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Choice errors and original maintenance measures and backward maintenance concepts are the main reasons for this inefficient use and maintenance expenditure. In today's emphasis on economic benefits, more and more users are beginning to realize that in the past, the only way to implement equipment maintenance plans based on human intuition and experience is no longer able to meet the production needs of the process industry.
Second, the mode of equipment maintenance Equipment maintenance generally has three modes: post-maintenance, preventive maintenance and predictive maintenance.
Afterwards, some people call it "remedial maintenance," "maintenance after failure," and "operational failure management." As the name suggests, it means that equipment is repaired when it fails. This is a kind of maintenance mode that “does not repair without failureâ€. It is also the simplest and most popular maintenance method currently used by users in China. A plant that is in operation until failure management does not spend any money on maintenance until the machine or system fails. Operation to failure is a reactive management technique that waits for a malfunction of the machine or equipment before taking any maintenance action. To be precise, this is a "no maintenance" management method. It is also the most expensive maintenance management method. Analysis shows that the cost of maintenance in reactive or ex-post maintenance mode is 3 times the cost of the same maintenance performed in planned or preventive maintenance mode. Arranging maintenance schedules allows the factory to minimize maintenance time and associated labor costs. It also provides a way to reduce the negative impact of rapid delivery and production decline.
The main costs associated with this type of maintenance management are:
High spare parts inventory costs;
· High overtime labor costs;
·Long machine downtime;
· Low production capacity.
Preventive Maintenance (Preventive Maintenance) and Predictive Maintenance (Predictive Maintenance) are pre-maintenance.
In general, preventive maintenance can be divided into three types:
• Time-based maintenance plan • Performance-based maintenance plan • Condition-based maintenance plan Time-based maintenance plan: Perform the maintenance of a time-based maintenance plan in a specific cycle, for example, every two months or every six months .
Performance-based maintenance plan: It can be based on counter readings installed at the measuring points of the individual equipment and functional locations. Some devices operate according to many parameters or states. These parameters or status information may be provided by the measuring point. When the counter on the equipment reaches a certain reading, the system performs maintenance, for example, every 100 hours of operation, every 500 casting cycles, and so on.
Condition-based maintenance plan: Some devices will be controlled by real-time status or operating parameters such as temperature. These parameters are real-time readings that need to be monitored in real time.
The common symbol of all these preventive maintenance programs is that they all have planning guidelines. All preventive maintenance management plans assume that the condition of the equipment will deteriorate within the statistical time frame that is normally applicable to that particular type of machine. For example, a certain type of pump device will normally have its worn parts replaced after 12 months of operation. Using preventative maintenance techniques, the pump was stopped and remodeled after 11 months of operation. The problem with this approach is that the operating mode and the variables associated with the system or device directly affect the normal operating life of the machine. For pumps used to deliver water for transporting abrasive muds, the mean time between failures (MTBF) is different (see Figure 1). If the pump may not require maintenance after 11 months, the user's repair labor and materials will be wasted. The second option for preventive maintenance is even more expensive. At the same time, there are also a large number of facts that frequently dismantling and parking maintenance leads to a reduction in output, an increase in maintenance costs, and a significant reduction in the actual service life of the equipment. In fact, experts have pointed out that one of the biggest causes of failures in many industrial equipments is that, without rigorous analysis, operations and maintenance of industrial equipment will be carried out.
Predictive maintenance (PM), also known as predictive maintenance or strategic maintenance. Predictive maintenance integrates equipment condition monitoring, fault diagnosis, fault (state) forecasting, maintenance decision support, and maintenance activities. It is an emerging advanced maintenance method in recent years.
Predictive maintenance is actually a situation-driven preventive maintenance program. Predictive maintenance does not rely on industry or factory average life-span statistics (that is, mean time between failures) to plan maintenance activities, but directly monitors operating conditions, efficiency, heat distribution, and other indicators to determine the actual average Time to failure may jeopardize the loss of efficiency of the operation of all critical system devices in the plant or facility. Compared with preventive maintenance, it has obvious advantages:
· Overcome the blindness of preventive maintenance and have strong pertinence. According to the different conditions, different treatment methods are adopted to reduce the cost of operation and maintenance.
· Reduce downtime (total maintenance) time, improve equipment reliability and availability, extend equipment life, and better implement the "safety first. prevention-oriented" approach.
• Reduce the amount of maintenance work, reduce labor intensity, help reduce staff and increase efficiency, improve economic efficiency.
Second, the status of predictive maintenance In the past few years, with the rapid development of instruments and meters given to microprocessors or computers, as well as the continuous improvement of maintenance management systems, especially advanced communication technologies such as fieldbus and industrial Ethernet. With rapid development and popularity, major domestic and foreign manufacturers have introduced various advanced predictive maintenance technologies. Dr. FitCh of the United States established the concept and theory of initiative maintenance in predictive maintenance.
