JP4305061B2 - Device damage prevention method in hydraulic tank - Google Patents

Device damage prevention method in hydraulic tank Download PDF

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Publication number
JP4305061B2
JP4305061B2 JP2003153099A JP2003153099A JP4305061B2 JP 4305061 B2 JP4305061 B2 JP 4305061B2 JP 2003153099 A JP2003153099 A JP 2003153099A JP 2003153099 A JP2003153099 A JP 2003153099A JP 4305061 B2 JP4305061 B2 JP 4305061B2
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Prior art keywords
oil
hydraulic
tank
outside air
oil tank
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JP2004353779A (en
Inventor
義範 佐藤
満信 平石
謙二 松岡
省三 松田
誠一 山本
修平 安部
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JFE Steel Corp
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JFE Steel Corp
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【０００１】
【発明の属する技術分野】
本発明は、油圧機器の作動油を蓄えた油槽を備え、前記作動油を油圧機器に供給する油圧タンクに関するものである。
【０００２】
【従来の技術】
通常、油圧シリンダ等の油圧機器には油圧タンクが設けられている。油圧タンクは、油圧機器用の作動油を蓄えた油槽を備え、油圧機器の作動に応じて、油圧機器に作動油を送り出したり、油圧機器から作動油を受け取ったりするようになっている。
【０００３】
図３は、従来の油圧タンクを示す断面図である。油圧タンクは、内部に油圧機器用の作動油１２を蓄え、ほぼ密閉された構造の油槽１１と、油槽１１から油圧機器（図示せず）に作動油１２を送り出すための行き配管１３と、油圧機器から油槽１１に作動油１２を受け取るための戻り配管１４とを備えている。そして、油圧機器の作動に応じて作動油１２を送り出したり、作動油１２を受け取ったりすることにより、油槽１１内の作動油１２の油面１２ａが上下するので、その際の油槽１１内の圧力変動に対応するために、油槽１１内の油面１２ａ上部の閉鎖空間１５を外気と連通させる通気口２１が油槽１１の上部に設けられている。
【０００４】
したがって、このような従来の油圧タンクにおいては、外気が通気口２１を経由して油槽１１内への侵入と吐出を繰り返すことになり、油圧タンク周辺の外気が水分や粉塵等の異物を含んでいる場合、この外気の侵入によって油槽１１内の作動油１２に水分や異物が混入する。その結果、以下のような問題が発生する。
【０００５】
すなわち、作動油１２に多量の水分が混入した場合、作動油１２の乳化が発生する。乳化した作動油はサーボ弁等の油圧機器の内部部品に付着したり、フィルターの目詰まりを引き起こし、油圧機器の作動不良の原因となる。作動油１２に多量の異物が混入した場合も同様の結果となる。
【０００６】
また、乳化した作動油が油圧配管内に付着堆積した場合、フィルターの目詰まりが短期間で発生する。その都度フィルターを取替えるとフィルター取替費用が増大するし、油圧配管のフラッシングを行うと、補修費が増大する。
【０００７】
そこで、上記の問題に対応するために、油槽内の圧力変動を吸収できるような柔軟に変形する容器を油槽に取り付けることにより、油槽を外気と遮断した構造の油圧タンクが提案されている（例えば、特許文献１参照。）。
【０００８】
図４は、上記特許文献１に示されている油圧タンクを説明するための断面図である。この油圧タンクにおいては、図３における通気口２１に代えて、油槽１１の上部外側に、風船等の柔軟に変形する容器２２が取り付けられており、油槽１１内の油面１２ａの上下による油槽１１内の圧力変動を、この容器２２の変形によって吸収するようになっている。これによって、油槽を外気に連通させなくとも油槽内の圧力変動に対応できるようにしている。
【０００９】
【特許文献１】
特開平７−１５１１０２号公報
【００１０】
【発明が解決しようとする課題】
しかし、上記特許文献１に示されている油圧タンクにおいては、風船等の柔軟に変形する容器によって油槽内の圧力変動を吸収するようにしていることから、容器自体の強度が機械的外力に対して不充分となる。そのため、容器に保護カバーを取り付けることが必要になり、保守点検等に手間が掛かる。逆に、容器の機械的強度を上げると、油槽内に急激な圧力変動が生じた場合、容器の変形が追従できずに油槽内の圧力変動を吸収できなくて、機器の損傷を招く危険性がある。
