Stauff ACT Application Problem

ANTI CORROSION TECHNOLOGY THE APPLICATION PROBLEM THE PRODUCT SOLUTION

The Stauff Anti Corrosion Clamp provides Efficient Prevention of Crevice Corrosion under Pipe Clamps on Stainless Steel Pipework with Middle and LongTerm Cost Savings due to Extended Service and Maintenance Intervals.

Stainless steel instrumentation pipework

Crevice Corrosion on Pipework

The Application Problem: Crevice Corrosion on Pipework

Stainless Steel Pipework

Stainless steel pipework on offshore oil and gas platforms is used over a wide range of temperature, flow and pressure conditions, e.g. for process instrumentation and sensing, as well as for chemical inhibition, hydraulic or utility lines.

The typical tubing material selected for these particular applications is 316 stainless steel, although in more recent times other tube materials have been utilized to try and counteract the offshore corrosion issue.

In all major offshore oil and gas regions – including the Gulf of Mexico, the North Sea, the Gulf of Guinea and the China Sea – corrosion of 316 stainless steel pipework can be observed, and has been a researched and well documented problem as well as a costly and time consuming issue with regard to maintenance processes for many years.

Crevice corrosion clearly visible

Crevice corrosion clearly visible

Pitting Corrosion

One of the most prevalent forms of localised corrosion is pitting corrosion: Under certain specific conditions – particularly involving chlorides (such as sodium chloride in seawater) and exacerbated by elevated temperatures – small pits can form in a stainless steel surface.

Dependent upon both the environment and the stainless steel itself, these pits may continue to grow and eventually lead to perforation of tubing walls and leaks, while the majority of the surface may still be totally unaffected.

Pitting corrosion is often quite easy to recognise: small individual pits and – in later stages – sometimes deeper and connected pits can be observed by visual inspection with the unaided eye.

Crevice corrosion as it can be formed under regular plastic clamp bodies

Crevice corrosion can be formed under regular plastic clamp bodies

Crevice Corrosion

Another dominant type is crevice corrosion, which is a lot more difficult to observe: It usually tends to occur in shielded areas such as crevices, formed under gaskets, washers, fastener heads, insulating material, surface deposits, disbonded coatings, threads and lap joints.

Pipe clamps made of plastic in particular have also been prone to inducing crevice corrosion in the past, because the plastic deforms around the tubing and creates even tighter crevices.

Crevice corrosion is always initiated by changes in the local chemistry within the shielded area, usually associated with a stagnant solution on the micro-environmental level:

Trapped seawater becomes stagnant
Depletion of inhibitor and oxygen
A shift to acid conditions
Build-up of aggressive ion species (such as sodium chloride in seawater)
Accelerated corrosion process

Crevice corrosion can have serious and adverse consequences, eventually leading to perforation of tubing walls and the escape of highly flammable fluids and chemicals.

Corrosion Facts

Corrosion in general is a naturally occurring phenomenon commonly defined as the deterioration of a substance (usually a metal) or its properties because of a reaction with its environment. Like other natural hazards, corrosion can cause not only expensive but also dangerous damage to almost everything from automobiles, home appliances and drinking water systems to pipelines, bridges and public buildings.
Figures provided by the U.S. National Climatic Data Center underline that major weather related disasters the U.S. incurred total losses of averaging USD 17 billion annually (1980 – 2001). According to U.S. corrosion studies, the estimated direct cost of metallic corrosion in general was USD 276 billion on an annual basis in 1998. This represented 3,1% of the U.S. Gross Domestic Product.
Direct corrosion costs associated with the domestic oil and gas production activities in the U.S. were determined to be about USD 1,4 billion annually, with USD 0,6 billion attributed to surface piping and facility costs, USD 0,5 billion to downhole tubing, and USD 0,3 billion to capital expenditures related to corrosion.
The U.S. refineries represent approximately 23% of the world’s petroleum production in 1996 supplying more than 18 million barrels of refined petroleum products per day, with a total corrosion related direct cost of USD 3,7 billion. Maintenance expenses make up USD 1,8 billion of this total, vessel expenses are USD 1,4 billion and fouling costs are approximately USD 0,5 billion annually.
^{Source of Information: Report No. FHWA-RD-01-156, September 2001 ” Corrosion Costs and Preventive Strategies in the United States”; Report by CC Technologies Laboratories, Inc. (today: DNV Columbus) to the Federal Highwa}^{y Administration Office of Infrastructure Research and Development}