DN-07b - Metallic mains drilling and tapping

• Conducted on

  Date

• Prepared by

• Location
  Address

• Operative being assessed

  Yes

  No

  N/A

• Uses the Voltstick prior to undertaking any work on any exposed metalwork to ensure it is safe to <br>continue and repeats when necessary

  Yes

  No

  N/A

• Ensures drilling / tapping is located at least 200mm away from any joint, fitting or existing tapping and <br>where there are no large corrosion defects or hard encrustations. Cleans the main by scraping and wire <br>brushing

  Yes

  No

  N/A

• Selects the correct size rubber saddle to fit to the drilling machine based upon the diameter of the main

  Yes

  No

  N/A

• Fits the drilling machine according to manufacturer’s instructions ensuring the drilling does not exceed <br>the maximum main tapping size

  Yes

  No

  N/A

• Applies a pressure test to 1.5 times the maximum working pressure in the main or 350mbar (whichever <br>is the greater) with the gate valve in the OPEN position and checks the machine seal using SGN <br>approved leak detection fluid to ensure no leaks are apparent

  Yes

  No

  N/A

• Checks the gate valve opens and closes with no restrictions, with the gate open lowers the drill and <br>spindle onto the main. Positions the ratchet onto the spindle and commences drilling

  Yes

  No

  N/A

• Drills the main taking care to avoid excessive force especially when using air powered tools and <br>continues to monitor the mains pressure

  Yes

  No

  N/A

• Taps the main manually and withdraws the spindle, retains in the raised position and closes the gate <br>valve

  Yes

  No

  N/A

• Vents any gas trapped in the drill head by pressing the vent button

  Yes

  No

  N/A

• Question - What action would you take if gas continues to pass when depressing the vent button?

  Yes

  No

  N/A

• Answer - The gate valve should be re-opened and closed to establish the seal, but if gas continues to pass then breathing
  apparatus should be worn when fitting the service tee

• Depresses the vent button and removes the drill head using the large spanner

  Yes

  No

  N/A

• Inserts the fitting into carrier spindle, tightens the gland nut hand tight and locates the fitting head <br>onto the body of the machine, keeping the gate valve closed

  Yes

  No

  N/A

• Opens the gate valve, lowers the fitting and screws into the tapped hole hand tight

  Yes

  No

  N/A

• Depresses the vent button until the pressure has been released, slackens the gland nut and removes<br>the fitting head in a similar manner to that of the drilling head, leaving the spindle attached to the <br>fitting<br>

  Yes

  No

  N/A

• Removes any swarf from around the fitting and tightens the lock nut until gas tight. Checks using SGN <br>approved leak detection fluid for leakage and removes any excess leak detection fluid

  Yes

  No

  N/A

• Removes the machine from the main

  Yes

  No

  N/A

• Question - What action is to be taken with all exposed metallic joints and fittings?

• Answer - Wrap with approved mastic tape (denso tape) with a 50% overlap

Sign off

• Name of assessor

  Yes

  No

  N/A

• Pass or refer for additional training

  Pass

  Fail

  N/A