Plumber's Licensing Exam: Special Piping And Storage Systems

This guide covers the immensely important task of monitoring the safe installation and subsequent long-term use of certain gas and vacuum systems. To prevent a disaster, there are very specific rules that must be followed for the safe installation and use of these systems.
This guide focuses on nonflammable medical gas systems and nonmedical oxygen systems. These include medical oxygen, inhalation anesthetic, vacuum piping, and nonmedical oxygen. The maintenance and operation of these systems is found under the regulations of the International Fire Code (IFC) and the National Fire Protection Association (NFPA).

Objectives
- Understand safe installation of medical gas and nonmedical oxygen systems
- Develop awareness of associated codes
- Recognize proper marking of piping systems

Key Terms:
ASME
oxidation
station outlet

Nonflammable Medical Gasses
Common nonflammable medical gasses include oxygen, nitrous oxide, compressed air, carbon dioxide, helium, and nitrogen. (Refer to IPC 1201.1; UPC 1301.0–1302.0, 1309.0 –1328.4)
A medical gas system extends from the source, whether it is bulk storage, a compressor, a vacuum pump, or a manifold, to the station outlet where the gas is available to the area in which it is installed (Figure below). All nonflammable medical gasses must be conducted through type L or K copper tubing that has been cleaned and capped.

Only tubing that carries the imprinted designation OXY, OXY/MED, ACR/OXY, or ACR/MED can be used in a medical gas system. All fittings and valves used in a medical gas system must be cleaned and sealed in airtight containers that are oil-free and have been purged with nitrogen.

Real-Life Situation: Ace Plumbing has built a reputation for excellence, thanks to the dedicated employees Carlos has hired and kept over the years. Carlos’s demanding yet benevolent leadership has created a company that his workers are proud to be a part of. Carlos’s team has given him the confidence to bid and win the contract for the new Jackson Wing of County General Hospital. The head supervisor, Emil Meconi, will have his hands full organizing the project and keeping it on schedule. In addition to all of the sanitary waste piping and water supply piping work, Ace Plumbing must extend all of the medical gas piping into the new wing from the existing systems in the main hospital.
Only Dharini, Ace’s new employee from Bhopal, India, has experience with medical gas systems. Carlos made her the supervisor for all of the medical gas piping because she had been the assistant maintenance manager at the AIIMS medical college and hospital there. Bhopal is where the Union Carbide plant leaked deadly methyl isocyanate gas in 1984 killing thousands of people, including Dharini’s grandfather. Carlos expects Dharini to be especially diligent with the installation of the medical gas systems.

Figure: A Station Outlet in a Medical Gas System

The UPC requires all valves to close and open with no more than a quarter turn. Connections must be brazed or soldered while nitrogen is flowing through the tubing to prevent any oxidation scale from forming inside the fittings or valves. The piping system must be tested to 11/2 times the working pressure of the system. In addition to an inspection by the Authority Having Jurisdiction, a medical gas system must be certified by a third-party agency that carries a certification from the Medical Gas Verifiers Professional Qualifications Standard.
The UPC specifies the need for piping plans to be drawn up and in the hands of the installer so that the piping is installed correctly to exact specifications the first time. In addition, a copy must be on-site at all times to allow for review by the Authority Having Jurisdiction and must remain in the possession of the building owner after installation.

Caution: Take nothing for granted when working on medical gas systems. Ensuring the perfect operation of these systems is critically important. The lives of the patients and all of the people in the building are at stake. All of the gasses that flow through a medical gas system must be pure with no chance of contamination from any source, and there is an elevated chance that contamination could occur during sloppy installation procedures. Also, you must keep in mind that even though oxygen is considered nonflammable, it supports combustion very well, meaning that anything that can burn will burn very violently in an oxygen-rich environment.

