New SAWE Recommended Practice Number M-9 Adam (AJ) Bierbauer Supervisor, Waterfront Naval Architecture Shipboard Weight Surveys February 18, 2011

New SAWE Recommended Practice Number M-9

Adam (AJ) BierbauerSupervisor, Waterfront Naval Architecture

Shipboard Weight Surveys

February 18, 2011

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Status and Planned Actions

• Creation of this new Recommended Practice was approved by the Marine Workshop at the 68th International Conference.

• The RP was initially drafted with input from the Northrop Grumman Shipbuilding Newport News, Avondale, and Pascagoula yards.

• The document underwent a 2 month public review period. Comments and suggestions were received from General Dynamics NASSCO, Marinette Marine Corporation, NAVSEA, NSWCCD, ALION Science and Technology, Computer Sciences Corporation-Advanced Marine, and others. Comments and suggestions from all reviewers were incorporated.

• Plan is to obtain SAWE official approval as an approved Recommended Practice before the 70th International Conference in May 2011.

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Status and Planned Actions

The RP will represent the entire shipbuilding and marine services community, relating to all vessel types and survey practices.

•Vessel types including, but not limited to:– Commercial Cargo Vessels and Tankers– Cruise Ships– Fishing Vessels– Offshore Supply Vessels– Ferries

•Survey Practices:– Appropriate level of effort and detail– Storerooms– Personnel, Crew and Effects– Weights to Complete– Spare Parts, Technical Manuals– Contents of Desks, File Cabinets, Bookshelves in Offices

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Overview

• Scope/Objective

• Introduction

• Weight Categories

• Reasons for Surveys

• Conducting the Surveys

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Scope / Objective

• Scope/Objective– Document effective methods and practices.– Relate survey to intended purpose.

• Introduction




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Introduction

• Scope/Objective

• Introduction

Appropriate methods and degree of precision depend on:– Purpose of survey– Size, type, and complexity of ship– Type of space or items being surveyed




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Weight Categories

• Scope/Objective

• Introduction

• Weight Categories– Light Ship - the ship complete, ready for service in every respect,

including permanent solid and liquid ballast, onboard repair parts, and liquids in machinery at operating levels, without any items of variable load (SAWE RP #12)

– Variable Loads – Items which are consumable and subject to frequent change, i.e., all items that are not included in light ship



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Reasons for Surveys

• Scope/Objective

• Introduction


• Reasons for Surveys– Stability Test or Deadweight Determination– Trim Dive– Docking/Undocking


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Surveys are Essential to Stability Tests

• Stability Test or Deadweight Determination– A stability test is conducted to determine a vessel’s light ship

weight and centers of gravity.– A stability test consists of two tasks: the light ship survey and the

inclining experiment.– A deadweight determination is similar except that the vessel is not

inclined, and the vertical and transverse centers of gravity are not determined.

– The safety of the vessel and crew may depend on the accuracy of the test or determination.

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Surveys are Essential to Trim Dives

• Submarine Trim Dive– A trim dive is conducted to determine the weight and longitudinal

center of gravity of the load to submerge.– The load to submerge is the basis for calculating the ballast

needed for the submarine to safely dive and re-surface for various conditions of loading in water of varying density.

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Surveys are Needed for Undocking

• Docking/Undocking Evolutions– Shipboard surveys are conducted to account for the weight of

temporary equipment, material, staging and miscellaneous items.– The information gathered is used to determine the amount and

location of ballast needed to safely float and transfer the vessel.

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Conducting the Surveys

• Scope / Objective

• Introduction



• Conducting the Surveys– Surveys Supporting Stability Tests/Deadweight Determinations

(Light Ship Survey)– Surveys Supporting Submarine Trim Dives– Surveys Supporting Docking / Undocking Evolutions

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Light Ship Survey

• An accurate survey is vital to the accuracy of a stability test or deadweight determination.

• Goal is to obtain a “snap shot” of the vessel’s condition at the time the ship is inclined or the drafts are read.– The ship should be as complete as possible.– Extraneous material should be reduced to a minimum.

