Plastic pipeline flange connection, bolts play an important role
The bolts are widely used in the pipeline industry. The flange connection needs to be used with suitable bolts. Choosing the right bolt plays an important role in connection and leakage.
What are the categories of bolts?
All threads meet the requirements of Asme B1.1.
Convenient to separate flange for maintenance. The joints that often need to be separated are often separated, including hole boards, glasses boards, pads, sieve nets and landing line axons. The design of the pipeline layout should make the flange be separated without too much force. The top lift screws should be installed on both sides of the pipeline. For holes, the lifting screw should be installed at 3 o’clock and 9 o’clock. When using a flange separator, no jack screw is required.
Choice of bolt:
Select according to the corrosiveness of the use of temperature and environment.
The length and size of the bolt:
The length and diameter of the bolt are determined by the flange standard used.
The bolt should be represented by diameter. The length is in millimeter, and the four houses and five enter the closest 5 mm.
Flat pads: In special cases, on the insulation flange and the nuts of plastic flange, the flat pad ring is needed under the nut.
Belleville Circle: For the maintenance temperature of cycle maintenance and bolts above 450 degrees Celsius, Belleville Circle Circle
The materials used for process and basic services should be ASTM A193 B7 -level bolts, and have ASTM A194 2H nuts. The suitable temperature range is negative 20 to 450 degrees Celsius.
The materials used for low -temperature services should be as follows:
1. The operating temperature range of the bolt is negative 18 to negative 101 degrees. The ASTM A194 Grade 4 or 7 with ASTM A320 L7 and Astm A194 Grade 4 or 7 should be used. C.
2. ASTM A320 L7M -level nut and A320 7M -level nut can be used for low -temperature environments with negative 18 to 73 ° C.
· The working temperature range of the bolt is negative 101 to 195 degrees. It should use a nut that conforms to the ASTM A320 B8 level and a nut that conforms to the ASTM A194 8. C
Medium -high temperature service material:
1. ASTM A193 B7 or B7M -level nuts, with A194 7 or 7M -level nuts, can withstand 450 degrees of high temperature. C.
2. ASTM A193 B16 -level double -headed bolt with A194 7 nuts, suitable for working temperature of 450 to 510 degrees. C.
When the spiral wound pad is used for high temperature, the bolt must provide sufficient stress to make the pads in place.
1. When the B8 2 bolts are used for the temperature of more than 650 ° C, a fixed padding ring is required to use the strain hardening bolt. The winding of high -temperature pads is likely to be 347 or chromium nickel iron alloys.
2. At a temperature of more than 650 ° C, the reaction hardening will anneal. As long as the connector is not broken, the antidium bolts have sufficient strength to fix the connector.
1. When the bolt is connected as follows, the standard quenching and ignition of the standard quenching and ignition ASTM A193 B7 B7 double -headed bolt should be used for acid wet operation:
2. Not directly exposed to hydrogen sulfide
3. Not buried or insulated
4. No French protector, or not directly exposed to the atmosphere.
5. Under the same conditions, you can use ASTM A320 L7 -level double -headed bolts with a level 4 or 7 nut.
Under the following conditions, nuts that meet the ASTM A193 B7M and A194 2HM -level nuts should be used.
1. Directly exposed to an acidic environment
2. When the bolt will be buried or insulated
3. When the flange protector is installed on the flange, it cannot be exposed directly in the atmosphere.
4. You can use the ASTM A320 L7M -level bolt and 7m -level nuts under the same conditions.
· Mechanical bolts:
Steel mechanical bolts that comply with ASTM A307 B can be used in plane cast iron or non -metallic flanges in a acid -free environment. The nut should meet the ASTM A563 D level. The combination of this bolt and nut can be used under acidic conditions without sulfurization. The system is also applicable when the “weak” bolts are specified to avoid flange overload. This bolt can be galvanized.
· Swelling and contraction:
When the fluid temperature is lower than negative 45 degrees. C, the selection or bolt design of the bolt material should include the contraction difference between the flange and the bolt, so that the changes in the seat pressure of the pad will not cause leakage.
Product Recommendation: china flange lock nut