I. Overview of the Project
Second, the basis of supervision
1, Technical Code for Ground Source Heat Pump System Engineering (GB 50366-2005)
2. Code for Construction Engineering Supervision (GB503 19-2000)
3, ground source heat pump design and construction drawings and disclosure, minutes of the blue prints.the design
4. Construction organization design of ground source heat pump
Third, the difficulties and key analysis
1. Installation and debugging of ground source heat pump control system. The control technology of ground source heat pump is relatively complex, and the initial investment cost is high, and the system needs to control and adjust two water systems and heat pump units at the same time, otherwise it will lead to unstable operation of the system, so this item is also one of the key points in the installation of ground source heat pump.
2. The core of ground source heat pump system is soil coupled underground heat exchanger. Pipe, pipe diameter, pipe length, number and spacing of vertical shafts, pipeline laying, pump selection and pipeline pressure-bearing capacity check are all key and difficult processes in the installation of ground source heat pump system.
3. Installation and debugging of underground system and water collector in air conditioning room. Because the valves on the water distributor and the water collector can control the heat exchange of each group of underground pipes, and it is convenient to find the accident site in case of failure, the flow balance between branch pipes needs to be adjusted through this system.
4. Installation and debugging of heat pump unit. In order to improve the energy efficiency ratio of heat pump unit under heating conditions, it is required to increase the evaporation temperature of the unit as much as possible. The operating cost of the system is the first concern of users. The inlet and outlet temperatures of the underground heat exchanger under heating conditions have been determined, that is, the inlet and outlet temperatures of the evaporator of the unit have been determined. The only way to improve the evaporation temperature is to reduce the temperature difference at the evaporator outlet, so the correct installation and normal operation of the heat pump is particularly important.
Fourth, the control target value and method
(A) the riser construction control
1, pay-off
Pay-off with reference to the positioning axis of the field project, and calibrate the position of the heat exchange hole according to the construction drawings to ensure the accurate position.
2. Erect drilling rig
(1) The tower chassis should be located at the drilling point, and the chassis should be leveled horizontally and vertically with a level meter, and the levelness should be ≤ 0.5 mm/m. ..
(2) After positioning the chassis, install the vertical pole of the tower, and measure the verticality of the tower with a plumb hammer and a ruler to ensure the verticality of the vertical pole of the tower.
(3) Install power head of drilling rig, lifting device of drilling rig, water filling (mud) of drill bit and other auxiliary devices.
(4) The concrete floor in the site shall be broken in time, and the sedimentation tank and mud ditch shall be dug and kept unblocked as required.
(5) Connect the electricity and water pipes to the drilling rig and its accessories, and test each equipment to determine the steering.
3, drilling
(1) Before drilling, make sure that the steering is correct, and recheck the levelness and verticality of the tower underframe and upright post.
(2) When drilling, the drilling speed should be uniform, and the operation of the drilling rig and auxiliary equipment should be paid close attention to. If any abnormality is found, it should be handled in time to prevent the thread of drill pipe and joint from being pulled off and the bit from falling off. At the same time, we should always pay attention to and record the geological changes of the stratum.
(3) During drilling, the platform manager and operators should regularly check the platform and ancillary equipment, and do a good job of maintenance in time to improve work efficiency.
(4) When the hole is drilled to the required depth, it should be drilled repeatedly to create smooth conditions for the lower heat exchange tube.
4. Pressure test
Before lowering the heat exchange tube, the water pressure test should be carried out according to the design requirements. The test pressure is 25MPa, and the pressure is stabilized for at least 30 minutes. After the pressure is stabilized, the pressure drop should not be greater than 3%, and there is no leakage. Hot-melt seal its nozzle and prepare to run the pipeline.
5. Lower the heat exchange tube
(1) In order to ensure the heat exchange effect and prevent the heat from flowing back between the branches, the distance between the two heat exchange branches should be kept, and the two heat exchange tubes should be separated and positioned with a separation positioning pipe clamp before the pipeline laying, and the distance between the separation positioning pipe clamps is 3m.
