Reducing The Risk of Pipework Vibration Fatigue Failures
Previous Special Offers
Free Sample – Pipework Risk Assessment Tools
‘Vibration induced fatigue failures’ account for a large proportion of all leaks from pipes, which, in certain industries, creates major HSE concerns. Throughout Q1 2016, pipework vibration specialist VibTech Ltd will be offering free sample versions of its powerful QAT™ pipework vibration risk assessment tool which is designed to help operators to identify and reduce risks. QAT™ is an Excel based tool for calculating the ‘Likelihood of Failure’ (LOF) of pipework for all common excitation mechanisms, such as Flow Induced Vibration (FIV), Acoustic Induced Vibration (AIV), Surge, Cavitation, etc, plus assessment of LOF of Small Bore Connections (SBC) and Thermowells. In fact, the QAT™ painlessly performs all LOF calculations contained in Sections T2, T3 and T4 of the industry ‘best practice’ publication by the Energy Institute: ‘Guidelines for the Avoidance of Vibration Induced Fatigue Failure in Process
21st November 2016: Free! Sample! Small Bore Connection (SBC) Calculator – Type 4
In the last of the SBC tools, this week VibTech will be offering a free fully working sample of the ‘SBC4’ calculation tool which calculates the Likelihood of Failure (LOF) for Type 4 Small Bore Connections (SBCs), which connect between two separate main lines. The calculations show the severity of damage due to vibration induced fatigue, in accordance with the methods presented in the Energy Institute publication: Guidelines for the avoidance of vibration induced fatigue failure in process pipework, 2nd edition, 2008.
Any vibration on either Main Line will cause differential movement between the two ends of the SBC span, inducing cyclic stresses in the welded connection between the SBC and the Main Line which can lead to fatigue cracks, potentially resulting in the release of large quantities of hazardous gases or liquids. As with Type 3 SBCs the usual best practice of minimizing branch length does not apply. Instead pipework must be designed to not be less than a minimum allowable length depending on the type of fitting used e.g. Weldolet. The VibTech SBC4 calculator, makes this calculation very easy, performing complex computations based upon a combination of Location and Geometric parameters.
To receive your free fully functioning sample version of the VibTech SBC Type 4 calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, (http://vibtech.co.uk/contact.html) mentioning the code ‘SBC4’. Watch out for the release of the VibTech ‘TW1’ Tool for Thermowells based upon the closeness of the thermowell natural frequency and the flow-induced vortex shedding ‘wake’ frequency.
9th November 2016 – Free! Sample! Small Bore Connection (SBC) Calculator – Type 3
This week VibTech will be offering a free fully working sample of the ‘SBC3’ calculation tool which calculates the Likelihood of Failure (LOF) for Type 3 Small Bore Connections (SBCs) due to vibration induced fatigue, in accordance with the methods presented in the Energy Institute Guidelines* *Guidelines for the avoidance of vibration induced fatigue in process pipework, 2nd edition, 2008.
Type 3 SBCs are where a SBC branches off a main line and spans a short gap to a nearby fixed structural support. The free span may or may-not support a mass such as a valve. As one end of fixed (to the structure), any vibration on the Main Line will cause differential movement between the two ends of the SBC first span, inducing cyclic stresses in the welded connection between the SBC and the Main Line.
Such failures at the welded connections between SBCs and main lines due to vibration induced fatigue are one of the most common failure mechanisms, where the cracks can result in the release of large quantities of hazardous gases or liquids. The calculation method for Type 3 SBCs is one of the most daunting of all the calculations presented in the Energy Institute Guidelines, involving multiple calculation stages and requiring cross-referencing of calculated values against published Graphs and Tables.
To receive your free fully functioning sample version of the VibTech SBC Type 3 calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, (http://vibtech.co.uk/contact.html) mentioning the code ‘SBC3’. Watch out for the next release of the SBC type 4 tool for SBCs connected between two separate main lines. The VibTech SBC3 calculator, makes this calculation very easy, simply requiring the inputting of the various Location and Geometric parameters for the first span and longest subsequent span.
