Author:
Viktor Ilyin,
Chief Engineer M+V Zander Facility Management CIS
Development of optimal functional automation schemes
Functional diagrams of automation are included in the executive documentation of the ACS and are the main document defining the volume and functions of the system. Functional diagrams display the technological object of automation, for example, a ventilation unit, and the corresponding inputs/outputs of the software and hardware of automation. The connections between the technological object and the inputs/outputs form the so-called “data points”, the number of which is one of the determining parameters of the quality and cost indicators of the ACS project.
At first glance, the more “data points”, the higher the volume of automation, quality and efficiency of the project. However, an increase in the number of “data points” leads to an increase in software and hardware, and, accordingly, the cost of equipment and automation tools. Additional controllers are required for input/output of physical signals and additional licenses for software (hereinafter referred to as software). By the way, for many leading manufacturers, the cost of software depends on the number of “data points”.
In recent years, the volume of automated objects based on digital “integration” has increased, in which technological objects are connected to automation equipment via digital data transfer interfaces. For example, the integration of uninterruptible power supplies increases the number of “data points” by an order of magnitude. It is necessary to remember that an increase in the number of “data points” can cause a significant complication of the structural diagram of automation equipment, including the layout of technical equipment and the topology of communication data transfer buses, which can lead to a decrease in the quality and overall reliability of the system.
On the other hand, reducing the number of “data points” can lead to insufficient functionality of the system and, ultimately, to failure to meet the requirements of the technical specifications. Thus, at the design stage, one of the most important stages is the coordination of optimal functional automation schemes that meet the requirements for maintaining a balance in the number of data points. As a rule, technical specifications define the scope of automation only in general terms and cannot solve this problem in full.
Technical risks
At the design stage, there always comes a moment when it is important to assess the technical risks when implementing specific solutions. When implementing large industrial automation projects (APCS), especially in the energy sector, the project includes entire sections on assessing the reliability of the system, including identifying potential risks.
Considering the complexity and importance of modern APCS, the general low quality of the construction process as a whole, it is advisable to use a similar approach in our industry.
Risks can be considered first of all, in relation to the automated control system:
Power outage.
Given the domestic realities, problems with power supply have become a common issue. To reduce such risks, it is recommended to use uninterruptible power supplies for the main technical means of the automated control system (control stations/servers, controllers, up to providing uninterruptible power supply for individual control circuits). It is also recommended to provide uninterruptible power supply for individual key peripheral devices, such as control valves. Many manufacturers of equipment for ensuring the safe position of controls have battery-powered equipment.
Failures in the operation of computers/servers of dispatchers. Upper level of SCADA systems.
Often, key top-level nodes are ordinary computers for home use, not designed for 24-hour operation and full load with multiple peripherals connected and constant read/write operations to the disk. To reduce such risks, it is recommended to use server platforms with integrated data backup, RAID arrays and antivirus tools.
Low outside temperatures.
It can be cold in Russia. Many automation equipment from Western suppliers are simply not designed to operate at such low temperatures. Experience has shown that problems begin at temperatures of -15°C and below. Not only the automation equipment itself, but also process automation objects, such as air heaters, radiators, and pipelines, can be subject to abnormal overcooling. It is necessary to provide for an appropriate selection of automation equipment, such as sensors in a protective design, provide for additional heating, and make maximum use of protective signaling devices with strict adherence to installation and adjustment rules. This is especially true for protective thermostats on air handling unit air heaters.
Low qualifications of service personnel (not a technical risk, but quite common).
Unfortunately, this problem in Russian conditions can be considered a permanent risk for any project. It is recommended not to neglect such measures as:
• conducting serious training and instruction programs for personnel when commissioning systems (including training of dispatch personnel in specialized courses);
• organizing warranty and post-warranty service, concluding service contracts;
• high-quality organization of the access system (delimitation of rights) to various top-level software functions;
• implementation of standard mnemonic diagrams with a proven minimum graphical interface.
Project division scheme, system integration principle.
There are still very few large system integrators of automated control systems on the Russian market that are capable of implementing a full-scale automation project, including:
• design, supply, installation of peripheral devices (sensors, actuators)
• design, supply, installation of automation equipment
• design, supply, installation, connection of electrical distribution devices (panels, cabinets), including power circuits.
As a rule, the Russian integrator of the automated control system performs only the second part, in some cases the first and, very rarely, all three parts in a complex. In some large projects, one should not forget about the complexity of the upper-level IT infrastructure, as this creates additional areas of responsibility for the performers. In conditions where work on one project is divided between several performers, serious difficulties arise in mutual integration, both at the design level and during project implementation, during installation and commissioning.
A typical situation: the ventilation unit was installed by one contractor, the sensor was installed and installed by a second, the controllers were installed and connected by a third, and the power part of the control was implemented by a fourth. It is not difficult to imagine what problems may arise.
It is recommended to use a single integration scheme, in which a separate contractor company is responsible for the entire ASUZ project, performing general management, administration and coordination functions. This significantly increases the efficiency of interaction between the customer and the contractor. It is worth remembering the advantages of the scheme for a general construction general contractor.
Setup of individual subsystems
The customer must pay special attention to quality control of the setup of the following ASUZ subsystems:
Setup of automation of heating points.
The most common scheme for connecting to heat supply in Russia is independent. This scheme is not typical for the West, where schemes with individual heating (boilers) are used. The software and hardware of Western manufacturers practically do not provide basic software algorithms for an independent scheme, so domestic specialists are forced to develop their own approaches. And this gives rise to individual problems with the functions of regulating temperature circuits in combination with the network schedule of the heat supply organization and the internal temperature schedule. Increased attention is required to debugging the regulation scheme in various temperature and time modes.
