Every conventional land drilling rig uses some form of bell nipple flange connected at the top of the blowout preventer ( BOP ) stack. This flange does not hold well pressure, but acts as a fastening device to connect a vertical pipe, referred to as a bell nipple, to the top of the BOP stack. For a typical installation see the illustration below.
Contact us to discuss your requirements of 16 3/4”Annular BOP. Our experienced sales team can help you identify the options that best suit your needs.
TYPICAL BELL NIPPLE AND FLANGE INSTALLATION BELOW DRILLING RIG FLOOR
Operators have chosen many ways to fabricate this assembly of flange and pipe nipple. Sometimes they make the flange from torch cut plate, thin and flimsy, without a ring groove, using a piece of “soft line” in the BOP ring groove to make a seal. Sometimes they use a flange cut from some piece of wellhead equipment.
Often operators fasten the flange to the tapped upper connection of the annular BOP with only 4 bolts, the remaining tapped stud holes in the BOP upper connection left without the protection of tightly engaged tap end studs. The empty tapped stud holes collect water and waste and rapidly deteriorate and become useless. In some cases, operators attempting to protect the tapped holes with short “screwed-in” all thread plugs; find that only drilling in a machine shop will remove the plugs. These common, less expensive installations, may actually have the greatest cost among the available options.
One of the most practical, and over time least costly, bell nipple and flange assemblies, utilizes a full thickness flange, retained with a full set of tap end studs tightly engaged in all the tapped holes of the BOP.
Because normal operations require unrestricted access to the full bore of the BOPs, a bell nipple flange must have a full bore. The pipe size chosen for the bell nipple must have an I.D. at least equal to the BOP stack I.D. See the illustration below.
ANNULAR BOP WITH BELL NIPPLE ASSEMBLY ATTACHED
Both the flange and pipe chosen to make the assembly should have good field weldability. Either low grade ( J ) casing or 36K line pipe works well to fabricate the bell nipple. A “special” flange with a counter bore sized to accept the chosen pipe, a shoulder for the pipe to rest on prior to welding, a taper to guide the bit to center, and a steel chemistry chosen for field weldability, will allow easy and predictable installation. These factors will also facilitate modification of the bell nipple and flange assembly as necessary for BOP connection changes, or when the drilling rig moves to another location.
TYPICAL BELL NIPPLE FLANGE BORES AND TYPICAL COMPATIBLE PIPE TO COMPLEMENT THESE BORES
FLANGE BORECOMPATIBLE PIPE7-1/16″8″ Sch. 40, 36 K line pipe,Some of the above nominal bore flanges can have counterbores that accept either casing or line pipe when these pipe varieties share the same O.D.
Every conventional land drilling rig uses some form of bell nipple flange connected at the top of the blowout preventerblowout preventer ( BOP ) stack. This flange does not hold well pressure, but acts as a fastening device to connect a vertical pipe, referred to as a bell nipple, to the top of the BOP stack. For a typical installation see the illustration below.
TYPICAL BELL NIPPLE AND FLANGE INSTALLATION BELOW DRILLING RIG FLOOR
Operators have chosen many ways to fabricate this assembly of flange and pipe nipple. Sometimes they make the flange from torch cut plate, thin and flimsy, without a ring groove, using a piece of “soft line” in the BOP ring groove to make a seal. Sometimes they use a flange cut from some piece of wellhead equipment.
Often operators fasten the flange to the tapped upper connection of the annular BOP with only 4 bolts, the remaining tapped stud holes in the BOP upper connection left without the protection of tightly engaged tap end studs. The empty tapped stud holes collect water and waste and rapidly deteriorate and become useless. In some cases, operators attempting to protect the tapped holes with short “screwed-in” all thread plugs; find that only drilling in a machine shop will remove the plugs. These common, less expensive installations, may actually have the greatest cost among the available options.
One of the most practical, and over time least costly, bell nipple and flange assemblies, utilizes a full thickness flange, retained with a full set of tap end studs tightly engaged in all the tapped holes of the BOP.
Because normal operations require unrestricted access to the full bore of the BOPs, a bell nipple flange must have a full bore. The pipe size chosen for the bell nipple must have an I.D. at least equal to the BOP stack I.D. See the illustration below.
ANNULAR BOP WITH BELL NIPPLE ASSEMBLY ATTACHED
Both the flange and pipe chosen to make the assembly should have good field weldability. Either low grade ( J ) casing or 36K line pipe works well to fabricate the bell nipple. A “special” flange with a counter bore sized to accept the chosen pipe, a shoulder for the pipe to rest on prior to welding, a taper to guide the bit to center, and a steel chemistry chosen for field weldability, will allow easy and predictable installation. These factors will also facilitate modification of the bell nipple and flange assembly as necessary for BOP connection changes, or when the drilling rig moves to another location.
TYPICAL BELL NIPPLE FLANGE BORES AND TYPICAL COMPATIBLE PIPE TO COMPLEMENT THESE BORES
FLANGE BORECOMPATIBLE PIPE7-1/16″8″ Sch. 40, 36 K line pipe,Some of the above nominal bore flanges can have counterbores that accept either casing or line pipe when these pipe varieties share the same O.D.
Typically, fabrication of the bell nipple and flange occurs at the well site to satisfy measurement taken after setting the conductor pipe or surface casing and installing the BOP stack. Each actual bell nipple fabricated atop the bell nipple flange must meet the requirements of the individual situation, and the operator should have the equipment planned for and ready when needed. When the flange dimension and chemistry, and the pipe dimension and grade satisfies the description above, the bell nipple assembly can experience multiple cut and weld changes without frequent replacement.
