This document, Guidance on the Safe Operation of Steam Boilers (BG01) has been developed and written by the Combustion Engineering Association (CEA) in consultation with other stakeholders within the boiler industry to help designers, managers and operators of new and existing boiler systems make health and safety and environmental improvements in the industry.
This revision (Edition 2.5) incorporates up-to-date information and best practices relating to the operation of steam boiler plant; hot water boilers are now covered in a separate document, BG02.
This publication should not be regarded as an authoritative interpretation of the law, nor a mandatory legal requirement. However, if the guidance provided is followed, it will normally be regarded as sufficient to comply with the relevant health and safety duties

INTRODUCTION

Guidance on the Safe Operation of Hot Water Boilers (Ref: BG02) is a guidance document intended to assist the designers, managers, operators, maintenance personnel and Competent Persons (CP) of new and existing low temperature and high temperature industrial hot water boiler systems including 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:
  • Loss of water;
  • Over-pressure;
  • Overheating e.g. due to excessive scale;
• Using efficient boiler operation to avoid the excessive pressure/thermal cycles and load swings which can accelerate boiler fatigue or failure;
• Having the proper treatment and monitoring of the system and boiler water to minimise corrosion and scale and avoid microbiological fouling (biofouling), as these problems can result in energy wastage, poor system performance, and the need for early replacement of plant and components.
• Compliance with the various legal requirements, in particular that for periodic examination by a CP in accordance with a Written Scheme of Examination (WSE) for high temperature hot water boilers.

SCOPE

This document applies to all industrial hot water boilers (normally shell boilers), including mobile hot water boilers and waste heat boilers, that fall into the following categories:

• Low Temperature Hot Water boilers (LTHW)
  • Boilers designed to operate below 110°C with a design pressure up to 16 bar gauge; and
• High Temperature Hot Water boilers (HTHW)
  • Boilers designed to operate above 110°C with a design pressure up to 32 bar gauge.

These guidelines cover the types of controls and limiters necessary to ensure safe operation of various arrangements of fully flooded hot water boiler systems both <110^oC and >110^oC.  The term MTHW has not been used in this document for clarity.

The following boilers are specifically excluded from the scope of this Guidance Document:

• Steam boilers and water tube boilers;
• Boilers with a capacity exceeding 37 MW nett rated thermal input;
• Domestic and commercial boilers with a rated capacity less than 100 kW;
• Electric immersion boilers, electrode boilers and steam coil heated boilers (now covered by CEA BG13);
• Hot water coil boilers.

However, just because these boilers are out of scope of BG02, this does not mean that the regulations and general principles in this document should not be applied where suitable and applicable.

Introduction

Blowdown Systems, Guidance for Industrial Steam Boilers (Ref: BG03) is a guidance document intended to provide advice to designers, specifiers, manufacturers, installers and those responsible for the management and operation of steam plant as well as Competent Persons (CP).  It is applicable to both new and existing installations of steam boilers and addresses the following issues:

• The safe discharge of blowdown from boilers;
• The safe use and operation of blowdown vessels;
• The safe use and operation of blowdown pits;
• Proper maintenance and inspection of blowdown vessels and pits including requirements for regular inspection by a Competent Person in accordance with the Written Scheme of Examination (WSE).

Advice was previously provided by Health and Safety Executive Guidance Note PM60 Steam boiler blowdown systems 2nd edition 1998 which has been withdrawn.

Scope

This guidance applies to blowdown arrangements for steam boilers with a maximum evaporative capacity not exceeding 30 tonnes of steam per hour and working pressures not exceeding 32 bar gauge including water tube boilers with a single main blowdown line.

The following are specifically excluded from the scope of this document:

• Water tube boilers with multiple blowdown circuits
• Blowdown tanks of non-circular cross-section
• Design and construction information for blowdown pits. Experience has shown that the state of repair and rate of deterioration are difficult to monitor, and serious undetected leaks have been known to undermine foundations. It is recommended that no new blowdown pits be constructed and a blowdown vessel shall be the preferred option.

