Pipe classes are the default organization or collection of components used for designing and building pipe lines. This purpose of such a collection is to have a selection of piping components that match a serie of requirements and design conditions.

We have done the engineering of many pipe classes for the process, power and food industry. The services included the preparation of the full package for Authority approval. The pipe class have been new pipe classes but also the check and updating of the existing pipe classes. This experience gives us an good overview of the requirements to make high quality pipe classes.

Pipe classes can have different sources of origin. For example the process licensor has defined the basic 'lay-out' of the pipe class, defining the material, component types and size ranges.

In this particular case the licensor provided the basic requirements for the pipe class. The pipe class included the material of construction the pressure/temperature range and the size range. The pipe classes have been further detailed regarding the welding grouping, material certificates, schedules of the pipe and fittings, commodity codes per customer requirements and the full approval cycle with the Notified Body for authority approval. (Borealis)

Pipe classes can be designed as per calculation codes. The different calculation codes do not give the same result. The PCC software created by and used at Red-Bag allows the switch between calculation codes without any change to the pipe class input. The possibility to switch between the calculations codes such as the ASME B31.3 and EN 13480-3 gives the engineering a better understanding of the critical pipe class components.

In this case the fittings have been corroded and an assessment was requested whether the fittings were fit for service. The ASME B31.X series do not give enough details to calculated the remaining strength of the fittings. For this European customer it was possible to switch the EN 13480-3 and create the detail calculations based on the measure thicknesses. (Internal)

The available dimensional standards, such as the ASME  B36.10 for pipe and B16.9 for fittings, do not always provide the pipe or fitting suitable for the design requirements. For example the pressure can be too high for the strongest component in the standards. In that case a custom build component will be the solution. 

The Tee in this case was a custom build component, large diameter and large wall thickness. Red-Bag provided the detail calculation as per the code requirements. (Fluor)

At a certain point, the existing pipe classes in older plants require a total review of the pipe classes. During the review the old and sometimes superseded standards can be updated and also the selection of the pipe and fitting schedules can be checked according the latest revision of the calculation codes and design standards.

This unit in an existing oil and gas plant has more than 30 pipe classes. The pipe class needed to be recalculated according the latest issue of the calculation code. The calculations together with the required PMA's have been submitted and approved by the Notified Body. A PMA is a Particular Material Appraisal required for the use of ASTM materials in the European market. (Ineos)

The software developed at Red-Bag allows to modify it to certain needs. The individual calculations are available and these can be used for repeated work.

The combination of engineering experience and the software development capabilities is unique. The first use case was the creation of the PCC software for the calculation of all pipe class components with the 'push of one button'. The other possibilities include the repeated calculation of piping components or any other engineering calculation were a limited amount of input parameters change. For example calculating one elbow, with fixed dimensions and material, for many design conditions. Refer to the below cases for more examples.

A minimum thickness table for is an efficient tool to determine whether further inspection of pipe branches is required. Many calculations are required to make these tables for the different pipe sizes, thicknesses and branch pipe size combinations.

Together with the customer the governing design conditions were defined and the pipe material. Red-Bag software engineers developed additional methods to the software to generate the calculations and the report. The report was exported to spreadsheet format.

The software development and the creation of the reports was done within a few weeks. With regular tools this would have taken months up to half a year to create the reports with over 8000 calculations. (Vopak)

A minimum pipe thickness table for is an efficient tool to determine whether further inspection of straight pipe is required. Many calculations are required to make these tables for the different pipe sizes and thicknesses.

Together with the customer the governing design conditions were defined and the pipe material. Red-Bag software engineers developed additional methods to the software to generate the calculations and the report. The report was exported to spreadsheet format.

The software development and the creation of the reports was done within a few weeks. With regular tools this would have taken months to create the reports with over hundreds of calculations. (Vopak)

The piping Tee is a complex formed piping component. The end-customer is concerned about the strength of the supplied Tees for the project. It was decided to calculate each and every Tee according the European EN13480-3 with the interpretation following the AD2000 (Germany) and the RToD (Netherlands). This calculation is included in the Red-Bag PCC software.

