PFD Inspection, Rearming, and Replacement

CO2 Cylinder Inspection — The Heart of the Inflation System

The CO2 cylinder is the component that makes your inflatable PFD work in the critical seconds after you hit the water. A full-size sailing PFD uses a cylinder containing 24 to 38 grams of compressed CO2 (depending on the PFD's buoyancy rating and bladder volume), pressurized to approximately 850 psi. This small metal cylinder must deliver its entire charge in 1-3 seconds through a piercing pin mechanism to inflate the bladder. If the cylinder is underweight, corroded, or improperly seated, the inflation will be partial, slow, or nonexistent.

Weight checking is the primary inspection method and should be performed at least every 2-3 months during the sailing season and before any offshore passage. Every CO2 cylinder has a weight stamped on its body — typically on the base or side, expressed in grams. Using a kitchen scale or postal scale accurate to 1 gram, weigh the cylinder and compare to the stamped weight. If the measured weight is more than 1 gram below the stamped weight, the cylinder has leaked and must be replaced. Do not assume a 1-2 gram deficit is acceptable — even a small loss indicates the seal has been compromised and the remaining gas may be insufficient for full inflation.

Thread condition is the second critical inspection point. The cylinder screws into the inflation mechanism via a threaded neck, and the seal between the cylinder and the mechanism depends on both the thread engagement and a small O-ring or gasket. Examine the threads for corrosion, cross-threading, and salt crystal buildup. Green corrosion on the brass or chrome threads indicates moisture exposure and potential seal degradation. Salt crystals in the threads can prevent proper seating, leading to a gas leak when the cylinder is pierced. Clean threads gently with a soft brush and fresh water if contaminated. Never use lubricant on the threads unless specifically recommended by the manufacturer — some lubricants can degrade the O-ring.

The piercing pin — the sharp point that punctures the cylinder's seal when the mechanism fires — must be inspected for damage, corrosion, and proper alignment. A blunted or corroded pin may not cleanly puncture the cylinder seal, resulting in a slow or incomplete gas release. On most PFD mechanisms, the pin is visible when the cylinder is removed. It should be sharp, clean, and free of corrosion. If the pin shows any damage, the entire mechanism typically needs replacement — the pin is not a separately serviceable part on most designs.

Cylinder dating is less standardized in the PFD world than for life raft cylinders, but many manufacturers stamp or print a date on the cylinder body. While CO2 cylinders don't expire in the traditional sense (the gas doesn't degrade), the metal cylinder itself can develop internal corrosion over time, especially in marine environments. As a practical matter, replace any cylinder older than 10 years even if it still weighs correctly. Replacement cylinders are inexpensive ($15-$30) — cheap insurance for a device your life depends on.

1. Remove the CO2 cylinder

   Unscrew the cylinder from the inflation mechanism by turning it counterclockwise. Some models require removing a cover or clip first — consult your PFD's manual for the specific procedure.

2. Weigh the cylinder

   Place the cylinder on a digital scale accurate to 1 gram. Compare the reading to the weight stamped on the cylinder body. If the measured weight is more than 1 gram below the stamped weight, the cylinder must be replaced.

3. Inspect threads and seal

   Examine the cylinder's threaded neck for corrosion, salt deposits, and cross-threading. Check the O-ring or gasket (if visible) for cracking or deformation. Clean threads gently with a soft brush if needed.

4. Inspect the piercing pin

   With the cylinder removed, look into the mechanism to inspect the piercing pin. It should be sharp, clean, and properly aligned. Any corrosion or blunting requires mechanism replacement.

5. Reinstall the cylinder

   Screw the cylinder back into the mechanism hand-tight. Do not over-tighten — the seal should engage with finger-tight pressure. Verify the mechanism is in the armed position per the manufacturer's indicator (typically a green indicator visible through a window).

