JPS6224081Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a storage tank for water-glycol hydraulic oil that is supplied to hydraulic equipment used under high heat. The present invention relates to a storage tank equipped with a mechanism capable of preventing various inconveniences (for example, development of ignitability, etc.) due to deterioration of the hydraulic oil. [Prior Art] Power medium fluids used in hydraulic systems are generally classified into petroleum-based hydraulic fluids and synthetic hydraulic fluids, with the former being generally used. These hydraulic fluids flow in hydraulic equipment while being affected by temperature, pressure, metals, contaminants, etc., so they have high oxidation stability, lubricity, viscosity characteristics, low-temperature fluidity, rust prevention, and demulsification. sex,
It must have excellent defoaming properties, etc. Therefore, there is a need to improve the properties of hydraulic oil, and efforts have been made to improve the oil itself and add additives.
Among these, the iron and steel manufacturing fields (including rolling and continuous casting),
For hydraulic oils used in high-temperature environments such as large-scale injection molding and forging presses, a new characteristic of flame retardancy has been added due to the need to protect equipment from fire. A new genre called oil is being formed. Although a wide variety of synthetic and aqueous types of flame-retardant hydraulic fluids are available, water-glycol-based hydraulic fluids are attracting attention because they do not have a so-called flash point. ing. Water-glycol hydraulic fluid is made by mixing various liquid glycols with water, but generally contains 35% to 45% ethylene glycol (or propylene glycol), polyglycol (as a thickener) 10 The composition of ~20% water, balance 34~40% (oil-based agent, liquid phase rust preventive agent, vapor phase rust preventive agent, antiwear agent, antifoaming agent, etc.) is prized. It goes without saying that the water-glycol hydraulic fluid referred to in this specification is not limited to the above composition example, and may include all water-glycol hydraulic fluids that are known (or commercially available) or that will be developed in the future.
It includes all glycol-based hydraulic fluids and is not excluded by changing the composition of the third component. [Problems to be solved by the invention] By the way, the boiling points of each component constituting such a water-glycol hydraulic fluid are water (100℃), ethylene glycol (197℃), and propylene glycol (188℃).
~189℃), which is one of the lowest boiling points of water. Therefore, if the device is used for a long time in a high temperature environment as described above, the water will eventually evaporate due to the high temperature of the operating conditions. When water evaporates, the ratio of ethylene glycol, propylene glycol, etc. increases relatively,
Things that were originally flame retardant are now becoming flammable. However, because we have established a relatively lenient fire prevention system based on the assumption that it is inherently flame retardant, workers may become flammable without knowing it, resulting in a lack of awareness. This means that they were in a fire prevention mode, so the risk level is extremely high. Therefore, it is necessary to analyze and monitor the amount of water lost at the appropriate time (much more frequently than when using general petroleum-based hydraulic fluid), and replenish distilled water as necessary. This invites outside air to get mixed in and causes rust, which will be discussed later. Also, vapor-phase rust inhibitors are also affected by high temperatures and are quickly dissipated into the open atmosphere, so rust may develop in the parts of the oil tank that come into contact with the atmosphere. Anti-corrosion measures such as forming with suitable materials are becoming necessary. Furthermore, although a liquid-phase rust preventive agent is used, the warm air inside the tank mixes into the hydraulic oil and is subjected to a violent agitation action, so not only the tank but also the pump, actuator, various control valves, etc. are damaged from the inside. There is also the problem of oxidation. The present invention has been developed with attention to these circumstances, and has adopted a configuration that allows the oxidation of the equipment to be suppressed to a necessary and sufficient degree even when water-glycol hydraulic oil is used in a high-temperature environment. It is intended to provide a storage tank. [Means for solving the problem] The storage tank according to the present invention has a structure that exhibits airtightness with a closed lid, and the gas phase side wall of the tank is equipped with a pressure retaining function inside the tank. The gist is that an exhaust device is attached and an inert gas injection device is attached, and on the other hand, an outlet and an inlet for the hydraulic oil are provided on the liquid phase side wall surface of the tank. [Function] Of the above-mentioned configurations adopted in the tank of the present invention, the provision of an airtight lid and the provision of an inert gas injection mechanism are similar to known techniques that appear to be similar at first glance, as described below. exist. In other words, when using conventional hydraulic equipment in facilities that generate a large amount of dust, or when using equipment that requires extremely high cleanliness characteristics such as servo valves, it is necessary to prevent foreign substances such as dust from entering. In order to maintain the suction performance of the pump in the hydraulic system, a lid has been installed on the oil tank, and nitrogen gas has also been introduced into the tank. Alternatively, a technique is known in which air pressure is applied above the oil surface for the purpose of preventing cavitation of the pump. However, the latter technique uses air and does not involve pressurizing inert gas. Alternatively, it is also known to use pressurized nitrogen gas to inject insulating oil into other parts of equipment. However, when using water-containing hydraulic fluids (in addition to the above-mentioned water-glycol type, W/O emulsion type, O/W emulsion type, etc.), the dynamics of the oxidation reaction should be considered as described above before introducing an inert gas. There are no examples of such maintenance measures being implemented yet, and of course, there are no examples of qualitatively or quantitatively recognizing their effects. This invention takes into account the following situations: ``Fire prevention in a high-temperature environment → Adoption of water-glycol hydraulic fluid → Deterioration of the hydraulic fluid and rusting of the tank itself'', and releases as much air as possible from inside the tank to operate the tank. This prevents oxidizing gas from coming into contact with the oil or the inner surface of the tank. [Embodiment] Fig. 1 is an explanatory diagram showing a typical embodiment of the present invention, in which an oil tank 1 consists of a container body 1a and a lid 1b, and a ring-shaped packing 2 is provided on the upper periphery of the container body 1a. mated and sealing the tank.
A is hydraulic oil and B is the atmosphere. tank 1
The hydraulic oil A in the
0, is pumped out from the pipe 4a, is supplied as high pressure oil, passes through a hydraulic control valve section (not shown), and reaches the hydraulic actuator section.On the other hand, low pressure oil passes along the arrow inside the pipe 4b, and is supplied to the inlet port. It is returned or replenished into tank 1 from 11. Although the type of inert gas applied to the present invention is not specified, for example, nitrogen gas supplied from a nitrogen gas cylinder 5 is pressurized into the atmosphere B of the tank 1 through a pressure reducing valve 6. Note that 7 is a relief valve with a pilot, and 8 is a pressure gauge. Before nitrogen gas injection, that is, lid 1b
Atmosphere B immediately after the nitrogen gas is closed is composed of air, so it is necessary to completely purge the air at the beginning of nitrogen gas injection, and it takes some time to complete the nitrogen gas replacement, but once the nitrogen gas is After the replacement is performed, it is necessary to pressurize the atmosphere B slightly, for example to about 0.2 to 0.3 Kgf/cm ² in gauge pressure, and fill it with nitrogen. A stop valve 9 is attached. Note that circuit changes such as changing the position and installing the relief valve 7 in place of the check valve 9 can be made freely. With this configuration, even if the oil level in the tank drops due to an oil leak, or if the oil level in the tank rises due to the installation of a continuous replenishment mechanism, atmosphere B can be kept under constant pressure. This allows the hydraulic system to be operated continuously under constant conditions. When removing the lid 1b to replenish or replace hydraulic oil,
All you have to do is return to the initial state and restart from the air purge stage. Furthermore, in the present invention, since it is not possible to peek at the liquid level of the tank 1 from above, it is also recommended that a suitable liquid level gauge be attached to the tank 1. By injecting the inert gas into the atmosphere B in this way, the air dissolved in the hydraulic oil is gradually replaced until a certain equilibrium is established with the inert gas in the atmosphere B. Therefore, the amount of air in the hydraulic equipment system becomes extremely small, and the atmosphere B becomes an almost completely inert gas atmosphere, so oxidation of the equipment surfaces in contact with these is suppressed and the life of the equipment is extended. Oxidative deterioration of the hydraulic oil itself is also prevented. In addition to this, water-glycol hydraulic fluids have the characteristic that cavitation tends to occur on the suction side of the pump due to the fact that they contain water.
It is also recognized that the pressure of the inert gas relaxes the suction conditions and prevents the occurrence of cavitation. The structure of the present invention is as described above, but changes in the physical properties of the water-glycol hydraulic oil were measured when it was exposed to the atmosphere and when it was protected in a nitrogen atmosphere. Since there is data, I will describe it next. <Oxidation Stability> An accelerated oxidation test was conducted according to ASTM D 2272. A commercially available hydraulic oil was appropriately selected as the water-glycol hydraulic oil, and the sealed gas pressure was 6.3 atm (25°C).
A test was conducted using a copper coil in a gas phase of 250 ml at 150° C. for 6 hours, and the results shown in Table 1 were obtained. <Rust prevention> 50 ml of the sample solution and a copper piece were placed in a 450 ml glass bottle, and the copper surface was observed after being left at 40°C for 2 weeks, and the results shown in Table 2 were obtained.

