Much of the RKPL network will be newly constructed
pipelines, but it does also draw from and includes
sections of older pipelines in which scale has accumulated
as they age. In consequence, refined hydrocarbon fuels
may contain fine particles of scale. Through time, scales
were being deposited on the inner magnetic ring of gear
pumps and and causing serious internal damage.
To inhibit the ingress of scale particles the magnetic
drive pumps would need the protection of fine filtration
systems in the pump inlet piping – not a practical
solution in an unsupervised location.
The difficulties afflicting the RKPL and other networks
were eventually resolved by using pumps of a different
type for sampling systems – seal-less diaphragm pumps in
the Wanner Hydra-Cell range that can handle abrasive and
other problematic liquids by design, and do not need fine
filtration. On the RKPL Hydra-Cell pumps are incorporated
in sampling systems for analysing density (manufacturer
Emerson Process Management) and sulfur content
(manufacturer Bartec).
Similar circumstances
Comparable issues were being faced and overcome in
density analysis systems elsewhere; at the Government-
owned Mumbai-based refinery for example, and along the
pipeline that links it with markets across the country.
At another large refinery, operated at Vadodara
(Gujarat) by Yokogawa, magnetic drive gear pumps in
sulfur content analyser systems had to be replaced every
two months because of gear damage, attributed partly
to scale ingress and partly to handling non-lubricating
fuels (high-speed diesel and petrol) at high pressures and
temperatures up to 45˚C or higher.
For many years the refinery had used magnetic drive
gear pumps for sampling - but with their life expectancy
so low it was decided to make a change. For a new system
manufactured by Chemtrols Industries the pump specified
by the manufacturer was a Hydra-Cell G10.
The pump began running at Vadodara in January 2011.
Three years later, with no maintenance needed and no
troubles to relate, it was still working reliably. Similar
reports have come from other pipeline and refinery sites
– including the world’s largest refining and petroleum
complex, operated by Reliance Industries at Jamnagar.
Zero leakage is a given requirement for an
unsupervised pump handling petroleum liquids on a
pipeline sampling system. In Hydra-Cell pumps it follows
automatically from a unique design concept in which
flexible hydraulically-balanced diaphragms deflect in
sequence to provide the pumping action while totally
isolating the pumped liquid from the drive mechanism.
This is always submerged in lubricant. There are no
dynamic seals, packings or close-tolerance mating surfaces
in the pump – no potential for leaks or premature wear.
Out of these features come further benefits relevant
in sampling applications: the pumps can run dry
indefinitely without damage; they can handle virtually
any liquid, hot or cold, including thin non-lubricants and
those containing abrasive particles; they do not need fine
filtration; being hydraulically balanced the diaphragms are
stress-free, enabling the pumps to work efficiently at any
discharge pressure up to 70 bar (or higher, depending on
the model).
On sampling/analyser systems flexible operation is
needed. Discharge pressure requirements vary with the
application. application. On Emerson installations along
HPCL’s Rewari-Kanpur, the Hydra-Cell G10 pumps are
operating at pressures up to 40 bar and G15 pumps also
in use are working at pressures up 100 bar; the G10 at
Vadodara from 10 - 60 bar, while a system at the refinery
in Mumbai calls for operating pressure of only 9 bar.
Hydra-Cell technology also has advantages on the
suction side of the pump. Analyser stations
are typically sited at some distance
(sometimes up to 100 m) from the main
pipeline, and the interconnecting small-bore
pipework may have numerous bends, drops
and rises: features that together create
adverse suction conditions at the pump
inlet.
Pressure drop through the pipework
can reduce NPSH available to less than
that required by the magnetic drive pumps.
Hydra-Cell pumps are better able to handle
these conditions, and perform with equal
efficiency in the less common situation
where inlet pressures are substantially
higher than those typically encountered in
sampling applications.
Note
With thanks to the Hydra-Cell support company in India,
Machinomatic Engineers.
Figure 3.
Hydra-Cell G10 and G15 sampling pump installations by Emerson
Process Management (HPCL – Rewari Kanpur Pipeline network).
66
World Pipelines
/
MARCH 2016
