Construction steps of a garden automatic sprinkler irrigation system project

The general requirements for the construction and installation of landscape sprinkler irrigation systems are strict adherence to the design. Any modifications to the design must be approved by the design unit and the competent authority beforehand. The construction technical standards of this project's sprinkler irrigation system shall be implemented in accordance with the "Construction and Acceptance Specifications for Water Supply and Drainage Pipeline Engineering" (No. CB 50268-97), issued and implemented by the Ministry of Construction in 1998.

Construction sequence: Sprinkler system construction planning → Material preparation → Measurement and line setting → Trench excavation → Main pipeline installation → Branch pipeline installation → Installation of control valves and other components → Backfilling of trenches → Pipeline flushing → Installation of quick-take valves → Testing and adjustment → Inspection and acceptance for commissioning.

1. Trench Excavation

(1) According to the pipeline center line, measurement and line setting are conducted. Different stake numbers are clearly marked at branch lines, sprinklers, gate valves, etc. Trench excavation is mainly done by a trenching machine, supplemented by manual labor. The main pipe excavation depth is 1200mm, and the minimum trench width should be greater than the pipe diameter by 300mm. The branch pipe excavation depth is 800mm. At the junction of the main pipe and branch pipe, a gradual slope is used to ensure they are on the same plane. At intersections with other pipelines, manual excavation is used.

If the sprinkler pipe trench has a significant sudden fluctuation in some areas, the trench bottom should not have a large fluctuation during excavation. It is required to excavate deeper at the raised ground to reduce the fluctuation of the bottom of the pipe, ensuring smooth pipeline and extending the service life of the pipeline.

(2) Trench Cleaning

During trench excavation, a designated person is responsible for protecting the on-site line marking to prevent loss and ensure that the markings are not moved arbitrarily. The location of markings after excavation should be consistent with the line setting results. Before pipe installation, hard and sharp debris at the bottom of the trench should be removed. The cleaning principle is manual cleaning, to make the trench as flat as possible, removing larger and harder soil blocks or stones.

(3) Fine Sand Bedding at the Bottom of the Trench:

If there is a lot of garbage and debris in the trench, fine sand should be laid at the bottom to protect the pipeline. The thickness of the sand layer is approximately 100mm. The sand should be free of large stones or pebbles. The sand should be laid as centrally as possible in the trench, approximately 500mm wide for the main pipe, and approximately 300mm wide for the branch pipe.

2. Pipeline Laying

The laying principle is basically in accordance with the drawings, with minor adjustments allowed locally. The main and branch pipes are connected using a socket joint and a rubber ring seal. 45° and 90° cast iron elbows are used for the main pipe at corners.

The 45° and 90° elbows and other fittings used for the branch pipe are UPVC fittings. Before installation, the Size on the construction drawings must be checked against the pipe diameter delivered to the site. Check the materials for any quality problems, such as pipe cracks, dents, bends, rubber ring defects, etc. Materials with quality problems are prohibited from use. Protective measures, such as making cast-in-place concrete piers, must be taken for the elbows and fittings on the main pipe.

The elbows and fittings on the branch pipe use glue joints. The area must be securely padded to protect the pipe and fittings. The main pipe and branch pipe are connected using a water divider saddle. The connection between the branch pipe and the elastic connecting rod uses a reducing tee, and the sprinkler height is adjusted through the elastic connecting rod. Pipelines passing through roadways must use sleeves of appropriate Size and other effective measures to increase the compressive strength of the pipelines in the road sections to meet the design requirements.

3. Construction of Sprinkler Automatic Control Line Laying

Determine the location of the control station according to the drawings. After the main water supply pipe is laid, lay the signal line along the trench according to the design drawings. All lines should be marked with numbered pipes according to the solenoid valve numbers in the drawings for easy connection and maintenance. The power supply for the satellite station comes from the pump room, and a 220V power line RVV3x2.5 is laid along the water supply main pipe. The wire joints are crimped with crimping sleeves, then soldered, and insulated with waterproof self-adhesive tape.

4. Backfilling of Trenches

Backfilling must be carried out after all concealed works have been confirmed by the supervisor and the pipe watertight test has passed. The pipe foundation concrete must also reach a certain strength. The backfilling sequence should be done layer by layer from high to low in the direction of trench drainage to ensure smooth drainage. Backfill both sides simultaneously and compact evenly to prevent pipeline displacement. Backfill around ancillary structures such as inspection wells simultaneously.

When the water content in the soil is too high after rain, backfilling should be avoided as much as possible. The backfilling height should be coordinated with the construction of the inspection wells to prevent mud and water from flowing into the wells. When the soil is backfilled to the ground level and the inspection well has not yet been covered, an earth embankment should be made around the well mouth, and should be 20cm above the ground.

During backfilling and compaction, there should be no accumulated water in the trench. The soil should be compacted in layers, with each layer not exceeding 20cm in loose thickness. The optimum water content should be maintained. If the soil is too dry, water should be added appropriately. If it is too wet, it should be dried or replaced. Use a small rammer to compact it to meet the density requirements.

The section within 50cm of the top of the pipe should be strictly controlled. The Size of the backfill material should be within the specified range. Large rollers should not be used for compaction; manual compaction should be done with wooden rammers. Above 50cm of the pipe top, use a frog-type rammer to compact in layers. The loose thickness of each layer should not exceed 20cm, and the optimum water content should be controlled. If the soil is too dry or too wet, water should be added or sun drying should be done respectively, to meet the required density.

5. Quick Water Take-off Valves

To facilitate temporary water intake or manual irrigation of corners that are difficult to control with sprinklers, a certain number of quick water take-off valves are generally installed on the main pipe. These quick water take-off valves are used with matching keys. Inserting the key automatically opens the valve to supply water; to stop watering, simply remove the key, and the valve will automatically close.

6. Inspection

After completion of the pipeline installation process, before formal use, pipeline flushing and water testing are carried out: This flushes away any residual mud and sand from the installation process and checks for leaks and whether the sprinkler range meets the design requirements. Pressure testing should be done in sections. Before pressure testing, the pipeline should be fixed, the pressure gauge should be installed, and work on the pressure pump and air release valves should be completed. After the pressure test is passed, the contractor and the owner's representative will jointly inspect each completed hole, and sign off on the completion of the sprinkler project in writing before handing it over for use.

7. Watertight Test

Conduct a water closure test according to the requirements of the design and supervisory engineers to check whether the water seepage of the pipeline and inspection wells is within the specified allowable value. First, block the inlets of the downstream and upstream inspection wells of the test section pipeline. Blocking is done using brickwork and cement mortar. Then, use the upstream inspection well for water closure; water is injected from the upstream well into the test section. After the section is full of water, soak for 24 hours to allow the pipe wall to fully absorb water. Allow the water level to stabilize; the test water level should be 2m above the top of the upstream pipe. If the height from the top of the upstream pipe to the inspection well opening is less than 2m, measure the water level drop height, calculate the actual water seepage, and compare it with the allowable water seepage. If it is less than the allowable value, the test is qualified; if it is greater than the allowable value, the cause must be checked, the problem identified, and handled.

If the seepage is not easily visible, add some red pigment to the water to make the location of the seepage visible for easy handling. Then, conduct the water injection test again until it meets the specification requirements.