17th October 2016 – Free! Sample! Small Bore Connection (SBC) Calculator – Types 1 & 2
This week VibTech will be launching a free sample version of the eagerly-awaited Small Bore Connector (SBC) calculation tool which calculates the Likelihood of Failure (LOF) due to Vibration Induced Fatigue for types 1 and 2 SBCs.
Type 1 SBCs are the most common cantilevered type, where an SBC branches off a main line and terminates locally at a valve. Type 2 SBCs are like 2 No. Type 1 SBCs back-to-back on the same line, connecting onto the same main line at 2 separate positions, such as in the case of a bypass line
Failures at the welded connections between SBCs and main lines due to vibration induced fatigue are one of the most common failure mechanisms, where the cracks can result in the release of large quantities of hazardous gases or liquids. Small vibrations in the main line can cause amplified vibration of the cantilevered SBC mass which results in high cyclic stresses at the interconnecting welds, ultimately leading to progressive failure due to fatigue cracking after several million cycles, often over periods of several years.
The Likelihood of Failure (LOF) assessment takes into account a number of factors: Geometric effects – due to SBC geometry and types of fitting e.g. Weldolet Location effects – due to SBC location of main lines close to sources of excitation or pipe supports Main Line LOF – SBC is likely to be excited by main line vibration and consequently, the main Line LOF has an effect on the SBC LOF To receive your free fully functioning sample version of the VibTech SBC Type 1 & 2 calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, (http://vibtech.co.uk/contact.html) mentioning the code ‘SBC1&2’. Watch out for the next release of the SBC type 3 tool for SBCs connected between main lines and fixed supports.
This week we will be launching the Cavitation & Flashing (C&F) tool, which calculates the danger of pipe and equipment excitation due to the shock waves from the rapid implosion of vapour bubbles in liquid systems, which, with repeated events can cause serious damage. With liquid systems, areas of very low pressure can be generated in valves, flow nozzles, orifice plates and in pump suction pipework. If these pressures are low enough, gas bubbles may form, or in the case of flashing, a larger volume of liquid will change state from liquid to gas. The main problem arises when these bubbles later implode generating massive shock waves as the liquid rushes at very high velocities into the void left by the collapsed bubble. These shock waves will create large dynamic forces in the pipe over a section covering 2 partial or full pipe supports (not spring hangers) both upstream and downstream of the low pressure area. The Cavitation & Flashing Likelihood of Failure (LOF) assessment is one of the simpler calculations in the Energy Institute Guidelines, being a function of absolute and differential pressures across a flow restriction and in the case of a valve, the type of valve will affect how likely cavitation will occur, However, the VibTech ‘C&F’ tool simply requires the entering of up to 6 No. basic inputs in order to compute a LOF factor for the cases of Cavitation or Flashing. To receive your free fully functioning sample version of the VibTech C&F calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, (http://vibtech.co.uk/contact.html) mentioning the code C&F2016. Watch out for the next eagerly awaited release of the first of three Small Bore Connection (SBC) LOF calculator tools, covering the Type 1 & Type 2 SBC configurations.
20th March 2016! PIPE SURGE CALCULATOR – Gas Valve Opening (GVO)
This week we will be launching the 3rd in the series of tools relating to SURGE. The SURGE – Gas Valve Opening (GVO) tool calculates the danger of shock excitation of pipework due to Fast Opening Valves on gas systems, which, with repeated cycles can cause serious fatigue damage. With gas systems, the rapid opening of a valve will create transient forces due to the sudden change in momentum. This will create large dynamic forces in the pipe over a section covering 2 partial or full pipe supports (not spring hangers) both upstream and downstream of the valve. The Likelihood of Failure (LOF) assessment calculates the maximum forces in the pipe and compares these against a Force Limit, based upon the pipe size and effectiveness of pipe supports. Similar to the Liquid Valve Opening calculation, the manual GVO calculation is still relatively complex, however the VibTech ‘GVO’ tool simply requires the entering of 10 No. basic inputs: relating to: gas properties; process properties; pipe sizes; pipe supports details and valve type. To receive your free fully functioning sample version of the VibTech GVO calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, (http://vibtech.co.uk/contact.html) mentioning the code GVO2016. Watch out for the next release of the Cavitation & Flashing (C&F) tool.
