With composite pressure vessels foreseen as a significant industrial growth sector, Mike Skinner, from Seifert and Skinner & Associates, talks us through their approach and how the composite solution offered by ComposicaD and ESAComp provides efficient design and analysis to meet the emerging markets.
About SSA - Seifert and Skinner & Associates
With offices in USA, Europe, Asia and South America, SSA - Seifert and Skinner & Associates is an engineering consulting company that focuses on design, development, consulting, training and other composite-related products and services. Founded by Mr. Axel Seifert and Mr. Michael Skinner, both partners have spent all of their careers working in the composites industry and offer a combined wealth of expertise from design of composites, filament wound structures, process optimisation and filament winding machine design. The aim is to provide a range of products and services to "Facilitate Composites Technology".
What is a CPV?
"We mainly work with filament wound, composite vessels with nonstructural liners, i.e. plastic, where the composite carries the loads. In the categories of pressure vessels, these are Type IV", says Mike.
What are its benefits / limitations compared with conventional all metal pressure vessels?
"In general terms, weight savings over conventional all steel vessels come from increasing the proportion of composite in the construction".
For example : Type I, all metal steel constructions are the heaviest 3.0 lb/L (1.4 kg/L), but the cheapest to manufacture, whereas values for Type III and Type IV are typically 0.75 lb/L (0.3 kg/L) to 1.0 lb/L (0.45 kg/L) but are significantly more expensive to produce (> 3x).
Where are they traditionally used and what are the emerging markets?
Originating in the aerospace sector, such vessels are routinely used for propellant storage and rocket motors. CPV have become contenders for applications looking for weight-efficient storage and transportation of gas. From personal protection equipment (breathing apparatus); small CNG vessels 700-800 litres internal volume; large vessels designed to fit into conventional transport containers (40 ft x 4 ft dia.; approx. 12m x 1.2 m dia).
For example : A bus or commercial truck, fitted with Type III and Type IV vessels, could reduce the weight of the gas containment system by more than 1,000 lb (454 kg). This in turn gives improved fuel economy, increased load-carrying capacity...
Composite vessels offer improved gas containment pressures and better energy storage density, with Type III and Type IV vessels often the most practical solution for high-pressure applications: NGV natural gas powered vehicles, a rapidly expanding market, are expected to be equipped with high-pressure (>200 bar) fuel storage systems.
Composites offer improved corrosion resistance and lower maintenance, along with longer service lives compared with Type I and Type II vessels. Impact tolerance concerns can be addressed by innovative design including protective bumpers and support structures.
One report predicts "annual production approaching 12.5 million pressure vessels and could grow to more than 20 million units, yearly, within a decade. Delivery of more than 150 million pressure vessels is forecast between 2014 and 2023". 
Are there particular design issues with CPV?
The design-drivers are different between aerospace applications, producing 1 or 2 off, and industrial applications with quantities of 100s and 1000s identical units.
"Aerospace is performance driven, whereas for industrial: we're talking price," explains Mike.
"Overdesign is the enemy", says Mike, "Vessels having too much material are heavier than they need to be and cost too much. Often there is no time to optimise designs, which is where using a design tool like ESAComp early in design cycle saves time and allows us to iterate a design", Mike continues, "This also means we make fewer prototypes during design-development, and that means material cost savings of about $4-5,000 for typical size vessels; up to $50-60,000 for a large 40 ft x 4 ft dia. vessel".
"Another concern is the time it takes to get these vessels approved. Here again, analysis tools can hopefully help speed up this process. In one project, it took 7 years to get US approval on a tank transport for fuel for trucks".
Collaboration between Componeering and SSA
Under the ComposicaD trademark, SSA offer a range of software packages that generate the patterns needed by CNC equipment to produce composite parts by filament winding.
Having identified a new approach to consider a part as a whole (layers and geometry), SSA began looking for low cost analysis tool that, with a collaborative project, could be compatible with ComposicaD.
"The objective was to bring to the market a reasonably-priced, easy to use, filament winding design and analysis tool". Mike continues, "Componeering's ESAComp software more than met our needs. Together we developed an interface between both of our packages".
"Whereas ComposicaD approaches the product development from the processing aspect, i.e. how to make the part, ESAComp considers the function - does it carry the specified loads?" explains Mike.
"With the common interface we ensure that the shape and materials of the CPV automatically transfer between the products. This set of tools provides designers with a highly-efficient environment for design studies. You can see more about this in our joint webinar". [http://www.esacomp.com/webinars/recorded/116-webinar-form-composicad-esacomp]
For instance, global strains of the candidate CPV tank can instantly be visualized and local studies for hot spots can then be performed. Results of the FEA indicate to users if any parameters of the manufacturing process need to be changed in ComposicaD. Then the design modification can verified in ESAComp.
"Within the Metal-series, ESAComp is available for the ComposicaD 'Silver' package for tanks and pressure vessels. Using parametric modelling, automatic lamina thickness generation and simple transition patterns, it allows quick and easy, comprehensive pattern generation for filament wound tanks and pressure vessels".
More information about ComposicaD:
|USA - Michael Skinner - Managing Associate
Seifert and Skinner & Associates, Inc.
|EUROPE - Axel Seifert - Managing Associate
Seifert and Skinner & Associates, BVBA
More information about ESAComp for ComposicaD:
Technical Support is provided by Componeering's Harri Katajisto who has many years of experience in the design, analysis and optimisation of all manner of high-performance composite structures.
© 2016 Componeering Inc, by Jo Hussey