US COASTGUARD DP RULES.pdf

Commander

Eighth Coast Guard District

Hale Boggs Federal Bldg.

501 Magazine Street

New Orleans, LA 70130-3396

Staff Symbol: (mvs)

Phone: (504) 589-6271

FAX: (504) 589-4999

16711/DP OSVs

D8(m) Policy Ltr 01-2003

22 January 2003

MEMORANDUM

Subj:

USE OF DYNAMIC POSITIONING (DP) BY OFFSHORE SUPPLY VESSELS (OSVs)

FOR OIL AND HAZMAT TRANSFERS

1. PURPOSE: This letter provides Eighth Coast Guard District (D8) guidance on minimum

requirements for use of a DP system on an OSV for the purpose of “mooring” the vessel during

oil and hazardous material (HAZMAT) transfers to and from an offshore facility or rig on the

Outer Continental Shelf (OCS) within D8. A summary of the guidelines put forth by this policy

letter is provided in enclosures (1) and (2). This policy letter is only intended to apply to OSVs;

and its application to such things as Floating Production, Storage, and Offload (FPSO) units and

their supporting shuttle tankers is specifically excluded from this policy.

2. DIRECTIVES AFFECTED : None.

3. BACKGROUND:

a. 33 CFR 156.120(a) requires that during oil and HAZMAT transfers “the vessel’s

moorings are strong enough to hold during all expected conditions of surge, current and

weather.” This regulation was written for a conventional mooring system or anchoring system

and does not envision the use of DP. However, heightened oil and gas exploration and

production activity in the deepwater regions of the Gulf of Mexico created a demand for OSVs

with DP and a corresponding desire to use DP for “mooring” a vessel during deepwater cargo

transfer operations. Questions have arisen about the use of DP as an acceptable mooring system

for oil and HAZMAT transfers, so this policy letter provides guidance on what minimum

requirements an OSV with DP should meet rather than complying with the mooring requirements

of 33 CFR 156.120(a). It should be noted that there are deepwater installations and OSVs that

are equipped for and employ means of mooring that fully comply with 33 CFR 156.120(a), and

such compliance with the regulation is always acceptable.

b. The definition of an OSV can be found in 46 USC 2101(19) and 46 CFR 125.160. Under

current policy and regulations, vessels meeting the definition of an OSV may be regulated under

various 46 CFR subchapters, specifically Subchapters I, L and T. These vessels are also subject

to the pollution prevention regulations in 33 CFR Subchapter O, and the transfer procedure

requirements in 33 CFR 155.720 stipulate that vessels subject to that regulation must meet the

requirements of 33 CFR 156.120.

16711/DP OSVs

D8(m) Policy Ltr 01-2003

22 January 2003

Subj: USE OF DYNAMIC POSITIONING (DP) BY OFFSHORE SUPPLY VESSELS (OSVs)

FOR OIL AND HAZMAT TRANSFERS

c. In recent years, OSVs have incorporated vessel propulsion and control systems that

provide DP capability of varying degrees. These DP installations have usually been done with

minimal regulatory oversight. In 1994 the International Maritime Organization (IMO) published

Marine Safety Committee Circular 645 (IMO MSC/Circ 645), “Guidelines for Vessels with

Dynamic Positioning Systems,” which defines a DP vessel as follows: “Dynamically positioned

vessel (DP-vessel) means a unit or a vessel which automatically maintains its position (fixed

location or predetermined track) exclusively by means of thruster force.” It also defines a DP

system as “the complete installation necessary for dynamically positioning a vessel comprising

the following subsystems: power system, thruster system, and DP-control system.” An unknown

number of OSVs currently use DP for most, if not all of their OCS facility support activities,

including transfer of oils and hazardous materials.

4. DISCUSSION:

a. A conventional mooring system using mooring lines, as is addressed by 33 CFR

156.120(a), is essentially a passive system such that there is little risk of a “spontaneous” failure

unless the mooring system is overwhelmed by operator error or extraordinary external forces,

such as a severe storm or a powerful wake from a passing ship. Similarly, a DP system can fail if

overwhelmed by excessive external forces that exceed the performance limits of the system.

However, a DP system is an active system with working machinery and many moving parts

controlled by “software,” so a “spontaneous” failure is also possible unless the system has a high

degree of redundancy built into it. Therefore, a DP system must have redundancy if it is to

provide an equivalency to a passive mooring system, since without redundancy the failure of any

piece of machinery or the control system could cause the overall DP mooring system to fail.

b. IMO MSC/Circ 645 addresses redundancy and establishes 3 classes for DP systems:

(1) Class 1 : loss of position may occur in the event of a single fault.

