Method of inspecting vessel cargo hold

Abstract

The present disclosure relates to a method for inspecting whether the cargo hold of a ship transporting liquid cargo has been properly cleaned, that is, whether there is any remaining amount of previous cargo in the cargo hold, and can provide an accurate and rapid method for inspecting the ship's cargo hold using liquid caustic soda.

Description

Technology Field

[0001] The present disclosure relates to a method for inspecting whether the cargo hold of a ship transporting liquid cargo has been properly cleaned, that is, whether the remaining amount of previous cargo exists inside the tank of the cargo hold. Background Technology

[0002] Vessels transporting large volumes of liquid bulk cargo are classified into three types: crude oil carriers, chemical tankers, and liquefied natural gas carriers. While crude oil carriers and liquefied natural gas carriers are dedicated vessels (i.e., their cargo is designated as crude oil or LNG), chemical tankers are not. Therefore, a voyage is completed when cargo A is loaded at the loading port and unloaded at the unloading port, and other cargoes such as B, C, or D may be loaded on the next voyage. When loading cargo other than the same cargo A after unloading it, cleaning and washing the ship's tanks and cargo holds are essential before loading the new cargo. When loading the next cargo, if a residue of the previous cargo A remains, there is a risk that the purity of the newly loaded cargo may decrease or deteriorate; therefore, after cleaning and washing the ship's tanks or cargo holds, it must be inspected to ensure that there is no residue of cargo A.

[0003] At this time, inspectors assess the cleanliness status through visual inspection or by rubbing the walls of the ship's tanks while wearing white gloves; however, these methods lack accuracy, are unscientific, and may lead to disputes with relevant parties (e.g., cleaning personnel) later on. Accordingly, a conventional technique to inspect for the remaining amount of previous cargo involves performing the Hydrocarbon Test, Chloride Test, and Potassium Permanganate Time Test, collectively known as the Wall Wash Test (WWT). However, this method is complex and takes a significant amount of time (approximately one hour or more) to test a single sample; therefore, even if multiple people perform the inspection simultaneously, it still takes a considerable amount of time, especially when the vessel has multiple tanks. Since demurrage is calculated based on time, the long duration of the inspection leads to economic losses. Consequently, there is a demand for the development of a rapid and simple method for inspecting ship cargo holds. The problem to be solved

[0004] The purpose of the present disclosure is to provide a method for inspecting a ship's cargo hold that can accurately and quickly determine whether there is any remaining cargo from previous shipments transported by the ship. means of solving the problem

[0005] The present disclosure comprises the steps of: flowing liquid caustic soda onto the inner wall of a tank in a ship's cargo hold and collecting the flowed liquid caustic soda as a sample; and

[0006] a) a step of measuring the pH of the above sample at room temperature; and

[0007] b) a step of inspecting for the presence or absence of previous cargo in the ship's cargo hold, including at least one step of checking the turbidity of the sample;

[0008] A method for inspecting a ship's cargo hold, including...

[0009] In one aspect, if the previous cargo is an acidic substance, the above step a) is included, and the presence or absence of the previous cargo in the ship's cargo hold can be checked by determining whether the pH of the sample has decreased compared to the pH of liquid caustic soda.

[0010] In one aspect, if the pH reduction rate of the sample relative to the pH of the liquid caustic soda is 7% or more, the cargo tank may need to be re-cleaned.

[0011] In one aspect, if the aforementioned prior cargo is an animal or vegetable oil, the above step b) is included, and the turbidity of the sample can be confirmed by comparing the turbidity of the sample with the turbidity of the following 1 to 4 standard solutions.

[0012] First standard solution = pure caustic soda

[0013] Standard Solution No. 2 = 1 ppm mixture of oils and fats in pure caustic soda

[0014] Third standard solution = 5 ppm oil-based mixed solution in pure caustic soda and

[0015] Standard Solution No. 4 = 10 ppm oil and fat mixed solution in pure caustic soda

[0016] In one aspect, if the turbidity of the sample is higher than the turbidity of the third standard solution, the cargo hold may need to be re-cleaned.

[0017] In one aspect, if the aforementioned prior cargo is a hydrocarbon-based material, the above step b) is included, and the turbidity of the sample can be confirmed by comparing the turbidity of the sample with the turbidity of the following standard solutions A to D.

