Brian McKay of Topaz Inc. and Elaine Maruca of PLIDCO focus on safe pipeline repair and modification methods without shutdown. The document discusses hot tapping procedures which allow tie-ins and insertions into pressurized lines. Hot tapping involves using a machine to cut a coupon from the pipeline wall and insert a tapping valve without loss of pressure. It allows repairs, modifications and installations while the line remains operational.

1. Brian McKay, Topaz Inc., and Elaine
Maruca, PLIDCO®, USA, focus on safe
and reliable methods that facilitate
pipeline repairs/modifications without
system shutdown.
I
s it routine maintenance? Is it an emergency? Whatever the reason, operations
personnel do not take shutting down a system, for any reason, lightly. Time and
product lost in taking a line out of service, making the repair or modification and then
bringing the line back up, feels like pouring money down the drain. This is why, if the
project can be completed safely while the line remains in service, that is the option that will
be chosen every time. That is when hot tapping and associated procedures become practical
and cost-effective solutions.
You have no doubt heard of hot tapping before, whether you utilise the procedure
routinely or not. While the overall concept of hot tapping is not overly technical, the actual
procedures become a bit complex with the introduction of potentially hazardous products
under high pressure and at extreme temperatures. Let us look at a brief overview of the hot
tapping procedure and several scenarios where hot tapping can facilitate other maintenance
or repair tasks.

2. The basics
Hot tapping, sometimes called pressure tapping, cold tapping
or wet tapping, is a field machining process that enables tie-
ins to onstream pipe, tanks, or any pressurised gas or liquid
containing vessel. This is done without shutting down service
and without release or loss of product. Hot tapping also permits
the insertion under pressure of sensing or metering devices into
the flowstream, installation of permanent or temporary bypass
piping, and is the preparatory stage for line plugging (isolation)
operations.
A hot tap is accomplished by penetrating the vessel
wall within the confines of a tapping or branch connection.
This branch connection consists of a tapping fitting welded
or bolted to the vessel to be tapped. The fitting is usually
some variant of a self-reinforcing connection with attached
flange, a short flanged pipe nipple saddle cut to fit the
vessel, or a flanged full encirclement tapping tee. A tapping
valve is attached to the tapping fitting as a means to block
in line pressure once the hot tap is complete. Bolted to
and operating through the open tapping valve, the tapping
machine extends a shell cutter to the vessel wall, mills a
‘coupon’ out of the vessel the approximate diameter of the
branch ID, then retracts the shell cutter with the coupon back
through the tapping valve. The valve is then closed, pressure
is bled off the tapping machine and the machine is removed.
The tapping valve is now ready to receive the new branch
piping. When planning a hot tap, critical information must be
provided:
)) Size of tapping valve through which hot tap will be done.
)) Is the valve threaded or flanged? ANSI rating? (150#, 300#,
600#, etc.)
)) Nominal size, wall thickness and material of the line to be
tapped.
)) Product in the line to be tapped.
)) Operating pressure and temperature of the product.
)) Overall length of tapping nozzle and valve (distance from the
surface being tapped to the outside of the tapping valve).
Once onsite, and prior to beginning a tap, there are details
that the hot tap technician must address to assure the safe
and trouble-free completion of the hot tap. These details
include checking the tapping valve and nozzle flange alignment,
proper positioning of gaskets, assuring that flanged connections
are properly bolted, assuring that the tapping valve is a full
opening/full port valve with sufficient ID for clearance of
the cutter being used, and ensuring that no trash, bolts or
welding rods have been left or fallen into the tapping valve
or nozzle. Accurate measurements are taken and recorded to
enable calculation of the point at which the pilot drill and shell
cutter will touch the vessel wall and when the cutter will have
travelled far enough to complete the cut (Figure 1). Next, the
power source is connected to the tapping machine; the machine
can be powered pneumatically, hydraulically or by an electric
motor. The tapping machine is equipped with an automatic
feed mechanism and the technician monitors the calibrated
travel indicator continuously during the slow milling process to
assure that at no point does either the cutter travel beyond the
centreline of the tapping pipe, or that the pilot drill touches the
back wall of the pipe. Topaz Inc. in Houston, Texas, specialises
in hot tapping service work and they also sell several styles of
saddles including PLIDCO Hot Tapping+Saddles that bolt-on.
PLIDCO offers options including hinges, plated studs and nuts,
anodes, epoxy paint and integral clamp elements (Figure 2).
Tapping into a blind flange or a heavy wall
vessel
Hot tapping thick wall pipe, vessels and blind flanges several
inches thick is possible. There are, however, special issues that
Figure 1. Before connecting the power source to the hot
tapping machine, the Topaz technician confirms his calculation
at which the pilot drill should make contact with the vessel.
wall.
Figure 2. A subsea PLIDCO Hot Tapping+Saddle with integral
clamping elements, epoxy paint, plated studs and nuts,
anodes, lifting eyes and a hinge.
World Pipelines / REPRINTED FROM MAY 2015

