TEORÍA DE RESTRICCIONES
4.3 THROUGHPUT ACCOUNTING
1. Boat landings, associated connections and local framing shall be designed for boat impact loads (as specified in Appendix B), environmental loads, uniform live loads, and dead loads.
2. Boat landings shall be two levels.
a. Mooring bollards shall be provided on the jacket structure near each end of the boat landing for supply vessel mooring.
b. Removable handrails shall be provided on the interior side of the boat landing.
c. A removable ladder shall be provided on each side of the boat landing to facilitate personnel movement from the water to the boat landing walkway.
d. The bottom rung of the ladder shall be level with the bottom of the boat landing.
e. A stairway shall be provided between the boat landing and the jacket walkway.
f. Swing ropes shall be provided to facilitate personnel movement between vessels and the boat
3. All vertical posts along the berthing face shall be protected from abrasion by vessel contact by replaceable rub strips.
4. Center-to-center spacing between the vertical posts shall not exceed 3 feet (0.9 m).
5. For field-installed boat landings, the boat landing, and its interface with other platform appurtenances and equipment, shall be designed to allow for +/- 4 feet (1.2 m) of vertical adjustment in the field at the time of platform installation.
6. The +/- 4 feet (1.2m) vertical adjustment tolerance is to allow for water depth and platform on-bottom setting uncertainties.
7. If requested by Purchaser, boat landings shall be designed to accommodate small “surfer”
vessels used primarily for personnel transfer. (This is a typical requirement in areas such as West Africa.)
7.2 Barge Bumpers
1. Barge bumpers, associated connections, and local framing shall be designed for boat impact loads as specified in Appendix B.
2. Barge bumpers shall be removable and mounted on shock cells.
3. The barge bumper total vertical design height or explicit provision for field adjustment shall be consistent with the water depth and platform on-bottom setting uncertainties specified for boat landings in Section 7.1.
7.3 Riser Guards
1. Riser guards, associated connections, and local framing shall be designed for boat impact loads as specified in Appendix B.
2. Where there is a plan for future riser installation, riser guards shall be designed to swing from one end to allow for installation of the future risers.
3. Large riser guards that cannot be effectively designed to swing from one end shall be designed with stabbing guides so that they can be removed and reinstalled or replaced if necessary.
7.4 Riser Clamps
1. Riser clamps shall be designed to withstand all environmental and operating loadings including pipeline thermal expansion and surge.
2. Riser clamps shall include a neoprene liner.
3. In the design of riser clamps, Supplier shall consider that clamps rigidly attached to risers are believed to exhibit a shorter fatigue life than clamps designed with larger annular gaps, which are somewhat more flexible.
7.5 Sumps and Pump Casings
1. Sumps and pump casings and their supports shall be designed to withstand all environmental and operating loadings.
2. The bottom elevation shall be determined to satisfy process design.
3. Jacket supports for “skim pile” sumps shall be designed to allow vertical adjustment after jacket installation to match the jacket installation vertical tolerances (for example, the skim pile elevation relative to sea level must be adjustable to maintain full operability of the skim pile).
7.6 Walkways, Stairways, and Landings
1. Walkways, stairways, and landings shall be designed for a uniform live load of 100 psf (500 kg/m2) or a 1000-pound (450 kg) moving, concentrated load, whichever is more severe.
2. Walkways in high-traffic areas and primary means of egress shall have a minimum clear width of four feet (1.2 m).
a. All walkways, stairways, and landings shall have a minimum clear width of 3 feet (0.9 m).
b. Platform stairway and associated landings and egress paths shall be designed to
accommodate two men carrying an injured person on a stretcher from the boat landing to the helideck.
c. All walkways, stairways, and landings shall meet SID-SU-5106 requirements.
7.7 Containment, Curbs, Handrails, Kick Plates, and Ladders
1. Handrails and kick plates shall be provided around the perimeter of each deck (except the helideck) and on both sides of stairways.
a. Where containment of liquids is desired, a pollution curb shall be used.
b. If containment of liquid is desired, the handrail kick plates shall be welded directly to the deck plate. The height of the kick plate shall be a minimum of 4 inches (100 mm).
c. Where handrails are not present, the liquid containment shall be provided by welding half of an 8-5/8 inch (219 mm) tubular to the floor system.
d. This same detail shall be used where a containment area crosses walkways stairs, etc.
2. Handrails and supports shall be designed to withstand a lateral or vertical concentrated load of 200 pounds (90 kg) applied at any point on the handrails.
