View
224
Download
0
Category
Tags:
Preview:
DESCRIPTION
Bad Vibes Felt
Citation preview
S U M M E R 2 0 0 2
SPOTLIGHT ON OIL & GAS
PAGE 4CONTROL’S A GAS WITH CCI
PAGE 2-4BAD VIBES REPLACED WITH SEVERE SERVICE DESIGN
PAGE 7CCI HELPS WILPRO GO FULL THROTTLE
PAGE 7TECHNOLOGY IS A DRAG® AT DAKOTA
PAGE 8DRAG® HELPS KEEP THUNDER HORSE UNDER CONTROL
PAGE 6NOISE TAKES ON GULLFAKS C TURNS FOR THE BETTER WITH DRAG®
PAGE 5THE PRESSURE’S OFF AT SECUNDA
2
HOW DRAG®
ELIMINATES
HIGH VIBRATION LEVELS
Bad Vibes Felt at Offshore Platform— Replaced with DRAG® Design
EVER SINCE INITIAL OPERATION IN MID-1998, the 8-in.
(200-mm) recycle valves in the main oil line (MOL) export
system Eastern Trough Area Project offshore platform had been
experiencing extreme vibration problems. This North Sea platform is
operated by BP AMOCO on behalf of its partners.
Flow-induced vibration was extreme in the valves themselves, causing
excessive vibration as well as of the associated piping and structures.
The valves were suffering from continual failures in the gland-packing
assemblies, instrument and air supply tubing, and the mechanical and
electronic components of the position feedback control assemblies.
These MOL export pump recirculation valves were designed for a
maximum flow of 900,000 lb/hr (404,000 kg/hr) at inlet pressures
as high as 3200 psia (220 BarA) and ΔPs of 2900 psi (200 Bar) at
150 F (63 C).
After an evaluation of the problem in July of 1999 by JMDynamics,
it was recommended that the valves be replaced. However, for
operational reasons, this could not be immediately done. A revised-
design trim replacement in these three-stage cage/diffuser valves was
accomplished, but this failed to mitigate the severity of the vibration
problem.
On May of 2001, JMDynamics was called in to again evaluate this
continuing vibration problem. The company used Southwest Research
Institute’s (SRI) vibration-
level criteria as a guide
only for the evaluation
of results from piping
vibration testing. These
provide vibration criteria
acceptance as a function
of frequency and use two
predominant levels of
acceptance.
Figure 1: The replacement “A” MOL recycle valve
3
When these MOL
pumps startup
or shutdown,
the control
valves are 100-
percent open. From
a vibration point of view, this is
their most critical operating condition,
and a maximum vibration level of 25 mm/sec RMS
was recorded in the horizontal direction on the control-assembly
mounting plate; the dominant frequency was 29 Hz.
At this point, JMDynamics’ original recommendation that
these valves be replaced with new CCI severe service valves was
instigated. These valves are specifically designed to minimize
vibration through limiting trim flow velocity for this severe, very
high ΔP service.
Replacement Valve Design
To eliminate the destructive effects and potential dangers of
high vibration levels in the severe-service application, the new
replacement valves (Figure 1) are designed to limit trim fluid
velocities to less than 100 ft/sec.
This is accomplished through multi-stage pressure reduction
(over 20 stages) within a stack of tortuous-path, electro-
discharge-machined (EDM) disks containing a series of
sequential, right-angle turns, Figure 2. In addition, each disk
incorporates a pressure-equalizing ring (PER) on its inside
diameter to ensure that equal pressure acts radially around the
circumference of the plug at any position in its stroke. This
design keeps the plug centered at all loads, thus preventing plug
vibration that could cause galling and impede free stroking
motion.
Also, the actuator control is provided with a snap-action relay
which is set to reduce operating time of the valve at very low
Table 1: A 1999 vs. 2001 comparison of the RMS vibration measurements on valve actuators and bodies taken in XYZ directions.
Description LocationJuly 1999 Results* October 2001 Results*
Valve A Valve A Test 1 Test 2
100% Open 30% Open A-100%, B-60% B-100%, A-10%
Valve Actuator
1x 24.7 4.5 2 2.1
y 17.4 8.4 3.1 4.0
z - - 1.2 1.6
Valve A Body
4x 8.6 1.4 0.7 0.6
y 10.3 1.4 1.4 1.4
z 18.6 - 1.3 1
Valve B Actuator
11x 12.5 - 2.9 2.6
y 16.1 - 4.4 3.8
z - - 1.2 1
Valve B Body
14x 6.8 - 0.9 0.8
y 8.0 - 0.9 1
z - - 0.8 0.7
* Pump and valve A operating only, no flow through pump or valve B
Figure 2 – A multi-stage pressure reduction
disk stack with individual disks showing the
right-angle, tortuous flow paths.
