Dirt pans

Hot-dip galvanised steel components are used in sewer technology as drain gratings, covers and as dirt pans for balconies, roofs, and cellars in road and estate drainage. It is also used as buckets for drains in roads [40]. A zinc layer of at least 400 g/m is required for these components [41]. 

Metal Pan Assemblies. These units consist of tiles and panels formed from perforated aluminum or steel with pads of fiber glass or mineral wool inserted into the pans to provide the sound absorption. They are used primarily for ceilings in a similar manner to acoustical tiles and panels. The pads are sometimes sealed in plastic film to prevent absorption of moisture, dirt, and odors. The perforated metal is relatively sound transparent and functions as the finished ceiling and the support for the sound-absorbing material. The perforated metal by itself has no acoustical value. 

Protect sample containers and field meters from contamination with dirt and dust by placing them into large shallow plastic pans or keep them covered in coolers or boxes. 

The need for positively sealing the downcomer is determined in this phase. This could be achieved by installing an inlet weir, which is a weir installed at the tray inlet to keep the downcomer outlet immersed in liquid. A similar device, which extends below the tray floor, is a seal pan (Fig. 17). Both devices provide positive assurance against vapor rising up the downcomer, but they may also trap solids and dirt and cause blockage. A seal pan must always be used in the downcomer from the bottom tray otherwise there is nothing to prevent vapor from rising up the bottom downcomer. 

The regeneration time is determined by the time in which silt passes from the beginning of the regeneration corridor to the beginning of the oxidation corridor. Purified waste waters self-flow out of settling boxes 22 through pans into dirt settling box 25. Dirt is removed from there as it accumulates. 

Inlet weirs and recessed seal pans have the disadvantage of creating areas of stagnant liquid, where sediment, dirt, and polymer can build up. Such buildup may restrict the downcomer outlet flow area and cause premature flooding. For this reason, these devices should be avoided in fouling services (88, 144, 257, 268, 404, 409). Inlet weirs and recessed seal pans are also more expensive than flat seal areas, but often by a small amount (61). The cost difference between inlet weirs and recessed seal pans is usually small (73, 317). 

Sources of lAQ contaminants related to the HVAC system can include dirt and dust which is found in ductwork or on other components, but is most often seen as microbiological growth found in drip pans, humidifiers, ductwork coils, and other moist portions of the system units. In addition, lAQ investigators commonly look for improper venting of combustion products such as carbon monoxide from water heaters, steam boilers, and gas appliances. 

Below the downcomer of the bottom tray is the seal pan. The seal pan, like a recessed sump, is also a potential dirt trap. I ve crawled... 

A drain hole is provided in the floor of the seal pan, and is sized for 20-25 percent of the design flow, to flush out the accumulated dirt. 

If a drain hole plugs on a bottom tray seal pan, I have found that the seal pan will, with time, fill with dirt and corrosion products. This restricts the flow from the downcomer and has caused at least one amine fuel gas hydrogen sulfide absorber to flood. To avoid this problem. I ll size the drain holes in such seal pans to pass 20 percent of the liquid flow, or at least use a single 1-inch drain hole. Unless liquid is flushed out of the bottom of the bottom tray seal pan, the solids washed down the column settle out in the seal pan. 

When finished, use a dustpan and brush to collect the piles. When you see a line of dirt left, turn the dustpan to the opposite angle and sweep it in the pan. If the lines aren t vanishing, wipe them up with a damp paper towel. 

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