When working with high temperatures using natural gas, if an industrial furnace does not have its safety regulatory instruments properly adjusted it is almost as if we had a time bomb waiting to explode in our plant.
Safety interlocks are instruments especially responsible for monitoring these high temperatures and verifying that the equipment is within safe values, so that if a furnace exceeds the established limits, the interlocks will be responsible for cutting off the gas supply to avoid explosions.
However, these devices need to be checked at least once a year to function properly. Find out more in this article.
A vital aspect for safety in your plant
Safety reviews specifically focus on combustion system safety equipment and instruments in order to:
• Make sure they are in good condition and are working properly.
• Verify that they are configured with the correct values so that in the case of unforeseen events they act efficiently to avoid explosions.
The NFPA86 Standard, Chapter 7, Section 7.4 establishes the guideline for these checks, designating the user of the furnace as responsible for their realization and documentation.
For its part, the manufacturer is responsible for laying out in the furnace operating manual, in the ‘Maintenance and Inspections’ section, all the instructions necessary to perform the checks, especially in the case of annual reviews.
Review of security interlocks – key aspects
The vital points to analyze in the annual checks are as follows:
• High temperature limits: both the operation and the setting of the correct temperature values.
• Flame relays: check the correct ignition sequence of the burner to ensure that if there is no flame at the burner, the burner will be immediately cut off.
• Temperature bypass: both the operation and the setting of the correct temperature values.
• Gas relief valves: verify their operation to confirm they open with the predetermined gas pressure.
• High and low air and gas pressure switches: their operation and setting of the correct pressure values.
• Gas safety solenoid valves: that they open and close correctly, and that there is no gas leak when they are closed.
• Valve proving system (vps): that this instrument responsible for verifying the tightness of the safety solenoid valves in the gas train performs the appropriate sequence.
• Explosion relief ports: that there are no obstructions so that they can be opened correctly; make opening tests and confirm that they are not padlocked.
• Manual gas shut-off valves: open and close them to verify that they are not stuck, in order to ensure that they work properly in the event you need to cut off the gas; if necessary, check the correct level of lubrication.
Recommendations during safety checks
Some best practice procedures that we advise you to consider during your inspections are:
• The set points of all interlocks must be documented in the furnace manual and each report during the annual reviews with the values analyzed and adjusted.
• The set point of temperature, pressure or flow devices used as safety interlocks must be verified (at least annually).
• Check the correct operation of the high temperature interlock (high temperature limit) set point.
• Verify at least once a year that the security interlocks are present and have not been bypassed or do not work.
• The maintenance department should schedule these safety checks as part of its maintenance routine.
At Nutec Bickley we are experts in industrial safety and all our furnaces comply with all regulations.
Contact our consultants to review your needs and to develop your next project.
