Pre-drilling side pressure instrument models, but its structure and Mena-type side pressure instrument is basically the same. Domestic manufacturers of fixed-point production of bypass pressure instrument manufacturers for Jiangsu Drift City Instrument Factory, the production of PY-type bypass pressure instrument, there have been three generations of products. 80 years, mainly the production of PY-1 and PY-2 type; on this basis, in the 90s and the production of PY-3 type pre-drilling bypass pressure instrument. Now take the domestic PY-type side pressure meter as an example (Figure 5-10), a brief description of its equipment and its installation and commissioning.
(A) equipment
Pre-drilling side pressure test of the main equipment for the side pressure instrument. It mainly consists of the following four parts.
1. By-pass pressure
It is the most important part of the by-pass pressure instrument, by the round metal skeleton and wrapped in the outside of the rubber membrane is composed of. By-pass pressure is generally three-cavity type, the center of the main chamber (also known as the test chamber), the upper and lower for the protection of the chamber. The main cavity and the protective cavity do not communicate with each other, the protective cavity is connected, the main cavity in the middle of the sandwich. During the test, high-pressure water enters the main chamber from the control unit through the intermediate piping system, causing the rubber membrane to expand radially (laterally) to the surrounding soil, compressing the surrounding soil, thus establishing a correlation between the pressure in the main chamber and the volumetric deformation increment of the soil. At the same time, the same pressure of water is also synchronized to the two protective cavities to keep the pressure and the main cavity consistent, in order to force the main cavity to the surrounding along the horizontal direction of synchronous deformation. This allows the deformation of the soil around the main chamber to be treated as a plane strain problem.
Figure 5-10 PY-2 type by-pressurizer piping (structure) diagram
The by-pressurizer has a guide pipe in the center, which is used to drain groundwater so that the by-pressurizer can be placed at the test depth smoothly. The by-pressure apparatus is divided into two kinds: naked and with metal armor protective film. For general types of clay, can directly use the bare by-pressure; such as encountered in the soil layer contains gravel and other sharp substances will damage the elastic membrane, can be outside the by-pressure elastic membrane with metal armor protective film for testing, its main role is to protect the elastic membrane, so that the by-pressure test can be carried out normally.
At present, PY-2 type and PY-3 type by-pressure device outer diameter are 50mm (55mm with metal armor sheath), the length of the test chamber are 250mm, the volume of 491cm3 (594cm3 with metal armor sheath). The total length of the by-passer is 500mm, and the upper and lower chambers (protective chambers) are communicated with copper conduits, while the middle chamber is isolated.
2. Pressure and volume control box
Usually, pre-drilled by-pressure instrument control unit is set on the tripod for a box structure. It includes two major parts: the deformation measuring device and the pressurizing and stabilizing device. The former mainly has a measuring tube, auxiliary tube (PY-3 type only measuring tube, its internal cross-section of 14.32cm2, volume of 650cm3), water tanks and various types of valves and other components; measuring tube and auxiliary tube are made of plexiglass, the smallest scale of 1mm, PY-2-type measuring tube internal cross-section of 15.28cm2, PY-3-type is equipped with a liquid level display, the resolution can be increased to 0.1mm. The main function of this part is to control the amount of water into the by-pass pressure, measured by the tube or liquid level meter read the corresponding deformation value of the hole wall soil body under pressure. Pressurization and pressure stabilization device includes a high-pressure nitrogen cylinder or artificial pump, gas storage tank, regulator and the corresponding pressure gauge. Pressurization and pressure stabilization are controlled by the regulator. The main function of this part of the device is to control the pressure into the bypass pressure. In short, the relationship between the pressure on the soil and the corresponding volume deformation (realized by measuring the drop in water level of the tube) through the control box has been realized.
3. Piping system
The piping is the "bridge" connecting the by-pass pressure and the control box. Its role is to send the pressure and water from the control box to the by-pass pressure. PY-2 type has two pressure conduits and two water injection pipe, PY-3 type has two pressure conduits, but only one water injection pipe (Figure 5-11). The tubing is made of nylon 1010 material that can withstand high pressures, and its length is determined by the maximum test depth, which is usually more than ten meters long. The line attached to the by-pressure vessel can be quickly connected to the control box by means of a quick coupling.
Figure 5-11 PY-3 type by-pressure instrument pipeline diagram
4. Hole forming tools and other accessories
Pre-drilling type to be formed in advance, the hole forming tool is mainly spoon drill (Figure 5-12), with high-strength steel made of spoon bit, probe rod and soil lifting drill bit. It is suitable for general cohesive soils. For hard soils, light drilling rigs should be used to form holes.
