CHAPTER 4 — Dive Systems 4-1
CHAPTER 4
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4-1
INTRODUCTION
4-1.1
Purpose.
The purpose of this chapter is to promulgate general policy for main-
taining diving equipment and systems.
4-1.2
Scope.
This chapter provides general guidance applicable to maintaining all
diving equipment and diving systems. Detailed procedures for maintaining diving
equipment and systems are found in applicable military and manufacturers oper-
ating and maintenance (O&M) manuals and Planned Maintenance System (PMS)
Maintenance Requirement Cards (MRC).
4-2
GENERAL INFORMATION
4-2.1
Document Precedence.
If a conflict arises between the documents containing the
maintenance procedures for diving equipment and systems, the following actions
are required:
1.
PMS/MRC takes precedence.
2.
If PMS/MRC is inadequate or incorrect, the applicable military O&M manual
takes precedence. Report inadequate or incorrect PMS via a PMS feedback
report in accordance with current PMS instructions.
3.
If PMS/MRC and applicable military O&M manual are inadequate or
incorrect, the manufacturer’s technical manual takes precedence. Report
inadequate or incorrect military technical manual information in accordance
with procedures in the affected technical manual.
Call NAVSEA or NAVFAC prior to disregarding any required maintenance
procedures on certified diving equipment. Failure to do so may compromise
certification.
4-2.2
Equipment Authorized For Navy Use (ANU).
Diving equipment used to conduct
diving operations shall be authorized for use by NAVSEA/00C Diving Equipment
Authorized For Navy Use (ANU) list or hold a current NAVSEA or NAVFAC
system safety certification certificate. Naval Sea Systems Command (Code
00C3B), Supervisor of Diving is the cognizant authority for the NAVSEA/00C
ANU list. Surface supplied diving systems, hyperbaric chamber systems, and
selected free swimming scuba underwater breathing apparatus shall be certified in
accordance with U.S. Navy Diving and Manned Hyperbaric System Safety Certifi-
cation Manual (SS521-AA-MAN-010).
4-2 U.S. Navy Diving Manual—Volume 1
The publication for Continuation of Certification Handbook For U.S. Navy Diving
Systems, (SS521-AB-HBK-010) also provides information concerning main-
taining system certification.
4-2.3
System Certification Authority (SCA).
Naval Sea Systems Command Code 00C4
is SCA for all afloat and portable diving and hyperbaric systems. Naval Facilities
Engineering Command Code 00CE is SCA for all shore-based diving and hyper-
baric systems. Naval Sea Systems Command Code 92Q is SCA for submarine-
employed Dry Deck Shelters and one atmosphere diving systems.
4-2.4
Planned Maintenance System.
Diving equipment shall be maintained in accor-
dance with the applicable PMS package. Failure to maintain equipment in
accordance with current PMS guidance reduces the equipment reliability and may
void the system safety certification for formally certified systems.
4-2.5
Alteration of Diving Equipment.
Diving equipment shall not be modified or
altered from approved configuration unless prior written approval has been
granted by the applicable diving equipment technical program manager.
4-2.5.1
Technical Program Managers for Shore-Based Systems.
Alterations for shore-
based systems are managed by Naval Facilities Engineering Command (Code
00CE), who is the cognizant technical authority for the development and approval
of alterations to shore-based systems.
4-2.5.2
Technical Program Managers for Other Diving Apparatus.
The technical pro-
gram managers for other diving apparatus are:
EX 14 - NAVSEASYSCOM (PMS-395)
MK 16 - NAVSEASYSCOM (PEO-MIW)
MK 20 - NAVSEASYSCOM (SEA 00C)
MK 21 - NAVSEASYSCOM (SEA 00C)
MK 25 (LAR-V) - NAVSEASYSCOM (PMS 325)
Dry Deck Shelter - NAVSEASYSCOM (PMS 395)
4-2.6
Operating and Emergency Procedures.
