Lightning Protection and Grounding Device Engineering Quantity Calculation


1. Calculation of the amount of equipment for installing a lightning rod

Lightning rods are installed on flat roofs, walls, structures, chimneys and metal containers.

1. Rated Unit①Installation of lightning rods on flat roofs, walls and chimneys is measured by "root" or "group". ②The installation of independent lightning rods is measured by the "base", and the length, height and quantity are in accordance with the design rules. (2) Processing and production of lightning rods with "root" as a unit of measurement.

(3) Lightning rods are installed in groups of three and measured in "groups". 2、Lightning protection net installation

(1) The lightning protection mesh is laid according to the laying along the seam plate support and along the concrete block, and the engineering quantity is measured in "m". The formula for calculating engineering quantities is as follows: Lightning protection mesh length = length calculated according to the size shown in the diagram × (1+3.9%) 3.9% in the formula - for lightning protection mesh up to turn, avoid obstacles and overlap First-class added value of length. (2) The production of concrete blocks is measured in "blocks", and the number of support clamps is taken into account, usually 1 per meter and 1 per half meter in the corner(3) Pressure equalization ring installation is measured in "m" Measurement ① When flat steel and round steel are used separately as pressure equalization rings, the engineering value is calculated based on the length of the center line of the ring beam to be grounded for pressure equalization. pressure, and the project of "laying equalizing rings" is being carried out. ② When the main reinforcement in the ring beam of a building is used as a pressure equalization ring, the engineering value is based on the length of the center line of the ring beam, which must be grounded in the design for pressure equalization. When the main rib is used, it can be adjusted proportionally. (4) The main reinforcement of the column is welded to the annular beam, measured by "place"

The number of "points" connecting the main reinforcement of the column and the ring beam is calculated in accordance with the design standards. Each location is considered as two main reinforcements and two ring beam reinforcements, respectively welded and connected. If there are more than two welded main bars and ring bars, they can be adjusted proportionally.

Lightning Protection and Grounding Device Engineering Quantity Calculation

2. Calculation of the installation number of down conductors (Construction) Laying the main reinforcement of the building structure, using metal elements for laying, etc. 1) Installation of down conductors is calculated in accordance with the height of the building on the construction drawing, measured in "extension meters", and in the norm includes the manufacture and termination of support clamps. The technical quantity of down conductor is calculated by the following formula:Length of down conductor=length calculated according to the size shown in the diagram×(1+3.9%)

2) Use the main reinforcement of the structure of the building (structure) as the down conductor installation: calculate the engineering quantity according to the following method.

When the main reinforcement in a column is used as the "bottom step", the quota is considered to be the welding of two main reinforcements measured in "m", and can be adjusted proportionally if more than two main reinforcements are used. 3) Manufacture and installation of disconnecting clamps is measured by "set". Calculate according to the number of disconnecting clamps installed according to the design requirements. Installation of disconnecting clamps in a surface manhole is calculated at the rate of one set per manhole.

3. Calculation of the amount of installation of the grounding deviceThe grounding device consists of a grounding bar and a grounding electrode. At present, the building grounding electrode uses a steel rod in the foundation of the building as the grounding electrode. , and the grounding bar is pulled out of the disconnecting clamp. Reinforcing bars or sheet steel are intended for spare grounding. 1) When installing an earth bar, the height of the breaking clamp is usually used as the starting point for the calculation of the bar, and the calculation is carried out before the earth post. Galvanized round steel, galvanized flat steel or stranded copper wire should be used as the material of the earth bar and should be measured in "long meters". The technical quantity is calculated as follows: Grounding bar length = length calculated according to the dimension shown in the diagram × (1+3.9%) 2) Installing the grounding electrode (1) Separate grounding manufacture and installation of the electrode. Take "root" as a measurement and calculate according to the quantity shown on the construction drawing. (2) Use the main steel rod as the ground electrode, take "m2" as the unit, calculate the engineering value according to the main dimension, and weld the down conductor to the main steel rod after passing through the disconnection. clamp. 4. Calculation of the engineering number of wires of ground jumpersA ground jumper is a connecting line that must be crossed and connected when there are obstacles in the ground bus, down conductor, ground electrode, etc., called a jumper. ZazThe resistance is measured in "centers". The quota for the installation of grounding jumpers includes three positions: grounding jumpers, frame grounding and steel-aluminum window grounding. 1) Earth bridges are commonly found in building expansion and settlement joints, rail-rail joints when crane rails are used as lightning wires, anti-static pipe flange connections, ventilation pipe flange connections, etc., as shown in the following diagrams ( a), (b) Calculation of "one place". 3) Grounding of steel and aluminum windows is measured "on site" (the construction of metal windows above six floors of high-rise buildings generally requires grounding), and the calculation is based on the number of metal windows that are grounded in accordance with design standards. (Glass Curtain Wall) 4) If other professional metal pipes need to be grounded when entering the house, the calculation is based on the number of pipes. 5) For connecting wires welded with metal pipes through boxes, trays, cabinets, boxes, etc., and connecting wires at the points of connection of pipe wires to pipe hoops, installation work is included in the norm, and the jumper is not counted. 5. Other issues1) The grounding device of lightning protection on the roof of a multi-storey building must be carried out according to the project "Installation of a lightning protection mesh", and the installation of a lightning protection cable of a cable support must implement the project "laying an internal grounding bus". 2) Debugging the grounding device

(1) Ground electrode debugging is measured in "groups". Generally, three ground electrodes form a group, which is considered a debugging group. If the grounding resistance is not in accordance with the requirements, a test must be carried out after adding the grounding body, and another commissioning fee may be calculated. (2) Ground grid debugging measured by "system". The ground mesh is formed by connecting several ground electrodes, and sometimes a large ground mesh consists of several groups. Typically, a subnetwork may consist of 10-20 ground electrodes. In real work, if it is difficult to calculate according to the subnet, it can be used as a test unit for every 50m of network length, and the engineering quantity can also be calculated as a network if it is less than 50m. If the project has rules, it can be calculated according to the design quantity.