A waste and recycling company’s process includes bulk storage, discharge and transfer of a variety of residues, which are the byproduct of incinerating chemical, clinical and municipal wastes. These are solids and residues from flue gas treatment, APC, FTG and fly ash. The company had experienced problems with the existing valves located on the outlet of their bulk storage silos. Due to the aggressive and varying nature of the materials being handled, the existing valves had difficulties opening and closing through a standing column of material.
The Vortex®Titan Slide Gate™ (TSG) was identified as the ideal solution for this application. The TSG is designed for handling heavy-duty, abrasive dry materials in gravity flow applications. Beneficial features of the TSG include a positive material shut-off and dust-tight sealing capabilities.
Because this client’s process had high-pressure silo discharge aeration(despite the TSG’s “gravity flow only” design), to prevent leakage of materials and dusts to atmosphere, the TSG was equipped with a Return Pan.
A Return Pan is a fabricated metal piece designed to transition the outlet side of a gate. It is angled to create an inverted “ramp”– beginning narrow at the back of the gate and gradually steepening as it approaches the gate’s opening. When using a Return Pan, on the top part of the gate, a solid bonnet cover is used. On the bottom part of the gate, a perforated bonnet cover is used. A Return Pan is installed on the outlet side of the gate, directly beneath the perforated bonnet cover. As materials begin to migrate into the bonnet area, rather than building up, they are deposited down through the perforated bonnet cover and onto the Return Pan, to be reintroduced into the material flow stream.
Benefits of a Return Pan include:
- An inexpensive way to prevent dusting to atmosphere. This improves housekeeping and workplace safety, and prevents product loss.
- An effective solution to prevent material build-up in the bonnet area, which could otherwise cause gate actuation issues.
On the closing stroke, the TSG is designed so that the blade enters into a recessed area with a displacement pocket. Upon gate closure, the displacement pocket prevents materials from packing, as they would into an end seal. The displacement pocket also allows any materials remaining at the leading edge of the blade to fall away into the process line below, even after gate closure. This feature is essential when handling packable materials, as is the case in this client’s process. Otherwise, material packing can cause seal wear,actuation issues and material leakage past the gate.
For ease of maintenance, the TSG features milled access slots on each side of the gate’s frame so that bonnet seals can be quickly and easily replaced whilst the gate remains in-line.