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Hot Tapping

The hot tapping procedure is a means of permanently adding an outlet to an existing system without disruption of service. The O.D. of the existing line and the operating pressure shall be submitted to the offices of Allied Flow Specialists, Inc. (AFS) at the time of scheduling. Prior to the welding of the assembly, the pipe coating is removed and the pipe is cleaned. The weld fitting is set and leveled on the existing pipe where proper fit is then checked. Both sides of the fitting should be tacked so the fitting will not be pulled to one side and will stay uniformly straight. A minimum of three passes is required to fill the bevel, not including the root pass. (Only the outside of the fitting is to be welded).

Once welding is complete the fitting shall be allowed to cool for approximately 15 minutes. The appropriately rated valve for the existing line pressure is then installed. Prior to installation of hot tapping equipment, the whole assembly is pressure tested with air and is sprayed with a solution of soapy water to check for leaks. Once it is determined to be a qualified weld, the hot tapping equipment is then installed and another pressure test is performed to verify our equipment is air tight. When tapping natural gas lines, a nitrogen purge shall be installed with valves (in the off position) on the entering and exiting sides of the head. During tapping, the pilot drill penetrates the line and its contents enter the head and will remain there throughout the tap. When the hot tap is completed the “cookie” or cut portion of the pipe, which is normally retained by the pilot drill wires, is lifted out and the valve is closed.

When tapping natural gas lines the nitrogen purge is turned on and both valves on the head are opened and the purging of the head is begun. After no natural gas is detected from the exiting purge hose, the purge will be halted and hot tapping equipment will be removed. The valve is now ready to be used for the branch connection.

Fire Safety and Emergency Shut Down

Prior to tapping natural gas lines AFS replaces all o-rings with new o-rings to ensure a safe air tight tap will be performed. AFS strongly urges the customer to locate and make accessible shut off valves serving the pipe being tapped. All fire safety equipment, welding permits and fire watch personnel shall be provided by customer, or those at his direction

Hot Tapping

AFS hot tapping services include tapping 1/2″ to 54″ on natural gas, water, sewage, steam petroleum products, and chemicals.

A. Saddle or weld nozzle installed, valve installed, assembly pressure tested and tapping machine attached.

B. Valve opened, hot tap completed, coupon or cut portion retained by latches on pilot drill. Pressure is contained within tapping machine.

C. Cutter retracted and valve closed. Fluid is drained and tapping machine removed. The tapped valve is now ready for the contractors tie-in.


  • Commercial Buildings
  • Hospitals
  • Manufacturing Plants
  • Hotels
  • Power Plants
  • Schools
  • Airports
  • Water Treatment Plants


  • Copper
  • Carbon Steel
  • Stainless Steel
  • Cast Iron
  • Coated and Lined Pipes
  • Aluminium Alloys
  • Nickel Alloys
  • Plastics


  • Chilled Water Lines
  • Domestic Water Lines
  • Condenser Lines
  • Hydraulic Lines
  • Heating Lines
  • Sprinkler Lines
  • Boiler Water