Sea trials of the vessel. Mooring tests of ships

And the operational qualities of the ship (vessel). Ship tests are carried out after its construction, modernization, re-equipment and repair: they are mooring, factory running and state (acceptance and delivery for small ships of serial construction, ships and ships that have undergone repair and (or) modernization).

Types of ship tests

State tests of the ship carried out by a state commission with the aim of comprehensively checking the quality of the built ship and the compliance of its tactical and technical elements with the approved project. Acceptance tests are carried out by the acceptance commission.

Factory sea trials of the ship are carried out for the purpose of checking, under sea conditions, the main characteristics of combat and technical equipment and the entire ship as a whole for compliance with the approved tactical and technical elements, ship specifications, diagrams, technical descriptions and operating instructions, forms and technical conditions. Sea trials are one of the important elements that complete the process of building ships and ships, and involve the implementation of a number of repair, restoration and reconstruction work.
During sea trials, under the conditions of a real sea passage, the reliability and vital functions of power plants, navigation equipment and other ship equipment systems, as well as controllability, stability, loss of speed (propulsion) and inertia are tested. In some cases, in order to successfully carry out sea trials, ships and vessels are checked in various climatic and weather conditions. Depending on the purpose of sea trials, their duration can range from several hours to several days. It is also possible to conduct a whole series of sea trials to monitor, check and adjust various elements of ship equipment.

Notes

Literature

Ship testing// Naval Dictionary / Chernavin V. N. - M.: Military Publishing House, 1990. - P. 165-166. - 511 p. -

Constant technical control of products that are intermediate products of hull processing, assembly and welding, mechanical installation and other shops is carried out regularly during the construction of ships.

The scope of inspections during construction is regulated by a list of mandatory acceptances, which is compiled jointly by the Contractor-shipyard and the Customer.

Technical control ends with testing and delivery of the vessel.

The purpose of the tests is to verify compliance of the technical and operational characteristics of the vessel with the characteristics specified in the design documentation.

Before testing the vessel begins, the following work must be completed:

For installation of all pipelines,

Systems of main and auxiliary mechanisms;

Equipment of premises;

Impermeability tests;

Installation of ship equipment and practical items.

All work performed during the construction process, included in the list of mandatory acceptances, is documented with the appropriate documents - certificates signed by the quality control department and representatives of the customer.

To hand over the vessel to the customer, a delivery commission, a test batch and a responsible delivery person are assigned. The commission includes assistants to the responsible commissioner for hull and electrical parts, a commissioning mechanic, foremen and workers from highly qualified specialist installers for main and auxiliary mechanisms, ship devices, systems, and electrical equipment.

The test batch consists of specialists who monitor the operation of individual units during testing.

All deviations from normal operating conditions recorded by the test batch are reported to the responsible commissioner or chief mechanic. At the same time, a test log is maintained in which the test results are recorded.

The scope and sequence of tests are established by a special program, which is the guiding document for testing.

The acceptance of the vessel is carried out by an acceptance committee consisting of representatives of the customer and the Register.

Before the start of testing, the acceptance committee must be presented with a construction contract, a set of drawings of the general layout of the vessel, a book of installation certificates, a log of the weight load of the vessel, a log of alterations and approvals, bench test reports for main and auxiliary mechanisms and other mechanical equipment, as well as instructions, diagrams, descriptions, forms of equipment and passports of control and measuring instruments (instruments). After reviewing all submitted documents, the commission makes a decision on readiness to carry out acceptance tests.

In addition to preparation for testing, the vessel testing period includes the following stages:

Mooring tests;

Sea trials;

Audit;

Control output;

Control tests.

Mooring tests

Mooring tests of ships (SH) are a technological stage of acceptance tests, including Preparation for tests, Mooring tests, Sea trials, Inspection, Control output, Control tests.

ShI is carried out in a sufficient depth of the shipyard water area near the outfitting quay, equipped with coastal mooring devices, without access to the sea.

