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Crossfire Hydrotesting
and Resurfacing
By Bill Mills - Photos by Dawn Mills - Jul 2006

For several years now Crossfire, has been producing fixed output screw-in compressed air systems for paintball.  With screw-in air systems there is always a concern that the regulator has to stay secured to the tank when the whole system is unscrewed from the paintgun.  For this reason Crossfire has always recommended that their air systems be sent to them when the time comes for hydrotesting.  Previously they would remove and inspect regulators before having a tank tested by a subcontractor, but now they have gone a step further, to offer in house hydrotesting and tank refinishing.

Federal regulations give the Department Of Transportation (DOT) authority when it comes to the transport of hazardous materials, including compressed gasses.  Through inspection at the manufacturing plant and overpressurizing samples to find their point of failure, the DOT hazmat exemption program provides oversight to make sure that the tanks we use for CO2 and compressed air are tough enough to hold the pressures they face during normal use.

When a tank is manufactured, it is stamped or labeled (depending on the type of tank) with the date of manufacture, the DOT HAZMAT exemption number under which it was manufactured, and identification information about the manufacturer.  For most tanks, this certification has a limited lifespan before they must be retested.

Some of the more conscientious manufacturers of fiber wrapped compressed air tanks will include re-test information in their label, with a statement like “retest every 5 years.”  That is the length of time for which the exemption is valid.  After that time period, the tank may not be filled (there are legal penalties for filling and transporting a tank that is no longer under an exemption) until it has been re-certified.  For tanks which don’t state how often they must be tested, this information can be found by looking up their exemption number at 

In general, many of the smaller aluminum CO2 tanks do not require retesting, while larger CO2 tanks like 20 ounce sizes must be retested every five years – though many players opt to simply replace them, since that is often less expensive than retesting.  

For fiberglass or carbon fiber wrapped HPA cylinders on the other hand, with their higher price tag, retesting is much more affordable and must be performed every 3 or 5 years, depending on the particular tank model’s exemption.

Determining when a cylinder needs retesting requires finding both how often retesting is required, and knowing when the tank was made.  The tank’s month and year of manufacture will always be on the tank, with the manufacturer’s initials or symbol between them.  

Living in an area full of SCUBA divers, finding a hydrotester locally, is not all that difficult.  Surprisingly when Crossfire announced their hydrotesting service, their price  was almost 50 percent less than having it done locally – a little lower than or break even when considering the cost of shipping.  A few older tanks made the trip up to Kalamazoo to be re-certified, along with a newer tank to try out their new “spa service.”

The process of hydrotest re-certification involves first removing the regulator from the cylinder.  This is why it can be advantageous to use a hydrotester that specializes in paintball tanks – unlike SCUBA or SCBA oriented hydrotesters, they will already be familiar with the paintball regulators and the fittings needed to remove them properly.  After regulator removal, the tank is visually inspected to make sure the threads in the neck are intact, and for fiber wrapped tanks, the fibers themselves must be undamaged.  Any stickers on the tank must be removed to allow a full external visual inspection – something that is also standard practice when filling tanks.

Fiber wrapped tanks consist of an internal aluminum cylinder that is reinforced with a wrapping of either glass or carbon fiber which is sealed in resin.  While scratches in the outer layer of resin are unsightly, it is physical damage such as fraying, burning or breakage of the fibers that can disqualify a tank from re-certification. 

After visual inspection the tank is hydrotested.  This involves placing it in a sealed container surrounded by water, and filling it with air to pressures beyond its service rating.  The pressure level for the test is determined by the DOT for the tank’s particular exemption (typically 5/3 of the operating pressure.)  When the tank is filled, it will expand slightly, stretching from the internal pressure.  This will displace water from the container it is in.  The amount of water is measured, and is equal in volume to the tank’s expansion.  When the tank is depressurized, the amount of contraction is also measured.  In order for a tank to pass hydrotesting, its expansion and contraction must be within the limits defined by the DOT for the tank’s exemption code.

Tanks that fail recertification, either from failing the hydrotest itself or showing visible signs of damage, may no longer be used.  Responsible hydrotesters condemn the tank from service, often going so far as to drill a hole through it and grind off the hazmat exemption number, to prevent the tank from being put back into service.  

Tanks that pass certification are marked with a label bearing the name of the hydrotester, and the re-certification date.  Standard practice is to place this label above and to the right of the cylinder’s existing label, and to cover it in an epoxy resin to prevent peeling, and to make certain it can’t be moved in a later attempt to cover tank damage.

Rather than simply smear a blob of epoxy over their stickers, Crossfire has gone the extra mile of setting up a cylinder coating facility.  This allows them to coat the cylinder and re-certification sticker in a layer of the same type of resin that is used in the original manufacture of the tanks.  The result is that the hydrotest label is fully embedded and secured to the tank.  Since this process modifies the tank, it is actually performed before the hydrotest, so that any effect it may have on the tank is accounted for.

All of the tanks sent in to Crossfire passed re-certification, and were given the company’s new “spa treatment.”  This brand new service provides a new coating to the full tank, not just a band aligned with the retest sticker.  Like the label sealing it too is performed prior to hydro.  

All of the tanks had been well cared for – with tank covers used to protect them from abuse on the field.  Even so, one had a chip in its finish from a fall in the workshop, and another had some very gloppy epoxy over the sticker from an earlier recertification.  

The spa treatment coated these tanks with a fresh outer coat which filled in the minor scratches and smoothed over the lumpy epoxy.  The used tanks literally came back looking brand new.  Crossfire is hoping this service will appeal especially to store owners and players who deal in used gear, by increasing the value of a used tank.

To further illustrate the difference the new coating can make, Crossfire president Chris Havlock took a condemned tank and literally abused it with a screwdriver, scratching deep into its outer coating.  None of the scratches damaged fibers, so they would not have prevented re-certification (the particular tank had failed hydro.)  By coating only a three-inch section of the tank, the damage could be easily compared side by side with re-coated section.  The difference was significant.  The cylinder went from looking badly damaged to looking factory fresh.

Another bonus of the spa treatment is that stickers and photos can be imbedded under the coating.  WARPIG stickers and a picture of Jackson (the head of security here at Corinthian Media Services) were sent along with the tanks.  After the tanks passed hydro, the stickers were placed on them and imbedded under the new spa treatment coating.  This made them a permanent part of the tanks, just like the original factory label, meaning they would not have to be removed for visual inspections at air fill stations.  While the sticker service does bring an added price to the service, is stands as a rather effective way to personalize a tank, either merely for looks or to help identify it in the case of theft at the field.  

After the Spa Treatment and completion of testing, Crossfire reinstalls regulators.  For years they have offered trade in programs where they will give a discount for players exchanging their regulator for a Crossfire.  Not surprisingly, they offer a similar discount program with a package price for re-certifying a tank and installing a new Crossfire high output or low output regulator.

Hydrostatic testing and re-certification is a required part of both legal and safe use of compressed air systems in paintball.  Crossfire’s DOT certified testing service provided the benefits of being performed by a tester already familiar with paintball regulators, with the option of resurfacing the cylinders to replace the marks of normal wear and minor damage with a factory new exterior.

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All articles and images are copyrighted and may not be redistributed without the written permission of their original creators and Corinthian Media Services. The WARPIG paintball page is a collection of information, and pointers to sources from around the internet and other locations. As such, Corinthian Media Services makes no claims to the trustworthiness, or reliability of said information. The information contained in, and referenced by WARPIG, should not be used as a substitute for safety information from trained professionals in the paintball industry.
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