Engineering management of the project was awarded to (BESP) Bechtel-Snamprogetti, London in the UK. BESP chose OPC DRIZO Inc., Houston, Texas in the USA to design the glycol contacting and regeneration unit using OPC’s DRIZO patented process.

Specifications for the dehydration of the gas required no more than 1 part per million volume of water @ 70barg. Using OPC’s DRIZO patented technology meant that the unit could be made with lower capital expenditure count than conventional molecular sieves due to their low equipment. Also the DRIZO units produce virtually zero emissions.

What also makes the OPC designed DRIZO units unique is that they can run using diethelyne glycol (readily available in the East) or the more efficient triethelyne glycol (readily available in the West). This means that in the future triethelyne can be used when it becomes more readily available. The DRIZO unit is the only process that can offer this flexibility.

The water-rich glycol that is fed into the regenerator contains a portion of the sour elements that are present in the wet gas. The first stage in extracting these elements is to feed this liquid into a flash drum where the flashed off gas is recompressed and fed back into the plant’s wet gas stream for subsequent dehydration.

The DRIZO process is virtually emission free because there is no flaring off of contaminated gas by-products as with many glycol regeneration processes. The by-products of the DRIZO process are glycol at purity levels of 99.99%+ and sour produced water. This very high level of glycol purity greatly enhances the dehydration efficiency when reintroduced into the wet gas stream.

Requirements were that the unit could be fabricated and shipped from anywhere in the world. With overall dimensions of 13.5m long x 7m wide x 21.2m high, it was evident that the skid could not be fabricated and transported as a single unit.

During the design process steelwork and pipe runs had to be configured to enable the unit to be broken down into boltable sections no larger than 2m x 2m x 10m for transportation by sea, road or rail after fabrication. This approach cut out over 70 tonnes of steel – a significant saving in fabrication and shipping costs.

Early in the design process OPC decided that they needed to design the unit using plant design software that would provide them with powerful 3D modeling tools. After much searching OPC settled on CADWorx/PIPE from COADE, Inc.

CADWorx/PIPE which gave OPC the ability to produce 3D, 2D drawings, fabrication isometrics, bills of material and provided bi-directional links to COADE’s CAESAR II stress analysis package.

OPC found CADWorx/PIPE easy to learn, implement and use. In fact OPC’s designers were up and running after just two days of training. OPC also found great value in the one-year technical support and program updates that COADE included with the purchase of the package.

CADWorx/PIPE’s specification driven routines meant that each fitting was placed to project specifications, which ensured that only components with the correct material and dimensions data were placed in the model. This drastically reduced human error.

The workgroup features of CADWorx/PIPE also made it easy for multiple designers to work on different parts of the model whilst viewing each other’s work at any point in the design. Thus reducing man-hours and increasing output.

Although there were great benefits in working in 3D this would not be much use to those without access to computers or the software. Design reviews and field workers needed 2D drawings and reports that kept to traditional forms of representation.

These ‘deliverables’ included 2D plans, elevations, sections, fabrication isometrics and spool drawings and bills of material. Within CADWorx/PIPE’s single module format OPC were able to create these items automatically from the 3D model with very little effort, modification or clean up.

Another benefit was that any adjustments to the model could be automatically reflected in the 2D drawings. This in it self is not unique but what really set CADWorx/PIPE apart was the ability to pass modifications to the fabrication isometrics or sections back to the model. True ‘round trip’ engineering.

OPC were also looking for other ways to save on the duplication of work and realized that the potential for doing so on the stress analysis portion of the job was enormous.

Typically the designer would draw a stress isometrics from the plant layouts. The stress engineer would then use these to input the information for stress analysis. The drawing would then be marked up and then returned to the designer for review. If all was correct the designer would add the changes to the layout and modify the stress isometrics accordingly.

Because CADWorx/PIPE had the ability to bi-directionally link to COADE’s CAESAR II pipe stress analysis program, OPC saw the chance of saving hundreds of engineering and design hours. An unexpected benefit was that during the preliminary design stages the designer could send the piping layout complete with proposed support points, hangers or restraints to CAESAR II for analysis. Therefore catching potentially large problems early in the design.

Once the analysis had been performed by CAESAR II the stress engineer would make recommendations for layout changes or support placement based on the results. CADWorx/PIPE could read those results directly into 3D model allowing the designer to review the proposed modifications for layout feasibility. Once all parties were satisfied CADWorx/PIPE would import the CAESAR II modified information into the CADWorx/PIPE piping model including any routing or support recommendations.

The bi-directional benefits did not stop there. CADWorx/PIPE is also able to take the analysis results and interactively produce stress isometrics. The designer chooses what analysis information appears on the drawing.

OPC feel that they have not yet fully realized all of the benefits of using CADWorx/PIPE and CAESAR II and feel that there are still greater efficiencies that can be gained through the use of 3D modeling in their design process.

Many of the mundane tasks that designers had come to accept as part of their job are eliminated by the use of this design tool. The results of these mundane tasks were still required, but CADWorx/PIPE made the results an automatic by-product of efficient and safe design.

For OPC using CADWorx/PIPE has meant working smarter, offering clients more and delivering a better quality product for their design dollars.

In the past OPC may just have produced plant layouts and sections leaving the fabrication isometrics and spool drawings as the responsibility of the fabricator. Because OPC can now produce these drawings automatically and using CADWorx/PIPE'x ability to detect clashes they have put themselves in the position of virtually proving the design before the first piece of steel is cut or the first arc is struck with obvious benefits.

OPC believe the decision to implement an integrated engineering CAD system such as CADWorx/PIPE and CAESAR II has been a worthwhile and painless move. OPC DRIZO feels that the project and they have greatly benefited from the use of these design tools.