Bobbin and Inflator Replacement Schedules

The automatic inflation trigger — whether a water-dissolving bobbin or a hydrostatic inflator unit — has a fixed replacement schedule that is non-negotiable. These components are designed to degrade in a controlled manner (the bobbin literally dissolves on cue), and they have a finite shelf life even in storage. Missing a replacement deadline means you're relying on an automatic trigger that may not fire when submerged, or may fire prematurely from residual moisture. Neither outcome is acceptable.

Halkey-Roberts bobbins are among the most common automatic inflation components in PFDs sold in North America. These small green or white tablets are installed in a spring-loaded cartridge inside the inflation mechanism. When the bobbin dissolves in water, the spring drives the firing pin into the CO2 cylinder. Halkey-Roberts specifies replacement every 3 years from the date printed on the bobbin or cartridge. However, if the bobbin has been exposed to high humidity, spray, or accidental wetting, replace it immediately regardless of the date — partial dissolution weakens the bobbin and can result in either premature deployment or failure to deploy.

UML (United Moulders Limited) is the other major bobbin-based system used in many European-manufactured PFDs including some Crewsaver and Mullion models. UML's replacement interval is also every 3 years. UML bobbins are color-coded by size and are specific to the mechanism — do not substitute a Halkey-Roberts bobbin into a UML mechanism or vice versa. The cartridge assemblies are not interchangeable even though they serve the same function.

Hammar MA1 hydrostatic inflators replace the bobbin with a water-pressure-activated mechanism. The Hammar unit has a longer replacement interval of every 5 years — a significant advantage over bobbin systems in terms of maintenance frequency and cost. The replacement date is printed on the Hammar unit body. Unlike bobbins, the Hammar mechanism is not affected by spray, rain, or humidity exposure (that's its entire design advantage), so the 5-year interval is reliable regardless of conditions. Replacement involves removing the old Hammar unit from the inflation mechanism and installing a new one — a simple procedure that takes under a minute with the instructions provided in the replacement kit.

Track replacement dates by writing them on a piece of tape on the PFD itself (inside the cover, near the mechanism) and in your vessel's safety equipment log. Do not rely on memory — with multiple PFDs aboard, different purchase dates, and different mechanism types, it's easy to lose track. At the start of each sailing season, check every PFD's bobbin or inflator date as part of your commissioning checklist. Replace any component within 6 months of its expiry date rather than waiting for the exact date — the cost is minimal and the margin of safety is worth it.

Bladder Leak Testing and Oral Inflation Tube Maintenance

The bladder is the inflatable chamber that provides buoyancy — it's a welded nylon or polyurethane envelope that must hold gas pressure for hours in a survival situation. A bladder with a slow leak may inflate fully when the CO2 fires but gradually deflate over the following hours, eventually losing enough buoyancy to drop the wearer's head below water level. This is an insidious failure mode because the PFD appears to work when first deployed but fails over time when the wearer may be exhausted, hypothermic, or unconscious.

Perform a leak test at least annually and before any extended offshore passage. The procedure is straightforward: fully inflate the PFD using the oral inflation tube (not the CO2 cylinder — save that for emergencies). Inflate the bladder until it's firm, then leave it inflated for 12-24 hours in a warm, indoor environment. After the waiting period, check the bladder pressure by squeezing it — any noticeable softness indicates a leak. For a more precise test, measure the circumference of the inflated bladder with a tape measure at a consistent point immediately after inflation and again after 12 hours. A reduction of more than 1-2 cm suggests a leak that needs investigation.

If a leak is detected, the most common sources are: the oral inflation tube valve (the one-way valve that allows you to blow air in but prevents it from escaping), the CO2 cylinder connection point (where the mechanism seats against the bladder inlet), and seam welds in the bladder fabric itself. Submerging the fully inflated bladder in a bathtub or basin and watching for bubbles can help localize the leak. Small seam leaks can sometimes be repaired with a manufacturer-approved patch kit, but any significant bladder compromise warrants replacement of the entire PFD — this is not a component you want to trust a DIY repair on in a survival situation.

