The Submerged Flight Conveyor (SFC) is a proven bottom ash handling system and the most cost-effective compared with other alternatives. Designed for use with most boiler types, this type of bottom ash handling system has become the most common bottom ash handling system since the mid-1990s. This system is often used to replace legacy sluice systems and is well suited to new installations where water and headroom are limited.
However, not all submerged scraper conveyor designs are created equal. Every aspect of the SFC from United Conveyor Corporation is designed to minimize maintenance and to operate dependably from outage to outage (see Performance tab). With over 100 installations worldwide, the UCC SFC system has proven to be the industry leader for performance and reliability.
Operation of the Submerged Flight Conveyor (SFC) is very simple. Ash falls from the boiler into a water-filled, upper trough that quenches and cools the ash. Chains and flights move the ash along the horizontal trough and up a dewatering ramp. At the top of the ramp, the ash falls through a discharge chute into a concrete bunker, where it can be loaded into trucks for final disposal. The flights continue through the lower (dry) chamber to the rear of the conveyor and then return to the upper trough.
SFC Submerged Flight Conveyor:
- Continuous ash removal up to 100 TPH
- Less energy and water consumption than sluice systems
- Premium construction for highly reliable 24/7 performance
- Upper trough (wet) is lined with thick AR400 abrasion-resistant steel plate for maximum strength and durability
- Bottom trough (dry) is lined with thick abrasion-resistant rails or basalt tile for maximum strength and durability
- High-strength, robust round chain link is case hardened to UCC specification (approx. 700 BHN) for longer-life durability.
- Drive sprocket teeth are made from Durite® H alloy and case hardened for maximum strength and durability
- Flights are constructed of rectangular steel tubing, instead of angle iron, to greatly resist and avoid derailment or bending.
- Submerged idlers are cast from corrosion resistant, Durite H material (650 BHN) and heat treated for superior life and reliability
- Structural support designed to withstand upset conditions.
- The chain tensioner uses a hydraulic cylinder to maintain constant chain tension which extends the chain life and eliminates weekly adjustments common.
- An integral indicator provides visual reference of chain wear. A linear positioner provides an instant alarm if the chain breaks.
- Simple, direct drive soft-start hydraulic motor/reducer provides superior performance and less maintenance over variable speed drive motors.
- The SFC is designed for either variable speed operation, or for two pre-set speeds: normal mode and “catch-up” mode. The higher speeds are used when the unit has been shut down temporarily and a large volume of ash has been collected in the upper trough.
- Modular design simplifies field erection and reduces installation cost
- Optional rollout wheels allow direct access to the boiler throat during a shutdown
When is an SFC the most appropriate?[+]
The SFC is the most appropriate solution when seeking a system that provides the continuous removal of ash and when reducing water consumption is a major deciding factor. It is also appropriate where headroom is limited and the disposal point is near the boiler.
My drag chain can pull large clinkers out from underneath the boiler and I don’t want them to fall into the truck/bottom ash bin/ belt conveyor located at the discharge. Is there anything that can be installed that would prevent this?[+]
A clinker detector can be located on the ramp to stop the SFC and allow the clinkers to be removed manually before being discharged onto/into that equipment.
When should I remove links from the chain?[+]
Remove links when (2) links (horizontal and vertical) can be removed from the chain and there is still a few inches of room for tensioning.
What boiler types are compatible with the SFC?[+]
The SFC has been used on pulverized coal (PC) boilers, cyclone boilers, wet bottom (slagging) boilers, stoker-fed and traveling gate boilers, and incinerators. There are three standard widths (1000mm, 1500mm, and 2000mm) to accommodate these boiler types and sizes.
How does the SFC interface with the boiler?[+]
Depending upon the boiler design and placement of the boiler seal plates, the SFC may be interfaced with the boiler one of two ways: Seal Plate or Transition Hopper.
How important is the chain to system performance?[+]
During normal operation, the case hardened chain will elongate over time (from wear) based on its load and abrasive environment. To avoid the risk of derailment, drive sprocket adjustments are required to compensate for this elongation.
How can I tell if my submerged idlers are rolling? [+]
UCC offers submerged idlers with integral speed switches to continually monitor idler rotation.
Does the SFC offer any features that make it easier for work to be performed underneath the boiler?[+]
Yes. The SFC has an optional manual or motorized roll-out feature. This allows the entire SFC unit to be moved from underneath the boiler providing direct access to the boiler throat during shutdown.
– 27”, 33”, 54”
Mechanical System Components
– SFC Idlers, chains, flights, HPU, tensioners