Abstract: groove clamp pipe connection technology in our fire protection system has been widely used, with the flange and welded construction technology, compared with a reasonable structure, high strength self-sealing, long life, flexible connecting pipes are the advantages of the state, and installation and maintenance simple, convenient, high in the fire to promote the value of the pipeline.
Keywords: clamp, flexible, pipe connections, sealing gasket
With the rapid development of China s construction industry, large-scale fire is widely used pipe, pipe materials generally used in galvanized steel. Galvanized pipe with a corrosion-resistant, easy to transport contaminated media advantages. However, for pipe sizes DN ≥ 100 galvanized pipe, the threaded connection is difficult to meet the pressure requirements, and construction difficult. For pipe sizes DN> 150 pipe is often used welding. Before the old methods of pipeline construction welding construction, flange; and number demolition, to a second galvanizing plant; and then sit in the right connection. As a necessary extension of the construction period, an increase of construction costs. Galvanized pipe clamp manufacturers connection in recent years, building systems commonly used in a domestic connection, its construction method overcomes the difficulty sets of wire, galvanized welded the second issue, which has the advantages of convenient installation and maintenance, the current pipeline construction on the lot is promoting the use of fire.
1, the groove forms clamp the basic structure and working principle
Groove in the pipe clamp is a clamp ring card slot, to ensure that the pipeline by the axial tension is not sufficient to be opened, only two bolts to tighten the clamp, compared with the flange fastening simple , convenient and reliable. Connection with the groove tube clamp, pipe end directly to the general left 2 ~ 3mm clearance, pipe a small amount of axial displacement can be guaranteed. Take over the gap is sealed by the rubber ring was pressed to achieve the structure shown in Figure:
Grooved pipe clamp works into the C-medium rubber ring, the use of media to make their own rubber ring compression pressure in the pipe coupling cavity, to ensure sealing, rubber ring size slightly larger than the other pipe bands and the formation of empty pipe chamber, bolt tightening, the rubber ring is further squeezed, sealing effect further strengthened.
2, groove clamp pipe connection characteristics:
2.1 reasonable structure, strong high by
Working condition is equivalent to groove clamp pressure vessels, transmission medium axial force borne by the clamp bolt to bear radial force, due to the limited radial width of clamp force is much smaller than the axial force. Flange, the bolts bear all of the axial force and gasket compression force.
2.1 a good seal
Sealing groove clamp, mainly through C-ring to achieve, can form triple sealing. When the clamp is not installed by first forming dense rubber ring seal; clamp installation, clamp the rubber ring is further compressed to form the second seal; when the pipe into the rubber ring of the C medium cavity, reaction in the rubber ring sealing lips, increasing the sealing lips, the formation of self-sealing. According to a survey, grooved hoop connected to the system leakage rate of about 1%, well below the threaded connection.
2.3 installation and maintenance quick and easy
Groove clamp can be installed just a wrench, do not need to cut and weld, saving a lot of ancillary workload and costs. By removing the steel cable clamps, you can easily replace the maintenance, especially local maintenance, just need to release the two clamps to repair any section of pipe out of pan to prevent removal of pipe threaded connections require a lot of welding to be cut in order to repair the problems.
3, groove clamp analysis of technical performance
3.1 Pipe wall thinning on the impact pipeline pressure
Groove clamp connection of pipes, pipe through the wall of the trench after extrusion machine will be thinning, after thinning the pipe whether there is a greater use of performance changes, it is of great concern. After rolling, based on multiple measurements of the pipeline, the pipeline for different groove depth is generally 1.6 ~ 2.7mm, thinning rate of about 8%.
For galvanized steel pipe DN50 ~ 150 roll tank, the pipe roll groove at the minimum wall thickness shown in Table 1, according to the following formula to calculate allowable pipe pressure, there is evident in Table 1, the pipeline s operating pressure is much smaller than the pipe Yun-bearing pressure, so do not affect thinning galvanized steel tube construction the normal use of fire.
P = (1-C)? Δ / D × 200? [Ε]? Φ
Where: P - pressure pipes allowed (MPa)
C - the additional amount of pipe wall thickness (mm)
D - pipe diameter (mm)
δ - thickness after thinning rate (%)
[Ε] - material allowable stress (fkg/mm2)
Table 1 roll groove pipe pressure after
3.2 pipe diameter to reduce the impact resistance of the pipeline system
Galvanized steel tank in the roll, the roll groove area of ??the pipe diameter to reduce the loss of resistance is also worth noting, was the scene of the roll reduction tank diameter was measured after the calculations, after the roll groove pipe diameter to reduce the rate of about 5 percent of its resistance: a 90 ° elbow used to increase channel resistance of 0.3 to 0.4, groove clamp connection piping resistance of about 0.02, accounting for bend resistance of 5 to 6%, and therefore the whole system, groove clamp connection on the system resistance has little effect.
3.3 Cost Analysis groove clamp connection
Grooved pipe coupling to connect the price of the initial investment in fire protection systems have a certain influence, resulting in increased investment. Score using groove clamp connection flange segment investment is high, but the groove clamp connection to reduce the cost of secondary zinc, in the whole project cost close connection with the flange. Considering the post-maintenance, high overall efficiency groove clamp connection.
4, the groove processing requirements
Because the characteristics of groove clamp connections, clamp connections is lower than the strength of weld strength and location of the pipe clamp, there are two free-end, so connections are the weakest link in the pipeline. During the construction process can pass in the pipeline trench outside the wall processing is one of the key groove clamp connection, the interface may cause leakage or even slipping accidents. Conduct a roll groove pipe in strict accordance with specifications, in line with the following table:
5, the construction should pay attention to the problem
Galvanized steel pipe clamp groove connection of national technical specifications and construction acceptance is lagging behind, to the construction and supervision difficult. Roll groove quality good or bad, is a key factor affecting clamp connection, the construction should be strictly in accordance with standard construction. Groove clamp connection purpose is to protect the zinc coating, roll groove in the process of destroying the zinc coating will accelerate the corrosion of the pipeline should be protected. Groove clamp connection with a certain flexibility, to prevent pipe deformation at the interface during the pressure test, pipe supports layout should be reasonable.
Although the groove clamp connection in actual use there are some problems, but its advantages are obvious, easy construction, high efficiency, no open flame and so on. As technology continues to improve, groove clamp connections will continue to promote the actual use of the process used.