ABB KM26 Operating Instruction page 18

18
KM26 | M AGN ETI C L EV EL G AU GE | O I/KM 26 -E N REV I
. . . 3 Mounting
Isolation valves
Valves should be installed between the tank and the KM26 for
maintenance purposes and are available as an option.
CAUTION
Care must be used when opening the valves to prevent a
surge of fluid or gases through the chamber. A surge can
cause the float to be propelled against the far stop
causing damage to the float shell and / or the indicator
glass. Failure to comply may result in damage to the float
and expense to the customer. Gradually open the upper
isolation valve prior to the lower one to equalize the
pressure in the level gauge chamber with the pressure in
the vessel. After the pressure has equalized, gradually
open the lower isolation valve. At this point, the level
indicator may show a liquid level if enough liquid is
present.
Vent and Drain
The vent and drain connections provide the user an alternate
way to pipe into the chamber. In many cases, the drain is left
either plugged or closed off with a valve. It can be opened at
any time to drain the remaining liquid out of a recently
emptied chamber. These accessories are offered with the
KM26 as options.
Pressure testing
CAUTION
The level indicator chamber should be blocked off or the
float should be removed when the vessel is hydrostatically
tested. This precaution is necessary because most vessels
are tested at pressures much higher than the maximum
operating pressures and, even though the float chamber is
capable of the high pressures, the float may not be
capable of handling such pressures. All units are clearly
marked as to this danger and should be given special
consideration. Failure to comply may result in damage to
the float and expense to the customer.
Magtraps
Magnetic particle traps (or magtraps) are provided to prevent
ferromagnetic particles in a tank from entering the KM26
chamber and interfering with the movement of the float. The
trap is installed at the bottom process connection. The
permanent magnet in the trap ensures the clean and effective
removal of ferrous contaminating materials.
Insulation
Chamber, switch, transmitter, and flange insulations are
available as an option or, to meet the temperature
requirements specified. These coverings protect the process,
personnel, and / or equipment from temperature extremes.
The customer may elect to install their own insulation. When
this is done, care must be exercised to insure that associated
equipment (such as scales, switches, transmitter, and other
items) remains in proximity to the float magnets and that the
insulation does not adversely affect the devices in terms of
temperature retention.
Figure 21 - KM26 with insulation
Scale zero
Scale zero (lowest measure point on the ruler) for the KM26S
is typically at the centerline of the lower side process
connection or 10 in. from the face of the bottom flange. This
varies with specific gravity requirements or custom designs.
The KM26T zero point is typically 6 in. to 10 in. from the face
of the process connection unless some special requirement
calls for a change. In any case, the scale zero point coincides
with the float at the lowest point in the chamber. The scale is
installed so that the indicator just begins to move when the
float is against the bottom stop.
Replacing indicator tube
1 Remove the machine screw in the upper tube holder.
Remove the upper tube holder by sliding it out of the end
of the channel (do not pull forward). For units 60 in. or
longer remove all of the stainless steel wires that retain
the tube in the channel. Slide the tube to be replaced out
of the end of the channel.
2 Before installing replacement tube, check for proper
orientation. The bottom of the shuttle tube will have an
orange 'PAC-MAN' shaped silicon bumper inside the tube.
The bottom of the magnetic bar graph glass tube will have
an indentation to align with the bottom tube holder.
Insert the replacement tube into the bottom holder. Install
the top holder using the machine screw to hold in place.
Replace any stainless steel wires necessary to retain the
tube in the channel.
3 Cryogenic indicator tubes are sealed into the scale
assembly and should be replaced as a unit. These scale
assemblies are strapped in place using gear clamps.