(2) Class 2 : loss of position is not to occur in the event of a single fault in any active

component or system.

(3) Class 3 : loss of position is not to occur in the event of a single failure of any active

or static component or system, and does not occur if all components in one

compartment are lost due to fire or flooding.

The IMO guidelines recommend that the vessel operator and their customer examine the risks

associated with the operation and determine the appropriate class of DP system necessary. The

USCG encourages vessel and facility operators to engage in such discussions, but recognizes that

this communication may not occur in every case. Therefore, this policy will establish minimum

requirements for DP transfers of oil or HAZMAT. The IMO Guideline defines redundancy as

follows:

16711/DP OSVs

D8(m) Policy Ltr 01-2003

22 January 2003

Subj: USE OF DYNAMIC POSITIONING (DP) BY OFFSHORE SUPPLY VESSELS (OSVs)

FOR OIL AND HAZMAT TRANSFERS

“Redundancy means ability of a component or system to maintain or restore

its function, when a single failure has occurred. Redundancy can be achieved

for instance by installation of multiple components, systems or alternative

means of performing a function.”

A summary of IMO’s recommended criteria for each class of DP system is provided in

enclosure (3).

c. Alternative #1 (preferred) – IMO Class 2 or Class 3 DP System : The likelihood of total

failure of the DP system causing a pollution incident due to the vessel drifting off station is very

remote for a vessel equipped with a Class 2 or Class 3 DP system, and even if the DP system

were to fail the DP operator is likely to have ample warning so that transfer operations could be

safely terminated before the vessel were to drift off station. Therefore, a vessel using a DP

system that meets IMO MSC/Circ 645 as Class 2 or Class 3 will be considered acceptable for

meeting the mooring requirements of 33 CFR 156.120(a) for the purpose of conducting oil and

HAZMAT transfers.

d. Alternative #2 – Classification Society “equivalency” to Class 2 or Class 3 : Any DP

system that has been certified by the American Bureau of Shipping (ABS) as “DPS-2” or “DPS-

3”, Det Norske Veritas (DNV) as “AUTR” or “AUTRO,” or Lloyds Register (LR) as “DP(AA)”

or “DP(AAA),” will be considered acceptable for meeting the mooring requirements of 33 CFR

156.120(a) for the purpose of conducting oil and HAZMAT transfers. As shown in enclosure

(4), some of DP criteria of these three classification societies are not as stringent as that

recommended by IMO MSC/Circ 645; however, all of the DP criteria of these classification

societies meets or exceeds the minimum requirements discussed below.

e. Alternative #3 – DP System meeting Minimum Requirements specified in enclosure (2) :

Since the development of DP systems for OSVs has been done with minimal regulatory

participation, there is an unknown number of OSVs in the Gulf of Mexico with DP that do not

fully comply with the IMO recommendations for a Class 2 or Class 3 DP system nor do they

comply with classification society rules. However, many of these OSVs may still have a highly

reliable DP system. In response to this concern a review of IMO’s DP criteria was conducted by

D8 and alternative minimum requirements were developed which are listed in enclosure (2).

These minimum requirements still emphasize the need for redundancy, but acknowledge the fact

that an alternative degree of redundancy is acceptable since long-term station keeping is not

necessary for oil or HAZMAT transfers. The DP system just needs sufficient redundancy so that

if problems occur there will be enough time to safely terminate the transfer operation before the

OSV is likely to drift off station. Therefore, an OSV using a DP system that does not meet the

Class 2 or Class 3 standards but does meet the minimum requirements put forth in enclosure (2)

will be considered acceptable for the purpose of conducting oil and HAZMAT transfers.

f. Alternative #4 - Use of Breakaway Fitting with Quick-closing Valves (for OSVs with DP

systems not meeting any of the above options) : Another option for other DP equipped OSVs is to

16711/DP OSVs

D8(m) Policy Ltr 01-2003

22 January 2003

Subj: USE OF DYNAMIC POSITIONING (DP) BY OFFSHORE SUPPLY VESSELS (OSVs)