【table】

[Table] As shown in Tables 1 and 2, the oxidation stability and rust prevention properties of water-glycol hydraulic fluids when placed in a nitrogen atmosphere are extremely superior to those when placed in the air. , the effects of the present invention have been clarified. [Effects of the invention] Since the structure of the invention is as described above, even if the hydraulic system is operated under high temperature conditions for a long time, deterioration of the water-glycol hydraulic fluid is prevented, and the frequency of its replacement is drastically reduced. The evaporation loss of water and the consumption of rust inhibitors have also been prevented, resulting in a drastic reduction in the frequency of replenishment of these agents. In addition, oxidation of the equipment, especially the tank, was prevented, the life of the equipment was extended, and the flame-retardant hydraulic oil was made extremely easy to use. In addition, oxidative deterioration of the hydraulic fluid itself was prevented, and cavitation that was observed on the suction side of the hydraulic pump was also suppressed.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention. 1...Tank, 5...Nitrogen cylinder.

Claims (1)

[Scope of utility model registration request] Water supplied to hydraulic equipment used under high heat
This is a storage tank for glycol-based hydraulic oil, and the tank has a structure that exhibits airtightness with a sealed lid, and an exhaust device with a pressure retention function in the tank is installed on the gas phase side wall of the tank. A storage tank for water-glycol hydraulic oil, characterized in that an inert gas injection device is attached thereto, and an outlet and an inlet for the hydraulic oil are provided on the liquid phase side wall surface of the tank.