SCOPE

This document applies to those industrial & commercial steam and hot water boiler plants, including steam generators, operating at a working pressure of between 0.5 and 32bar gauge and a working temperature between 110°C and 239°C.

The following boilers are specifically excluded from the scope of this Guidance Document:

• Water tube boilers such as would be found at an energy producer;
• Process Boilers with a capacity exceeding:
  • 70tonnes steam per hour;
  • 46MW thermal input;
  • 32bar gauge working pressure;
• Domestic and commercial boilers smaller than 70kW thermal input;
• Manually operated boilers (i.e. those requiring constant human intervention).

This document also excludes from its scope any consequences arising from incorrect steam pressure delivery from the boiler.

The purpose of this guide

Boiler failures can, and do, occur more frequently than are reported.  The common reasons for failures are:

• Non-operation of controls due to sludge accumulation;
• Perforation of smoke tubes due to corrosion;
• Less frequently, but even more serious, overheating, distortion and even collapse of the furnace caused by scale or other deposits.

All of the above can be avoided by correct boiler water treatment.  Poor or inadequate water treatment has been shown to be the cause of more than 95% of all boiler failures.  Often this is as a result of poor management of the water treatment regime by whoever is collectively deemed responsible.

All sources of water contain impurities which are harmful to steam and hot water boilers.  All waters therefore need to be pre-treated and then chemically treated, either to remove these impurities or to minimise any adverse effects.

The Combustion Engineering Association and ICOM Energy Association are very pleased to be able, thanks to member input, to provide this publication relating to water treatment for shell boilers, coil boilers, steam generators and hot water boilers.

Introduction

Guidance on Design and Operation of Biomass Systems (Ref: BG05) is a guidance document intended to provide advice to clients, designers and those who operate and maintain commercial or industrial (i.e. non-domestic) biomass systems using wood in the form of pellets or chips.

Those involved in the procurement, design, construction and the ongoing operation (including maintenance) of biomass systems have duties to co-operate and share relevant information required for the development of a safe system of work. They have a number of legal responsibilities (Duties of care) and to comply with these duties, they should possess or have access to good, current knowledge of health and safety legislation and practice, as well as ensuring personnel they employ are competent to carry out the required tasks safely.

The concepts governing safe design and operation are the same regardless of project size, from the smallest domestic installation, to the largest power station. While, this document focuses on the design and operation of new industrial and commercial installations, the information in this guide will also be relevant for smaller installations as well as the refurbishment or conversion of existing installations.

The content is most relevant to designers, building services designers and those practising as biomass specialists, e.g. for importers of biomass boilers. Those engaged in installing, operating or maintaining biomass systems will also find the content relevant and useful.

Scope

The use of Biomass has increased significantly over the last ten years. This increase is, in large part, due to a perception that biomass is green, clean and sustainable. These conceptions are, in part, driven by market pressure and, in part, underwritten with Government commercial interventions. The rapid development and deployment of biomass has, in some cases, resulted in the un-informed design, review, installation and operation of allied storage and combustion technologies (with attendant fatality and injury).

To date, there have been several serious accidents and at least one known fatality in the British Isles directly connected to biomass heating systems; accidents which could easily have been avoided if a process that ensures safe design and safe systems of work in biomass had been applied.

The most effective biomass systems are the result of a close working partnership between client, architect, mechanical and building services engineer where all aspects of design, management and operation are carefully considered and integrated, with an emphasis on health and safety.

Biomass systems are subject to the same general health and safety principles, codes of practice, and design, installation and operation standards that apply to gas, oil or coal fired boiler systems, including, for example, the provisions of the Pressure Systems Safety Regulations 2000.

The following are specifically excluded from the scope of this guidance document:

• Detailed design information a might be contained within a British Standard Installation Guide.
• Detailed information that would apply to all boilers regardless of fuel and might be regarded as “standard” boiler issues or pressure systems as governed by the Pressure Systems Safety Regulations 2000 (PSSR) or the Pressure Equipment Regulations 1999 (PER).
• Installations where any fuel is pulverised. The hazard of dust explosions presented by such systems requires special design and operating criteria.

