Flow measurement
T
he need to replace installed process control instrumentation
because of failure, unreliability or unacceptably high main-
tenance, can justify the cost of the replacement even in the
harshest of economic conditions. The measurement may be critical
to the quality, productivity or safety of a vital manufacturing process,
and would typically qualify for expenditure under maintenance, repair
and operations, commonly abbreviated to MRO.
If we consider today's global flowmeter market, and the available
technologies within it, we can observe it divides very roughly into two
halves. One half is represented by the technologies that collectively
dominated the market until around the middle of the last century,
so here we are talking about positive displacement (PD), turbine,
variable area (VA or Rotameter) and differential pressure (DP). The
other half of the market is represented by the modern technologies
of electromagnetic, vortex, thermal-mass, ultrasonic and coriolis.
These modern technologies have, one by one, carved out their
own share of the market over the past sixty years, at the expense
of PD, turbine, VA and DP. Whilst DP meters are predicted to hold
market share going forward, significantly because meters operating
on that principle alone satisfy certain applications, it is clear that
‘the writing is on the wall’ for the others, where modern alternatives
exist. Available statistics indicate collectively a compound negative
annual growth rate approaching -3%. We should understand the
reasons behind that trend and be aware of what options exist when
facing an MRO situation?
Tough decisions in tough times
A further appreciation of the MRO potential can be gained from
considering the challenges faced by manufacturers in the process
industries, where operating profit or even survival can depend upon
improving their cost position. If the product quality or productivity
of a process plant must be improved, then a more accurate or more
reliable flow measurement may be a key component. Scheduled or
unscheduled process stoppages can be necessary when, for example,
a flow meter requires essential maintenance, calibration or outright
replacement. Such process down time can be extremely costly.
Consider a process with a typical liquid flow velocity of 2,0 ml s
in a standard DN50/2" line, giving a flow rate of around 15 500 litres
per hour. If the product in question has a value to its manufacturer
of just R3,25 per litre, then the loss in revenue could be R50 700 for
every hour the process is stopped. Beyond the lost revenue from
the process stoppage, there is the cost of maintaining, calibrating,
repairing or replacing the meter itself, and possibly environmental
cost implications for safe disposal of hazardous product released
from the process line during the operation.
Consider also that in exploring all possible ways to reduce costs,
companies will attempt to switch between fuels used for, say, process
heating operations, according to fuel cost and availability at the time
of purchase. This can mean significant variation in fuel properties,
such as density and viscosity, and fluid temperature variation is of
course a related influence. Thus an older flowmeter technology hav-
ing significant fluid property dependence is inappropriate when fluid
By S Milford, Endress+Hauser
This article considers the significant potential for maintenance, repair and operations (MRO) which exists amongst the extensive installed base
of older mechanical flow meters, where the existing flow meter technology was once the best or only solution for a particular application, but
where now for several possible reasons, it no longer is.
T
ake note
Value of modern 2-wire
technology for MRO
• There remains an installed base of older-technology flow meters.
• There is a case for careful maintenance and life extension of installed
equipment.
• In many cases, newer technologies offer significant advantages that
may give them a cost advantage.
Electricity+Control
July ‘13
16