Tips
Always follow the manufacturer’s installation instructions for all equipment that is connected to any medical gas system. Many pieces of equipment will be foreign to installers and will have certain installation idiosyncrasies that must be followed for the equipment to operate as designed.
All medical gas piping needs to be clearly marked to prevent cross-connections with other systems and to ensure that there is no interruption of service from these critical systems.

The table below shows the markings and colors used for these piping systems.

Medical Oxygen
Oxygen is one of the most common nonflammable medical gasses. That’s right, nonflammable. Oxygen supports combustion, but it does not burn. Burning, or combustion, is a rapid form of oxidation. Oxidation is the chemical process that occurs when a substance combines with oxygen. Therefore, since oxygen does not combine with oxygen (with the exception of ozone formation), it does not combust. So, it is not flammable. (Refer to IPC 1203.1)

Fact: Our normal atmosphere contains 21% oxygen. An oxygen-enriched atmosphere occurs when the oxygen content of the air increases to as little as 24%. Oxygen-enriched atmospheres most often occur from leaks in an oxygen system. Cracked hoses, loose fittings, or damaged equipment are likely culprits. In an oxygen-enriched atmosphere, clothing, hair, and all other combustible materials can very easily catch fire and it becomes very difficult, if not impossible, to extinguish the flames. Never use an open oxygen hose to dust yourself or anything else off.
Some materials, such as grease, oil, and certain metal alloys can burst into flames even without a source of ignition in an oxygen-enriched atmosphere. Never use oil or grease as a lubricant in an oxygen system and only use thread tape or pipe dope that is explicitly approved for oxygen use. Even many soaps and detergents contain grease and should not be used near an oxygen system. In short, only use materials and compounds that are specifically approved for oxygen service.
Obviously, however, oxygen must be handled very carefully because it is a key player in combustion. That status justifies special handling.

The figure below shows a medical gas distribution center.
When installing and inspecting medical gas systems, properly defining systems covered under medical gas is critical. Piping systems covered in medical gas have their own definitions and language, which need to be defined for both inspector and installer to verify installations meet current standards.

Figure: A Medical Gas Distribution Center


Figure: Nonmedical Oxygen Storage

Nonmedical Oxygen
This section applies to facilities that have more than 20,000 cubic feet of oxygen stored on premises, but are not producers of oxygen (Figure below). Bulk oxygen storage tanks must be ASME Boiler and Pressure Vessel rated. They also must be corrosion resistant. An alternative design for the tanks is to build them to U.S. DOT 4L container regulations. In either case, the tank(s) must be individually equipped with a pressure relief valve. (Refer to IPC 1202.1–1203.1)
All of the pipes and tubing must conform to standards for oxygen service. The joints must be of the brazed, flanged, threaded, socket, slip, or compression design.
When oxygen is used in conjunction with acetylene or another fuel gas for welding and cutting purposes, the equipment must have protective devices that prevent flow of the oxygen into the fuel gas and prevent flashback of the flame into the fuel gas. As with other piping systems, the piping must be tested to 11/2 times the working pressure of the finished system as it will operate.

Vacuum System Piping
Vacuum systems are not held to as high a standard as the medical gasses that are supplied to patients and medical equipment. However, they still must be constructed of corrosion-resistant materials, which includes copper water tube type K, L, or M; ACR tubing; copper medical gas tubing; galvanized steel pipe; or stainless steel tubing. All copper connections must still be brazed. Galvanized steel joints must be flanged or threaded. (Refer to IPC 1202.1; UPC 1326.1–1326.5)
 

Medical Air Compressors
Medical air compressors shall be sufficient to serve the peak calculated demand with the largest single compressor out of service. In no case shall there be less than two compressors.
The vacuum piping must be clearly marked “Medical-Surgical Vacuum,” or MED/SURG VAC, no more than 20 feet apart. Medical vacuum systems must have two vacuum pumps equipped with isolation valves in order to ensure the continuous operation of the system to a reasonable degree. Testing and inspecting shall be carried out and reference made to NFPA99.