[0018] Standard Solution A: Pure Caustic Soda

[0019] Standard Solution B: 1 ppm hydrocarbon mixed solution in pure caustic soda

[0020] Standard Solution C: 5 ppm mixed solution of hydrocarbons in pure caustic soda and

[0021] Standard Solution D: 10 ppm hydrocarbon mixed solution in pure caustic soda

[0022] In one aspect, if the turbidity of the sample is higher than the turbidity of standard solution C, the cargo hold may need to be re-cleaned.

[0023] In one aspect, the cargo loaded after inspecting the ship's cargo hold may be liquid caustic soda.

[0024] In one aspect, the liquid caustic soda may have a pH of 13 to 14 at room temperature. Effects of the invention

[0025] The ship cargo hold inspection method of the present disclosure can quickly and simply inspect for the presence of any remaining cargo in the ship's cargo hold. Furthermore, the ship's crew can easily perform the ship cargo hold inspection method of the present disclosure. Therefore, it has the effect of preventing time and economic losses in advance by reducing the time required to inspect the cleanliness of the ship's cargo hold. Specific details for implementing the invention

[0026] The embodiments or aspects of the present disclosure are illustrative for the purpose of explaining the technical concept of the present disclosure. The scope of rights according to the present disclosure is not limited to the embodiments or aspects presented below or the specific descriptions thereof.

[0027] All technical and scientific terms used in this disclosure, unless otherwise defined, have the meaning generally understood by those skilled in the art to which this disclosure pertains. All terms used in this disclosure are selected for the purpose of further clarifying this disclosure and are not selected to limit the scope of the rights under this disclosure.

[0028] Unless otherwise stated, singular expressions described in this disclosure may include a plural meaning, and this applies likewise to singular expressions described in the claims.

[0029] In one aspect of the present disclosure, the term “about” is used with the intent to include manufacturing process errors included in specific figures or slight numerical adjustments falling within the scope of the technical concept of the present disclosure. For example, the term “about” means a range of ± 10% of the value it designates, ± 5% in one aspect, and ± 2% in another aspect. In the field of the present disclosure, unless the value is specifically stated to require a narrower range, this level of approximation is appropriate.

[0030] In the present disclosure, pH or turbidity may be understood as measured at room temperature (about 15°C) unless otherwise stated.

[0031] Hereinafter, embodiments of the present disclosure will be described in detail.

[0032] The present disclosure comprises the steps of: flowing liquid caustic soda onto the inner wall of a tank in a ship's cargo hold and collecting the flowed liquid caustic soda as a sample; and

[0033] a) a step of measuring the pH of the sample; and

[0034] b) a step of inspecting for the presence of previous cargo remaining in the ship's cargo hold, including at least one step of checking the turbidity of the sample;

[0035] A method for inspecting a ship's cargo hold, including...

[0036] In one aspect, a sample may be collected by flowing about 500 mL to about 100 mL, or about 500 mL to about 250 mL (e.g., about 100 mL or about 500 mL) of liquid caustic soda onto the inner wall of a tank, but is not limited thereto. The amount of liquid caustic soda flowing onto the inner wall of the tank is sufficient if it is an amount sufficient to collect a sample. The liquid caustic soda that flows down can be collected in a bottle using a funnel or a tray to collect a sample.

[0037] In one aspect, a) the presence or absence of a previous shipment can be checked by measuring the pH of the sample. If the inner wall of the tank is contaminated, the pH of the sample differs from the pH of the liquid caustic soda due to the neutralization reaction between the liquid caustic soda and the contaminant (e.g., previous shipment). The pH can be measured using a pH meter, paper pH test strips, or a pH test solution, but is not limited to any method capable of measuring pH.

[0038] In one aspect, b) the presence of a remaining amount of previous cargo can be inspected by checking the turbidity of the sample. Liquid caustic soda is colorless and has no turbidity; however, if the inner walls of the tank are contaminated, the turbidity of the sample increases as the contaminants dissolve in the liquid caustic soda due to the dissolution reaction between the liquid caustic soda and the contaminants (e.g., previous cargo). Additionally, since liquid caustic soda is a strong base, it can easily dissolve contaminants on the inner walls of the tank. The turbidity of the sample can be checked visually. By preparing a turbidity standard solution in advance, the turbidity of the sample can be confirmed by comparing it with the turbidity standard solution.

