Performance comparison between PVC-M pipe and PVC-U pipe
PVC-M pipe has obvious advantages over PVC-U pipe in terms of safety, convenience and economy. It can effectively resist point load and uneven settlement of foundation, reduce the demanding requirements of construction environment, and is an energy-saving type. High impact, sanitary grade pipe products. PVC-M pipes are very suitable for use in water distribution projects due to their high performance and high safety.
First, performance difference detection
1. Determination of longitudinal retraction rate. Place the specimen of the specified length in an oven at 150±2°C for a specified period of time, measure the spacing of the markings before and after the sample is placed in the oven at 23±2°C, and calculate the longitudinal return according to the percentage change of the original length. Shrinkage. There are two main methods of measurement, one is the liquid bath test (the constant temperature liquid medium in the hot bath), and the other is the oven test (the heating medium is air). If there is no special requirement, the oven test method is generally recommended. This method is low in cost, economical and practical, easy to operate, and easy to control temperature. If you take the flat sample measurement method, you only need to put a layer of talcum powder on the plate to measure.
2. Determination of impact strength. The impact strength of PVC-U pipe is the maximum ability to withstand the impact load, that is, the ratio of the work consumed by the material to the cross-sectional area of the sample under impact load. According to the drop hammer impact method, the impact strength of PVC-U pipe is proportional to the temperature. The higher the temperature, the better the impact performance, and vice versa. The impact strength at 20 °C is nearly twice that at 0 °C. The impact performance of PVC-U pipes under low temperature conditions is significantly reduced, especially below 0 °C. According to GB/T 10002.1-2006, PVC-U pipe drop impact test (0 °C) TIR ≤ 5% (TIR is the true destruction rate).
3. Hydrostatic test. The hydrostatic test is a method of verifying the hydrostatic strength of a pipe with a specified hydrostatic pressure P. The test stipulates that for a given pipe, under constant annular stress, the pipe wall is not fully yielded at a certain temperature and time. Whether the PVC-U pressure pipe can pass the hydrostatic test depends mainly on the basic properties of materials and products, and the circumferential yield strength of the material is the most important one. If the hoop yield strength of the pipe can be accurately measured, it can guarantee the manufacture of pipes that meet the requirements of hydrostatic strength.
Second, the application difference in water supply engineering
(1) Safety aspects
1. PVC-M has excellent toughness and impact resistance. Taking dn200mm pipe as an example, the drop weight test is carried out at 0 °C, and the impact height is 2 meters. As a result, the mass of the hammer of PVC-M is 10 kg, and that of PVC-U is only 2 kg. This shows that the toughness of PVC-M is much higher than that of ordinary PVC-U pipes. Good toughness improves the impact resistance of PVC-M pipe, can effectively resist external impact during installation and transportation, and improves the resistance of pipe to external force. In this regard, PVC-M pipe 22 ° C, 20m fast impact test is the most convincing. After systematic comparison test, it was found that PVC-M was toughness damage after impact, and a small pit was punched out on the outer wall of the pipe. The pipe body was not damaged, but the PVC-U pipe test under the same conditions was broken.
2. PVC-M has good resistance to point load and crack resistance. PVC-U pipe has poor resistance to stress cracking. Stress concentration is often caused by poor laying, and brittle fracture occurs in pipe crack propagation, resulting in leakage and cracking of the pipe. PVC-M pipe can effectively resist external impact during transportation, handling and construction, and reduce safety risks, indicating that the performance of resistance to point load and environmental stress cracking is significantly improved. If it is inadvertently caused by slight scratches and scratches on the surface of the pipe, it will not affect the use of the pipe, which effectively ensures long-term, safe and reliable operation of the pipeline.
(2) Facilitation aspects
1. PVC-M construction tools. PVC-M pipe connection does not require special tools, such as hand hoists, tighteners, guide chains, etc. can be bought. In particular, small-diameter pipes can be constructed by the bar method or the hammer method. The installation of all specifications of the pipe can basically adopt an installation tool, and the construction machine is simple in principle and easy to maintain.
2. PVC-M construction process is small. PVC-M pipe is connected by rubber ring, the construction process is simple, easy to master, good detection, and high reliability of interface. In actual operation, only the working surface, the upper rubber ring, the brush lubricant, the counter insertion, and the feeler gauge need to be cleaned.
3. PVC-M construction speed is fast. The PVC-M is connected by a rubber ring. As long as the pipe is installed properly, the water can be passed immediately, and the interface time is short. Due to the simple construction tools, low cost, and light weight, it can be manually transported and installed. On average, a team can complete pipeline connections of more than 300 meters per day, greatly improving the construction progress.
(3) Economic aspects
1. PVC-M has low procurement costs and low investment. PVC-M has a rich source of raw materials and a low price. After detailed calculation, the cost of PVC-M is 20-30% lower than the cost of the same specification PVC-U pipe.
2. PVC-M has large inner diameter, good hydraulic conditions and low operation and maintenance costs. Under the same environment and location conditions, the water pressure of PVC-M users is significantly higher than other pipelines, which can meet the user's requirements for water pressure, thus ensuring the safety of water for more users.
3. PVC-M is light in weight and low in transportation and installation costs. Compared with the pipe of the specification, the weight of the pipe body and the design coefficient are different, and the weight of the PVC-M is the smallest, thereby effectively reducing the transportation, loading, unloading, handling, installation and the like.