Events related to corruption of pressure hose
Currently in operation in the pressure hose, leaks due to cracks and penetration of the plant have occurred for investigation.
Survey was conducted in order to elucidate the cause of the damage
Pressure hose with a twist of penetration of the plant
Twisting of pressure hose has been confirmed at the start of water flow. For start and stop the device is repeated, each time twisting the hose is added, that may have led to the damage. Damaged hose or by adding a twist to the hose (① Investigation)
Was investigated how they affect the strength hose.
Whether or not to penetrate the buds of the plant, there is no knowledge. Was investigated through the ease of using a needle to the hose to simulate the bud of the plant (② Investigation).
The structure of pressure hose
Fiber-reinforced rubber PVC rigid PVC
Cross-sectional view of the hose
Wall material of the hose, a three-layer structure is sandwiched between PVC and rubber reinforcing fibers of the mesh. In addition, there is also the reinforcing fiber in the circumferential direction of the hose.
Fused salt in a spiral Bichubu hard as a reinforcing material external to the outside of the hose wall material.
Test and tensile test pressure hose twisting
Testing machine attached to a pressure hose twisting, while torsion repeated addition, we measured the presence or absence of leak and torque (Photo 1). Tensile strength was measured by tensile tests of torsion was added further pressure hose (Photo 2). If the pressure is high, was seen reduced torque and deformation, leak did not occur. In addition, the crack has not been confirmed inside the rubber. Repeated starting and stopping of the pump, was tested by simulating water flow, including the opening and closing of valve steep, the actual equipment, it was confirmed the degree of pressure hose to move or twist. As with the real machine, and up to approximately 20 ° twist of movement of the hose of a few cm was observed at the start of water flow. → true test loop pump performance test summary twisting was carried out with quite stringent conditions than the actual flow rate: up to 650L/min
, Maximum lifting height 100m
Maximum allowable working pressure: 0.8MPa
Design pressure (1.0MPa Pipe size):80A
Pressure gauge pressure gauge electromagnetic flowmeter valve ball valve
Overview caliber pressure hose: 75A
Allowable bending radius: 750mm
Pressure hose to above, also in addition a considerable number of torsion of the conditions more severe than actual, damage caused by the leak did not occur.
Slight decrease in strength is seen along with the torsion, decreased enough to damage the hose will not occur. From the above, in the degree of twist in the hose due to the actual operation it is presumed that damage to the hose will not occur. However, it is estimated that if there was internal pressure fluctuations and rapid, and the wound of the hose, and prone to corruption.
I checked with the manufacturer that manufactures sheet grass-proof plant had been through the hose at the scene, from that clumps of shapes and colors, around the bud, get the opinion and no doubt in Imperata was. Imperata cylindrica, sprout germinate around May to June in the perennial that inhabits the streets of Japan, such as wasteland, thin and sharp tip. This bud test was simulated using a needle for the evaluation of waterproof material such as 耐根 (JSTM G7101 has the power to penetrate more easily through a sheet of general anti-grass
PVC and rubber layer is cut out from a hose that conforms to the tests) Test methods, and confirmed its 耐根 of hose material, fixed 5.2 scissors crowded as shown in the figure below to jigs
And shape as shown in. The material is
Stainless steel (JIS G 4303Prescribed in the SUS440C Throw away the hardness of more than or equivalent Say)
Steel and stainless. In addition, the tapered portion of the polishing surface roughness
And. In addition, according to the standard test, if the load exceeds the 50N in Figures 1 and 2 during the test to abort the test, where the standard Testing Center for Construction Materials
JSTM G7101: 2011
“Test method was simulated using a needle for the evaluation of waterproof material such as 耐根” Foundation (Testing Center for Construction Materials Reprint from) issue. Hose is a structure as shown in the right figure. In the actual test, where the simulated needle through the soft PVC layer, touched the fiber reinforcement, for load exceeds 50N, was evaluated by the maximum load of up to penetrate the soft PVC.
It is estimated the following materials has been evaluated 20N, and “lack of 耐根” is the maximum load, the possibility to penetrate the plant and there is enough soft PVC layer.
There may 耐根 耐根 that may not have nearly the maximum load of 50N or more 耐根 maximum load below 20 ~ 50N 20N maximum load criteria of 耐根
Bud of the plant if the spiky (such as Imperata cylindrica), by weight of the hose to act, it is estimated that penetration to the inside of the hose can occur.
In addition, it is estimated that surface scratches, and that can degrade the strength of the hose, such as penetration of water. To study and implement the following measures, depending on the installation situation of the hose, etc.
Hose moved onto the asphalt
Laying hose at the bottom of (commercially available) sheet Imperata measures
U-shaped groove of the hose to the relocation, etc. (concrete) (laying)
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