(2) According to the actual situation of the well, use the pipe running machine to run the pipe at a uniform speed to prevent the pipeline from being damaged in the process of running the pipe. If there are obstacles and obstacles, the reasons should be found out in time, and the pipe can be run again after being properly handled.
(3) When lowering the pipe device, the HDPE pipe head should be connected and fixed with the pipe device, and the pipe head should be tied with a plastic rope.
(4) Insert the lower pipe device together with the HDPE pipe into the borehole, and manually lift the HDPE pipe to one side to lower the pipe.
(5) When the pipe head sinks into the borehole, it should be measured according to the drill pipe, and the pipe should be stopped after reaching the effective depth, and it should be pulled by nylon rope to prevent sinking.
(6) If a pipe-lowering machine is used to lower the pipe, the pipe-lowering drill pipe should be lifted after the heat exchange pipe is in place. In order to prevent the heat exchanger from floating, a little grouting or yellow sand should be injected before lifting the pipe.
6. Backfilling
(1) Backfilling method: backfill with underground mud. Using special backfill pump, the filler is injected from the bottom of the hole and backfilled upward, so that the air is gradually removed, ensuring no backfill gap and ensuring heat transfer effect.
(2) Backfill: The thermal conductivity of backfill material has an important influence on the heat exchange capacity of underground pipelines. Backfill materials are in closest contact with underground heat exchangers after construction. The proportion and selection of backfill materials determine its heat transfer performance, which directly affects the heat transfer effect. In addition to heat transfer, its solidification strength grade should also be considered. Due to different geological structures, different expansion capacities and different extrusion pressures. Choosing suitable backfill can also prevent the underground heat exchange tube from being damaged by extrusion. Therefore, according to the geological report, the selection of backfill is also an important part to ensure the successful application of ground source heat pump.
(3) Backfilling equipment: When backfilling materials, high-pressure backfilling is required. If manual backfilling is used, the pressure is not enough and there are many gaps, which seriously affects the heat transfer effect, fails to reach the design parameters and cannot realize the cooling and heating of the system. The backfill equipment used has high backfill pressure, and the backfill material is injected from the bottom of the hole to ensure that there is no backfill gap, and the backfill material has good thermal conductivity after solidification.
(4) Full-hole backfilling to the elevation of the working face. After completion, it shall be marked with colored flags or other marks.
(2) Horizontal pipe construction control
1, material inspection and storage
The internal and external walls of pipe fittings and pipelines shall be smooth, free of bubbles, cracks, peeling, obvious marks and depressions; The colors of pipe fittings and pipes shall be consistent, and there shall be no uneven colors.
2, loading and unloading transportation
Handle with care when handling. It should not be impacted by violent collision and sharp objects. Do not throw, drop, roll or drag to avoid contact with oil. During storage and construction, mud and sundries should be strictly prevented from entering the pipe, and direct sunlight should be avoided in the storage place.
3. Connection mode
According to the design requirements, all polyethylene pipes should be connected by butt welding. The hot-melt connection of pipelines must be carried out in accordance with the manufacturer's construction technical specifications and standards.
4. In this project, most buried heat exchanger pipes are laid under the floor of the building. In order to ensure that the buried heat exchanger pipeline will not have problems due to compression, the following two countermeasures have been taken:
(1) First of all, it is necessary to ensure that the pressure-bearing capacity of the pipe of the buried pipe heat exchanger is 1.6MPa, and the pipe made of HDPE 100 with pressure-bearing capacity 1.6 MPa shall be adopted to ensure that its ring stiffness meets the external pressure-bearing requirements.
(2) The laying and backfilling of horizontal pipelines must be carried out in strict accordance with the following construction schemes:
It is necessary to lay a layer of fine sand equivalent to the pipe diameter at the lower part of the horizontal pipe of the ground heat exchanger in advance, and lay a layer of 200mm fine sand at the upper part after the horizontal pipe is connected and qualified in pressure test.