Additional functionality was developed in the software to call the individual calculation from a table with the dimensions of the measured Tees. A template spreadsheet developed by Red-Bag was used by the supplier to enter the measured wall thicknesses and dimensions. The spreadsheet was imported in the software and the calculations could be generated efficiently. With the is approach more than 200 Tees have been calculated. (Fluor)

A flange pair, with the bolts/nuts, washer, gasket and flanges is a complex mechanical assembly. Existing calculations are mostly based on the Taylor Forge method looking at the allowable stress in the flange and bolts. Only a limited (static) parameters are used to take for example the gasket behavior into account.

A more advanced calculation method is the EN 1591-1. This calculation code is more detailed and considers the behavior of all components. For example the gasket thickness reduces due to the gasket stress imposed by the flanges, the elasticity of the gasket changes with the temperature and others.

The calculation will also give some indication of the expected leak tightness of the flange assembly in addition of the allowable stress check on the components. The method can be used for regular piping flanges but also custom design body flanges for equipment. Red-Bag is member of the EN committee dealing with the EN 1591-1 calculation code.

Red-Bag has calculated many pipe class flanges. The pipe class consists of various piping components, ranging from pipe, all sorts of fittings up to flanges. The flanges are usually the limiting factor, since the flange rating is used as the design condition for the pipe class. The strength limitation of the flange is therefor covered, however the leak tightness of the flange assembly (flanges, bolts, gasket) is not further determined. The bolt load will to a large extend determine the overall quality of the flange assembly. Red-Bag does the flange calculations for example according the EN 1591-1 to obtain the required bolt load for the design conditions and the required leak tightness. The bolt load table and assembly requiremnts are added to the pipe class and is therefor consistent with the quatlity requirements for the welding work. (work done for Borealis and Vopak)

Flanges in and on equipment are calculated according the various calculation codes. The calculation codes such as the ASME VIII div.1, the EN 13445-3 or the EN 1591-1 have a different approach and different assessment criteria. For critical equipment and equipment flanges Red-Bag can execute all these calculations and compare the different results. Based on the strength assessment and the leak tightness assumptions has provided valuable information and suggestions to mitigate troubeled flanges. Manholes on storage tanks have usually a large diameter and a thin flange and cover. The internal pressure is relatively low and the temperatures are ambient. But after years of operation it occurred that the manhole flanges started to show problems. The general assumptions was that the bolt load should be increased but this did not solve the problem. The problem remained and additional problem was that the bolts and manhole were overloaded. Engineering services were provide by Red-Bag resulting in new bolt load and design parameters. (Vopak)

Shell and tube heat exchangers are complex equipment. The tubesheet is facing on both sides different design conditions and also during start-up different conditions occur. The mechnical model and calculation codes require the engineer to assess the various conditions. Designing a heat exchanger requires experience of the do's and dont's. High pressure differences and high temperture differences at both sides of the tubesheet make heat exchanger design a challenging task. Red-Bag has provided the engineering service to calculate the already designed cover flange and the combination with the gasket at high pressure. Small modifications have been implemented for a successful pressure test. (Exotech)

A shell and tube exchanger is operating with an inlet temperature of almost 900 degree Celsius with a short time from a cold start. The gasket around the tubesheet started leaking after a few of these starts. Red-Bag has executed the analysis of the problem in cooperation with partner Wentzel Dynamics. A FEA model was made for the mechanics of the tubesheet and the flow was implemented to predict the correct thermal effects. The overall FEA investigation was a multi physics quest. The result was that due to the large temperature difference the thick tubesheet started to change shape. Instead of a flat tubesheet the tubesheet became convex shaped. Due to the rotation at the end of the tubesheet gasket facing changed and would deform the gasket. Suggestion have been made to prevent the enormous temperature shock in the heat exchanger. (Petrogas)