Figure 5-12 Hole-forming tool
The PY type parapressure meter is suitable for testing in clayey, pulverized and sandy soil formations. If the stratum contains gravel, etc., the by-pressure apparatus with metal armored sheath should be used so as not to puncture the rubber membrane. The current test pressure has been increased to 2.5MPa, the depth of up to 20 m. If the selection of higher strength materials, improve the sealing of the valve at high pressure, the test pressure and depth can be increased. Foreign similar products, the test pressure has reached 12.5MPa (such as Ménard GB type pre-drilling side pressure instrument), the test depth of up to 50m; some have reached 70MPa, can be measured in hard rock (such as the U.S. Goodman52101 type).
(B) the repair and maintenance of the side pressure instrument
1. The construction and maintenance of the main components of the instrument
(1) the skin membrane type control valve: its structure is shown in Figure 5-13.
Figure 5-13: Diaphragm type control valve
1-rotating wheel; 2-guiding screw; 3-splicing cap (nut); 4-valve plug; 5-pressure ring; 6-diaphragm; 7-valve seat. -When the rotary wheel is rotated clockwise, the screw pushes the valve plug to press the diaphragm tightly in the orifice, and the pipeline is disconnected; when the rotary wheel is rotated counterclockwise, the diaphragm restores its original position by its own elasticity and the internal pressure in the pipeline, and the pipeline is connected. In this way, the pipeline open and close the control role.
The advantages of the diaphragm type valve are: good sealing performance, high pressure resistance. Disadvantages are: open and close no fixed position, operation by feel, the membrane is easy to damage or cut into the hole, so that the pipeline blockage, affecting the work. When closing the pipeline, it is not advisable to screw the skin membrane type valve too tightly. After the work is completed, all valves must be loosened, so that the skin membrane back to the free state. As soon as the diaphragm is damaged, it must be replaced.
Replace the dermal membrane in the following order: spin down the spinning wheel 1, loosen the nut 3, loosen the pilot screw 2, and remove it; use tweezers to remove the pressure ring 5 pressed on the dermal membrane, remove the old dermal membrane 6, and replace it with a new membrane. When replacing the new membrane, note that the dermal membrane drum shape should be outward. Assembly is carried out in the reverse order of disassembly. When assembling the leadscrew 2, be careful not to over-tighten it, nor should it be too loose. Too tight, the skin membrane closely fits the orifice, so that the pipeline is not smooth; too loose, resulting in water leakage and air leakage.
(2) ferrule type pipe fitting: its structure is shown in Figure 5-14.
Figure 5-14 tube fitting
1-connector body; 2-pressure nut; 3-seal ring; 4-takeover
The joint is by the compression nut 2 seal ring tightly compressed 3, so that the deformation of the receiver and the joint body closely affixed to form a hard seal. Assembly and test pressure should not be disassembled, if the need to disassemble and repair, and then after assembly, its sealing performance will be significantly reduced. If it is impossible to maintain its working requirements, the seal must be replaced. Replacement method is as follows: with a fine-toothed file will be filed to remove the seal, pay attention to not file the receiver, replaced with a new seal can be. When the seal has been damaged, found that the receiver has been deformed, must be replaced at the same time to ensure that the receiver to ensure the quality of the joint.
(3) regulator: structure shown in Figure 5-15.
The balance of the regulator works: clockwise rotation of the regulator handle 1, the main spring 3 compression balance diaphragm 4, so that the top lever 6 and the overflow port 14 fit, and move along the axial direction, push open the inlet plug 8, so that the studio into the air. When the studio and pipeline air pressure rises to a fixed value, the balance of the diaphragm reverse pressure to move, the top bar by the force of the lower spring 9, through the lower top bar 11, plugs, etc. to pass back up, close the air inlet to stop air intake. When the studio and pipeline air pressure exceeds the fixed value, the balance diaphragm by the studio air pressure, compression of the main spring upward movement, resulting in the overflow port to open the release of residual air, air pressure down to the fixed value. When the studio and pipeline due to volume changes and other reasons for air pressure drop, the balance diaphragm and the role of the main spring will be the overflow port closed, and pushed open the air inlet, so that the inlet to boost pressure. Such a continuous cycle, to achieve the role of pressure stabilization.