According to the construction experience of similar projects in the past, the buried heat exchanger pipeline can withstand external pressure after taking the above measures.
6. According to the progress plan provided by earthwork construction, horizontal pipe construction shall be carried out in different regions. When a loop or a system cannot be closed due to incomplete excavation, the reserved pipe head should be closed by hot melt, and the remaining wells or loops should be connected and closed after excavation, and then connected to the water collector.
7. Construction of 7.HDPE pipe passing through the bottom plate
(1) waterproof casing component prefabrication
A. waterproof casing is welded according to the design drawing of waterproof casing, and PE pipe in casing is installed.
B, a hole is reserved at the upper part of the shell. When installing HDPE pipe, install and tighten the rubber ring and short pipe at the lower part of the casing, and then pour resin mortar into the reserved hole.
C. After the casing and HDPE pipe are filled with resin mortar, plug the reserved holes with pipe plugs, and then install the upper rubber ring and short pipe.
D. During installation, the bottom flange and some short pipes under the concrete of the bottom plate shall be treated with anti-corrosion and painted with asphalt paint twice.
(2) waterproof casing parts installation
A. connect the u-pipes in each partition into a system according to the requirements of the drawings, and lead them to the coordinate position passing through the big bottom plate respectively. Accurately locate the position of the water collector and water separator, and connect the prefabricated waterproof casing parts with the pipe head of the horizontal pipe.
B. After all HDPE pipes are connected, calibrate the installed waterproof casing again.
C. After the basement floor construction is completed, it is connected with the indoor water collector.
8. Pressure test
(1) After the directly buried heat exchanger and header are assembled, the second hydrostatic test shall be conducted before backfilling. Under the test pressure, stabilize the voltage for at least 30 minutes, and the pressure drop after stabilization should not be greater than 3%, and there is no leakage. After passing the pressure test, continue to seal and maintain the system pressure.
(1) main pipeline connection and pressure test: after the pipeline connection and pressure test of each partition are completed, connect the water collectors of each partition to the main pipeline, and conduct the third water pressure test. The test pressure is 0.8MPa, and the pressure is stabilized for at least 2 hours without leakage.
9. Flushing, pressure test and others of underground heat exchange system
(1) Pipeline flushing and pressure test are the last two processes before concealment, and they are also extremely important links. Before cleaning, check whether there are reserved holes (such as connecting holes of pressure gauges) in the pipeline. ) No necessary sealing measures have been taken to avoid washing water flowing out and polluting finished products, semi-finished products and raw materials of other professions. The opening and closing of the valve shall meet the requirements of flushing, so as to avoid flushing water from flowing into the terminal equipment.
(2) After all piping systems are connected and installed, flush the system with water and exhaust. When cleaning, attention should be paid to connecting the discharged water to the nearest drainage well or drain ditch to ensure drainage and safety. The drain pipe is connected from the end of the pipeline, and the cross-sectional area of the drain pipe should not be less than 60% of the cross-sectional area of the flushed pipeline. Flushing should be carried out at the maximum possible pressure and flow rate in the system until the color and transparency of water at the outlet are consistent with the visual inspection at the inlet.
(3) After all system pipelines are installed, flushing, exhaust and backfilling are completed, the fourth water pressure test shall be conducted, with the pressure of 0. 1MPa, and the pressure shall be stabilized at the test pressure for 12 hours, and the pressure drop after stabilization shall not be less than 3%.
10. Add an automatic bleed valve at the highest point of the pipeline system and a manual drain valve at the lowest point.
1 1, backfill
After the pressure test is qualified, adjust the spacing and flatness of horizontal pipes first, and then notify the earthwork construction unit to carry out backfilling operation. During construction, the horizontal pipe is padded with sand layer with pipe diameter thickness, and the sand layer with thickness of 200mm is backfilled after connection. Then inform the construction contractor to carry out the next concrete cushion and bearing layer construction.
