Niskin water sampler
トピックアウトライン
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It consists of a water sampler made of polyvinyl chloride and a lid. The upper and lower lids are closed by the elasticity of a rubber tube or a metal spring (Figure 1). To remove the sample water from the water sampler, open the air vent at the top of the sampler and push in the water sampling port (PET cock) at the bottom of the sampler. The detailed structures of the upper and lower lids, the air vent, and the water sampling port (Pette cock) are shown in Figure 2. All of them are sealed with O-rings to prevent seawater from mixing with other seawater.
Fig. 1 Structure of Niskin water sampler
上蓋 Top Lid
採水筒 Water sampling bottle
ゴムチューブ(又はバネ) Rubber tube (or spring)
下蓋 Lower cover
空気孔(エアベント) Air vent
プッシュロッド Push rod
ワイヤクランプ Wire clamp
リリースブロック Release block
ナイロンテグス Nylon Tegs
採水口(ペットコック) Water sampling port (PET cock)
Fig. 2 Niskin water sampler Aperture mechanism
蓋 Lid
Oリング O-ring
空気孔 Air Hole
エアベントバルブ Air vent valve
空気 Air
採水口 Water sampling port
ガイドピン Guide pin
プルディスク Pull Disk
ペットコック Petcock
海水 Seawater
穴 Hole
ガイドピン Guide Pin
a) O-rings are fitted into the upper and lower openings of the water collection bottle, and the O-rings and the lid are sealed tightly together to maintain a tight seal. b) A screw-in valve (air vent valve) with a T-shaped hole is inserted into the air hole. When the valve is screwed in, the O-ring is crushed and the hole in the valve is blocked. Conversely, when the valve is loosened by twisting it, air enters the water sampling bottle. c) A T-shaped through-hole cock (petcock) is inserted into the water sampling port, and by sliding the cock back and forth, the water sampling port can be opened and closed. When the cock is pulled out, the hole is blocked by two O-rings. When the cock is pushed in, the hole is released and seawater flows out. The pull disk, which serves as a handle for sliding the cock, has a small hole in it, and this hole must be aligned with a metal rod (guide pin) protruding from the water sampling cylinder in order to push the cock in, making it difficult to accidentally release the cock.
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The water sampler with the lid open is attached to a wire rope, lowered to the desired depth, and then the lid is closed to collect the water ( Fig. 3 ).
Fig. 3 Niskin water sampler fixed to wire rope
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Setting up the water sampler
Before attaching the water sampler to the wire rope, leave the lid of the sampler open ( Fig. 4 and Fig. 5 ). Also, make sure that the water sampling port and air hole are closed.
Fig. 4 How to open the lid and set it on the trigger
上蓋 Upper Lid
下蓋 Lower Lid
プッシュロッド Push Rod
トリガーピン Trigger pin
スナップフック Snap hook
a) Open the top lid. Pass the tegus through the inside of the handle and secure the end of the tegus to the trigger pin. The trigger pin slides with the up-and-down movement of the push rod. b) Open the lower lid. Hook the snap hook at the end of the tegus onto the tegus on the upper lid. c) Set is complete.
Fig. 5 Notes on opening the lid
If a strong impact is applied when opening the lid, the edge of the water sampler may be chipped and the seal of the water sampler may be compromised. If the rubber (or spring) is pulled in the direction of extension (upward for the top lid) and then knocked down, the lid can be opened without applying impact.
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Attachment to the wire rope
Attach the water sampler to the wire rope, with the weight suspended and taut, using the fixture (clamp) provided on the back (Fig. 6).
Fig. 6 Fixing method to wire rope
ワイヤーロープ Wire Rope
蝶ナット Wing Nut
固定ブロック Fixing Block
クランプボルト Clamping Bolt
Fix the water sampler by fitting the wire rope into the groove of the clamp bolt and tightening the wing nut. Fix in two places in this order: upper part, then lower part.
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Closing of the lid
The lid is closed when a weight dropped along the wire rope strikes the trigger of the water sampler. The trigger mechanism of the Niskin water sampler is shown in Fig. 7. When the push rod is pushed down by the falling weight, the release pin slides downward, the nylon tegus fixed to the pin is released, and the lid is closed. The weight that actuates the trigger is called a messenger and has a closing mechanism that allows it to fall along the wire rope without falling off ( Fig. 8 ).
Fig. 7 Trigger mechanism of Niskin water sampler
ワイヤーロープ Wire Rope
プッシュロッド Push rod
ナイロンテグス(上蓋) Nylon tegs (upper lid)
リリースピン Release pins
ナイロンテグス(下蓋) Nylon tegs (lower lid)
Fig. 8 Messenger
a) Released state when attaching to or detaching from a wire rope. b) Closed state when dropping along the wire rope.