Introduction

Hot wells and De-aerators – Guidance for Industrial installations (Ref: BG06) is a guidance document intended to provide advice to designers, specifiers, manufacturers, installers and those responsible for the management and operation of steam plant as well as Competent Persons (CP).  It is applicable to both new and existing installations of hot wells and de-aerators and addresses the following issues:

• The safe and correct provision of feed water for steam boilers;
• The safe use and operation of hot wells and de-aerators;
• Proper maintenance and inspection of hot wells and de-aerators

About this guide

This comprehensive guide deals with all aspects of feedwater provision for industrial steam boilers (shell boilers) and why it is necessary to carefully manage and control the water that is supplied to the boiler.  We trust that by studying the contents and following this advice your boiler plant will operate safely and more efficiently, and provide you with a trouble-free system.  If in any doubt contact the supplier, the system designer or your boiler water treatment specialist for advice.

It is aimed at the Owner, Operator, Engineer and Manager of the boiler plant to help them understand all aspects that affect the boilers and their water supply arrangements, both from a practical operational performance view and for the legal requirements.

It covers who is responsible for the safe and efficient operation of steam boiler plant, and who is responsible for managing the safe operation of this type of equipment.  Ultimately the responsibility lies with the most senior person on site.

With other HSE guidance being withdrawn, and having taken all factors into consideration, The Combustion Engineering Association (CEA) agreed to write this guide with the help of its members.

Within this Guide there are a significant number of legal requirements, regulations and standards highlighted; these regulations and standards are periodically reviewed and they can and do change, but they are as accurate as possible at the time of publication.

CEA cannot accept any liability for the information provided herein; however, be assured that we have consulted widely with our member companies during the compilation of this guide.

Scope

This guidance applies to feed water arrangements using hot wells and de-aerators of various designs for supplying feed water to steam boilers in commercial and industrial installations.  The primary purpose of a hot well or de-aerator is to manage and reduce the amount of dissolved gases in boiler feed water.

1                INTRODUCTION

Thermal fluid heating systems are in common use across many sectors of industry and it is estimated there are at least 2000 installations of such heaters in the UK fired on natural gas and light oil, and many more, often smaller units, utilising direct electrical heating of the fluid.  Biomass is also used in some installations as a fuel.

Thermal fluid heaters are available in a wide range of sizes to suit many different applications and temperature requirements.  Units capable of delivering fluid temperatures to processes at up to 350^oC range from 100kW to around 17MW output, with smaller sizes for providing heat to individual process machines also being readily available.  Some systems also include cooling capability to around minus 50^oC with the correct choice of fluid.

Users of these installations operate in a wide variety of industries including:

• Food and drink manufacturing, breweries and distilleries;
• Printing and coatings industries;
• Petrochemicals and bitumen reactors;
• Fine chemicals;
• Wood panel and composite panel manufacturing;
• Extrusion and moulding processes;

This guidance is for users of thermal fluid systems to enable them to fully understand the capabilities of thermal fluid heaters and the way they can be integrated into their business.  It will also be useful for designers and installers to remind them of emerging legislation and best practices that affect the installations they create, and it will help plant operators and maintenance contractors to keep the installations operating safely and at optimum efficiency.

There are a number of sets of legislation relating to the design, installation, operation and maintenance of industrial equipment such as thermal fluid heaters and associated systems, and reference is made to the most significant of these throughout the text.

Introduction

Temporary Steam and Hot Water Boiler Plant – Guidance for Safe Installation and Use (Ref: BG08) is a guidance document intended to provide advice to all those involved in
the design, procurement, manufacture, supply, installation and use of temporary steam and hot water boiler installations. It is applicable to all temporary installations of boilers and addresses the following issues:

• The Legal and Regulatory framework, ownership and responsibilities;
• The Specification and Design of temporary boiler installations;
• Temporary boiler installation guidance and best practice;
• Operation and maintenance of the temporary plant.

