CEA BG11 - Safe Operation Of Water Tube Boilers
This document applies to all industrial and commercial water tube steam and hot water boiler plant operating at a working pressure up to 100 bar and utilising a wide variety of fuels or heat sources including fired and unfired heat recovery steam generators (HRSG) where appropriate. Whilst the cut off pressure for this guidance is set at 100 bar there are many aspects of boiler operation and maintenance herein which are equally applicable to higher pressure boilers. INTRODUCTION Guidance on the Safe Operation of Water Tube Boilers (Ref: BG11) is a guidance document intended to assist the designers, managers, operators, maintenance personnel and Competent Persons (CP) of new and existing steam boiler systems in addressing the following issues: • The safe and efficient use and operation of the boiler installation; • Determining adequate supervision and maintenance requirements (levels and competence) that are consistent with the installed plant and its location; • Reducing the likelihood of explosion or other dangers from events such as: o Loss of feed water or low water level; o Over-pressure; o Overheating e.g. due to excessive scale; o High wastage rates on metal surfaces; o Incomplete combustion of fuel; • Using efficient boiler operation to avoid excessive pressure or thermal cycles and load swings which can accelerate component fatigue damage through to premature failure; • Having the proper treatment and monitoring of the feed water and condensate to: o Minimise corrosion and scale; and o Avoid carry-over of water with the steam which in turn can cause steam hammer and other issues; • Compliance with various legal requirements, in particular that for periodic examination by a CP in accordance with a Written Scheme of Examination (WSE) and all relevant environmental legislation. Water tube boilers are large and expensive items of capital plant that frequently have a service life of 25 years or more. It is not possible in this document to cover every type of boiler or every installation scenario for water tube boilers, but the safe operation and maintenance of boilers that have been in service for many years is of equal importance to the design and operation of new boilers; references in the text may include plant items and techniques that are no longer available but still in daily use. One important aspect of water tube boiler design and operation is the availability, maintenance and monitoring of appropriate high quality water supplies. Many volumes of excellent material exist that cover this subject in more detail, so the references to water treatment plant and water quality in this document are here as a reminder of the general principles and the reasons for maintaining good quality water and not a detailed explanation of the individual plant items or techniques required which will be bespoke to each and every installation. Another significant consideration is the selection and treatment of the correct metals and alloys in various boiler parts commensurate with the type of fuel to be combusted. The vast majority of the damage that occurs in a water tube boiler results from corrosion and erosion effects which commonly act in combination to contribute to excessive local wastage rates on metal parts. Water tube boilers come in many shapes and sizes, use a wider variety of fuels than any other boiler type, and serve a range of industries in many different sectors. It would be impossible to cover every aspect of design, operation and maintenance of all such installations in one document. The contributors to this guidance have used their combined years of experience to bring together as many elements as possible, but if errors are found or adjustments to the text are required, please contact the CEA for clarification and for amendments to be made. This document will be kept under review and amended as necessary in the light of emerging technologies, improved working practices, new legislation or any other relevant aspect.