[0039] In one aspect, the step of checking for the presence or absence of a remaining quantity of the previous cargo may include at least one of the steps a) and b). For example, if information regarding the type of the previous cargo is available, step a) or step b) may be performed considering its characteristics, and if the type of the previous cargo is unknown, both steps a) and b) may be performed. If the step of checking for the presence or absence of a remaining quantity of the previous cargo includes both steps a) and b), steps a) and b) may be performed simultaneously, or sequentially, step b) followed by step a), or step a) followed by step b).

[0040] In one aspect, the cargo loaded after inspecting the ship's cargo hold may be liquid caustic soda. In this case, the process of using liquid caustic soda to inspect for the presence of remaining previous cargo in the ship's cargo hold and washing off the liquid caustic soda adhering to the inner walls of the tank can be omitted. Furthermore, since both the sample used during inspection and the subsequent cargo being loaded are liquid caustic soda, there is no concern that the sample used during inspection may affect the subsequent cargo, such as by lowering its purity or altering its properties.

[0041] In one aspect, the liquid caustic soda may have a pH of 13 to 14 at room temperature. The liquid caustic soda used in the present disclosure may be an aqueous solution of sodium hydroxide (NaOH) in an amount of about 50 wt%, or 49 to 51 wt%, 49.5 to 50.5 wt%, about 50 wt%, or 50 wt%. Since the ship cargo hold inspection method of the present disclosure uses liquid caustic soda, which is a strong base, safety accidents can be prevented by using goggles and rubber gloves for the safety of the inspector.

[0042] In one aspect, the ship cargo hold inspection method of the present disclosure may take about 10 to 20 minutes per cargo hold.

[0043] In one aspect, if information regarding the type of previous cargo is known, the ship cargo hold inspection method of the present disclosure may be performed according to the type of previous cargo.

[0044] If the ship's previous cargo is an acidic substance

[0045] In one aspect, if the previous cargo of the ship is an acidic substance, step a) above is included, and the presence of the previous cargo in the ship's cargo hold can be checked by determining whether the pH of the sample has decreased compared to the pH of the liquid caustic soda under the same temperature conditions. If the inner wall of the tank is contaminated with the previous cargo which is an acidic substance, the pH of the sample decreases compared to the pH of the liquid caustic soda due to a neutralization reaction between the liquid caustic soda and the contaminant. If the rate of decrease in the pH of the sample relative to the pH of the liquid caustic soda is 7% or more (i.e., [(pH of the liquid caustic soda - pH of the sample) / pH of the liquid caustic soda] is 0.07 or more), the cargo hold may need to be re-cleaned.

[0046] If the vessel's previous cargo consists of animal or vegetable oils

[0047] Even after washing, oil components may remain in cargo tanks that have transported animal or vegetable oils. In particular, if the cargo being shipped after inspection is liquid caustic soda, there is a high risk of spoilage if oil components remain, as liquid caustic soda is a solvent. Therefore, it is essential to inspect for any residual oil components from the previous cargo after washing.

[0048] In one aspect, if the vessel's previous cargo consists of animal or vegetable oils, step b) above is included, and the turbidity of the sample can be verified by comparing the sample with the following first to fourth standard solutions. The turbidity of the sample changes due to the dissolution reaction between the liquid caustic soda and the oils. If the turbidity of the sample is higher than that of the third standard solution, re-cleaning of the cargo hold may be required.

[0049] Standard Solution 1: Pure Caustic Soda

[0050] Standard Solution No. 2: 1 ppm mixture of oils and fats in pure caustic soda

[0051] Third standard solution: 5 ppm mixed solution of oils and fats in pure caustic soda and

[0052] Standard Solution No. 4: 10 ppm oil and fat mixed solution in pure caustic soda

[0053] The above oil mixture solution is prepared in advance before the vessel enters port and may be prepared using the same oils as the previous cargo based on information provided by the shipping company; however, if the oils are unknown substances or if the information regarding the oils is unclear, canola oil or palm oil may be used as the oil.

[0054] In cases where the vessel's previous cargo is a hydrocarbon substance

[0055] Cargo tanks that have transported hydrocarbon-based cargo, such as gasoline including lubricating oil, are difficult to clean, and even if cleaned, they cannot be trusted. Furthermore, if the inside of a ship's cargo tank is contaminated with hydrocarbon-based substances from the previous cargo, it is difficult to detect with the naked eye, making it essential to inspect for any remaining traces.

