Medical Gas Underground Piping & Flexible Connector Standards
Ensuring Safe and Compliant Installation of Medical Gas Piping
The proper installation of underground medical gas piping and flexible connectors is critical to ensuring safety, compliance, and longevity in healthcare facilities. This guide outlines key NFPA 99 standards for installing underground piping outside buildings and using metallic and nonmetallic flexible connectors.
1. Underground Piping Outside of Buildings
1.1 Frost Protection & Physical Damage Prevention
- Piping must be installed below the local level of frost penetration to prevent freezing-related failures.
- During backfilling, all piping must be protected from physical damage to ensure long-term durability.
1.2 Requirements for Underground Piping in Conduits
- Access points must be provided at joints for visual inspection and leak testing before backfilling.
- The conduit, cover, or enclosure must be self-draining to prevent prolonged groundwater exposure.
1.3 Depth Requirements & Backfilling
- Piping subject to surface loads must be buried deep enough to prevent excessive stress.
- The minimum backfilled cover above the pipe shall be:
- 900 mm (36 inches) in most cases.
- 450 mm (18 inches) where there is no potential for damage from surface conditions.
- Trenches must be excavated so that pipes rest on a firm and continuous bearing surface.
- Backfill must be clean and free of materials that could damage the pipe.
1.4 Identification & Warning Systems
- A continuous tape or marker must be placed above the pipe to clearly identify the pipeline.
- A warning marker should be installed at approximately half the burial depth.
- When piping passes through a wall sleeve, the outdoor end must be sealed to prevent groundwater entry.
2. Hose & Flexible Connectors
2.1 Installation & Safety Considerations
- Flexible connectors must be kept as short as necessary and must not be concealed inside walls, floors, ceilings, or partitions.
- Connections in manufactured assemblies may be concealed above a ceiling if inspection access is available.
2.2 Burst Pressure & Durability Requirements
- Flexible connectors must have a minimum burst pressure of 6895 kPa (1000 psi).
- Metallic flexible joints are permitted for:
- Expansion joints and seismic protection.
- Thermal expansion and vibration control.
2.3 Material & Manufacturing Standards
- All wetted surfaces must be made of bronze, copper, or stainless steel.
- Components must be factory-cleaned for oxygen service and certified for cleanliness.
- Flexible joints must withstand pressures of 2070 kPa (300 psig) and temperatures up to 538°C (1000°F).
- Joints must have brazing extensions to allow secure integration into the pipeline.
- They must be supported using appropriate pipe hangers and supports.
3. Get Expert Consultation for Medical Gas Installations
Proper medical gas piping installation and compliance with NFPA 99 guidelines are essential for safety and efficiency. If you’re planning a new medical gas system or upgrading an existing one, our experts can help.