Editorial Type:
Article
Article Type:
Research Article

Scheme Design and Pressure-Retaining Performance Analysis of Macrobiological Sampler in the Full-Ocean-Depth Operating Environment

Guangping Liu aNational-Local Joint Engineering Laboratory of Marine Mineral Resources Exploration Equipment and Safety Technology, Hunan University of Science and Technology, Xiangtan, Hunan, China

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Yongping Jin aNational-Local Joint Engineering Laboratory of Marine Mineral Resources Exploration Equipment and Safety Technology, Hunan University of Science and Technology, Xiangtan, Hunan, China

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Youduo Peng aNational-Local Joint Engineering Laboratory of Marine Mineral Resources Exploration Equipment and Safety Technology, Hunan University of Science and Technology, Xiangtan, Hunan, China

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Deshun Liu aNational-Local Joint Engineering Laboratory of Marine Mineral Resources Exploration Equipment and Safety Technology, Hunan University of Science and Technology, Xiangtan, Hunan, China

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Liang Liu aNational-Local Joint Engineering Laboratory of Marine Mineral Resources Exploration Equipment and Safety Technology, Hunan University of Science and Technology, Xiangtan, Hunan, China

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Online Publication:
16 Jan 2023
Print Publication:
01 Jan 2023
DOI:
https://doi.org/10.1175/JTECH-D-22-0062.1
Page(s):
85–97
Free access

Abstract

A new full-ocean-depth macroorganisms pressure-retaining sampler (FMPS) was designed to collect pressure-retaining macroorganisms samples from the abyssal seafloor. A mathematical model for pressure compensation in the FMPS recovery process was developed. The effects of FMPS structural parameters, pressure compensator structural parameters, and sampling environment on the pressure retention performance of FMPS were analyzed. Using the developed FMPS engineering prototype, FMPS internal pressure test, high-pressure chamber simulation sampling, and pressure-retaining test was carried out. The test results show that the key components of FMPS can carry 115 MPa pressure, FMPS can complete the sampling action in the high-pressure chamber of 115 MPa, the pressure is maintained at 105.5 MPa, and the pressure drop rate (ratio of pressure drop during FMPS recovery to sampling point pressure) is 9.13%; the experimental results are consistent with the theoretical calculation. The test verified the feasibility of FMPS design and the reliability of pressure retention, providing a theoretical basis and technical support for the design and manufacture of full-ocean-depth sampling devices.

© 2023 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Yongping Jin, jinyongping12@163.com\

Abstract

A new full-ocean-depth macroorganisms pressure-retaining sampler (FMPS) was designed to collect pressure-retaining macroorganisms samples from the abyssal seafloor. A mathematical model for pressure compensation in the FMPS recovery process was developed. The effects of FMPS structural parameters, pressure compensator structural parameters, and sampling environment on the pressure retention performance of FMPS were analyzed. Using the developed FMPS engineering prototype, FMPS internal pressure test, high-pressure chamber simulation sampling, and pressure-retaining test was carried out. The test results show that the key components of FMPS can carry 115 MPa pressure, FMPS can complete the sampling action in the high-pressure chamber of 115 MPa, the pressure is maintained at 105.5 MPa, and the pressure drop rate (ratio of pressure drop during FMPS recovery to sampling point pressure) is 9.13%; the experimental results are consistent with the theoretical calculation. The test verified the feasibility of FMPS design and the reliability of pressure retention, providing a theoretical basis and technical support for the design and manufacture of full-ocean-depth sampling devices.

© 2023 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Yongping Jin, jinyongping12@163.com\
Keywords: Ocean; Pressure; Numerical analysis/modeling; Field experiments

1. Introduction

Hadal trenches, found at depths exceeding 6000 m, represent only ∼0.21% of the volume but 45% of the depth range of the ocean (Fang et al. 2010). The hadal zone remains one of the least understood and most mysterious habitats on Earth. It is characterized by elevated hydrostatic pressure, cold temperature, low food availability, the absence of natural light, and relatively isolated hydrotopography (Nunoura et al. 2015; Ritchie et al. 2017). For a long time, the hadal zone was considered to be a biological desert, and knowledge of its biology, ecology, and biogeochemistry was very scarce as a result of its technological constraints (Luo et al. 2017). Despite being considered an “extreme” environment, the hadal zone is rich in macroorganism, microorganism, and gene resources. The study of biological communities, chemical circulation, and life processes is key to understanding the evolution of the hadal zone environment.

Countries around the world have made rapid development in deep-sea biological sampling technology. Macdonald et al. (1978) proposed a deep-sea macrobiotic pressure-maintaining sampler, which was sampled at a depth of 2700 m. The organisms were trapped by bait in the pressure-maintaining cylinder, and the recovery process compensated for the pressure by a pressure compensator, and the outer wall of the pressure-maintaining chamber was equipped with a heat insulation layer to keep the samples in a low-temperature environment. Yayanos (1978, 2009) proposed a deep-sea biological sampling system, which sampled at a depth of 10 900 m and was sealed by a spring–piston–counterweight mechanism. The system is also equipped with pressure compensators and insulation to achieve seafloor insulation and pressure retention sampling. Drazen et al. (2005) proposed a hyperbaric trap respirometer with a sampling depth of 4000 m. The system uses a hydraulic buffer cylinder to control the closing speed, thus reducing damage to the organisms, and the system is also equipped with transfer and culture devices. Shillito et al. (2008) developed a PERISCOP system for an active sampling of deep-sea organisms by a suction device followed by preservation by a pressure-maintaining recovery device, which successfully obtained a live fish at 2300 m water depth. Billings et al. (2017) developed a SyPRID deep-sea macroorganism sampler. This deep-sea macroorganism sampler operates at a water depth of 6000 m. The SyPRID deep-sea macroorganism sampler is a paired system with a tube-in-tube design for each deep-sea macroorganism sampler, with a total length of 3.11 m, a flared entrance, and a diameter of 0.71 m. It can perform two repetitions or two independent biological samplings. Peoples et al. (2019) developed a new lander system that is capable of sampling in a full ocean depth environment. The lander system has a modular design and instruments for collecting macrofauna and flora, water, taking video, images and a pressure-maintaining deep-sea microbial sampler can be deployed on the lander. Garel et al. (2019) developed a device for in situ samplings, enrichment, and transfer of deep-sea organisms at a sampling depth of 6000 m. The system installed the sampling device on a CTD turntable, opened the inlet valve for sampling by releasing the spring through a trigger, and was equipped with a pressure compensator to compensate for the pressure for its recovery process. Wang et al. (2022) proposed a motor-driven piston pressure-maintaining sampler; the sampling device traps a benthic macroorganism onto a piston by bait, then the piston is controlled by a motor into a deep-sea macroorganism sampler, and a pressure compensator compensates for the pressure loss during the recovery process. He et al. (2021) designed a new deep-sea microbial pressure-retaining sampler, which has an independent sampling device and pressure-retaining device, and uses a sampling tube to collect microorganisms and a pressure-retaining device to maintain the sample pressure, and the sampler is able to sample under full-ocean-depth environment. Wu et al. (2018) designed a new gas-tight pair sampler that uses two titanium bottles and a sampling valve to collect two samples at a time, and the sampler is capable of pressure-retaining sampling on the abyssal seafloor. X. Wang et al. (2020) introduced a new metal-sealed pressure-retaining sampler, which took samples through a titanium diaphragm valve and stored the samples using a flexible titanium foil bag, which collected pressure-retaining samples during the sea trial.

