After years of limited changes in the development of BOP
design, the National Oilwell Varco (NOV) line of Shaffer® NXT®
BOP Systems offers the drilling industry improved drilling
economics in a new generation of well control systems. This new
generation BOP has changed the performance expectations for
pressure control equipment, offering significant advantages and
BOLTLESS BOP DOORS:
NOV's Shaffer NXT BOP Systems are unique in providing a
means of significantly improving safety and efficiency in the
critical path of activity. With the replacement of the door
bolts in ram BOPs, NOV has eliminated the time consuming manual
practice of using brute force to torque up numerous large door
bolts. A number of benefits have been realized with this
Reduced Weight (lightest BOP systems in the industry)
Reduced Height (smallest BOP systems in the industry)
Elimination of Manual Labor Under Time Pressure
Elimination of Cross Threading Bolts
Ram Changes go from 4 hours to 40 minutes (15 Minutes with
an ARC™ Automated Ram Changer)
Hydraulic power to operate a Model NXT ram BOP can be furnished
by any standard oil field accumulator system. Hydraulic
passages drilled through the body eliminate the need for
external manifold pipes between the hinges. Each set of rams
requires only one opening and one closing line. There are two
opening and two closing hydraulic ports, clearly marked, on the
back side of the BOP. The extra hydraulic ports facilitate
connecting the control system to the preventer. A standard
hydraulic accumulator unit will close any Model NXT ram.
RAM CHANGING SYSTEMS:
NOV's Shaffer ARC Automated Ram Changing System provides an
additional edge in ram changing economics and safety by
eliminating all hands-on activity involved in changing rams.
The ARC can reduce the crew working on ram changing activities
from 4-5 people to 1-2 people. A simple ram-changing arm
retrieves and replaces rams in minutes quickly and accurately
from a simple removable ram storage magazine.
18-¾" BOP SYSTEMS:
The introduction of the NXT Ram BOP was initially in the
18-¾", 15,000 psi size. This system was designed to
enable a stack height and weight package similar to a
13" BOP configuration and provide the capability of
eliminating the dual stack drilling system with a through bore
wellhead connector. Actuation of the boltless door mechanism is
available in two configurations:
- Remote or door mounted hydraulic operation.
- Simple manual mechanical door actuation at the ram
The introduction of no weld cavities in previous Shaffer BOP
designs is carried on in the NXT models. This feature
introduces replaceable parts to the cavity to eliminate
extensive in-shop repairs and post weld heat treatments. The
seal seat, skid plate and side pads can be replaced upgrading
the BOP cavity tolerances to as new condition.
Shaffer engineers have extended the capabilities of shear rams
with a casing shear ram which meets the specific cutting needs
to physically shear casing tubulars up to 13"; in an
18-¾"; bore BOP.
TYPE CVX SHEAR RAM:
The type CVX Shear Ram enhances the features of NOV's Shaffer
Shear Ram family, assuring multiple shear and sealing sequences
while hung off in a cavity below the shear ram cavity. No
additional force is required to manipulate the fish. This
multiple shear and seal capability enhances shear ram
reliability and extends the length of BOP stack deployment.
Type CVX Shear Rams are capable of shearing at 20% lower
pressures than conventional shear rams.
CVX Shear Rams are designed for durability and convenience,
and provide the reliable performance that today's BOP equipment
demands. The CVX Shear Rams are offered for large bore, high
NOV addresses the need for changing out rams on a tapered
drillstring by offering MULTIRAM blocks to cover a range of
varying sizes of drill pipe from 3-½" to 5"
and 5" to 7". The MULTIRAM introduces the
potential for the elimination of additional ram BOPs to
facilitate the changes in tubular OD on any given string.
NOV's conservative Shaffer testing procedures call for
maintaining pressure and temperature for the duration of the
test. Even with these stringent demands, the UltraTemp rams
hold in witnessed testing. NOV's Shaffer UltraTemp rams are
designed to seal in temperatures as low as 20Â°F. This
eliminates the need to heat the BOPs and/or the test medium
when the surface ambient temperature is low.
NOV's Shaffer UltraTemp ram assemblies are designed to
safely withstand wellbore pressures up to 15,000 psi and
extreme temperatures up to 350°F (177°C) for prolonged periods.
This translates into rigsite capability to safely evacuate
personnel and equipment in the event of a major high
temperature, high pressure kick.
ULTRALOCK™ II RAM LOCKING SYSTEM:
The UltraLock™ II locking system incorporates a mechanical
locking mechanism within the piston assembly. This locking
system is not dependent on closing pressure to maintain a
positive lock. It uses flat tapered locking segments carried by
the operating piston which engages another stationary tapered
shaft located within the operating cylinder. Using SL-D™ rams,
the UltraLock™ II has hang-off capabilities up to 600,000
pounds at full working pressure. The system needs no
adjustments, no matter the size of the pipe rams. Different
size or type ram assemblies can be freely interchanged.
Only one hydraulic function is required to operate the
cylinder's open/close function and the locking system. The
system automatically locks in the closed position each time the
piston assembly is closed. Once the operating piston is closed
on the pipe, the locks are engaged until opening pressure is
applied. Only hydraulic pressure can unlock and reopen the