First, the key points of the safety inspection of the pile machine assembly
Initially understand the general situation of the construction site, determine the location of equipment stacking, check whether the equipment accessories are complete after entering the site, and start assembly after basic preparation work, focusing on the following parts;
1. Preparation before assembly
(1) Seriously study and master the basic information on the site; there are construction fences and related warning signs around the operation area.
(2) Reasonably determine the parking position of the pile driver equipment
According to the site situation, we must first stay away from river ponds, mud pits, high-voltage lines, soft soil layers, surrounding buildings, etc.; according to the construction organization design, try to choose to stack and stop near the pile position of the first construction.
(3) Clean up the obstacles on the assembly site, level the site, and if necessary, lay the block or sleeper to enlarge the supporting area of ​​the pile driver; the average foundation bearing capacity of the large tonnage (static pressure) pile machine parking site should be no less than 35 kPa.
?) Check whether the equipment accessories and auxiliary construction equipment are complete, such as counterweight, conduit, concrete mixer, ash (mud) slurry pump, electric welding machine, testing equipment, etc., should be inspected according to the corresponding safety technical regulations before construction, and placed The location should be convenient for construction management.
(5) Reasonably arrange the laying position and direction of the electric control circuit, minimize the distance between the pile driver and the power distribution (box) cabinet, and reduce the line power loss. In one case, the distance between the working point (pile position) and the power supply point is controlled within 200m, and the starting voltage drop is not more than 10% of the rated voltage; the nighttime construction must be equipped with sufficient illumination points for independent laying of the line.
(6) Non-assembly personnel should be away from the equipment assembly site.
2, mechanical parts assembly inspection
According to the characteristics of different types of pile machines, the assembly according to the manufacturer's instructions, pay attention to the following points:
(1) There are no (weld) cracks, distortions, severe rust, etc. in the main structural members and the traveling mechanism. For example, the deformation of the guide groove of the drill machine affects the verticality of the pile body, and the deformation of the guide rail of the vibratory pile machine affects the vibration hammer. Sliding and so on.
(2) The connection of the fastening parts (buckle) such as bolts, flanges and pins at various positions (high-strength) such as bars and hammer boxes must be reliable and tight.
(3) Replace the aging, damaged and worn parts in time.
(4) The wire rope has no broken strands, severe rust and wear, and protects the oil from being evenly coated; in the hooks, pulleys, etc., there should be reliable anti-hook insurance, anti-wire rope jump protection and other protection devices; strict implementation of scrapping standards, timely replacement failure Wire rope.
(5) The control instruments such as current (pressure) meter and oil pressure gauge work well.
(6) The safety cover of the transmission components such as the motor and the hoist is intact.
(7) The water and oil control valve and the electric push button switch are well sealed and can be started freely.
3, transmission system and oil circuit, lubrication inspection
The drive system of the pile driver is composed of mechanical and hydraulic dynamic systems. After the assembly of the mechanical components, the transmission system and its lubrication, oil circuit work and protection status should be checked.
(1) According to the requirements of the manufacturer's manual, replace the mechanical oil, gear oil, grease, etc. that meet the seasonal temperature requirements corresponding to the transmission components on time, quarterly and quality;
(2) The wear value of the motor, variable (decrease) speed box, gear, winch, hydraulic and other transmission components shall not exceed the standard and work normally;
(3) The transmission component pulley, the guiding device and the rotating shaft rotate freely, and the grease is evenly coated, such as a hydraulic cylinder, a vibration (hammer) box and the like;
(4) Check whether the oil pipe and joint pipe clamp are damaged, loose, oily, leaking, and the seals should be in good condition;
(5) The hydraulic pump, valve and other components are clean and fixed firmly. The hydraulic oil is strictly filtered, and its oil viscosity and cleanliness are normal.
4, electrical control line inspection
(1) Configuring professional electricians qualified for post training, specializing in the management of electric control system for pile driver construction, strictly implementing the technical standards for power distribution safety management, frequently inspecting on-site electrical box rejection lines and control switches, and discovering hidden dangers should be reported and repaired in time.