3. The ladder design load shall be determined by the usage of the ladder, but shall not be less than a single concentrated load of 300 pounds (135 kg).
4. Number and location of the ladders between the main deck and cellar deck, or between the cellar deck and top of the jacket, shall be based on HSE and HAZOP studies and requirements.
5. The ladder shall be located remote from other deck-to-jacket stairways.
6. All containments, curbs, handrails, kick plates, and ladders shall meet SID-SU-5106 requirements.
7.8 Crane Pedestals
1. Crane pedestals and the supporting structure shall be designed in accordance with API RP 2AWSD and/or API RP 2A-LRFD, as applicable.
2. The supporting structure is defined as the pedestal and all primary members directly attached to the pedestal.
3. Bearing in mind that crane pedestals are commonly used for diesel storage, the liquid loads and the location of the access manhole shall be considered in the design of the pedestal.
7.9 Conductor Guide Framing
1. The criteria in Table 17 govern the design of the conductor guide framing when the conductors are installed using the drilling rig.
a. These criteria shall be considered for the design of the conductor guide framing.
b. These criteria are in addition to the consideration of loads imposed by pre-installed conductors.
2. The criteria in Table 18 govern the design of conductor guide framing when conductors are supported off the top jacket elevation during installation.
a. As a minimum, these criteria shall be considered for the design of conductor guide framing.
b. The design shall not practically restrict the number of locations that may be worked at one time.
c. The criteria shall be in addition to the consideration of loads imposed by preinstalled conductors.
3. The top level of conductor guide framing shall be designed to minimize surface area and enhance maintainability.
4. The conductor guides at the top of jacket level shall have no cavities where water may be trapped.
5. The design shall include conductor guides and framing at the mudline elevation unless pre-drilled wells are present.
6. If pre-drilled wells are used, Supplier shall request design guidance from Purchaser.
7.10 Skirt Pile Guide Framing 7.10.1 Battered Skirt Piles
1. The design of skirt pile framing for battered skirt piles shall consider the loads imposed during the installation of the piles.
2. As a minimum, the criteria in Table 19 shall be considered for the design of the skirt pile guide framing.
Table 17: Load Criteria for CGF – Conductor Installed by Rig
Top level 1.5 times the weight of the string that will initially pass this level.
Second level 1.5 times the weight of the string that will initially pass the second level.
Subsequent levels 0.5 times the weight of the string that will initially pass these levels.
Table 18: Load Criteria for CGF – Conductor Supported by Jacket
Top level 1.1 times the weight of the heaviest string to be supported from this level, or 1.5 times the weight of the string that will initially pass this level, whichever is greater.
Second level 1.5 times the weight of the string that will initially pass the second level.
Subsequent levels 0.5 times the weight of the string that will initially pass these levels.
Table 19: Criteria for Design of Battered Skirt Pile Guide Framing
Top level A vertical load equal to 1.1 times the weight of the heaviest string to be supported from this level, or 1.5 times the weight of the string that will initially pass this level, whichever is greater.
Second level A vertical load equal to 1.5 times the weight of the string that will initially pass the second level.
Subsequent levels A vertical load equal to 0.5 times the weight of the string that will initially pass these levels.
7.10.2 Vertical Skirt Piles
1. The design of skirt pile guides for a one-piece, vertical skirt pile shall consider the loads imposed during the installation of the piles.
2. As a minimum, the criteria in Table 20 shall be considered for the design of the skirt pile guide framing.
7.11 Flooding and Grout System
1. The flooding and grouting system shall be designed to have primary and secondary systems, which shall be separated to preserve utility in case of damage to the primary system.
2. The system shall be fully detailed to allow fabrication from the design drawings.
3. Flooding and grout lines shall be designed for transportation loads and, where applicable, launch loads. Particular attention shall be paid to wave slam during launch.
4. When underwater hammers will be used, flooding and grout piping systems shall be designed to resist severe impact forces.
5. Special attention shall be paid to the appurtenances attached directly to the pile sleeves as these will have the highest accelerations.
6. Piping supports in the splash zone shall be minimized.
7. To permit easy removal of the lines, the design of the flood and grout line supports shall consider that when no longer needed, the flood and grout lines and supports shall be removed down to el. −25 feet (−7.5 m).
7.12 Bridge
7.12.1 Support Conditions
1. Bridges shall be designed to accommodate transverse and longitudinal differential platform movement between the two platforms supporting it. Predicted maximum relative deflection shall be calculated based on a worst-case situation; i.e., the sum of the maximum absolute deflections of the adjacent platforms.