Operating procedures (OPs) are detailed
check sheets for operating the diving system and for performing various system-
related tasks. All diving and recompression chamber systems shall be operated in
accordance with a set of NAVSEA or NAVFAC approved operating procedures
(OPs) and Emergency Operating Procedures (EPs) and requires the Commanding
Officers or OIC’s signature on the cover page as final review.
4-2.6.1
Standardized OP/EPs.
Standardized diving equipment such as the Light Weight
MK 3 Surface Supplied Diving System, Transportable Recompression Chamber
System (TRCS), and class-certified equipment such as the MK 16 and MK 25
Underwater Breathing Apparatus shall be operated per a single set of standardized
OP/EPs that are included as part of the system O&M Manual.
CHAPTER 4 — Dive Systems 4-3
Proposed changes/updates to OP/EPs for standardized diving equipment shall be
submitted as a formal change proposal to the respective O&M Manual in accor-
dance with directions contained therein.
4-2.6.2
Non-standardized OP/EPs.
Diving and diving support equipment such as ships,
small boats, and unique shore facility surface supplied diving and recompression
chamber systems shall be operated in accordance with a single set of standard OP/
EPs that are developed at the command level and approved for use after validation
by NAVSEA Code 00C3 or NAVFAC Code 00CE. Proposed changes/updates to
OPs/EPs for non-standardized diving equipment shall be submitted to the appli-
cable approval authority. The following addresses are provided to assist in
submitting proposed OP/EP changes and updates.
Submit proposed OP/EP changes and updates for afloat, portable diving and
recompression chamber systems, and class-certified equipment to:
COMNAVSEASYSCOM (Code 00C3)
2531 Jefferson Davis Highway
Arlington, VA 22242-5160
Submit proposed OP/EP changes and updates for fixed, shore-based facilities to:
NAVFAC (Code 00CE)
Washington Navy Yard
901 M Street SE, Bldg. 212
Washington, DC 20374-5054
4-2.6.3
OP/EP Approval Process.
Submission of OPs/EPs for approval (if required) must
precede the requested on-site survey date by 90 calendar days to allow complete
review and resolution of questions. Follow these procedures when submitting
OPs/EPs for approval:
The command shall validate in the forwarding letter that the OPs/EPs are
complete and accurate.
The command must verify that drawings are accurate. Accurate drawings are
used as a guide for evaluating OPs/EPs. Fully verified system schematics/
drawings with components, gas consoles, manifolds, and valves clearly
labeled shall be forwarded with the OPs/EPs.
Approved OPs/EPs shall have the revision date listed on each page and not
have any changes without written NAVSEA/NAVFAC approval.
The command shall retain system documentation pertaining to DLSS
approval, i.e., PSOBs, supporting manufacturing documentation, and OPs/
EPs.
4-2.6.4
Format.
The format for OPs/EPs is as follows:
4-4 U.S. Navy Diving Manual—Volume 1
System: (Name or description, consistent with drawings)
Step, Component, Description, Procedure, Location, Check, Note (read in
seven columns)
4-2.6.5
Example.
System: High Pressure Air
Step/Component/Description/Procedure/Location /Initials /Note
1.
ALP-15/Reducer outlet/Open/Salvage Hold/Initials/Note
2.
ALP-GA-7/Reducer outlet/Record Pressure/Salvage Hold/Initials/Note 1
The operator executing the procedure shall initial the Check column. Hazards and
items of particular concern shall be identified in the Note column.
Once NAVSEA or NAVFAC has approved the system OP/EPs, they shall not be
changed without specific written approval from NAVSEA or NAVFAC.
4-3
DIVER’S BREATHING GAS PURITY STANDARDS
4-3.1
Diver’s Breathing Air.
Divers air compressed from ANU or certified diving
system sources shall meet the U.S. Military Divers Breathing Air Standards
contained in Table 4-1.
Divers breathing air may be procured from commercial sources if a source of
military divers air is not readily available. Divers air procured from commercial
sources shall be certified in writing by the vendor as meeting the purity standards
of FED SPEC BB-A-1034 Grade A Source I (pressurized container) or Source II
(compressor) air. Specifications for this standard are outlined in Table 4-2.
