If you are an avid scuba diver, you know how important it is to have a properly filled scuba tank. However, there are certain do’s and don’ts to keep in mind to ensure that your refill is safe and effective.
In this article, we will discuss the key things to consider when refilling your scuba tank, including what to do before, during, and after the refill process. Whether you are a seasoned diver or new to the sport, this guide will help you keep your tank in optimal condition and stay safe on your next dive.
How do you safely refill a scuba tank?
After the end of a dive, you dry off, rinse your gear, and stow it for safe transport. I would suggest that the most neglected piece of equipment after a dive is the scuba tank. It is made of metal and the water just runs off the side walls. By the time you get it to your vehicle, it has dried naturally. Because of these traits, few people pay attention to the cylinder.
You might not need to dry the tank, but removing the cylinders boot, and rinsing / drying will prevent unnecessary corrosion. If you have ever removed your boot, and particles of white debris come off, it is not salt water. It is the beginning stages of corrosion. Cylinder/ Tank boots will trap moisture against the metal, causing the cylinder to corrode over time.
The next part of the cylinder that is neglected is the valve. If the valve is not rinsed, particulates get into the hand wheel and affect the stem and bonnet nut. AND, if you rinse the valve, make certain that you blow out any moisture from the orifice. Failing to blow out the moisture, prior to the next fill, could force water through the valve and into the cylinder. Even small droplets of water entering the cylinder during a filling process can begin the corrosion process.
Most facilities that offer tank fills will get dozens or hundreds of cylinders during the day. The Fill Station Technician is unlikely to crack the valve, blowing moisture out of the orifice, before attaching it to the fill whip. It is recommended that the diver crack the valve as part of their after dive, storage procedure.
When taking the cylinder to an unfamiliar fill station the operator may ask for proof of dive certification. This may offend some seasoned divers, but remember; The fill station owns the compressor, must maintain its rules, and may be held accountable in case there is an incident. That is also why they check the hydrostatic requalification date stamped on the cylinder and look for proof the cylinder has been visually inspected.
Once the cylinder is filled by a trained Fill Station Technician, hook it up to your regulator, or use a hand gauge to ensure that the cylinder has been filled to capacity. The pressure marked on the outside of the cylinder is based on room temperature. If you check the cylinder pressure while the cylinder feels warm, the gauge pressure will drop as the cylinder cools. To ensure your cylinder has been filled to its rated service pressure, it is best to check its internal pressure after the cylinder has cooled to room temperature.
Other considerations when filling a SCUBA tank.
Moisture needs to be prevented from entering the cylinder. One of the frequent ways was mentioned above. Another source of moisture inside the cylinder may be directly from the compressor. If the owner has not changed filters on a regular basis or is failing to dump the moisture at required intervals, moisture can enter a cylinder.
For a more detailed description of this failure read this BLOG on compressors.
How often should a scuba tank be cleaned out?
If moisture enters a cylinder, corrosion develops. The corrosion may take the form of rust on a steel cylinder or appear as a white gelatinous substance in aluminum called aluminum hydroxide. If this aluminum hydroxide dries out, it becomes aluminum oxide, which resembles a white powder. In either case, the cylinder needs to be cleaned out.
The good news is that trace elements of corrosion should not affect the diver, but it should be corrected as soon as possible.