Figure 3: A schematic of the two, parallel MOL pump recycle
systems showing the points of valve vibration measurement.
(Continued on page 4)
Control’s a Gas with CCI
4
flows when the plug would be close to the seat. Under the
close seat/plug conditions, high, resultant fluid velocities
could result over time in seating surface erosion.
Results of Valve Replacements
Vibration levels were recorded not only at many points
throughout the MOL recycle valve associated piping and
support structures, but of course also on the two valve bodies
and actuators involved as indicated in Figure 3. Table 1
shows comparatively the root-mean-square (RMS), vibration
reduction by a factor of 10 at these valve locations between
the original valves tested in 1999 and the multi-stage
pressure reduction valves tested in October of 2001. Figure
4 shows a typical peak actuator vibration comparison under
Figure 4: A typical plot of before and after actuator peak vibration
spectra over a wide frequency range.
(Continued from page 3)
relatively comparable conditions. This vibration level reduction is
even more significant since the replacement valves operate at a higher
flow and pressure drop than the original valve. In addition, there is
now virtually no transmission of vibration energy to the piping and
support structure.
CONTROL VALVES IN THE GAS
TRANSMISSION INDUSTRY have
traditionally sacrificed capacity and noise
for low-end control. For many systems,
flow-impinging valves may seem the best
solution, but they don’t offer both high
capacity and low-end control in optimal
ranges. This results in gas transmission
organizations having to accept the
need for expensive bypass systems and
the willingness to live with noise and
cavitation.
To address these needs, CCI has introduced
the Rotary DRAG® valve which marries
the high capacity of a rotary valve and the
proven multi-stage technology of DRAG®.
With the potential for more than 28
stages of pressure reduction, the result is
an axial flow control valve with very high
capacity, and low-end control that rivals
all other valves on the market. Now the
applications that traditionally utilized two
valves in parallel will only need one Rotary
DRAG® valve. This creates a substantial overall reduction in maintenance costs and
eliminates the need for low-end bypass control for most gas transmission applications.
At a minimum, Rotary DRAG® technology will impact future design considerations for
gas interconnect, distribution and blending stations, as well as the basic design and
control philosophies used within the transmission industry.
The valve industry realizes that designs
utilizing expanding right-angle
flow paths effectively reduce
fluid velocities and provide
effective valve control.
The cost of this
control has always
been capacity;
however, with the
introduction of
the CCI Rotary
DRAG® valve, gas
transmission
groups will no
longer need
to make the
decision between
valve capacity and
performance.
5
SASOL RECENTLY FACED A CHALLENGE WHEN ONE OF
THE VALVES INSTALLED AT ITS SECUNDA PLANT BEGAN
EXPERIENCING PROBLEMS. The plug on one of the existing valves
kept separating; this caused rotating and damaging of the plug, the
seal ring, and jamming of the valve. The pin holding the stem also
came loose, requiring an efficient replacement at Secunda.
Understanding why a selected valve is not performing satisfactorily
is not always known and in many cases is accepted as the norm.
Many attempts throughout the industry aim to resolve the
problems by addressing the effects of the damage. For example, the
use of harder materials when erosion and cavitation damage occur.
These solutions only marginally prolong the time at which failure
will take place. Problems like erratic control, noise, mechanical
vibration, cavitation, erosion, and short life are best solved by
controlling the cause of damage.
To overcome Secunda’s challenges, CCI provided a resolution that
would address the root cause of the problem with a customized
specification for the site’s steam pressure application. Sasol
received two, 16-in. x 16-in. (400-mm x 400-mm) control valves
The Pressure’s Off at SecundaThe DRAG® disk
stack incorporates a
pressure equalizing
ring on its inside
diameter to ensure
equal pressure
acting radially on
the valve plug at all
times. This eliminates
the vibration that could
occur because of rapid plug
radial movement.
with design temperatures of 570 F (300 C). Incorporating
DRAG® technology, the disk stacks have pressure equalizing
ring (PER) grooves built into them and each disk is made with
a land on the inside diameter so that localized pressure from
each disk’s outlet is equalized around the plug. This eliminates
radial forces on the plug which might otherwise cause binding
in under-the-plug applications and/or radial vibration and
buffeting in over-the-plug applications.
THE CHALLENGE OF THE RICH-AMINE APPLICATION IS
A COMPLEX ONE; the process begins when amine liquid is
pumped into the top of a column and raw gas enters along the
bottom, passing through the amine liquid as it rises. This process
removes H2S and CO2 from the gas and absorbs it into the amine
liquid, allowing the gas to leave the column “clean” and ready
for distribution or use in a refinery. The remaining amine at the
bottom of the column is now referred to as “rich amine.”
The column is maintained under pressure to improve the
efficiency of the absorption process. At this pressure and
saturation point, the rich amine is a multi-constituent fluid with
a vapor pressure close to that in the column. As the fluid passes
through the rich amine letdown valve, the pressure drops across it,
causing the gases to be released from the amine.