The purpose of the SHI is to check the quality of ship construction, installation and adjustment of equipment, preliminary testing under load of the main power plant at idle speed, auxiliary mechanisms, systems and devices that ensure the survivability and safety of the ship, preparing the ship for going to sea for sea trials.

By the beginning of the ship construction work must be completed to the extent provided for in the construction certificates.

Checking the main performance indicators of equipment during the period of ShI and sea trials is carried out according to the methods developed by the Designer for lead ships and by the shipyard for serial ships.

The technique involves the use of non-standard instrumentation, as well as devices with established limits of measurement scales and the required accuracy classes to check parameters and create the required operating conditions for the equipment.

SI is carried out separately for mechanical, electrical and housing parts:

Testing of the mechanical part, starting with emergency systems and mechanisms that ensure the safety of the vessel during testing (fire system, flooding and water pumping systems).

Testing of auxiliary energy equipment: turbogenerators and diesel generators, auxiliary boilers, evaporators, desalination plants, etc.

Tests of the main power plant are carried out last. Ship systems, pipelines, electrical networks, power and survivability stations are tested simultaneously with the main mechanisms. Before testing the GTZA of a steam turbine installation, the operation of the shaft turning and shaft braking devices is checked, as well as the movement of the turbines into forward and reverse motion. During mooring tests of a steam turbine installation, hydraulic tests of pipelines of all systems are carried out, including fuel, fire, and steam; check the operation of auxiliary installations (start-up, feed, fuel pumps); carry out pumping of oil through the oil pipeline of the engine room; carry out hydraulic and steam tests of steam pipelines of the engine room; carry out tests of circulation and condensate pumps, as well as pipelines directly connected to turbines; carry out checking the power and lighting networks and starting the turbogenerator, as well as starting the GTZ for idling. Then the operation of the GTZ is checked at a rotation speed that is permissible according to the conditions of mooring reliability, the condition of coastal structures and the depth of the water area.

Simulation tests

Simulation tests are tests in which the specification parameters of ship equipment are checked during mooring tests in the conditions of the shipyard water area, as close as possible to full-scale ones.

Simulation tests are carried out using special unloading or loading devices - simulators, reproducing the running conditions of the ship's equipment.

An unloading device is a special technological device used for simulation tests of the main power plant. The unloading device serves to create easier operating conditions for the equipment. To unload the propeller along the stop and torque to the calculated values, a reduction in the area of the propeller disk is used due to the ring attachment; a flow-directing chamber that ensures the flow of water to the propeller at a speed equal to its design axial speed; supplying compressed air to the propeller area in order to reduce the density of the water surrounding the propeller. The work of the propeller can also be made easier by reducing the draft of the vessel and, therefore, reducing the depth of the propeller.

Load devices create additional load to check the functionality of the equipment. For example, when testing diesel generators and turbogenerators, the load device is the shore network, where excess electricity is transferred from the vessel being tested.

Simulation tests of the anchor device on moorings are carried out in several ways: by securing the anchor chain on the shore when the main engine is running in reverse at design modes, or by hanging loads on a section of the anchor chain. The most promising method for simulating tests of an anchor device is considered to be a method using a universal loader located on a pontoon and representing a hydromechanical brake with remote control. This method has a number of advantages in terms of versatility, independence of the testing process, and accuracy of reproducing natural conditions.

Simulation devices are also used to test navigation and radar equipment, a gyrocompass, a hydrodynamic log, and hydroacoustic equipment.

To set up radars, special training grounds are set up, located outside the plant and equipped with special reflectors. The direction and distance to the reflectors are known. Radar stations detect reflectors, determine course directions and distances to the reflectors. The data is compared with the true values and adjusted based on station deviations to the required accuracy in determining the required parameters.

Hydroacoustic equipment is checked using a measuring device installed under the bottom of the vessel - a hydrophone, which measures the sound pressure of the vibrator of the hydroacoustic apparatus. Based on the measured sound pressure, the range of the hydroacoustic equipment is recalculated.