At present, the sampling depth of the deep-sea biological sampler developed at home and abroad is in the range of 2000–6000 m, its bearing pressure is less than 70 MPa, and the sampling target is mainly deep-sea microorganisms and biological larvae, and most of the samplers cannot transfer the samples after sampling is completed. Therefore, in this paper, a full-ocean-depth macroorganisms pressure-retaining sampler (FMPS) is designed, and the sampler can sample macroorganisms at 11 000 m of the seafloor. The FMPS is equipped with a pressure compensation device for sample pressure maintenance and a transfer mechanism and docking interface to the culture kettle for pressure drop–free transfer of collected samples.

After a brief introduction, the rest of the paper is organized as follows: Section 2 describes the structure and working principle of FMPS. Section 3 introduces the structure and principle of the flap seal valve used in FMPS and establishes a mathematical model of the pressure compensator compensation process. Section 4 analyzes the influence law of FMPS structure parameters, pressure compensator structure parameters, and sampling depth on pressure compensator pressure retention performance. In section 5, internal pressure test tests and high-pressure chamber simulation sampling tests were conducted on FMPS. The test results were consistent with the analysis results.

2. Structure and working principle of FMPS

a. Structure of the FMPS

The overall structure of FMPS is shown in Fig. 1. FMPS is mainly composed of a pressure-retaining cylinder, outlet and inlet sealing mechanism, pressure compensation mechanism, transfer mechanism, and bait replenishment mechanism. FMPS has the following features: 1) It can be carried on board landers and submersibles without external energy and power, can be sealed in one trigger, and is simple to operate. 2) Active pressure retaining of samples can be achieved. 3) All key components can carry 110 MPa pressure. 4) It can be docked with biological culture device to realize pressure drop–free transfer.

Fig. 1.
Fig. 1.

FMPS overall structure.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

The FMPS section view is shown in Fig. 2. The outlet and inlet sealing mechanism consists of the valve cover, valve body, and torsion spring. The valve cover can be driven by the torsion spring to achieve the opening and closing action, which is used to seal the outlet and inlet ends of FMPS. The pressure-retaining cylinder is used to keep the pressure on the collected deep-sea macroorganisms. The material of the pressure-retaining cylinder is TC4 titanium alloy, which has the characteristics of high strength, light quality, and corrosion resistance. The inlet end of the pressure-retaining cylinder is equipped with a nonreturn device, which has two functions: one is used to prevent biological escape during the sampling process, and the other is used to repel biological transfer. The pressure compensation mechanism consists of a piston, an end cap, and a high-pressure cylinder, which is precharged with a certain amount of nitrogen to compensate for the pressure drop in the recovery process of the pressure-retaining cylinder. The gear mechanism is used to control the opening and closing of the outlet sealing mechanism under ultrahigh pressure. The adjustment of pressure causes the rack and pinion lever to drive the rotation of the outlet valve cover to realize the transfer of biological samples by FMPS under ultra-high-pressure force. The transfer mechanism consists of a transfer handle, a transfer rod, and a gear. By turning the handle, the stopper is driven to move on the transfer rod, thus driving the transfer of organisms in the pressure retaining cylinder. The bait replenishment mechanism consists of an end cap, barrel, spring, piston, one-way valve, and one-way valve control lever. Through the spring driving the piston to squeeze the bait package, the bait flows from the one-way valve into the pressure-retaining barrel to realize the trapping and nutrient replenishment of deep-sea organisms. The FMPS is mounted on a support frame, with the length, width, and height of the support frame being 700 mm × 300 mm × 160 mm.

Fig. 2.
Fig. 2.

FMPS section view.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

b. Working principle of FMPS

The working principle of FMPS is shown in Fig. 3. FMPS captures macroorganisms in four processes: lowering, capturing, recovering, and transferring.

Fig. 3.
Fig. 3.

Working principle of FMPS.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

1) Lowering

The FMPS components are installed on the lander after integration. Before the lander is lowered, open the outlet and inlet flap seal valves and limit them by the trigger lever. The pressure compensator is precharged with a certain amount of nitrogen through the filling valve so that the piston is at the bottom of the pressure compensator. The bait package is placed on top of the bait tube piston, the check valve on the bait tube is opened by the trigger lever, and the spring is in compression. The trigger rods on the outlet and inlet flap seal valves and the bait barrel are connected to the load-bearing block via the trigger rope on the lander, as shown in Fig. 3a.

