Intelligent instrument automation

In recent years, the development of smart field devices has always been a topic of discussion. Most of the discussions focused on the new features of the transmitter, while others complained about how difficult it was to obtain additional information on the control system. The reason may be that the old equipment layer network could not handle such requirements.

The emergence of such problems is closely related to the status of industrial networks in manufacturing factories. Most production plants that have been operating for more than a few years have used a wide variety of automation equipment since their initial construction. And just like the “barrel principle” (how much water a bucket can hold depends on the shortest board), the overall performance of the system will not be better than the performance of its oldest equipment. This situation is common in those field devices that use common analog quantities.

Control system vendors have provided a much more complex variety of functions than simple analog I/O for a considerable period of time. Although many companies still use this old and backward instrument system, the HART-enabled I/O has been available for several years. Most companies that equip HART devices and facilities have used HART5 since the 1990s. The latest situation is that several major system vendors have introduced configurable I/O that can be modified through software or hardware modules.

This configurable I/O provides users with the latest capabilities to interact with smart devices and achieve all the benefits they can provide. Configurable I/O can be fully interactive with those HART6 and HART7 transmitters that are becoming more and more common, and use all the latest diagnostic data and control systems to achieve two-way communication with the device.

Many large companies in the process industry, including many refinery operators, see this as an important technological advance that can completely simplify future projects. Devices with advanced HART functionality can provide sophisticated communication paths, and their implementation costs are lower, fault diagnosis is simpler, and flexibility is much greater.

A huge step forward

Automation is the infrastructure that supports process technology. Therefore, people designing automation systems must meet the needs of chemical engineers and other process process designers. If one of these elements has changed, the automation system must be adapted to the changes, because this change can disrupt everything and make the automation system the most critical path for a project. Not all automation hardware and systems currently on the market can be easily adjusted based on those new changes.

Most automated devices are designed for specific applications and are therefore highly personalized. This makes it expensive, changes the cost, requires a large amount of engineering, and requires a lot of documentation and testing. If you can use more off-the-shelf equipment with fewer communication methods and protocols, it will be of great help.

Many users are very keen on the new configurable I/O systems that are already on the market. They see through such systems that vendors are really listening to their voices and are willing to make greater progress in flexibility. There are two things HART functional meter users repeatedly mentioned and want to get rid of: marshalling cabinets and HART multiplexers. Configurable I/O can get rid of both.

So what exactly is the problem?

To be honest, these advancements are considered excellent. However, there has been a problem with the setting of the device. In the past few years, the number of parameters that a typical smart device needs to set has increased significantly. People who need to set up through the keyboard must face endless questions and answers to deal with such situations. The specific parameters of different devices vary, but it always takes some time to set.

Some users work with suppliers to develop pre-set devices. When the user receives the device, the transmitter already has a range, engineering unit, alarm, and so on, so it can be plug and play. These jobs give you all the information you need when you need to book equipment, that is, early in the process. This also means that setting specifications from the ordering of equipment to installation and commissioning cannot be changed. These qualifications reduce the practicality of this approach.

Some users will ask, "Why can't we let the system do the setup work for us? The control system has all the information it needs to get from known field devices. It knows that the PT215 has a range of 0-30 psi and is at 25 psi. This will trigger an alarm, etc. All this information can be found in the system and is always updated. Why do technicians have to look at this information and manually enter it into the device?"

Timm Madden, a senior instrument and control consultant at ExxonMobil Development Corporation, recently made a report to Yokogawa's user group entitled "It happened like this." He spoke of the company's efforts in refining projects using a variety of methods that do not make automation a critical path. The goal is to make people see no automation. Almost no problem arises where those who do not know where to come from, the automation system has been solved from the bud of the problem.

ExxonMobil is a relatively well-known company in handling automation issues, and it also poses many challenges for suppliers. Some of Madden's reports are about technology, others are about programming, and he also spent a lot of time talking about smart device settings. He introduced a set of systems called "DICED" that ExxonMobil is using.

Mr. Madden also pointed out that Exxon Mobil Corporation wanted to standardize hardware and implement all personalized project requirements through software. Field cabinets equipped with configurable I/O should be stocked, ready-to-deploy, fully tested, ready-to-use devices that can be shipped in a short period of time. All the information is obtained from the control system via the network, so in practice the technician does not need to do anything other than connecting the device cable. All are pre-tested, and the number of required documents is greatly reduced.

He said that installing such intelligent I/O cabinets in the field requires nothing but a fiber optic cable connected to the control center and redundant power supply. For field devices, the old marshalling cabinet needs 15 to 25 terminal blocks from each device to the control system, but now only 5 are required: 2 on the equipment side and 3 on the cabinet side. ExxonMobil does not use a fieldbus network but prefers HART devices. Mr. Madden's argument is that this intelligent I/O cabinet approach makes it no longer important to distinguish whether the technology used in the field is HART or Fieldbus. The system architecture and the functionality available are basically the same.

The gap between reality and vision

The technology necessary to support the "DICED" system does not currently exist. But how far is it from us? ExxonMobil believes that HART6 and HART7 transmitters are now available, and new I/O systems should support it. In preparing this article, the author of this article asked the supplier of the four main production meters and configurable I/Os a question, "How far away are we from achieving it?" No one answered.

It is possible that research in this area has progressed more than we know, or that some suppliers are trying different approaches, but their goals are similar. Let's leave the answer to the time.

Smart device settings

According to Timm Madden, Senior Instrumentation and Control Consultant at ExxonMobil Development Corporation, when using DICED (see the meaning of each letter below) and passing new HART6 or HART7 devices through configurable I/O After connecting with the control system, the following process will be performed:

Detection (D) - When a new HART device is connected to configurable I/O, the I/O channel detects that the current is flowing in a direction that it did not flow to before. That means adding a new device.

The interrogation (I)-I/O channel will require the HART command transfer of the device tag. Devices with HART functionality pass back their tag names. If the newly installed equipment is not a HART-enabled device, such as a shut-off valve, it is obviously not possible to respond to the request. In this case, the DICED process is terminated, but a report is still generated for the user to inform the user that the field wiring has changed, most likely a new DI or DO device has been installed.

Configuration (C) - Once the system has detected and identified a new HART functional device, the system can set its engineering scope, engineering units, and other setup information. Our plan is to purchase field devices that have only been pre-configured with tags, and then configure the field devices accordingly with systems that typically have the latest data.

Enable (E) - We assume that the field devices have been configured by the system and become part of a particular control strategy. It should be noted that our project execution process is based on the assumption that we will perform most of the design, configuration and testing work in a virtual environment, but we may not know which I/O channel each field device is going through. Set up.

Therefore, in this step, the system will know which I/O channel the new device is connected to and establish the logic between the contact control strategy and the field device. Once this is done, the field device and its associated logic are activated.

Assuming that all the above steps are completed successfully, we expect the system to report this success through the event log. The vision we are looking forward to is that we can greatly simplify the on-site debugging process that currently requires paper folders and a large number of field trips.

We also believe that the system can automate the test work currently being performed by an engineer or operator sitting in front of the console and contacting the field team via radio. For example, if the detected device is a control valve, we can send an analog output to the valve and read its position via HART. Therefore we can assume that the valve is working properly, there is no stuck, its failure mode (fail open or closed) is correct, and its position is also within its range of travel.

One of our ideas is that all electronic circuits that need to perform DICED are included in configurable I/O modules. The problem now is to make the software work so that it can take full advantage of this hardware. Please note that DICED does not require that the field device itself be changed.