Proximity switch. Replacing the revolution sensor on the purifier

Greetings! Today, the revolution sensor on the heavy fuel separator failed. In the instructions, it is called a proximity switch.

This inductive speed sensor (proximity switch) installed in the separator detects the drop in speed on the horizontal shaft and sends an output signal to the multi-monitor equivalent to the amount of sludge discharged. 

Pickup sensors are also used on ships, which differ from proximity switch sensors in some technical features.

Difference between Pickup Sensors and Proximity Switch Sensors

Pickup Sensors

• These are inductive sensors that react to changes in a magnetic field.
• Mainly used for reading the rotational speed of gears, flywheels, crankshafts, etc.
• They work without external power by generating a signal (usually AC voltage) when a metallic object moves nearby.
• Require a minimum movement speed to generate a signal.
• Commonly used in ignition systems, ABS, and rotational speed measurement.

Proximity Switch Sensors

• These are sensors that detect the presence of an object without physical contact.
• Available in different types: inductive (for metals), capacitive (for any material), optical, ultrasonic, etc.
• Require external power and output a discrete signal (ON/OFF).
• Used for automation, position control, conveyors, safety systems, etc.

If you need to measure rotational speed, use a pickup sensor. If you need to detect the presence of an object, use a proximity switch sensor.

Separator multi-monitor

That is, in addition to reading the shaft speed, the system also uses this sensor to understand the amount of sludge when discharging the separator. Without this sensor, the separator will not work normally, so if it fails, it must be replaced.

Multi-monitor

Multi-monitor is a device to which all separator sensors are connected, it participates in the safe and correct operation of the separator.

Before installing a new proximity switch, let's read the instructions for the sensor, as well as how to install it correctly.

Instructions for installing the speed sensor

From the instructions it is clear that the gap between the shaft and the sensor should be about 1 mm, the error can be 0.3 mm. For precise measurements of the sensor seating depth, use a caliper.

Before pulling out the old sensor, we can measure the distance of the outer part that protrudes.

Before carrying out any work on the separator, it is necessary to de-energize it and make sure that it has stopped rotating!

16 mm outer part

Outer part measurement

The photo shows that it is quite difficult to measure the internal depth, so we will use the outer part measurement.

New and old sensors

Measurement of the outer part showed that the sensor protrudes from the surface of its mount by 16 mm. Therefore, we pull out the old sensor, having previously loosened the inner nut, and install (screw in) the new sensor.

The seating depth should be 16 mm according to the external measurement.

Checking the gap

After installing the sensor, we fix it with a clamping nut, it is enough to tighten it by hand. It is very important to make sure that the nut is well fixed and that there is the correct gap between the sensor and the shaft.

Installing a new proximity switch sensor

The new proximity switch sensor has been installed and tested in operation. The vessel has many similar systems that use speed and position sensors, for example, in the counters and tachometers of the main, auxiliary engines and turbines. Proximity switches are used in synchronous communication systems, for example, to determine the position of the engine telegraph.

A proximity switch is a device that detects the presence or absence of an object near its sensing element without physical contact with the object. These sensors are widely used in automation, robotics, and various control systems to detect the position, movement, or presence of objects. The operating principle and design may vary depending on the type of sensor.

Here are the main types of proximity sensors:

1. Inductive sensors: Used to detect metallic objects. Works on the basis of a change in inductance when a metallic object approaches.
2. Capacitive sensors: Can detect both metallic and non-metallic objects. Works on the basis of a change in capacitance when an object approaches.
3. Ultrasonic sensors: Use ultrasonic waves to detect objects. Emits high-frequency sound waves and measures the time it takes for them to reflect off the object.
4. Optical sensors: Use light (usually infrared) to detect objects. Includes photoelectric sensors, which can work on the principle of interrupting or reflecting a beam.
5. Magnetic sensors: Detect the presence of a magnetic field and are used to detect magnetic objects.

The main advantages of proximity sensors include:

• No mechanical wear as they do not require physical contact with the object.
• High response speed and accuracy.
• Reliability and durability in various operating conditions.

Applications of proximity sensors include automatic doors, conveyor systems, security systems, industrial robots and other automated systems.

Proximity switch sensors can also be installed instead of limit switches on cranes, in watertight door alarm systems, and in various cargo systems where it is necessary to record the position of individual objects. The main function they perform is to protect the mechanism and the operator.