2) Capturing

During the lowering of the lander, the piston in the pressure compensator moves upward under the pressure of seawater until the pressure in the lower chamber of the piston equilibrates with the pressure in the upper chamber. The spring of the bait cartridge pushes the piston to move. When the sampling point is reached, the piston in the bait cylinder squeezes the bait package, which flows into the pressure-retaining cylinder through the one-way valve, thus trapping the bottom organisms, as shown in Fig. 3b.

3) Recovering

After the FMPS sampling is completed, the trigger rope is cut off by a command from the deck, which causes the trigger lever to cancel the restriction on the outlet and inlet flap seal valves, and the outlet and inlet flap seal valves are closed, while the check valve on the bait barrel is closed. FMPS recovery to the deck process, due to the reduction of external seawater pressure, the sampling cylinder barrel expansion deformation, at this time the pressure compensator will compensate for the pressure reduction inside the pressure-retaining cylinder due to the expansion deformation of the sampling cylinder, as shown in Fig. 3c.

4) Transferring

After the FMPS recovery deck, the FMPS outlet end is docked with the culture device, the gear mechanism is made to open the outlet flap seal valve by pressurization, and the transfer handle is turned so that the nonreturner drives the organisms in the pressure-retaining cylinder into the culture device to complete the transfer without pressure drop.

3. Pressure compensation model for FMPS

a. Flap sealing mechanism

This paper designs a flap sealing mechanism with inside-out sealing, the bonnet and the valve body adopt an eccentric design, and the sealing performance of the flap sealing valve is better when the eccentric angle is 10° as verified by an experiment (Liu et al. 2018). The structure of the flap seal valve is shown in Fig. 4. After the FMPS sampling is completed, the trigger rod cancels the restriction of the flap seal valve, and the valve cover is driven by the torsion spring to achieve the initial seal with the valve body. The sealing force between the valve cover and the valve body is calculated as follows:
Fa1=F0+Fc1−Fb1=F0+14πDc2P1′−14πDb2P2,
where F0 is the force of torsion spring, Fc1 is the pressure inside FMPS acting on the top of the bonnet, Fb1 is the environmental pressure acting on the bottom of the bonnet, Dc is the diameter of the top of the bonnet, Db is the diameter of the bottom of the bonnet (Dc > Db), P1′ is the pressure inside FMPS, and P2 is the environmental pressure. During the process of recycling FMPS to the deck, the environmental pressure P2 keeps decreasing the pressure difference inside and outside FMPS. The pressure difference gradually increases, the sealing force Fa1 between the valve cover and the valve body gradually increases, the better the sealing performance.
Fig. 4.
Fig. 4.

Flap sealing valve structure.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

After the HMPS recovery deck, it needs to be docked with the culture unit to complete the transfer. Therefore, in this paper, the outlet seal valve bonnet is improved, the end of the bonnet is designed to be gear-like, and the rack and pinion mechanism is used to realize the bonnet opening under the ultra-high-pressure force environment, to realize the transfer process. Figure 4a shows the outlet flap seal valve closed; at this time, the gear lever is in the rightmost position. When deep-sea biological samples need to be transferred, a pressurized pump is used to connect with the high-pressure pump interface, and the gear lever is moved to the left end by pressurization, which causes the valve cover to rotate and realize the transfer of samples without pressure drop. Figure 4b shows the open state of the outlet flap seal valve. The limit lever is used to limit the rotation of the gear lever and ensure the smooth movement of the gear lever.

b. Pressure compensation modeling

Due to the special high-pressure environmental conditions of the seafloor, the sampling process of FMPS must minimize the fluctuation of the external environmental pressure of macroorganisms and avoid the influence of external pressure changes on the life characteristics of macroorganisms. Therefore, a piston-type pressure compensator was designed to keep the pressure of the sample close to the in situ pressure. The operation of the pressure compensator is divided into three statuses, as shown in Fig. 5, and the three statuses of the pressure compensator are analyzed separately.

Fig. 5.
Fig. 5.

Pressure compensator working condition.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

