In April 2021 the UK’s Combustion Engineering Association (CEA) released document ‘BG11’, a Guidance on the Safe Operation of Water Tube Boilers. The CEA, a charitable organisation, promotes the science of combustion engineering to ensure the safe and efficient operation of boilers and other associated plant and equipment. BG11 adds to their range of guidance documents for use within the boiler industries and fills a gap for water tube boilers.
BG11 gives guidance on the design, operation and maintenance of water tube boilers and refers to legislation and practices relevant to the UK. The CEA explains that adherence to the guide will demonstrate safe operational practices. Delta Mobrey, with their years of experience of boiler monitoring and controls and their expertise in boiler instrumentation were invited to contribute to BG11.
BG11 includes guidance on Control Systems and Instrumentation to ensure the safe and efficient operation of the boiler systems. The guide explains that maintaining the correct boiler drum level is critical: if the water level is too low, there is a risk of damage to the boiler drum and tubes and of overheating.
If the level is too high, water can reach and damage the superheaters, or eventually the turbines, causing catastrophic damage.
There are many technologies available to measure and control steam drum levels and triple redundancy whilst mixing technologies is becoming common place. The guide explains the need for a visual indication of the drum level and that this is a requirement of both BS EN 12952 and the ASME Boiler and Pressure Vessel code. Traditionally sight glasses were used, but these are difficult to read and often require regular maintenance. BG11 states that Hydrastep, which uses conductivity probe technology, is an acceptable alternative to the sight glass (BG11 pg 24). It also cites Hydrastep as giving a clear display, both locally at the drum and in the control room and is the preferred solution for steam drum level indication. (BG11 pg 26)
Hydrastep was originally developed in conjunction with the UK’s CEGB. The use of conductivity probes, positioned along a vertical water column, gives a highly reliable method to differentiate between steam and water. The level display can be repeated in the control room and is immediately visible to operators without having to look at monitors.
Alarms or trips can be assigned to chosen levels. The dual redundant design means that even with an internal fault, the Hydrastep will continue to give a drum level indication. It is no surprise that BG11 refers to Hydrastep as having exceptional reliability. (BG11 pg26).
For full information on the safe operation of water tube boilers, refer to BG11. The guide includes a page dedicated to Hydrastep and explains the recommended installation. BG11 is available from the Combustion Engineering Association’s website. For further information on Hydrastep, contact Delta Mobrey.
About Delta Mobrey
For more than 100 years, Delta Mobrey Limited has been a world-leading specialist in the design and manufacture of quality process instrumentation for the measurement and control of fluids and gases in all industrial plant and equipment.
Trusted quality – proven value: quality and reliability have always formed the cornerstone of our success, recognised by industry with international approvals covering every aspect of our manufacturing and product portfolio, together with certifications spanning all areas of hazardous and regulated environments.
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