Safety, inspection and the savings

Steam plant stores a great deal of energy. A boiler holds hot water above its atmospheric boiling point, under pressure; if its shell fails, that water flashes to steam with enormous force. Steam and condensate burn skin in an instant. Boilers and pressure vessels are therefore regulated plant in Australia, with duties on everyone who designs, supplies, installs, operates, inspects and maintains them. None of this is a reason to avoid steam, which has been used safely in factories for a very long time. It is a reason to run it deliberately, with the right people, the right checks and the right records.

This chapter covers SV-8’s safety and inspection arrangements and then draws the book’s numbers together. It sets out the regulatory frame in general terms, the routine checks that keep a boiler safe, especially its low-water protection and safety valves, the in-service inspection regime, isolation for maintenance and the burn hazards of steam and condensate. It then adds up the savings from the measures in earlier chapters. The failure case is a low-water cut-out that failed its weekly test because its chamber had silted up.

This chapter is general information. The specific requirements that apply to any boiler or pressure vessel depend on its type, size, hazard level and jurisdiction, and must be confirmed with the work health and safety regulator, the equipment’s maker and a competent person.

Regulated plant

Under Australia’s work health and safety laws, boilers and pressure vessels are plant, and the model Code of Practice on managing the risks of plant sets out the general duties: identifying hazards, assessing and controlling risks, and keeping plant safe through its life. Certain boilers and pressure vessels, depending on their hazard level, must have their designs registered, and some items must themselves be registered with the regulator before use. Operating some boilers may require the operator to hold a high-risk work licence. The applicable standards, including AS/NZS 1200 for pressure equipment and AS/NZS 3788 for in-service inspection, set out how equipment is designed, inspected and maintained. SV-8’s owner confirmed the boiler’s registration status, the operators’ licensing requirements and the inspection regime with the regulator and the boiler’s maker when it was installed, and keeps the evidence in the plant file.

The checks that keep a boiler safe

A boiler’s most important protection is against low water. If the water level falls too far, the heating surfaces are exposed, overheat and can fail. Boilers are fitted with low-water controls that cut out the burner, and their correct operation is tested regularly, as the maker and the applicable requirements specify, by draining the control’s chamber and confirming that the burner trips.

The safety valves on the boiler and on the low-pressure side of the reducing station, Chapter 4, are the last line of defence against overpressure. They are tested, overhauled and reset by competent people at the intervals required, and their discharge pipes are kept clear and drained.

In-service inspection

Boilers and pressure vessels are inspected in service at intervals set by the applicable standard, the equipment’s condition and history and the competent inspector’s judgement. An inspection may be external, while the boiler runs, or internal, with the boiler shut down, drained and opened. It looks for corrosion, scale, cracking, distortion and the condition of safety devices. SV-8’s boiler is inspected on the schedule set at installation, and each report, with any actions, is filed with the boiler log, the water treatment records and the maintenance history. Those records together show the boiler’s condition over its life, and inspectors rely on them.

Isolation and burns

Maintenance on steam systems is done only with the equipment isolated from every source of steam, depressurised, drained, cooled and proved safe, under the site’s isolation procedure, with locks and tags. On SV-8, steam isolations to equipment that people will open use two valves in series with a vent between them, so that a valve passing steam is detected at the vent rather than inside the equipment. Condensate lines are isolated too, because condensate can back-flow from the return system.

Figure 1Isolating a SV-8 kettle with two valves and a vent

Burns are the commonest steam injury. Live steam is invisible close to a leak; condensate at 143 °C flashes and sprays when a fitting is loosened, even with the steam isolated, as Chapter 6 noted for traps. SV-8’s procedures require face protection and gloves for any work on hot steam or condensate fittings, insulation on every pipe within reach, and warning signs at safety valve discharge points.

Competence and training

Steam plant is only as safe as the people running it. SV-8’s boiler operators are trained in the boiler’s operation, its safety checks and its emergency shutdown, and hold any licence their jurisdiction requires for the boiler’s type and size. Maintenance staff are trained in the site’s isolation procedure and in the hazards of steam and condensate. Contractors who work on the steam system are inducted into the same procedures before they start. Training records are kept with the plant file, and refresher training follows any change to the plant or any incident. The specialist work, such as safety valve overhaul, burner tuning, water treatment and in-service inspection, is done by people competent and, where required, accredited for it.

Emergencies

The procedures also cover what to do when things go wrong. SV-8’s boiler house has an emergency stop for the burner and an isolating valve for the gas supply outside its door, so both can be reached without entering a room full of steam. Alarms for low water, high pressure, flame failure and low feed tank temperature sound in the production office as well as the boiler house. Staff who might be first on the scene know to evacuate the area of a steam release, raise the alarm and stop the boiler from the outside controls, and are trained in first aid for burns, including cooling a burn with cool running water for an extended period and seeking medical help. The procedures are rehearsed once a year.

Records that matter

A steam plant’s records are its memory and its evidence. SV-8’s plant file holds the boiler’s registration documents where they apply, its maker’s manuals and data, the design pressures and safety valve settings of every pressure vessel, the in-service inspection reports, the safety valve test certificates, the water treatment reports, the boiler log, the trap register, the steam users list from Chapter 3, the isolation procedures and the training records. Kept together and current, they let any competent person understand the plant quickly, show inspectors and insurers that it is managed, and make it possible to see trends that no single reading shows. When a key person leaves, the records stay.