Status 1: When the FMPS is prepared on deck, a certain amount of nitrogen is precharged to the pressure compensator, at which point the piston of the pressure compensator is in the left end position:
P0S1−F=Ma,
where P0 is the pressure compensator precharge pressure, F is the frictional force of the piston, M is the mass of the piston, and a is the acceleration of the piston.
Status 2: During the decentralization of the FMPS, the external ambient pressure increases and the seawater in the FMPS pushes the piston in the pressure compensator to the right. When the FMPS reaches the sampling point, the pressure at both ends of the piston is the same:
P1S1−F1=P0′S1,
where P1 is the pressure at the sampling point, P1 = ρgh, S1 is the area of the piston, and P0′ is the pressure at the sampling point when the pressure compensator is in place.
Status 3: During the FMPS recovery process, the external ambient pressure keeps decreasing, the high-pressure seawater inside the FMPS causes the pressure-retaining cylinder to expand and deform, and the nitrogen in the pressure compensator pushes the piston to the left to compensate for the pressure loss of the pressure-retaining cylinder volume collision:
P0″S1−F2=P1′S1,
ΔP=P1−P1′,
where P0″ is the pressure after pressure compensator compensation, P1′ is the pressure after FMPS compensation, and ΔP is the pressure drop during FMPS recovery.
Combining Eqs. (3)–(5), the pressure drop of FMPS is
ΔP=P0′−P0″+F1+F2S1.
When the pressure compensator works under high pressure, the nature of the gas inside the pressure compensator is obviously different from that of the gas in the ideal state (Huang et al. 2006). Calculated from Boyle’s law equation (S. Wang et al. 2020; Zhang et al. 2017),
P0V0T0Z(P0)=P0′V0′T0′Z(P0′)=P0″V0″T0″Z(P0″),
P0′=P0V0T0Z(P0)T0′Z(P0′)V0′=P0V0T0Z(P0)T0′Z(P0′)V0″−ΔV,
P0″=Z(P0″)T0′Z(P0′)P0′T0+Z(P0)ΔVP0V0.
Combining Eqs. (3)–(9), we obtain
ΔP=P0V0T0Z(P0)T0′Z(P0′)P0V0T0″P0″T0·Z(P0″)Z(P0)−ΔV−Z(P0″)T0′Z(P0′)P0′T0+Z(P0)ΔVP0V0+F1+F2S1,
where ΔVP1 is the effect of pressure on the volume of FMPS, ΔVt1 is the effect of temperature on the volume of FMPS, ΔVP0 is the effect of pressure on the volume of pressure compensator, ΔVt0 is the effect of temperature on the volume of pressure compensator, ΔV = ΔVP1 + ΔVP0 + ΔVt1 + ΔVt0. Since the ambient temperature before FMPS lowering and recovery completion are equal, T0=T0″, and the water temperature of deep seafloor remains basically the same, T0′=2°C.
The piston inside the pressure compensator is sealed by O-ring; the material of the O-ring is PTFE covered fluorine rubber; the movement friction of O-ring (Han et al. 2011)
F=fπDd1−μ0[0.2πeE+μ0(1+μ0)ΔP],
where f is the coefficient of friction between the O-ring and the pressure compensator, D is the outer diameter of the O-ring, d is the cross-sectional diameter of the O-ring, the Poisson’s ratio of the O-ring material μ0 = 0.49, e is the precompression rate of the O-ring, working in an ultra-high-pressure environment, 15% ≤ e ≤ 25%, and the modulus of elasticity of the O-ring material E = 7.84 × 106 MPa (Liu 2013).
In the recovery process of FMPS, the cylinder will produce radial and axial deformation under the pressure difference between inside and outside. According to the elastic strain theory, the cylinder radial deformation ΔμP and axial deformation ΔLP are expressed as follows (Liu et al. 2022):
ΔuP=Di2P1DiE(Dk2−Di2)[Di2(1−2μ)+Dk2(1+μ)],
ΔLP=r02P1L(1−2μ)E(ri2−r02),
δ=Di2{exp⁡[3nbP2σs(2−σs/σb)]−1},
ΔVP=π(r0+ΔuP)2(L+ΔLP)/4−πr02L/4,
where Di is the inner diameter of the cylinder, Dk is the outer diameter of the cylinder, L is the length of the cylinder, E is the modulus of elasticity of the cylinder material, μ is the Poisson’s ratio of the cylinder material, δ is the wall thickness of the cylinder, the yield strength of the cylinder material σs = 800 MPa, the tensile strength of the cylinder material σb = 980 MPa, P is the design pressure of the cylinder, the design pressure is taken as 1.5 times of the sampling point pressure, P = 1.5P1. The design safety factor is nb = 2.5. ΔVP is the change in volume of the cylinder caused by the pressure difference.
In the recovery process of FMPS, the cylinder will produce circumferential and axial deformation under the difference in internal and external temperature, and the cylinder circumferential deformation ΔCt and axial deformation ΔLt are expressed as (Wang et al. 2022)
ΔCt=α(πDiΔT),
ΔLt=α(LΔT),
ΔVt=(C+ΔCt)2(L+ΔLt)/4π−πDi2L/4,
where ΔT is the temperature difference between the inside and outside of the cylinder, C is the circumference of the cylinder, ΔVt is the volume change of the cylinder caused by the temperature difference and the linear expansion coefficient of the cylinder material α = 8.6 × 10−6.
The change in pressure inside the FMPS after deck retraction reflects the compensating capacity of the pressure compensator; therefore, the pressure drop rate εp is defined to quantify the pressure compensator compensation performance as follows:
εp=ΔPP1×100%.

According to the project technical requirements, the FMPS inlet inner diameter D1 ≥ 60 mm and length L1 ≥ 500 mm. Since there is a limit to the weight of the sampling equipment carried by the deep submersible, the inner diameter and length of the pressure compensator are as small as possible compared to the value of the deep-sea macrobiotic pressure-holding sampler. The precharge gas pressure is usually set to 10%–20% of the sampling point pressure before the deep-sea sampler is decentralized, and the precharge nitrogen pressure is set to 10–30 MPa in this paper. The specific range of each parameter value is shown in Table 1.

Table 1

Parameters for simulation.
Table 1

4. Analysis of the pressure-retaining performance of FMPS

a. Influence of FMPS structural parameters

The effect of the inner diameter of FMPS on the pressure drop rate is shown in Fig. 6a. When the pressure compensator precharge pressure is certain, the larger the radius of FMPS, the smaller the pressure drop rate of FMPS. When the precharge pressure is 40 MPa, the pressure drop rate of FMPS with an inner diameter of 80 mm is 5.60%, which is 1.74% lower than that of FMPS with an inner diameter of 60 mm. When the inner diameter of FMPS is certain, the greater the pressure compensator precharge pressure, the smaller the pressure drop rate of FMPS. When the inner diameter of FMPS is 80 mm and the pressure compensator precharge pressure is 10 MPa, the pressure drop rate of FMPS is 8.91%, which is 3.31% more than when the precharge pressure is 40 MPa. The effect of the length of FMPS on the pressure drop rate is shown in Fig. 6b. When the pressure compensator precharge pressure is certain, the longer the length of FMPS, the smaller the pressure drop rate of FMPS. When the precharge pressure is 40 MPa, the pressure drop rate of FMPS length of 1000 mm is 6.34%, which is 1.66% lower than that of FMPS length of 500 mm. When the length of FMPS is certain, the higher the precharge pressure of the pressure compensator, the smaller the pressure drop rate of FMPS. For 1000 mm length of FMPS, when the precharge pressure of the pressure compensator is 10 MPa, the pressure drop rate of FMPS is 9.10%, which is 2.76% higher than the precharge pressure of 40 MPa. The precharge pressure of the pressure compensator has a more obvious effect on the pressure drop rate than the structural parameters of FMPS. When the cylinder is subjected to the action of the internal and external pressure difference, the cylinder will undergo expansion and deformation, and the pressure drop caused by the cylinder expansion and deformation is given by the formula
ΔP=ΔVPV×E1,
where ΔVP is the volume change of the cylinder caused by the pressure difference, V is the original volume of the cylinder, and E1 is the elastic modulus of seawater, E1 = 2.4 GPa. The larger the radius and length of FMPS, the smaller the deformation rate ΔVP/V under the action of the internal and external pressure difference of FMPS, and the smaller the pressure drop of FMPS, which is also consistent with the experimental results of Wang et al. (2022). The inner diameter and length of the FMPS should not be too large because of the weight limitation of the sampling equipment carried by the deep submersible on one dive. In this paper, FMPS with an inner diameter of 68 mm and a length of 760 mm was selected for test verification, and the test results are discussed in section 5.
Fig. 6.
Fig. 6.

