Rope skimmer

Rope skimmers Irrelevant 0-15 Yes No Surface water use only... 

Skimmers may equipped in different ways such as free floating, built into a vessel, side mounted on a vessel, or held by crane. Several types of skimmer may be used for oil removal. The rope skimmer is one type that employs polypropylene, PVC, or aluminum as adhesion materials, as shown in Fig. 3. The floating oil can be attached to these moving surfaces and removed out of the water. The belt skimmer (Fig. 4) is used to convey floating oil by moving through the oily waste from water. In a filter skimmer, the water can pass through the belt while the oil is filtrated and adhered on the belt. At the top of the belt the oil is scarped off into a sump or a pump. 

Fig. 3. Rope skimmer using polypropylene as an adhensive material.

Photo 59 A rope skimmer can be used to recover oil from under ice. (Al Allen)... 

Rope skimmers remove oil from the water surface with an oleophilic rope of polymer, usually polypropylene. Some skimmers have one or two long ropes that are held in the slick by a floating, anchored pulley. Others use a series of small ropes that hang down to the water surface from a suspended skimmer body. The rope... 

Photo 63 A rope skimmer is shown recovering a weathered crude oil. (Environment Canada)... 

Oleophilic surface skimmers use a surface, to which oil can adhere, and thus be removed from water surface. A wiper blade or a pressure roller then removes the oil from skimmer surface and deposits it into an onboard container. The output mixture of the skimmer may also be directly pumped into storage and separation facilities on a barge. Various types of oleophilic surface skimmers are available based on the process of oil adsorption, including disk drum brush belt and rope skimmers. 

Winds and waves, in general decrease the effectiveness of skimmers (Fingas 2011, Schulze 1998, Ventikos et al. 2004). This is mainly due to the splash of oil over skimmers, and also because rough waters move the skimmer collection mechanism away from the oil layer on the water surface. However, there are some types of skimmer, such as rope skimmers, whose performance is less affected by waves (Fingas 2011, ITOPF 2012, Potter et al. 2012, Schulze 1998). 

Rope and belt skimmer units are quite efficient at removing thin layers of LNAPL from both open-trench wells and larger surface areas (ponds, or even manholes). Recent developments include development of belts that are sufficiently narrow to use in open wells. Both smooth flexible-tube and belt systems rely upon continuous rotation of a flexible closed-loop tube (or belt) constructed of an oleophilic material (Figure 7.16). The automatic unit draws the oil-covered tube (or belt) through scrapers and returns it to the surface to gather more oil. 

FIGURE 7.16 Schematic of a rope (a) and belt (b) skimmer system. 

The advantage of either rope or belt skimmers is that they do not require significant operational attention. They can be left unattended (except for routine maintenance) for extended periods of time. Also, either unit can recover thin layers of floating product without sophisticated instrumentation. The primary disadvantage is that the recovery capacity is limited to a few hundred gallons per day per unit. Higher-viscosity oils attach more effectively to the oleophilic materials. Less-viscous products are recovered less effectively. 

Skimming of oil and grease from the surface of separation vessels can be performed on a manual or continuous basis. The viscosity of many oils used in vegetable oil processing at ambient temperature is such that surface contact-skimming devices (belts, ropes) are not particularly effective. Chain and scrapper type skimmers are effective, but not physically adaptable to every skimming sima-tion. Shop fabricated, manually operated decant devices have been effective. 

Oleophilic surface skimmers — Also called sorbent surface skimmers, these skimmers use a surface to which oil can adhere to remove oil from the water surface. This surface can be in the form of a disc, drum, belt, brush, or rope that is moved through the oil on the top of the water. The oil is removed with a wiper blade or... 

Sorbent-surface skimmer — This is a mechanical skimmer that incorporates a rotating, sorbent surface (oleophilic) drum, disc, belt, or rope to which oil adheres as the surface is moved continuously through the slick. 

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