It is widely recognized that UK oil and gas is one of the most highly regulated industries in the world. Over the last twenty years, largely driven by greater regulation and responses to international incidents, the standards regime has become evermore stringent and comprehensive.
Standards inform practice at every level within the industry, from design at the sharp end, to general competency training and every technological and staffing development in between, whether large-scale or small.
Standards set the benchmark for quality, keep projects on target within the compliance framework, giving us peace of mind in terms of both risk and cost management. In other words they are both a legislative necessity and helpful project indicator. At their most fundamental, standards create trust.
That said, there are occasions when we need to ask ourselves if we really understand all the requirements set out by the multitude of standards that we operate to. In particular with reference to possibly one of the most recognisable standards used in the oil and gas sector – Norsok M-501 – which relates to the surface preparation of protective coatings.
Norsok M-501 is an umbrella standard that covers a family of coating systems, including hot dip galvanizing. The variety of coatings covered legislates for the wide-ranging performance capabilities demanded by the various oil and gas environments, both onshore and offshore. It also relates to the variety of application parameters.
Hot dip galvanizing, to BS EN ISO 1461, is the process of coating iron or steel articles with zinc, by immersing the metal in a bath containing molten zinc at a temperature of around 450°C. During the process, a metallurgically bonded coating is formed which protects the steel. In terms of application of the coating, M-501 states that prior to galvanizing, the steel must be blast cleaned. Actually this is not necessary, and would incur avoidable extra cost.
Whilst it is important that steel is prepared correctly prior to galvanizing, this is normally done via a cleaning cycle that is an integral part of the galvanizing process. This includes degreasing the steel, rinsing and also a chemical cleaning stage, which involves the dipping of steel into hydrochloric acid to remove any rust or mill scale.
M-501 also mentions a minimum coating thickness of 125 microns, which misunderstands how the galvanizing process works. With hot dip galvanizing, the surface of the steel is completely covered with a uniform coating whose thickness is determined principally by the thickness of the steel being galvanized.
This characteristic is an important advantage, whereby a standard coating thickness is applied automatically in relation to steel section size, surface profile and surface composition. The coating is not in the hands of the skill of the applicator, but rather the product of a natural reaction, which occurs between clean steel and zinc. In fact the actual coating thickness is often much more than the minimum specified in the standard.
In addition hot dip galvanizing offers a practical advantage to other coatings, such as paint, which are governed by a variety of factors including climate, skill of applicator, equipment, cleanliness and correct curing between coatings. Galvanizing on the other hand, is a factory controlled process not governed by environmental or skill factors.
Although regulation and economics often work independently, the consideration remains, how much will it actually cost to correctly protect steel and comply with standards? Probably less than you think.
The true cost of protecting steelwork from corrosion has to take into consideration two important elements; initial cost of protection and lifetime cost. The latter also includes the cost of maintenance.
Interestingly hot dip galvanizing is often perceived to be more expensive than it is, for which there are two common reasons. Firstly, such a high performance coating is automatically assumed to be expensive. Secondly, the initial cost of galvanizing relative to paint, has changed significantly over recent years. Painting costs have steadily increased whilst galvanizing costs have remained fairly stable. In some instances just the cost of preparing steel for painting can be the same as the total cost of galvanizing that same steel.
Standards can have another effect on choices, in specifying matters such as corrosion protection. Standards can cause a ‘safe haven’ for purchasers. Repeating the specification of the last job, rather than deciding what is the cost effective performance required for the current project, is not always the best solution. These days challenging past specifications isn’t foolhardy, it is an economic necessity. Claiming ‘we’ve always done it that way’ is no longer a good reason to choose a specification.
Iqbal Johal is Marketing Manager at Galvanizers Association, the industry body providing free information and advice on design, specification and performance of hot dip galvanizing.
For further information visit www.galvanizing.org.uk