abstract: glass fiber reinforced plastic pipe as a new type of pipe material, is widely used because of its characteristics. in use process due to pay attention to and solve some concrete problems failed to affect its marketing. this paper analyzes these problems and the solutions are put forward.
key words: glass fiber reinforced plastic pipeline; characteristics and problems; root cause analysis; solution.
mainly used in water supply and drainage pipeline engineering in china steel pipe, iron pipe, cement pipe, plastic pipe, such as glass fiber reinforced plastic pipe as a new type of tubing was gradually known by people. in recent years in recent years, with the glass fiber reinforced plastic pipeline and introduction and development of technology and equipment, has built a batch of glass fiber reinforced plastic pipe manufacturer in china, and in quite a batch of glass fiber reinforced plastic pipeline is adopted in water supply and drainage pipeline engineering. glass fiber reinforced plastic pipe has wide application prospects due to its characteristic prominent, but in use process because the performance of glass fiber reinforced plastic pipeline without fully understanding and well targeted to solve and affect the project quality, which in turn affect the application of frp pipes. the author according to the met problems when it is applied in glass fiber reinforced plastic pipeline in recent years were discussed and put forward the way to solve the problem, construction as a reference for similar engineering design.
1. the main characteristic of glass steel pipes
glass fiber reinforced plastic, also known as glass fiber reinforced thermosetting resin pipe. the existing glass steel pipe in our country, filament winding pipe sand inclusion tubes and centrifugal casting sand two kinds. tube is a glass fiber yarn filament winding sand, quartz sand and unsaturated polyester resin as the main raw material, by filament winding. centrifugal casting sand tube based on unsaturated polyester resin, short cut fiber and quartz sand as the main raw material, using centrifugal casting into legal system. glass steel pipe has the following main features:
1.1 product applicability
because of the characteristic of the frp pipe molding process, and make it easier to change the products specification and size, the factory under the condition of pipe products can be up to 4 m in diameter, can be up to 12 m length.
1.2 installation is simple and low cost
installation method is varied, can use flange connection, socket connection, bonding, and can easily realize between frp pipe, frp pipes and valves or other accessories, and between between frp pipes and other material pipe connection.
because the weight is lighter, don't need to use large hoisting equipment when installed, only by hand or light lifting equipment. due to pipe factory, joint counts and installation efficiency and lower cost.
1.3 light weight
proportion of glass steel pipe generally is 1.8 g/cm3, the tensile strength of 245 ~ 294 mpa, small specific gravity, high strength, internal pressure and pipe diameter under the same conditions, unit length of the glass steel pipe weight is only 1/5 of 1/5 of the carbon steel pipe, iron pipe, about half of the prestressed reinforced concrete, is easy handling, long-distance transportation and construction costs are low.
glass fiber reinforced plastic pipe products for air, water and general concentration of acid, alkali, salt and other media have good chemical stability, especially the water on the corrosion of glass fiber reinforced plastic is almost zero, corrosion resistant performance is good. don't need like metal pipe adopt strict internal and external coating and cathodic protection, basic don't need protection during the term of use.
1.4 good hydraulic characteristics
glass steel pipe has a smooth inner surface, the flow friction coefficient is small. glass steel pipe roughness coefficient is 0.0053 ~ 0.0053, and the concrete pipe is 0.013 ~ 0.014, the difference between 55% ~ 164%. for a flow and available water resources under the condition of same can reduce tube diameter, thus can save investment. at a flow rate and pipe diameter under the condition of same can save the delivery lift, reduce the operation energy consumption.
2. the common problems in use process and analysis
because the glass fiber reinforced plastic pipe has more than a number of characteristics and advantages, so get promoted and applied in our country, but in the application in the process of glass fiber reinforced plastic pipeline, often encounter some installation construction units and owners reflect some specific issues using glass fiber reinforced plastic pipeline, when the processing is not at that time, will cause the engineering quality accident, or difficult and time-consuming to processing, affect the overall social and economic benefits. the following a few common problems in the process of glass fiber reinforced plastic pipe used for analysis and put forward the way to solve the problem.
2.1 rock tube slot leakage of improper handling
grooves in the rock excavation is a common pipe buried geological conditions, when you meet the hard rock to hew flat at the bottom of the groove to the design elevation are not easy, will be affected by any carelessness caused local uplift and formation after backfill partial overload, the individual will tip frp pipe roof rock crack and even wear, resulting in leakage of pipeline.
this is due to the hardness of glass fiber reinforced plastic material is small, when it comes to the local rock ridges and individual pointed, tube slot backfill and other external load will make the whole section of stress transfer and focused on a local stress concentration resulted in damage to glass fiber reinforced plastic pipes.
solutions: one is in the rock excavation trench must be strictly according to the design elevation repair level off, can't appear local uplift or groove bottom rock tip; second is grooved backbreak 0.3 ~ 0.5 m first, and then uses the coarse sand in accordance with the design elevation leveling. 2.2 with the leakage of reinforced concrete pool wall connection place
reinforced concrete pool is the most common structures in water supply and drainage engineering, the connection between the frp pipe as a pool of water pipeline is taken for granted. often uses the embedded casing in the design of reinforced concrete pool ways to solve the contradiction between the civil engineering construction and pipeline engineering installation. design units in the design of tank commonly used while the embedded casing current national standard drawing s312, on the inner wall of the casing and the gaps between the frp pipe outer wall by packing tightly packed cured after connection to complete. but after project completed and put into operation in reinforced concrete pool wall and glass fiber reinforced plastic pipe connection place appear leakage and not easy to solve. this is because of the large reinforced concrete pool wall stiffness, and insert the frp pipe stiffness is relatively smaller, when the tank walls of glass fiber reinforced plastic pipeline under the action of external force separated easily and packing when the toroidal deformation and leakage.
solutions: one is to use steel flange short tube into the wall of the embedded pipe, glass fiber reinforced plastic pipe with flange again with a short pipe connection; 2 it is directly using steel flange after short tube with welding check water wing ring embedded in reinforced concrete pool wall, glass fiber reinforced plastic pipe with flange with a short pipe connection again.
