Medical gas flow control

The dramatic drop in health care construction spending that occurred in 2009 because of the economy appears to have turned the corner in 2011. Though spending is still sluggish with only single-digit increases in budgets for 2012, opportunity exists for growth in medical gas equipment sales.

New construction and facility renovation projects will in many cases involve the installation of new National Fire Protection Association (NFPA) 99-compliant medical gas central supply systems for USP oxygen, USP nitrous oxide, NF nitrogen and USP air. Understanding how to size and select the appropriate system will be a key factor in securing not only the equipment contract but also will play a role in the gas supplier being able to show cost savings that may win or retain the gas contract.

It is worth noting here that passage of the Patient Protection and Affordability Care Act (PPACA) with its reduction in Medicare and Medicaid payments has left health care facilities looking for ways to reduce costs in other areas, especially those considered as commodities or operating expenses, such as medical gas costs.

This article will detail how to appropriately size and select an NFPA 99 medical gas central supply manifold and in so doing show the client cost savings without reducing the cost of the gas, using medical USP oxygen from cylinders and/or portable cryogenic containers as an example.

In October of this year the NFPA finally released the 2012 edition of NFPA 99 renamed the Health Care Facilities Code which included major revisions to the previous 2005 edition. Since the new edition is under review by The Joint Commission (JCAHO), we will focus on the 2005 edition of NFPA 99, Chapter 5, which covers medical gas central supply systems for liquid and high-pressure cylinders with or without a third-leg reserve.

Sizing a medical gas central supply system

When it comes to delivering medical gases to a health care facility, nothing is more critical to patient health than the oxygen that sustains life. If accurate current oxygen usage is available and there is no expected expansion, then the equation for the amount of gas required is fairly simple. Apply the principle that the total number of cylinders or volume of gas should be not less than what would be used in seven to 10 days (see Table 1). If only high-pressure cylinders are used as the source, then a minimum of two cylinders per side is required as illustrated in Figure 1. If the system is for a new construction or includes expansion, then the number and type of use points need to be tabulated as shown in Table 2, depending on the type of activity. For operating rooms, which vary from patient rooms, the gas used per room or outlet must be used to calculate a total used per day, which can then be used to arrive at how many cylinders are required per side.

As you will note in Table 1, once you exceed 16,000 scf/month or approximately eight cylinders per side using portable cryogenic liquid cylinders, Dewars become a viable option as the primary and secondary supply. This, however, requires that the system have an additional third-leg 24-hour reserve of high-pressure cylinders that must be a minimum of three cylinders, as shown in Figure 2. This can result in significant cost savings for the facility because of the lower cost per cubic foot of gas when supplied in Dewars as well as the reduction in cylinder rental cost as one cryogenic container holds roughly the equivalent volume of 18 high-pressure cylinders. However, if the usage is less than 16,000 scf/month but more than 8,000 scf/month, then using what is called a hybrid system in which only the primary side of the system has a Dewar and the secondary and third leg have high-pressure cylinders as shown in Figure 3, is an option. For facilities in which total usage is less than 8,000 scf/month, the savings based on using the Dewars becomes less attractive as some of the contents may not be used because of vent loss.

Selecting a central supply system

These systems must be obtained from and installed according to the instructions of a supplier familiar with their proper construction and use. The manufacturer should have a proven track record of designing and actually manufacturing the various components of the manifold. Keep in mind that these systems should be designed to last for years and be able to be serviced far into the future. Many existing, grandfathered systems were made by companies that no longer exist, creating non-viable situations. Look for systems supplied by companies with manufacturing capability and longevity.

A unique requirement for manifolds for cryogenic liquid cylinders is that they must have a function to conserve the gas in the secondary header, such that it is supplied to feed the line regulators before the container’s own relief valve vents the gas. This is commonly called an economizer function, and there are many systems that attempt to achieve this requirement with poor results. NFPA 99 does not state what means or mechanism to use, and some methods lead to both primary and secondary headers being empty almost simultaneously. A well-engineered computer controlled mechanism conserves the gas and doesn’t drain both supply headers.

These systems are becoming more common as explained earlier because of cost advantages. There can be drawbacks for systems that don’t have properly engineered designs. Look for one that differentiates its operation based on which relief-valve setting (230 psig, 350 psig or 500 psig) is actually connected to the system. To optimize the cost savings when using cryogenic liquid cylinders, this capability is very important as it prevents vent loss while being selective in how it engages the economizer function.

Most manufactures have three separate main control systems, one for each of the three configurations stated above, and they are not capable of being reconfigured. This makes expansion or mode change to or from cryogenic liquid cylinders impossible with their systems. It would require purchasing another new unit. The system would be shut down, and the installation labor, verification and testing by itself can exceed $10,000, plus the cost of the new system.

It is both practical and efficient to consider choosing a system that has the flexibility to change without shutting the oxygen system down. Verifying tests would be minimal as the purity of the pipeline was never compromised as changes are little more than replacing a pigtail and a source selection function that reconfigures the system for the new cylinder style.

In this way, you will show your medical facility clients cost savings by basing their gas source on their system demand and offering flexible systems that can grow or change as their needs do. Companies focused on knowing how to size and select the appropriate medical gas central supply system can capture new gas business and retain existing contracts without discounting product costs.