Hydrocarbon Processing - August 2022 - 65

Bonus Report Gas Processing & LNG Industry Spotlight
M. RAKITA, Emerson Automation Solutions,
Fiorenzuola d'Arda, Italy
Why compact actuation solutions are ideal
for constrained space installations
Many oil and gas industry applications
face space constraints. This limitation requires
more compact solutions providing
the same performance as traditional alternatives,
and this is particularly true in many
valve installations, where actuators often
require an inordinate amount of space.
This article will examine two applications-a
floating production, storage and
offloading (FPSO) vessel, and a floating
liquefied natural gas (FLNG) vessel-
where space is at a premium, although
the problems and solutions discussed are
often found in many other areas of the oil
and gas value change.
The ultimate space constraint. The
landscape of oil and gas production is
changing very rapidly. The LNG market
has significantly expanded, driven by
the soaring cost of energy, as well as by
a global desire to switch to lower carbon
fuel alternatives.
To reduce costs and make smaller,
deepwater oil and gas reserves economically
feasible, many producers are turning
to offshore processing units. These FPSO
vessels are becoming increasingly common
all over the world, but their compact
design creates significant challenges for
engineers tasked with putting so much
equipment in tight spaces.
One glance at an FPSO unit tells the
story (FIG. 1). Unlike a typical onshore oil
and gas production facility that has more
space, an FPSO facility must jam an entire
oil and gas production plant into a very
limited footprint.
FPSO vessels are particularly effective
in remote or deepwater locations where
running seabed pipelines are cost prohibitive.
These units also eliminate the need
to run costly long-distance pipelines to
onshore processing facilities, and they
can be moved to another location when
a field's production tapers off. However,
their main disadvantages are the obvious
limitations on available space, along with
particularly harsh saltwater environments.
Designing all equipment to fit in such
close quarters, while allowing this equipment
to be maintainable, is a very challenging
engineering problem.
The drive toward developing natural
gas reserves has spawned an offshore
floating facility devoted to natural gas
processing, storage and transfer (FIG. 2).
These vessels (i.e., FLNG units) are like
FPSO units, as they accept and process
natural gas from a variety of fields, store
LNG as required, and then transfer it to
large ships for transport around the world.
FLNG production units face the same
challenges as FPSO ships in that they
must wedge an enormous amount of
equipment and piping into a very limited
space. However, the FPSO designer's task
is made even more difficult by the high
pressures, cryogenic temperatures and
very large line sizes common in the LNG
industry. Fitting 100 automated valves in
a small footprint is difficult. Fitting a hundred
24-in., 900-class automated valves in
that same constrained space is even more
of a vexing problem.
Standard actuators do not
fit. A
scotch yoke or rack-and-pinion actuator
(FIG. 3) works well in a facility where
there are no space constraints. A typical
actuator is mounted above the quarterturn
valve, and it has a pneumatic or hydraulic
cylinder on one side of the shaft
and an opposing spring cylinder on the
other. The pneumatic cylinder uses air
pressure to drive the valve to the actuated
state, and the spring drives the valve back
to the fail-safe state upon loss of air or
power. This design is proven and robust,
operating reliably in millions of valve applications
all around the world.
Unfortunately, typical actuator designs
have a very large footprint, especially when
the pneumatic
cylinder
and opposing
spring are sized to handle very high pipeline
pressures. Even when mounted with
the actuator running parallel with the pipe,
sufficient space in all directions must be
left open to access and replace the actuator,
if necessary. In an FPSO, FLNG or other
space-constrained environment, this type
of actuator is not feasible in some cases
because installation space is not available.
A better solution. Fortunately, a new
actuator design dramatically reduces the
footprint of the actuated valve. Helicalslot
actuators combine the pneumatic
cylinder and spring cylinders into a single
vertical housing mounted directly to the
top of the actuated valve (FIG. 4).
As the air pressure pushes the cylinder
downward, rollers move in the helical
slot, converting the vertical movement of
the cylinder into rotational movement to
turn the valve. When the cylinder pressure
is released, the spring drives the cylFIG.
1. An FPSO gas and oil facility is the
ultimate study in space management, as every
component must be carefully chosen to fit
within a very tight envelope.
Hydrocarbon Processing | AUGUST 2022 65
Hydrocarbon Processing - August 2022

Table of Contents for the Digital Edition of Hydrocarbon Processing - August 2022
