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Shaffer-SLX Ram Blowout Preventer
Ram Blowout Preventer

 National Oilwell Varco's Shaffer SLX Blowout Preventer incorporates an optimized design with enhanced features that increase the efficiency of your drilling operation.

Pressure-Energized Door Seal:

Pressure differentially energized modular door seal. As wellbore pressure increases, the differential area between the door face seal and radial seals force the modular carrier towards the BOP door face.

The higher the wellbore pressure, the tighter the modular carrier is forced toward the BOP door face.

Modular door seal utilizes a secondary seal to maintain external pressure integrity. This is ideally suited for subsea use in the event wellbore pressure drops below external hydrostatic pressure; the secondary seal prevents the hydrostatic pressure from de-energizing the modular door seal.

Corrosion resistant material is utilized in the door cartridge seal groove.

Weldless Cavity:

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.

Casing Shear:

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 18¾" 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 provides the reliable performance that today's BOP equipment demands. The CVX Shear Rams are offered for large bore, high pressure BOPs.

Multi Rams:

Shaffer addresses the need for changing out rams on a tapered drillstring by offering Multi-Ram blocks to cover a range of varying sizes of drill pipe from 3½ "to 5" and 5" to 7". The Multi-Ram introduces the potential for the elimination of additional ram BOPs to facilitate the changes in tubular OD on any given string.


The 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. Shaffer UltraTemp rams are designed to seal in temperatures as low as 20°F. This eliminates the need to heat the BOPs and/or the test medium when the surface ambient temperature is low.

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 preventer.

 Optimized Weight and Height:

Current state-of-the-art computer analysis technology allows for accurate simulation of stresses in complex shapes of BOP pressure containing components. Optimization of the BOP pressure containing components results in reduced weight and height of the BOP.

Lower Operating Pressure Requirement:

The SLX outperforms its competitors by requiring only 1,500 psi maximum operating pressure to close the pipe rams and contain wellbore pressure on 10,000 psi and 15,000 psi BOP stacks.

Easier Ram Changes:

  • Fewer door bolts than the earlier SL model preventer
  • Reduced door bolt torque - 32% to 45% typical reductions (refer to BOP Manual for recommended door bolt torque values)
  • Roller bearing hinge assembly - less than 50% of force previously required to open SL model door
  • Maximum of 45° of door swing required to remove the ram (57° on 18" SLX).
  • No critical components exposed when changing rams - no exposed ram shaft or ram change piston rods.
  • No hydraulic pressure required to open or close doors.
  • Safety-enhanced - avoids use of hydraulic pressure to BOP while rams are being changed.