Using alternative analysis and test procedures to avoid unnecessary downtimes

Hamburg: Periodic testing of plant and equipment subject to mandatory monitoring is a requirement of the German Ordinance on Industrial Safety and Health (BetrSichV). In addition, operators of such plant often have to carry out comprehensive maintenance and repair work due to component wear. The result: companies regularly have to shut down their production for significant periods. Although the expense of the resulting downtimes is naturally calculated into production costs, the experience of TÜV NORD shows that both the duration and the financial impact of production standstills can often be reduced and the times when they occur can be more conveniently planned.

Testing of operational safety as well as maintenance and repair of industrial plant and machinery are often associated with standstills in production. This necessarily gives rise to a great deal of expense. “In the case of legally required tests, most of the costs are not even due to the tests themselves. Often the loss of production alone causes immense reductions in sales. This means that every single day when plant is not at a standstill is valuable“, explains Susanne Magiera, pressure vessel systems expert at TÜV NORD. As a provider of testing services, TÜV NORD advises all plant operators to make use of the new opportunities that have been available within the BetrSichV ordinance since 2015, and to develop a corresponding test concept for their pressurised systems. Within the framework of such a concept, alternative tests methods can be specified which mean that the plant components do not have to be opened, emptied, cleaned or rendered gas free and that insulation does not have to be removed. Operators must have their own estimation of the plant confirmed by an accredited inspection body (ZÜS) such as TÜV NORD. If the concept is acceptable, the alternative test methods can be used, which means that plant downtimes can be reduced or even avoided altogether. “Based on our long years of experience, we can also make use of the wide range of alternative test procedures in quite special cases – for example in the case of very low material thicknesses. This means that the expenses associated with legally required testing are considerably reduced and companies avoid losses in output due to days when the plant is unnecessarily at a standstill”, adds Magiera.

Preventive measures and damage tolerance analysis

Taking measures to prevent damage can also play an important role when it comes to process plant which is subject to stress and wear and tear. “Even small changes – such as changing the position of a pipeline bracket or modifying the flow rate of a pump – can prevent some damage to plant and equipment”, says Magiera. If components that are subject to heavier loading such as pumps, flanges, pipe walls and bolts are already showing damage due to wear, ageing, or temperature and pressure fluctuations, they are often replaced quickly. However, by analysing the actual situation, the real permissible operating lifetime of damaged components and equipment can be determined. This means that necessary standstills can be fitted into the operational flow in the best possible way and can be postponed until a later date if appropriate.

By means of the damage tolerance analysis, flexible inspection intervals based on real plant use can be determined. This method is one possible way of extending inspection intervals as laid down by BetrSichV. In addition, this method allows maximum utilisation of the lifetime of all components, without compromising plant safety. This means that components need only be replaced when actually necessary.

Use of innovative robot technology

In areas of the plant that are difficult to access, it is possible to make use of technologies and calculation programs which save the operator complex disassembly tasks and which above all save time. An example of this is the use of “pigs” which collect data in underground or submerged pipes and high-pressure pipelines. Crawlers can be remote-controlled and move on magnetic wheels to hazardous areas that are difficult to access – such as thin-walled tank covers and domes – in order to record material thicknesses. And flying robots (drones) can be used to check inaccessible areas for possible damage. The results of all these investigations can be represented in three-dimensional form using 3D printers.

Potential too rarely used

However, the experience of TÜV NORD shows that the advantages of these methods are not yet widely enough known. As Magiera says: “Especially when speaking to medium-sized enterprises, we hear again and again that it is a challenge to provide resources in terms of manpower and time in order to examine the subject of alternative test methods more closely. But it is precisely in such companies that there is a great deal of unused potential as regards reduction and optimum planning of downtimes.”