【００１１】
本発明は、上記の問題を解決するためになされたものであり、外気の侵入による油槽内の作動油への水分や異物の混入を防ぎながら油槽内の圧力変動に対応できるとともに、油槽内の急激な圧力変動にも適切に対応できる油圧タンクを提供することを目的とするものである。
【００１２】
【課題を解決するための手段】
上記の課題を解決するために、本発明は以下の特徴を有する。
【００１３】
［１］油圧機器の作動油を蓄えた油槽を備え、前記作動油を油圧機器に供給する油圧タンクにおける機器損傷防止方法であって、
前記油槽の外側に、一端が前記油槽の油面の上部の閉鎖空間に通じ、他端が大気に開放され、内部に前記作動油を収納した略Ｕ字状の外気遮断配管を備え、
前記油槽内に急激な圧力上昇があった場合には、前記外気遮断配管の内部の作動油が大気に飛び出して油槽を大気と連通させ、
前記油槽内に急激な圧力低下があった場合には、前記外気遮断配管の内部の作動油が前記油槽内に飛び込んで油槽を大気と連通させることを特徴とする油圧タンクにおける機器損傷防止方法。
【００１４】
［２］前記油槽内の上限圧力Ｐ Tcr を設定し、前記外気遮断配管内の作動油の油槽側と大気側との液面差が以下の式で算出される限界液面差Δｈ cr となったときに、前記外気遮断配管内の作動油の液面が前記外気遮断配管の開放端高さを超えるようにすることを特徴とする前記［１］記載の油圧タンクにおける機器損傷防止方法。
Δｈ cr ＝（Ｐ Tcr −Ｐ A ）／（ρｇ）
Ｐ A ：大気圧、ρ：作動油の密度、ｇ：重力加速度
【００１５】
【発明の実施の形態】
図１は、本発明の一実施形態に係る油圧タンクを示す断面図である。この実施形態に係る油圧タンクは、内部に油圧機器用の作動油１２を蓄え、ほぼ密閉された構造の油槽１１と、油槽１１から油圧機器（図示せず）に作動油１２を送り出すための行き配管１３と、油圧機器から油槽１１に作動油１２を受け取るための戻り配管１４と、一端が油槽１１の油面１２ａの上部の閉鎖空間１５に通じ、他端が大気に開放され、内部に液体１９を収納した略Ｕ字状の外気遮断配管１８（一種のＵ字管マノメータ）とを備えている。
【００１６】
上記のような構造の油圧タンクにおいては、油槽１１への作動油１２の出入りに伴う油面１２ａの上下によって油面１２ａの上部の閉鎖空間１５の容積が変化し、油槽１１内の圧力が変動すると、その圧力変動は、閉鎖空間１５に通じている外気遮断配管１８の内部の液体１９の移動によって補われる。
【００１７】
例えば、油面１２ａが上昇して油槽１１内の圧力が上昇すると、図２に示すように、外気遮断配管１８の油槽１１側の液面が低下し、大気側の液面が上昇する。その際、油槽１１内の圧力ＰTと外気遮断配管１８内の液面差Δｈとの関係は、外気遮断配管１８の管径を均一とすると、Ｕ字管マノメータの原理から以下のように表される。
【００１８】
ＰT−ＰA＝ρｇΔｈ ……（１）
ここで、ＰAは大気圧、ρは液体１９の密度、ｇは重力加速度である。
【００１９】
このようにして、外気遮断配管１８内の液体１９の移動によって、油槽１１を外気と遮断しながら、油面１２ａの変位による油槽１１内の圧力変動を吸収することができる。
【００２０】
しかも、液体の配管内の移動によって圧力変動を吸収しているので、前記特許文献１のように容器の変形によって圧力変動を吸収するものに比べても、その応答速度（圧力感度）は一層良好である。
【００２１】
さらに、外気遮断配管１８自体が変形する訳ではないので、機械的外力に対して不充分な強度のものを用いて、そのための保護カバーを取り付ける必要もなく、構造上も簡易であり、保守点検は容易である。
【００２２】
そして、油槽１１内に急激な圧力上昇があった場合には、外気遮断配管１８の内部の液体１９が外気遮断配管１８の開放端１８ａから大気に飛び出して、油槽１１を大気と連通させるようになるので、機器の損傷を防止できる。また、油槽内に急激な圧力低下があった場合にも、外気遮断配管１８の内部の液体１９が外気遮断配管１８から油槽１１内に飛び込んで、油槽１１を大気と連通させるようになるので、機器の損傷を防止できる。その際、外気遮断配管１８の液体１９として、油槽１１内の作動油１２と同じものを用いていれば、液体１９が油槽１１内の作動油１２に混ざっても支障がない。
【００２３】
なお、油槽１１内の圧力ＰTが所定の上限圧力に達したときに、外気遮断配管１８内の液体１９が大気に飛び出して油槽１１を大気と連通させるように設定するには、以下のようにすればよい。
【００２４】
すなわち、前記（１）式から、
Δｈ＝（ＰT−ＰA）／（ρｇ） ……（２）
となるので、油槽１１内の圧力ＰTが所定の上限圧力ＰTcrに達したときの限界液面差Δｈcrは、
Δｈcr＝（ＰTcr−ＰA）／（ρｇ） ……（３）
となる。
【００２５】