2.3 pipe trench backfill material is undeserved cause leakage
pipe installation is complete and after testing qualified, pipe trench backfill are needed to restore the ground the rest of the function, the construction units often remove the pipe trench excavation of stone slag stone fill in the pipeline, when the backfill to pipe roof height above the began to use the machinery and equipment roller compaction, the individual stones acute angle insert frp pipe and cause leakage.
the reason is because of the glass fiber reinforced plastic material hardness is small, when stone acute angle to the glass fiber reinforced plastic pipes and its rocks back and standing up to the wall pipe trench, stones were rolling down the crowded move when frp pipes are easy to be stones corner wear. frp pipes and steel pipes, iron pipes or reinforced concrete pipe is different, they have enough hardness will not be stones corner wear.
solutions: one is the rock when the pipe trench pipe roof above 0.5 m below the trench backfill should be in soil, should not be within the trench dug out stone stone slag and then back into the pipeline, to avoid scratches glass fiber reinforced plastic pipeline; 2 it is to meet with general hard soil foundation trench should prevent foreign gushi rolled into the trench, or in the backfill soil mixed with hard rock.
2.4 and leakage of pipe connection place
glass fiber reinforced plastic pipe in the engineering practice and steel or cast iron pipe connection, in the connection place leakage is a common phenomenon, maintenance also work hard.
frp pipes and steel tube connection with glass fiber reinforced plastic pipe socket and steel pipes, frp pipe socket and the socket connection steel pipe socket connection, flange connection three ways. according to investigate, flange connection mode and glass fiber reinforced plastic pipe socket and steel pipe socket connection way excuse leakage phenomenon is very few, most leakage phenomenon appeared in the interface belongs to the glass fiber reinforced plastic garment pins and steel pipe socket connection way, the reason is two kinds of material of the pipe stiffness caused by different. commonly used in ordinary conditions of frp pipe stiffness using sn = 5000 or 10000, and the stiffness of steel or cast iron guancheng mouth is far greater than this value, pipe trench backfill, in under the action of external force, frp pipe before toroidal deformation, steel or cast iron tube joints occurrence crack of the back and water penetration.
solutions: one is to use flange connection mode and glass fiber reinforced plastic pipe socket and steel pipe socket connection in two ways; 2 it is in the last case using frp pipe socket and steel pipe socket connection, on the frp pipe socket end within 2 m with 180 �� plain concrete tube base, the rest of the section of tube to compacted backfill, the hierarchical compaction to the waist, to prevent the glass fiber reinforced plastic pipe in toroidal deformation under the action of external force. 3 it is possible using sn 10000 or greater stiffness of glass fiber reinforced plastic pipe products, reduce the cause frp pipe deformation caused by external forces an excuse to the possibility of leakage.
2.5 glass steel pipe itself defects caused by leakage
frp pipe is a new type of pipe material, has many advantages, but often met the owner units and construction units in the engineering practice reflect the quality of the glass fiber reinforced plastic pipeline flaws, mainly has: meet with toroidal deformation prone to delamination; when pressure testing tube wall appear sweat phenomenon; when cutting easy see structure layer is dense, loose tube wall; open air laid, pipe surface is rough, fading, peeling.
on the market at present in our country has a centrifugal casting sand and sand tube filament winding tube of the production of two kinds of glass fiber reinforced plastic pipeline. appear the phenomenon of the main reasons is a filament wound sand tube of the thickness of the isolation layer is thinner, usually less than 0.5 mm thick, under the condition of mass production gas cannot eduction, thin seepage prevention isolation layer is difficult to truly achieve anti-seepage effect, thus appears in the test tube wall back to sweat phenomenon; second, filament winding sand tube wall of a multilayer structure of sand core, toroidal deformation when the pipe and the tube wall by bending force is easy to produce delamination and the higher sand content, hierarchical trend, once the pipes appear statified phenomenon, it shows that the strength of the structure of the tube body is destroyed, it is not suitable for continue to used as a pressure pipeline; three is in the process of production of quartz sand were wrapped in free fall form falling between fiber layer, uneven sand quantity of this process, tube wall loose, easy to cause delamination; four is glass fiber reinforced plastic pipe in the open air under the condition of installation, long-term by ultraviolet irradiation, pipe surface is rough, fading, peeling.
solutions: one is using underground laid as far as possible to avoid laying under the condition of glass fiber reinforced plastic pipe in the open, or take appropriate measures to glass fiber reinforced plastic pipeline not to direct exposure to the sun's ultraviolet rays. the second is using centrifugal casting sand filling tube. because of centrifugal casting sand tube wall usually a multilayer structure, can according to the need to enhance seepage, transition, isolation, increasing the rigidity of the center layer and different role, such as lining layer layer design, the thickness of the lining layer according to the need to make sure that the wall under the action of suppression and become, in a larger centrifugal force is very dense, solid, no delamination, no pores. it to a wall of h beam structure, strong resistance to bending force, high rigidity. on the market at present most of the sand production is the filament winding tubes, there are many defects in product quality aspect, should gradually improve the market share of the centrifugal casting sand filling tube, engineering quality will be improved.