4-3.2
Diver’s Breathing Oxygen.
Oxygen used for breathing at 100-percent concentra-
tions and for mixing of divers breathing gases shall meet Military Specification
Table 4-1. U.S. Military Diver’s Compressed Air Breathing Purity Requirements for
ANU Approved or Certified Sources.
Constituent Specification
Oxygen (percent by volume) 20-22%
Carbon dioxide (by volume) 1,000 ppm (max)
Carbon monoxide (by volume) 20 ppm (max)
Total hydrocarbons (as CH
4
by volume) 25 ppm (max)
Odor and taste Not objectionable
Oil, mist, particulates 5 mg/m3 (max)
CHAPTER 4 — Dive Systems 4-5
MIL-O-27210F, Oxygen, Aviators Breathing, Liquid and Gaseous. The purity
standards are contained in Table 4-3.
4-3.3
Divers Breathing Helium.
Helium used for divers breathing gas shall meet Mili-
tary Specification, MIL-P-27407B Propellant Pressurizing Agent Helium, Type I
Gaseous Grade B, Respirable Helium. The purity standards are contained in Table
4-4.
4-3.4
Divers Breathing Nitrogen.
Nitrogen used for divers breathing gas shall meet
Federal Specification BB-N-411C Nitrogen, Technical. The purity standards are
contained in Table 4-5.
4-4
DIVER’S AIR SAMPLING PROGRAM
NAVSEA Code 00C manages the divers breathing air sampling program in
accordance with OPNAVINST 3150.27 (series). The purpose of the air sampling
program is to:
Provide technical support for the operation and maintenance of diver’s
breathing air compressors and diving air storage systems.
Provide general guidance concerning use of local commercial air sampling
sources, including the evaluation of commercial air sampling capabilities and
equipment.
Perform program management for centrally funded air sampling services as
directed by CNO Code N873D.
Table 4-2. Diver’s Compressed Air Breathing Requirements if from Commercial
Source.
Constituent Specification
Source I
Source II
Oxy
g
en (percent by volume) 20-22%
Carbon dioxide (by volume) 500 ppm (max)
Carbon monoxide (by volume) 10 ppm (max)
Total hydrocarbons [as Methane (CH
4
) by volume] 25 ppm (max)
Odor Not objectionable
Oil, mist, particulates .005 m
g
/l (max)
Separated Water None
Total Water 0.02 m
g
/1 (max)
Halo
g
enated Compounds (by volume):
Solvents 0.2 ppm (max)
Reference: FED SPEC BB-A-1034 B
4-6 U.S. Navy Diving Manual—Volume 1
Collaborate with other government agencies and commercial industry on gas
purity standards and sampling procedures related to divers breathing gases.
4-4.1
Maintenance Requirements.
Taking periodic air samples is a required mainte-
nance action and shall be performed in accordance with the PMS card(s)
applicable to the compressor or system producing diver’s breathing air. Each diver
Table 4-3. Diver's Compressed Oxygen Breathing Purity Requirements.
Constituent Specification
General Note:
Gaseous and liquid oxy
g
en shall contain not less than 99.5% by volume. The
remainder, except for moisture and minor constituents specified below, shall be Ar
g
on and
Nitro
g
en.