(2) The pile machine equipment and the auxiliary construction equipment are equipped with their own special switch distribution boxes, the door locks are complete, and the “one machine and one gate†system is implemented;
(3) The power supply line should meet the electric power and voltage requirements of the pile machine. The cable line section must be matched with the electric power of the pile machine. For example, the DZ90 vibration pile machine is within 100m of the power transformer, the transformer power should be greater than 200kVA, and the cable cross-sectional area is greater than 120mmsup> 2;
(4) The three-phase wiring of the motor is in accordance with the electrical schematic diagram and the insulation test value is qualified (for example, greater than 0.5MΩ), the terminal wiring in the junction box is correct and reliable, the terminal is not loose and the insulation is good;
(5) Carry out the appearance and internal insulation and conduction test of the cable, check whether there is any damage, the internal core wire breaks, and the insulation test value between the core wires must meet the requirements of the manual (for example, greater than 2 MΩ);
(6) The electric control circuit should be laid or installed with steel pipe protection measures, etc. It is strictly forbidden to crush and pull heavy objects, and the pressure test between the main circuit and the body of the electric appliance is qualified;
(7) Install the protection device in accordance with the standard leakage, isolation, short circuit, voltage loss, overcurrent, etc. in the distribution box. The lightning protection of the electrical system is well connected to the grounding line. The resistance value is in accordance with the requirements (if the grounding resistance should be less than 4Ω) );
(8) The insulation and contact of other electrical components are good, the connection is firm, the line is smooth, and the control electrical signal is reflected correctly.
Second, pile machine construction and demolition safety technical inspection points
The assembled pile machine equipment should be operated strictly according to the relevant work flow during construction. During the construction period, the working status should be checked and observed frequently, and the piles should be constructed in the order determined by the organization design. Before starting construction, the technical personnel shall provide safety management technology to all (unit operation) construction personnel and configure professional safety management personnel.
1. The operator of the pile machine must undergo strict training before the post. Only after the qualification is qualified can the construction be completed. During the construction period, the employee must not leave the job without authorization. It is strictly forbidden for the unrelated personnel to enter the operation (room) position.
2, the operator should be familiar with the function of the pile machine equipment, technical indicators, conditions of use, etc., the operation should be accurate and gentle, prohibiting overload, mechanical disease and barbaric operation.
3. Before the formal construction, the assembled pile machine equipment and auxiliary equipment should be checked for the empty load joint test operation to see if the movement of each component (bit) is correct and stable, no abnormal noise, the control instrument reflects whether it is sensitive, and whether the electrical line works. normal. Find problems and fix them in time.
4. If the construction may cause adjacent houses to crack, pipeline breakage, water leakage, and roadbed sinking, etc., emergency rescue plans should be formulated in advance and reported to the construction and supervision units for filing.
5. Strengthen the safety monitoring work of buildings around the site, and make timely written observation records; when constructing special piles such as side piles and corner piles, pay attention to the adverse effects on nearby buildings; construction of static pressure, immersed pipes, etc. Measures such as excavating ground anti-vibration troughs and pre-drilling can be considered to reduce the impact of soil compaction;
6. When moving between pile positions, it should not be pressed on the pile (top) position that has been completed. Keep away from other construction machinery and keep the pile machine safe distance (such as 6m or more) with high-voltage line. Keep the equipment vertical and stable during walking. Sleepers, fill the pits and pits, replace the soft soil layers, add temporary fixed rope locks, clear obstacles on the walking lines, etc.; when the high vibration and mixing pile machines of the frame are moved, they must be prevented from overturning. Emergency measures.
In order to keep the equipment stable and protect the hydraulic system from impact damage, the hydraulic system cannot be operated at full stroke.
7. When the resistance of the ground layer is large, pay attention to observing the current value index or slow down the speed of the pile (forming hole), or stop the construction after shutdown to avoid the super power of the motor to burn the fuse or the motor; when the resistance of the ground layer suddenly decreases (such as Cave) should be shut down for investigation.