• Maintaining the vessel in the desired “pristine” state for the duration of the survey is challenging.

• On some vessels, conducting the survey while underway at sea may be beneficial.

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Light Ship Survey

• Light Ship Survey consists of two parts:– Compartment and Dunnage Survey to compile weights and

locations of dry loads– Liquid Load Survey to determine contents of tanks and status of

system liquids

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Light Ship Survey-Compartment/Dunnage

• Compartment and Dunnage Survey– Must enter all compartments on the ship.– Arrange for entry into locked spaces.– Divide ship into zones considering most efficient routes to

compartments.– Weight data can be obtained from various sources.– Level of detail should be appropriate to size and type of vessel.

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• Compartment and Dunnage Survey– Hangar/Cargo Bays, Flight Decks, Weather Decks– Storerooms– Dry Voids– Personnel, Crew and Effects– Weights to Complete– Spare Parts, Technical Manuals

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• Hangar/Cargo Bays, Flight Decks, Weather Decks– Map items on arrangement drawings.– Take photographs.– Spaces are subject to frequent change – survey near the end.

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• Storerooms– These change frequently – survey last.– Itemize contents whenever practical.– Use density factors when not practical to itemize.

• Dry Voids– May be used as storerooms or contain liquids.– Are often difficult to access.

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• Personnel, Crew and Effects– Minimize number of people aboard during draft readings and

inclining weight movements.– Personnel are to remain in place during draft readings and weight

movements.– Use estimated average weight or weigh each individual person?– Use actual inventory of personal effects or standard allowance?

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• Weights to Complete– Obtain list of missing items from ship project/ship’s crew.– Missing items are easy to overlook. Vessel should be as complete

as possible.– Consider using weight report to prepare lists of outfit/equipment

for individual compartments.

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• Spare Parts, Technical Manuals– Normal allowance is part of light ship weight.– Difficult to identify missing items –load out should be as complete

as possible.– Request list of missing items from ship project/ship’s crew.– Establish a spare parts warehouse to track these items.

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Light Ship Survey-Liquid Load

• Tank Survey– Manual Soundings are required wherever possible.– Tank Level Indicators (TLI’s) are acceptable in some cases.– Visual inspection of empty tanks is preferred.

• System Liquids– System liquids at normal operating levels are part of light ship

weight.– Normal operating level is the preferred condition for a stability test

or deadweight determination.– Status is usually verified by system operators.

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Light Ship Survey-Planning

• Obtain Reference Documents

• Prepare Data Sheets

• Develop Schedule

• Conduct Training Sessions

• Coordinate with Shipboard Personnel

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Submarine Trim Dive Survey

• The trim dive survey is similar to a light ship survey in that it consists of two parts:– A Compartment and Dunnage Survey to compile weights and

locations of dry loads.– A Liquid Load Survey to determine contents of tanks and status of

system liquids.

• Compartment and Dunnage Survey– Should be performed within 24 hours of the trim dive.

• Liquid Load Survey– Performed during the trim dive while the ship is “hovering”.– Utilizes Tank Level Indicators.

• Both surveys can be completed by one person in a single day.

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Docking/Undocking Survey

• Survey is conducted to account for weight changes during period in dry dock.– Survey is primarily focused on temporary material, equipment,

staging, and other dunnage.

• Results assist in ballasting the ship for undocking within acceptable limits of draft, trim, list, and stability.– If comfortable margins exist, survey may be less thorough than a

lightweight survey.

• Process is similar to lightweight survey, except:– Significant work may remain unfinished.– Significantly more temporary material may remain aboard.– Survey may be less thorough and precise.

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Key Lessons Learned

• Effective Planning is essential.

• Seek the highest state of ship completion possible.

• Schedule surveys at times of least activity.

• Support of ship’s crew is essential.

• Identify incomplete work (know what is not there).

• Maintain vessel condition throughout the inclining experiment, deadweight determination, or trim dive.

• Survey hangar bays, weather decks, storerooms last.

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