Typical Arrangement 3 This shows the minimum equipment requirements for the lowest degree of supervision, where no boiler operators could be on-site for up to 72 hours and with status monitoring and boiler safety shutdown by a remote location/telemetry system. New installations shall be manufactured to BS EN 12953, which requires additional limiters to be fitted. With typical Arrangement 3 the following factors need to be considered: x Attendance: The site must be visited and checked by a boiler operator at least every day. Visits may be extended to 72 hours where additional monitoring is included such as that shown on the diagrams below. In any case, risk assessment may determine a more frequent visit is needed for reasons other than the level of automation. Boiler status is monitored from either an on-site or off-site location. x Equipment integrity: This arrangement is the highest level of automation requiring the greatest degree of confidence in the boiler controls and equipment. Low water level devices and an excess pressure device must be high-integrity. Combustion control system shall be high-integrity. Auto TDS and bottom blowdown shall be installed on any boiler left unattended for 24hrs. All control equipment must be fail- safe. Some types of high integrity self-checking photocell need professional adjustment and setting, and the manufacturer’s recommendations and t imescales must be followed. x Boiler house fire protection: Fire detection, fire alarm and automatic shut-off of fuel oil systems must be provided. For gas firing, gas detection and alarm shall also be considered. x Minimum frequency of routine testing: o Low water level devices fitted directly to the boiler: o Weekly: The low water level cut-out and lock-out shall be tested by lowering the boiler water level by evaporation and controlled blow down. Discharge temperature to drain must not exceed permissible limits. o Low water level devices in external chambers fitted with automatic blow down facilities: o Daily: External chambers shall be automatically blown down at intervals typically at least every six hours. Discharge temperature to drain must not exceed permissible limits. o Weekly: In addition, the low water level cut-out and lock-out shall be tested by lowering the boiler water level by evaporation and controlled blow down. Discharge temperature to drain must not exceed permissible limits. x Level indicators (gauge glasses): At least once every three days, manually blown down. x Water treatment: o At least every three days, testing and recording of the feed water plant parameters, hotwell temperature and water sample results including pH, turbidity or other measurements of boiler water; o Water treatment plant and chemical dosing plant shall have flow monitoring for feedwater and chemical dosing integrity, and level monitoring for salt and chemical stocks; o Condensate monitoring and feedwater/dosing plant shall alarm if parameters are not met.
BG01 Guidance on the safe Operation of Steam Boilers Edition 2 – © 2019
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