したがって、（３）式によって算出される限界液面差Δｈcrが生じたときに液体１９の液面が開放端１８ａを越えるように、外気遮断配管１８の高さを調整しておけばよい。これによって、油槽１１内の圧力ＰTが所定の上限圧力（遮断解除圧力）ＰTcrに達した外気遮断配管１８内の液体１９が大気に飛び出して油槽１１を大気と連通させることができる。
【００２６】
油槽１１内の圧力ＰTが所定の下限圧力に達したときに、外気遮断配管１８内の液体１９が油槽１１内に飛び込んで油槽１１を大気と連通させるように設定する場合も上記と同様に行えばよい。
【００２７】
このようにして、前記（３）式に基づいて、外気遮断配管１８の遮断解除圧力を精度良く設定することができる。これに対して、前記特許文献１のような容器の変形による場合には、その遮断解除圧力を適切に設定することは難しい。
【００２８】
上記のように、この実施形態に係る油圧タンクにおいては、油槽への外気の侵入を遮断しながら油槽内の圧力変動に対応することができるとともに、油槽内の急激な圧力変動にも適切に対応することができる。
【００２９】
【発明の効果】
本発明においては、内部に液体を収納した略Ｕ字状の外気遮断配管を油槽に取り付けているので、外気の侵入による油槽内の作動油への水分や異物の混入を防ぎながら油槽内の圧力変動に対応することができるとともに、油槽内の急激な圧力変動にも適切に対応することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態の説明図である。
【図２】本発明の一実施形態における作動状態の説明図である。
【図３】従来技術の説明図である。
【図４】他の従来技術の説明図である。
【符号の説明】
１１ 油槽
１２ 作動油
１２ａ 油面
１３ 行き配管
１４ 戻り配管
１５ 閉鎖空間
１８ 外気遮断配管
１８ａ 開放端
１９ 液体
２１ 通気口
２２ 容器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic tank that includes an oil tank that stores hydraulic oil for hydraulic equipment and supplies the hydraulic oil to the hydraulic equipment.
[0002]
[Prior art]
Normally, hydraulic equipment such as a hydraulic cylinder is provided with a hydraulic tank. The hydraulic tank includes an oil tank that stores hydraulic oil for hydraulic equipment, and sends hydraulic oil to the hydraulic equipment and receives hydraulic oil from the hydraulic equipment according to the operation of the hydraulic equipment.
[0003]
FIG. 3 is a cross-sectional view showing a conventional hydraulic tank. The hydraulic tank stores hydraulic oil 12 for hydraulic equipment therein, and has an oil tank 11 having a substantially sealed structure, an outgoing pipe 13 for sending the hydraulic oil 12 from the oil tank 11 to a hydraulic equipment (not shown), and hydraulic pressure A return pipe 14 for receiving the hydraulic oil 12 from the device to the oil tank 11 is provided. And since the oil surface 12a of the hydraulic oil 12 in the oil tank 11 goes up and down by sending out the hydraulic oil 12 according to the action | operation of hydraulic equipment or receiving the hydraulic oil 12, the pressure in the oil tank 11 in that case In order to cope with the fluctuation, a vent 21 for communicating the closed space 15 above the oil surface 12 a in the oil tank 11 with the outside air is provided in the upper part of the oil tank 11.