The regulator is the key component of the instrument. The accuracy of the regulator directly affects the accuracy of the test results; use, in the absence of connecting the air source or air pressure, shall not rotate the regulator handle for invalid pressure regulation. After the end of the work, the handle should be immediately loosened, so that the main spring to return to normal, in order to extend its working life, and to maintain a considerable degree of accuracy.
Common faults and troubleshooting methods of regulator:
①Pressure pointer "crawling" after regulating: "crawling" is mainly due to the airflow medium entrained dust accumulated on the surface of the plug, so that the air inlet and the plug can not be caused by a close fit; Secondly, due to long-term use, the surface of the plug has obvious indentation, resulting in surface unevenness, and the air inlet can not be closed. The elimination method is: rotate the lower air chamber 12, remove the plug from the guide sleeve 13, under a magnifying glass with alcohol to clean the surface of the plug, so that no dust adhesion. At the same time, with tweezers with alcohol cotton wool scrub inlet end surface; cleaning, pay attention to prevent the surface bruises and scratches. If there are scratches and bruises when viewed under a magnifying glass, the plug or air inlet must be replaced.
Figure 5-15 Regulator Structure
1-Handle; 2-Upper Cylinder; 3-Main Spring; 4-Balance Diaphragm; 5-Valve Body; 6-Top Rod; 7-Inlet Port. -top bar; 7-inlet; 8-plug; 9-lower spring; 10-adjustment screw; 11-lower top bar; 12-lower chamber; 13 -guide sleeve; 14-overflow port
②overflow port gas consumption: that is, the overflow port in the rated working pressure is not exceeded when the exhaust more than. The elimination method is to increase the contact pressure of the top rod and overflow port. Adjustment screw 10 clockwise to the direction of the tight rotation, to not consume gas until (taking into account the sensitivity of the regulator, should not be screwed too tight). If air is still consumed, the overflow port must be removed and its contact plane must be ground so that it is in even contact with the top lever sphere.
③Lower air chamber leakage: generally due to aging of the lower top rod sealing sleeve, this time to replace the sealing sleeve.
(4) quick coupling: its composition is shown in Figure 5-16. Due to frequent use, so that the seal ring 2 wear, affecting the sealing, must be replaced immediately. Test work is completed, remove the quick connector plug tube 3, should be put on the sheath, to prevent sediment from the mouth of the plug tube into the conduit, damage to the instrument.
Figure 5-16 Quick connector
1-socket; 2-seal; 3-plug tube
(5) bypass pressure: bypass pressure is the test probe. Its structure is shown in Figure 5-17.
Figure 5-17 by-pressure device structure
1-conducting, guide tube; 2-elastic membrane; 3-drainage tube tile; 4-center conduit; 5-copper section head 6-inner compression ring; 7-tube splicing boot; 8-splicing cap; 9-outer compression ring
When the by-pass pressure vessel elastic membrane is damaged and needs to be replaced, the replacement order is as follows:
1) use a knife to cut open the old membrane, take off the tube splicing boot 7, loosen the various copper Section head cap 8, remove the old membrane, while removing both ends of the copper section of the head of the inner and outer compression ring 6, 9 and cap;
② remove the upper and lower auxiliary cavity leakage tube tile, cleaning impurities;
③ the new membrane coated with soap solution on the inner wall, from the bypass pressure end of the set into the end of the copper section of the head and through the copper section head of the end of the outer compression ring, through the medium cavity leakage tube tile, so that the new membrane position and the bypass pressure skeleton position is exactly the same, and the set of Two copper node head outside the compression ring;
4 will be the new membrane end of the external turn (turn over the attention of the membrane and the membrane coated with soap liquid, in order to profit slippery), until the exposure of the copper node head of the internal compression ring position;
5 set on the internal compression ring, with a hook wrench will be tightened splicing cap;
6 install the end of the leakage of the cylinder tile (pay attention to the right sign), will be over the end of the skin membrane back again;
⑦ successively set on the external compression ring, with the hook wrench will be tightly put together;
6 install end drain tile (pay attention to the right number), the turn over the end of the skin membrane and then turned back;
6 install the end leakage cylinder tile (pay attention to the number), turn over the end of the film and turn back;
7 successive sets of outer compression ring, inner compression ring, spelling tight cap;
8 the other end of the order of ④ - ⑦ operation.
Precautions: each section of the membrane after assembly must be tightly fitted to the parapressor skeleton, to prevent slack.
2. Instrument assembly and use
(1) Instrument assembly: tripod as a support, with M20 knurled copper nut linkage.