Relationship between structural parameters of FMPS and pressure drop rate.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

b. Influence of pressure compensator structural parameters

The effect of pressure compensator inner diameter on pressure drop rate is shown in Fig. 7a. When the pressure compensator precharge pressure is certain, the larger the inner diameter of the pressure compensator, the larger the pressure drop rate of FMPS; when the precharge pressure is 40 MPa, the pressure drop rate of the pressure compensator inner diameter of 60 mm is 7.83%, which is 4.68% more than the pressure compensator inner diameter of 30 mm. When the inner diameter of the pressure compensator is larger than 50 mm, the larger the inner diameter of the pressure compensator, the smaller the change in the pressure drop rate of FMPS. When the pressure compensator inner diameter is certain, the greater the pressure compensator prefilling pressure, the smaller the pressure drop rate of FMPS. When the pressure compensator inner diameter is 60 mm and the pressure compensator prefilling pressure is 10 MPa, the pressure drop rate of FMPS is 9.43%, which is 1.60% more than when the prefilling pressure is 40 MPa. The effect of pressure compensator length on pressure drop rate is shown in Fig. 7b. When the pressure compensator precharge pressure is certain, the longer the length of the pressure compensator, the greater the pressure drop rate of FMPS. When the precharge pressure is 40 MPa, the pressure drop rate of FMPS with a length of 300 mm is 7.86%, which is 3.57% lower than that of FMPS with a length of 100 mm. When the length of the pressure compensator is certain, the greater the pressure compensator precharge pressure, the smaller the pressure drop rate of FMPS. For 300 mm length of FMPS, when the pressure compensator precharge pressure is 10 MPa, the pressure drop rate of FMPS is 9.48%, which is 1.62% more than when the precharge pressure is 40 MPa. When the length of the pressure compensator is greater than 220 mm, the longer the length of the pressure compensator, the smaller the change in the pressure drop rate of the FMPS. The structural parameters of the pressure compensator have a more obvious effect on the pressure drop rate than the pressure compensator precharge pressure. In this paper, a pressure compensator with an inner diameter of 50 mm and a length of 220 mm was selected for test verification, and the test results are discussed in section 5.

Fig. 7.
Fig. 7.

Relationship between pressure compensator structural parameters and pressure drop rate.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

The effect of the friction coefficient of the O-ring in the pressure compensator on the pressure drop rate is shown in Fig. 8a. When the pressure compensator precharge pressure is certain, the larger the O-ring friction coefficient, the larger the pressure drop rate. The effect of the precompression rate of the O-ring in the pressure compensator on the pressure drop rate is shown in Fig. 8b. When the pressure compensator precharge pressure is certain, the greater the O-ring precompression rate, the greater the FMPS pressure drop rate. As the O-ring friction coefficient, the greater the precompression rate, the greater the piston friction in the pressure compensator, the better the sealing performance, but the greater the piston friction, the poorer the compensation performance of the pressure compensator, the greater the pressure drop.

Fig. 8.
Fig. 8.

Relationship between piston parameters and pressure drop rate.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

c. Influence of FMPS sampling environment

The effect of FMPS operating depth on the pressure drop rate is shown in Fig. 9a. When the pressure compensator precharge pressure is certain, the deeper the FMPS operating depth, the greater the pressure drop rate. When the precharge pressure is 40 MPa, the pressure drop rate for an FMPS operating depth of 11 000 m is 7.12%, which is 1.67% more than when the FMPS operating depth is 6000 mm. The deeper the FMPS operating depth, the greater the pressure difference between the inside and outside of the FMPS, the more pronounced the expansion and deformation of the FMPS and, therefore, the smaller the pressure drop rate of the FMPS. The effect of FMPS recovery to deck temperature on the pressure drop rate is shown in Fig. 7b. When the pressure compensator precharge pressure is certain, the temperature at the sampling point is set to 2°C. The higher the temperature difference between the inside and outside of the FMPS, the greater the FMPS pressure drop rate. When the precharge pressure is 40 MPa, the pressure drop rate at a deck temperature of 40°C is 9.48%, which is 6.12% lower than when the deck temperature is 20°C. The higher the pressure compensator precharge pressure, the lower the pressure drop rate of FMPS for a certain deck temperature. At a deck temperature of 40°C and a pressure compensator precharge pressure of 10 MPa, the FMPS pressure drop rate was 11.61%, an increase of 2.13% over the precharge pressure of 40 MPa. The effect of FMPS recovery to deck temperature on the pressure drop rate is more pronounced than the effect of pressure compensator precharge pressure, so after FMPS recovery to the deck, it should be immediately transferred to a refrigerated room to cool down.

Fig. 9.
Fig. 9.