8. When abnormal noise is found during construction, it should be stopped immediately; during construction and overhaul, it is strictly forbidden to stand under the piling hammer and lifting machine; the pile hole that has been completed should be marked with warning signs, if necessary (large aperture pile) with cover plate to prevent The person fell.
9. In case of thunderstorms, severe winds such as winds above 6 or above, it is necessary to install a cable wind rope, lay down the rack and other measures to stop the pile driver and close the electric control switch to prevent overturning.
10. In case of emergency such as power outage or out of control during construction, reliable measures should be taken to prevent the equipment from collapsing and the power switch should be cut off in time; the pile driver should be stopped at the end of the rest or operation, the pile hammer should be dropped, and the power supply should be cut off.
11. Pay close attention to the temperature changes of important parts such as motors, hydraulic cylinders and bearings.
12. In winter construction, pay attention to anti-freezing protection measures for equipment related parts, such as water pump discharging water in time, using low temperature resistant oil (such as No. 120 gear oil, No. 46 anti-wear hydraulic oil), etc.
13. In summer, pay attention to high-temperature protection measures for equipment-related parts, such as electric lines, bearings, electric motors, and use high-temperature protection oil such as (No. 90 gear oil, No. 68 anti-wear hydraulic oil);
14. There are several common mechanical actions in the construction of pile machines, such as hanging piles (reinforcing cages), lifting hammers, turning, walking, countersunking, pile pressing, etc. It is not advisable to carry out two or more kinds of mechanical actions at the same time.
15. When the overhauled or newly purchased pile driver is first constructed, it should be gradually balanced during its walking (grinding) period, and it is forbidden to operate at full load; for protection equipment, it is not suitable after the period of walking (grinding) Running at full capacity.
16. For complex foundation construction projects with strong comprehensive foundation pit support and building displacement, the project safety protection check calculation must be carried out according to the national technical regulations, and the local competent department should be reported to organize experts for demonstration and review. At the same time, it should cooperate with the conclusions of its verification and verification to carry out the inspection of the comprehensive safety management technology of the pile machine equipment and construction.
17, exit and demolition inspection
Pile driver equipment for construction tasks, most types of equipment need to be demolished before exiting for partial transport. For this purpose, the following preparations should be made:
(1) Leveling the site and clearing obstacles, so that it is convenient to drag the vehicle safely in and out, and the lifting equipment can be docked smoothly;
(2) Cleaning and maintenance of the pile driver equipment, moving it to a position where it is convenient for unloading and hauling, shutting off the power supply, preparing the demolition tools, lifting equipment, and hauling the vehicle;
(3) Make specific steps for demolition according to the order specified in the equipment manual provided by the manufacturer;
(4) Do a good job in the safety protection of demolition personnel, and unrelated personnel should stay away from the demolition site.
(5) During the demolition and lifting, attention should be paid to the protection of important parts in the pile driver equipment. It is strictly forbidden to damage the equipment by barbaric operation.
Polycarboxylate Superplasticizer
For example, self-consolidated concrete and slump retention beyond two hours without significant set time extension have been made possible with PCEs. I was fortunate to be on the R&D/marketing team for a major chemical admixture company that launched the first group of polycarboxylate-based admixtures in the 1990s. Like all new technologies introduced into the building industry, there has been a long learning curve which underscores the highly diverse set of materials and applications with concrete construction. This article summarizes a few key performance attributes which have been learned from both commercial concrete applications and the research laboratory. Some of the benefits provided by polycarboxylate superplasticizers have been discussed and previously published in The Concrete Producer.
