1. How to distinguish pipe bends  

The difference between elbow, as the name suggests, is essentially the difference between "head" and "tube", but there is a great difference in the production process.  The basic difference is that the elbow is shorter than the elbow.  R=1 to 2 times is the elbow, and the larger multiple is called a bend.  In the production process, the cold bending pipe can be bent by the ready-made straight pipe bending machine, and the one-time completion is not needed for the second corrosion protection.  Elbow to custom, to do anti-corrosion, long order cycle.  The elbow price is higher than the bend but the cost performance is much higher than the bend.  

2. The materials of elbow elbow are cast iron, stainless steel, alloy steel, calcined cast iron, carbon steel, non-ferrous metals and plastics, etc.  There are direct welding (the most common way) flange connection, thread connection and socket connection, etc.  

3. Elbow symbol: SCHXX is the wall thickness grade, 90E (s) represents the short radius of 90 degree elbow;  90E (L) represents long radius 90 degree elbow;  45E (L) represents a 45 degree elbow with long radius;  45E (s) represents the short radius 45 degree elbow;  180E (s) indicates a short radius 180 degree elbow;  180E (L) represents long radius 180 degree elbow;  R (c) represents concentric reduction joint;  R (e) represents eccentric reducer joint;  T (s) denotes equal path tee;  T (r) stands for reducing tee;  Cr (s) stands for equal path four-way;  Cr (r) stands for reduced-path four-way;  C for pipe cap.  The classification method of elbow, according to its curvature radius, can be divided into long radius elbow and short radius elbow.  

A long radius elbow is a pipe whose radius of curvature is equal to 1.5 times the outer diameter of the pipe, i.e., R=1.5D.  A short radius elbow has a radius of curvature equal to the outer diameter of the pipe, i.e., R=D.  Where D is elbow diameter and R is curvature radius.  If divided according to the pressure level, there are about 17 kinds of pipe standards, which are the same as those of the United States, including Sch5s, Sch10s, Sch10, Sch20, Sch30, Sch40s, STD, Sch40, Sch60, Sch80s, XS;  Sch80, Sch100, Sch120, Sch140, Sch160, XXS, among which STD and XS are commonly used.  According to the Angle of the elbow, there are 45O elbow, 90o elbow and 180o elbow.  In this way, there are many types of elbows, and orders are often represented as follows: "LR STD 90o 8", for long radius, pressure class STD 90O 8";  Elbow;  For example, "SR XS 45O 4" denotes the short radius, and the pressure grade is XS, 45O 4";  Elbow.  

The maintenance method of elbow 

1.Long-term storage of elbow  pipe, should be checked on schedule, often on the exposed processing surface must be kept clean, remove dirt, neatly stored in a dry place in the room, is strictly prohibited to pile or open storage.  Always keep the elbow dry and ventilated, the retainer clean and tidy, in accordance with the accurate storage method.  

2. When installing, the elbow  can be directly installed on the pipe according to the connection mode and installed according to the position used.  Under normal circumstances, it can be installed in any position of the pipeline, but it needs to be easy to control the inspection. Pay attention to the flow direction of the elbow medium should be upstream from the longitudinal valve disc, and the elbow pipe can only be installed horizontally.  When installing the elbow, we should pay attention to the sealing property to prevent the leakage phenomenon and affect the normal operation of the pipeline.  

3. When the ball valve, globe valve and gate valve of the elbow elbow is used, it is only fully open or fully closed. It is not allowed to adjust the flow rate, so as to avoid the erosion of the sealing surface and accelerate wear.  The gate valve and the upper thread globe valve have an inverted seal device, and the handwheel is turned to the top position to tighten, which can prevent the media from leaking from the packing.