Simulation tests approximately halve the duration of the acceptance period, make it possible to create stable test conditions, improve the quality of testing and reduce the consumption of fuel and energy resources.

Sea trials and delivery of the vessel

Sea trials are a technological stage of acceptance tests, the purpose of which is to check the operation of the equipment and its parameters under running conditions, as well as to check the seaworthiness of the vessel (buoyancy, stability, controllability, propulsion, maneuverability, strength on waves). Sea trials are divided into factory and acceptance tests.

The speed is determined by passing the measuring line indicated by leading signs. At a speed of 18 knots, the ship must pass a measuring line of 1 mile, at a speed of 18 - 36 knots - 2 miles, at a speed over 36 knots - 3 miles. This ensures sufficient accuracy in determining speed. Speed is determined as the average value from measurements on several tacks.

The sea trials program provides for determining the agility of the vessel at low, economic, cruising and full speed.

Agility is characterized by circulation elements:

Circulation diameter (distance between return course lines when changing direction by 180°);

Duration of circulation;

Bank angle during circulation, loss of speed.

The circulation diameter is determined in terms of the lengths of the ship's hull. The measurement is carried out by the ship's standard radar stations or special equipment.

The length of the hull also determines the coasting of the vessel due to inertia. When checking inertia, the time from the moment the command is given until the vessel comes to a complete stop or reaches a certain speed is also determined.

Inspection and final acceptance of equipment during sea acceptance tests are carried out while the ship is moving under conditions that ensure that nominal parameters are obtained. According to the requirements of regulatory documents, equipment is tested under normal climatic conditions (atmospheric pressure 1.01 105 Pa, temperature 293 K, relative humidity 70%), with a wind force of no more than 3 points on the Beaufort scale, taking into account the depth and speed of the current in the test area.

At the end of the vessel's acceptance sea trials, an inspection of the main and auxiliary mechanisms and devices is carried out according to the list compiled by the selection committee. The list contains those mechanisms and devices in the operation of which deficiencies have been noticed. The audit consists of revealing these mechanisms and eliminating the shortcomings noticed by the commission.

After the inspection, the ship goes to the control exit. If the commission has no more comments, then a certificate of delivery and acceptance of the vessel is signed.

During the factory sea trials, adjustment and adjustment work is carried out and equipment is prepared for sea acceptance tests. During factory sea trials, the specifications of the main ship engines are checked in terms of power, fuel and oil consumption, and time to develop full power. This check is carried out in various operating modes: at economic speed, cruising speed, full and full speed with all engines running, reverse gear. Simultaneously with checking the power plant, the speed and maneuverability of the vessel are determined. The speed is determined by passing the measuring line indicated by leading signs. At a speed of 18 knots, the ship must pass a measuring line of one mile, at a speed over 18 to 36 knots - two miles, at a speed over 36 knots - three miles. This ensures sufficient accuracy in determining speed. Speed is determined as the average value from measurements on several tacks.

The sea trials program provides for determining the agility of the vessel at low, economic, cruising and full speed. Agility is characterized by circulation elements: circulation diameter (the distance between the return course lines when changing direction by 180°), circulation duration, roll angle during circulation, loss of speed. The circulation diameter is determined in terms of the lengths of the ship's hull. The measurement is carried out by the ship's standard radar stations or special equipment.

Inspection and final acceptance of equipment during sea acceptance tests are carried out while the ship is moving under conditions that ensure that nominal parameters are obtained. According to the requirements of regulatory documents, equipment testing is carried out under normal climatic conditions (atmospheric pressure 1.01 * 10 5 Pa, temperature 293 K, relative humidity 70%), with a wind force of no more than 3 points on the Beaufort scale, taking into account the depth and speed of the current in the testing area.

The construction of any vessel ends with its testing and delivery to the customer. During the delivery period, a set of acceptance tests is carried out in order to comprehensively verify the compliance of the completeness and quality of the vessel with the contract for its construction. Then decisions are made on the commissioning of the vessel. During the tests, a final check is made of the performance of various equipment (including main and auxiliary mechanisms, systems, devices, etc.) and its interaction is worked out, the characteristics of the seaworthiness and habitability of ships are checked. The tests under consideration account for up to 7% of the labor intensity of building the vessel as a whole.

The sequence and scope of acceptance tests of the propulsion equipment and the vessel as a whole are determined by the programs developed by the design bureau of the vessel in accordance with the requirements of the Register of Russia and the provisions of the contract with the customer. Based on the test programs, a certificate log and a list of acceptances are compiled. Certificates are issued for each object subject to acceptance. Acceptance is an inspection or test carried out in accordance with drawings or an acceptance list, and the recognition of products that meet the established specifications.

The certificates indicate:

Test period;
Terms of acceptance of this object;
Acceptance program and its results.

Certificates are usually grouped by design:

Hull part;
Power plant;
Systems;
Devices;
Electrical equipment, etc.

In the list of acceptances, certificates are grouped by stages of acceptance testing.
A separate group includes the so-called construction certificates, which are issued before the start of testing.

Such certificates include, for example:

Results of verification of certificates for ship hull material;
Certificates of testing the tightness of the housing compartments;
Certificates of verification of compliance of hull structures with the design, etc.

The total number of identities can be quite significant. Thus, for a dry cargo ship with a deadweight of about 40,000 tons, the magazine provided about 700 certificates, of which 300 were construction certificates.

The entire period of acceptance testing generally includes the following stages of work:

Preparation for tests;
Mooring tests;
Sea trials;
Inspection of mechanisms;
Control output.

In addition, for certain types of vessels, another stage of testing is provided - operational tests of the lead vessel of the series. They are carried out after the customer signs the acceptance certificate according to the program developed by the ship designer. For example, for fishing vessels, the program includes checking the performance of fishing, technological and refrigeration equipment under operating conditions and checking the compliance of the technical and economic indicators of the vessel with design requirements. Ice tests are provided for icebreakers and ice-navigating vessels.

All mechanisms and equipment arriving at shipyards are subjected to bench tests to check the quality of assembly and establish the parameters entered in the passport. Bench tests reduce the time and cost of subsequent tests on the ship. At the manufacturing plants of mechanisms, appropriate test benches are created for such tests.

The main part of the preparation of the vessel for testing consists of:

Reactivation of ship equipment;
Adjustment;
Setting up and testing in action;
Flushing and checking the cleanliness of pipelines and systems, etc.

Due to the increase in the power supply of ships, the expansion of the use of automation and control equipment, the labor intensity of adjustment and adjustment work is increasing and in some cases reaches 50% of the labor intensity of mooring tests. After completing the preparatory work, mooring tests begin.

Mooring tests are carried out in order to check the quality of installation and performance of ship equipment and determine the readiness of the ship for sea trials. Previously, such tests were carried out only after the vessel was launched and moored at the plant's outfitting quay. Hence the name - mooring tests.

Mooring tests are carried out according to programs and methods developed by the vessel designer. In addition to instructions for conducting tests, the methods contain lists of equipment, fixtures and equipment required for testing, as well as table forms for recording equipment performance indicators and the results of their measurements.

Rice. 1 Diagram of a cable measuring line (a) and a measuring line equipped with secant sections (b)

As ship equipment is improved and automated control systems are used in its composition, both technical means and measurement methods are improved, which are the main source of obtaining a sufficient amount of objective information about the operation of the equipment. During testing, equipment is increasingly being used that automatically records changes in parameters over time and records indicators on tapes of oscilloscopes, recorders, or with digital information displayed on the screens of relevant devices. Instruments and equipment combined into complexes continuously and synchronously record a large number of rapidly changing parameters in both steady-state and unsteady operating modes of ship equipment. All kinds of sensors are used to measure and record various parameters.

During mooring tests, the performance indicators of the presented equipment are recorded and identified deficiencies are noted. If the operating conditions of the equipment during mooring trials do not differ from the operating conditions during sea trials, then, based on the results obtained, this equipment is finally handed over. Equipment, systems and devices, the operating conditions of which during the ship's progress differ from the conditions for mooring tests, are accepted twice, first at mooring tests and finally during sea trials.

The first group of equipment includes, for example:

Ship power plant;
Galley equipment;
Most ship systems, etc.

To the second:

Anchor device;
Steering screw complex, etc.

A significant part of the work during the mooring tests is related to the main power plant. First, they set up and test the auxiliary mechanisms that serve this installation, then they test electrical power equipment and various emergency mechanisms (for example, an emergency diesel generator). In order to save the life of the ship's auxiliary mechanisms, during the testing period the ship is provided with electricity, steam, and compressed air from shore sources.

At the beginning of mooring tests of the main diesel installation, the following is checked:

The operation of the turning device is correct;
Alarms for pressure drop and oil overheating;
Turning off the fuel supply when the rotation speed is higher than permissible;
Engine starting qualities and starting air reserves.

Then they check the operation of the main engine at low and medium speeds, and, if there is a controlled pitch propeller or special load devices, at full speed.

During the period of mooring tests, the equipment of all ship premises is checked and handed over, the tightness tests of the premises are completed, and the salvage equipment is checked.

Mooring tests of a vessel are considered fully completed if all sections of the test program are completed in full and all equipment of the vessel is accepted by representatives of the technical control department of the plant, the Register and the customer in accordance with the mooring period certificate log. After completion of the mooring tests, the vessel is ready for sea trials.

Sea trials are carried out to check the reliability of:

Actions of mechanisms;
System;
Devices;
Instruments and the entire vessel under sea conditions;
As well as compliance with contractual documentation of technical specifications;
Seaworthiness of the vessel.

Tests are carried out in those areas of the sea, reservoir or river where free maneuvering of the vessel is possible, the necessary depths are available and technical support is available for testing individual mechanisms, devices and various equipment of the vessel.

During sea trials, the design specifications of the main ship engines (power, fuel and oil consumption, etc.) are checked under different operating conditions, including:

Economic;
Full;
The most complete;
Rear.

Simultaneously with checking the ship's power plant, sea trials determine the speed and maneuverability of the vessel.

Determining the speed of the ship is necessary to obtain its dependence on the speed of rotation of the propellers and the power of the main power plant. Speed tests are carried out in special areas of the sea (rivers, reservoirs) on a measuring line (measuring mile) shown in Fig. 1. Mandatory conditions for organizing such a line are sufficient depth and the presence of free areas of water at the ends of the measuring section to ensure the safe turn of the vessel on the reverse course and increase in speed. Depth of the water area in the area of the measuring line N l must be no less than the largest value obtained from the formulas:

IN And T- the width and draft of the vessel, respectively, m;
V- the highest possible speed of the vessel, m/s.

The measuring section of the measuring line is designated by secant sections (Fig. 1, b). the distance between which is precisely measured. To ensure sufficient accuracy of measurements, the run length on the measuring line should be one mile - at speeds up to 18 knots, two miles at speeds of 18-36 knots, three miles - at speeds over 36 knots.

To eliminate the influence of current, wind, and random errors in measurements on the test results, several runs of the vessel are carried out in opposite directions at the same propeller speed. Usually limited to three-tack runs. Speed is determined as the average of measurements on several tacks.

When using electrical methods for determining the speed of a vessel, cable measuring lines are used, in which the role of transverse sections cutting off a measuring section of a certain length is assigned to electric cables. The equipment installed on the vessel records the moments of the vessel's passage over the cables and determines the time interval for passing the measuring section (Fig. 1, A).

Speed tests of the lead vessel are carried out by a special group distributed among the measurement sites. The locations must be equipped with reliable communication with the measurement supervisor. During the tests, the propeller shaft rotation speed is recorded using recording devices, and readings of the propeller shaft rotation speed counters are taken continuously at regular intervals (no more than two minutes). Required speed measurement accuracy ±0.2%.

During maneuvering tests, the maneuverability of the vessel and its inertia at various speeds are determined, and the stability of the vessel on course is assessed.

The agility of the vessel is characterized by the elements of circulation:

Tactical diameter (the distance between the return course lines when the ship turns 180°);
Duration of circulation;
The angle of heel of the vessel during circulation;
Losing their speed.

The circulation diameter is measured using standard ship radar stations, as well as using special navigation equipment.

The basis for determining the inertia of a vessel is the assessment of its reversible qualities. Checking the reverses is necessary to determine the duration of the change in the direction of movement of the vessel to the opposite. Reverse is characterized mainly by the length of the path traveled by the ship from the beginning of the reverse to a complete stop. This path is called coasting. The run-out is usually expressed in lengths of the ship's hull, for example, “one length”, “two lengths”, etc. It is measured using radar equipment or using wooden blocks thrown into the water from the bow of the ship along the direction of its movement at the moment the command is given about changing the driving mode. When the stern of the vessel reaches the first dropped bar, the second is dropped, etc. until the vessel comes to a complete stop.

During sea trials in running modes, some elements of electrical equipment and navigation devices are also checked.
Sea trials are considered completed if all sections of the test program have been completed and the results obtained correspond to the specifications of the equipment or vessel.

Inspection of ship machinery and equipment is carried out after completion of sea trials. During the inspection process, a control opening of the mechanism is performed and its individual components are disassembled to determine their condition and identify possible defects. Particular attention is paid to rubbing and high-stress components and parts of disassembled mechanisms. The list of ship equipment subject to inspection, indicating its volume, is compiled by the selection committee.

At the same time as the equipment inspection, deficiencies identified during testing are eliminated. At the same time, the final painting of the ship's hull is carried out.

A control exit to the sea (reservoir, river) is carried out after:

Audits;
Elimination of all identified defects and shortcomings;
Installation in standard places of equipment;
As well as spare tools and devices.

The purpose of the control output is to check the operation of the equipment that has been audited.

Acceptance tests are organized and carried out by the ship's building plant together with representatives of counterparty plants, whose participation is stipulated in separate agreements with them. The preparation and conduct of tests is carried out by the plant’s delivery team, led by the responsible commissioner, consisting of highly qualified workers and engineers from both this plant and some contractors. The composition of the delivery team is appointed by order of the plant director. The acceptance team also includes the test batch, whose responsibilities include ensuring the normal operation of all measuring instruments and recording their readings during testing.

The acceptance of the vessel during commissioning tests is carried out by the acceptance committee, which includes representatives of the organization supervising the construction, the captain of the vessel and representatives of the customer and the design organization. Upon completion of the acceptance tests, the acceptance committee signs the vessel acceptance certificate. From this moment the vessel is considered delivered to the customer.

After mooring are carried out sea trials related to going to sea. Tests are carried out in a specially equipped water area called "measuring mile" ("measuring line"). This is a route of a certain length (for example, one mile), the beginning and end of which are marked by secant sections - a pair of coastal wooden shields with a vertical black stripe painted on them. When the lanes merge into one for an observer on the vessel, the vessel is on target. One alignment marks the beginning and the other the end of the measuring section. The direction of movement of the vessel is set either by guide lines or by the course indicated on the map.
To carry out the tests, a commission is formed, all the results of its work are documented in the form of protocols, where, in particular, the names and positions of the commission members, the time and conditions of the tests, information about the measuring instruments used, and measurement results are entered.
At the time of testing, the vessel itself, the measuring mile itself, the test conditions and measuring instruments are subject to certain requirements.
The vessel must be freshly painted (no more than 15 days, and in cold water - 30 days after leaving the dock), and must not have a list or trim. During sea trials, the displacement is usually less than when fully loaded, which is taken into account when processing the results. For this purpose, it is recommended to measure the drafts at the ends and on both sides amidships, which will make it possible to take into account the list and general bend of the vessel. During docking, the condition of the protruding parts is examined and, if necessary, their damage is repaired. Special requirements are imposed on the condition of ship propulsors. The geometric characteristics of the propellers are checked, and if there is damage to the blades, they are repaired.
Tests are carried out in calm weather: wind force is allowed up to approximately 3 points (for small ships - up to 1000 tons - up to 2 points, for large ships - over 20,000 tons - up to 4 points), and waves - up to 2 points (also for small ships - less, and for large ones - more), and the leading signs should be clearly visible. In the area of the measured mile there should not be a strong current, especially in the transverse direction, which distorts the speed measurement results. It is very important that the depth at the meter be deep enough to avoid the influence of shallow water on the resistance. Let us recall that a sharp increase in resistance begins at the Froude number in depth

