Sampler control systems
What type of control system is recommended by the standards?
The primary function of the control system is to operate the sampling device in a time or flow proportional manner. (more information) This normally requires that the controller have a real-time operating system. The system should allow the operator to enter the batch size and should determine the necessary sampling rate to achieve the correct volume of sample.
The system should monitor the number of grabs and the volume of sample collected to verify at any time during the batch that the sampler is working correctly (normally using a weighing system). At the end of a batch the system should produce a report validating system performance and performance factors during the batch.
Facilities should be provide for monitoring the following:
- Main pipeline flow rate.
- That the sample volume collected is proportional to the totalised flow in the main pipeline (i.e. performance factor).
- The number of grabs.
The system should provide alarms in the event of failure allowing a back-up manual sample to be taken. Alarms should be provided for the following:
- High level in sample receiver.
- Low flow in main pipeline.
- Low flow in sample loop (in bypass loop systems).
- Loss of power.
- Sample probe failure.
The controller may include facilities for batch identification and producing reports at the end of batches and can have a DCS interface. If the system is located at a facility with a large line-fill the control system should allow a separate line-fill sample to be taken at a high sample rate into a different sample receiver. More about line-fill.