The implementation of Total Quality Management (TQM) and lSO9000 also doubles the demand for PDM programs. Both the TQM and the lSO9000 have requirements for maintenance planning procedures to ensure that the process and all its components can continue to perform high-performance.
Predictive maintenance has a narrow and broad sense in the concept of connotation and extension.
The narrow sense of predictive maintenance is based on "state monitoring," stressing that "fault diagnosis" refers to the condition monitoring of equipment from time to time or continuously, based on the results. Identify equipment with or without state abnormalities or failure trends, and then arrange maintenance in due course. Generalized predictive maintenance integrates status monitoring, fault diagnosis, status prediction, and maintenance decisions. Condition monitoring and fault diagnosis are the foundation. State prediction is Focused, maintenance decisions lead to final maintenance activity requirements. It is a systematic process. It incorporates maintenance management into the scope of predictive maintenance. Take the entire maintenance process into consideration until you find out about the maintenance activities.
III. Predictive maintenance of Siemens meters In recent years, Siemens has designed and developed a number of highly intelligent instrument products around the concept of predictive maintenance.
1. Sitrans DA400 Pump Diagnostic System As stated in the previous example, for most slurry pumps with high wear and tear resistance, effective low-cost maintenance has always been a challenge. The Sitrans DA400 based on acoustic sensitivity diagnostics and Profibus technology introduced by Siemens can effectively implement a solution for predictive maintenance of pumps.
Pump leakage usually occurs in the turbulent region, especially when cavitation occurs under high pressure conditions. Sound waves or ultrasonic waves are generated at this time. Sensors can be installed outside the valve for detection. Sound level is a measure of leakage.
The on-line diagnostic system SitransDA400 (Figure 2) fully meets these requirements. The acoustic emission sensor is mounted outside the valve and is highly sensitive to leakage signals and insensitive to pump operating signals. Proper handling of the signal allows the measurement to automatically adapt to changes in load conditions, such as pressure or number of strokes. The operator only needs to set the alarm value.
The SITRANSDA400 sound-sensitive detection system provides an excellent solution for the operation of the reciprocating diaphragm coal slurry pump to detect suction and discharge valves.
The SITRANSDA 400 uses sound levels that detect the presence of cavitation and the corresponding operating noise of the pump to diagnose that the opening and closing of the valve is intact. Conversely, if cavitation is present in a defective valve, it can be identified by a periodic increase in sound level; the valve being tested detects this increase in sound level via the SITRANSDA 400; this detection can be done exclusively. Completed within the ultrasound range. This can filter out the noise generated by the operation of the pump and the closing of the valve.
Sitrans DA400's condition-based maintenance requires monitoring the operating conditions of the device or operating unit. The advantages are:
The device was found to be damaged before it failed.
·You can formulate parking maintenance plans,
· Costly damage has been repaired before it appeared
• Extend the service life of components
Automatic inspection of the device or unit Based on the experimental observation for more than half a year on site, the average maintenance time of the diaphragm pumps with Sitrans DA400 installed is reduced by about 2/3 compared to the two unmounted diaphragm pumps, which is equivalent to a reduction of 2/3. The maintenance cost (Figure 3), while greatly extending the life of the equipment.
2.Sipart PS2 intelligent valve positioner Because the intelligent valve positioner is installed on the pneumatic control valve, its working environment is relatively poor, such as the ambient temperature, pipeline vibration and other factors will have an adverse impact on the normal work of the intelligent valve positioner. In the design process of the intelligent valve positioner, some of its own diagnostic functions are designed taking these adverse factors into consideration. At the same time, pneumatic valves themselves work in harsh environments for a long time and there are also problems such as corrosion and wear. Therefore, if the predictive maintenance of the valve is achieved through the diagnostic function of the intelligent valve positioner, it is also a concern of many users.
Intelligent valve positioner fault diagnosis of the regulating valve is accomplished through an additional sensor. The micro-positioner inside the locator collects data of various sensors at regular intervals, performs calculations, comparisons, analysis, and configuration on various data, and outputs abnormal information through the configuration software to output an alarm signal. Intelligent valve positioner diagnosis of valve is divided into online diagnosis, off-line diagnosis.
Online diagnostics include: travel accumulation, number of travel direction changes, number of alarms, dead-zone self-adjustment, valve baseline position (eg, seat wear), hours of operation at the highest and lowest temperatures, number of times the piezoelectric valve has been operated, valve positioning Time, leakage of actuators, noise diagnosis, etc. Off-line diagnostics include: sealability, static characteristics, step transitions, and frequency response characteristics of actuators and gas lines.
In addition, the intelligent electric valve positioner SIPARTPS2 offers more additional monitoring functions. The status display is derived from the monitoring of fault signals. The fault signals are classified by "traffic light" and are indicated by green, $, and red wrenches (PDM software.
·Needs maintenance (green wrench)
Urgent repairs ($ wrench)
Proximity to failure or failure (red wrench)
This allows the user to detect in advance before the valve or actuator can cause a major failure, which can prevent the system from shutting down. Through the indication of fault signals, such as damage to the diaphragm of the actuator, delay in operation, etc., the user can use proper maintenance strategies to ensure the system reliability.
