Most of the choices and considerations for level controls discussed with customers are based largely on the criteria outlined below,
Any sensing, control, indication or detection consists of two main area’s
Do I need to know how much? What do I have in storage or do I need it for ‘controlling’ a process?
or
Do I just need to know when? Stop or start : Low level, dry running or high-level, overspill detection
Once decided upon, these are the other main criteria and questions to consider:
How important is this information – and what are the consequences?
It can be from the not very important, nice to know indication to a ‘safety interlocked plant shut down’. A plant could run out of important raw materials or be unable to despatch enough finished products to customers affecting cash flow. Maybe it could prevent a major pollution incident (from an effluent tank) saving thousands in fines (and reputation) or a simple saving of energy or plant equipment. (e.g. switching a pump when its not required)
What information is required? And in what format? A visual indication, or an alarm, flashing light, klaxon, a table on a computer screen, an automatic shut down, e-mail, text message or pager, a Fieldbus protocol to a main DCS system.
Who needs it? Someone or everyone? This information can be shared through the whole organisation:
- Plant operators walking past the vessel,
- Drivers at an offloading point,
- Central plant control system
- Production planners for future order fulfilling
- Distribution and logistics to coordinate deliveries,
- Accounts for stock valuation,
- Purchasing departments for re-ordering,
- Management for strategic decision,
- Sales team for customers placing orders
- Material suppliers/vendors to share information and schedule deliveries.
Accuracy? What size of tank, vessel or hopper range am I measuring over? What are the consequences (see above) Do I need the nearest millimetre or metre? Am I looking for a trend or an absolute accuracy of measurement?
What are the process conditions? These also need to be reviewed of course; temperatures, pressures, materials compatibility, process and product compatibility and behaviour, any special standards – for hygiene or safety certifications. What and where are the connections into the process and equipment, what is the access to the plant, are there preferences for contact or non-contact measurements…and how will this all interact with some of the criteria above?
The ‘connectivity’ is the next step. What is available for access, power, wiring, mounting of devices and local indicators, protocols for connecting to plant and pc networks, scheduling of the plant to be available for installation. Liaising with electrical departments and contractors for installation, mechanical personnel if vessel modifications are required, production for availability, perhaps IT people if the information is to be networked - as well as a commissioning engineer or can internal staff complete this?
After sales service, maintenance and support for the equipment. This is the final step but probably one of the most important and should be considered just as carefully BEFORE purchase; What is the warranty, what about obsolescence/compatibility, how easy is it to use, Is in house ‘competency training’ required, service contracts, remote connection/calibration and on going support for any issues or maintenance?
Experience
Above are only some basic points to consider as a guide, difficult for busy staff to get their heads around with all other work needs, but all of this and more is considered by a Specialist Level Engineer, who will discuss these options and more with customers every day. They can take people through all the options, steps and budget consequences, ensuring that all aspects are considered for the best outcomes to be secured. We are always happy to answer any questions customers have, so feel free to contact us if you have any question arising from this blog.
Next time we will cover some of the techniques of level measurement and the basic considerations.
This entry was posted
on Friday, February 8th, 2008 at 3:11 pm and is filed under Aggregates & Mining, Automotive, Beverage, Bulk Solids Handling, Cement, Chemical, Dairy, Distillation of Alcohols, Environment & Recycling, Flour and Milling, Food, Information, Level Measurement, Marine Shipping Harbours, Offshore Oil & Gas, Other, Paper and Board, Petrochemical, Pharmaceuticals, Power Generation, Steels and Metal Manufacturing, Water and Waste.
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