Frequently Asked Questions

Whatever you need to know about cylinder testing, we can help. Take a look at our frequently asked questions below, if you can’t find the information you are looking for, contact us

What different types of cylinders do you sell?

We sell the following different product lines of cylinder models:

High Pressure Steel (20CF up to 400CF)
Acetylene (10CF up to 450CF)
Aluminum CO2 (1.5# up to 50#)
Aluminum Industrial (N6 up to N265)
Aluminum Medical (M6 up to M265)
Paintball (18 oz. up to 24 oz.)
Scuba (S80)
Composite (select models)

Do you sell fully assembled cradles, gas packs, and pallet manifolds?

Yes, we do. Certified Cylinder offers fully assembled Cradle and Pallet Manifolds in 6-, 12- or 16-cylinder configurations. We assemble and install cradles, gas packs, and pallet manifolds – ensuring the test dates on all cylinders match each other – before being shipped.

What are the exact dimensions of steel cylinders?

Steel cylinders have dimensional variations between the same size cylinders. Depending on the manufacturer, the cylinder’s dimensions may vary by a couple of inches. We give an approximate height and width of the largest typical dimensions.

What are the differences of steel versus aluminum cylinders?

Steel cylinders are more economical but significantly heavier than aluminum. Aluminum is more rust and corrosion-resistant than steel, which is important for wet gases and in humid or condensation-prone environments.

What are the differences of ISO versus TC/DOT cylinders?

All cylinders must be manufactured and certified to a recognized standard. Transport Canada (TC), The US Department of Transportation (DOT), and UN/ISO all have established cylinder standards.

UN/ISO standards are newer than TC/DOT standards, and UN/ISO cylinders are equivalent to, and arguably superior to, TC/DOT-rated cylinders:

  • UN/ISO is a universally recognized worldwide regulation for compressed gas cylinders, and UN/ISO cylinders are approved for use in almost every country around the world. UN/ISO cylinders can cross country borders and still be filled easily.
  • UN/ISO service pressure is at or above the common fill pressure of a DOT cylinder with a +10% overfill designation. These higher capacities allow for UN/ISO cylinders to be easily integrated into a fleet of TC/DOT cylinders.
  • UN/ISO cylinders contain friendly markings with service pressures rated in PSI and Bar.
  • UN/ISO cylinders remain in circulation at maximum capacity for the life of the tank. Due to the higher design ratings for pressure, UN/ISO cylinders do not require REE (Reject Elastic Expansion) testing to achieve the common cylinder service pressures used and approved in North America. While REE is a valuable and stringent test, older cylinders will often have their maximum fill pressure ratings reduced after testing.

What types of bulk tanks do you sell?

The Titan® bulk product line offers a wide selection of capabilities and sizes for small or large bulk applications of Argon, Oxygen, Carbon Dioxide, Nitrogen, or Nitrous Oxide gases. Larger models than what are listed here are also available by request.

Titan® Small Bulk Co2 (300# up to 750# CO2)
Titan® Small Bulk Industrial (450 L up to 5,600 L)
Titan® Large Bulk CO2 (6-ton up to 50-ton CO2)
Titan® Large Bulk Industrial (1,500 gallon up to 13,000 gallon)

What is your warranty for bulk tanks?

Our Titan® bulk tanks are backed by a competitive 5-year warranty.

Do you install concrete pads for bulk tanks?

No, we do not offer services to install concrete pads for bulk tanks. Concrete slab installs are vastly different for each geographical location and must follow local laws and regulations. Consult your local municipality for specific guidelines before beginning a storage tank concrete pad install.

Do your bulk tanks have top and bottom fill?

Yes, our small and large bulk tanks come standard with top and bottom fill capabilities.

What is Level-Eye®?

Level-Eye® is a digital gauge that uses precise percentage measurements to accurately measure liquid level capacities in cryogenic cylinders. It was designed to replace traditional mechanical floats that often get broken and provide inaccurate information of the liquid gas level in the tank. Used in conjunction with the appropriate sized wand, the Level-Eye® gauge offers a level of accuracy that the traditional mechanical floats simply cannot match.

How do I install my Level-Eye®?

Level-Eye® installation should only be installed onto an empty tank and always BEFORE the filling process. Please visit our Level-Eye® page for full instructions or download our Level-Eye® User Manual.

How do I calibrate my Level-Eye®?

Level-Eye® calibration is a TWO-STEP PROCESS of setting the liquid level range from an empty (low) level to a full (high) level for your specific tank size and model. Please visit our Level-Eye® page for full instructions or download our Level-Eye® User Manual.

What is CylConnect®, and how do I use it?

CylConnect® Remote Monitoring provides you with daily updates of your tank’s capacity level (transmitting parameters such as liquid level, pressure, and/or weight) directly to your computer or mobile app. You gain peace of mind as you are able to monitor and track your tank’s level every day.

How often does a cylinder require testing?

It is dependent on the type of cylinder and type of service of the cylinder. Most industrial cylinders require testing every 5 years.

