posted on July 16, 2012 14:40
Chetek, WI: Turbine Technologies, Ltd. (TTL) recently completed certification of its RankineCycler Steam Turbine Power System boiler and power piping to meet the requirements of the American Society of Mechanical Engineers (ASME) Section 1 Power Boilers category.
Since RankineCyclerTM is designed for intermittent educational laboratory use, one goal during the certification process was to design the boiler and piping system to utilize stainless steel materials, rather than standard carbon steel used in commercial systems. This would help to assure units would not suffer any ill effects from corrosion due to storage and long layoffs. This followed the same logic used on the rest of the long-life components comprising the RankineCyclerTM.
During the design review, 410 stainless steel was found to be acceptable for wetted service in a fired boiler under section 1 rules. This finding allowed the whole boiler to be designed around and fabricated from this material.
With any pressure vessel development, safety is the major concern. TTL added some primary safety and performance features to the new boiler system, which include;
· Automatic Low Water Shutoff
· Automatic boiler over-pressure relief valve system
· Shut-off valves for sight glass (meets full scale “valve off for cleaning” requirements).
· Rated Steam Admission Valve
· Rated Boiler Pressure Gauge
Because the system is designed to be used primarily in an educational setting, operational temperatures and pressures were kept as low as possible, while still allowing the boiler to produce super-heated steam for operation. The boiler was certified to 225 psi and 500F. During system operation, system pressure and temperature readings typically peak at 120 psi and 220F, which allows for a very good safety margin.
Each boiler system is individually tested to assure it meets certification requirements. Individual detailed records are published for each boiler manufactured, which include:
· Welding Process Quality Control
· Fabrication Drawings
· Certification Design Summary and Calculations
· Welding Procedural Documents
· Material Grade, Specifications and Certification Test
· Test Gauge Calibration
· Hydrostatic Test Report
· Inspector Certification of Compliance
Upon successful completion of compliance test and review, a “boiler plate” showing the ASME certification markings is applied to the boiler pressure vessel. The “s” stamp indicates certification as a Section 1 Power Boiler by the American Society of Mechanical Engineers (ASME). The “NB” stamp indicates that the boiler is registered with the National Board of Boiler and Pressure Vessel Inspectors (with a specific NB number). The approved certification company is shown.
Maximum Allowable Working Pressure (MAWP), Heating Surface Area, Steaming Capacity, Serial Number and Year Manufactured complete the boiler plate markings.