Oil & Gas - Refining
Refinery piping and equipment operate under conditions that reduce material allowable stresses and introduce dynamic loads: flue-gas and catalyst lines in the creep range, two-phase and slug-flow lines subject to vibration and fatigue, furnace coils absorbing large thermal expansion, and cooling water networks scheduled for conversion to glass-reinforced epoxy. These conditions determine support design requirements, remaining service life and turnaround scope.
Dynaflow provides specialised engineering analysis services to address these challenges directly. As independent consultants working with owners, operators, EPC contractors and suppliers, we combine field measurement, code-based calculation and finite element or CFD modelling, and report results against the applicable code with the model input documented.
ANALYSIS DISCIPLINES
- FCC flue-gas and catalyst withdrawal lines in the creep range
- Fired-heater radiant coils and furnace inlet/outlet piping
- Two-phase lines: feed, stripper, wash oil, hydrofiner service
- Reciprocating compressor and pump systems (API 618, API 674)
- Cooling water and fire water networks, including GRE conversion
- Steam headers, desuperheaters and injection equipment
REFINING SOLUTIONS
High-Temperature Piping Services
At the temperatures reached in flue-gas and catalyst lines, pipe materials lose much of their strength through creep, so the support arrangement determines whether the line can carry its own weight and pressure over its service life
Flexibility and support analysis of FCC flue-gas overhead lines and catalyst withdrawal lines to ASME B31.3, separating the creep-limited sustained stresses from the self-limiting expansion stresses, with iterated spring hanger and restraint design.
Static stress analysis of radiant coils and furnace inlet and outlet piping to RToD, EN 13480 or ASME B31.3, covering material upgrades, anchor relocation, coke build-up effects and outlet retrofits with imposed header displacements.
Assessment of hinged, gimbal and universal expansion joints, and their replacement with expansion loops where joints are to be eliminated, including nozzle load assessment at separators, superheaters and boilers.
3-D finite element analysis to ASME VIII-2 where beam models cannot qualify the geometry: welded stops on bends, manhole penetrations in elbows and tees, reinforcement pad sizing, and derivation of fitting-specific stress intensification and flexibility factors.
REFINING SOLUTIONS
Vibration & Fatigue Services
Two-phase and slug flow generates unbalanced loads at elbows, reducers and tees. A line can pass all static allowables and still fail the dynamic fatigue assessment, so both must be checked.
Flow-regime screening, slug load derivation, and spectrum, harmonic and time-history analysis in CAESAR II to identify the modes contributing most to dynamic stress and design targeted restraint modifications, including viscous dampers where thermal growth precludes rigid support.
Fatigue life calculation to ASME VIII-2 from measured or modelled stress amplitudes and cycle counts, including cumulative usage across changing process conditions and quantified life impact of planned throughput increases.
Pulsation and vibration studies for reciprocating compressors and pumps in refinery service to API 618 and API 674, covering hydrocracker wash water systems, hydrogen compressors and small-bore connections.
Investigation of in-service failures and recurring damage, from fatigue cracking at branch connections to post-trip flange leakage, isolating the excitation mechanism by combined measurement, modal analysis and elimination of candidate sources.
Assessment of slender inserts such as injection quills and thermowells in high-velocity process streams, verifying frequency separation between vortex shedding and structural modes with cross-validated hand, modal and harmonic calculations.
REFINING SOLUTIONS
Flow & Fiberglass Services
Utility and process flow questions, from pump suction uniformity to surge in cooling water networks, and the qualification of glass-reinforced epoxy piping replacing steel.
CFD analysis of refinery internals and utility systems: pump suction line flow uniformity against supplier acceptance criteria, strainer and reducer behaviour, and erosion studies of refractory-lined FCC flue-gas components.
Flexibility analysis of glass-reinforced epoxy piping to ISO 14692, including steel-to-GRE conversion of cooling water headers, small-bore branch flexibility rules, flange load screening and more. Dynaflow is a founding member of ISO 14692 and operates an in-house laboratory for material testing.
Surge analysis of cooling water and fire water networks, pump trip analysis, and root-cause investigation of line failures, applied to complete refinery FW and CW systems.
Engineering of foam, cooling water and fire water systems for refinery tank storage, including hydraulic calculations, system modifications and piping for new fire water pumps.
