Glossary
Browse the IADC Lexicon alphabetically or by category. Get comprehensive definitions of drilling industry terms.
MHHW
Definition(s)
MHHW
For regions with semi-diurnal or mixed semi-diurnal tides, the mean of the higher of the two high tides that occur each tidal day, determined over the period of water level observations. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsMHHW
Mean higher high water. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsMarine Growth
Definition(s)
Marine Growth
living organisms attached to an offshore structure. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsMarginal Probability
Definition(s)
Marginal Probability
Statistical distribution (probability) of the occurrence of a variable A that is obtained by integrating over all values of the other variables B, C, … NOTE The marginal probability of A for all values of B, C, … is written as P(A). The concept is applicable to metocean parameters, as well as to actions and action effects. EXAMPLE When considering wave conditions, A can be the individual crest elevation for all mean zero-crossing periods B and all significant wave heights C, occurring at a particular site. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsMarginal Probability
Marginal probability is the unconditional probability of event A, P(A). It is the probability of A regardless of whether event B did or did not occur. If B can be thought of as the event of a random variable X having a given outcome, then the marginal probability of A can be obtained by summing (or integrating, more generally) the joint probabilities over all outcomes for X. Sample Usage: Analysts estimated the marginal probability of a water system contamination, irrespective of the source or type of contaminate. Source: DHS Risk Lexicon, U.S. Department of Homeland Security, 2010 Edition. September 2010 Regulatory GuidanceMarginal Distribution
Definition(s)
Marginal Distribution
statistical distribution (probability) of the occurrence of a variable A that is obtained by integrating over all values of the other variables B, C, … NOTE The marginal probability of A for all values of B, C, … is written as P(A). The concept is applicable to metocean parameters, as well as to actions and action effects. EXAMPLE When considering wave conditions, A can be the individual crest elevation for all mean zero-crossing periods B and all significant wave heights C, occurring at a particular site. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsLong-term Distribution
Definition(s)
Long-term Distribution
probability distribution of a variable over a long time scale NOTE The time scale exceeds the duration of a sea state, in which the statistics are assumed constant (see short-term distribution in 3.29). The time scale is hence comparable to a season or to the design service life of a structure. EXAMPLE Long-term distributions of ⎯ significant wave height, ⎯ significant wave height in the months May to September, ⎯ individual wave heights, ⎯ current speeds (such as for the vortex induced vibrations of drilling risers), ⎯ scatter diagrams with the joint distribution of significant wave height and wave period (such as for a fatigue analysis), or ⎯ a particular action effect. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsHighest Astronomical Tide
Definition(s)
Highest Astronomical Tide
Level of high tide when all harmonic components causing the tides are in phase NOTE The harmonic components are in phase approximately once every 19 years, but these conditions are approached several times each year. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsGust Wind Speed
Definition(s)
Gust Wind Speed
Maximum value of the wind speed of a gust averaged over a short (3 s to 60 s) specified duration within a longer (1 min to 1 h) specified duration NOTE 1 For design purposes, the specified duration depends on the dimensions and natural period of the (part of the) structure being designed such that the structure is designed for the most onerous conditions; thus, a small part of a structure is designed for a shorter gust wind speed duration (and hence a higher gust wind speed) than a larger (part of a) structure. NOTE 2 In practice, for design purposes, the gust wind speeds for different durations (e.g. 3 s, 5 s, 15 s, 60 s) are derived from the wind spectrum. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsGust
Definition(s)
Gust
Brief rise and fall in wind speed lasting less than 1 min NOTE In some countries, gusts are reported in meteorological observations if the maximum wind speed exceeds approximately 8 m/s. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsExtreme Value
Definition(s)
Extreme Value
design value of a parameter used in ultimate limit state checks, in which a structure's global behavior is intended to stay in the elastic range NOTE Extreme events have probabilities of the order of 10−2 per year. Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsDesign Wave
Definition(s)
Design Wave
deterministic wave used for the design of an offshore structure NOTE 1 The design wave is an engineering abstract. Most often it is a periodic wave with suitable characteristics (e.g. height H, period T, steepness, crest elevation). The choice of a design wave depends on ⎯ the design purpose(s) considered, ⎯ the wave environment, ⎯ the geometry of the structure, ⎯ the type of action(s) or action effect(s) pursued. NOTE 2 Normally, a design wave is only compatible with design situations in which the action effect(s) are quasistatically related to the associated wave actions on the structure Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsIMR
Definition(s)
IMR
inspection, maintenance, and repair. Source: API Recommended Practice 17H, Remotely Operated Tools and Interfaces on Subsea Production Systems, Second Edition, June 2013 (Addendum 1, October 2014). Global StandardsICS
Definition(s)
ICS
Industrial control system. Source: DNVGL-RP-G108, Cyber security in the oil and gas industry based on IEC 62443, DNV GL, September 2017. Global StandardsICS
intervention control system. Source: API Recommended Practice 17H, Remotely Operated Tools and Interfaces on Subsea Production Systems, Second Edition, June 2013 (Addendum 1, October 2014). Global StandardsHeave-compensated System
Definition(s)
Heave-compensated System
System that limits the effect of vertical intervention vessel motion on the deployed ROV and ROT system. Source: API Recommended Practice 17H, Remotely Operated Tools and Interfaces on Subsea Production Systems, Second Edition, June 2013 (Addendum 1, October 2014). Global StandardsDWT
Definition(s)
DWT
deep water test. Source: API Recommended Practice 17H, Remotely Operated Tools and Interfaces on Subsea Production Systems, Second Edition, June 2013 (Addendum 1, October 2014). Global StandardsDeployment System
