A customised development of the PPDS Web Browser Application

Background

Pall Corporation is the largest and most diverse filtration, separations and purifications company in the world. They supply filtration, separations, and purifications technologies that are essential to industry. Liaising through Pall Europe, based in Portsmouth, UK, they have been customers of NEL over a decade and in that time had been using the DOS version of NEL’S PPDS software.

Recently the company were considering ways in which NEL could help them move forward and update their working practise. Pall were comfortable using the DOS version, and had developed streamlined procedures that fit around it use. The benefits of the latest version of PPDS for Windows were presented to the company. These included functionality such as the network support of having all clients talking to a central Thermoserver, the Excel interface for custom development and the convenience of the graphical nature of the windows product.

Specifically, Pall wanted a solution that would be network based. It would have to be easy for an occasional user to use. This would take away the burden that the existing ‘Power Users’ were subjected to as being the first port of call for any property calculation. With so many users to support, client installation would have to be easy and flexible enough to handle infrequent use. The ability to perform all calculations that were currently being performed was an essential factor. Ideally the input and output could be saved in accordance with their established operating methods.

There were a few directions that these requirements could have led. Two of the earlier suggestions were a customised front end and custom excel templates. The most likely suggestion was to develop an intranet application, evolved from the prototype web application at ppds.net.

There are several advantages with an intranet application.

Its centralised location makes deployment quite straightforward. The central webserver hosts the application and ‘serves’ pages to the client, requiring no client side installation. This particularly suits infrequent users as there is no ‘real’ reason why they cannot simply access the site themselves. Additionally, as everything is on a central machine, updates can be performed quickly. At this time Pall already had in place an effective intranet ‘pallnet’ that was used by most staff members. This would mean that almost immediately a well designed application would be available to staff once it was installed.

Additionally, as web pages could be customised precisely as the Pall wanted, they could tightly control the look and feel of the application. Furthermore, the custom nature of the application meant that specific calculations that Pall required could be incorporated as part of the normal development.

A specification was drawn up and once approved, work began in early 2004.

Welcome page from the PPDS Web Application as developed for the Pall Intranet

Development

Due to the length of time involved in developing the specification, the requirements were well established by the time development work began. Pall was quite specific about the type of user the application was targeted at and equally precise about the calculations that would be available to that user.

In developing the intranet application NEL’s Software Products Centre would have to add functionality to the Thermoserver. This new functionality would ease the model choice for the user and also allow some new specific calculations. The look and feel of the application was in many ways determined by Pall’s existing corporate standards for intranet development which were adhered to wherever possible.

In most aspects, the intranet application followed the logic established for the DOS program. The user begins by defining a stream of components, and then, based on the stream just defined, is offered calculation options. Once chosen, any specific options for that calculation are set, and the calculation proceeds. Once the calculation is complete the user is brought directly to the results page. This results page is based directly on the established DOS output, again due to Pall’s familiarity with that layout. From the results page the user can ‘dump’ the results into their save file, go back to change the calculations conditions and repeat the calculation, or go further back and choose a different calculation.

Screenshot from the PPDS Web Application as developed for the Pall Intranet showing a typical calculation definition page.

For any given stream the application only makes available those calculations that are appropriate.

This stream driven approach makes controlling the stream fundamental to the operation of the application. With this in mind, the stream is accessible from all operational pages, except the results page.

Thermoserver code developed for this application includes the route set wizard. This function examines the chosen stream and determines the most appropriate model to use for equilibrium calculations. This allows people without the thermodynamics expertise to be confident that their results have a sound basis.

A new calculation, Saturate with Key Component, was added. This calculation allows the user to determine how much of a particular component within the stream will cause a specific phase to form. This is useful in answering questions such as “how much water do I have to add before a liquid phase forms”.

Other Pall specific code that was implemented includes the “Follow on Flash”. This function allows the user to take the output from one calculation and set it as the input stream for the next one. This is very useful in modelling multi-stage operations such as compressors where the vapour stream would be sent through a series of compressors each reducing the pressure and condensing out a liquid.

Standard calculations such as vapour-liquid, liquid-liquid and three-phase flash calculations are also available, as are dew and bubble point calculations, phase envelope calculations, and binary diagrams.

Phase envelope diagrams and equilibria plots were rendered using a 3rd party graphics engine. Normally this tool would generate live graph objects that can be manipulated by the user once an activeX application has been downloaded and installed. In this case the engine was set to create static images. Although this prevents the user from adjusting the graph it does remove the need to download the object, ensuring that there is minimal client configuration.

Screenshot from the PPDS Web Application as developed for the Pall Intranet showing a typical results page with table and graph.

As the application runs on Pall’s intranet, access control was not originally considered. However, although Pall did not want to restrict access to the application, they did want some mechanism of tracking who was using it. The easiest way of implementing this was to use the web server’s built in authentication system and disable anonymous access.

One of the features of this system is that failed calculations are also recorded and graphed. Pall are then able to use this data to examine where additional training is required.

Where is it now?

The completed application – custom Thermoserver, web pages, graphics engine, and database were dispatched to Pall in mid 2004 and the installation, deployment, and customer acceptance was completed by Autum 2004. NEL Software Products Team followed this up with formal training on both the application's use and with a customised version of the NEL Thermodynamics of Fluid Systems course.

As with any new tool we are in regular contact with Pall Europe to determine any shortcomings or enhancements that they have identified.