Environment vs pressure drop rate for FMPS sampling.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

5. Experiments

a. Internal pressure test

Internal pressure tests were conducted in the laboratory to test the pressure retention performance of FMPS at an internal pressure of 115 MPa (working pressure), as shown in Fig. 10a. First, open the outlet and inlet flap sealing valves, put the FMPS into a water-filled tank, and extract the air inside the FMPS through a syringe. Then pull the outlet and inlet trigger lever to close the outlet and inlet flap seal valves. Use the pressurized pump to connect the pressurized valve of FMPS and conduct the internal pressure test. We first increased the pressure to 10% of the maximum test pressure, and after ensuring that no leaks occurred, we gradually increased the working pressure by 10% each time, holding each pressure gradient for 1 min and stopping when the maximum test pressure was reached, and the pressure gauge values are shown in Fig. 10b. The pressure was held at the maximum test pressure for 4 h (taking into account the time used for the recovery of FMPS from the seafloor at 11 000 m to the deck, disassembly, and transfer), and the pressure gauge values were observed as shown in Fig. 10c. Finally, start unloading and gradually reduce the maximum test pressure by 10% each time, holding each pressure gradient for 1 min and stopping when the pressure drops to zero. The same tests were conducted at 110 MPa (design pressure) and 127 MPa (1.15 times the design pressure), and the test results are shown in Table 2. The test results show that the FMPS as a whole can meet the requirements of ultra-high-pressure bearing, and with the increase of test pressure, the pressure drop of the all-seas deep macrobiological pressure-holding sampler is lower, which also verifies the rationality of the design of the flap sealing mechanism.

Fig. 10.
Fig. 10.

Internal pressure test of FMPS.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

Table 2

Results of internal pressure test.
Table 2

b. High-pressure chamber test

To verify the pressure retention performance of FMPS in an ultra-high-pressure environment, we conducted a simulated sampling test in a high-pressure chamber. A device capable of completing the FMPS sampling action under ultra-high-pressure force was designed, as shown in Fig. 11, which realizes the FMPS triggering action by the reciprocating motion of the hydraulic cylinder. The steps of the high-pressure chamber simulation sampling experiment are as follows: 1) First, fix the FMPS on the bracket, open the outlet and inlet flap seal valves, and lock them by the trigger lever. Three hydraulic cylinders on the bracket control the triggering action of the FMPS, respectively, and the hydraulic cylinders are connected to the pressurization system through a high-pressure pipe (as in Fig. 13a). 2) With compressed air as the driving power source and a gas booster pump as the pressure source, the air is used as the pressurized medium, and the pressure compensator is precharged with 30 MPa nitrogen through the gas booster pump, as shown in Fig. 12. 3) Put the FMPS into the high-pressure chamber together with the bracket, close the high-pressure chamber end cover, and pump the water into the high-pressure test chamber through the connected high-pressure pump station until the required water depth pressure is reached, as in Fig. 13b. 4) The pressurization system is used to pressurize the three hydraulic cylinders to trigger the three trigger rods of FMPS to complete the closing of the outlet and inlet flap seal valves and the bait cartridge check valve to simulate the sampling action of FMPS on the seabed. 5) After the sampling action is completed, hold the pressure for half an hour, open the outlet of the high-pressure chamber, and slowly release the water pressure inside the high-pressure chamber until it is equal to atmospheric pressure. 6) The FMPS was recovered to the laboratory, and the pressure value inside the full-seas depth macrobiocontainment FMPS was measured by a pressure gauge, as shown in Fig. 13c. The test results show that the FMPS can complete the sampling action under an ultra-high-pressure environment, and the pressure inside the FMPS is 105.5 MPa, the pressure drop rate is 9.13%, and the theoretical calculation value is 8.56%; the theoretical calculation and the test results are basically consistent.

Fig. 11.
Fig. 11.

High-pressure chamber test principle of FMPS.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

Fig. 12.
Fig. 12.

Precharge pressure test of FMPS.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

Fig. 13.
Fig. 13.

High-pressure chamber test for FMPS.

Citation: Journal of Atmospheric and Oceanic Technology 40, 1; 10.1175/JTECH-D-22-0062.1

6. Conclusions

In this study, a full-ocean-depth macroorganisms sampler with a pressure-retaining function is designed, which can realize the sampling of deep-sea macroorganisms under 11 000 m of the seafloor. The FMPS integrates a pressure compensation mechanism, a bait replenishment mechanism, and a sample transfer mechanism. FMPS can be operated on board landers and submersibles without external energy or power, with a single trigger for sealing, simple operation, and no pressure drop transfer of samples. We established a mathematical model of pressure compensation in the FMPS recovery process, analyzed the influence of different parameters on pressure compensator pressure retention performance, and conducted experimental verification. The major results of this study are as follows:

  1. At the same precharge pressure, the larger the inner diameter of FMPS, the smaller the pressure drop rate of FMPS, the longer the length of FMPS, and the smaller the pressure drop rate of FMPS. When the inner diameter and length of FMPS are certain, the larger the precharge pressure of the pressure compensator, the smaller the pressure drop rate of FMPS. Pressure compensator precharge pressure on the pressure drop rate is more obvious than the influence of FMPS structural parameters.

  2. Under the same precharge pressure, the larger the inner diameter of the pressure compensator, the larger the pressure drop rate of FMPS, the longer the length of the pressure compensator, and the larger the pressure drop rate of FMPS. The larger the friction coefficient and precompression rate of the O-ring inside the pressure compensator, the larger the pressure drop rate of FMPS. The structural parameters of the pressure compensator have a more obvious influence on the pressure drop rate of FMPS, and the parameters of the O-ring seal inside the pressure compensator have less influence on the pressure drop rate.

  3. Under the same precharge pressure, the deeper the FMPS operation depth, the greater the pressure difference between inside and outside FMPS, and the greater the expansion and deformation of the FMPS barrel, so the greater the FMPS pressure drop rate. The greater the temperature difference between inside and outside FMPS, the more obvious the change in FMPS pressure drop rate; therefore, in the FMPS recovery deck plate process, controlling the temperature difference between inside and outside FMPS can reduce the pressure drop rate; after recovery to the deck, it should be transferred as soon as possible to cold storage room.

  4. We carried out FMPS internal pressure tests using the developed FMPS engineering prototype, and the test results showed that the FMPS as a whole can meet the 110 MPa load capacity, and the higher the test pressure, the less the pressure drop of the FMPS. When the FMPS test pressure was 127 MPa, the pressure drop of the sampler was 0.39%.