WOODCO USA manufactures bell nipple flanges as a standard product with specific material to facilitate field welding and dimensions that protect the BOP.
For more information about API Flanges, click here.
Click here to view the API Flange weight reference chart.
Variable bore blowout preventer rams are a relatively new development. Since these rams increase the flexibility of the ram-type BOP substantially, they have become the subject of considerable current interest. This paper contains general background information on the variable bore ram (VBR), as well as discussions of the advantages and limitations which are to be considered when specifying BOP equipment and when designing and implementing well control procedures using VBRs.
DESCRIPTION
A variable bore ram (VBR) enables a ram-type BOP to close and seal on more than one size pipe. This is in contrast to the standard pipe ram which is designed to seal on only one size pipe. In the standard pipe ram, the elastomeric packing material is supported against extrusion by rigid steel plates which are shaped to fit closely around the pipe. In VBRs the elastomer is contained by a series of segmented inserts which cooperate to conform to any of several pipe sizes as well as tool joints, kellies and other parts of the drill string whose size lies within the range of the VBR.
VBR packers are actuated in the same manner as standard pipe ram packers. The packers extend forward of the ram block faces. When the rams are closed, the packers contact each other on the leading surfaces at the sides of the pipe bore. As the rams continue to close, the elastomer in the packers is displaced inward against the pipe. In standard pipe rams, the packers extend forward of the ram block faces only a fraction of an inch since the elastomer is only required to "feed" inward sufficiently to replace material lost through wear. In the case of the VBR however, much more radial displacement is required. There must be enough displacement to cover the pipe size range of the ram, plus enough to replace material lost through wear. In VBRs, the packers may extend forward of the ram faces an inch or more. There are practical limits to the amount that the packers may extend forward of the ram face. The most obvious limiting factor is the requirement that the ram packers may not extend into the wellbore when the rams are fully retracted. This limits the pipe size range of the VBR, especially in the case where they are designed to fit existing BOPs.
Another factor which limits the pipe size range of a VBR is the width of the ram block, or the width of the packer recess in the ram.
The annular area that can be closed off by the packer is proportional to both the packer width and the distance that the packer extends forward of the ram face. As a result, VBRs for large bore BOPs can have a greater pipe size range than VBRs for small bore BOPs. For example, the maximum pipe size range for the Cameron VBR the 11" bore BOP is 5" to 2-7/8", whereas in the 18-3/4" BOP, the VBR can cover 7-5/8" to 3-1/2" pipe.
Typically, fabrication of the bell nipple and flange occurs at the well site to satisfy measurement taken after setting the conductor pipe or surface casing and installing the BOP stack. Each actual bell nipple fabricated atop the bell nipple flange must meet the requirements of the individual situation, and the operator should have the equipment planned for and ready when needed. When the flange dimension and chemistry, and the pipe dimension and grade satisfies the description above, the bell nipple assembly can experience multiple cut and weld changes without frequent replacement.
WOODCO USA manufactures bell nipple flanges as a standard product with specific material to facilitate field welding and dimensions that protect the BOP.
For more information about API Flanges, click here.
Click here to view the API Flange weight reference chart.
Variable bore blowout preventer rams are a relatively new development. Since these rams increase the flexibility of the ram-type BOP substantially, they have become the subject of considerable current interest. This paper contains general background information on the variable bore ram (VBR), as well as discussions of the advantages and limitations which are to be considered when specifying BOP equipment and when designing and implementing well control procedures using VBRs.
DESCRIPTION
A variable bore ram (VBR) enables a ram-type BOP to close and seal on more than one size pipe. This is in contrast to the standard pipe ram which is designed to seal on only one size pipe. In the standard pipe ram, the elastomeric packing material is supported against extrusion by rigid steel plates which are shaped to fit closely around the pipe. In VBRs the elastomer is contained by a series of segmented inserts which cooperate to conform to any of several pipe sizes as well as tool joints, kellies and other parts of the drill string whose size lies within the range of the VBR.
VBR packers are actuated in the same manner as standard pipe ram packers. The packers extend forward of the ram block faces. When the rams are closed, the packers contact each other on the leading surfaces at the sides of the pipe bore. As the rams continue to close, the elastomer in the packers is displaced inward against the pipe. In standard pipe rams, the packers extend forward of the ram block faces only a fraction of an inch since the elastomer is only required to "feed" inward sufficiently to replace material lost through wear. In the case of the VBR however, much more radial displacement is required. There must be enough displacement to cover the pipe size range of the ram, plus enough to replace material lost through wear. In VBRs, the packers may extend forward of the ram faces an inch or more. There are practical limits to the amount that the packers may extend forward of the ram face. The most obvious limiting factor is the requirement that the ram packers may not extend into the wellbore when the rams are fully retracted. This limits the pipe size range of the VBR, especially in the case where they are designed to fit existing BOPs.
Another factor which limits the pipe size range of a VBR is the width of the ram block, or the width of the packer recess in the ram.
The annular area that can be closed off by the packer is proportional to both the packer width and the distance that the packer extends forward of the ram face. As a result, VBRs for large bore BOPs can have a greater pipe size range than VBRs for small bore BOPs. For example, the maximum pipe size range for the Cameron VBR the 11" bore BOP is 5" to 2-7/8", whereas in the 18-3/4" BOP, the VBR can cover 7-5/8" to 3-1/2" pipe.
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