Adjustment of automation of ventilation units.
It should be noted that there are frequent cases of unsatisfactory adjustment of control circuits for complex central supply and exhaust units using air conditioning circuits of various types of recuperation and humidification.
When setting up, it is necessary to take into account the initial parameters (including I-d diagrams), according to which the ventilation unit was calculated by the design organization. The general process of setting up should include the active participation of companies that performed the installation and setting up of the mechanical part, both hydraulically and air-wise. The task of the automation company is to bring all the parameters together, to set up a working scheme for regulating all temperature-time modes. We must not forget about the separate setting up of fire safety functions when implementing the fire safety system of the building.
Setting up refrigeration and air conditioning systems.
Adjustment of refrigeration and air conditioning systems is the most “sore” topic. On the one hand, central refrigeration systems have only recently begun to be implemented, and, accordingly, approaches to automation have not yet fully developed. On the other hand, as an automation object, a central refrigeration system with various seasonal refrigeration-generating circuits, with a multi-circuit hydraulic circuit, with high requirements for the quality of regulation (narrow temperature range), with high requirements for reliability (air conditioning of server rooms) — also makes high demands on the level of implementation of the automation system. In terms of the volume of commissioning work, the refrigeration and air conditioning system should occupy one of the first places.
Acceptance and delivery activities and seasonal adjustment
One of the main problems for the customer. In the conditions of prompt domestic acceptance of buildings, the ACS, which require the highest quality acceptance events and seasonal debugging with a certain time delay, also fall under the «quick hand». Moreover, unlike other systems, where the customer, with the help of the operating company, is able to independently bring the systems «to mind» later, in the case of the software and hardware component of the ACS, it is extremely difficult and expensive to do without an executor.
An automated control system without adjustment is a perishable semi-finished product. Everything glitters and shines in the wrapper, but inside there is garbage. Therefore, the main advice to the customer: the delivery of a building is one event, and the delivery of an automated control system is quite another. The “automation system operators” should be the last to leave the facility.
Require the automated control system contractor to perform a full range of activities in accordance with GOST 34.601-90, AUTOMATED SYSTEMS. STAGES OF CREATION (which no one has yet canceled). Namely, points:
7.1. Preparation of the automation facility for commissioning the automated control system.
7.2. Personnel training.
7.3. Provision of the AS with the supplied products (software and hardware, software and hardware complexes, information products).
7.4. Construction and installation works.
7.5. Commissioning works.
7.6. Carrying out preliminary tests.
7.7. Carrying out trial operation.
7.8. Carrying out acceptance tests.
It is recommended to close each stage with separate acts and actual reports on the work performed. For example, at the preliminary testing stage, EVERY data point and ALL automation functions should be checked. The report can be prepared based on the automatic protocols of the upper-level system (trends, alarms, mnemonic diagrams with registration of the test date).
Require the transfer of the full set of application software developed for the project (upper-level software: mnemonic diagrams, scripts, additional modules, configurations, databases).
Demand the transfer of a complete set of system software in installation kits (distributions on media), including operating systems and automation software. Agree in advance on the possibility of transferring development software, as this is usually associated with additional costs and licensing terms.
Don't forget to get information about all possible access names and passwords. Today the developer company exists, and tomorrow it may not exist. Your building will stand for many years.
The building's technological systems have a pronounced seasonal nature of operation. In winter, the central heating system operates, and a refrigeration system with «dry coolers» is used. In summer, the heating system is used only for hot water supply, and refrigeration machines are used in refrigeration. Transitional periods have their own characteristics. The operating mode of the central supply and exhaust units also depends significantly on the season.
All this requires additional seasonal commissioning work in the ASUZ. The customer, as a rule, needs to agree on contractual obligations for this work in advance. The system can be commissioned in one season, and problems will appear in two or three months with a change in outside temperature. It is necessary to pay attention to debugging temporary control algorithms, both during working hours and outside working hours (night, weekends, holidays).
The real picture is that after the installation work is completed and the first spot checks of the basic functions at the top level are carried out, the contractor leaves the site and opens the warranty period. All remaining testing and debugging work falls on the shoulders of the customer and the operating company. In fact, the system is fine-tuned during the warranty period.
Warranty and post-warranty operation
Usually, the warranty period for the automated control system (ACS) is offered to be no more than one year. Taking into account Russian and international experience, it is recommended to agree on terms of at least 2 years. This period should include the terms of commissioning and delivery of individual subsystems and the above-mentioned seasonal adjustments. It is necessary to take into account that warranty obligations for the automated control system (ACS) can be included in the general warranty obligations of the general contractor for construction, in which case the terms must be more than one year.
After the system is put into operation, it is necessary to provide the ability for the customer/operating company to independently make changes to the mnemonic diagrams, alarm message lists and trend configurations. At the stage of warranty operation, these actions should not lead to conflict situations regarding the responsibility of the parties; these issues are resolved by prior agreement between the customer and the contractor.
Already at the stage of warranty operation, it is necessary to conclude a service agreement with a specialized company (preferably with the developer company) for technical maintenance. In our experience, ASUZs require minimal but highly qualified periodic maintenance: diagnostics of the main controller tools, testing, debugging of individual algorithms, work on emergency calls.
At the end of the warranty period, it is necessary to make sure that all developed application software for the ASUZ has been transferred to the customer in full. Otherwise, the risks of software loss (in controllers, at stations) may result in restoration work with costs commensurate with the costs of the project.
|
