Installing modern piping connections during ongoing operations

The tapping method allows for the expansion of existing piping systems during operation, without interrupting the supply or requiring lengthy downtime. By using special tapping valves and equipment, new connections can be installed safely and efficiently while adhering to defined pressure and temperature limits. Compared to conventional methods, this process significantly reduces effort, costs, and time, and is therefore becoming increasingly important in network construction.

Traditional pipeline network upgrades are time-consuming and costly. First, the pipeline must be taken out of service and drained. Next, a section is cut out and replaced with a T-fitting, before the system is refilled and vented.

The tapping method is significantly more efficient. It allows for both smaller connections and larger branches during ongoing operation without interrupting the supply to connected consumers. As a result, this technique is becoming increasingly important in the consolidation and expansion of networks.

Tapping via a tapping ball valve. (© KÄHLER GmbH Industrie-Armaturen)

Applications
The system is primarily designed for liquid media. Use with other media is generally possible but requires individual consultation with the manufacturer. Typical applications include heating and cooling systems. Permissible operating conditions:

Nominal diameters: DN 20 to DN 200

Pressure: up to 25 bar

Temperature: −30 °C to +200 °C

The specified pressure and temperature limits for the valves used must be strictly observed.

Operating principle
During tapping, a tapping ball valve is welded onto the existing pipeline while it is in operation. A special tapping tool is then used to pierce the pipe wall through this valve, creating a new outlet. Technical regulations, such as AGFW Worksheet FW 432, contain binding guidelines for carrying out this procedure.

External hexagon with clear position indicator. (© KÄHLER GmbH Industrie-Armaturen)

Tapping valves
Various types of valves are used, such as threaded ball valves, threaded shut-off valves, or threaded clamps. In practice, threaded ball valves are the most common choice because they offer safe and convenient operation while also serving as permanent shut-off valves.

High-quality versions feature reinforced welded ends, multiple stem seals, and a full bore. A clear position indicator and defined 90° end stops increase operational safety and prevent operating errors. Variants with an extended stem allow for use without an additional shut-off valve, particularly in accessible areas.

Tapping machine
The drilling unit is screwed onto the previously installed ball valve and consists primarily of a housing, a feed unit, and a drill spindle. The latter has a multi-stage design and houses both the drill chuck and the drive. A hole saw with a center drill is used for drilling, and an integrated expansion spring prevents the cut-out pipe segment from falling out.

Sketch of a tapping device mounted on a ball valve and a medium pipe. (© KÄHLER GmbH Industrie-Armaturen)

By using various adapters, the device can be adjusted to fit different nominal diameters. It is powered by a drill that is connected directly to the spindle.

Preparing the drill hole
Before starting, all relevant parameters—such as the medium, pressure, temperature, material, and dimensions of the piping—must be determined. The dimensions of the planned branch must also be specified. Fire alarm systems must be temporarily deactivated during welding operations.

Drilling site. (© KÄHLER GmbH Industrie-Armaturen)

The threaded ball valve is adapted to the bend in the main pipe and welded on at a right angle to the pipe’s centerline. It can generally be positioned anywhere around the pipe, but not in the vicinity of existing welds. The joint must meet the required strength specifications.

After welding, ensure that no welding residues enter the valve. A functional test is then performed; the ball valve must be fully open for the tapping.

Adjustment of the weld-on end contour to match the main pipe. (© KÄHLER GmbH Industrie-Armaturen)

Installation and Adjustment
Prepare the tapping tool with the appropriate adapter, an intact O-ring, and a correctly mounted hole saw. The centering drill bit must have the specified protrusion. Lubrication of the spindle in the sealing area is required to ensure smooth movement.

After mounting on the open ball valve, the spindle is carefully guided to the pipe wall. The flush valve is opened, and a hose is connected to safely drain the fluid and drill chips. The drill is then mounted and properly adjusted.

Leak test
A leak test must be performed before drilling begins. During this test, all components—including welded joints and the equipment unit—are checked for leaks.

Implementation
First, the pilot hole is drilled at a constant feed rate until the pipe wall is penetrated. The speed is then reduced, and the main hole is drilled using a hole saw. Throughout the entire process, an open flush valve ensures that the chips are removed.

Illustration of the tapping tool after the centering hole (top) and after tapping (bottom). (© KÄHLER GmbH Industrie-Armaturen)

Once the procedure is complete, retract the drill spindle, close the ball valve, and secure it. A final check of the flush valve ensures that the fitting is tight. The tapping tool can then be removed, and the cut-out section of pipe can be taken out. The entire process must be documented in accordance with applicable regulations.

Illustration of the tapping tool after the centering hole (top) and after tapping (bottom). (© KÄHLER GmbH Industrie-Armaturen)

Summary

The tapping method allows for the expansion of existing piping systems without interrupting operations. Downtime, as well as the need to drain and refill the pipes, is eliminated. This significantly reduces the amount of labor and technical effort required, resulting in substantial savings in both time and costs.