[0004]
Therefore, in such a conventional hydraulic tank, the outside air repeatedly enters and discharges into the oil tank 11 via the vent hole 21, and the outside air around the hydraulic tank contains foreign matters such as moisture and dust. If it is, moisture and foreign matter are mixed into the hydraulic oil 12 in the oil tank 11 due to the intrusion of the outside air. As a result, the following problems occur.
[0005]
That is, when a large amount of water is mixed in the hydraulic oil 12, the hydraulic oil 12 is emulsified. The emulsified hydraulic oil adheres to the internal parts of hydraulic equipment such as servo valves, and causes clogging of the filter, causing malfunction of the hydraulic equipment. The same result is obtained when a large amount of foreign matter is mixed in the hydraulic oil 12.
[0006]
Further, when the emulsified hydraulic oil adheres and accumulates in the hydraulic piping, the filter is clogged in a short period of time. If the filter is replaced each time, the cost for replacing the filter increases, and if the hydraulic piping is flushed, the repair cost increases.
[0007]
Therefore, in order to cope with the above problem, a hydraulic tank having a structure in which the oil tank is shut off from the outside air by attaching a flexible deformable container that can absorb the pressure fluctuation in the oil tank to the oil tank has been proposed (for example, , See Patent Document 1).
[0008]
FIG. 4 is a cross-sectional view for explaining the hydraulic tank shown in Patent Document 1. In this hydraulic tank, instead of the vent 21 in FIG. 3, a container 22 such as a balloon that is flexibly deformed is attached to the upper outer side of the oil tank 11. The internal pressure fluctuation is absorbed by the deformation of the container 22. This makes it possible to cope with pressure fluctuations in the oil tank without the oil tank communicating with the outside air.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-151102
[Problems to be solved by the invention]
However, in the hydraulic tank shown in Patent Document 1, since the pressure variation in the oil tank is absorbed by a flexible deformable container such as a balloon, the strength of the container itself is less than the mechanical external force. Is insufficient. For this reason, it is necessary to attach a protective cover to the container, which takes time for maintenance and inspection. On the contrary, if the mechanical strength of the container is increased, if a sudden pressure fluctuation occurs in the oil tank, the deformation of the container cannot follow and the pressure fluctuation in the oil tank cannot be absorbed, resulting in damage to the equipment. There is.
[0011]
The present invention has been made to solve the above-described problem, and can cope with pressure fluctuations in the oil tank while preventing moisture and foreign matter from being mixed into the hydraulic oil in the oil tank due to intrusion of outside air. An object of the present invention is to provide a hydraulic tank that can appropriately cope with sudden pressure fluctuations.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following features.
[0013]
[1] comprising a oil tank accumulated hydraulic oil in the hydraulic device, the hydraulic fluid A definitive to the hydraulic tank equipment damage prevention method for supplying the hydraulic equipment,
On the outside of the oil tank, one end leads to a closed space above the oil level of the oil tank, the other end is opened to the atmosphere, and includes a substantially U-shaped outside air shutoff pipe containing the hydraulic oil inside,
When there is a sudden pressure rise in the oil tank, the hydraulic oil inside the outside air shutoff pipe jumps out to the atmosphere and the oil tank communicates with the atmosphere.
Wherein when a sudden pressure drop in the oil tank, the instrument damage prevention method in the hydraulic tank hydraulic oil inside the outside air cutoff pipe and said Rukoto in communication with the atmosphere the oil vat jump in the oil vessel .
[0014]
[2] sets the upper limit pressure P Tcr in the oil tank, a said limit liquid level difference Delta] h cr the liquid level difference between the oil vessel side and the atmosphere side of the working oil outside air blocking the pipe is calculated by the following equation The apparatus for preventing damage to equipment in the hydraulic tank according to [1], wherein the level of hydraulic oil in the outside air shutoff pipe exceeds the open end height of the outside air shutoff pipe .
Δh cr = (P Tcr −P A ) / (ρg)
P A : atmospheric pressure, ρ: density of hydraulic oil, g: acceleration of gravity
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view showing a hydraulic tank according to an embodiment of the present invention. The hydraulic tank according to this embodiment stores hydraulic oil 12 for hydraulic equipment inside, and an oil tank 11 having a substantially sealed structure, and a route for sending the hydraulic oil 12 from the oil tank 11 to a hydraulic equipment (not shown). Pipe 13, return pipe 14 for receiving hydraulic oil 12 from hydraulic equipment to oil tank 11, one end leading to closed space 15 above oil surface 12 a of oil tank 11, the other end open to the atmosphere, and liquid inside 19 is a substantially U-shaped outside air shutoff pipe 18 (a kind of U-shaped manometer).
