Hollysys DCS - DCS daily maintenance and fault analysis and troubleshooting methods

01. Power supply

The DCS power supply system is mostly a "dual backup hot redundant power supply", and the prevention and control of power failures is mainly reflected in the inspection and daily maintenance.

Generally speaking, as long as the unit is operating normally, the failure rate of the DCS system is low, and the faults are mostly "single power loss", as long as the fault is eliminated as soon as possible, the DCS system can be restored to operation.

Maintenance Method:

(1) Use infrared temperature measurement inspection equipment to check the temperature of power cable wiring, wiring, terminal strip and screws, and check the temperature of ultra-high temperature;

(2) Check whether the screws at the wiring, terminal strip and cable wiring are loose or over-temperature, and check whether the fuse capacity is consistent with the circuit diagram;

(3) Check whether the UPS power output is stable, and check whether there is a problem with the UPS power supply wiring;

(4) After the DCS power supply alarm appears, immediately find the cause of the problem, eliminate the fault, and avoid the long-term operation of the single power supply;

(5) If the fault involves the controller, if the power supply equipment cannot be quickly replaced, corresponding precautions should be taken to avoid abnormal initialization of the controller.

▶ Failure Analysis:

The power supply is an important part of maintaining the normal operation of the DCS system, and the cause of the problem needs to be found as soon as possible, and the causes of the fault are mainly as follows:

(1) Poor contact of cables, wiring, and terminal joints;

(2) The connector is loose during the operation of the power supply;

(3) Poor contact at the bolted joints due to external forces;

(4) The quality of the insulation layer is not up to standard or the impedance of the power line increases;

(5) Poor contact caused by corrosion of foreign objects;

(6) The wiring method of the power cord is unreasonable;

(7) The ground wire is unreasonably arranged, and there is a magnetic signal that interferes with the operation of the power supply system.

▶ Troubleshooting:

Power failure is a more common type of fault, with the extension of the use time of the DCS power module, the power failure rate will gradually increase, and the fault handling measures are mainly as follows:

(1) Select high-quality power modules and adjust the power redundancy rate appropriately;

(2) Deal with problems such as loose power wiring during maintenance;

(3) Optimize power wiring to solve the problem of electromagnetic interference;

(4) Establish a power supply maintenance file, and replace the power supply regularly according to its use time.

02. Network communication

There are multiple nodes in the DCS system network, on the one hand, there are human-machine interface connection nodes, such as engineer station nodes and operator station nodes; On the other hand are the nodes that connect to the central processing unit.

Network communication failures are mainly manifested as: server crash, operator station disconnection or crash, decentralized processing unit crash, redundant controller control invalid, communication interruption, etc.

▶ Failure Analysis:

In addition to unreasonable software design and network congestion, network communication failures are mainly caused by the following reasons:

(1) In the process of transmitting data, a node asks for data, but the rest of the nodes lack relevant data, and the query instruction will be issued repeatedly, resulting in network congestion;

(2) Damage to the network communication medium;

(3) The DCS configuration operation is not standardized, and the I/O connection is not reasonably realized, and the network is blocked due to overload in the process of reading data;

(4) After the software is upgraded, the driver and hardware do not match;

(5) Historical data memory occupies too much, and during the peak period of data transmission, there will be frequent network congestion, resulting in crashes and other problems at each site;

(6) The operating environment temperature of DCS hardware is too high (often caused by the failure of the cooling system).

▶ Troubleshooting:

At present, there is no low-cost and effective method to reduce the network communication load, solve the problem of network congestion, and it is still difficult to solve the problem through daily maintenance and maintenance, so the main treatment method is embodied in improving the level of daily maintenance, and the daily maintenance method is:

(1) Frequently conduct network tests, increase the frequency of network tests, confirm the abnormal working conditions of the unit according to the communication load rate with all systems, strengthen network monitoring, adjust data transmission time, and reduce network load in the process of redundant switching;

(2) In the process of overhaul, reset the DPU and data station, delete the invalid I/O, and remove the influencing factors;

(3) The double-layer network structure component DCS system is adopted to separate the system network and the management network to improve the stability of network operation;

(4) Regularly test the hardware working environment, check whether the heat dissipation system is operating normally, and check whether each interface is normal;

(5) The direct data transmission of each system adopts a one-way transmission protocol;

(6) CRT is added to the temperature signal detection to realize abnormal alarm and avoid abnormal temperature affecting the operation of the system;

(7) Before upgrading the driver and software, carefully consider the matching degree of software, driver and hardware to ensure the normal operation of the unit and system.

03. Software

Software failures are usually caused by software programming errors, generally appear after the DCS system is put into operation or after the software is upgraded, most of the software programs are complex, and there are configuration personnel cross-work, etc., resulting in software errors from time to time, and the software used in the DCS system is mainly for the installation of workstation tools and monitoring software.

▶ Failure Analysis:

Software failures are mainly reflected in the following aspects:

(1) The configuration information of the master CPU and the slave CPU is inconsistent, and the CPU cannot be initialized normally.

(2) The database configuration and channel connection signals cannot be effectively matched.

(3) System chaos caused by network communication congestion.

(4) The printer print fails.

(5) After replacing the component once, the variable parameter setting is incorrect.

(5) The equipment is not working normally, and the system output cannot drive the equipment to work normally.

▶ Troubleshooting:

Under normal working conditions, there are few cases of software failures, which mainly appear after modifying the unit configuration and in the process of unit commissioning, and the application of mature software is the basis for ensuring the normal operation of the DCS system.

In this regard, before the unit is overhauled and transformed or the unit is commissioned, it is necessary to implement a perfect transformation plan, and carry out effective technical disclosure according to the content of the plan to ensure the effective implementation of the relevant system and avoid software failure caused by human error. In addition, reasonable backup methods should be used to avoid data loss caused by software failures.

Hollysys DCS - DCS daily maintenance and fault analysis and troubleshooting methods

Hollysys DCS - DCS daily maintenance and fault analysis and troubleshooting methods

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