Design and Sizing piping

Ben Youssef Mohamed Amine

SummaryPiping definition what is Piping ? Piping material aspects and trends of corrosion in oil and gas environment & material selection strategy and recommendations Piping Design Design recommandation & way of sizing Stress Analysis Calculation method of flexibility

Pipping Defenition

Within industry, piping is a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping studies the efficient transport of fluid. Pipe is a Tubular item manufactured from metal, steel, aluminum, copper ,plastic, wood, fiberglass, glass,, and concrete etc. meant for conveying Liquid, Gas or any thing that flows.Generally, industrial piping engineering has three major subfields: Piping material, Piping design & Stress analysis

ManufacturingThe most known way of manufacturing pipes is Spiral Welded Steel Pipe

The spiral welded steel pipe is manufactured using hot rolled steel strip which is spiraled at room temperature to be welded. Automatic submerged arc welding is the most commonly used method in the spiral tube production, and the end products come with welding seam both inside and outside.

Manufacturing1. Raw Material Inspection 2. Uncoiling 3. Rough Leveling 4. End Cutting and Butt Welding 5. Precision Leveling 6. Delivering 7. Forming By Inner and Outer Welding 8. Welding Slag Cleaning & Overall Inspection 9. repair Welding, X-Ray Inspection, Scanning, And Re-Inspection By Manual UT 10. Chamfering 11. Hydrostatic Testing 12. auto Length-Measuring and Weighing 13. Coating and Marking 14. storage

Piping Material

1. Material Selection Strategy and recommendations:Material selection shall be optimized, considering investment and operational costs, such that Life Cycle Costs (LCC) are minimized while providing acceptable safety and reliability. The following key factors apply to materials selection: Primary consideration shall be given to materials with good market availability and documented fabrication and service performanceOperating conditionsThe number of different material types shall be minimized considering costs, interchangeability and availability of relevant spare partsDesign life

Piping Material

2. Overview of CO2 Corrosion Models for Pipelines:Corrosion models are set by petroleum companies (e.g. Shell, Total), international organizations,standardization bodies or research bodies or universities.Corrosion prediction models are basically based on two different approachesMechanistic model: It is a model based on chemical and physical approach of the phenomenon.

Empirical model: It is a model based on correlations with laboratory and field data but would have some mechanistic equations as a starting point.

Piping Material

Corrosion models:De Waard Model The model takes CO2 partial pressure, temperature, pH, liquid velocity. The model includes pH calculation only for pure condensed water or condensed water saturated with corrosion products, and requires pH as a separate input when a formation water chemistry is specified. However the model has relatively little sensitivity to variation in pH.

Piping Material

Norsok Model empirical model that takes temperature, total pressure, CO2 content, pH, wall shear stress and glycol concentration as major input. The model contains modules for calculating pH and wall shear stress. Three options for calculating pH are available. Wall shear stress can be calculated from production rates and pipe diameter.

Pipping Material

Key factors governing those models are:Determination of PHOne of the most crucial aspects in corrosion evaluation of oil and gas pipelines is to obtain a realistic estimate of the actual pH in the water phase.

Effect of Protective corrosion filmsThe effect of protective corrosion films on the predicted corrosion rate varies considerably between the models.

Piping Material

Connection with fluid flow modeling

CO2 corrosion is dependent on the flow velocity, and the models have varying degree of flow dependence. Most of the models include a simplified fluid flow calculation based on production rates and pipe diameter, while some only take flow velocity as input and require that liquid flow velocity in the pipeline have been calculated by a fluid flow model.

Piping Material

Effect of oil wettingIt is important to know whether water or oil wets the steel surface since corrosion takes place only when water is present at the surface. If the water is transported as a water-in-oil emulsion or dispersion corrosion can be substantially reduced.Effect of H2SWhen even small amounts of H2S are present, the corrosion products are iron sulfide rather than iron carbonate, since iron sulfide is much less soluble and precipitates much more rapidly than iron carbonate

Piping Material

Top-of-line corrosionThe discussion above concerns primarily corrosion in the bulk water phase. The situation is quite different for top-of-line corrosion when water condenses out in the upper part of a pipeline. The condensing water is unbuffered with low pH, but can become rapidly saturated or supersaturated with corrosion products, giving rise to increased pH and possibility for iron carbonate film formation. The top-of-line corrosion rate then becomes dependent on the water condensation rate and the amount of iron which can be dissolved in the condensing water.

Piping Material

Piping Design

We are designing pipes that must be manufactured after all, that's why we should keep in mind 2 elementary key factors:CostFeasibility(manufacturing, maintenance..)However a good design requires a good sizing, which leaves no other alternative other than going throw the codes and standards of sizing:ASME B31.3:Process PipingASME B31.1:Power Piping

Piping Design

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ASME B31.1ASME B31.3Uses higher allowable stress values Includes torsional stresses in sustain case loadingCode allowable stress is based upon a factor of safety of 4

Plant life is about 40 yearsLess allowable stressNeglect torsional stresses

Factor of safety of 3

Plant life about 20 to 30 years

Piping Design

B31.1 Power Piping: piping typically found in electric power generating stations, in industrial andinstitutional plants, geothermal heating systems, and central and district heating systems. B31.1 isintended to be applied to: Piping for steam, water, oil, gas, air and other services Metallic and nonmetallic piping All pressures All temperatures above -29C (-20F)

Piping Design

B31.3 Process Piping: piping typically found in process facilities such as petroleum refineries,chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants. B31.3 is intended to be applied to: Piping for all fluid services Metallic and nonmetallic piping All pressures All temperatures

Stress Analysis

In order to guarantee the efficiency of piping systems we need to go throw flexibility calculation, in which two software are adopted :CAESAR ANSYS Piping is submitted to a lot of actions such as :Gravity effect,pressurelink action exercised by the Bracketingsolicitation of climatic originVibrationstemperature variation effect

Stress Analysis

Certainly, all of this solicitation affect the piping and result a damage; for example:cracking in singular points loss of sealing in jointStructure deformationFlexibility calculation is based on decomposing the piping system into a number of elements and defining each element extremity then determining stresses and deformations by using beam theory.We shall find two types of stresses: one is due to efforts and the other is due to displacement(thermal expansion)