moment has not been transmitted homogeneously to allhexagonal surfaces but only been transmitted through the hexagonal shaft

corner.Human Cause : The root cause of 1-X-840 and 2-X-840 extruder shaft failure was due to

fatigue failure initiated by domination of concentrated load on hexagonal shaftsurface during overload period .

Design Machine Capacity 17.4 ton/hHistorical, Machine in could be running at 21 ton/h

Start and stop operation mode of this machine might contributed to increasefatigue cycle.

Latent Cause : Inadequate procedure that allows operation of the machine above design

capacity & excessive start-stop mode.


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Thank You

lesson learn from petrochemical plant rev1

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