(2) The connection between the high-pressure nitrogen bottle and the instrument: if the high-pressure nitrogen source is used, the inlet end of the instrument accessory decompression table is connected to the nitrogen bottle, the outlet is connected to a φ6×1 nylon tube, and the other end is connected to the connector with the instrument marked with the words "nitrogen source".
3. Debugging of side pressure instrument
Before work, the instrument should be debugged, the purpose is to check whether the instrument is normal; if there is anomaly, must be dealt with to avoid interruption of the work.
(1) before the work of the water injection standard check: according to the operating order of water injection, found that the water injection is slow or not into the water, indicating that the water injection system has been blocked or clogged. Commonly occurring failure is the water injection valve, generally the valve skin film fit orifice caused by. At this point, you do not have to disassemble the valve, with the "backwash method" to eliminate the problem. Elimination method is: pressurize the tank to 0.5MPa or more, and close the drain valve and zero valve, the rest of the valve open, slowly pressurized to the pipeline (pressurized before the bypass pressure must be placed into the calibration cylinder, and will be opened to the water tank water injection cover). When you hear the water tank water noise, that is to indicate that the pipeline has been smooth. When the pressure is increased to more than 0.5MPa, if the water tank is still no water noise, indicating that the pipeline blockage is serious. At this time, the pipe must be dismantled to check, generally occurring parts of the blockage is the injection valve and the injection valve to the water tank pipe, other parts shall not be easily dismantled.
(2) elastic membrane seepage check: the instrument is filled with water, will be placed next to the instrument in the state of no external constraints on the side of the pressure, slowly to the side of the pressurizer pressurized to 0.05MPa; to be elastic membrane expansion, check the membrane with or without leakage phenomenon, where there is a leakage, need to be immediately replaced with an elastic membrane.
(3) the use of the tube instructions:
Figure 5-18 No. 3 holes in the tube (the figure in the number of holes)
This tube is No. 3 holes dedicated. When doing the elastic membrane binding force correction test, this tube should be pulled out of the No. 3 hole; after the test is completed, re-inserted for other tests.
This tube can be used interchangeably in No.1, No.2 and nitrogen sources.
4. Display meter adjustment instructions
(1) the instrument will be connected to the power supply, connected to the electrical test tube output plug; before the test, warm up half an hour before calibration.
(2) When calibrating, it is necessary to pull out the quick plugs of No.1 and No.2 holes of the by-pressure device, and replace them with the special plug connecting tubes for this instrument, so that No.1 and No.2 holes can communicate with each other.
(3) calibration process:
Figure 5-19 1,2 and nitrogen source hole special plug tube
①Injection of water in accordance with the order of operation, the water level of the test tube filled to the zero scale line, and then adjust the zero knob to the display of the instrument output of 400mV;
②Open the water injection valve, slightly pressurized (pressure should be less than 0.05 MPa), the water back to the water. MPa, the water back to the water tank) so that the water level of the test tube gradually fell to 400mm in the test tube, adjust the zero knob to the instrument output to zero;
3 and then repeatedly adjusted in the above way a few times, the display instrument can be recorded in the field;
4 Do not adjust the zero locking nut. The zeroing has been debugged in the instrument before delivery, to be adjusted when the instrument is cleaned measuring tube.
(C) the instrument factory inspection standards
PY-type by-pass pressure instrument factory main test items are:
(1) stability: at all levels of working pressure levels, the initial adjustment of the permissible fluctuations in 1min should be less than or equal to 0.0025MPa;
(2) sealing: in the rated working pressure, cut off the gas source test pressure 4h, the instrument should be less than or equal to the pressure drop value of the instrument. The pressure drop of the instrument should be less than or equal to 0.1MPa;
(3) Pressure regulating value: the maximum adjustable pressure value should not be less than 2.5MPa;
(4) Water injection: the water injection pressure is less than 0.05MPa, the working chamber and the circuit should be filled up in 5min;
(5) Tank cleanliness: there should be no any debris in the tank that causes clogging of the pipeline and affects the transparency of the measurement pipe;
(6) Water tank cleanliness: there is no any debris that causes clogging of the pipeline and affects the transparency of the measurement pipe. Pipe transparency of the presence of debris;
(6) quick couplings and instrument piping pressure: shall not be less than 2.5MPa;
(7) the absolute error of the liquid level display instrument: liquid level display instrument display and the number of marking, the maximum error in the whole 400mm absolute value shall not exceed 4mm.