If a valve’s design is based on a
presumed lower vapor pressure,
catastrophic consequences can
result, such as high mechanical
vibration that shuts down
the train. DRAG® technology
provides the number of pressure-
reducing stages required to limit
the kinetic energy produced,
providing the needed reliability
to keep production running and
producing profit.
Rich-Amine Letdown in Refineries and Gas Processing Plants
WHEN STATOIL’S GULLFAKS C PLATFORM RECENTLY
UPRATED ITS COMPRESSORS, they revamped their
piping and replaced their compressor-recycle valves. During
initial testing on Train A in early October 2001, they observed
excessive noise levels – as high as 126 dBA – within the
revamped piping surrounding a new recycle valve and the valve
itself, Figure 1.
The piping revamp included five new elbows and two flange
joints within 15-ft (4.5-m) of the valve inlet. It also included
an 18.5-in. (455-mm) spool piece to reduce the pressure class
just downstream of the valve. This was accommodated by a
spool piece that included one 1500 ANSI flange joint, one 600
ANSI flange joint and a slight expansion in the spool itself to
accommodate the decrease in pipe wall thickness, Figure 2. The
flanged joints were all the ring-type joint (RTJ) design.
Because the high frequency noise was judged to be in excess
of 85 dBA, and the noise seemed to have a “trigger” point
associated with a specific valve lift, CCI was contacted by Statoil
and Aker Engineering to assist in determining the source of
the noise. An audit confirmed that the valve should not be
producing the noise, and that there was no noticeable vibration
of the valve stem or actuator, something frequently related to
noise.
Statoil and Aker Engineering contracted a consulting firm to
learn about the specifics of the observed noise. They carried
out detailed and accurate noise measurements under varying
compressor and valve operating conditions. The dominant
noise frequency was 2000 Hz and the peak noise level was
126 dBA. This peak noise level occurred at the ANSI 1500/600
transitional spool piece. The noise level in the upstream piping
ranged from 112 to 115 dBA. Farther downstream, where the
piping was insulated, the noise level dropped off from 123 dBA
to 113 dBA.
It was decided that a spare valve made at the same time as the
one at Train A would be disassembled and inspected while the
installed valve continued to be used for compressor testing. It
was also decided that at the next shutdown, a flexible perfluoro-
elastomer filler material would be installed into the RTJ flange
gaps at the inlet and outlet end of the spool piece to assess
its impact on reducing the noise at that location. At that time,
the installed valve could also be visually inspected through
the valve outlet to see if any constructional anomaly could be
observed. After this
modification was
completed, and
upon restarts of the
Train A compressor,
a significant noise
reduction was
observed (in excess
of 10 dBA) such that
the dominant noise
now seemed to be coming from the upstream side of the valve. The
dominant frequency remained at about 2000 Hz.
Based on this experience, it was concluded that the source of the
noise was probably not the valve, but rather the piping, and it
was further decided to install soft fill-in gaskets in the RTJ flanges
upstream of the recycle valve as well. This was carried out a few days
later during a scheduled compressor stop. New noise measurements
were again taken that showed the previous high-frequency noise
in the piping system adjacent to the anti-surge valve had been
eliminated.
The final conclusion was that the noise arose solely from significantly
increased gas velocity in the piping following the uprated capacity
of the export compressor. When the gas velocity in the piping, as
determined by the valve opening position, became sufficient, it
triggered a resonant frequency in the flange gaps (similar to blowing
across the top of an empty bottle).
Checking conventional design rules for gas service pipe sizing also
showed that the
compressor uprating
had produced
a significantly
increased gas
velocity over normal
recommendations
for the pipe sizes
involved. It was
further concluded
that the anti-surge
recycle valves did
not represent any
significant noise
problem in Satoil’s
current operations.
Noise on Gullfaks C Takes a Turn for the Better with DRAG®
Figure 1
Figure 2
6
7
AT THE DAKOTA GASIFICATION
COMPANY, AN EXISTING VALVE was
experiencing erosion of the trim. This resulted
in high maintenance for the company, and
required a solution to handle the process
conditions of the Dakota Gasification
Company.
Typical problems caused by incorrect
technology in severe service valves include
premature trim and body erosion due to lack
of velocity control along the flow path. Trim
damage reduces the trim’s ability to control
spraywater flow, which is why it’s important
to avoid high velocity areas. Avoiding this
occurrence allows for the life of the trim to
increase considerably. CCI’s unique DRAG® design produces a highly
reliable and precise level of flow control to
eliminate the possibility of erosion problems.