Type I Gaseous
Oxy
g
en (percent by volume) 99.5%
Carbon dioxide (by volume) 10 ppm (max)
Methane (CH
4
by volume) 50 ppm (max)
Acetylene (C
2
H
2
) 0.1 ppm (max)
Ethylene (C
2
H
4
) 0.4 ppm (max)
Ethane (C
2
H
6
and other
hydrocarbons)
6.0 ppm (max)
Nitrous Oxide (N
2
O by volume) 4.0 ppm (max)
Halo
g
enated Compounds (by volume):
Refri
g
erants 2.0 ppm (max)
Solvents 0.2 ppm (max)
Moisture (water vapor measured by
ppm or measured by dew point)
7 ppm (max)
>-83°F
Odor Odor free
Type II Liquid
Oxy
g
en (percent by volume) 99.5%
Carbon dioxide (by volume) 5 ppm (max)
Methane (CH
4
by volume) 25 ppm (max)
Acetylene (C
2
H
2
) 0.05 ppm (max)
Ethylene (C
2
H
4
) 0.2 ppm (max)
Ethane (C
2
H
6
and other
hydrocarbons)
3.0 ppm (max)
Nitrous Oxide (N
2
O by volume) 2.0 ppm (max)
Halo
g
enated Compounds (by volume):
Refri
g
erants 1.0 ppm (max)
Solvents 0.10 ppm (max)
Moisture (water vapor measured by
ppm or measured by dew point)
7 ppm (max)
>-83°F
Odor Odor free
Reference: Military Specification MIL-O-27210F
CHAPTER 4 — Dive Systems 4-7
breathing-air source in service must be sampled approximately every 6 months
(within the interval between 4 and 8 months following the last accomplishment),
when contamination is suspected and after system overhaul.
Do not use a compressor that is suspected of producing contaminated air or that
has failed an air sample analysis until the cause of the problem has been corrected
and a satisfactory air sample analysis has been obtained validating the production
of acceptable air.
Diving systems that do not have a high-pressure (HP) air compressor within the
scope of certification shall only be charged with air produced by HP air compres-
sors listed on the ANU list and must have all applicable PMS completed up to
date, including air sample requirements. Examples of these types of systems
include MK 3 LWDS, Roper Cart, and various diving boats. HP banks on these
systems need not be sampled unless contamination is suspected.
Air drawn from submarine HP air storage banks for use as divers breathing air
shall be sampled in accordance with the PMS maintenance requirement card appli-
cable to the system, i.e., dry deck shelter system, submarine escape trunk, scuba
charging station. See paragraph 4-4.2 for additional information on system line-up
for sampling compressors where a sampling connection cannot be made immedi-
ately downstream from the last air filtration device.
Table 4-1 shows the minimum purity requirements for diving air produced by
ANU-approved and certified diving air compressors. Air sampling services may
be procured locally from government or commercial air analysis facilities, or may
be acquired by utilizing analysis services coordinated via Coastal Systems Station
(CSS), Panama City, Florida.
NOTE The most recent air sample analysis report shall be maintained on file for
each air compressor (by compressor serial number) used to produce
divers breathin
g
air.
Table 4-4. Diver's Compressed Helium Breathing Purity Requirements.
Constituent Specification
Helium (percent by volume) 99.997%
Moisture (water vapor) 7 ppm (max)
Dew Point (not
g
reater than) -78°F
Hydrocarbons (as Methane) 1 ppm (max)
Oxy
g
en 3 ppm (max)
Nitro
g
en + Ar
g
on 5 ppm (max)
Neon 23 ppm (max)
Hydro
g
en 1 ppm (max)
Reference: Military Specification MIL-PRF-27407B
4-8 U.S. Navy Diving Manual—Volume 1
4-4.2
General Air Sampling Procedures.
The following general information is pro-
vided to assist commands in managing air sample analysis programs.
Ensure all applicable PMS has been completed on the compressor and associated
filtration system prior to taking an air sample.
When sampling from HP charging systems, separate samples should be taken
from each compressor supplying the system. Samples from the compressors
should be taken as close to the compressor as possible but down stream of the
last compressor-mounted air treatment device (moisture separator, filter, etc.).
Some systems do not have fittings that allow samples to be taken from the
system at a location other than the charging connection. In this case, the
storage flasks should be isolated from the system, the system purged with air
from the compressor to be sampled and the sample taken at the charging
connection.
When sampling from a low-pressure (LP) breathing-air system, separate air
samples shall be taken from each LP compressor connected to the system.
Samples shall be taken from each LP compressor as close to the compressor as
possible, but downstream of the last compressor installed air treatment device
(moisture separator, filter, etc.). Some systems do not have fittings that allow
samples to be taken at connections other than the divers manifold. In this
case, a HP source should be isolated from the LP system, the system purged
with air from the LP compressor to be sampled, and the sample obtained from
the diver’s manifold.