Projects, Articles & Webinars
Oil & Gas Insights
Verifying Manhole-Equipped Pipe Fittings Using Finite Element Analysis
A manhole interrupts the load-bearing shell of an elbow or tee, so the component is regarded as a non-standard piping fitting. The three fittings here are two 20 inch long-radius elbows, EX-23 and EZ-22, in SA-234 Gr. WP11 Cl. 1, and one 32 inch ASME B16.9 welding tee, FB-11, in
Static Stress Analysis of a Furnace Coil Outlet Piping
Furnace F-501 at a refinery heats crude through radiant coils made of A312 TP316Ti stainless steel. Each coil enters the radiant section at grade level, runs 21 loops parallel to the refractory lined furnace wall, crosses over to the roof section, makes 8 further loops against the roof, and leaves
CFD Analysis of Pump Suction Line Flow Uniformity for Refinery Service
Two identical Visbreaker bottom pumps at an onshore refinery were due for replacement. The existing pumps were of single side suction execution, the new pumps of double side suction execution. For the new pumps a minimum straight length of five times the diameter (5D) was specified directly upstream of the
Dynamic Stress Modelling of a Two-Phase Gas Line Between Hydrocracker Separators
A gas line between the high and low pressure separators of a hydrocracking unit failed in service, probably through material fatigue caused by vibration. An additional 3-way stop was fitted just downstream of the TSO valve to reduce vibration levels, and vibration was then measured at nine locations on the
Vibration Analysis and Flange Leakage Analysis of Crude Furnace Piping
The crude heating system serves one of two distillation trains: crude is preheated in a convection box, heated in the radiant section of the furnace and carried by a feed line to the tower. Crude heating generates two-phase flow, whose fluctuations impose the unsteady unbalanced loads at elbows and tees
Static and Modal Analysis of a Failed Desuperheater Branch Connection
At a refinery, a branch connection designated W31056, the 2″ line that ties in to the high-pressure steam attemperator J-3103 (a desuperheater), failed in service. A similar failure had occurred about twenty years earlier, in 1992. On-site observations report periodic movement of the connecting header, line 6″-S31022, which contains the
Replacing a Steel Cooling Water Header with Glass Reinforced Epoxy
A refinery operator is replacing two existing steel main cooling water headers with Glass Reinforced Epoxy (GRE) piping. The two changes were raised as Technical Change Requests, and this case study covers the second of them, the “lube” cooling water header. The GRE consists of a header and a branch
Slug flow vibration in the two-phase section downstream of an angle control valve
A wash oil line was vibrating in the vertical section downstream of its angle control valve. It has been reported that the vibration amplitude increases with increasing flow, and in the future the mass flow rate may still be increased further. No vibration measurements had been carried out, so the
Vibration Measurement and Fatigue Assessment of a Refinery Wash Oil Line Subject to Slug Flow
Undesirable vibrations were observed in the wash oil line between two vessels during activation of the wash oil flow, most severe in the vertical section immediately downstream of the angle control valve. An earlier study had already identified slug flow as the most probable cause and proposed mitigation measures, and
Slug-Flow Vibration and Expansion Stress in the 10-Inch Two-Phase Lines of a Refinery Furnace
The 10″ inlet and outlet lines of furnace H301 carry two-phase content during all process conditions. Under certain process conditions, staff reported feeling like getting seasick when standing on the platform of the furnace, and the piping was seen vibrating mainly near the furnace. The impact of these dynamic effects
Stress Analysis of a Flue-Gas Overhead Line Operating in the 304H Creep Range
A flue-gas overhead line runs from a third stage separator to a waste heat boiler. It carries gas at a maximum operating temperature of 740 °C upstream of the orifice chamber and is designed for 755 °C in the hot-walled sections. At those temperatures the hot-wall material, stainless steel A240
Flexibility Analysis of a GRE Cooling Water Header Replacement
Two existing steel cooling water headers were to be replaced with Glass Reinforced Epoxy (GRE) piping under two Technical Change Requests. This case study covers the first request, for the main cooling water header “boiler”. The second, covers the “lube” header. A flexibility analysis was required, together with recommendations, to
Slug-Flow Vibration Assessment of an 8-Inch Two-Phase Refinery Line
An 8-inch line carrying two-phase content from a heat exchanger to a gasoil stripper at a refinery had been vibrating for years, mainly in the two shorter horizontal sections, one downstream of the heat exchanger and one just upstream of the stripper. The operator had reported vibration for 5 to
High Temperature Stress Analysis of an FCC Fluegas Overhead Line
A line in the creep range, where the weight loads set the support design The line studied here is the revised fluegas overhead line between the third stage separator and the superheater. It operates at 725 °C in the hot walled sections and 200 °C in the cold walled section,
Flexibility Analysis of a Stainless Steel Radiant Coil Replacement at 650 °C
A coil anchored at both ends, with the cross-over overloaded In a refinery furnace, the radiant coil carries crude. Under a project designated high TAN, the existing carbon steel radiant coil piping is to be replaced by stainless steel, grade A312 TP316Ti. This account presents the stress analysis of the
Reducing Slug-Induced Vibration on Four Two-Phase Hydrofiner Lines
Lines assessed 4 Pipe content Two-phase gas-liquid flow, all process conditions Flow regime, start-up Slug flow Flow regime, normal operation Annular flow Pipe material A 358 type 321, main material Design temperature 400 °C Design pressure 77.5 bar, Lines 1 and 3; 81.0 bar, Lines 2 and 4 Liquid slug
Replacing an Expansion Joint with an Expansion Loop on a 700 °C Catalyst Withdrawal Line
Line temperature 700 °C Design temperature 755 °C Design pressure 4.2 barg Pipe material A 312 type 304H Allowable stresses ASME B31.3 Appendix A Expansion loop 4 inch, 6,000 mm deep Creep-range service on the catalyst withdrawal line A waste catalyst line runs from the regenerator to the waste catalyst