ECE™ – corrosion and materials selection software

If the process is dry, then no, it is not normally required to conduct corrosion calculations for dry service, except to demonstrate what corrosion would be expected if the process became wet.

Two options:

1. Most corrosion modelling packages, including ECE, require a minimum flow rate of water to be entered, so the typical approach is to set the liquid water flow rate to the minimum possible value.
2. As a more conservative option, if you're presented with a composition of water in the vapor phase heat and mass balance the data, you can convert that into a condensed liquid and determine the maximum possible liquid water flow rate considering complete condensation of any water. That would be a worst-case scenario. If you compare that to the minimum flow rate, that will give you an indication of the spectrum.

Yes, that is exactly the correct approach.

In the event that H2S is present, ECE gives the user a series of outputs:

• General corrosion rate that would be expected on the assumption of FeS film formation considering the relative ratios of CO2 and H2S present.
• Pitting corrosion rate which would occur in the event that the FeS film breaks down locally.
• Pitting risk factor as Low/Moderate/High/Very High which is a qualitative estimation of the stability of the FeS film under the operating conditions and hence a risk factor that pitting may occur.

You need to convert this % to a volumetric flow rate of water in a liquid state. There is usually sufficient detail in the H&MB dataset to do this calculation.

This is just the volumetric % of water in oil. It is calculated by ECE by entering the respective oil and water flowrates.

Yes, unless there is condensate expected. The entry is for liquid hydrocarbon in ECE, which may be crude oil or condensate.

Yes, ECE models the formation of FeS films and also the stability of that film under the conditions entered. It provides the user with a general corrosion rate prediction, a pitting corrosion rate prediction that would occur following FeS film breakdown and also a qualitative stability ranking of the film.

You might find that the corrosion rate reduces with more H2S; it is generally CO2 content that drives the predicted corrosion rate. If the process is dry, then general or pitting corrosion is not a concern. While it may require sour service spec to resist cracking in the event of off-spec wet operation, the difference between 850ppm and 3000ppm would only be important if this is for a CRA selection, for carbon steel selection as long as H2S content is greater than 0.05psi, meaning it is classified as NACE sour service, then an increase H2S makes no difference.

ECE applies an iron carbonate protective scaling factor to the underlying predicted corrosion rate in regions where iron carbonate is expected to form.

There is only a small effect on the flow model and currently this is not a user definable input to ECE. However current developments on the flow model will allow entry of surface roughness values to future versions of ECE.

You can just synchronize them to be the same, and ECE will do that for you, or you can use the bulk upload spreadsheet, which is just a point calculation tool.

The primary difference is that those free spreadsheets do not take account of H2S present.

NORSOK has some very small PPM values of where H2S is acceptable, whereas ECE is a model that fully evaluates the presence of both CO2 and H2O on your conditions.

ECE wouldn’t be applicable to predicting corrosion rates for instrumentation tubing, as the minimum diameter which may be considered is about 3”. Additionally, the NACE CRA selections rules incorporated into ECE are for “any equipment,” they are not applicable to instrumentation tubing, which has separate rulesets in the standard.

Checking low spot water drop out switches off the oil wetting model within ECE, and any protective effect by the presence of oil is removed.

Liquid hold up change is related to the difference in the flow velocity between liquids and gases in a pipeline with the gas flowing faster. It may overtake the water, and the cross-sectional area of water in a pipe increases as it is “held up.” This change parameter enables that to be adjusted over the length of the pipeline being modelled.

Yes, correlation studies have been performed and published. These are available upon request.

This is a possible upgrade in a future version of ECE.

Yes, slug flow is a potential flow pattern that may be predicted by the ECE flow model. The primary impact would be the change in the flow velocity in the event of slug flow as this is an input to the corrosion rate prediction model.

In a word, no, although the flowline model allows for a pipeline section to be elevated, corrosion modelling isn’t sufficiently advanced to model corrosion within piping bends to that detail.

However, with regards to erosion, we do include it within the tubing model an implementation of the DNV RP-0501 erosion standard to evaluate potential solids erosion rates in the event of downhole sand production.

Corrosion inhibition of gas systems must be used with care. The design of the system needs to consider a good distribution of the inhibitor over the internal surface, which is more difficult in the absence of liquids flow.

Multiple injections points and the use of atomising quills and oil-soluble chemicals, which may be transported in any liquid condensate, are typical practices employed in gas systems.

Efficiency of over 99% can be measured in lab tests, however, the value is specific to the chemical and the environment, and only laboratory testing can determine what it is.

The difference between SS316L and SS316L clad is that the clad option is an internal cladding of a carbon steel pipe, and hence the external surface would be carbon steel. A solid SS316L pipe would have an external SS316L surface, and hence different external damage mechanisms would be applicable. However, for the internal environment, they are the same.

Yes, the ECE rules for 13Cr, Duplexes and SS316 are applied to resistance to general and localised corrosion mechanisms in sweet service. Although the conditions have to be quite extreme to get anything but a green light for SS316 and Duplex materials in sweet service.

For the other alloys 6Mo , 825 and 625 the rules are for resistance to sour cracking.

The reference details and domain maps for ECE rules can be found in the help guide.

The lifecycle cost calculator allows these values of wall thickness to be entered by the user. ECE does not calculate mechanical thickness requirements.