The oral inflation tube requires its own maintenance attention. Salt crystals can accumulate inside the one-way valve, preventing it from sealing properly (causing a slow leak) or from opening at all (preventing oral inflation). After every exposure to salt water — and periodically throughout the season even without immersion — flush the oral tube with fresh water by blowing fresh water through it and then allowing it to dry completely. Test the valve by inflating the bladder partially through the tube and verifying it holds pressure for at least several hours. If the valve leaks or sticks, replacement tubes are available from the PFD manufacturer.

While the bladder is inflated for testing, take the opportunity to inspect the entire bladder surface for damage. Look for abrasion marks, punctures, UV degradation (indicated by color fading or surface cracking), and any areas where the inner coating appears to be peeling or delaminating. Run your hands over the entire surface feeling for irregularities. Pay particular attention to areas where the bladder contacts the PFD's outer cover, harness hardware, or the inflation mechanism — these are high-wear points.

Fabric, Stitching, and Harness Inspection

While the inflation system gets most of the maintenance attention, the outer cover, stitching, and harness components of your PFD are equally critical to its function. A PFD with a perfectly functioning inflation system but a failed harness buckle or torn cover is not a reliable piece of safety equipment. These external components are subject to UV degradation, salt crystallization, chafe, and physical abuse from daily use — and they degrade visibly in ways that you can inspect without any special tools.

UV damage is the primary enemy of the outer cover fabric and stitching thread. A PFD worn on deck through a full sailing season absorbs enormous UV exposure — far more than gear stored below decks. The signs of UV degradation are color fading (the first visible indicator), followed by thread weakening (stitching becomes easy to pull apart with finger pressure), and eventually fabric embrittlement (the cover tears when flexed). Check the stitching at every seam, particularly around the harness attachment point, the inflation mechanism housing, and the areas where the bladder exits the cover. If any stitching pulls apart with moderate finger pressure, the PFD needs professional repair or replacement.

Salt crystal buildup is a pervasive problem on PFDs used in offshore sailing. Salt crystals accumulate in fabric weave, inside buckle mechanisms, around the inflation mechanism, and in the oral inflation tube. Beyond the corrosion risk, salt crystals act as abrasives — every time you flex or fold the PFD, the crystals grind against the bladder fabric and stitching. Rinse your PFD thoroughly with fresh water after every passage or significant spray exposure, and allow it to dry completely before stowing. This single maintenance step dramatically extends the life of every component.

The harness webbing and buckle must withstand the shock loads generated when a tethered crew member falls overboard and is jerked to a stop. These loads can exceed 900 kg (2000 lbs) in a worst case — enough to break substandard hardware. Inspect the harness webbing for cut fibers, edge fraying, UV fading, and any areas of chemical contamination (fuel, solvents, battery acid). The buckle should engage and release positively with no hesitation. Test the buckle repeatedly — engage, load it by pulling the webbing taut, release. If the buckle is sluggish, stiff, or inconsistent, replace it or replace the PFD. The D-ring or attachment point where the tether clips should be free of corrosion, cracks, or deformation.

Reflective tape on your PFD is a survival feature, not decoration. SOLAS-grade retroreflective tape (typically 3M Scotchlite) makes you visible to searchlights and flashlights at distances far beyond what your PFD light alone can achieve. Inspect the reflective tape for peeling, delamination, and loss of reflectivity. Test by shining a flashlight at the tape in a dark room — fresh tape returns a bright, crisp reflection, while degraded tape appears dull or patchy. Replacement tape is available in rolls and can be applied by the owner using contact adhesive or the tape's self-adhesive backing.

Rearming After Deployment and End-of-Life Replacement

Whether your PFD deployed in an actual emergency, a training exercise, or an accidental inflation from spray, it must be completely rearmed before it can be relied upon again. Rearming is a straightforward process — essentially replacing the spent CO2 cylinder and the triggered bobbin or inflator — but it must be done correctly or the PFD will not function at the next deployment. Most PFD manufacturers include rearming instructions inside the cover, and rearming kits are available from chandleries and directly from the manufacturer.

