Corrosion, either internal or external, along with other types of defects on pipelines eventually lead to leaks without proper treatment. This gives rise to several issues, including environmental and safety hazards, and in case of pipe leaks in a plant, a loss of the efficiency of the process or, ultimately, failure of the process. Replacing the corroded pipelines (piping) can be difficult, costly and time consuming especially for plant. A required shutdown causes major economic loss. Thus, instead of a replacement of the defected pipelines, the installation of online repair is a better option.
Repairs of pipelines include metallic and non-metallic repairs. Metallic repairs generally require welding or hot works which is not suitable for online repair of pipes containing hydrocarbons. In such cases the use of non-metallic composite repairs is the optimum solution. A non-metallic composite repair system is a system used to reinforce structures using a fiber equipped with a thermoset epoxy system. The epoxy system consists of a hardener and a resin which, after mixing, become solid through a polymerization reaction after a short duration of time, a process that is called curing. Depending on the temperature, the duration of time changes in an inverse relation. The higher the temperature, the smaller the duration of time needed for curing. This system can be used to reinforce pipelines with both external and internal corrosion and it can be used on Straight Pipes, Tees, Elbows, Flanges and weld joints. The repair system can also be installed online without the need for a shutdown in a short amount of time and a small requirement of labor intensity, making it cost effective. It is also environmentally friendly. In this paper we are going to present cases that were resolved by our company that demonstrate how successful these non-metallic composite repairs are and how diverse their applications can be

Residual stresses are self-equilibrating stresses that exist in materials and structures at the absence of instantaneous application of external loadings. In industrial manufacturing and fabrication processes, such stresses can be prominent and may lead to premature failures if uncontrolled. Such failures can be manifested in many forms including stress corrosion cracking, fatigue cracking or brittle facture. This paper is devoted to providing a comprehensive review on residual stress in the manufacturing and fabrication domain with a greater emphasis on welding based residual stresses. Three residual stress evolution mechanisms will be evaluated covering deformation driven stresses during manufacturing, thermally driven during welding and surface modifications such as grinding, carburizing and plating. In welding processes, the residual stresses in the cooling cycle are characterized using Gleeble testing illustrating the stress profiles as a function of temperature. The effect of residual stresses in welded structures will be discussed covering fatigue performance, brittle fracture and effect on Stress Corrosion Cracking resistance. To ensure residual stresses are effectively measured and quantified, a total of nine (9) destructive, semi-destructive and non-destructive residual stress measurement techniques are evaluated. A comparison and evaluation of four (4) common residual stress mitigation techniques are also discussed covering Ultrasonic Impact Treatment, High Frequency Mechanical Impact, shot peening and Post-weld Heat Treatment. The review discussion extends to four (4) factors towards impacting the residual stress magnitude and distribution covering material properties, welding process and clamping and preheating during welding.

The heat treatment condition of industrial materials is a critical parameter for material evaluation and its fitness for intended service. Proper heat treatment will produce desired mechanical and physical properties, while absence or improper heat treatment may lead to major failure with huge production, Environmental, Health, and Safety (EHS) impacts. We hereby explain an actual case for cracked gas compressor (CGC) 5th stage discharge line caustic stress corrosion cracking (SCC) that caused unplanned plant shut down and resulted in noticed financial and production loss.
The proven root cause is absence of normalization. Emergency piping batch is received and supposed to be normalized to avoid failure recurrence. Many discrepancies extracted from submitted material certificates, also many physical signs observed on the material itself raising doubts about received material compatibility. Using advanced Positive Material Identification (PMI) device to verify the chemical composition of the received material, results show that the material is questionable.
As a precise test to verify heat treatment condition, microstructure analysis test (metallography) conducted to confirm normalization condition of the material, the resulted grain structure size and growth confirm that one of the received pipes has improper or absence of normalization.
The material rejected as it is proven and confirmed that it is not normalized as per the requirements to avoid further potential of hydrocarbon leakage due to improper material specification. Rejecting the material eliminate the potential of having repeated failure, in addition to 600,000 Saudi Riyal (SR) cost saving as material cost. A common recommendation shared with concerned parties to consider metallography as a mandatory test to be submitted with heat-treated material test certificate (MTC).
Key words: Heat treatment, microstructure, normalization, grain structure, failure, metallography