3. need to be addressed in the design phase of the tapping branch.
This service requires special engineered solutions that address
specific challenges on a job-by-job basis. Topaz personnel can
work closely with the Engineering department at PLIDCO to
design what is needed for each application.
Hot tapping materials other than carbon steel
A pipe or other vessel needs to be hot tapped that is not carbon
steel. Can it be done? The answer is yes. Cement lined pipe,
transite, cast iron, stainless steel and other alloys, plastic and
fibreglass can all be tapped. It is critical to know the thickness and
composition of the lining, hardness of the alloy, and type of fitting
and valve through which the tap will be performed to insure that
proper equipment is selected and provided for the job.
Tapping into vessels at an angle
Now things start getting a little trickier, but are still feasible.
Tapping a radial surface like round pipe is common and presents
no special challenge, provided the tapping nozzle is installed
perpendicular to the vessel wall. There are times, however, when
the new piping layout requires tapping the vessel wall at an
angle other than 90˚. Angle taps like this require special tapping
equipment and tapping nozzle preparation, so contacting Topaz
before welding is important. Topaz has performed angle hot
taps up to 24 in. nominal valve size, at an angle of 45° maximum
off perpendicular (the centreline of the tapping nozzle actually
intersects the centreline of the line being tapped at 45˚, the
nozzle is not simply ‘rolled’ 45˚ off a vertical or horizontal
orientation). Utilising these same specialised tools and nozzle
prep, we can also make hot taps into the heel or backside
of short and long radius 90˚ ells. When bolt-on fittings are
required, they can be custom designed and manufactured at
PLIDCO to accommodate angle taps.
Hot tapping when a weld-on tapping nozzle or
tee is not possible
There are two types of hot tapping saddles; bolt-on and weld-on.
Hot tapping can still be performed in most situations where it is
not safe to weld in the area, when product and flow conditions
within the line make welding unsafe, or when the pipe and tapping
nozzle or tee is not a material that can be welded. In such cases,
a bolt-on fitting, such as the PLIDCO Hot Tapping+Saddle, can
be quickly and easily installed by bolting the two halves of the
fitting together using the provided torque specification (Figure 3).
As the two halves come together against the pipe wall, the
integral girdering of the fitting protects, and secures to prevent
displacement of the elastomer seals. PLIDCO engineers can design
custom hot tap fittings in special configurations and materials for
limitation of temperature due to seals where the standard PLIDCO
Hot Tapping+Saddle is not suitable.
Probe installation
Can appurtenances such as thermowells, flowmeters and
atomisers be installed while the line is in service and under
pressure? The answer is, in many cases, yes. Knowing the physical
design and dimensions of the device often enables adaptations
to be made to standard hot tapping equipment and fittings, and
permits positioning of the piece through the tapped hole into
the flow stream. Once it is installed in the set position within a
specialised fitting, line pressure is contained and the temporary
installation equipment can be removed. This allows unobstructed
access for attachment of instrumentation.
Plugging a line temporarily to do work
downstream
Line plugging is a method of temporarily isolating and bleeding
down a section of a pressurised system, for purposes of alteration
or maintenance within the isolated part. This is done without
Figure 3. A 6 in. PLIDCO Hot Tapping+Saddle being installed
in Italy.
Figure 4. This bypass system allows the flow of product to be
maintained around the isolated section while the work is being
done.
REPRINTED FROM MAY 2015 / World Pipelines

