Troubleshooting and Calibration of ABB Millmate Tension Gauge

Troubleshooting and Calibration of ABB Millmate Tension Gauge

In modern continuous production lines such as cold rolling, annealing, pickling, and galvanizing, strip tension is the core parameter that determines the shape, thickness accuracy, and operational stability of the finished product. The ABB Millmate strip tension gauge system (including MC 400 controller, Millmate Operator Unit 400 control panel, and various load sensors) has a high installed capacity in the metallurgical industry due to its excellent resistance to harsh environments and extremely high measurement accuracy. However, high temperatures, steam, oil stains, and high-frequency vibrations on site often cause tension measurements to drift, jump, or communication interruptions. For on-site maintenance engineers, a thorough understanding of their core Presductor is essential ®  The principle of magnetoelastic measurement and mastering the fast isolation and troubleshooting method of signal links and system components are key to ensuring the continuous operation of the production line.

Core Measurement Principles and Hardware Architecture Analysis

The core advantage of the Millmate system comes from its unique sensor technology. Presductor patented in 1954 ®  Principle, based on the magneto elastic effect: When mechanical force is applied to the sensor steel body, its magnetic conductivity will change. The primary coil inside the sensor is fed with alternating current, and the secondary coil serves as the measuring winding. The two are arranged orthogonally at a 90 degree angle and have no magnetic coupling when there is no load. When the steel body is loaded (such as the vertical or horizontal force generated by the turning roller installed on the load sensor), the symmetry of the magnetic field is broken, and the secondary coil induces a voltage signal proportional to the load.

1. Selection and characteristics of load sensors

When replacing or troubleshooting sensors, on-site engineers must first confirm the installation direction:

Vertical measurement: including PFBL 141 series (customized, range 4-400 kN) and PFCL 201 series (PillowBlock, range 5-50 kN). Vertical measurement sensors are sensitive to vertical forces and insensitive to horizontal forces, and are typically used between the stands of continuous rolling mills or compact rolling mills.

Horizontal measurement: including PFTL 201 series (range 10-100 kN) and PFTL 101 series (range 0.5-20 kN). The horizontal measurement scheme can eliminate the interference of the self weight of the rolling mill (Tare) by measuring the horizontal force component, thereby obtaining extremely high measurement accuracy. It is mainly used in acid pickling, annealing, galvanizing and other process lines.

This series of sensors adopts a solid stainless steel design with no physical moving parts inside, which gives it extremely high spring constant and vibration resistance. Some models can withstand overloads up to 30 times the rated load without damaging the data.

2. Control and Network Architecture

The brain of the system is Millmate Controller 400 (MC 400). It is responsible for powering sensors, processing weak signals, and converting them into standard industrial signals. The MC 400 supports RS-232, RS-485, and optional fieldbus communication. The operator performs intuitive operations through the Millmate Operator Unit 400 panel, which is connected to the controller via a local area network (LAN) based on the IEEE 802.3 standard and TCP/IP protocol, powered by 24V DC. In the signal transmission link, if the load sensor is far away from the control cabinet, a PFBC 161 junction box is usually installed to extend the distance and reduce wiring costs; In situations where enhanced electrical insulation or long-distance transmission is required, a PxUB 201 insulated amplifier (supporting 0- ± 10V and 4-20mA outputs) will be connected in series.

Common on-site troubleshooting and diagnostic strategies

When the tension meter system malfunctions, it usually manifests as tension display fluctuations, constant values, inability to calibrate, or communication interruptions. The investigation should follow the reverse thinking from the physical layer to the signal layer, and then to the control layer.

1. Intense fluctuations or drift in tension display

Mechanical installation stress: Check for foreign objects or uneven stress on the fastening bolts at the bottom of the load sensor. Due to the extremely high spring constant of the sensor, any external mechanical stress will be directly reflected in the signal.

Cable insulation and interference: Check whether the cable from the sensor to the junction box is damaged, and whether the shielding layer is reliably grounded at one end. In the rolling mill area with dense frequency converters, it is necessary to use fixed cables with metal protective hoses as specified by the original factory (such as CE version, with fixed connecting cables) to resist electromagnetic interference (EMI).

Temperature compensation failure: The working temperature range of the sensor is -10 ° C to+90 ° C (some horizontal models can reach 105 ° C). Check if the ambient temperature exceeds the limit. If the zero point drift or sensitivity drift exceeds the rated value (usually 0.005%/K or 0.010%/K), it may be necessary to recalibrate the zero position.

2. Signal link interruption (no response from control panel)

Power supply inspection: First, measure whether the 24V DC power supply of the operation panel is normal. If using PxUB 201 insulated amplifier, it is necessary to check whether its power supply (+24V, 20-253V wide voltage) is normal and whether the output terminal is overloaded.

Network communication failure: If there is no communication between MC 400 and Millmate Operator Unit 400, check the TCP/IP settings of the local area network (LAN). Check if the network cable interface is loose and if the switch is in a crash state.

Relay board abnormality: If the system linkage or interlocking signal is lost, check the PFVK 128 relay board in the slot. This board is equipped with 4 conversion contact relays, with a power consumption of 20mA/relay. Check if the contact capacity (AC 250V/8A, DC 48V/1.2A) is stuck due to overload.

3. Control system configuration error

After replacing the new MC 400 controller or control panel, if the numerical display is chaotic, it is necessary to check the internal parameters. The MC 400 is equipped with rich built-in load cell tables, and engineers need to accurately select the model of the connected sensor (such as PFCL 201C or PFTL 201D) and the corresponding units (N, kN, MN, kp, t, lb, T) through the panel. If two or more rollers are used to measure the structure on site, it is necessary to ensure that the angle parameters (α, β) are inputted correctly, otherwise the system cannot pass the formula

FRot=T(sinα+sinβ)+Tare

F Rot=Calculate the actual tension of the strip steel using T (sin α+sin β)+Tare.

Standardized calibration and long-term maintenance recommendations

1. Zero calibration and tension calibration

When performing zero position calibration, it is necessary to ensure that there is no strip steel on the rolling mill and it is in a stationary state. The self diagnostic test system of MC 400 can assist in confirming the status of sensors. Tension calibration usually requires the use of standard weights or specialized calibration devices to verify the linearity deviation (≤± 0.5%) and repeatability error (≤± 0.05%) of the system by applying known forces.

In addition, the MC 400 provides adjustable filter times ranging from 5ms to 500ms. If the tension display of the rolling mill lags behind during acceleration and deceleration, the filtering time can be appropriately reduced; If the on-site mechanical vibration is extremely large, the filtering time can be increased to smooth the signal.

2. Protection and modular replacement in harsh environments

It is recommended to use fixed cable versions with protective hoses (such as PFCL 201CE or PFTL 101BE) on acid pickling or high-temperature annealing lines to prevent corrosive liquids from entering. For wall mounted installation, MC 400 can be placed in a dust-proof and splash proof cabinet (size 500 × 400 × 200mm) with a protection level of IP65.

When it is confirmed that the sensor is damaged and needs to be replaced, due to the fact that the sensor is made of a whole piece of stainless steel and has a large weight, lifting equipment needs to be used for assistance. Special attention should be paid to protecting the pins of the Cannon connector during disassembly and assembly, and it is strictly prohibited to plug or unplug with power on. After the replacement is completed, the load sensor model must be rechecked on the operation panel and a complete zero and range calibration must be performed before it can be put into production.