394
N. T. Mathew et al.
The main cost associated with online biofouling prevention is the direct cost of the
chemicals that are used for the removal of deposits from time to time (Hansen 2018;
Kronholm 2018; Bertilsson 2018). Then there are costs associated with the process
of mitigation based on the mitigation techniques used. Due to strict environmental
regulations, the storage, transportation and the proper disposal costs (treatment costs)
of the chemicals used in the mitigation process become a significant factor in the
overall costs associated with biofouling prevention (Hansen 2018). These costs are
directly dependant on the rate of biofouling in each case. As the biofouling rate is a
variable factor, it is difficult to provide an average range of values (Hansen 2018).
Biofouling causes the requirement of periodic offline cleaning of heat exchanger
surfaces (Müller-Steinhagen et al. 2011). The cleaning schedules vary widely and
depend mainly on the rate of biofouling which in turn depends on local characteristics like the plant operating conditions, physical and chemical properties of the
process fluid, heat exchanger material properties, and so on (Michels et al. 1979). For
example, some heat exchangers are cleaned daily, and some others weekly, monthly
or even annually (Michels et al. 1979). In offline cleaning, the heat exchangers
have to be removed from the operation and then disassembled (Hansen 2018). A
popular cleaning technique is the mechanical cleaning of heat exchanger surfaces
by employing manual labour (Hansen 2018; Chambon et al. 2017). The main cost
associated with offline mechanical cleaning is labour charges (Hansen 2018; Kronholm 2018; Bertilsson 2018; Kazi 2012). Offline cleaning is also performed using
chemicals (Kazi 2012). A major disadvantage with offline chemical cleaning is the
potential for corrosion damage due to undesired reactions between heat exchanger
surface and the chemical used (Kazi 2012). This would cause additional repair costs
(maintenance expenditure) or even an early replacement of the heat exchanger if the
corrosion effects are irreparable (Hansen 2018). There is also the direct cost of the
chemicals used in the cleaning process. Further, as mentioned earlier in this section,
the storage, transportation and proper disposal costs of the chemicals used in the
cleaning process, also contribute to the total costs in the offline chemical cleaning
process.
Offline biofouling cleaning techniques will cause significant equipment downtime
as the heat exchangers are removed from the current operation. Thus there are also
production losses associated with offline biofouling prevention. To prevent these
production losses, usually, a spare heat exchanger will be maintained. So, there
is also the additional cost of maintaining a spare heat exchanger. The pumps that
are used to supply seawater to the heat exchangers are also subjected to marine
biofouling. Thus biofouling will also result in additional pump maintenance costs or
pump cleaning costs for the end-user (6). Apart from that, the frequent cleaning of
heat exchangers and pumps to remove the deposits will cause wear and tear of heat
exchanger parts and pump parts. This will decrease the life expectancy of parts and
results in the increase of parts replacement costs and overall maintenance expenditure
for the end-user.
N. T. Mathew et al.
The main cost associated with online biofouling prevention is the direct cost of the
chemicals that are used for the removal of deposits from time to time (Hansen 2018;
Kronholm 2018; Bertilsson 2018). Then there are costs associated with the process
of mitigation based on the mitigation techniques used. Due to strict environmental
regulations, the storage, transportation and the proper disposal costs (treatment costs)
of the chemicals used in the mitigation process become a significant factor in the
overall costs associated with biofouling prevention (Hansen 2018). These costs are
directly dependant on the rate of biofouling in each case. As the biofouling rate is a
variable factor, it is difficult to provide an average range of values (Hansen 2018).
Biofouling causes the requirement of periodic offline cleaning of heat exchanger
surfaces (Müller-Steinhagen et al. 2011). The cleaning schedules vary widely and
depend mainly on the rate of biofouling which in turn depends on local characteristics like the plant operating conditions, physical and chemical properties of the
process fluid, heat exchanger material properties, and so on (Michels et al. 1979). For
example, some heat exchangers are cleaned daily, and some others weekly, monthly
or even annually (Michels et al. 1979). In offline cleaning, the heat exchangers
have to be removed from the operation and then disassembled (Hansen 2018). A
popular cleaning technique is the mechanical cleaning of heat exchanger surfaces
by employing manual labour (Hansen 2018; Chambon et al. 2017). The main cost
associated with offline mechanical cleaning is labour charges (Hansen 2018; Kronholm 2018; Bertilsson 2018; Kazi 2012). Offline cleaning is also performed using
chemicals (Kazi 2012). A major disadvantage with offline chemical cleaning is the
potential for corrosion damage due to undesired reactions between heat exchanger
surface and the chemical used (Kazi 2012). This would cause additional repair costs
(maintenance expenditure) or even an early replacement of the heat exchanger if the
corrosion effects are irreparable (Hansen 2018). There is also the direct cost of the
chemicals used in the cleaning process. Further, as mentioned earlier in this section,
the storage, transportation and proper disposal costs of the chemicals used in the
cleaning process, also contribute to the total costs in the offline chemical cleaning
process.
Offline biofouling cleaning techniques will cause significant equipment downtime
as the heat exchangers are removed from the current operation. Thus there are also
production losses associated with offline biofouling prevention. To prevent these
production losses, usually, a spare heat exchanger will be maintained. So, there
is also the additional cost of maintaining a spare heat exchanger. The pumps that
are used to supply seawater to the heat exchangers are also subjected to marine
biofouling. Thus biofouling will also result in additional pump maintenance costs or
pump cleaning costs for the end-user (6). Apart from that, the frequent cleaning of
heat exchangers and pumps to remove the deposits will cause wear and tear of heat
exchanger parts and pump parts. This will decrease the life expectancy of parts and
results in the increase of parts replacement costs and overall maintenance expenditure
for the end-user.