NOTE Failure to pur
g
e the system line-up of air produced from other
compressors or stora
g
e flasks will lead to an invalid air sample for the
compressor bein
g
sampled.
Table 4-5. Diver's Compressed Nitrogen Breathing Purity Requirements.
Class I Oil Free, Type I Gaseous & Type II Liquid
Specification/Grade
Constituent A B C
Nitro
en 99.5% 99.5% 99.5%
Oxy
en 0.05% 0.50% 0.50%
Moisture (water va-
por)
.02 m
g
/l .02 m
g
/l *
Total Hydrocarbons 50 ppm 50 ppm 50 ppm
Odor None None None
* Not a limitin
characteristic
Note:
Type I Nitro
g
en shall not contain any solid particles whose dimensions are
g
reater than 50
microns. This shall be assumed to have been assured by the used of a 10 micron or better nominal
filter at or close to the cylinder char
in
manifold.
Reference: Federal Specification BB-N-411C
CHAPTER 4 — Dive Systems 4-9
Ensure that the compressor being sampled has reached full operating status
(proper operating temperature, oil pressure, and air pressure) and is properly
lined up to deliver air to the sample kit.
Ensure that the compressor’s intake is clear of any potential sources of
contamination (including consideration of ambient smog levels in areas where
smog is a problem).
Follow the procedures on applicable air sample MRC card.
Follow the instructions for operation of the air sampling kit.
4-4.3
CSS Air Sampling Services.
The following applies to centrally funded air
sampling services coordinated by CSS. Due to limited funding, commands are
requested to schedule all compressors and associated samples to be taken at the
same time. CSS coordinates air sampling services with a commercial contractor.
Commands are not authorized to communicate directly with the commercial
contractor. Sampling services are provided at no cost to the command. To request
air sampling services, fill out and fax Air Sampling services request to COAST-
SYSTA (Attn: Air Sampling). Telephone numbers are listed in Appendix 1C.
The user must provide the sample expiration date, the number and type (HP or
LP) of samples required, a complete mailing address, user point of contact and
phone number. Air sample kits will not be shipped until the required
information is received.
Allow a minimum of 5 working days after submitting a properly filled out
request form for delivery of a sampling kit in CONUS. Kits will be sent via
commercial air with a prepaid return mailer. Incomplete sample requests
cannot be acted on and will result in delay of shipping of sample kit.
Allow a minimum of 3 weeks after submitting a properly filled out request
form for delivery of a sampling kit if overseas. Kits will be sent via certified
priority mail for overseas/FPO-APO addressees with prepaid return mailing.
Incomplete sample requests cannot be acted on and will result in delay of
shipping of sample kit.
Detailed instructions are included with each sample kit. It is imperative to
follow those instructions and the instructions on the applicable compressor air
sampling MRC card.
Air samples shall be taken and returned to COASTSYSTA within 5 working
days of receipt of the air sample kit to preclude incurring late fees.
Air sample analysis reports for samples that meet air purity standards will be
mailed to the command. Commands will be notified by quickest means
possible, normally via fax, of any samples that do not meet minimum purity
requirements.
4-10 U.S. Navy Diving Manual—Volume 1
The user will be contacted immediately by phone and/or message by
COASTSYSTA if the sample fails to meet established purity standards. The
user will discontinue use of the air source until cause of contamination is
corrected. Corrective action must be taken prior to laboratory retest.
4-4.4
Local Air Sampling Services.
Commands may use local government (e.g., ship-
yards, ship repair facilities, government research laboratories) or commercial
laboratories to analyze divers air samples. Commands are required to bear the
cost of locally procured air sample services. Local sampling facilities must be able
to analyze to U.S. Navy air purity standards.
4-5
DIVING COMPRESSORS
4-5.1
Equipment Requirements.
