Failures piping specifications

On heating up, thermal expansion of a liquid in sealed piping, equipment or a container may exert sufficient hydraulic pressure to cause rupture or failure. (Hence specific filling ratios are followed with containers, e.g. road tankers.)... 

Failure to Follow Piping Specifications as Piping Supports Are Altered... 

Investigators determined that a carbon steel section of 6-inch (150 mm) line was installed in an area in which specifications required corrosion-resistant 5-percent chromium—1/2-percent molybdenum (generally called 5-chrome) alloy piping. In a process plant like a fluid coker, the materials used are a mixture of carbon steel and other steel alloys. Apparently, the welder and the maintenance crew, who previously repaired this piping some time ago, were not aware of the piping specifications. Apparently, they did not realize that if a material like carbon steel was installed in an area requiring 5-chrome alloy piping, erosion or corrosion could cause failure. 

The Dow Chemical Company recommends canned-motor pumps or magnetic-drive pumps for phosgene service. Phosgene is an example of an extremely hazardous material. These pumps should have a secondary containment such that failure of the can does not create a phosgene release. The secondary containment should meet pipe specifications for pressure or relieve to the scrubber system in the plant. These pumps must have automated block valves on the suction and discharge. Operation of these valves should be managed such that the thermal expansion does not damage the pump. 

Major fire occurs after the failure to follow piping specifications during maintenance... 

Davenport has listed more tlian 60 major leaks of flammable materials, most, of which resulted in serious fires or unconfined vapor cloud explosions (UVCEs)." Table 16.3.1 classifies tlie leaks by point of origin and shows that if transport containers are excluded, pipe failures accounted for more than lialf tlie accidents. The biggest cause of tliese failures lias been shown to be poor construction due to use of wrong specifications or failure to follow specifications established. 

More pumps fail as a direct result of improper installation than any other single factor. The predominant reasons for these failures include starvation, caused by inadequate or inconsistent suction conditions distortion, caused by pipe strain or improper foundation and turbulent that results from piping or entrained gas problems. Centrifugal pump installation must follow Hydraulic Institute Standards, which provide specific guidelines to prevent these installation and performance problems. This chapter will address the fundamental requirements for proper installation. 

I-3.6.2 Electronic control, monitoring, and hydrogen gas measurement equipment shall be properly grounded and isolated from piping to help prevent overpressure/ accidental shutoff situations caused by equipment failure due to lightning strikes and electrical transients and to prevent safety hazards caused by fault currents. Electrical isolation equipment for corrosion control purposes should not be installed in buildings unless specifically designed to be used in combustible atmospheres. 

Specific segments of process piping handling flammable liquids or gases in mixtures known to promote pipe failures through erosion, corrosion, or embrittlement. These include hydrocarbons, streams that may contain entrained catalyst, caustics, acids, hydrogen, or similar materials where development of an appropriate scenario envelope is feasible. 

Environmental stress cracking (ESC), usually associated with SCG accelerated by surfactants or other aggressive media, is also of considerable interest in its own right, since pipe materials are often intended for service in contact with water or other industrial fluids. Oxidative degradation is another important concern, particularly at high temperatures, and stabilisers are often added specifically to retard SCG and catastrophic failure [65, 66, 67, 68], the stabiliser type and concentration being critical at very low SCG rates, even where they have little effect on rapid fracture [69]. 

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