Dive Planning. Sources Barsky, S.M. 1999. Diving in High-Risk Environments. Hammerhead Press, Santa...

Dive Planning

Sources

• Barsky, S.M. 1999. Diving in High-Risk Environments. Hammerhead Press, Santa Barbara, CA. 198 pp.

• Joiner, J.T. 2001. NOAA Diving Manual: Diving for Science and Technology. Best Publishing Co., Flagstaff, AZ.

• US Department of the Navy. 1999. US Navy Diving Manual. Revision 4. NAVSEA 0910-LP-708-8000. Naval /sea Systems Command, 2531 Jefferson Davis Hwy, Arlington, VA.

Objectives

• Upon completion of this module, the participant will be able to:– State the essential elements of a dive plan– State the advantages and disadvantages of breath-hold diving– State the advantages and disadvantages of open-circuit scuba – State the advantages and disadvantages of umbilical-supplied

systems– State the advantages and disadvantages of closed-circuit

systems– List the responsibilities of NOAA Divemasters– Discuss surface and underwater environmental conditions as

applied to diving– List common diving signals

Objectives (cont)

• Upon completion of this module, the participant will be able to:

– Calculate air consumption rates using RMV– Describe how to determine individual Surface Air Consumption

rates– Describe how to estimate a scuba cylinder duration at depth

The Dive Plan

• Careful planning is the key to an efficient dive operation. The dive plan should include at least the following:– Definition of objectives (clear statement of purpose and goals)– Analysis of pertinent data (e.g., surface conditions, sea state,

temperature, depth, bottom type, tides, currents, visibility, pollution, hazards)

– Assistance and emergency information, including location, status, contact procedures for nearest recompression chamber, air evacuation, US Coast Guard, and nearest hospital

– Diving team selection, including divemaster, medical personnel, tenders/timekeeper, boat operator and surface personnel

– Diving mode selection, e.g., skin/snorkeling, open-circuit scuba, rebreathers, surface-supplied, hookah

The Dive Plan (cont.)– Equipment and supplies selection, such as breathing gas, backup

supply, dive platform, support equipment, oxygen resuscitator, first aid kit, backboard, dive flag, tools, communications, water

– Schedule of operational tasks, including transit to site, assembling dive gear and support equipment, predive briefing, calculating allowable underwater times, recovery, cleaning, inspection, repair, and storage of gear, debriefing of divers and support personnel

– Final preparations and safety checks, including review of dive plan, outline of dive assignments and sequence, complete and post onsite emergency checklist, review divers qualifications and conditions, secure permission from command or vessel captain for dive

– Briefing/debriefing diving team, including the objective and scope of the operation, conditions in the operating area, diving techniques and equipment to be used, personnel assignments, specific assignments for each diver, anticipated hazards, normal safety precautions, any special considerations, group discussion period

Selection of Diving Equipment

• Breath-hold Diving Equipment– Generally used for observation and specimen

collections, photography, or scouting out dive sites in shallow water

– Advantages include: less physical work, simplified logistics, fewer medical/physiological complications

– Disadvantages include: limited in depth and underwater time duration, requires breath-holding techniques, useful only in relatively calm sea conditions

Selection of Diving Equipment (cont.)

• Open-Circuit Scuba– Generally used for scientific observations, light

underwater work, sample collections, and shallow-water research

– Major advantages include: minimum support requirements, mobility, accessibility and economy of equipment and breathing gas, portability, and reliability

– Major disadvantages include: lack of efficient voice communications, limited depth and duration


• Umbilical-Supplied Systems– Generally used for scientific work, ship inspection and

repair, salvage, long-duration data gathering, harsh environments (low visibility, strong currents, polluted water)

– Major advantages include: long duration, voice communications, protection from environment

– Major disadvantages include: limited mobility, significant support requirements


• Closed-Circuit systems– Generally used for observations of long duration– Major advantages include: mixed-gas capability, less

noise or bubbles, conservation of breathing medium, long duration

– Major disadvantages include: complicated maintenance, extensive training requirements, cost of equipment

Dive Team Organization

• NOAA Divemasters have complete responsibility for the safe and efficient conduct of all NOAA diving operations. Responsibilities include:– Preparation of a basic plan of operation, including evacuation and

accident management plans– Liaison with other organizations– Inspection of equipment– Proper maintenance, repair, and stowage of equipment– Selection, evaluation, and briefing of divers and other personnel– Monitoring progress of the operation, and updating requirements as

necessary– Maintaining the diving log– Monitoring of decompression (when required)– Coordination of boat operations when divers are in the water

Dive Team Organization

• The individual diver is responsible for:– Being in proper physical condition– Checking out personal equipment before the

dive– Thoroughly understanding the purposes and

procedures to be used during the dive– Refusing to dive when conditions are unsafe,

when not in good mental or physical condition, or when diving would violate their training or applicable standards