Compressors used to supply diving air or transfer
oxygen or mixed gases shall be listed in the NAVSEA/00C Authorized for Navy
use (ANU) list or be an element of a certified diving system.
4-5.2
Air Filtration System.
Military diving compressors shall be equipped with an air
filtration system that is listed in the NAVSEA/00C Authorized for Navy use
(ANU) list or be an element of a certified diving system. The term air filtration
system as used here is inclusive, referring collectively to compressed gas system
filters, moisture separators, air purification, air cooling, and dehydration
equipment.
4-5.3
Lubrication.
Compressors used to produce military divers breathing air are
normally of oil-lubricated, two-to-five-stage reciprocating type. Oil lubrication:
Prevents wear between friction surfaces
Seals close clearances
Protects against corrosion
Transfers heat away from heat-producing surfaces
Transfers minute particles generated from normal system wear to the oil sump
or oil filter if so equipped
A malfunctioning oil-lubricated compressor poses a contamination risk to the
diver’s air supply. Contamination may occur due to excess oil mist being passed
out of the compressor due to excess clearances, broken parts, or overfilling the oil
sump.
Gaseous hydrocarbons and carbon monoxide may also be produced should a
compressor overheat to the point of causing combustion of the lubricating oil and/
or gaskets and other soft goods found in the compressor. Compressor overheating
may be caused by a number of events including, but not limited to: loss of cooling
water or air flow, low lube oil level, malfunction of stage unloader or relief valves,
CHAPTER 4 — Dive Systems 4-11
friction from broken or excessively worn parts, and/or compressor operation at an
RPM above its rated capacity.
Divers air filtration systems are designed to work with compressors operating
under normal conditions, and cannot be relied on to filter or purify air from a
malfunctioning compressor.
WARNING Do not use a malfunctionin
g
compressor to pump divers breathin
g
air
or char
g
e diver's air stora
g
e flasks as this may result in contamination
of the diver's air supply.
Lubricants used in divers air compressors shall conform to MIL-L-17331 (2190
TEP) for normal operations, or MIL-H-17672 (2135TH) for cold weather opera-
tions. Where the compressor manufacturer specifically recommends the use of a
synthetic base oil in their compressor for production of breathing air, that manu-
facturer recommended synthetic base oil may be used in lieu of MIL-L-17331 or
MIL-H-17672 oil. Oil shall be changed out on compressors in strict accordance
with the PMS requirements applicable to that compressor.
4-6
DIVING GAUGES
4-6.1
Selecting Diving System Guages.
Select a gauge whose full scale reading
approximates 130 percent to 160 percent of the maximum operating pressure of
the system. Following this guideline, a gauge with a full scale reading of 4,000 or
5,000 psi would be satisfactory for installation in a system with a maximum oper-
ating pressure of 3,000 psi.
Selecting gauge accuracy and precision should be based on the type of system and
how the gauge will be used. For example, a high level of precision is not required
on air bank pressure gauges where only relative values are necessary to determine
how much air is left in the bank or when to shut down the charging compressor.
However, considerable accuracy (¼ of 1 percent of full scale for saturation diving
operations and 1 percent of full scale for surface supplied operations) is required
for gauges that read diver depth (pneumofathometers and chamber depth gauges).
Depth gauge accuracy is critical to selecting the proper decompression or treat-
ment table.
Many gauges are provided with a case blowout plug on the rear surface. The
blowout plug protects the operator in the event of Bourdon tube failure, when case
overpressurization could otherwise result in explosion of the gauge lens. The plug
must not be obstructed by brackets or other hardware.
All diving system gauges should be provided with gauge isolation valves and cali-
bration fittings. If a gauge fails during an operation, the isolation valve closes to
prevent loss of system pressure.
4-6.2
Calibrating and Maintaining Gauges .
