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IP258
11
4 INSTALLATION
4.1 PRELIMINARY CHECKS
The MSM400 system is normally supplied in two packages, one for the MSM400 Control Unit and one for the
sensor, whether it is a pipe section or a tank sensor. Take care in handling the pipe section. In particular do not
damage the cable or the hose protection for the cable where it enters the sensors. Before installation check that
there has been no damage in transit, particularly to the sensor cables. Check that the equipment is as specified, and
that the pipe section length and flanges are compatible with plant pipework.
Sensors in intrinsically safe systems may be mounted in potentially explosive areas ("hazardous areas"). Refer to the
sensor safety data section 2.4.
The control unit must be mounted in a non-hazardous ("safe") area. Refer to control unit safety data section 3.3.
4.2 PIPE SECTION INSTALLATION
The Mobrey MSM448 pipe section sensor should be same size as surrounding pipe work. It should be installed in a
straight section of line, if possible, with the sensors in a horizontal plane. This avoids the sensors being covered with
debris at the bottom of the pipe, and being in an air gap at the top of the pipe. Particular attention must be paid to
the positioning of the pipe section in relation to pressure reduction or agitation of the slurry to be monitored :
Figure 7 : Pipe sensor orientation
WARNING:
Air or gas that comes out of suspension in a slurry gives a high ultrasonic attenuation, giving a false high solids
reading. The installation must maintain the full hydrostatic pressure in the slurry up to the pipe measurement
section. Any unnecessary pressure reduction should be avoided. This means avoid free fall of the slurry into a sump,
avoid pumps and partly open valves, avoid abrupt changes of pipeline diameter upstream of the sensor pipe section
installation point. If possible position the sensors directly at the outlet of the tank, low down, so that the full
hydrostatic head is maintained on the monitored liquid. However, it may be necessary to remove the sensors for face
cleaning later, so isolation valves are desirable. The Mobrey Sensor pipe is supplied with a flushing spray nozzle,
which directs a supply of water at the sensor faces. This is a useful cleaning procedure, avoiding the need to remove
the sensors from the pipe. A water supply is required, connected to the purge nozzle on the top of the sensor pipe
section.
4.3 SUSPENDED SENSOR INSTALLATION
The Mobrey MSM433 sensor is available with the gap between sensor faces from 100 mm up to 450 mm, for higher
sensitivity to light slurries. These sensors are usually mounted directly into the settlement tank, at pre-selected levels
above the tank discharge outlet. Mounting can be vertically down on a piece of conduit, or suspended on the sensor
cable. Whilst the conduit might be attached to the tank wall, it is normal to have the sensor well away from the wall
itself, to avoid any non moving slurry or "dead" settlement areas. It should be possible to lift the sensor out for
periodic cleaning and/or rag removal.
Pipe line
Pipe line
Sensors horizontal in pipe OK
Sensors vertical in pipe NOT OK
Sludge settles on bottom sensor
Top sensor probably in air