Diving Medical Officer/Diving Medical Technician

• A Diving Medical Officer or Diving Medical Technician shall be assigned to all diving operations

• If not available, then these authorities shall be contacted if required:– Divers Alert Network (DAN) (919) 684-8111 (ask for the

Diving Physician)– Navy Experimental Diving Unit (850) 234-4351– Brooks Air Force Base (210) 536-3278 or (210) 536-3281

Environmental Conditions

• Must be considered when planning a diving operation

• Surface conditions include weather, sea state, and boat traffic– Continuous marine weather broadcasts are provided by

NOAA on the following frequencies depending on the local area:

• 162.40 MHz, 162.475 MHz, or 162.55 MHz• Available from VHF radio or weather radio


• Sea state is generally described on a scale of 0-9, as depicted in the figure below

• Sea states above 4 (moderate seas) should be avoided whenever possible


• Diving operations conducted in harbors, rivers, or shipping channels may pose serious problems

• Display the proper signal flag, shape and lights

Underwater Environmental Conditions

• Diving depth should be determined as accurately as possible• Dive duration, gas requirements, and decompression schedules

should be planned accordingly• Mud bottoms often have suspended sediment in the water• Coral reefs have sharp protuberances - divers need hand and body

protection• If a current exists, a buoyed safety float line at least 100 ft in

length should be deployed from the stern of the vessel• Free-swimming descents should be avoided in a current - use a

down line• Begin the dive into the current so it is easier to return to the entry

point at the end of the dive• Tidal currents should be identified, and if significant, diving should

be done at slack tide

Underwater Environmental Conditions (cont)

• Water temperature determines the type of exposure suit to be worn

• A thermocline, which is an abrupt change in temperature with depth, can occur at any depth, and should be considered in the dive plan

• If underwater visibility is limited, a buddy line or float is recommended

• Contaminated or polluted water may have health hazards– Detailed procedures are described in another module

Diving Signals• Hand signals are used to convey basic

information• Some common signals are shown below

– For a complete list see the NOAA Diving Manual

OK! OK?

OK! OK?Distress (need help)

Diving Signals (cont)

Stop

OK?

Help!

Out of air

Going down

Going up

OK

SomethingIs wrong

Low on air

OK!


Me, orWatch me

WhichDirection?

Ear notclearing

You lead,I’ll follow

What time,What depth?

I don’tunderstand

yes no

Holdhands

Get withbuddy

Lookdown

Slowdown

I amcold

Comehere

Go thatway


• Other types of signals include:– Surface-to-diver, recalling diver from the

water:• Hammer-rapping four times on the boat hull or

suspended steel plate• Bell held underwater and struck four times• Hydrophone, underwater speaker or sound beacon• Strobe flashed four times


• Line signals may be used for surface-supplied diving and for scuba in limited visibility– A list of line pull signals can be found in the NOAA Diving

Manual

• Surface signals may be used to attract attention– Whistle– Flare– Flashing strobe– Flags– Hand/arm signals

Air Consumption Rates

• Respiratory Minute Volume (RMV) is the total volume of air moved in and out of the lungs in one minute

• Actual cubic feet (acf) is the unit of measure that expresses actual gas volume in accordance with the General Gas Law. Actual cubic feet per minute (ACFM) is a consumption rate

• Standard cubic feet (scf) is the unit of measure expressing surface equivalent volume, under standard conditions, for any given actual gas volume. Standard cubic feet per minute (SCFM) is a consumption rate

Calculating Air Consumption Rates

Consumption rate at depth can be estimated by determining the appropriate RMV for the anticipated exertion level and the absolute pressure of the dive depth, using:

Cd = RMV (Pa)WhereCd = consumption rate at depth in scfmRMV = respiratory minute volume in acfmPa = absolute pressure (ata) at dive depth

Calculating Air Consumption Rates

Problem: Compute the air consumption rate for a 50 ft (15 m) dive requiring moderate work, maximum walking speed on a hard bottom (see table 8.5 in NOAA Diving Manual)

Solution:Cd = RMV (Pa)

RMV = 1.1 acfm (from Table 8.5)Pa = 50/33 +1 = 2.51 ata

Cd = (1.1 acfm)(2.51 ata) = 2.76 scfm

Determining Individual Air Consumption Rates

• Surface Air Consumption Rate (SAC) can be used to calculate estimated air consumption rate at any depth– Conduct a dive to a constant depth, and record

beginning and ending pressure gauge readings and elapsed time

– Subtract ending psi from beginning psi– Determine SAC from:

SAC = change in psi/time (depth in ft + 33)/33

SAC Problem

• A diver swims at 30 ft (9 m) for ten minutes. The submersible pressure gauge reads 2,350 psi at the start and 2,050 at the end. What is the diver’s SAC?