What is the manufacturer or certification date of a cylinder?

All cylinders have a manufacture date. Recertified cylinders also have a certification date. The most recent date on the cylinder is the currently active date. The most important date to know when purchasing a cylinder is when the cylinder was last recertified (recertification means that all TC/DOT requirements for that cylinder have been met).

Transport Canada (TC) requires that composite, aluminum, and steel cylinders containing 30%+ CO2 by volume be certified every five years. Nitrogen and other high pressure inert gas cylinders generally have a 10-year recertification requirement but can sometimes be limited to 5-years based on the test data. Certification must be performed by a TC or DOT-licensed facility.

The date of the last recertification is the 7 digits stamped across the shoulder of the tank. The first two digits indicate the month (i.e., 01 = January), and the final two are the year in which the tank was tested (i.e., 23 = 2023). The three digits in the middle are the TC requalifier’s identification number (RIN) of the recertification facility. Additional marking may come after the two digits indicating the year, such as +, *, UE, VE, etc.

  • “+” indicates the cylinder is approved for a +10% overfill of the rated service pressure (not used on TC cylinders)
  • “*” indicates the cylinder is approved for a 10-year service use before recertification is necessary
  • “UE” indicates that the cylinder was tested by Ultrasonic Examination
  • “VE” indicates that the cylinder was subject to, and passed, Eddy Current examination
  • “K” stamps are also used on TC cylinders that failed the REE to indicate the service pressure is to be reduced by 10%. The “K” marking would be found following the rated service pressure in Bar, if present.

Can you repair and refurbish old or broken cryogenic vessels?

Yes, our professional cryogenic repair service facility repairs and refurbishes all major brands and styles of cryogenic tanks to their original factory performance and appearance. We have competitive pricing, fast turnaround, and multiple service options.

Some of the repair services we offer are:

  • Initial testing & diagnostics
  • “Top Works” Repair – plumbing repaired and tested
  • Helium mass spectrometer leak testing
  • Cosmetic repair/refinish of carbon & stainless-steel vessels

For more information check out our Cryogenic Cylinder Repair page.

Can you repair and refurbish old or broken cryogenic vessels?

Yes, our professional cryogenic repair service facility repairs and refurbishes all major brands and styles of cryogenic tanks to their original factory performance and appearance. We have competitive pricing, fast turnaround, and multiple service options.

Some of the repair services we offer are:

  • Initial testing & diagnostics
  • “Top Works” Repair – plumbing repaired and tested
  • Helium mass spectrometer leak testing
  • Cosmetic repair/refinish of carbon & stainless-steel vessels

For more information check out our Cryogenic Cylinder Repair page.

Will this cylinder work for my application?

With so many uses for gas cylinders and components, plus the dangers of improper use, we cannot verify or confirm you’re purchasing the right items. It is your responsibility to specify and purchase the correct item(s) for your application, and to use them safely and appropriately.

Please make sure you are purchasing the right item for your intended use before you buy.

How do I choose the correct valve for my cylinder?

There are a lot of different valves out there, and a lot more different cylinders and outlet sizes. We want to make sure you get the right valve the first time. Here are some things to know before you order a valve:

  • Gas Type – Naturally, the first thing to know is the gas your cylinder is designed to hold and that you intend to use. A valve for a different gas may fit your cylinder but isn’t designed for the gas you’re using and won’t have the correct outlet fitting to connect to your regulator.
  • Aluminum or Steel Cylinder – Valves seal to the cylinder differently depending on whether it’s made of steel or aluminum. Steel cylinders use NGT threads, and the compatible valves are tapered. They seal by using that taper to tighten securely to the steel threads. Aluminum (UNF) cylinders require a gentler sealing method, so compatible valves have straight (no taper) threads with a flat flange on top to seal against an O-Ring on the cylinder top.
  • Don’t rely on a ruler (because ¾” is not always ¾”) – Measuring either the valve base or the cylinder inlet will not give you the correct size for the valve. For example, ¾” NGT valves measure about 1” from thread to thread. If you’re not a cylinder pro, the only way to know the size for certain is to ask your filler or compressed gas specialist to measure your cylinder and/or old valve for the correct size.
  • The numbers on the valve usually don’t tell the story – Few valves are stamped with plain-English version of the sizing. Most have proprietary identification marks that are unique to each manufacturer. Without the translation guide, they’re not much help in choosing a valve.
  • Safety matters – Your personal safety as well as the safety rating of the valve. The same size valve may come in multiple different safety pressure ratings. It’s crucial that you have the right safety for your cylinder size and material. Too low, and the safety will discharge too soon. Too high, and you can have an unintended discharge from the cylinder itself. Be sure to play it safe and know the correct safety rating before you order.

Compressed gas cylinders must be connected only to the regulators and equipment designed for the gas in the cylinder. Since connecting the wrong equipment can be dangerous, a number of different standard cylinder valve outlets are available for different classes of gas. For example, these standard connections prevent the valve connection for a flammable gas from fitting the connections for an incompatible gas, such as an oxidizing gas.

