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Steam boilers can explode like bombs

Posted Feb 28 2013 5:29am

Steam boilers are potential bombs, as was seen at the beginning of this month when an improvised boiler exploded with devastating force at a farm in Mount Hampden, killing three farm workers instantly.

Boilers are packed with energy. They can explode with devastating force if not manufactured, installed and used with care and if not well maintained and periodically inspected by professional inspectors
It is for this reason that there is legislation, the Factories and Works (Boiler) Regulations, RGN 279 of 1976, covering the manufacture, installation, use, maintenance and inspection of boilers.

Steam boilers play an important role in many industrial sectors including the textile, sugar, tea and paper manufacturing sectors, hospitals, prisons, hotels, power generation, agriculture and forestry. The steam energy produced is used for energising materials and machinery and for process needs. In the case of the farm in Mount Hampden, the improvised boiler was intended for tobacco curing.

The minimum compliance required by the legislation is that the equipment be manufactured to a standard approved by the Chief Inspector of Factories and Works under the supervision of an approved Independent Inspection Authority and that it should not be used without a valid certificate issued by NSSA upon satisfactory commissioning under the supervision of a NSSA Inspector of Factories and Works.

Many users, especially in the farming areas, are not complying with this requirement. Apart from compliance being a legal requirement, it is better to comply than to risk losing members of the family, employees and property through accidents caused by using dangerous boilers.

Even where rigorous safety requirements have been observed in their manufacture and operation, boiler parts do wear out, creating some undesirable structural weaknesses.

Boilers are subjected to harsh operational conditions, such as corrosion, vibration, stress, pressure, fatigue, temperature differences, pulsation and erosion.
These can with time lead to dangerous conditions which require a trained inspector to detect them.

There is a statutory obligation to have boilers inspected regularly to maintain a safe work environment, control unsafe acts and conditions and ensure operational efficiencies. Inspections should be carried out by operators and at appointed times by the qualified NSSA Factory and Works inspectors appointed according to the law.

The inspection activities performed by operators include routine heat surveillance, draft or excess oxygen adjustment and assessing heat balance in the boiler.

The required tasks are normally itemised in unit operation manuals, on itemised checklists, or are programmed into portable “intelligent” devices. The significant results of these monitoring activities should be recorded in a unit log book.

It is dangerous to ignore the value and advice of a NSSA Factory and Works Inspector. A hazard that goes unnoticed can make itself known violently.

Some boilers do not comply with any standard. A good example of this is the makeshift boilers being used on some farms.

Thinning of the boiler shell may be caused by corrosion or erosion due to poor quality fuel, weather and feed water. Ultimately, if this goes unnoticed, severe thinning may occur and lead to an explosion.

Excessive pressure, caused either by the absence or failure of safety measures or insufficient release of contents through safety valves, can cause such a high build-up of pressure that an explosion may occur.

A low water level, caused through incorrect operation, faulty feed pumps or leakage may result in the burning of boiler tubes, bursting of the boiler shell in fire tube boilers or permanent deformation of the steel drum in water tube boilers.

The metal from which the boiler is made may deteriorate as a result of scaling or overheating due to a poor quality of feed water.

There are three main causes of boiler loss or damage. These are human failure, product faults and operational errors.

Human failure includes faulty handling, negligence or wilful acts, which may include the operation of boilers without certificates.

To reduce the likelihood of loss due to human failure, it is necessary to select suitably trained people for the operation, maintenance and servicing of boilers.

It is also necessary to install on the boiler easily noticeable fittings and control elements, warning devices and recovery mechanisms.

Manning levels should be adequate.

Only government-approved persons should be allowed to service boilers. That is a legal requirement.

Operational faults include inadequate maintenance, overheating due to scaling and failure to measure and regulate the pressure. To guard against loss due to operational faults, regular servicing, maintenance and overhauling is important. There is need for constant control and inspection of measuring devices.

Product faults include faulty material, faulty design or construction and faults in workmanship or installation.

To prevent loss due to product faults, there is need for purposeful inspections by NSSA Factory and Works Inspectors at appropriate times. Components that have led to damage to boilers as a result of deficiencies should be replaced when it is noticed that they are deteriorating.

To prevent catastrophes due to boilers exploding, it is important that all boilers are registered with and inspected by the Factories Inspectorate to ensure compliance with the safety regulations governing them and their use. Failure of legally registered and professionally operated boilers is rare in Zimbabwe.

Talking Social Security is published weekly by the National Social Security Authority as a public service. There is also a weekly radio programme, PaMhepo neNssa/Emoyeni le NSSA, discussing social security issues at 6.50 pm every Thursday on Radio Zimbabwe. Readers can e-mail issues they would like dealt with in this column to or text them to 0772 307 913. Those with individual queries should contact their local NSSA office or telephone NSSA on (04) 706517-8 or 706523 5.


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