12, high density polyethylene pipe connection
hot melt connection
Hot-melt socket connection: it is a connection process that the outer surface of the pipe and the inner surface of the pipe fitting are simultaneously inserted into the mold of the welding device without rotating, heated for a few seconds, then the welding device is quickly removed, the heated pipe is quickly inserted vertically into the pipe fitting, and the pressure is maintained and cooled.
The connection process is as follows: check → cut the pipeline → clean the joint line → heat → dismantle the welding machine → align → insert the pipe fittings into the pipeline and correct → keep the pressure and cool.
A. The requirements and operation methods of inspection, pipe cutting, joint cleaning and marking are similar to those of UPVC pipe bonding, but the outer diameter of the pipe is required to be greater than the inner diameter of the pipe fitting to ensure the formation of a suitable flange after welding.
B. Heating: Insert the outer surface and the inner surface of the pipe into the mold of the welder at the same time, and heat for several seconds without rotating (preheating to the set temperature), with the heating temperature of 260℃ and the heating time subject to the technical specification.
C. Note: When the working environment temperature is lower than 0℃, the heating time should be extended by half.
D. Insertion: After the pipes and fittings are heated for a specified time, quickly pull out the fuser from the fuser mold, quickly find the correct direction, put the fittings into the pipe end to the scribing position, and correct them in time if any skew is found during insertion. Alignment and correction can use the line printed on the pipe and the four cross-shaped engraved lines at both ends of the pipe as reference.
E. Pressure-maintaining cooling: During the cooling process, pipes or fittings shall not be moved, and the next joint can only be connected after it is completely cooled.
V. Key points of supervision and control
1. According to the design drawings, strictly supervise the installation positions of differential pressure sensors and flow sensors to meet the control accuracy requirements of the system.
2. Strictly supervise the whole installation and debugging process of the user-side water system, heat pump unit and cold and heat source-side water system of the ground source heat pump control system, so as to control the two water systems and heat pump unit system at the same time and ensure the stable operation of the system.
3. All vertical buried heat exchangers are connected to the air conditioning room through horizontal connecting pipes to realize the circulation of groundwater system. In the process of construction, horizontal connecting pipes are not allowed to have vertical U-bends at the intersection of pipes, otherwise it will lead to difficulty in exhaust.
4, in strict accordance with the design drawings, supervise the buried depth and pipeline series-parallel mode, to ensure the best work of thermal circulation system and pipeline stress safety.
5. Hot-melt connection is often used for the connection between pipes. Hot-melt connection should meet the design and specification requirements, and the joint should be sealed without leakage. Operators of special operations must hold relevant certificates.
6. After the pipeline is laid, it shall be backfilled after passing the water pressure test. When backfilling, the pipeline should be filled with water.
7. The particle size of backfill material for horizontal pipeline should be uniform, fine, loose and dense.
8. According to the actual situation of on-site construction, when backfilling after the completion of pipeline laying, the pressure value of the pressure gauge of the backfill pump should be well controlled to ensure the compactness of backfilling and the heat exchange effect when the buried pipe is used.
9. Grasp the backfill quantity according to the pore size, depth, sediment and mud viscosity.
10. Strictly supervise the installation and debugging of the distributor and water collector of the underground system in the air-conditioning room.
1 1, strictly review the materials for approval, such as polyethylene pipes and horizontal pipes for buried heat exchangers, and
Materials entering the site and other kinds of materials to be used shall be submitted for re-inspection, which shall be strictly examined before leaving the factory.
All supporting documents, if necessary, should be checked by the supplier to ensure that all materials used are qualified.
12, installation and debugging of auxiliary heat exchanger and installation of accessories such as expansion tank and vent valve.
13. Supervisors witnessed various tests such as temperature test and water temperature test of underground pipelines, and recorded them in detail.