4. shutdown of the entire system and without loss of product. If
flow must be maintained despite the isolation, a bypass can be
installed around the isolated work section (Figure 4).
Line plugging fittings are also available in either a bolt-on or
weld-on style. A special line plugging variant of the PLIDCO Hot
Tapping+Saddle with a purpose built flange can be bolted on
the line and used in the line plugging process when welding is
not possible (Figure 5). Bolt-on plugging fittings include integral
clamping areas to prevent axial and torsional movement of the
fitting due to the inherent end force generated when the line is
plugged and the weight of the temporary tapping and plugging
equipment. These specialty fittings allow us to work through
temporary valves, which Topaz provides, during the plugging
operation. In very abbreviated terms, the procedure begins
by mounting the temporary valve on the special line plugging
fitting. After a hot tap is made, the line plugging tool is run
down through the tapped hole into the set position in the line.
The work section is blown down, and the repair or modification
work commences (Figure 6). If that scope of
work involves having Topaz cold cut a bad
section of pipe out to replace it with new pipe,
the PLIDCO Weld+End mechanical coupling is
a great product to consider. These fittings are
safety welding couplings used to quickly join
pipe so that flow can be resumed immediately,
keeping downtime to an absolute minimum.
When flow has been reestablished, the
Weld+End can be backwelded if you choose.
Welders and weld procedures should be
qualified in accordance with API standard 1104,
Welding of Pipelines and Related Facilities,
Appendix B, In-Service welding. No special
preparation of pipe ends is needed to install
the PLIDCO Weld+End. When the repair or
modification within the isolated work section
is finished, the line plugging tool is retracted,
and an o-ring sealed metal plug is secured in
the special fitting below the temporary valve.
Pressure is then bled off above the plug, the
valve is removed, and a blind flange is installed
on the fitting to complete the job.
If necessary, line plugging work can also be performed
through permanent valves and standard hot tap fittings. When
plugging through permanent valves, contact Topaz for required
bore diameters and overall fitting and valve dimensions prior
to welding. Information we require for line plugging services
includes:
)) Nominal size of the line.
)) Will the line be plugged on one end or both ends of isolated
section?
)) Material and wall thickness (schedule) of the line.
)) Product in the line.
)) Operating pressure and temperature.
Figure 6. Performing a cold cut in hazardous conditions is a safe and effective
technique used when torch cutting is not an option.
Figure 7. PLIDCO Shear+Plug being installed on a 16 in. line
containing 100% H2
S.
Figure 5. This PLIDCO Hot Tapping+Saddle with a purpose
built flange is being pressure tested to confirm a 100%
seal.
World Pipelines / REPRINTED FROM MAY 2015

5. )) Maximum possible pressure and temperature while line is
plugged.
)) Blow-down and equalisation provisions for de-pressuring and
re-pressuring of work section.
)) Size of bypass, if required.
)) Scope of alteration or maintenance while line is plugged.
)) Orientation of the line and required fitting orientation.
Plug a line permanently
You can use the same procedure above to plug a line permanently,
using bolt-on fittings when desired, with one small addition. You
would install a PLIDCO Flange+Coupling with a blind flange to
create a seal on the line after the cold cut has been performed.
It is common practice to back weld the fitting in place if the
scope of work involves pipeline abandonment or a reroute. This
procedure is common onshore as well as offshore. No matter
what the situation, PLIDCO will have a safe and reliable solution.
Facing extreme pressure and temperature
High pressure, high temperature lines often require a plant
shutdown because standard line plugging seals will not safely
withstand the extreme pressures and temperatures. A reliable
alternative is the PLIDCO Shear+Plug, which provides a safe and
reliable way to isolate the problem while keeping the system
running. The Shear+Plug provides positive metal-to-metal contact
with back up injected sealant. When conventional line plugging
techniques cannot stand up to extreme conditions, look to the
PLIDCO Shear+Plug alternative for 100% isolation (Figure 7).
REPRINTED FROM MAY 2015 / World Pipelines