[0016]
In the hydraulic tank having the above-described structure, the volume of the closed space 15 above the oil surface 12a is changed by the up and down of the oil surface 12a as the hydraulic oil 12 enters and leaves the oil tank 11, and the pressure in the oil tank 11 varies. Then, the pressure fluctuation is compensated by the movement of the liquid 19 inside the outside air shutoff pipe 18 communicating with the closed space 15.
[0017]
For example, when the oil level 12a rises and the pressure in the oil tank 11 rises, as shown in FIG. 2, the liquid level on the oil tank 11 side of the outside air blocking pipe 18 decreases and the liquid level on the atmosphere side increases. At this time, the relationship between the pressure PT in the oil tank 11 and the liquid level difference Δh in the outside air shutoff pipe 18 is expressed as follows from the principle of the U-shaped manometer when the pipe diameter of the outside air shutoff pipe 18 is uniform. Is done.
[0018]
P T −P A = ρgΔh (1)
Here, P A is atmospheric pressure, ρ is the density of the liquid 19, and g is gravitational acceleration.
[0019]
In this way, the movement of the liquid 19 in the outside air blocking pipe 18 can absorb pressure fluctuations in the oil tank 11 due to the displacement of the oil surface 12a while blocking the oil tank 11 from the outside air.
[0020]
In addition, since the pressure fluctuation is absorbed by the movement of the liquid in the pipe, the response speed (pressure sensitivity) is even better than the one that absorbs the pressure fluctuation due to the deformation of the container as in Patent Document 1. It is.
[0021]
Furthermore, since the outside air shutoff pipe 18 itself is not deformed, it is not necessary to attach a protective cover for the mechanical external force that is insufficiently strong against mechanical external force, and it is simple in structure and maintenance inspection. Is easy.
[0022]
When there is a sudden pressure increase in the oil tank 11, the liquid 19 inside the outside air blocking pipe 18 jumps out to the atmosphere from the open end 18 a of the outside air blocking pipe 18 so that the oil tank 11 communicates with the atmosphere. Therefore, damage to the equipment can be prevented. In addition, even when there is a sudden pressure drop in the oil tank, the liquid 19 inside the outside air shutoff pipe 18 jumps into the oil tank 11 from the outside air shutoff pipe 18 so that the oil tank 11 communicates with the atmosphere. Damage to equipment can be prevented. At that time, if the same fluid 19 as the hydraulic oil 12 in the oil tank 11 is used as the liquid 19 in the outside air blocking pipe 18, there is no problem even if the liquid 19 is mixed with the hydraulic oil 12 in the oil tank 11.
[0023]
In addition, when the pressure P T in the oil tank 11 reaches a predetermined upper limit pressure, the liquid 19 in the outside air shutoff pipe 18 jumps out to the atmosphere so that the oil tank 11 communicates with the atmosphere as follows. You can do it.
[0024]
That is, from the equation (1),
Δh = (P T −P A ) / (ρg) (2)
Therefore, the limit liquid level difference Δh cr when the pressure P T in the oil tank 11 reaches a predetermined upper limit pressure P Tcr is
Δh cr = (P Tcr −P A ) / (ρg) (3)
It becomes.
[0025]
Therefore, the height of the outside air blocking pipe 18 may be adjusted so that the liquid level of the liquid 19 exceeds the open end 18a when the limit liquid level difference Δh cr calculated by the equation (3) is generated. As a result, the liquid 19 in the outside air blocking pipe 18 in which the pressure P T in the oil tank 11 has reached a predetermined upper limit pressure (blocking release pressure) P Tcr jumps out to the atmosphere, and the oil tank 11 can communicate with the atmosphere.
[0026]
When the pressure P T in the oil tank 11 reaches a predetermined lower limit pressure, the liquid 19 in the outside air shut-off pipe 18 jumps into the oil tank 11 so that the oil tank 11 communicates with the atmosphere. Just do it.