Definition(s)
Deployment System
All equipment involved in the launch and recovery of the ROV and ROT system. Source: API Recommended Practice 17H, Remotely Operated Tools and Interfaces on Subsea Production Systems, Second Edition, June 2013 (Addendum 1, October 2014). Global StandardsCL
Definition(s)
CL
center line. Source: API Recommended Practice 17H, Remotely Operated Tools and Interfaces on Subsea Production Systems, Second Edition, June 2013 (Addendum 1, October 2014). Global StandardsUndrained Condition
Definition(s)
Undrained Condition
Condition whereby the applied stresses and stress changes are supported by both the soil skeleton and the pore fluid and do not cause a change in volume. Source: API RP 2GEO, Geotechnical Foundation Design Considerations, First Edition, April, 2011, Addendum 1, October 2014. Global Standards Source: API Recommended Practice 2GEO, Geotechnical and Foundation Design Considerations, First Edition, April 2015 (Addendum 1, October 2014). Global StandardsSettlement
Definition(s)
Settlement
Permanent downward movement of a structure as a result of its own weight and other actions. Source: API RP 2GEO, Geotechnical Foundation Design Considerations, First Edition, April, 2011, Addendum 1, October 2014. Global Standards Source: API Recommended Practice 2GEO, Geotechnical and Foundation Design Considerations, First Edition, April 2015 (Addendum 1, October 2014). Global StandardsSeabed
Definition(s)
Seabed
Materials below the sea in which a structure is founded. NOTE The seabed can be considered as the half-space below the sea floor. Source:API RP 2EQ, Seismic Design Procedures and Criteria for Offshore Structures, First Edition, November 2014. Global StandardsSeabed
Materials below the sea in which a structure is founded, whether of soils such as sand, silt or clay, cemented material or of rock NOTE The seabed can be considered as the half-space below the sea floor. [ISO 19901-4:2003] Source: API RP 2MET, Derivation of Metocean Design and Operating Conditions, First Edition, November 2014. Global StandardsSeabed
Materials below the sea in which a structure is founded, whether of soils such as sand, silt or clay, cemented materials or of rock NOTE 1 The seabed can be considered as the half-space below the seafloor. NOTE 2 Offshore foundations are most commonly installed in soils, and the terminology in this part of ISO 19901 reflects this. However, the requirements equally apply to cemented seabed materials and rocks. Thus, the term “soil” does not exclude any other material at or below the seafloor. NOTE 3 As yet there are no universally accepted definitions of the various types of soil and rock, see A.6.4.3. Source: API RP 2GEO, Geotechnical Foundation Design Considerations, First Edition, April, 2011, Addendum 1, October 2014. Global Standards Source: API Recommended Practice 2GEO, Geotechnical and Foundation Design Considerations, First Edition, April 2015 (Addendum 1, October 2014). Global StandardsEffective Foundation Area
Definition(s)
Effective Foundation Area
reduced foundation area having its geometric center at the point where the resultant action vector intersects the foundation base level. Source: API RP 2GEO, Geotechnical Foundation Design Considerations, First Edition, April, 2011, Addendum 1, October 2014. Global Standards Source: API Recommended Practice 2GEO, Geotechnical and Foundation Design Considerations, First Edition, April 2015 (Addendum 1, October 2014). Global StandardsDrained Condition
Definition(s)
Drained Condition
condition whereby the applied stresses and stress changes are supported by the soil skeleton and do not cause a change in pore pressure. Source: API RP 2GEO, Geotechnical Foundation Design Considerations, First Edition, April, 2011, Addendum 1, October 2014. Global Standards Source: API Recommended Practice 2GEO, Geotechnical and Foundation Design Considerations, First Edition, April 2015 (Addendum 1, October 2014). Global StandardsWhip Line
Definition(s)
Whip Line
A secondary hoist rope (if present) on a crane. Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsToolbox Talk
Definition(s)
Toolbox Talk
Work team meetings held at the work site prior to the job starting to review potential hazards and discuss aspects of planned operations. NOTE Normally consists of crew members and any supervisor or technical resources required to perform the work. Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsTemporary Crane
Definition(s)
Temporary Crane
aka self-erecting, leapfrog or bootstrap cranes A lifting device that is not part of the original platform design and installed for a specific application or task and will not remain as a permanent part of the facility. NOTE A temporary crane can be certified to API 2C or other justification by engineering analysis, review and materials of construction. Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsTailgate Meeting
Definition(s)
Tailgate Meeting
Work team meetings held at the work site prior to the job starting to review potential hazards and discuss aspects of planned operations. NOTE Normally consists of crew members and any supervisor or technical resources required to perform the work). Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsStatic/Onboard Lift
Definition(s)
Static/Onboard Lift
A crane lifting a load from and to the deck of the platform/vessel that the crane is mounted on. Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsSlewing
Definition(s)
Slewing
Rotation of the upper-structure for movement of loads in a horizontal direction about the axis of rotation. Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsSelf-erecting Cranes
Definition(s)
Self-erecting Cranes
A lifting device that is not part of the original platform design and installed for a specific application or task and will not remain as a permanent part of the facility. NOTE A temporary crane can be certified to API 2C or other justification by engineering analysis, review and materials of construction. Source: API RP 2D, Operation and Maintenance of Offshore Cranes, Seventh Edition, December 2014. Global StandardsSimple Lifts
Definition(s)
Simple Lifts
The following are classified as simple lifting operations:- equipment specifically installed by a crane operator;
- load has known and evaluated weight;
- center of gravity below the lifting point;
- use of a certified lifting point directly above the load;
- ample headroom;
- not sensitive, difficult or in restricted areas;
- use of one crane;
- unlikely to be affected by changing environmental conditions;
- experienced and competent crane operator;
- standard rigging arrangements;
- suitable working area available;
- relevant permits.