[0056] In one aspect, if the vessel's previous cargo is a hydrocarbon material, the above step b) is included, and the turbidity of the sample can be verified by comparing the sample with the following standard solutions A to D. The turbidity of the sample changes due to the dissolution reaction between the liquid caustic soda and the hydrocarbon material. If the turbidity of the sample is higher than that of standard solution C, re-cleaning of the cargo hold may be required.

[0057] Standard Solution A: Pure Caustic Soda

[0058] Standard Solution B: 1 ppm hydrocarbon mixed solution in pure caustic soda

[0059] Standard Solution C: 5 ppm mixed solution of hydrocarbons in pure caustic soda and

[0060] Standard Solution D: 10 ppm hydrocarbon mixed solution in pure caustic soda

[0061] The above hydrocarbon mixture solution is prepared in advance before the vessel enters port and may be prepared using the same hydrocarbon as the previous cargo based on information provided by the shipping company; however, if the hydrocarbon is an unknown substance or if the information regarding the hydrocarbon is unclear, it may be prepared using gas oil as the hydrocarbon.

[0062] Hereinafter, embodiments of the present disclosure will be described in detail. However, the following embodiments are provided merely to facilitate a better understanding of the present disclosure and do not limit the scope of the present disclosure.

[0063] On May 22, 2024, the vessel "ARGENT GEBARA" entered Ulsan Port to load 7,000 tons of liquid caustic soda bound for the United States and 7,250 tons of liquid caustic soda bound for Canada. Prior to entering Ulsan Port, while the vessel was anchored in Mailao, Taiwan, the owner conducted three preliminary tests—hydrocarbon testing, chloride testing, and potassium permanganate time testing—on the six cargo holds (cargo hold numbers 1-P, 1-S, 3-P, 3-S, 7-P, and 7-S) intended for loading, and the vessels passed them. The previous cargo in the holds was canola oil. The inspection took at least 6 hours. In contrast, upon entering Ulsan Port, the vessel cargo hold inspection method disclosed herein was performed, and the inspection was completed in just 1 hour.

Claims

Claim 1 A method for inspecting a ship's cargo hold, comprising: a step of flowing liquid caustic soda onto the inner wall of a tank of a ship's cargo hold and collecting the flowing liquid caustic soda as a sample; and a step of measuring the pH of the sample at room temperature; and b) a step of checking the turbidity of the sample to inspect for the presence or absence of a remaining amount of previous cargo in the ship's cargo hold, wherein if the previous cargo is animal or vegetable oils, step b) is included, and the turbidity of the sample is confirmed by comparing the turbidity of the sample with the turbidity of the following first to fourth standard solutions: first standard solution = pure caustic soda; second standard solution = pure caustic soda mixed with 1 ppm of oils; third standard solution = pure caustic soda mixed with 5 ppm of oils; fourth standard solution = pure caustic soda mixed with 10 ppm of oils. Claim 2 A method for inspecting a ship's cargo hold according to claim 1, wherein if the turbidity of the sample is higher than the turbidity of the third standard solution, re-cleaning of the cargo hold is required. Claim 3 A method for inspecting a ship's cargo hold, comprising: a step of flowing liquid caustic soda onto the inner wall of a tank of a ship's cargo hold and collecting the flowing liquid caustic soda as a sample; and a step of inspecting for the presence or absence of a remaining amount of previous cargo in the ship's cargo hold by including at least one of a) a step of measuring the pH of the sample at room temperature; and b) a step of checking the turbidity of the sample. In the case where the previous cargo is a hydrocarbon-based substance, the method includes step b), wherein the turbidity of the sample is confirmed by comparing the turbidity of the sample with the following standard solutions A to D: Standard solution A = pure caustic soda; Standard solution B = pure caustic soda mixed with 1 ppm hydrocarbon; Standard solution C = pure caustic soda mixed with 5 ppm hydrocarbon; Standard solution D = pure caustic soda mixed with 10 ppm hydrocarbon. Claim 4 A ship cargo tank inspection method according to paragraph 3, wherein if the turbidity of the sample is higher than the turbidity of standard solution C, re-cleaning of the cargo tank is required. Claim 5 A method for inspecting a ship's cargo hold, wherein, in any one of paragraphs 1 to 4, the cargo loaded after inspecting the ship's cargo hold is liquid caustic soda. Claim 6 A method for inspecting a ship's cargo hold according to any one of claims 1 to 4, wherein the liquid caustic soda has a pH of 13 to 14 at room temperature. Claim 7 delete Claim 8 delete Claim 9 delete