This week we will be launching the free sample of the SURGE – Liquid Valve Opening (LVO) tool. This calculates the danger of excitation of pipework due to Fast Opening Valves, which, with repeated cycles can cause serious fatigue damage. With liquid systems, suddenly opening a valve creates large dynamic forces in the pipe over a section covering 2 partial or full pipe supports (not spring hangers) both upstream and downstream of the valve. The Likelihood of Failure (LOF) assessment calculates the maximum forces in the pipe and compares these against a Force Limit, based upon the pipe size and effectiveness of pipe supports. Whilst simpler than the Liquid Valve Closing (LVC) calculations, the manual LVO calculation is still relatively complex, however the VibTech ‘LVO’ tool simply requires the entering of 10 No. basic inputs: relating to: fluid properties; process properties; pipe sizes; pipe supports details and valve type. To receive your free fully functioning sample version of the VibTech LVO calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, mentioning the code LVO2016. Watch out for the next release of the Surge – Gas Valve Opening (GVO) tool.
5th March 2016 – Free! SURGE – Liquid Valve Closing (LVC) Pipe Vibration Calculator – The ‘Double Whammy’ Effect!
This week we will be launching the free sample of the SURGE – Liquid Valve Closing (LVC) tool. This calculates the danger of excitation of pipework due to Fast Acting Valves, which, with repeated cycles can cause serious fatigue damage. With liquid systems, suddenly closing a valve requires a very large reactive force to decelerate a potentially large mass of liquid in the upstream section of the line, inducing massive pressures and stresses in long sections of the upstream line Whilst the upstream effect is perhaps obvious, think what happens immediately downstream of the fast closing valve. The liquid downstream initially carries on as normal at its flow velocity, like a subway train leaving the station. This creates a huge vacuum behind it, causing flashing as the closed valve prevents upstream liquid from filling the void. Eventually, this negative pressure causes the downstream liquid to change direction and smash back into the downstream side of the closed valve, creating a secondary large pressure and stress surge in the downstream line – the ‘double whammy’ effect. The manual calculation is one of the more complex ones, however the VibTech ‘LVC’ tool simply requires the entering of 20 No. basic inputs: relating to: fluid properties; process properties; pipe sizes; pipe supports details and valve type. To receive your free fully functioning sample version of the VibTech LVC calculator by email, simply enter your details via the VibTech Ltd website ‘Contact’ page, mentioning the code LVC2016. Watch out for the next release of the Surge – Liquid Valve Opening (LVO) tool.
This week we will be launching the free sample of the Flow Induced Pulsation (FIP) tool. This calculates the danger of excitation of pipework due to Flow Induced tonal excitation when gas flows across the end of a ‘dead-leg’ branch connection and produces a ‘Likelihood of Failure’ (LOF) factor, typically a number between zero and one relating to the severity of the risk. The affect is comparable with the tone produced by gently blowing across the top of a glass bottle and is most severe when the tonal pulsations produced match an acoustic resonant frequency and a pipe structural frequency. The calculation simply requires the entering of 9 No. basic inputs: relating to: gas properties; flow velocity; pipe size; and size and length of the sidebranch. To receive your free fully functioning sample version by email, simply enter your details via the VibTech Ltd website CONTACT page, entering the code FIP2016 in the ‘Comment’ box. Watch out for next week’s free release of the Surge – Liquid Valve Closing (LVC) tool.
