When to replace your old motor control
centre
A motor control centre (MCC)
sits at the heart of an industrial plant. If well maintained, an MCC can last for
decades, but despite their sturdiness, even the most reliable MCCs have to be
retired at some point. Here, Pat McLaughlin, operations director of Boulting Group, explains the early
warning signs that an MCC needs replacing.
There are
several reasons for replacing an MCC, but the most common ones include
obsolescence, incompatibility with new legislation or the condition of the MCC
deteriorating. Technological advancements that allow the design of intelligent,
more efficient MCCs are another reason why companies sometimes opt for an
upgrade.
Many engineers
will wait until an MCC breaks down completely before commissioning a
replacement, but best practice dictates that through proactive maintenance and
regular checks, plant managers and maintenance engineers can identify the early
warning signs of a failure and better plan for the upgrade.
The potential
defects discussed below are what maintenance engineers should look for when
performing regular MCC checks. These audits should take place at least twice a
year and log faults so that the information can be used retrospectively to
better understand the condition of an MCC and predict potential risks.
Mechanical defects
A motor control
centre has several electro mechanical components that are particularly susceptible
to failure. These include the filters and fans, which need to be cleaned and
checked regularly because they provide adequate air ventilation within the MCC.
Poor ventilation can easily lead to overheating and the failure of critical
components.
Visual checks
should also cover whether the relevant warning labels are in place before
performing maintenance on an MCC, so that maintenance engineers are not put in
any danger during these audits.
Electrical faults
Maintenance
engineers can employ several methods to check electrical equipment. These vary
from simple visual checks that identify discoloured or burned out components,
to more complex investigations using an infrared camera to analyse electrical
equipment or bus bars and to highlight hot spots.
Engineers should
also pay particular attention to the cables and connectors of the MCC, as these
tend to degrade relatively quickly. Checks should also cover the running
currents and shielding of the MCC, to ensure employees cannot access live
components.
Health and safety
MCCs,
particularly ones that have been in operation for a long time, can become
health and safety hazards. Engineers were not as safety conscious back in the 80s
or 90s as they are today, so there is a good chance that any MCC that is a
couple of decades old could be revisited to ensure it doesn’t pose any health
and safety risks.
For example,
Boulting Group engineers recently helped a utilities company replace an MCC
that had been in operation for 43 years. Because of its age, the condition of
the MCC had deteriorated resulting in some component failure and potentially
live and, possibly dangerous to maintenance staff.
Regulatory compliance
The well-known
BS EN 61439-2 standard, which came into play on November 1, 2014, states that
the enclosure of an MCC should fit the “type and degree of protection suitable
for the intended application.” Best practice dictates that the enclosure should
provide protection for equipment against external influences from any
accessible direction and against direct contact, meaning that an ingress
protection of at least IP2X is required. Older MCCs may not have been built to
this standard, so it’s important to check that your equipment is compatible
with the latest regulations.
Another critical design verification
introduced by BS EN 61439-2 refers to the temperature rise limits of motor
control centres. Temperature rise is essential to the reliability and long
service capability of an MCC, because excessive temperatures result in the
premature ageing and failure of components and insulation. The introduction of
the new standard means that manufacturers must verify that each circuit within
the assembly can individually carry its rated current.
If you are
considering purchasing a new MCC, it’s important to make sure that it complies
with BS EN 61439. This is the responsibility of the MCC manufacturer, but the
client should also be aware of the requirements and the benefits of the new
standard.
Environmental factors
Because MCCs
often operate in demanding environments, there are certain environmental
factors that can affect the equipment and shorten its operational life. Such
factors include dust, moisture and steam, all of which can be very corrosive
and damage bus bars or electrical equipment. Similarly, because MCCs are often
tucked away in the depths of a building, there is the danger of vermin damaging
cables.
Maintenance
engineers need to be aware of these potentially harmful environmental forces
and perform the relevant checks periodically. Although some of these variables —
such as moisture or dust — can’t be eliminated, they can be mitigated and engineers
can monitor sensitive components more closely.
New tech
More often than
ever, companies are deciding to change or upgrade their MCCs to take advantage
of the benefits that new technologies offer. One common upgrade involves replacing
conventional starters with variable speed drives (VSDs) and adapting the MCC to
accommodate this change. Since a VSD can reduce the energy consumption of a
motor by as much as 60 per cent, this type of upgrade helps companies make
significant energy and cost savings in the long term.
Intelligent MCCs
also feature remote controls and better data collection capabilities, which can
be used for condition monitoring and preventative maintenance. In turn, this
reduces maintenance and breakdown costs in the long run and helps companies
minimise overall operational costs and enhance productivity.
Regardless of
the age of your motor control centre, preventative maintenance is the key to
making sure it performs well for longer. After all, you wouldn’t skip an MOT on
your car, so why would you pay any less attention to the motor control centre
that lies at the heart of your industrial plant?