  5. We designed a set of devices capable of completing FMPS sampling action under ultra-high-pressure force and carried out an FMPS high-pressure chamber simulation sampling test; the test results show that FMPS is capable of performing each sampling action under a 115 MPa pressure environment with good sealing performance. The test results show that the FMPS can complete each sampling action under the pressure environment of 115 MPa. The pressure at the time of FMPS recovery to the laboratory is 104.5 MPa, the pressure drop rate is 9.13%, and the theoretical calculation value is 8.56%; the theoretical calculation and test results are basically consistent.

Acknowledgments.

This work was supported by the National Key Research and Development Program of China Grant 2022YFC2805904) and Postgraduate Scientific Research Innovation Project of Hunan Province (Grant CX20210985). It was also supported by Special project for the construction of innovative provinces in Hunan (Grant 2020GK1021) and Special project for the construction of innovative city in Xiangtan (Grant ZX-ZD20221005).

Data availability statement.

No datasets were generated or analyzed during the current study.

REFERENCES

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    • Export Citation

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    • Search Google Scholar
    • Export Citation

  • Wang, H., D.-R. Ruan, C. Cao, J.-S. Fang, P. Zhou, Y.-P. Fang, and J.-W. Chen, 2022: Collection sediment from Mariana Trench with a novel pressure-retaining sampler. Deep-Sea Res. I, 183, 103740, https://doi.org/10.1016/j.dsr.2022.103740.

    • Search Google Scholar
    • Export Citation

  • Wang, S., S. Wu, and C. Yang, 2020: The pressure compensation technology of deep-sea sampling based on the real gas state equation. Acta Oceanol. Sin., 39, 88–95, https://doi.org/10.1007/s13131-020-1637-6.

    • Search Google Scholar
    • Export Citation

  • Wang, X., S.-J. Wu, Z.-F. Fang, C.-J. Yang, and S. Wang, 2020: A pressure-tight sampler with flexible titanium bag for deep-sea hydrothermal fluid samples. J. Atmos. Oceanic Technol., 37, 2065–2073, https://doi.org/10.1175/JTECH-D-20-0017.1.

    • Search Google Scholar
    • Export Citation

  • Wu, S. J., S. Wang, and C. J. Yang, 2018: Collection of gas-tight water samples from the bottom of the Challenger Deep. J. Atmos. Oceanic Technol., 35, 837–844, https://doi.org/10.1175/JTECH-D-17-0170.1.

    • Search Google Scholar
    • Export Citation

  • Yayanos, A. A., 1978: Recovery and maintenance of live amphipods at a pressure of 580 bars from an ocean depth of 5700 meters. Science, 200, 1056–1059, https://doi.org/10.1126/science.200.4345.1056.

    • Search Google Scholar
    • Export Citation

  • Yayanos, A. A., 2009: Recovery of live amphipods at over 102 MPa from the challenger deep. Mar. Technol. Soc. J., 43, 132–136, https://doi.org/10.4031/MTSJ.43.5.20.

    • Search Google Scholar
    • Export Citation

  • Zhang, L., L. Yang, J. Wang, J. Zhao, H. Dong, M. Yang, Y. Liu, and Y. Song, 2017: Enhanced CH4 recovery and CO2 storage via thermal stimulation in the CH4/CO2 replacement of methane hydrate. Chem. Eng. J., 308, 40–49, https://doi.org/10.1016/j.cej.2016.09.047.

    • Search Google Scholar
    • Export Citation
Save
Cover Journal of Atmospheric and Oceanic Technology
Journal of Atmospheric and Oceanic Technology

  • Billings, A., C. Kaiser, C. M. Young, L. S. Hiebert, E. Cole, J. K. S. Wagner, and C. L. Van Dover, 2017: SyPRID sampler: A large-volume, high-resolution, autonomous, deep-ocean precision plankton sampling system. Deep-Sea Res. II, 137, 297–306, https://doi.org/10.1016/j.dsr2.2016.05.007.

    • Search Google Scholar
    • Export Citation

  • Drazen, J. C., L. E. Bird, and J. P. Barry, 2005: Development of a hyperbaric trap‐respirometer for the capture and maintenance of live deep‐sea organisms. Limnol. Oceanogr. Methods, 3, 488–498, https://doi.org/10.4319/lom.2005.3.488.

    • Search Google Scholar
    • Export Citation

  • Fang, J., L. Zhang, and D. A. Bazylinski, 2010: Deep-sea piezosphere and piezophiles: Geomicrobiology and biogeochemistry. Trends Microbiol., 18, 413–422, https://doi.org/10.1016/j.tim.2010.06.006.

    • Search Google Scholar
    • Export Citation

  • Garel, M., P. Bonin, S. Martini, S. Guasco, M. Roumagnac, N. Bhairy, F. Armougom, and C. Tamburini, 2019: Pressure-retaining sampler and high-pressure systems to study deep-sea microbes under in situ conditions. Front. Microbiol., 10, 453, https://doi.org/10.3389/fmicb.2019.00453.

    • Search Google Scholar
    • Export Citation

  • Han, C. J., D. B. Li, and Y. Liu, 2011: The strength and sealing analysis of high pressure ball valve for natural gas. Adv. Mater. Res., 233–235, 2816–2819, https://doi.org/10.4028/www.scientific.net/AMR.233-235.2816.

    • Search Google Scholar
    • Export Citation

  • He, S., Y. Peng, Y. Jin, J. Yan, and B. Wan, 2021: Design and experimental study of a novel full-ocean-depth pressure-retaining sediment sampler. J. Atmos. Oceanic Technol., 38, 1715–1726, https://doi.org/10.1175/JTECH-D-20-0202.1.

    • Search Google Scholar
    • Export Citation

  • Huang, Z., S. Liu, and B. Jin, 2006: Accumulator-based deep-sea microbe gastight sampling technique. China Ocean Eng., 20, 335–342, https://doi.org/10.3321/j.issn:0890-5487.2006.02.013.

