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Subsea - Hoffer Meters in the Depths of the Ocean
It has long been known that some of the largest reserves of
oil and gas lay below the waters of the world’s oceans.
For the last several decades the relatively shallow coastal
waters have been the center of activity to locate and extract
these reserves. With the ever increasing demand for energy
and the increasing price of energy, oil companies have been
forced to look in deeper and deeper water to locate new reserves.
Until the last few years, the limitation on how deep underwater
a reserve could be tapped was the ability to build a fixed
production platform structure tall enough and big enough to
reach the ocean floor. This limited production to water depths
of no more than a few hundred to just over 1000 feet. That
is no longer the case. The invention of advanced subsea production
systems, remotely operated vehicles (ROV’s) and floating
oil and gas production facilities have now pushed the limitation
on water depth out to the 10,000-foot mark and soon beyond.
Accurate flow measurement of a variety of fluids used in these
subsea production systems located on the ocean floor and on
the ROV’s used to service them at these extreme depths
is critical to their proper and safe operation. Measurement
applications include specially formulated hydraulic control
fluids, drilling mud and seawater.
Illustration #2 4” Subsea flowmeter
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Hoffer Flow Controls is a leading supplier of highly
customized flowmeters to meet the extreme conditions
associated with working at depths to 10,000 ft or more.
In addition to high internal operating pressures of
up to 10,000 PSIG and more, the meters must withstand
high external pressures created by the sea. These pressures
can reach as much as 5000 PSIG. The temperature of the
seawater to which the meters are exposed is often well
below 32° F (0° C). The salt content of the
seawater prevents the water from freezing but still
reduces the strength of metals which must be taken into
account. The need to transmit the flow signal to a remote
input control device, either located subsea or on the
surface aboard the production facility, requires the
use of specialized electrical connectors to permit wiring
interfaces. These connectors are often welded to the
top of special risers that enclose the meter coil (See
Illustration 1). This coil riser enclosure must also
be able to withstand the high external pressure exerted
by the sea and remain watertight.
Above all else, however, the flowmeters must be exceptionally
reliable. Day-in and day-out the flowmeters must function
accurately and reliably at these depths without routine
servicing or maintenance When a subsea system has to
be serviced, it is a logistically complicated and financially
expensive operation. Though scheduled servicing is required
on the systems; an unscheduled service call due to a
flowmeter failure is simply not acceptable. The extraordinary
reliability of Hoffer turbine meters under these conditions
has made them the preferred choice for many subsea system
manufacturers.
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Pictured in Illustration #2 is one of three custom-built
Hoffer 4” flowmeters recently built for use on
a new subsea system being developed for operations at
depths to 10,000-feet and beyond. These are perhaps
the largest turbine meters ever built for operation
at these depths. The meters feature a proprietary high-pressure
clamp-type end fitting specified by our customer. They
are rated and tested to internal and external operating
pressures of 10,000 PSIG. The coil rise atop the meter
is built from a smaller version of this same connector.
It mates with a blind connector (not shown) to form
the riser enclosure. In the upper portion of this riser
enclosure, a HIT-1B transmitter is also located to provide
a 4-20 mA output signal that is transmitted to a controller
remotely located in another subsea enclosure. From concept
to final product, these meters were designed, built
and tested in 12-weeks, an astonishingly quick turnaround
for such a highly customized product. Once again, when
the pressure to perform was on, Hoffer delivered. |
Illustration #1 5/8” Subsea flow
meters with special electrical
connectors |
Whether your requirements for flow measurement take
you to the depths of the ocean, the outer reaches of
the Solar system or on plain Terra Firma, call on Hoffer.
We have the experience to deliver the performance you
need, when you need it. |
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