The Polycarboxylate Family
The term “polycarboxylate” actually applies to a very large family of polymers, which chemists can design to impart a special performance to concrete mixtures. Subsequent to the introduction of so-called general purpose PCE superplasticizers, new PCE products have been developed especially designed to provide high early strength and different levels of slump retention, as well as provide different capabilities to manage air contents in concrete. One such class of polycarboxylates has little impact on initial slump, but because of a time-release function built into the PCE polymer, concrete slump increases generally in a predictive manner as a function of mixing time (see Figure 1). Thus, such a product can be added at various dosages to an already admixed concrete to dial in slump retention as a function of job conditions (haul time, temperature, delay before discharge, etc). Very often, a superplasticizer will be formulated with a blend of two or more PCEs to achieve a combined performance of both early strength and long slump life. Researchers will continue to actively manipulate PCE polymer structure to meet the ever changing material and construction requirements.
- Air entrainment: Essentially all polycarboxylate-based admixtures are formulated with a defoamer to control unwanted air entrainment inherent with the PCE polymer. For both air-entrained and non-air entrained concrete applications, air contents can usually be effectively managed with selection of the PCE-based superplasticizer product most compatible with job materials. Varying carbon content in fly ash can make consistent air contents challenging as the hydrophobic nature of defoamers leads to adsorption by fly ash carbon. In general, compared to polynaphthalene sulfonate polymer (PNS) based superplasticizers, PCE-based products can make air-entraining admixtures (AEA) more efficient, meaning a lower AEA can be required to achieve the same air content.
- Impact of clays: Unlike PNS superplasticizers, the PCE polymer will be readily and irreversibly adsorbed by certain clay fines that could be present in various aggregate sources. Figure 2 illustrates the impact that a clay- bearing sand, having a methylene blue value of 1.30, can have on the dosages of PNS verse PCE-based superplasticizers to achieve compatible slump. Normally, with clay-free or low-clay sands, PCEs are dosed about one-third that of PNS-based superplasticizers for comparable slump. However, when clays are present in certain sands, up to a 50% higher dosage of PCE versus PNS can be expected. Therefore, if the dosage of a PCE superplasticizer were to unexpectedly increase, checking for clay fines in the aggregate supply should be prioritized.
- Flexible dosing: Again, unlike PNS-based superplasticizers, which invariably should be added in a delayed addition mode (that is, after the cement and water have begun to mix), PCEs are relatively insensitive to the time of addition, allowing for greater flexibility in the concrete batching process.
- Incompatibility with PNS superplasticizers: Use of PCEs and PNS-based products in the same concrete mixture results in rapid loss of workability. Thus, the two technologies, PNS and PCE, should not be used in the same concrete mixture.
- Strength Synergy with calcium-based set accelerators: When PCE-based superplasticizers are used with set accelerators and corrosion inhibitors comprised of calcium salts, unexpected strength gains have been observed compared to a similar concrete mix admixed with a PNS-based product. This synergy in strength gain with PCEs was first observed in a mix containing a calcium nitrite-based corrosion inhibitor. The data summarized in Table 1 was reported by a concrete producer who had been using a combination of a lignosulfonate-based ASTM C494 type A water reducer and a Type G PNS/Lignin-based superplasticizer to manufacture prestress piles.
This remarkable strength difference, obtained by merely changing the superplasticizer type from a PNS to a polycarboxylate, was verified from a scientific study, and can be useful in reducing cement contents while still meeting strength specifications. Interestingly, the strength difference does not seem to be associated with increased heat of hydration, but rather is related to a denser microstructure produced by the combination of a calcium-based accelerating or corrosion-inhibiting admixture and polycarboxylate-based admixture.
The PCE superplasticizer replaced both the PNS/lignin and Type A water-reducing products at about one-third the dosage rate. Also, note the 50% drop in AEA dosage rate with the PCE admixed concrete to obtain the same air content.
To summarize, though the concrete industry has learned much about harnessing the versatility and understanding the limitations of PCE-based superplasticizers, chemists, working with concrete technologists, will continue to modify the polymer structure to achieve new capabilities for the production, placement and service life of concrete mixtures.
by-Ara
PCE based plasticizer
Shanghai Hongyun New Construction Materials Co., Ltd , https://www.hongyunpce.com