I guess I am in a privileged position to speak to many engineers and users of steam boilers in the course of conducting business. I get exposed to their challenges and have the opportunity to experience how they go about operating and managing their steam plant. Quite often the conversation turns to boiler control and automation, specifically the desirable base line features of a “good” automated boiler control system. Some engineers have to decide on acquiring a new technology control system, others realise that their current control system is not up to standard and are investigating an upgrade. Whatever the reason, the cost of the new or upgraded control system must typically fall within an already stretched budget and must offer a justifiable return on investment, if not in monetary terms, then at least in line with company objectives or policies.
My advice to anyone who has to acquire new or upgraded control technology is to at least make sure that the following features and functionalities are properly covered:
- The control system must be able to operate the boiler at highest efficiency within the constraints of fuel properties and the configuration of the boiler as designed and installed. There are still boilers out there which are manually operated, and we know that with modern control technology substantial efficiency improvements can be achieved with typically between 8% and 15% fuel savings. Unfortunately energy losses per se do not reflect as an entry on the balance sheet, but the cost of capital expenditure does, and often it is a matter of what cannot be seen, cannot cause harm. And so energy wasting practices continue unchecked.
- Manual and auto control of the boiler should be positively separated, which means manual operation should run independent of auto operation. The loss of a plc or HMI must not render the boiler inoperative; selecting manual operation must allow the operator to carry on producing steam, using the analogue instruments at his disposal to maintain steam pressure, furnace pressure and the water level.
- If the user is serious about remote boiler monitoring and information management a plc is a must. It has computational and data processing abilities. Modern plc’s come with on-board web servers and boiler monitoring and processed data can be accessed on any internet enabled device, such as a smart phone, tablet or computer. Ensure that quality information is captured, such as efficiencies, boiler outputs, consumptions, alarm conditions, safety and functional tests, diagnostics, etc.
- Eliminate human intervention in boiler operation as far as possible, but also make it as easy as possible for the operator to use and adjust the control system. Even with the highest level of automation operators are still needed to observe and adjust the combustion process, and this necessitates higher levels of understanding and skill from operating staff to meet performance expectations. Combustion conditions must be interpreted intelligently and responses and adjustments must be logical and accurate.
- Protect engineering settings behind a password, and assign different passwords to different levels of authority in the organization.
- Consider how alarms are being raised and for what conditions sirens are being sounded. A siren that sounds for every minor problem becomes a pain in the butt and quite often the operating staff will subtly sabotage or silence it. Rather make use of flashing lights or LED’s on the panel to draw the attention of the operator.
- Limit the steam output of the boiler to its maximum continuous rating. It helps in preserving a very valuable and costly asset.
- On a practical level: install the panel out of the way of movement of persons and other traffic, but make it easily accessible to the operator. Also consider exposure to high temperatures (radiant heat), water (steam) and dust.
- Please note that I have deliberately avoided the thorny issue of automation technology platforms, their cost, support, etc. in our discussion above. Most companies adhere to specific policies in this respect.
This post was compiled by René le Roux for Le Roux Combustion, all rights reserved. Do you want to know more about boiler control systems, or boiler optimization? Please contact us for your professional boiler automation, steam system efficiency and coal characterization needs.
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