Examen de Novedad

The   results   in   this   questionnaire   study   shows   that   almost   all   respondents   classify   the   factors   “equipment   failure”,   “failure   of   software   in   production   equipment”,   and   “media   error”  as  PD.  More  than  75  percent  also  classified  “human  error”,  “failure  of  peripheral”,   “planning   error”,   “subsequent   stop   in   output   flow”,   “shortage   of   staff”,   “speed   loss”,   and   “scrap   or   quality   problems”   as   PD,   but   factors   concerning   planned   activities   such   as   “preventive   maintenance”,   “cleaning”,   “work   meetings”   and   “pauses   or   breaks”   was   classified  as  PD  by  less  than  45  percent  of  the  respondents.  These  results  supports  the   conclusion  made  by  Ljungberg  (1998)  that  companies  are  in  general  primarily  focusing   on  downtime  losses,  and  especially  breakdowns,  and  that  planned  stoppages  are  instead   not  emphasized  enough.  In  relation  to  Ylipää’s  (2000)  model  for  sustainable  PDH,  it  is   naturally  the  breakdowns  that  result  in  the  biggest  visual  effect  in  terms  of  PD,  and  they   also  require  a  restart  of  the  system  after  they  have  been  resolved.  However,  some  of  the   less  emphasised  planned  activities  are  aimed  at  managing  the  important  PPD.  Such  PPD   could   be   dirt   and   dust   that   can   in   fact   cause   major   breakdowns   (Nakajima,   1998),   or   deficiencies  in  interventions  and  violations  that  has  an  ability  to  propagate  towards  a  PD   (Ylipää,  2000).    

Interesting  to  note  here  is  also  that  there  are  in  fact  differences  between  factors  that  are   rather   similar,   shown   through   that   “shortage  of  staff”   is   clearly   classified   as   a   PD   to   a   greater  extent  than  “work  meetings”  or  “pauses  or  breaks”.  In  addition,  it  is  important  to   note  that  none  of  the  factors  was  completely  rejected  as  PD,  as  even  the  factors  that  was   classified  and  registered  as  PD  to  the  lowest  degree,  i.e.  the  two  planned  activities  “work   meetings”  and  “pauses  or  breaks”,  had  an  affirmative  response  by  more  than  20  percent   of  the  respondents  

Moreover,  several  events  that  are  defined  as  TPM  losses  and  are  topics  for  continuous   improvements   and   waste   elimination   in   Lean   such   as   “set-­‐up/resetting”,  “tool  change”,   “adjustments”,  and  “time  for  changing/refilling  of  material”  was  classified  as  PD  by  less   than   half   of   the   respondents.   A   possible   explanation   to   why   these   factors   are   not   perceived   as   disturbances   could   be   that   they   are   not   directly   concerning   technical   failures   and   instead   seen   as   are   a   natural   part   of   the   production   process.   Their   contribution  to  decreased  availability  could  thus  easily  be  overlooked,  and  they  are  not   covered   by   the   fundamental   purpose   of   maintenance;   to   ensure   the   functioning   of   technical   equipment   (SIS,   2000).   However,   as   Jonsson   &   Lesshammar   (1999b)   points   out,   if   actions   that   are   a   part   of   the   production   process,   as   well   as   the   previously   discussed   planned   stoppages,   are   in   fact   registered   and   included   in   calculations   of   availability,  the  low  figures  would  create  an  incentive  for  decreasing  planned  downtime   by   more   effective   set-­‐ups   and   PM,   as   well   as   highlight   the   importance   of   plant-­‐wide   waste  elimination.  

Williamsen   (2013)   describes   how   approximately   600   leads   to   one   severe   accident.   By   analyzing   near   misses   and   conduct   appropriate   risk   assessment,   actions   to   prevent   accidents  can  be  taken.  In  this  survey,  “incidents/near  misses”,  was  classified  as  PD  by  69   percent  of  the  respondents,  and  registered  in  61  percent  of  the  companies.    