    • Search Google Scholar
    • Export Citation

  • Liu, G. P., Y. Jin, Y. Peng, and B. Wan, 2018: Multi-objective optimization design of flap sealing valve structure for deep sea sediment sampling. J. Vib. Test. Syst. Dyn., 2, 281–290, https://doi.org/10.5890/JVTSD.2018.09.008.

    • Search Google Scholar
    • Export Citation

  • Liu, G. P., and Coauthors, 2022: A deep-sea sediment sampling system: Design, analysis and experimental verification. J. Pressure Vessel Technol., 144, 021301, https://doi.org/10.1115/1.4051628.

    • Search Google Scholar
    • Export Citation

  • Liu, Z. D., 2013: Analysis on the Mechanical Properties of Piston Type Pressure Compensator in Deep Sea. Hefei University of Technology, 72 pp.

  • Luo, M., J. Gieskes, L. Chen, X. Shi, and D. Chen, 2017: Provenances, distribution, and accumulation of organic matter in the southern Mariana Trench rim and slope: Implication for carbon cycle and burial in hadal trenches. Mar. Geol., 386, 98–106, https://doi.org/10.1016/j.margeo.2017.02.012.

    • Search Google Scholar
    • Export Citation

  • Macdonald, A. G., and I. Gilchrist, 1978: Further studies on the pressure tolerance of deep-sea crustacea, with observations using a new high-pressure trap. Mar. Biol., 45, 9–21, https://doi.org/10.1007/BF00388973.

    • Search Google Scholar
    • Export Citation

  • Nunoura, T., and Coauthors, 2015: Hadal biosphere: Insight into the microbial ecosystem in the deepest ocean on Earth. Proc. Natl. Acad. Sci. USA, 112, E1230–E1236, https://doi.org/10.1073/pnas.1421816112.

    • Search Google Scholar
    • Export Citation

  • Peoples, L. M., and Coauthors, 2019: A full-ocean-depth rated modular lander and pressure-retaining sampler capable of collecting hadal-endemic microbes under in situ conditions. Deep-Sea Res. I, 143, 50–57, https://doi.org/10.1016/j.dsr.2018.11.010.

    • Search Google Scholar
    • Export Citation

  • Ritchie, H., A. J. Jamieson, and S. B. Piertney, 2017: Population genetic structure of two congeneric deep-sea amphipod species from geographically isolated hadal trenches in the Pacific Ocean. Deep-Sea Res. I, 119, 50–57, https://doi.org/10.1016/j.dsr.2016.11.006.

    • Search Google Scholar
    • Export Citation

  • Shillito, B., G. Hamel, C. Duchi, D. Cottin, J. Sarrazin, P.-M. Sarradin, J. Ravaux, and F. Gaill, 2008: Live capture of megafauna from 2300 m depth, using a newly designed pressurized recovery device. Deep-Sea Res. I, 55, 881–889, https://doi.org/10.1016/j.dsr.2008.03.010.

    • Search Google Scholar
    • Export Citation

  • Wang, H., D.-R. Ruan, C. Cao, J.-S. Fang, P. Zhou, Y.-P. Fang, and J.-W. Chen, 2022: Collection sediment from Mariana Trench with a novel pressure-retaining sampler. Deep-Sea Res. I, 183, 103740, https://doi.org/10.1016/j.dsr.2022.103740.

    • Search Google Scholar
    • Export Citation

  • Wang, S., S. Wu, and C. Yang, 2020: The pressure compensation technology of deep-sea sampling based on the real gas state equation. Acta Oceanol. Sin., 39, 88–95, https://doi.org/10.1007/s13131-020-1637-6.

    • Search Google Scholar
    • Export Citation

  • Wang, X., S.-J. Wu, Z.-F. Fang, C.-J. Yang, and S. Wang, 2020: A pressure-tight sampler with flexible titanium bag for deep-sea hydrothermal fluid samples. J. Atmos. Oceanic Technol., 37, 2065–2073, https://doi.org/10.1175/JTECH-D-20-0017.1.

    • Search Google Scholar
    • Export Citation

  • Wu, S. J., S. Wang, and C. J. Yang, 2018: Collection of gas-tight water samples from the bottom of the Challenger Deep. J. Atmos. Oceanic Technol., 35, 837–844, https://doi.org/10.1175/JTECH-D-17-0170.1.

    • Search Google Scholar
    • Export Citation

  • Yayanos, A. A., 1978: Recovery and maintenance of live amphipods at a pressure of 580 bars from an ocean depth of 5700 meters. Science, 200, 1056–1059, https://doi.org/10.1126/science.200.4345.1056.

    • Search Google Scholar
    • Export Citation

  • Yayanos, A. A., 2009: Recovery of live amphipods at over 102 MPa from the challenger deep. Mar. Technol. Soc. J., 43, 132–136, https://doi.org/10.4031/MTSJ.43.5.20.

    • Search Google Scholar
    • Export Citation

  • Zhang, L., L. Yang, J. Wang, J. Zhao, H. Dong, M. Yang, Y. Liu, and Y. Song, 2017: Enhanced CH4 recovery and CO2 storage via thermal stimulation in the CH4/CO2 replacement of methane hydrate. Chem. Eng. J., 308, 40–49, https://doi.org/10.1016/j.cej.2016.09.047.

    • Search Google Scholar
    • Export Citation
Fig. 1.

FMPS overall structure.
Fig. 2.

FMPS section view.
Fig. 3.

Working principle of FMPS.
Fig. 4.

Flap sealing valve structure.
Fig. 5.

Pressure compensator working condition.
Fig. 6.

Relationship between structural parameters of FMPS and pressure drop rate.
Fig. 7.

Relationship between pressure compensator structural parameters and pressure drop rate.
Fig. 8.

Relationship between piston parameters and pressure drop rate.
Fig. 9.

Environment vs pressure drop rate for FMPS sampling.
Fig. 10.

Internal pressure test of FMPS.
Fig. 11.

High-pressure chamber test principle of FMPS.
Fig. 12.

Precharge pressure test of FMPS.
Fig. 13.

High-pressure chamber test for FMPS.
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