SAC = 300 psi/10 min = 15.7 psi/min (30 + 33)/33

• Multiply the SAC by ata to get consumption rate for any depth

Converting SAC from psi/min to ft3/min

• SAC can be converted to RMV using cylinder constants (see Table 8.7 NOAA Diving Manual)

• For example, converting the previous example SAC of 15.7 psi/min, using an aluminum 80 cubic foot cylinder (constant of 0.0266):

RMV = 15.7 psi/min X 0.0266 ft3/psi = 0.42 ft3/min (ACFM)

Scuba Cylinder Duration• Knowing the estimated duration of the scuba air supply is

vital to proper dive planning• For a given scuba cylinder, the ratio of rated volume to

rated pressure is a constant (k):

Scuba Cylinder Duration (cont)

• Air supply duration can be estimated using this equation:

Da = Va/CdWhere

Da = duration in minVa = available volume in scfCd = consumption at depth in scfm

• The available volume depends on the type (rated volume and pressure) and number of cylinders used, the gauge pressure measured, and the recommended minimum cylinder pressure

• Consumption rate depends on the depth and exertion level


• For planning purposes, the available volume of air is the difference between the deliverable volume at a given cylinder pressure and the recommended minimum cylinder pressure (430 psi for steel 72 ft3 and 600 psi for aluminum 80 ft3)

• The available volume can be calculated using:

Va = N(Pg-Pm)k

Where

Va = available volume in scf

N = number of cylinders

Pg = gauge pressure in psig

Pm = recommended minimum pressure in psig

k = cylinder constant


• Estimate the duration of a twin 80 ft3 (2,318 L) aluminum cylinders filled to 2,4000 psig for a 70 ft (21 m) dive for a diver with a RMV of 0.6 acfm

Da = Va/CdStep 1: Determine Va:

Va = N (Pg-Pm)k = 2(2,400 psig - 600 psig) (0.0266 scf/psig)

= 95.8 scfStep 2: Determine Cd:

Cd = RMV (Pa) = 0.6 acfm (70/33 +1) = 1.87 acfm

Step 3: Solve for Da: Da = Va/Cd = 95.8 scf/1.87 scfm = 51.2 min

Surface-Supplied Air Requirements

• Generally the same as for scuba, except where free-flow or free-flow/demand systems are used– Use actual cubic feet per minute instead of

RMV• Demand/Free-flow system has a minimum flow rate

of 1.5 acfm• Free-flow system has a minimum flow rate of 6.0

acfm

Study Questions

• Use the following study questions to review some of the information presented in this self study module. When you are finished you can print out your study questions results.

Self-study Questions

• Which of these underwater conditions should be considered in dive planning?

–a. Tides–b. Currents–c. Visibility–d. All of the above


• According to the NOAA Diving Manual, most diving is performed at depths less than how many feet?

–a. 100 feet–b. 110 feet–c. 120 feet–d. 130 feet


• Which of these are some of the divemaster’s responsibilities?

–a. Maintaining the diving log

–b. Inspection of equipment–c. Safe execution of all diving

–d. All of the above


• The diver is responsible for their own proper physical condition.

–a. True–b. False


• Divers should avoid or limit diving in moderate seas.



• Is a mud bottom more or less limiting to divers?

–a. More limiting–b. Less limiting


• Hand signals are used to convey advanced information.



• Which of these can be used as alternative signaling methods?

–a. Flares–b. Flags–c. Whistles–d. Hand signals–e. All of the above


• The consumption rate at depth can be estimated by determining the appropriate RMV for anticipated exertion level only.



• Which of these factors influence scuba air requirements?

–a. Depth–b. Bottom time–c. Normal ascent time–d. All of the above–e. None of the above


• Are estimations of air-supply requirements for surface-supplied divers the same as scuba divers?

– a. Yes– B. No– c. Yes, except when free-flow

systems are used– D. Yes, except when free-flow systems or

free-flow/demand breathing systems are used


• Breath-hold diving equipment is generally used for shallow-water photography.



• Closed-circuit systems are generally used for observations of short duration.



• Divers should be extremely cautious around underwater wrecks or other structures in low visibility to avoid swimming inadvertently into an area with overhangs.

a. Trueb. False


• Should divemasters review hand signals with all divers?

a. Yesb. No


• Line signals are used as backups to voice communications only.

a. Trueb.False


• Surface-supplied personnel working with a diver should be qualified divers as well.

a. Trueb. False


• Does physiological research yield useful estimates of RMV?

a. Yesb. No

Dive Planning. Sources Barsky, S.M. 1999. Diving in High-Risk Environments. Hammerhead Press, Santa...

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Transcript of Dive Planning. Sources Barsky, S.M. 1999. Diving in High-Risk Environments. Hammerhead Press, Santa...