2. Detailing of the hinged and sliding ends shall include a stopper to prevent the bridge from coming out of the supports and sliding off the deck. The sliding ends shall also accommodate the predicted maximum relative displacements (combined x and y directions).
3. One end of the bridge shall be designed as a hinged support and the other end as a sliding support.
4. The sliding support shall provide guide restraints in the vertical and lateral directions.
5. The sliding support shall be a self-lubricating bearing element.
Table 20: Criteria for Design of Vertical Skirt Pile Framing
Skirt pile guides A lateral load equal to 0.2 times the weight of one skirt pile shall be supported by the skirt pile guide.
Skirt pile sleeve A vertical load equal to 1.1 times the weight of one skirt pile shall be supported on the top of a skirt pile sleeve for the worst skirt pile location to assess the jacket stability and structural integrity of the jacket, including the skirt pile sleeve framing, jacket leg, and mudmats.
6. One hundred fifty percent of the total predicted translation shall be allowed for in the end connection and bridge design.
7. The hinged connection shall be designed to withstand 150 percent of the expected axial thrust.
8. Bridge supports shall be capable of accommodating a 2.5-foot (750 mm) tolerance in all directions for final platform location, except when the bridge length is adjusted after measurement of actual distance between platforms.
7.12.2 Deflections
1. The maximum deflection of the bridge due to bridge live load shall be limited to L/300 where L is the distance between bridge support points.
2. The bridge shall be designed to be fabricated with a built-in camber so that it will remain level after installation when loaded with the structural weight, commodities weight, and operating contents.
7.13 Vent and Flare Booms
1. Thermal stresses and steel strength reduction from radiant heat shall be considered in the design of flare booms.
2. Flare boom design shall consider thrust-induced loading.
3. For all structures, wind-induced fatigue and vortex shedding shall be considered.
4. For booms installed offshore, the boom connection shall be designed so that the boom is self-supporting prior to welding out.
5. Consideration shall be given to sealing the hook joint with cover plates after the vent boom is installed to avoid future corrosion.
7.14 Helideck
Refer to CIV-SU-1.28.
7.15 Mudmats
1. Steel mudmats shall be provided, unless Purchaser has accepted an alternative.
2. Attempts shall be made to design the mudmats such that they can be fabricated on the ground and then installed using a limited amount of welding.
3. The use of crimped or corrugated plate shapes is an acceptable alternative to beam and plates if the reduction in fabrication and welding cost justified their use.
4. If mudmat knee braces connect to primary jacket braces, they shall be modeled in the in-place analysis. Joint cans or doubler plates shall be used where the knee braces connect to the primary braces.
5. Knee braces attached to the jacket legs shall have doubler plates. The jacket legs shall be checked at these locations for punching shear stresses as well as ovalling.
6. For a large platform, Supplier shall consider a full stress analysis of the jacket structure using a jacket model that includes all mudmat framing and bearing loads from the soil.
a. The jacket should be analyzed first with supports at the center of each mudmat with appropriate environmental loads and pile loads applied.
b. The reactions from this analysis are then applied to a jacket model where it is supported at the top and the mudmat loads are applied at the bottom acting vertically upwards.
c. This allows the designer to check and document the stresses in all members of the jacket more thoroughly and reduces the requirement of manual design checks.
7.16 J-Tubes
1. J-tubes and their support framings shall be designed to withstand pipeline pulling forces.
2. Mudline detailing at the entrance of the J-tube shall have gradual slope to minimize the incoming pipeline span.
3. Above every J-tube, a padeye shall be provided on the underside of the deck with a capacity equal to twice the estimated pulling force.
4. If a hatch opening is provided where the pipe can be pulled from the main deck, then padeyes shall not be required.
7.17 Installation Aids
1. Installation aids shall be designed for functional, reliable, and safe installation procedures.
2. All installation systems such as grout lines, inflation lines for packers, release mechanisms, etc., shall have a 100 percent back-up system.
3. All top-of-jacket and splash zone installation systems shall be designed for ease of removal.
4. Flood, grout, and inflation lines shall be placed inboard of the jacket framings and secured properly to withstand installation forces resulting from loadout, transportation, launch/lift, and pile driving.
5. For an ROV-assisted installation where an ROV will be used to operate valves, provisions shall be made to provide a reaction point for the ROV to grab onto with one manipulator in order to stabilize the vehicle while work is being performed by the other.