Temperature controller. Replacing and adjusting the temperature controller on a cargo crane

Greetings! In this article we will change the temperature controller of a cargo crane. It has failed and for this reason the crane hydraulic protection system based on oil temperature does not work.

The temperature controller (PID controller) on the crane, together with the PT100 RTD (Resistance Temperature Detector) sensor, are key elements in protecting the crane hydraulics from oil overheating. 

The sensor is located in the expansion tank through which the hydraulic system oil constantly circulates. When the temperature in the tank changes, the thermal resistance of the sensor changes, and the current and voltage in the sensor circuit changes accordingly.

Circuit diagram of operation of the temperature sensor on the cargo crane

The PT100 RTD (Resistance Temperature Detector) sensor is a widely used temperature sensor that measures temperature based on the resistance change in a platinum element. Here’s a brief overview:

Key Characteristics:

1. Platinum Element: The "PT" in PT100 stands for platinum, which is known for its stable and repeatable resistance-temperature relationship.
2. 100 Ohms at 0°C: The "100" indicates that the sensor has a resistance of 100 ohms at 0°C.
3. Temperature Range: Typically, PT100 sensors are used in a temperature range from -200°C to +850°C.
4. Accuracy: PT100 sensors are highly accurate and offer excellent stability over time. They are available in different accuracy classes, such as Class A, Class B, and 1/3 DIN.

Operating Principle:

• Resistance Change: The resistance of the platinum element increases linearly with temperature. By measuring the resistance, the temperature can be determined.
• Temperature Coefficient: PT100 sensors have a standard temperature coefficient of resistance (α) of approximately 0.00385 ohms/ohm/°C, meaning the resistance changes by about 0.385 ohms per degree Celsius change in temperature.

Advantages:

• High Accuracy and Precision: PT100 sensors provide reliable and repeatable measurements.
• Wide Temperature Range: Suitable for a broad range of applications from very low to very high temperatures.
• Long-Term Stability: Platinum's stability ensures consistent performance over time.

Disadvantages:

• Cost: PT100 sensors can be more expensive than other types of temperature sensors like thermistors or thermocouples.
• Self-Heating: At high current levels, the sensor may self-heat, leading to measurement errors.

PT100 RTD sensors are a popular choice for accurate and reliable temperature measurement in various industrial and scientific applications. Their linear resistance-temperature relationship and long-term stability make them an essential tool in environments where precise temperature control is crucial.

The temperature controller (PID controller) at a temperature in the tank of 80°C and above issues an alarm for high oil temperature and stops the hydraulic system. At a temperature of 55°C and below, the controller stops the cooling fan of the oil cooler; at a temperature of 60°C and above, the cooling fans will operate in automatic mode (on the diagram, the inscription “off 60°C” may be misleading).

High Temperature Instructions

Troubleshooting manual

If any problems arise with the controller, sensor or PLC, then you should contact the troubleshooting manual offered by the manufacturer.

In our case, the problem is with the temperature controller, the display of which has failed and requires replacement.

Replacing the controller

Disconnecting wires

We replace the controller with a new one, and it is very important to mark all the contact wires in advance, and also copy the numbering into your notebook. The controller control circuit must be de-energized in advance. You can use the connection diagram as you wish.

Controller Settings

Controller operating mode settings

Controller PID component settings

Controller Parameter Settings

After replacing the controller, it needs to be configured. We check the settings on all cargo cranes and, using the instructions from the manufacturer, set up the PID controller.

Controller controls

In our case, it is important to select the option "Deviation alarm" - "High & Low alarm" and set the setpoint to 40°C. This setup can be confusing because... we should have 80°C.

40°C value on lower display (12°C low temperature alarm)

Change the value of the high temperature ALH (from the factory it was set to 839)

But everything is explained by the fact that the controller operates in deviation mode. We set High alarm to 40°C, Low alarm to 20°C and the temperature setpoint on the lower display to 40°C. Thus, at a temperature of 40 + 40 there will be an alarm for a high temperature of 80°C, and at a temperature of 40 - 20 = 20°C - for a low temperature. The low temperature alarm here is informational.

Disassembling the old controller

So we installed a new temperature controller on a cargo crane, configured it and tested it in operation. In this article I wanted to focus on the fact that it is not enough to simply change controllers and set operating settings; you need to check all the settings inside the PID controller and see in what mode it operates.

Crane model: DMC DDKC-3026-00 (Dongnam Marine Crane)

Temperature controller model: Digital temperature controller DX3 (Hanyoungnux)

Also read other articles about DMC cargo cranes:

1. Problems with cargo cranes. Some problems with cargo cranes that occur on the ship
2. The cargo crane does not slew. Troubleshooting
3. The crane hook goes up slowly. The cargo crane is not working. Troubleshooting
4. PLC failure. The cargo crane does not start. Troubleshooting
5. Motor Fault on the crane. Troubleshooting
6. The crane jib is luffing down under its own weight. Troubleshooting