3.Sitrans CLS300 capacitive level switch in industries such as pharmaceuticals, fertilizers, non-ferrous metals, petrochemicals, etc., because many measurement media itself has a strong adhesion, wear and other reasons, thus adding a lot of additional maintenance costs.
Siemens therefore introduced a capacitive level gauge with a Profibus bus to analyze critical data such as the amount of dead probes (variation of the zero point capacitance) of the field probe and the wear of the probe (accumulation capacitance change), and transmitted via the field bus. A large amount of diagnostic information is sent to the upper computer to help the user to specify a predictive maintenance plan (Figure 5), which greatly saves the user's maintenance costs. At the same time, due to the reduced number of replacement parts, it also equates to the extension of the actual service life of the equipment. This function is difficult to achieve for a meter that can only output switching signals.
4, Siwarex weighing system is different from the traditional weighing system, Siwarex weighing system is actually a digital weighing solution fully integrated in Simatic system. Compared to traditional weighing systems, the Siwarex system has broken through the limitations of communication and system architecture and has demonstrated tremendous technical advantages in system measurement accuracy, control speed, construction period, and long-term maintenance.
As the relative structure of the weighing system is relatively complex and maintenance is relatively large, long-term technology-leading weighing technology manufacturers have been considering how to design a system that can not only reduce costs, simplify the weighing system structure, but also improve the overall performance of the weighing system. The solution, Siemens Siem-based weighing solutions, is undoubtedly a viable solution to meet the new requirements.
The new Siwarex system provides a very conceptual and ideal tool for most users. The event recording function is used to record the progress and status of weighing in real time, and to analyze abnormal events. At the same time, the diagnostic buffer will record the last 100 diagnostics. Through long-term continuous monitoring of key parameters of the load cell and cable, we can obtain pre-diagnosis information on the weighing system (see Figure 6) to avoid sudden and expensive equipment stop failures and reduce maintenance Maintenance costs. These functions provided by Siwarex are undoubtedly an ideal complement to the evaluation and diagnosis of process data.
In addition, Siwarex can send the data recorded in the event of a failure, including the scale setting data, to the relevant experts, such as machinery manufacturers, via the Internet in a set manner. It can analyze an issue and provide independent diagnosis from time and place. Experts do not need to rush to the location of the equipment, as long as they can provide faster and more timely help through remote transmission, which saves time and costs.
IV. Concluding remarks Any kind of technology will certainly have its limitations. Selecting and formulating the most appropriate maintenance program must be judged from the on-site working conditions and the actual conditions of the company. With continuous breakthrough in electronic technology, sensor technology and communication technology, we believe that more and more predictive maintenance solutions will be introduced to the market; we also believe that due to the financial crisis, more and more users will start to Consider how to save maintenance costs, not just reduce investment costs. Of course, predictive maintenance itself is a dynamic and sustainable management process. It cannot be achieved by relying on the efforts of several departments or suppliers. It also requires more people's attention and participation to reflect its value.
Any advanced technology cannot be separated from human factors. No matter what kind of maintenance technology can not be separated from human participation, whether it is preventive maintenance, predictive maintenance, or even active maintenance, it needs to be analyzed according to the actual situation. The most appropriate maintenance plan is to achieve the best results. "UseitandForgetit!" or "doing nothing," is the ideal situation we have pursued in our maintenance plan.
2. Material: The poster stand is usually made of high-quality materials such as aluminum or steel to ensure durability and stability.
3. Weight: The weight of a standard poster stand can vary, but it is usually lightweight enough to be easily moved around and transported.
4. Height: The height of a standard poster stand can vary, but it is usually adjustable to accommodate different poster sizes and viewing angles.
5. Base: The base of the poster stand is usually designed to be stable and sturdy to prevent the stand from tipping over.
6. Display: The poster stand typically features a clear acrylic or plastic sleeve to hold the poster in place and protect it from damage.
7. Mobility: Some poster stands may come with wheels or casters to make it easier to move around.
8. Assembly: The poster stand may require some assembly, but it is usually easy to put together and does not require any special tools.
Keywords: Siemens meters, predictive, Preface Today's process industry, on the site of the increasingly higher reliability requirements, generally require that the instrument and equipment can meet 7/24 continuous and reliable work, sudden failure will result in downtime Big loss. Therefore, higher requirements are also put on the maintenance of the equipment so as to avoid the loss of production and the waste of materials. According to statistics, in 1981, the United States factory spent more than US$600 billion in the cost of maintaining its key installation systems. In 1991, this cost had risen to more than $800 billion, and in 2000 it was a record-breaking $1.2 trillion. These data indicate that one-third to one-half of these costs are wasted due to the use of ineffective maintenance management methods. Although there is no statistical data on this aspect in China, it is believed that China’s current situation in this respect is similar to that of the United States.
April 08, 2024