Elster Instromet 2000 - Grab Sampler Calculations

Model 2000 Flow Computer Instruction Manual
2.0 GENERAL DESCRIPTION
Model 2000 issue 21 Page No
55
The operator can only modify the cylinder size, grab size and output pulse duration samples if no sampling is in progress and
the volume in the cylinder has been reset. The operator can modify the expected production and sample pulse duration to
allow for changes in flow during the production period.
Sample Cylinder Reset
Whenever a sample cylinder is physically emptied, the operator should reset the displayed volume to zero. The operator can
only reset the cylinder volume if no sampling is in progress. When the cylinder volume is reset the grab count is also reset to
zero.
Sample Cylinder Full Detection
The Flow computer monitors the fill level of each sampler with an analogue level indicator (4-20 mA) See paragraph 2.4.13
or with a digital switch input see paragraph 2.4.13. When flow rates have changed during the specified period and the total
exceeds the operator entered expected total, the sampling will be stopped as soon as the cylinder level exceeds the Cylinder
full alarm (default 95%). An alarm will be raised when the cylinder level exceeds the Cylinder Alarm level (default 80%).
2.8.6.2. GRAB SAMPLER CALCULATIONS
The sampling is flow proportional, but will be ended at the end of the specified period. To organize this flow proportional
sampling, the expected liquid total for that period, the cylinder and grab size must be entered by an operator. The following
equations will then calculate when a sample needs to be taken.
Size Grab
0.01Limit FillSizeCylinder
Samples ofNumber
×
×
=
(1)
Samples TakenSamples ofNumber Samples Remaining
−
=
(2)
Samples ofNumber
Total Liquid Expected
Samples between flow Mass
=
(3)
100
SizeCylinder
Size GrabSamples Taken
Volume Estimated ×
×
=
(4)
Volume ActualLimit FillVolume Remaining
−
=
(5)
Total Liquid Expected
Size Grab
Rate Sample =
(6)
Where:
Number of Samples : Number of samples to fill the sample cylinder to 80% Equation 1
Cylinder Size : Size of cylinder in ml or cc Data Entry
Grab Size : Size of the sample plunger in ml or cc Data Entry
Fill Limit : Limit of cylinder used for filling Data Entry
Remaining Samples : Number of grabs to fill the sample cylinder Equation 2
Taken Samples : Counter of the samples taken by the FC Measured
Mass flow between Samples : Mass flow counted between two samples Equation 3
Expected Liquid Total : Expected period total Data Entry
Estimated Volume : Current calculated volume in the sample cylinder Equation 4
Remaining Volume : Remaining volume required to fill the sample cylinder Equation 5
Actual Volume : Current volume in the sample cylinder Measured
Sample Rate : Number of grabs taken per mass unit Equation 6