The bottom line is that unless you are certain of the size and safety rating you need, please seek professional assistance to determine the valve you need before you order. This will guarantee your safety and that you get the right valve the first time.

What are the best practices for opening and closing cylinder valves?

Observing a few simple rules when opening and closing cylinder valves can prevent damage to valves and equipment and add years of useful service life to the valves. The proper way to open any cylinder valve is to first crack the valve, then open it slowly by turning the handle or stem counterclockwise. This allows the equipment to gradually adjust to full pressure. Stop turning as soon as there is any resistance. Turning the valve handle or stem too far in the open position can jam the stem causing damage and leaks and preventing later closure.

Likewise, overtightening when closing a valve can damage or permanently distort the seat and result in leakage.

When should I “crack” the cylinder?

Before attaching the regulator, wipe clean the valve outlet with a clean cloth free of oil and lint and “crack” a secured cylinder by opening the valve slightly and then closing it immediately to blow out dust or dirt from the valve outlet. Use two hands on the valve and stand at the side of the valve – never stand directly in front of or behind the valve outlet.

Do not crack fuel gas cylinders due to the chance for the gas to ignite by friction, heating, or other ignition sources. Never crack hydrogen cylinders since the release of compressed hydrogen may ignite by itself.

What are cylinder safety devices?

Most cylinders have one or more safety-relief devices, known as a Pressure Relief Device (PRD). These devices can prevent rupture of the cylinder if internal pressure builds up to levels exceeding design limits. Pressure can become dangerously high if a cylinder is exposed to fire or heat, including high storage temperatures.

There are three types of safety-relief devices. Each relieves excessive gas pressures in a different way:

  • Safety- or Pressure-Relief Valves – These valves are usually part of the cylinder. They are normally held closed by a spring. The force holding the valve closed is set according to the type of gas in the cylinder. The valve opens if the cylinder pressure exceeds the set safety limit. Gas is released until the cylinder pressure drops back to the safety limit. The valve is then closed and retains the remaining gas in the cylinder.
  • Rupture Discs (also known as frangible or bursting discs) – These discs are usually made from metal. They burst or rupture at a certain pressure, releasing the gas in the cylinder entirely. The bursting pressure is designed so that the disc ruptures before the cylinder test pressure is reached. These devices cannot be reclosed, so the entire contents of the cylinder are released.
  • Fusible Plugs (also called fuse or melt plugs) – Temperature, not pressure, activate fusible plugs. These safety devices are used where heat could initiate an explosive chemical reaction. A pressure-relief valve rupture disc acts too slowly and too late to prevent rupture of the cylinder if an explosive reaction has already begun. The fusible plug releases the gas before the hazardous reaction can begin. Fusible plugs are made of metals that melt at low temoperatures. For example, acetylene cylinders have a fusible plug which melts at about 100°C
    (212°F). This temperature is safely below the temperature at which hazardous polymerization may occur.

Not all compressed gas cylinders have safety devices. Some gases are so toxic that their release through a safety device would be hazardous. Cylinders for these gases are built to withstand higher pressures than normal cylinders. When these “toxic gas” cylinders are involved in a fire, the area must be evacuated.

How do I store compressed gas cylinders?

Store compressed gas cylinders in compliance with the occupational health and safety regulations and fire and building codes applying to your workplace. These laws may specify the permissible kinds of storage areas and the construction of these storage areas. They may also specify the kinds and amounts of different gases that can be stored in each safe storage area.

Why is proper ventilation important?

Well-designed and well-maintained ventilation systems remove gases from the workplace and reduce their hazards. The amount and type of ventilation needed depends on such things as the type of job, the kind and amount of materials used, and the size and layout of the work area.

Assess the specific ways your workplace stores, handles, uses and disposes of its compressed gases. An assessment can reveal if existing ventilation controls and other hazard control methods are adequate. Some workplaces may need a complete system of hoods and ducts to provide acceptable ventilation. Others may require a single, well-placed exhaust fan. Storage facilities for particularly hazardous materials such as chlorine, may require an additional emergency ventilation system, or continuous monitoring with appropriate alarms. Other workplaces using small amounts of inert gases may require no special ventilation system.

Make sure ventilation systems are designed and built so that they do not result in an unintended hazard. Ensure that hoods, ducts, air cleaners and fan are made from materials compatible with the gas used. Systems may require explosion-proof and corrosion-resistant equipment. Separate ventilation systems may be needed for some compressed gases to keep them away from systems exhausting incompatible substances.

How do I transport or move cylinders?

Always transport cylinders with valve caps or other valve protection in place. Pulling cylinders by their valve caps, rolling them on their sides or dragging or sliding them can cause damage. Rolling cylinders on their bottom edge (“milk churning”) may be acceptable for short distances. Never lift cylinders with magnets or chain or wire rope slings. Transport cylinders on specially built hand carts or trolleys or other devices designed for this. All transport devices should have some way of securing cylinders to prevent them from falling.

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