Steam Boilers – IS Range
The IS range of boilers is available from 36 kW to 2106 kW – steam output up to 3345 kg/h (7374 lb/h) from and at 100:C, at working pressures up to 10.3 barg (150 psig). Higher pressures are available.
With their large water capacity, IS boilers act as steam accumulators. This feature enables the boiler to meet steam demands in excess of the rated output. As an example, the IS7 operating at 10.3 barg (150 psig) can generate twice rated output for 7 minutes for a pressure reduction of 3.4 bar (50 psi).
The boilers use Incoloy sheathed immersion elements of a low surface loading. This combined with high quality components (including Mobrey float level controllers) ensures a long, trouble–free life with the minimum of maintenance.
The boilers are available as a free-standing boiler complete with all controls mounted on a mild steel chassis with a separately mounted feedwater pump, or as a packaged unit with high level feedwater tank.
IS Specification – 380V & 415V – Other Voltages Available
Electrical Supply
3 phase, 3 wire (voltage up to 690V and frequency 50/60Hz to be specified).
Electrical Connection
Top entry cables.
Vessel
Designed and manufactured to BS5500. Independently inspected by Royal and Sun Alliance Insurance - full certificate is issued with completed boiler.
Standard Pressures
Working pressure 10.3barg (150psig)
Design pressure 11.4barg (165psig)
Higher pressures available
Insulation
High performance Rockwool covered by a galvanized steel lagging sheet.
Mechanical Connections
BS4504 PN16 and BSP(Rc) are standard, alternatives available at no extra cost.
Elements
Long-life, Incoloy 800 sheathed with low Watt density. Individual elements are mounted on the element flange with 316 stainless steel compression thermocouplers. This ensures that all water seals are adjustable from the outside of the vessel and enables simple individual replacement of elements. The element flange assembly is removed from the vessel on a skid arrangement
Controls
Moulded case circuit breaker fitted with electronic overload protection. Emergency stop. Boiler off/on switch. Audible alarm mute switch. Voltmeter with phase selector switch. Ammeter. Individual selection of stages. Lamp test switch. Low water test switch. High water test switch. Pressure modulating controller.
Water Level Control
Mobrey float control for high water, pump on/off, 1st low water and 2nd low water, 3rd low water level in form of element overheat thermostat.
Control Panel Indications
Controls circuit healthy. Boiler on. Feedwater pump on. Feedwater pump tripped. Individual stages on. High water level. 1st low water level. 2nd low water level. Element overheat. High pressure. Voltage. Current.
Remote Control/Indications
Boiler on/off. Grouped alarm. Other indications available as required.
Fittings and Mountings
Pressure gauge. Water level gauge with blowdown cock. Blowdown valve. Steam valve. Safety valve.
Feedwater Pump
High pressure, heavy duty, centrifugal pump with TEFC motor.
Optional Equipment
Thyristor load regulation
Earth fault protection relay adjustable 300mA to 30A
Conductivity controlled intermittent Blowdown.
Sample cooler
Magnetic water level gauge.
Optional Thyristor Control Description
References to pressure apply to steam boilers
References to temperature apply to water boilers or fluid heaters
The thyristor controlled boiler has the same vessel and comprehensive controls, low surface loading Incoloy sheathed elements mounted with thermocouples and easily withdrawal element flanges as our standard boiler.
The only difference is the thyristor control of load regulation with no direct on–load switching by contactors.
Load regulation is by means of a burst–firing thyristor controlling the three phase load. Thyristor switching occurs at zero voltage.
The analogue output from a pressure or temperature transducer is input to a process controller whose logic output is input to the thyristor.
At start-up, with 100% demand, the thyristor output is 100%. As the boiler pressure or temperature approaches the set point, the process controller modulates the output of the thyristor to maintain the pressure or temperature at the set point. The thyristor continues to modulate to ensure that the energy input is precisely matched to the demand.
The benefits of using this system are:
- Smooth load changes from 0–100%.
- Increased element life due to the reduction of thermal shock on the element resistance wire.
- Precise matching of load to the demand.
- Very low maintenance costs.
