Rachael Mell
OTM Consulting
The importance of developing a standard topsides interface, including a standard communication protocol, remains paramount for both cost and risk reasons; 2015 might finally be the year that gets us there. In June 2015, the topsides standardization network MDIS (Master Control Station and Distributed Control System Interface Standardization) successfully completed interoperability (IOP) tests in Amsterdam that demonstrated the standard working in practice. Although there is still work to be done, the tests proved one of the key benefits of the standard: switching between different vendor systems should and can take minutes not months.
MDIS was established in 2010 by a group of operators, distributed control system (DSC) vendors, and subsea vendors. The individual parties realized the potential and benefit of working together to tackle the challenges associated with disparate communications interfaces. The mission established from the outset was to optimize master control station (MCS) to DCS communications of topsides systems, by defining and establishing a standard for the interface. As subsea developments have become increasingly complex and costly, realizing this objective would provide significant value to operators and the industry at large. At a high level it would simplify implementation of data communication links and increase data quality but at a more project management level system interface testing requirements would be simplified, development times and risk of interface failures would be minimized, and project changes could happen much faster.
With these benefits in mind, the MDIS Network members have been working closely to develop an appropriate solution. As one of the network’s operator members commented: “The MDIS standard addresses project concerns related to interface issues and the unforeseen needs for additional testing. The new standard should work towards minimizing this risk.”
Thus far the network has defined two architectures, interfaced and integrated, that will be supported by the standard. In addition, the OPC Unified Architecture (UA) protocol was selected, which marked an important step forward. OPC UA is an interoperability framework for the secure and reliable exchange of data and allows the creation of standard, defined common subsea working objects. This approach was chosen from an initial list of eight protocols from which four were shortlisted and subjected to extensive testing throughout 2012. Since then, MDIS has been working extensively with the OPC Foundation to understand the protocol and develop the MDIS information model. The model currently includes four MDIS objects – valve, choke, analogue instrument, and digital instrument – which standardize the information that is expected to flow between the MCS and the DCS for all operations. Work is now well under way toward completing the MDIS information model and MDIS certification.
Thomas Burke, OPC Foundation president and executive director, said that the value proposition for OPC UA was “all about connectivity and providing the complete infrastructure to support platform independent interoperability and information modeling.” He added that “the important work that is being done by MDIS, in defining a standardized information model for all of their objects, fits well with the OPC UA information modeling capabilities. It allows OPC UA clients and servers to communicate integrated information seamlessly. The organizations working on MDIS have recognized the importance of secure reliable interoperability and platform independence as a base requirement for their information modeling. I’m excited that they have chosen OPC UA as the protocol of choice to deliver the solution to their requirements.”
The MDIS Validation Test workgroup has defined extensive test cases that ensure the correct implementation of the MDIS objects within vendors’ products. Eventually a series of tests will be defined that the vendor must pass in order to achieve MDIS certification.
Perhaps most notable in the progress of the topsides standard is the first MDIS interoperability (IOP) test that was conducted in June 2015. The purpose of the IOP test was to ensure the object models were correctly defined and to understand how the object definitions are being interpreted by different vendors. The testing involved six servers and six clients establishing communication and completing a series of test cases designed to test the functionality of the object models. The testing involved a dedicated test between each client and server pair. All pairs were able to communicate successfully and work through the test cases.
One of the major successes during the IOP test was that switching between vendor pairs and establishing communication took a matter of minutes, something that would currently take months of development time on a project.
Additional successes and lessons learned from the testing have led to minor changes to the object models and several items that will go into the MDIS recommended practice, a vital part of the MDIS standard. The success of this initial interoperability test means that work can now move forward with defining a recommended practice and additional object models.
As the information model and recommended practice becomes more defined, so development and testing activity will become more intense; the recent IOP test was an important first step in moving the work of MDIS from paper-based to product-based. Planning is already under way for the next IOP test to take place in early 2016.
Following the success of these IOP tests, and with growing support from the businesses that are providing resources and commitment, MDIS members will be in a strong position to mature the common standard going forward. Nobuaki Konishi, vice president of Process Automation Systems Business Center at DCS vendor Yokogawa, says “We are grateful for the opportunity to work with operating companies and subsea vendors to develop the MDIS specifications. By working together we have developed an in-depth understanding of the requirements and are committed to providing MDIS interfaces that will provide value to the operating companies.” This type of commitment ensures MDIS can deliver against the need for a standardized approach in the industry that provides simplified data communication links with increased data quality.
The MDIS standard offers significant promise for topsides communications; by using common interfaces operators will be able to evolve their systems and adapt to project and program changes with greater efficiency and effectiveness. In a time when cost control is under tight scrutiny across the industry and investment decisions are more difficult than ever it is good to see that collaboration and cooperation initiatives do work. The progress that MDIS has made to date is notable and the next set of IOP test results should be watched and taken note of as well. •
