Flange

A flange is a method of connection pipes, valves, pumps, and other equipment to form a piping system. It is the second and most connection after welding. Flanges provides easy access for cleaning inspection or modification.

Flange Classified :

1- Flange Type 

2- Flange Face 

3- Size 

4- Schedule 

5- Pressure-temperature rating 

6- Material

FLANGE TYPE :

1) Weld neck Flange:

Easy to recognize because of the long-tapered hub. It is the most widely used in process piping. 

• Used for high pressure and high temperature application 
• Decrease the high stress concentration at the bottom of the flange. 
• Used in all pressure class

2) Slip on flange :

The flange slip over the pipe and welded with two filets welds on inside and outside of the flange. It has short service life compared to weld neck flange.

3) Socket weld flange :

This flange is attached to the pipe by a filled weld. The flange has a socket, so the pipe is inserted and fits on the sockets.

• Can be used in high pressure system.
• A high skilled welder is required. 
• There is an expansion gap that is must be 1/16” to prevent residual stress.

4) Threaded Flange :

It has a female thread, so it’s connected to a male thread. Unlike other flanges, threaded flange is connected to the pipe without welding. It is used for low temperature and low-pressure applications.

5) Lap Joint flange :

This flange consists of two parts, which are stub end and the flange. It is used for low pressure applications.

Scraping of PE pipe

1.  During scraping the outer oxidized layer of pipe gets removed and the clean surface is available for Electrofusion jointing. 
2.  Wipe pipe ends using clean, disposable, lint free material to remove traces of dirt mud, etc. Pipe ends may be washed with clean water if necessary and dried with the lint free material. Ensure pipe end is completely dry before proceeding. 
3. Mark the area +50 mm beyond the fusion area. 
4.  For socket fitting measure the depth of penetration of the fitting by placing the socket of the bagged fitting alongside the pipe end and put a witness mark on the pipe at half the fitting length (i.e. Center Mark) to indicate the area to be scraped. Do not remove the fitting from its packaging at this stage. 
5.  For Saddle fitting mark the area for scraping by putting saddle on pipe without removing the packing. 
6.  Carefully scrape the whole circumference of the pipe in axial direction over length using a rotary / hand scraper 
7. When rotary scraper is used, no second scrapping must be performed. 
8. Wipe the scraped surface with an authorized Isopropanol impregnated pipe wipe or with isopropyl alcohol (IPA) & tissue paper for degreasing the scraped area or soiled fittings. 
9. Mentholated spirits, acetone, methyl ethyl ketone (MEK) solvents are not recommended for wiping the scraped surface. Ensure the prepared surfaces are completely dry before proceeding.

For Good practices 

a) Always Mark the area to be scraped before scraping. 

b) Use a mirror to inspect while scraping the underneath pipe surface.

c) While scraping remove the entire surface of the pipe over the area indicated, to a depth of approximately 0.3mm. 

d) Pipe must be scraped so that shavings of uniform thickness are formed.

 e) Remember to de-bur the pipe ends after scraping. 

f) Do not touch the prepared pipe surface. 

Procedure For Electrofusion Tapping Tee

1.  Scrape the necessary pipe surface as per above Mechanical Scraping procedure for saddle type fittings.
2.  Remove the fitting from its packaging and check the matt of the fitting is clean. Do not touch the fusion zone of the fitting or allow it to be contaminated.
3.  For fusing tapping tees correctly, sufficient amount of top load should be given properly on fitting. 
4. Top loading clamp suitable for different diameter range can be used. This clamp can load saddle on to pipe for required load. 
5. Top loading saddle clamp are light weight for easy transportation on site & are suitable for pipe dia. Up to 500mm. 
6. Degrease the heating mat with cleaning fluid IPA and white tissue paper. Now fit the tapping tee on pipe with its top attached to the spring of top loading clamp. Tighten the Knob (hand wheel) of clamp until the adjusting spindle (indicator rod) is flush with the top surface