FOR OIL AND HAZMAT TRANSFERS

utilize a “fail-safe” transfer system, so that even if the DP system were to fail and the OSV drifts

off station the transfer system will prevent the release of any oil or HAZMAT into the

environment. Therefore, for an OSV with a DP system not meeting any of the above options, the

transfer system may be designed and configured using a breakaway fitting equipped with quick-

closing valves. This must be engineered so that if the DP system were to fail and the vessel were

to drift away from the oil platform or rig, this fitting will be the weak-link in the transfer system

and will part before any other component in the system fails. When the breakaway fitting parts it

must have a quick-closing valve in each half of the fitting (one half which remains connected to

the OSV side of the transfer system and one half which remains connected to the oil platform or

rig) that automatically closes to prevent the release of any oil or HAZMAT. Also, the transfer

system must be designed so that if the breakaway fitting does part and the quick-closing valves

slam shut, the transfer pump has a relief valve and re-circulation piping and/or an automatic

shutdown device to prevent the system from being over-pressurized. If the transfer system is

engineered and configured in this manner then the OSV may conduct oil and HAZMAT transfers

in DP mode.

g. Operational Procedures : Regardless of which option is taken, either the DP system

meets the criteria discussed in paragraphs (c), (d), or (e), or else the transfer system is configured

with a breakaway fitting with quick-closing valves as discussed in paragraph (f), operational

procedures similar to Section 4, “Operational Requirements,” of MSC/Circ. 645, 6 June 1994,

should be developed to address the full range of operational safety issues while conducting oil

and HAZMAT transfers with the vessel in DP mode; and include the applicable surveys and tests

of MSC/Circ. 645, Sections 5.1.1.1, 5.1.1.2, 5.1.1.3, and 5.1.1.4. It shall be the OSV owner’s

responsibility to ensure that all surveys and tests are properly conducted and documented, and the

Coast Guard does not intend to issue a Flag State Verification and Acceptance Document. The

operational procedures for conducting oil and HAZMAT transfers in DP mode may be

incorporated into the transfer procedures required by 33 CFR 155.720, and should include such

things as maximum environmental conditions for the DP system, emergency shut-down and

breakaway procedures, etc. Also, it is strongly recommended that the OSV be positioned so that

if the DP system were to fail, the OSV will drift away from the offshore facility or rig and not

collide with it, and there should be procedures on how the DP operator should assess where to

safely position the OSV with respect to the facility or rig.

h. Training and Qualifications for DP Operators : In addition to having acceptable oil and

HAZMAT transfer procedures that include procedures for transfers while in DP mode, as

discussed above, the licensed deck officer on watch during the DP operations must be suitably

trained and qualified to operate the DP system.

Limitations of Policy Letter:

(1)

Only for OCS in D8: This policy letter applies only to operations in support of the

exploration or exploitation of offshore oil and mineral resources on the OCS within

16711/DP OSVs

D8(m) Policy Ltr 01-2003

22 January 2003

Subj: USE OF DYNAMIC POSITIONING (DP) BY OFFSHORE SUPPLY VESSELS (OSVs)

FOR OIL AND HAZMAT TRANSFERS

D8. Oil or HAZMAT transfer operations occurring on state waters will require the

use of a conventional mooring in accordance with 33 CFR 156.120. This policy

will be forwarded to the Commandant for consideration as a national policy and/or

revision.

(2)

Only for OSVs : This policy letter is only intended to apply to the use of DP by

OSVs transferring to and from an offshore facility or rig, and application to such

things as Floating Production, Storage, and Offload (FPSO) units and their

supporting shuttle tankers is specifically excluded from this policy.

5. ACTION :

A summary of the guidelines put forth by this policy letter is provided in enclosures (1) and (2).

D8 OCMIs are encouraged to distribute this policy letter to OSV owners and operators within

their area of responsibility, so that the OSV owners and operators ensure they comply with this

guidance for oil or HAZMAT transfers by any OSVs using DP. It is not intended that the Coast

Guard will conduct any additional inspection activities to enforce this policy, but the Coast

Guard will consider this guidance when investigating any casualties involving OSVs using DP.

OSV owners and operators are expected to be in full compliance with the provisions of this

policy letter by 22 January 2005, within two years of its effective date.

6. FEEDBACK : Feedback or questions on this policy should be referred to the Eighth Coast

Guard District, D8(m), at 504-589-6271.

Encl: (1) Summary of Compliance Options – OSVs using DP for Oil & HAZMAT transfers

(2) Alternative #3 – Coast Guard’s Minimum DP Requirements for OSVs using DP for

Oil & HAZMAT transfers

(3) Summary of IMO MSC/Circ 645, “Guidelines for Vessels with Dynamic Positioning

Systems”

(4) Summary of Classification Society DP Designations & Criteria

Dist: All Eighth District MSOs, MSU Galveston

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: