A method for calculating the sinking stability of a gravity type atmospheric dry chamber

Abstract

The application discloses a sinking stability calculation method for a gravity type normal-pressure dry cabin, which comprises the following steps: S1, determining the prerequisite for sinking stability calculation: clearly defining the size and weight of the cabin body and environmental parameters; S2, calculating the amount of counterweight and ballast water required for overcoming the buoyancy of the gravity type normal-pressure dry cabin under different working conditions to meet the initial stability requirement, which is recorded as the counterweight required for meeting the initial stability; S3, calculating the horizontal load borne by the gravity type normal-pressure dry cabin under different working conditions; S4, calculating the counterweight amount required for the gravity type normal-pressure dry cabin to not horizontally slide and the counterweight amount required for the gravity type normal-pressure dry cabin to not overturn in order to overcome the horizontal load under different working conditions, which is recorded as the counterweight required for overcoming the action of wind and current; and S5, adding the counterweight results of steps S2 and S4 to obtain the total counterweight required for the gravity type normal-pressure dry cabin under different working conditions; and the scheme of adding counterweight or ballast water for keeping the stability of the gravity type normal-pressure dry cabin under different working conditions is mainly studied.

Description

Technical Field

[0001] This invention relates to the field of marine oil engineering calculations, and more particularly, to a method for calculating the stability of a gravity-type atmospheric pressure dry tank. Background Technology

[0002] A gravity-type atmospheric pressure dry chamber is a structure used for repairing or rerouting subsea pipelines under atmospheric pressure. Previously, without a dry chamber, repairs to subsea pipelines involved two methods: either divers working in a wet underwater environment, or using a floating crane to lift the pipeline above the ship's deck for repairs, followed by lowering it back to the seabed. Repairs without a dry chamber required shutdowns, were costly, and time-consuming. Using a gravity-type atmospheric pressure dry chamber allows for repairs with or without shutdown, while also reducing the risks to divers.

[0003] Gravity-type atmospheric pressure dry tanks are structures that improve the efficiency of subsea pipeline maintenance and repair. However, this structure has unique characteristics, and the API standards commonly used in marine engineering are not entirely applicable to this type of "isolated pier" structure. Therefore, new solutions are needed. The calculation method for the settlement stability of gravity-type atmospheric pressure dry tanks mainly studies the schemes of adding counterweights or ballast water to maintain stability and prevent capsizing under conditions such as high tide, low tide, and environmental loads. This is one of the necessary verification contents to ensure the safety of dry tank operations, and this method emerged with the use of gravity-type atmospheric pressure dry tanks. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for calculating the amount of counterweight or ballast water required to maintain stability in a gravity-type atmospheric pressure dry chamber.

[0005] To address the aforementioned technical problems, this invention provides a method for calculating the settling stability of a gravity-type atmospheric pressure dry chamber, comprising the following steps:

[0006] S1: Prerequisites for determining the settlement stability calculation: Determine the dimensions and weight of the enclosure and environmental parameters;

[0007] S2: Calculate the amount of counterweight and ballast water required to overcome buoyancy in the gravity-type atmospheric pressure dry tank under different operating conditions while meeting the initial stability requirements. Record the required counterweight to meet the initial stability requirements.

[0008] S3: Calculate the horizontal load on the gravity-type atmospheric pressure dry chamber under different operating conditions;

[0009] S4: Calculate the counterweight required to prevent horizontal slippage and overturning of the gravity-type atmospheric pressure dry chamber under different working conditions, and record it as the counterweight required to overcome the effects of wind, waves and currents.

[0010] S5: Combine the loading results of steps S2 and S4 to obtain the total loading required for different operating conditions of the gravity-type atmospheric pressure dry chamber.

[0011] According to a preferred embodiment of the present invention, the determination of environmental parameters in step S1 requires determining the highest and lowest tide levels during the operation period based on the tide table; determining the maximum wave height and maximum current velocity during the operation period; determining the wind speed that restricts the operation; and determining the friction coefficient between the bottom surface of the gravity-type atmospheric pressure dry tank and the soil.

[0012] According to a preferred embodiment of the present invention, the different operating conditions in steps S2, S3 and S4 include at least three types: adding only the counterweight without adding the required amount of ballast water at low tide; adding only the counterweight without adding the required amount of ballast water at high tide; using the counterweight at low tide for both low tide and high tide; and adding the amount of ballast water inside during high tide.

[0013] According to a preferred embodiment of the present invention, the horizontal load in step S3 is the resultant force of wind load and wave load.

[0014] According to a preferred embodiment of the present invention, the wave load is calculated using the calculation method in the "Harbor Hydrology Code".

[0015] According to a preferred embodiment of the present invention, in step S4, the load data required to overcome the effects of wind, waves and currents is taken as the larger of the load required to prevent horizontal slippage and the load required to prevent overturning.

[0016] According to a preferred embodiment of the present invention, the counterweights in steps S2 and S4 should be applied evenly on both sides.

[0017] According to a preferred embodiment of the present invention, the gravity-type atmospheric pressure dry chamber has a rectangular box structure.

[0018] The technical advantages of this invention are as follows:

[0019] 1. This invention discloses a method for calculating the stability of a gravity-type atmospheric pressure dry tank. First, it clarifies the preconditions for the calculation. Second, it calculates the required ballast to meet the initial stability requirement of the gravity-type atmospheric pressure dry tank under different operating conditions, i.e., the ballast required to overcome buoyancy and meet the initial stability requirement in calm water. Then, it calculates the required ballast to overcome the effects of wind, waves, and currents under different operating conditions, i.e., the ballast required to overcome the forces of wind, waves, and currents. Finally, it sums the required ballast to meet the initial stability requirement and the required ballast to overcome the effects of wind, waves, and currents to obtain the total ballast. Thus, it realizes a method for calculating the amount of ballast or ballast water required to maintain stability and prevent capsizing of a gravity-type atmospheric pressure dry tank under conditions such as high tide, low tide, and environmental loads.

[0020] 2. The gravity-type atmospheric pressure dry tank settlement stability calculation method disclosed in this invention refers to the port hydrological code. It uses a self-developed program to calculate the settlement stability of the gravity-type atmospheric pressure dry tank during operation, and determines whether it will capsize. This determines the scheme of adding counterweight or pressurized water during the operation of the gravity-type atmospheric pressure dry tank, thus ensuring the safety of the gravity-type atmospheric pressure dry tank during operation.

[0021] 3. The counterweight calculated by this method can provide preliminary data for other seat stability calculations, and this method can also be used to verify the sinking stability calculation of different forms of gravity-type atmospheric pressure dry chambers such as quadrilaterals and pentagons. Attached Figure Description

[0022] Figure 1 This is a front view of the gravity-type atmospheric-pressure dry chamber used in the present invention's method for calculating the stability of a gravity-type atmospheric-pressure dry chamber.

[0023] Figure 2 This is a side view of a gravity-type atmospheric pressure dry chamber, which is the subject of the present invention's method for calculating the stability of a gravity-type atmospheric pressure dry chamber.

[0024] Attached diagram labels: 1-hull; 2-sealed door; 3-anti-sinking plate. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the invention.

[0026] like Figure 1 and Figure 2 As shown, a gravity-type atmospheric pressure dry chamber is a structure for maintenance, emergency repair, or rerouting of submarine pipelines under atmospheric pressure. It consists of a chamber 1, which is generally a steel box-shaped structure with an open top. Sealed doors 2 are usually installed on the front and back of the chamber 1, and sometimes sealed doors 2 are also installed on the bottom. A sinking plate 3 is installed and connected to each side of the lower end of the chamber 1 perpendicular to the chamber 1.

[0027] The calculation method for the settling stability of a gravity-type atmospheric pressure dry chamber is as follows:

[0028] Step S1: Determine the prerequisites for the settlement stability calculation: Box dimensions: 3m×3m×10.6m; Box weight: 39.4t (SACS model weight); Low tide water depth: 6.937m; High tide water depth: 9.247m; Assume the foundation is flat and does not settle, and the friction coefficient with the box is 0.3.