Where H is the depth of water at a measured mile. It is believed that the depth of water at a measured mile must exceed the greater of the two values calculated using the formulas

Where B and T are the width and draft of the vessel, respectively; v is the highest speed of the vessel during testing. Thus, at normal speeds for transport ships of 15-16 knots, the required depth is approximately 25-30 m (if the vessel's draft is not very deep). As speed increases, the required depth increases rapidly.
Errors in speed measurements should not exceed 0.5%, time of passage of the measuring section - 0.2 s, number of propeller shaft revolutions per minute - 0.2%, torque on the propeller shaft - 3% of the torque at rated power, fuel consumption - 0.5%, wind speed - 2%, wind direction -5%, vessel draft - 2 cm, water and air temperature - 1 degree, start and end time of the run - 1 min.
The sea trials program provides for the vessel to move in several modes corresponding to the main engine speed from minimum to maximum, including nominal. For lead transport vessels with internal combustion engines, the following modes are mandatory: n = nom, n = 1.03nom, n = 0.91nom, n = 0.80nom, n = 0.63nom. In each mode, the ship makes three runs (the movement pattern is shown in Fig. 11.1; the curve that the ship describes when turning in the opposite direction is called the “coordinate”). To do this, it falls on a given course, which must be precisely maintained, the required rotation speed is set, and the established speed is picked up. There are observers on the ship with stopwatches, the number of which must be at least three. When passing the first target, the stopwatches start, the second – stop. The results are recorded in the protocol; if one of the three results is significantly different from the others, it is discarded. The speed of the vessel during the run is calculated as the quotient of the measured mile length divided by the average time. The average speed over three runs in one mode is calculated using the formula:

Rice. 11.1. Vessel traffic pattern on a measured mile

This takes into account the possible flow speed, which will be taken into account twice with a plus and twice with a minus. Moreover, if during the test the speed gradually changed approximately linearly, the formula allows you to eliminate the influence of the flow. This is faster and more accurate than determining the average speed over four runs.
Modern navigation systems make it possible to accurately determine the position of a vessel anywhere in the World Ocean and at any time, which makes it possible in principle to conduct high-speed tests in places not specially equipped for this purpose. However, the possible flow must be taken into account.
Another important measured characteristic is engine speed. On ships under operating conditions, it is measured by tachometers, but for test conditions their accuracy is insufficient. Here they use a tachoscope - a mechanical or electrical device that has a revolution counter and a stopwatch in one housing. The tachoscope roller rests against the engine shaft at the nose end; when pressed, both the stopwatch and the revolution counter start working, and when released they stop.
There are pulse tachoscopes operating on various physical principles. They are also used in cases where it is not possible to connect a tachoscope to the end of the shaft.
It is highly advisable to also measure engine power and propeller thrust or thrust. These measurements are technically more complex and less accurate. One way to measure the power of diesel plants is by fuel consumption. To do this, a measuring tank is included in the fuel pipeline, at the inlet and outlet of which there are transparent tubes with marks. At some point, the fuel pipeline is closed, and fuel from the tank begins to be consumed. At the moment when the fuel level is equal to the input mark on the tank, the stopwatch is started, and at the exit mark it is stopped. Knowing the specific fuel consumption in g/kWh and measuring the actual consumption in g/h, the power is calculated. But specific fuel consumption is not a completely stable characteristic and does not guarantee accuracy. The error of this method is approximately 4-5%.
Diesel power can also be measured using an indicator diagram - recording the pressure in the engine cylinder as a function of piston movement. There are special devices for this purpose. The sum of the powers of all cylinders gives the indicated power; the effective engine power is less due to losses in the engine (friction), which is taken into account by the mechanical efficiency, the value of which can be determined during bench tests of a diesel engine at the manufacturer, but is also not completely stable.
The power of steam and gas turbine plants is determined by other methods that we do not consider. On ships with electric propulsion, power can be determined from current parameters.
There are other, more complex ways. Since the power PD is uniquely related to the torque Q transmitted by the shafting (PD = 2пn * Q),
You can use torsiometers to measure the torque through the angle of rotation of the shaft f on a certain base 1. In this case