The   results   furthermore   indicate   that   18   out   of   the   21   factors   are   to   a   greater   extent   classified   by   the   respondents   as   PD   compared   to   what   is   registered   in   the   follow-­‐up   systems.  Detailed  data  collection  can  however  be  very  resource  demanding  and  result  in   unmotivated   personnel   (Jonsson   &   Lesshammar,   1998b).   Interestingly   enough,   the   3   factors   that   are   instead   to   a   greater   extent   registered   as   PD   are   in   fact   the   planned   activities   “preventive   maintenance”,   “cleaning”,   and   “work   meetings”,   although   the   two   latter  only  show  a  difference  of  6  and  3  absolute  percent  respectively.  It  is  probably  not   surprising   that   “preventive  maintenance”   displays   the   largest   difference   of   13   absolute   percent  as  it  is  widely  debated  within  literature  whether  PM  should  be  treated  as  a  PD   or   not   (see   for   example   Dal   et   al,   2000;   Ericsson,   1997;   Nakajima,   1998;   Jonsson   &   Lesshammar.  1998b;  Ljungberg,  1998).  Ylipää  (2000)  sees  PM  as  a  kind  of  paradox:  it   can  be  a  disruption  if  it  is  carried  out  during  production  even  though  it  is  also  aimed  at   avoiding  failures.  In  addition,  PM  can  in  fact  be  a  cause  of  failure  due  to  the  probability   of  introducing  failures  during  the  maintenance  activity.    

Moreover,   maintenance   concepts   like   TPM   and   Lean   Maintenance   stresses   the   importance  of  close  co-­‐operation  between  the  production  and  maintenance  department   (Nakajima,   1988;   Smith   &   Hawkins,   2004).   In   order   to   prevent   sub-­‐optimization   and   enable   collaboration   towards   achieving   high   reliability   through   prevention   and   elimination  of  disturbances,  a  shared  view  upon  the  PD  factors  is  a  necessity.  The  results   in  this  study  shows  that  production  and  maintenance  people  in  general  share  a  similar   view   on   the   subject,   where   the   average   of   which   factors   that   are   classified   as   PD   lies   within   63-­‐66   percent   for   the   three   groups   of   maintenance   and   production   personnel.   The  same  scenario  was  in  fact  also  found  in  the  previous  survey  as  described  in  Ylipää  et   al   (2007),   signifying   that   a   uniform   view   on   PD   factors   between   the   production   and   maintenance  department  has  been  prominent  in  Swedish  industry  for  many  years.      

The   results   that   are   based   on   discrete   versus   continuous   production   companies   show   that  the  groups  on  average  register  the  PD  factors  to  the  same  extent,  but  that  there  are   differences   concerning   specific   factors.   The   factors   “planning   error”,   “speed   loss”,   and   “cleaning”  is  more  frequently  registered  as  PD  in  continuous  production  companies.  The   first   two   could   correlate   to   the   high   consequences   of   rework   and   delays   due   to   large   batch  sizes  particularly  found  in  process  industry.  The  latter  connects  to  addressing  the   PPD,  or  the  “hidden  effects”  such  as  dirt,  dust  and  scratches  that  seem  insignificant  on   their  own  but  can  in  fact  cause  major  breakdowns  (Nakajima,  1988;  Ylipää,  2000).  On   the   contrary,   “work  meetings”,  “subsequent  stop  in  the  output  flow”   and   “incidents/near   misses”  is  to  a  greater  extent  registered  by  discrete  manufacturing  companies.    

In  the  data  that  is  based  on  company  size,  it  was  found  that  the  larger  the  company  is,   the   more   factors   are   both   classified   and   registered   as   PD.   The   larger   companies   are   especially   prone   to   register   the   factors   regarding   reduced   production   flow   in   form   of   “waiting  time  for  incoming  product  or  material”  and  “speed  loss”,  changes  in  production   in  form  of  “set-­‐up”,  “tool  change”,  and  “time  for  changing/refilling  of  material”,  as  well  as   downtime   due   to   “preventive   maintenance”.   The   larger   production   volume   naturally  

results   in   larger   economical   losses   from   disturbances,   and   there   are   likely   more   resources   to   be   found   for   investing   in   data   collection   equipment   compared   to   smaller   companies.   However,   the   opposite   is   found   for   “incidents/near   misses”   which   is   more   often  registered  as  a  PD  in  the  companies  with  less  than  100  employees.  Reporting  these   types  of  disturbances  does  not  require  any  particular  equipment  and  could  be  done  in  a   more  ad-­‐hoc  manner,  possibly  favoring  smaller  companies.