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Multi-layered water sampling by continuous installation
By attaching multiple water samplers to a wire rope at arbitrary intervals (chaining), multiple layers of seawater samples can be collected in a single observation (Figure 9). The trigger of the sampler has a release pin from which a messenger can be hung, and the messenger can be released toward the lower layer at the same time the lid of the sampler is closed when the trigger is activated. By attaching water samplers with messengers to wire ropes at desired intervals, the lid of the sampler can be closed from the top to the bottom in a relay-like fashion, simply by sending out a messenger from the vessel as the "first runner". In the example shown in Figure 9, three water samplers are placed at 100 m intervals, and if a messenger is dropped after the topmost sampler is submerged to 100 m, seawater at 100, 200, and 300 m can be sampled respectively.
Fig. 9 Multi-layer water sampling using a series of water samplers
水深 Depth
メッセンジャー Messenger
リリースピン解除 Lilly Spin Release
a) Attach multiple water samplers to the wire rope at desired intervals and lower them into the water. b) Each water sampler is left with its lid open and a messenger hanging from the trigger. c) When the messenger arrives from the upper layer, the lid of the water sampler closes, and at the same time the messenger begins to fall toward the lower layer.
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The CTD water sampling system is a combination of a wired CTD, a water sampling device, and a water sampler, allowing for accurate water sampling at the desired depth while recording and monitoring CTD readings in real time.
The water sampling device has multiple triggers arranged in a radial pattern, and the water samplers are arranged around the sampling device (also called a rosette-type sampling device because of its shape). Water can be collected from the same number of samplers at different depths in a single observation, or more seawater samples can be collected from the same layer by closing the lids of several samplers at the same depth.
Fig. 10 Configuration of CTD water sampling system and trigger mechanism of water sampling device
アーマードケーブル Armored Cable
多筒採水装置 Multi-tube water sampling equipment
ニスキン採水器 Niskin water sampler
保護フレーム Protective frames
採水器架台 Water sampler trestle
CDT水中局 CDT submersible station
Fig. 11 CTD water sampling system (12L Niskin X water sampler, 12 hangers) being put into the sea
CTD water sampling systems are available with 12, 24, or 36 samplers, depending on the number of samplers that can be equipped. The greater the number of samplers, the more layers and seawater can be sampled, but the number is limited by the capacity of the vessel's observation equipment, such as cranes and winches.
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Setting up the water sampler in a multi-tube sampler
As with the direct wire attachment method, open the lid of the water sampler before placing it in the sea. The tegus that secure the lid are set on the trigger of the multibarrel sampler, not on the trigger mechanism of the sampler itself (Fig. 12).
Fig. 12 Setting up the water sampling device
採水装置トリガー部拡大図 Enlarged view of water sampling device trigger section
スナップフック拡大図 Enlarged view of snap hook
a) Hook the end of the tegus connected to the upper lid onto the trigger of the water sampling device to secure the upper lid in the open position. b) Secure the lower lid in the open position by hooking the snap hook on the lower end of the lower lid's ring-shaped tegus, which has been branched off from the upper lid's tegus and extended downward.
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Niskin water samplers are constructed with a metal spring or rubber tubing placed inside the sampling cylinder. This structure may cause the seawater sample to come into contact with the spring or tubing, resulting in the elution of components into the seawater sample that may affect the seawater analysis value. The "External Spring Niskin Bottle," also known as the "Niskin X" water sampler, was developed to eliminate such contamination of seawater samples. The upper and lower lids of the Niskin X water sampler are connected by two springs placed on the outside of the sampling bottle and nylon threads, and the lid has an arm-like guide for threading the nylon threads ( Fig. 13 ). With this structure, there are no more springs or tubes in contact with the seawater sample inside the water sampler tube.
Fig. 13 Structure of Niskin X water sampler
蓋閉鎖バネ Lid closing spring
ナイロンテグス Nylon Tegs
ガイド Guide
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Niskin water samplers are used alone, attached to a wire rope or similar device, or integrated into a CTD water sampling system. If the water sampling tube has a rotating stand attached to it, a tipping thermometer* can be used to measure the depth and water temperature at the time of sampling ( Fig. 14 ).
Fig. 14 Operation of the tipping thermometer in the Niskin water sampler
a) Rotate the thermometer frame and turn it upside down, and secure it with a nylon teg. b) When the water sampling trigger is actuated, the nylon tegs are released and the thermometer frame rotates 180 degrees with the rotating stand by the elasticity of the rubber tube.
※ Tipping Thermometer
A special glass-mercury thermometer that, when tipped over, cuts the mercury bulb and the mercury column at the cutting point, and the length of the mercury column at the time of tipping over is preserved. By comparing the indicated values of the "protective pressure type" which is not subject to water pressure, and the indicated values of the "exposed to pressure type" which is subject to water pressure, the depth of water (or more precisely, water pressure) at the time of tipping over can be determined.
Fig. 15 Tipping Thermometer
主温度計 main thermometers
副温度計 secondary thermometers
防圧型 protective pressure type
被圧型 exposed to pressure type
転倒 tipping
死菅 dead pipe
切断点 cutting point
環状部 ringside
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