Boiler does not switch to the second stage. Troubleshooting

Greetings! Here is another article about boiler malfunctions and this time we will analyze an interesting case when the Miura boiler does not switch to the second stage in automatic mode, while there are no visible problems or alarms.

In fact, the problem was that the boiler could not increase pressure and stop, it was working all the time. After that, it was noticed that it did not use the second stage (High Combustion) to supply more fuel to the injector.

Multipole Electric Motors: What They Are and How They Work

What Are Multipole Electric Motors?

Multipole electric motors are a type of electric motor that have multiple magnetic poles in their stator or rotor. Unlike standard two-pole motors, which have one north and one south pole, multipole motors have additional poles—such as four, six, or even more—arranged symmetrically around the motor.

These motors are widely used in industrial applications where high torque and efficient operation at lower speeds are required.

Synchronous Motor Startup Methods

A synchronous motor is an AC electric machine where the rotor rotates at the same speed as the stator’s magnetic field.

Working Principle

• The stator generates a rotating magnetic field when three-phase AC power is applied.
• The rotor produces a constant magnetic field, either through electromagnets or permanent magnets.
• The interaction between the rotor’s and stator’s fields ensures that the rotor spins at the exact synchronous speed.

Start Fail. The fire pump does not start. Troubleshooting

Greetings! Today our fire pump does not start; the “Start Fail” signal is displayed on the motor controller. The Reset button does not reset the error.

We open the starter panel, open the fire pump start-up and operation circuit, and look for the “Start Fail” signal. The motor controller produces this signal in many cases.

The autotransformer was flooded with sea water. Emergency fire pump problem

Today we got low insulation of 440V on the main switchboard megohmmeter when starting the emergency fire pump. Checking the power part of the circuit showed an insulation resistance relative to the electric motor housing of 0 MOhm. Has the motor burned out or is there a chance to restore normal operation of the mechanism?

Checking the power part of the circuit (main contactor and autotransformer) with a portable megohmmeter showed 0 MOhm. Have to climb into the pump shaft and measure the insulation resistance of the electric motor at the terminal box with disconnecting of the power cable.

Freefall lifeboat engine does not start. Part 2. Troubleshooting

Greetings! Today we have another problem with the lifeboat, it won’t start with any battery. At the same time, you can hear the starter motor rotating, but the start does not occur. This is the second article on this topic. In the first article we looked at a case where one battery failed and in that situation the battery tester was very helpful in identifying the problem.

In fact, low starter battery capacity is a fairly common cause of poor starting of lifeboat engines. Usually the solution to the problem ends with this, that is, replacing the batteries. But there are exceptions, especially on older ships.

Motor Fault on the crane. Troubleshooting

Greetings! Today we got a "Motor Fault" error on the cargo crane and the crane doesn't want to start. In the article we will consider the main actions of ETO when searching for and eliminating this malfunction.

Motor Fault on the Crane

The problem is quite large-scale and it can be anything related primarily to electric drives of both the main and auxiliary mechanisms of the crane. There was also a short-term accompanying signal in the ECR on AMS "low insulation 440V", which further narrowed the circle of my search.

Variable Voltage Control. Ward-Leonard control

Where fine control of both hoisting and lowering speed is required either booster control or a modified form of Ward-Leonard control is suitable and footbrakes are not essential. 

A magnetic brake provides against power failure or when returning the controller to off. Generally speaking for straightforward Ward-Leonard schemes the motor for the generator set can be either a.c. or d.c. and as the set runs continuously and in one direction only it is started in the conventional manner. If the supply is a.c. the exciter would be replaced by a static rectifier.

Under these Regulations vessels of 200 gross tons or less must have two lines of hawsers, one at the bow and the other at the stern quarter, each leading through a closed chock. Larger vessels must have at least four lines so arranged that they can be used on either side of the vessel. Two must lead from the bow and two from the stern quarters and not from the extreme bow or stern. For vessels between 200 and 300 gross tons the windlass forward and the capstan aft may be used for the two lines ahead but those leading aft must run from the main drum of power-driven winches and not from capstans. For all larger vessels all four lines must be power-operated and run from the main drum of power-driven winches and not from capstans.

Superconducting DC Motors for Marine Propulsion

Electric propulsion power transmission is usually economical only for special vessels. However, superconducting motors with their greatly reduced weights and sizes indicate that this type of propulsion may become more widespread in the future.

The energy crisis of the early 1970s provided impetus for more sufficient energy conservation and for exploiting hitherto untapped resources.

The superconducting dc motor adds a potent new factor to this situation. It offers the best of these options in that it is lighter than the equivalent conventional ac motor and is a dc motor which may be operated from an ac generator via a simple diode-rectifier-convertor. It offers all the advantages of a dc propulsion system, together with high efficiency, and performance characteristics particularly suited to high efficiency propellers; with no practical power limit.

What are convertors?

Presentation. The convertors in dc drive systems are designed to control and supply separately-excited dc machines in applications that demand rapid response, high accuracy and great reliability.

The convertors are available with single-convertor arrangement and in double-convertor arrangement.

Lloyd's Register of Shipping Certificate for AC Generator or Motor

This is to Certify that the auxiliary propulsion AC generator/stator, particulars of which are given below, has been inspected by me at the Makers' works. The construction, workmanship and materials are good, and the machine complies with the relevant of the Society's Rules.

On completion the generator/motor was tested with satisfactory results.

This certificate is issued upon the terms of the Rules and Regulations of the Society, which provide that:

The Committees of the Society use their best endeavours to ensure that the functions of the Society are properly executed, but it is to be understood that neither the Society nor any Member of any of its Committees nor any of its Officers, Servants or Surveyors is under any circumstances whatever to be held responsible or liable for any inaccuracy in any report or certificate issued by the Society or its Surveyors, or in any entry in the Register Book or other publication of the Society, or for any act or omission, default or negligence of any of its Committees or any Member thereof, or of the Surveyors, or other Officers, Servants or Agents of the Society".

Electric motors with electromagnetically operated brakes

The series motors are designed for operating with electromagnetically operated brakes. In the operating principle these brakes belong to multidisk brakes actuated by short-stroke electromagnets.

Braking results from friction between the rotating disks lined with a friction material and the stationary steel disks. The rotating disks are fitted on bushes keyed to the motor shaft. The stationary disks are fitted on pins secured in the frame.

The electromagnetic system of the brake consists of the two annular cores made of wound steel ribbon, and six coils uniformly spaced around the core circumference. One of the cores is stationary and is welded to the frame. The other core is fitted on the same pins as the stationary disks and is capable of moving in the longitudinal direction. Mounted between the frame and the movable core is the main braking spring.

The spring force is applied through the movable core to the stationary disks and through the friction surfaces to the rotating disks.

The brakes have provisions for manual unbraking, for adjusting the breaking effort through adjustment of the spring force and for adjusting the electromagnet travel to bring it to a normal value as the friction surfaces wear off. In the course of braking the brake absorbs the energy of the rotating masses.

The entire braking energy is distributed between the mechanical brake, the motor and the load.

What is the electronic control of motors?

It is necessary to control motors. That is, motors must be started, stopped, and reversed, and, within limits, it must be possible to control their speed.

The controls needed to perform these various functions on DC motors are designed to alter the quantity or the direction; of the current in the field or in the armature of the motor. On DC controls, these functions were shown to consist mainly of resistances, switches, and solenoids.