Fulton’s new VSRT 250 steam boiler builds on the innovation of its revolutionary predecessor to promise high efficiency and low costs of ownership. David Fowler reports.
With the launch of its VSRT steam boiler Fulton threw away the rule book, to produce the first departure in boiler design since the advent of the vertical tubeless boiler over 50 years earlier.
Now, with the new VSRT 250 it is set to do the same again for the higher output end of the vertical tube boiler market.
Launched in the US earlier this year, the VSRT 250 will arrive on the UK market towards early 2020. Its output of 2.5MW puts it squarely in the scope of the EU Medium Combustion Plant Directive, where a key requirement is reduced NOx emissions. Further models, the 100 and 150 (1MW and 1.5MW) are expected to follow.
The new boiler is not a scaled-up version of the original VSRT (for vertical spiral rib tubeless), which is available in seven models up to the VSRT 60, providing 600kW output. “It’s a totally different design again to meet the requirements of a bigger boiler,” says Fulton UK national consultant specialist Leigh Bryan, whose role is to assist specifiers and M&E contractors.
Like its predecessor, the boiler is the work of a team led by Dr Carl Nett, former head of United Technologies Research Center.
Siting the VSRT 250’s burner to fire in from the bottom of the boiler made possible a four–pass design in which the water is heated first by the furnace itself, then three separate heat exchangers – one more than conventional configurations. This maximises thermal efficiency and reduces thermal stresses.
As standard, NOx levels are expected to be around 20ppm, equivalent to 35-45mg/Nm³, against the MCPD requirement of 100 mg/Nm³ (at 3% O2 ref). The company can also offer a 9ppm alternative.
As with the original VSRT boiler, a turndown ratio of 10:1 is possible. The burner subsystem, designed by Fulton, has a premix mesh surface burner head and an LMV burner management system by Siemens: “It’s a recognised burner controller which will be fully supportable, and customers will be conversant with the design,” says Mr Bryan.
Unlike the smaller version, the VSRT 250 comes with oxygen trim as standard, providing continuous optimisation of combustion. Overall the boiler is monitored by a new, more sophisticated boiler management system, Pure Control, which also allows boilers to communicate with each other so they can be cascaded if required.
Efficiency is expected to be on a par with the original VSRT at 82.5% at 10 bar steam pressure. At this pressure the boiler will produce 99.75% dry steam, for optimum efficiency of the overall steam system.
On a practical level, the vertical configuration results in a much smaller footprint than a horizontal boiler, typically a third of the size because of the tube pulls in a horizontal fire tube boiler, while at the same time not being excessively tall. “In most boiler houses it will fit quite easily,” Mr Bryan believes.
One of the VSRT 250’s biggest selling points, however, is expected to be reduced maintenance and low cost of ownership.
“Maintenance is reduced because there are virtually zero thermal stresses,” says Mr Bryan. There are no tubes and therefore no requirement for a five-yearly SBG01 ultrasonic test to check furnace and shell welds. All that will be necessary will be a hydrostatic pressure test every five years. Commissioning is also relatively problem-free with all boilers delivered to the UK fully test-fired.
The new boiler has been well received in the US market, as has the original VSRT worldwide. In May in the UK it received the Product of the Year award at the Institution of Gas Engineers and Managers/Energy & Utilities Alliance Gas Industry Awards, along with two industry awards last year following its launch.
As a result Fulton has high hopes for the VSRT 250 in the UK, expecting it to be popular particularly “in markets where we’ve historically been strong, but we’ve been limited by the size of vertical tubeless product we’ve been able to offer – such as small to medium hospitals, food and beverage and process industry,” Mr Bryan says.