Here Ip is the polar moment of inertia of the shaft section; for solid round section with diameter D

Based on the operating principle, a distinction is made between electric and acoustic torsiometers. To convert the angle of twist into torque, knowledge of the shear modulus G is required, which is not a completely stable characteristic of the material. If you first calibrate the measuring section of the shaft to determine the shear modulus, the error in determining the torque is 2-3%.
Using strain gauges glued at an angle of 45 degrees to the shaft axis, it is possible to measure tangential stresses in the shaft (strictly speaking, shaft deformation from torsion), which can be easily converted into torque and power on the shaft. But here a serious problem arises in transmitting the signal from the rotating shaft to the stationary measuring equipment. Metal deformations are measured in hundredths of a percent, the same order of change in the electrical resistance of sensors that need to be measured with high accuracy. If readings are taken using slip rings and brushes, a resistance arises in the contact, the fluctuations of which can be of the same order of magnitude as the measured signal. To reduce this resistance, firstly, the pressing force of the brushes is selected, and secondly, attempts are made to use low-melting metals, for example gallium alloys (the melting point of pure gallium is 30 C). These errors can be avoided if a pre-amplifier and a radio transmitter are also placed on the rotating shaft, and a receiver and other measuring equipment nearby. Note that an additional error with this method arises due to inaccurate knowledge of the shear modulus of the shaft material.
Measuring the thrust or thrust of a screw is even more difficult to perform. For example, the thrust of a screw on moorings can be determined by the tension force of the cable connecting the ship to the shore, for which powerful dynamometers or metal plates with strain gauges glued to them are used.
The most accurate results can be obtained by replacing one of the intermediate shafts with a special insert equipped with instruments for measuring both thrust and torque. This insert is made specifically for a specific series of ships. A pressure meter (hydraulic or electric) can also be installed in a thrust bearing. The error in measuring the stop usually exceeds 5%.
Test results are processed and analyzed. To convert from displacement at the time of testing to full displacement, the Admiralty formula is usually used. It is desirable that the vessel reach its design speed at the nominal engine operating mode. Sometimes the test speed turns out to be less than the design speed. This may be due to insufficient depth at the measuring mile or due to the roughness of the skin - these cases should be excluded during preparation for testing. As we noted, errors may be due to the insufficient level of development of science and the characteristics of the constructed vessel. There are also cases when the test speed exceeds the design speed.
If during the tests the ship's speed, propeller shaft rotation frequency and power were measured (thrust often cannot be measured), then based on their results the coefficients of the associated flow and the influence of the unevenness of the velocity field on the torque, which were previously known from the data of model tests, can be corrected. Further, having calculated the resistance of the vessel, if there is a discrepancy with the results of model tests, it is possible to correct either the resistance or the suction coefficient.
Sometimes propeller elements are adjusted based on test results.

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