Before changing anything

Most steam incidents in small plants follow a change: a new piece of equipment connected to an existing main, a pressure raised to speed a process, a trap replaced with whatever was in the store, a support removed for another trade, as Chapter 5’s failure case showed. SV-8’s change procedure requires every change to the steam system, however small, to be reviewed before it is made by the maintenance engineer, and by the competent person where it affects pressure equipment, safety devices or registration. The review asks the questions this book has worked through: what pressure and temperature, what flow, what pipe size and drainage, what trap, what happens to the condensate, what safety device protects it, and what records must change.

When to bring in specialists

A plant engineer can do much of the work in this book: the calculations, the surveys, the trap register, the insulation and the condensate improvements. Some work belongs to specialists and should be recognised as such. The design of new pressure equipment and changes to existing pressure equipment, the setting and overhaul of safety valves, burner commissioning and combustion tuning, water treatment programs, in-service inspection, and any repair by welding to a boiler or pressure vessel all need people with the specific competence and, where required, accreditation. Knowing where that line lies, and buying the specialist’s time without hesitation when the work crosses it, is part of running a steam plant responsibly.

Adding up the savings

The earlier chapters each put a value on a measure. Together they show how much of a steam system’s running cost is within the plant’s control.

Figure 2How SV-8's steam savings add up to about A$32,500 a year

1. Insulating the 60 m main, against bareA$11,143 a year · 34%
2. Repairing three failed-open trapsA$7,560 a year · 23%
3. Holding boiler efficiency at 85% rather than 82%A$5,529 a year · 17%
4. Recovering flash steam at 190 kPaA$4,660 a year · 14%
5. Raising condensate return from 70% to 85%A$3,618 a year · 11%

The total, about A$32,500 a year, is about 21% of SV-8’s annual gas cost of about A$151,000 from Chapter 2. Most of it comes from measures that cost little: insulation, trap repairs and boiler maintenance pay back in months. Flash recovery and more condensate return need more capital and a matched heat user, and pay back over a few years.

Keeping the savings

Savings in steam systems decay. Insulation is removed for repairs and not replaced; traps fail; boiler efficiency drifts as burners go out of adjustment and heating surfaces scale; condensate lines corrode and leak. SV-8 keeps its savings with four routines already described: the daily boiler log with its gas, steam and make-up meters; the six-monthly trap survey and register; the annual thermal survey of insulation; and the regular burner service with flue gas analysis. Each takes little time; together they are the difference between a steam system that stays efficient and one that slowly returns to where it started. The maintenance engineer reports the steam system’s cost per tonne, return rate and trap failures each quarter alongside the plant’s other performance figures, so the savings stay visible to the people who fund the work. When the numbers slip, the report shows where to look first.

Figure 3The four routines that keep SV-8's savings

	How often	What it catches
Boiler log with gas, steam and make-up meters	every shift, reviewed weekly	falling efficiency, rising make-up, a cooling feed tank
Trap survey and register	every six months	traps failed open or closed, repeat failures
Thermal survey of insulation	every year	jackets and lagging removed for repairs and not replaced
Burner service with flue gas analysis	at the service interval	burners out of adjustment, scaled heating surfaces

A failure case: the silted cut-out

This is an illustration. During a routine test of SV-8’s low-water cut-out, the operator drained the control’s chamber as the procedure required. The burner kept firing. The operator stopped the boiler immediately, as the procedure required for a failed test, and called the maintenance engineer.

The control’s chamber was found partly blocked with sludge from the boiler water, so draining it had not lowered the level around the float, and the float had not dropped. The chamber’s blowdown had been done less often than the maker’s instructions required during a busy period, and sludge had built up.

The detection came from the test itself, which is why the test exists. The boiler stayed off until the chamber was cleaned, the control tested correctly several times, and the boiler’s competent person had reviewed the event. Production lost half a shift, which everyone agreed was a small price; a boiler that had run on with its low-water protection silted up could have suffered damage that took it out of service for months, or worse. The correction also included restoring the chamber’s blowdown to the maker’s frequency, reviewing the water treatment to reduce sludge, and adding the chamber blowdown to the shift checklist with a signature. The event was reported and recorded as the site’s procedures required.

How this applies to a small Australian business

Treat boilers and pressure vessels as the regulated plant they are: confirm registration, licensing and inspection requirements with the regulator, the maker and a competent person, and keep the evidence. Test low-water controls and safety valves exactly as required, stop the boiler when a test fails, and never bypass a safety control. Isolate, depressurise, drain and prove safe before any steam or condensate work, and protect people from burns. Then add up what your steam is costing you, measure by measure, and keep the routines that hold the savings.

Exercise: a first steam survey

A food plant similar to SV-8, with an annual gas cost for steam of about A$151,000, carries out its first steam survey. It finds a 20 m bare section of main costing about A$4,000 a year, four failed-open traps at about A$2,500 a year each, and a boiler efficiency of 80% that a burner service would restore to 85%, worth about A$9,400 a year. What is the total annual saving, and what share of the gas cost is it?

Worked answer. The savings are A$4,000 for the insulation, 4 × A$2,500 = A$10,000 for the traps and A$9,400 for the boiler, a total of about A$23,400 a year. That is about 23,400 ÷ 151,000 ≈ 15.5% of the gas cost, from three measures that would typically pay back within a year. The survey’s own cost, a few days of a technician’s time and some instruments, is recovered within weeks.