British Engineering Services clearly state on their website under Boiler inspection:
“Wrongly designed, sited or installed boilers can lead to serious failures that can have a major effect on people, production and the plant in general. As a manager or an employer, you have an obligation to ensure the safe installation and operation of your boiler systems, as well as conduct regular engineering inspections as identified by the written scheme of examination, governed by the Pressure Systems Safety Regulations 2000”

SCOPE

This guidance applies to all steam and hot water boilers supplied and installed as temporary plant on a site to replace or supplement existing steam or hot water capacity. Temporary boilers on trailers or in containers are normally available in sizes up to around 8,000 kg/h and 15 bar steam. It includes guidance on design, procurement, supply, installation, operation and maintenance of all temporary boiler plants.

1          INTRODUCTION

Most industrial and commercial processes involve the use of services and fluids that are normally contained within pipes, ducts and wires, and they are generally safe to use if the systems that contain them are correctly designed and installed, and properly maintained.  However, almost all such installations will require disconnection or dismantling at some stage in their life, sometimes many times over, for activities such as repair, replacement or routine maintenance.  Equipment in normal operating mode will usually run safely without any problems, but as soon as the equipment is required to be maintained or repaired it is extremely likely it will need to be isolated from all its sources of energy and any danger.

The common factor is that any commissioning, maintenance or repair activity on those assets must be carried out with all due regard for the safety of people involved and those around them, and every intervention must therefore be preceded by a safe isolation procedure.  However, taking equipment apart inevitably requires that it is put back together correctly, necessitating following of a safe process of reinstatement.

Guidance on the Safe Isolation of Plant and Equipment (Ref: BG10) is a document intended to assist managers, operators and maintenance personnel of new and existing industrial and commercial plant installations in addressing the following issues:

• How to assess risks associated with isolating services for repair and maintenance activities on industrial and commercial plant;
• Producing procedures to ensure a safe working environment for those activities;
• Safe methods of managing plant and equipment isolation activities including Permit to Work (PtW) systems.

The Health & Safety Executive (HSE) published HSG253 “The Safe Isolation of Plant and Equipment” in 1997, an informative document on this subject which was updated in 2006; it is still freely available on the HSE website.  It was conceived and drafted by experienced industrial plant engineers but focussed on larger installations and somewhat complex industrial processes that rightly require rigorous control measures to be put in place for all operation and maintenance activities.  Nevertheless, much of the information in HSG253 is relevant to other plant installations, and short sections are repeated where necessary in this guidance for consistency across industry.

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.

INTRODUCTION
Guidance on Safe Operation of Electrically Powered Steam Boilers (Ref: BG13) is a 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:
• Consideration of all the necessary design and installation aspects relating to an electrically powered steam boiler installation;
• 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 other dangers from events such as:-
o Loss of feed water or low water level;
o Over-pressure;
o Overheating;
o Electrical safety issues;
o The effects of Hydrogen gas possibly arising during operation;
• Using efficient boiler operation to avoid excessive pressure or thermal cycles and
load swings which can accelerate boiler fatigue or failure;
• Having proper treatment and monitoring of the feed water, boiler water, and
condensate to:
o minimise corrosion and scale of the vessel and electrical elements or
electrodes;
o treat the boiler water in order to protect the steam distribution system as well
as the boiler shell and components; and
o avoid carry-over of water with the steam which in turn can cause waterhammer and other issues;
• Compliance with the various legal requirements, in particular that for periodic examination by a Competent Person (CP) in accordance with a Written Scheme of Examination (WSE).
Electrically powered steam boilers are available in a wide range of sizes and types, and in this document the size of equipment is classified as small (<100kW), medium (100kW to 500kW), and large (above 500kW). This is an arbitrary grading simply used herein to differentiate between the different types and features of different sizes of boilers, and may not apply in every case or to every manufacturer.
There are essentially two types of boiler that use electrical power in order to raise steam,
electric boilers and electrode boilers. In this document:

• the term ‘electric boiler’ means an unfired pressure vessel with a visible water level and fully immersed electrically powered heating elements, used to generate steam by indirectly heating the water and

• the term ‘electrode boiler’ means an unfired pressure vessel with a visible water level and with immersed electrically powered conducting probes or electrodes, used to generate steam by directly heating the water through the passage of an electric current through the water.