Low Pressure Hot Tap Assemblies - ABB TB404 Operating Instruction

SAFETY CONSIDERATIONS
WARNING
PROCEDURE
W1
SAFETY CONSIDERATIONS
PR3 - 2
1. Always use the sensor guide when using the high pressure
hot tap assembly. The sensor guide is a tightly toleranced 1½
in. NPT nipple that prevents adverse play between the insertion
rod and the sensor guide. Adverse play could damage the
insertion rod and injure personnel.
2. Never stand directly behind the insertion rod upon pressur-
ization. If the insertion rod is not fully retracted upon pressur-
ization, it could rapidly reach the blow out protection of the
sensor assembly and severely injure personnel standing too
close behind the insertion rod.
Two types of hot tap assemblies are available: Low pressure units with either
hand or wrench-tight compression fittings and high pressure units. The high
pressure hot tap assemblies can be ordered with ball valves. A ball valve
must be ordered separately for low pressure hot tap assemblies.
For a low pressure hot tap assembly without a ball valve, valve sizes are lim-
ited to a minimum throat diameter of 1½ inches (e.g., 1½-inch full port,
two-inch regular port, etc.). Since mating hardware requires 1½ in. NPT
threads, ball valves greater than 1½ inches require a reducing bushing.
When using high pressure hot tap assemblies, a 1½-inch full port ball valve
is required. This is to maintain the proper insertion length for the sensor and
the correct positioning of the insertion rod guides with the 1½ in. NPT sensor
guide.
Sensors purchased through nomenclature with the hot tap hardware included
are shipped fully assembled and only require installation into a 1½ in. NPT
female receptacle followed by connection to the toroidal analyzer or trans-
mitter. Separately purchased replacement hardware kits come unassembled.
Assembly instructions in drawing format are provided with the kit. To
assemble these kits, follow the procedures outlined in these drawings before
installing the sensor into the process piping or tank.
Low pressure hot tap assemblies can be purchased with many different inser-
tion rod lengths. Different lengths allow for flexibility in positioning the sen-
sor to the desired depth of the final installed location.
One difficulty often encountered is the lack of repeatability in positioning of
the sensor relative to the flow and insertion depth per the installation guide-
lines described in Section
permanent mark on the insertion rod that indicates the required insertion
depth and sensor position. These marks allow the sensor to be returned to the
desired location and orientation in a repeatable manner. Many methods can
be employed to determine where these marks should be located. The follow-
ing example describes one of them.
2. A way to overcome this is to place a scribe or