Step-by-step rearming proceeds as follows: First, deflate the bladder by opening the oral inflation tube valve and pressing the bladder flat to expel all gas. Roll the bladder to squeeze out residual gas. Second, remove the spent CO2 cylinder by unscrewing it from the inflation mechanism. Inspect the mechanism — the piercing pin should have a clean puncture mark on the cylinder seal, confirming a clean firing. Third, remove the spent bobbin or Hammar unit. For bobbin systems, the dissolved bobbin remnants should be visible in the cartridge. For Hammar units, the mechanism will be in the fired position. Fourth, install a new bobbin/Hammar unit per the manufacturer's instructions. Fifth, install a new CO2 cylinder, screwing it in hand-tight. Sixth, verify the mechanism is in the armed position — most mechanisms have a visible indicator (green dot, red/green window, or a specific pin position). Finally, refold the bladder according to the manufacturer's folding diagram and close the PFD cover.

Refolding the bladder correctly is important for proper deployment. The bladder must be folded so that it deploys symmetrically and doesn't tangle with the harness or cover during inflation. Each PFD model has a specific folding sequence illustrated in the manual. If you've lost the manual, contact the manufacturer for a replacement or find the folding diagram online. A poorly folded bladder may still inflate (the CO2 pressure will force it open regardless of folding) but may inflate in a lopsided or tangled configuration that reduces buoyancy effectiveness.

Typical lifespan for an inflatable PFD is 10 years from the date of manufacture, though this varies by manufacturer and usage conditions. Spinlock recommends a maximum service life of 10 years. Mustang and Crewsaver have similar guidelines. After 10 years, even a PFD that passes all inspections may have internal degradation in the bladder material, inflation mechanism components, or harness webbing that is not detectable through normal owner inspection. The conservative approach is to retire and replace any inflatable PFD at or before the manufacturer's stated end-of-life, regardless of its apparent condition.

Storage between uses significantly affects PFD lifespan. Store inflatable PFDs hanging in a ventilated locker where air can circulate around the entire garment. Never compress an inflatable PFD under heavy gear, fold it tightly into a small space, or store it in a sealed plastic bag (which traps moisture). Avoid storage locations exposed to direct sunlight, extreme heat (above a hot engine compartment, in an unventilated lazarette in the tropics), or chemical fumes. Humidity is the enemy of water-dissolving bobbins — even a PFD stored in a humid locker can experience bobbin degradation. If you use a Hammar hydrostatic inflator, humidity during storage is not a concern for the trigger mechanism, but it still promotes corrosion on the CO2 cylinder and mechanism metal parts.

1. Deflate the bladder completely

   Open the oral inflation tube valve and press the bladder flat, rolling from the far edges toward the valve to expel all gas. Ensure the bladder is fully deflated before proceeding.

2. Remove the spent CO2 cylinder

   Unscrew the spent cylinder counterclockwise from the inflation mechanism. Inspect the piercing pin for a clean puncture mark on the cylinder seal.

3. Remove the spent bobbin or Hammar unit

   Detach the spent automatic trigger component. For bobbins, note the dissolved remnants. For Hammar units, note the fired position of the mechanism.

4. Install the new automatic trigger

   Install a fresh bobbin cartridge or Hammar MA1 unit per the manufacturer's instructions. Ensure it seats fully and the mechanism engages correctly.

5. Install the new CO2 cylinder

   Screw the new cylinder into the mechanism hand-tight. Verify the arming indicator shows the mechanism is in the armed/ready position.

6. Refold the bladder and close the cover

   Fold the bladder according to the manufacturer's folding diagram. Tuck it neatly into the PFD cover and secure all closures. Write the rearming date and next replacement dates on a label inside the cover.