Thermo Scientific APEX 100, User Manual

Page: 81 / 442

Thermo Scientific APEX User’s Guide
Page 81
Setting Reject Parameters
This section tells you how to set reject parameters for a typical pipeline application.
Reject Totals
Understanding Reject-Delay and Reject-Duration Timing
In a pipeline application, the detector’s search head surrounds a pipe where product is
flowing under pressure. When the search head detects metallic contaminants in the
product, the product continues along the pipe, and is diverted into a waste tank by a
valve that closes off the main pipe. The diverter valve stays closed for a set period of
time (usually about three seconds) to divert the contaminated product, then opens again
to allow uncontaminated product to again flow freely. Thus, for the reject process to
work properly, two critical time parameters must be set.
• Reject-Delay Time
In most pipeline applications, where the diverter valve is located close to the
search head, the reject-delay time is usually set to 0.00 seconds. Thus, when the
search head detects contaminants, the valve closes immediately.
However, in applications where the diverter valve is located some way from the
search head, a time delay is needed, because the product takes a finite time to
move from the search head to the diverter valve. Clearly, the reject-delay time
should be set to make sure that the valve closes before the contaminated product
actually reaches the valve. Reject-delay times, when needed, are set in seconds
and hundredths of a second.
• Reject-Duration Time
This is the time (in seconds and hundredths of a second) that the valve remains
closed to divert contaminated product into the waste tank. A typical time for a
normal pipeline application is three seconds.
Once you have set the reject-delay time and reject-duration time parameters, you must
test the reject process. Then, if needed, you may want to fine-tune the detector’s
response to vibration caused by the diverter valve opening and closing by enabling the
reject-suppression feature.