To address this issue, Dakota Gasification
is replacing the valve with a 1-in. (25-mm)
globe valve, specifically designed to handle
Dakota’s application requirements. By
utilizing DRAG® technology, the risk of
uncontrolled fluid velocity is eliminated
through the unique tortuous path trim
design. This controls fluid velocity by
forcing the pressure drop to occur in
several stages, reducing it as it passes
through each channel and stage. The
replacement valve will have design
pressures of up to 1500 psig (103 bar) with
temperatures up to 300 F (150 C).
Technology is a DRAG® at Dakota
CCI Helps Wilpro Go Full Throttle
AT WILPRO’S EL FURRIAL SITE
IN VENEZUELA, gas to flare
valves were creating problems in
production. These existing valves
were suffering from gas leakage when
closed, and high noise levels during
venting conditions that Wilpro found
unacceptable.
Leakage in the gas to flare application
creates serious issues for a plant,
particularly since the products that
need to be flared tend to be high cost
items. A constantly leaking valve also
causes energy from the system to be
lost, which increases plant costs. Even
a minute leak can grow quickly into
a large one, eventually affecting the
valve’s internal parts performance.
Additionally, El Furrial was also
experiencing high noise levels during
venting, which in gas to flare can
indicate a high-pressure drop that
results in shortened life and high
maintenance costs.
For these reasons, El Furrial is
replacing its valves with two, 14-in.
(355-mm) 100D DRAG® valves. With
design pressures up to 1350 psig (93
bar) at temperatures that range up to
120 F (50 C), these replacements will
eliminate the possibility of excessive
noise by using unique multi-passage
trim designed to control high pressure
drop. In addition to this, the DRAG®
valves are specifically designed for
long-term shutoff, to avoid any
unnecessary seat leakage. A DRAG® block angle valve similar in design to the
one supplied to El Furrial.
8
CCI World HeadquartersTelephone: (949) 858-1877Fax: (949) 858-187822591 Avenida EmpresaRancho Santa Margarita,California 92688 USA
CCI Switzerland Telephone: 41 52 262 11 66Fax: 41 52 262 01 65Hegifeldstrasse 10CH-8404 WinterthurSwitzerland
CCI Sweden (BTG Valves)Telephone: 46 533 689 600Fax: 46 533 689 601Box 603SE-661 29 SäffleSweden
CCI ChinaTelephone: 6501 0350 0650Fax: 6501 0286Room 567/569 Office TowerPoly Plaza14 Dongzhimen South AvenueBeijing 100027China
CCI KoreaTelephone: 82 341 980 9800Fax: 82 341 985 055226-17, Pungmu-DongGimpo CityKyunggi-Do 415-070Republic of Korea
CCI Austria (Formerly Spectres Components GmbH)Telephone: 43 1 869 27 40Fax: 43 1 865 36 03Carlbergergasse 38/Pf. 19AT-1233 ViennaAustria
CCI ItalyTelephone: 39 035 29289Fax: 39 035 2928246 Via G. Pascoli 10A-B24020 Gorle, BergamoItaly
CCI JapanTelephone: 81 726 41 7197Fax: 81 726 41 7198194-2, ShukunoshoIbaraki-City, Osaka 567-0051Japan
Contact us at:info@ccivalve.com
All rights reserved. Solutions™, DRAG® and CCI DRAG® are trademarks of CCI. CCI valves are manufactured under various United States and international patents.
©2002 CCI 518 8/02 10K
Visit us online at:www.ccivalve.com
DRAG® Helps Keep Thunder Horse Under Control
BP AMOCO DISCOVERED FOUR OIL FIELDS IN
THE GULF OF MEXICO, known as Atlantis, Mad Dog,
Holstein and Thunder Horse. Of these Thunder Horse
is the largest, located 6,000 ft (1830 m) in the Boarshead Basin.
With estimated recoverable oil of at least one billion barrels of
oil equivalent (boe), it is the biggest discovery ever made in the
Gulf deepwater.
To ensure that all equipment used in this project will have the
utmost reliability, BP Amoco chose DRAG® valves for their water
injection pump recycle application. These four, 4-in. (100-mm)
100D angle valves have been designed for inlet pressures of up to
8600 psig (593 bar), with temperatures up to 200 F (93 C).
Challenging the project is the need for absolute reliability:
because most deepwater projects are justified by their huge
energy reserves, any loss of revenue as a result of unexpected
shutdown can easily exceed the high remediation cost.
Experience shows that fluid velocity control along the flow path,
as in DRAG® technology, is necessary for long-term reliable
performance. By combining CCI’s unique capability to easily
vary the number of disks in each stack, a DRAG® valve eliminates
problems such as trim and body erosion, noise vibration and
poor process control that can result from excessive fluid velocities.
This is why it is essential that the valve design features match the
specific application requirements. If this is not so, then there is
little hope that corrective actions after installation will be able to
overcome the initial errors.
DRAG® technology will be supplied to Thunder Horse, one of the
largest oil discoveries made to date by any company.
Recommended