[0027]
In this way, the shut-off release pressure of the outside air shut-off pipe 18 can be set with high accuracy based on the formula (3). On the other hand, when the container is deformed as in Patent Document 1, it is difficult to appropriately set the cutoff release pressure.
[0028]
As described above, in the hydraulic tank according to this embodiment, it is possible to cope with pressure fluctuations in the oil tank while blocking intrusion of outside air into the oil tank, and appropriately cope with sudden pressure fluctuations in the oil tank. can do.
[0029]
【The invention's effect】
In the present invention, since a substantially U-shaped outside air shut-off pipe containing liquid inside is attached to the oil tank, the pressure in the oil tank is prevented while preventing moisture and foreign matter from entering the hydraulic oil in the oil tank due to intrusion of outside air. In addition to being able to cope with fluctuations, it is also possible to appropriately deal with sudden pressure fluctuations in the oil tank.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an operating state in an embodiment of the present invention.
FIG. 3 is an explanatory diagram of a prior art.
FIG. 4 is an explanatory diagram of another prior art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Oil tank 12 Hydraulic oil 12a Oil level 13 Outbound piping 14 Return piping 15 Closed space 18 Outside air shutoff piping 18a Open end 19 Liquid 21 Vent 22 Container

Claims (2)

油圧機器の作動油を蓄えた油槽を備え、前記作動油を油圧機器に供給する油圧タンクにおける機器損傷防止方法であって、
前記油槽の外側に、一端が前記油槽の油面の上部の閉鎖空間に通じ、他端が大気に開放され、内部に前記作動油を収納した略Ｕ字状の外気遮断配管を備え、
前記油槽内に急激な圧力上昇があった場合には、前記外気遮断配管の内部の作動油が大気に飛び出して油槽を大気と連通させ、
前記油槽内に急激な圧力低下があった場合には、前記外気遮断配管の内部の作動油が前記油槽内に飛び込んで油槽を大気と連通させることを特徴とする油圧タンクにおける機器損傷防止方法。Comprising a oil tank accumulated hydraulic oil in the hydraulic device, the hydraulic fluid A definitive to the hydraulic tank equipment damage prevention method for supplying the hydraulic equipment,
On the outside of the oil tank, one end leads to a closed space above the oil level of the oil tank, the other end is opened to the atmosphere, and includes a substantially U-shaped outside air shutoff pipe containing the hydraulic oil inside,
When there is a sudden pressure increase in the oil tank, the hydraulic oil inside the outside air shutoff pipe jumps out to the atmosphere and makes the oil tank communicate with the atmosphere.
Wherein when a sudden pressure drop in the oil tank, the instrument damage prevention method in the hydraulic tank hydraulic oil inside the outside air cutoff pipe and said Rukoto in communication with the atmosphere the oil vat jump in the oil vessel . 前記油槽内の上限圧力Ｐ Tcr を設定し、前記外気遮断配管内の作動油の油槽側と大気側との液面差が以下の式で算出される限界液面差Δｈ cr となったときに、前記外気遮断配管内の作動油の液面が前記外気遮断配管の開放端高さを超えるようにすることを特徴とする請求項１記載の油圧タンクにおける機器損傷防止方法。
Δｈ cr ＝（Ｐ Tcr −Ｐ A ）／（ρｇ）
Ｐ A ：大気圧、ρ：作動油の密度、ｇ：重力加速度 Set the upper limit pressure P Tcr in the oil tank, when the liquid level difference between the oil vessel side and the atmosphere side of the working oil outside air blocking the pipe becomes the limit liquid level difference Delta] h cr calculated by the following formula 2. The method for preventing damage to equipment in a hydraulic tank according to claim 1, wherein the level of hydraulic oil in the outside air shutoff pipe exceeds the open end height of the outside air shutoff pipe .
Δh cr = (P Tcr −P A ) / (ρg)
P A : atmospheric pressure, ρ: density of hydraulic oil, g: acceleration of gravity
JP2003153099A 2003-05-29 2003-05-29 Device damage prevention method in hydraulic tank Expired - Fee Related JP4305061B2 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101835419B1 (en) * 2015-12-23 2018-03-09 임연홍 Apparatus and method for manufacturing hydrogen water

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101835419B1 (en) * 2015-12-23 2018-03-09 임연홍 Apparatus and method for manufacturing hydrogen water

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