Page 39 - Gi flipbook April 2019

DeSIGN STANDARDS & BeNeFITS
The method of supporting the ball in a trunnion mounted ball
valve is of little importance in cases when the valve is small and
the pressures are low. However, the forces generated in a large
valve closed against high pressure are enormous and they create
2500
a major challenge for the valve designer. The magnitude of the
stresses and deflections generated by these forces depend upon
the design employed for supporting the ball. If stresses are too
2000
high some form of valve failure will occur, either initially or at some
time during service. If deflections are excessive, then the valve
1500
operating torque will be too high and the bearings may be unevenly
loaded resulting in premature failure.
1000
In some designs of trunnion mounted ball valves, trunnions project
from inside the valve body into sockets in the ball. These trunnions
are therefore subjected to a couple which could be massive and TON F 1500 600 900 300 150
500
result in unacceptable deflections together with high stress levels in
the valve body which is already subject to pressure forces. In other
designs, the valve stem is used as a trunnion which creates the 6” 12” 18” 24” 30” 36” 42” 48”
additional problem of possible stem leaks due to the application of
side loads to the stem seals. NOMINAL VALVE SIZE igem news – yppc
FIGURE 1 CORT C-B5 BALL VALVE CROSS SECTION
FEATURES AND BENEFITS
As one of the most trusted valves in the petroleum Engineered for heavy-duty, maintenance-free performance,
BeARING
BODY BeARING ReTAINeR
industry, the CAMERON fully welded ball valve combines the CAMERON fully welded ball valve is commonly
the strength of forged components with a lightweight selected for a number of applications, including:
ClOSURe
and compact spherical design. • Gas transmission • NGL plants
CAMERON fully welded ball valves satisfy ASME/ANSI • Product pipeline s • NGL pipeline
150 to 2500 (PN 20 to PN 420) and API 2000 to 5000 • Measurement skids • Compressor stations
standards. Made of forged steel to ensure uniform fine • Dehydration systems • CO services
2
grain structure and toughness, they can be specified in • Gas separation systems • Offshore
sizes from 2” to 56” (50 mm to 1400 mm).
• Natural gas storage • Subsea
BAll
• Dryer service
ThRUST WASheR
lOCATING PIN
BeARING
The distinctive design of the CAMERON fully welded ball valve gives it strength at reduced weight, as well as resistance to
both pipeline pressures and stresses. The compact, spherical design also eliminates body flanges, reducing overall size and
potential leak paths.
The design used in the CORT C-B5 for supporting the ball is not
FIGURE 2 CAMERON C-B5 VALVE OVERVIEW closures via the bearing retainers, which are put into compression.
the lowest cost but it is the most elegant and effective engineering The result is that for practical purposes, bending is eliminated from
solution. Both trunnions and the ball are a single component, thus these components and the deflections produced are minimal.
PTFE lip seal
Forged body and ball provides superior
eliminating the problems associated with a highly stressed joint. Mating surfaces remain square and parallel to each other so
ductility and strength for added safety
The trunnions are as close together as possible (normally within that stress distributions are uniform and stress levels remain
the ball spherical diameter) ensuring that the bending moment low. The stem is not rigidly attached to the upper trunnion and
PTFE delta seal
is minimised and applied to only the stiffest part of the ball. The therefore, although it can apply torsion to the ball, no side thrust is
trunnions are short in relation to their diameter and primarily transmitted from the ball onto the stem seals.
subject only to shear stress. The force is transmitted into the valve Compact body design gives increased
Stem sealant injection
strength with reduced weight
3 Valves and Through-Life Asset Management
Floating seat ring with seat to ball seal
(Various seat arrangements available
on pages 6 and 7)

Sealant port with check valve permits safe
injection of sealant for fast, simple
restoration of tight shutoff

Body bleed fitting allows double
block-and-bleed testing of valve seals in Trunnions encased in PTFE impregnated
either open or closed position stainless steel bearings for smooth
operation without lubrication

buried valves at Kings Lynn Compressor may have water in the drive stems evidence that water ingress is apparent 3
Station were found to have water in the below ground.” (DNV GL, 2016) within the stem extensions on buried
annulus between the torque tube and The DNV GL report is focused on the valves. The report suggests that further
drive shaft above ground.” potential for water freezing within the methods should be developed to detect
It was also stated that “valves where valve stems causing operational issues; the presence of water within the stems
water was not detected above ground however this information provides direct through keyhole tooling techniques.

39

IGEMNews_YPPC.indd 2 14/03/2019 14:23