Full steam ahead for safe fun at the fair

Steam engines pull in crowds at hundreds of events each year. But the ageing plant must be looked after carefully, says Bob Garnett at RSA Engineering

Steam propulsion may be a technology from a bygone era but it still brings pleasure to thousands. The heritage engineering market generates big revenues. Just one event, the Great Dorset Steam Fair, attracts 100,000 visitors in just a few days each summer.

A handful of historic boilermakers has fought against the odds to remain in business. One of the oldest, Israel Newton, was established in 1804 and is still in operation in Derbyshire. There are other specialist boilermakers that, as well as helping to keep heritage plant alive, provide apprenticeships to preserve skills for the sector.

As a result, steam raisers can be restored to working condition, and maintained to high standards. This has brought a requirement for an increase in the number of boiler inspection companies that can ensure that safety comes as a given.

Railway locomotives must comply with the Pressure Systems Safety Regulations 2000 (PSSR). 

Full-size road steam engines are mostly fitted with a Stephenson-type boiler operating at pressures of 250psi or less. It is not uncommon for these boilers to be fitted with superheaters. There is debate as to whether the Health and Safety at Work Act and PSSR apply to all these engines. The Health and Safety Executive’s view is that the person inspecting the steam plant is at work so PSSR applies at that time. 

Steam cars operate at relatively high pressure, being fitted with flash steam, coil or drum-type boilers. In this sector there is considerable reluctance to embrace the requirements of PSSR.

Marine applications also have to be considered. Historic steam passenger boats and tugs or small cargo vessels are generally fitted with shell-type boilers but some have water-tube boilers. Their operators have to broadly follow PSSR requirements plus rules from the Maritime and Coastguard Agency. 

All these groups require examination at intervals outlined in a written scheme. Normally out-of-service plant should be examined every 14 months. There are additional examination requirements at seven years which may under certain circumstances be extended to 10 years. These apply to riveted and locomotive boilers.  


Bob Garnett is an inspection specialist with RSA Engineering

A common misconception is that an examination with lagging removed and maybe a hydraulic test constitutes a seven- or 10-year test. This is untrue. The boiler certificate generally runs for a maximum of 14 months at which time another examination is required. The competent person will specify additional tests and examinations after seven or 10 years.

It is standard practice for major repairs to be carried out during the seven- or 10-year examination. Locomotive boilers will normally require removal from the locomotive frames. The tubes should be removed and the boiler thoroughly examined internally and externally. Any remedial works to the boiler barrel may require removal of the longitudinal stays, so that access to the boiler barrel and restricted areas of the firebox is possible. These examinations include a search for stress corrosion cracking on the flat plate radiuses and between stays.  

Road engines are exposed to the elements and suffer from corrosion to the boiler barrel between the chimney and cylinder block. Firebox corrosion is often a big problem.

Some fixed and marine boilers are only steamed on five or six days a year. They can suffer from corrosion under lagging from being kept in damp boilerhouses.

If unboiled, untreated water is left in a boiler for a long time it can lead to severe corrosion. Water treatment is generally welcomed but problems can be encountered with over-treatment or the addition of undissolved chemicals.

Repair techniques have improved, although there is occasionally a tendency to “weld up” all types of failures. Welding may simply cover up the defect without adding material strength. Repairs should be formally reviewed to ensure continued safety. 
If a replacement plate is required, it may be flat or forged to the original shape. Use plate of the correct material and dimensions. 

Hydraulic riveting, backed up with handheld pneumatic hammers for rivets that are inaccessible to the hydraulic apparatus, can produce more reliable repairs than earlier techniques. But some repairs have been destroyed through the use of incorrect rivet material.

Heritage engineering presents special maintenance challenges. But these can be handled, and the sector can continue to delight the public.