Choosing Medical Gas Filling Equipment

Medical gas filling advice.

Selecting the right medical gas filling equipment when first building or upgrading a medical fill area can have a major impact on your ultimate success in winning and keeping medical business. Many distributors jump into medical gas filling because of service or logistics issues with a third party supplier. Distributors then upgrade their medical filling area when the growth of the business and the addition of a large customer make their existing fill equipment inefficient. Well-maintained fill plant equipment can last 20 years or more, which makes the decision in selecting the right equipment all the more important.

A 40-cylinder modular E rack

A 40-cylinder modular E rack

Economic Considerations
Ultimately, the total cost of delivering a full cylinder to the customer is the most important cost. In evaluating whether to fill their own cylinders or have a third party fill for them, distributors often focus on the difference in cost of USP bulk liquid and high pressure gas in cylinders. By taking the cost of bulk liquid, adding capital, operating and labor costs, a distributor can calculate a cost to fill their current volume into cylinders.

The formula in the above paragraph, however, overlooks some important cost benefits of filling your own cylinders. To have one cylinder at the customer location (and presumably collecting rent), a distributor not filling his cylinders will need two or more additional cylinders in the supply chain: One cylinder will be at the supplier’s plant getting filled, with the second in reserve for the customer or in the logistics system. Depending on the service level of the supplier and the schedule of deliveries and pick-ups, even more cylinders may be required.

By filling your own cylinders, this ratio often can be reduced to one cylinder at the customer’s site and one in the supply chain. For a distributor, this can translate to a third more cylinders available to be rented without increasing the number of cylinders in the fleet.

The Basics
To fill your own medical cylinders you will need at least the following equipment:

  • Bulk oxygen tank certified for USP grade oxygen
  • Tank legs (set of 3)
  • Cryogenic pump, sized to the size of the fill manifold
  • Pump control panel with cavitation protection
  • High pressure line relief (normally 3250psi)
  • High pressure monel tubing or xxh brass pipe
  • Fill control panel with low temperature shutdown
  • Vacuum pump with oxygen service oil
  • Copper vacuum and vent lines
  • Fill manifold(s)
  • Oxygen analyzer
  • Third party system validation.
Each of the above pieces of equipment must be sized to fit together and efficiently fill the number and types of cylinders desired. From a safety standpoint, the cryogenic pump, the vaporizer and the manifolds have to be sized to fill slowly enough to limit the heat of compression and the oxygen velocity in the manifolds. Often the solution is to fill 200 (H size) cylinders in parallel with “E” and “D” size cylinders. The larger cylinders provide sufficient volume to slow the fill velocity and reduce the heat of compression. This also makes it much easier for the operator to use pressure and temperature charts to achieve an accurate fill.


Automated control panel for an E fill system

Automated control panel for an E fill system

Most distributors have the highest volume of cylinder filling needs for the post valve “E” cylinder. Over the years, hundreds of different standard and custom-designed E fill manifolds have been built. Today, the most popular standard designs are modular, with a 24-cylinder, two-tier E fill rack most common. This design has two rows of 12 cylinders, each with its own manifolds and quick connects for each cylinder. The modular 24-cylinder manifolds can be placed back to back or in a line to create racks of 48, 72 and 96 cylinders to fit into existing fill plants.

Many distributors are also filling E size cylinders with the integrated regulator. These cylinders require specially designed fill manifolds with fill connections matched to the valve design. In some cases, existing E racks can be adapted with high pressure quick connects that can be changed out with special fittings to fill the integrated valve type cylinder.

High Volume Filling
Distributors who have a high volume of medical business should consider automating the cylinder filling process to achieve higher efficiency and reduce costs. Since the E cylinder filling generally has the greatest volume, automating this fill process produces the greatest efficiency gain.

A PLC (programmable logic controller) based system can double or triple the number of E cylinders filled per operator man hour.

These systems typically use a gravimetric fill process to vent, vacuum and fill a rack of 48 to 96 E cylinders while the operator is busy loading and doing pre-fill checks on a second rack. While the operator tests and unloads the first rack, the PLC starts the fill process on the second rack the operator just loaded. By the time the operator has re-loaded the first rack, the second is finished and the cycle continues. Such a system, with two operators and two 96-cylinder racks, can fill over 50,000 cylinders per month in a single shift per day.

Most distributors will never have to fill such a large number of cylinders. However, having the ability to quickly turn around a large volume of cylinders is often the difference in winning and keeping medical gas customers. While the competition in the medical gases market is keen, the volume of medical gas business continues to grow as the U.S. population grows and ages. Close attention to the equipment choices you make today can ensure your competitive position in the future.

Gases and Welding Distributors Association
Kent Buzard Meet the Author
Kent Buzard is the vice president of business development at CTR, located in Rock Hill, South Carolina, and on the Web at www.ctrinc.com.