[0029] Step S2: Calculation of load requirements to satisfy high initial stability:

[0030] The calculations were performed for three scenarios: a low tide level of 6.937m, a high tide level of 9.247m with only ballast water and no additional ballast water, and a high tide level of 9.247m with both low tide ballast water and ballast water. The calculation process is as follows:

[0031] Initial stability calculation: Formula for calculating the height of the initial metacenter: GM = Z b +rZ g ;GM: Initial stationary height under accounting conditions; Z b : Height of the center of buoyancy at the corresponding draft; r = It / A: Radius of the transverse metacenter at the corresponding draft; It: Moment of inertia of the section; A: Draft volume; Z g : Center of gravity height under calculated conditions. The inspection standard is stability lateral alignment: GM not less than 0.15m.

[0032] The initial stability calculations for low tide, high tide, and ballast water schemes are shown in Table 1. If GM is less than 0.15m, additional ballast is considered until GM meets the requirements. The ballast weight during high tide is considered the same as that during low tide, and the remaining parts are considered based on the added water level. The table below only uses a high tide of 9.247m as an example for ballast water calculations. The final ballast data required to meet initial stability are: Low tide: 28.667m; High tide: 53.315m; Ballast water scheme: 28.667m.

[0033]

[0034]

[0035] Table 1

[0036] Step S3: Calculate the horizontal loads on the gravity-type atmospheric pressure dry chamber under different operating conditions:

[0037] The horizontal load F = F1 + F2; where: F1 is the wind load on hull 1; F2 is the wave load on hull 1.

[0038] F1 wind load = 0.0473v 2 CsA; where V is the wind speed (m / s); Cs is the shape factor (1); and A is the windward area (m²). F2 wave load is calculated according to the "JTJ 213-98 Harbor Hydrology Code".

[0039] Step S4: Calculation of load required to overcome wind, waves and current: Horizontal load calculation and overturning resistance calculation are shown in Table 2, where M max F2 is the torque relative to the reference plane.

[0040] The data required to overcome the effects of wind, waves and currents are as follows: Low tide: 37.89; High tide: 62.07; Ballast water scheme: 30.88.

[0041]

[0042]

[0043] Table 2

[0044] Step S5: Combine the loading results from steps S2 and S4, as shown in Table 3, to obtain the total loading (rounded) required for different operating conditions of the gravity-type atmospheric pressure dry tank: 67t for a water level of 6.937m; 115t for a water level of 9.247m.

[0045]

[0046] Table 3

[0047] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for calculating the sinking stability of a gravity type atmospheric dry chamber, characterized in that, It comprises the following steps: S1: determining the precondition of the sinking stability calculation: clearly defining the box size and weight and environmental parameters; S2: calculating the amount of counterweight and ballast water required to overcome the buoyancy of the gravity type normal pressure dry cabin under different working conditions to meet the initial stability requirements, recorded as high initial stability required ballast; S3: calculating the horizontal load received by the gravity type normal pressure dry cabin under different working conditions; S4: calculating the amount of counterweight required for the gravity type normal pressure dry cabin to not produce horizontal sliding and the amount of counterweight required for not overturning in order to overcome the horizontal load under different working conditions, recorded as wind and wave flow action required ballast; S5: adding the ballast results of steps S2 and S4 to obtain the total ballast required for the gravity type normal pressure dry cabin under different working conditions; The different working conditions in steps S2, S3 and S4 include at least three kinds, the amount of counterweight required when only adding counterweight without adding ballast water at low tide; the amount of counterweight required when only adding counterweight without adding ballast water at high tide; the amount of counterweight required at low tide and the amount of ballast water added to the inside during high tide when using the amount of counterweight at low tide; The data of wind and wave flow action required ballast in step S4 is the larger one of the amount of counterweight required for not producing horizontal sliding and the amount of counterweight required for not overturning.

2. The method according to claim 1, wherein, In step S1, the environmental parameters need to be determined according to the tide table, the highest and lowest tide levels during the operation period are determined; the maximum wave height and maximum flow rate during the operation period are determined; The wind speed limiting operation and the friction coefficient between the bottom surface of the gravity type normal pressure dry cabin and the soil are determined.

3. The method according to claim 1, wherein, The horizontal load in step S3 is the resultant force of wind load and wave load.

4. The method according to claim 3, wherein, The calculation of wave load uses the calculation method in the "Harbor Hydrology Specification".

5. The method according to claim 1, wherein, The counterweight in steps S2 and S4 should be applied uniformly to the left and right.

6. The method according to claim 1, wherein, The structure of the gravity type normal pressure dry cabin is a rectangular box.

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