All installed gauges and portable gauges
(tank pressure gauges, submersible tank pressure gauges, and gauges in small
portable test sets) in use must be calibrated or compared in accordance with the
4-12 U.S. Navy Diving Manual—Volume 1
Planned Maintenance System schedule unless a malfunction requires repair and
calibration sooner. Programs such as the Shipboard Gauge Calibration Program as
outlined in the NAVSEA Instruction 4734.1 (series) provide authority for a
command to calibrate its own gauges. Calibrated gauges not in use should be kept
in a clean, dry, vibration-free environment. The Meteorology Requirements List,
NAVSEA OD-45845, should be consulted to determine storage times not consid-
ered part of the calibration interval.
Calibration and comparison data must include the date of the last satisfactory
check, the date the next calibration is due, and the activity accomplishing the cali-
bration. Labels attached to gauge lens are satisfactory for recording this data.
When oxygen systems are being cleaned, gauge lines should be removed and
cleaned separately, after first cleaning the system with gauge lines attached. This
will ensure that the gauge lines are thoroughly flushed. All gauges should be
removed from the system prior to the cleaning process to avoid dead ends in the
system and damage to the gauges from the cleaning solution.
Gauges are delicate instruments and can be damaged by vibration, shock, or
impact. They should be mounted in locations that minimize these factors and
should always be mounted to gauge boards, panels, or brackets. The piping
connection should not be the sole support for the gauge. A gauge can be severely
damaged by rapid pulsations of the system when the fluid pressure is being
measured. When this condition exists, a gauge snubber should be installed
between the isolation valve and the gauge to protect the instrument. Most gauges
are not waterproof and are not designed for use in a marine environment. Enclo-
sures of transparent acrylic plastic, such as lucite, can be used to protect the
gauges from water and salt spray. However, the enclosure must have vent
passages to allow the atmospheric pressure to act on the gauge sensing element.
4-6.3
Helical Bourdon Tube Gauges.
Manufacturers make two basic types of helical
Bourdon tube gauges for use on recompression chambers and for surface-supplied
diving systems. One is a caisson gauge with two ports on the back. The reference
port, which is capped, is sealed with ambient air pressure or is piped to the exterior
of the pressure chamber. The sensing port is left open to interior pressure. The
other gauge is the standard exterior gauge.
Both are direct-drive instruments employing a helical Bourdon tube as the sensing
element. The gauges are accurate to ¼ of 1 percent of full scale pressure at all dial
points. With no gears or linkages, the movement is unaffected by wear, and accu-
racy and initial calibration remains permanent.
A comparative check in lieu of recalibration should be made in accordance with
the Planned Maintenance System. A dial adjustment screw on the front face of the
gauge provides for zero-point adjustment and special set pressure. Dial readout
units of measure can be in pounds per square inch (psi) and/or feet of seawater
(fsw).
CHAPTER 4 — Dive Systems 4-13
4-7
COMPRESSED GAS HANDLING AND STORAGE
Handling and storing compressed gas are inherent parts of virtually all diving
activities, whether conducted with scuba or surface supplied diving equipment. It
is imperative that divers be familiar with the safety aspects of handling
compressed gas. Divers compressed gas shall be stored in military standard
(MIL-STD) or DOT approved cylinders or ASME flasks applicable to the type
and pressure levels of the compressed gas being stored.
Compressed gas shall be transported in cylinders meeting Department of Trans-
portation (DOT) regulations applicable to the compressed gas being handled. DOT
approved cylinders bear a serial number, DOT inspection stamp, a pressure rating,
the date of last hydrostatic test, are equipped with applicable cylinder valve, and
are appropriately color coded.
Refer to the following references for more detailed information on compressed gas
handling and storage:
Industrial Gases, Generating, Handling and Storage, NAVSEA Technical
Manual S9086-SX-STM-000/CH-550
American and Canadian Standard Compressed-Gas Cylinder Valve Outlet
and Inlet Connections (ANSI-B57.1 and CSA-B96).
American National Standard Method of Marking Portable Compressed-Gas
Containers to Identify the Material Contained (Z48.1)
Guide to the Preparation of Precautionary Labeling and Marking of
Compressed Gas Cylinders (CGA Pamphlet C-7).
4-14 U.S. Navy Diving Manual—Volume 1
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