Vacuum transfer systems provide an alternative to augers. The initial applications were on jackups, primarily in the Gulf of Mexico, where the cramped areas required multiple conveyors to get around the legs and other obstacles. It was also easy to close the discharge chute, making a sump to collect the cuttings that is suitable for the vacuum nozzle.
A major advantage of vacuum transfer systems is that they permit more flexibility in siting components on the rig. The individual components (collection troughs, conveyors, collection boxes, etc.) are connected via hoses. This facilitates the routing of flow through and around congested areas on the rig and makes it possible to place equipment at different elevations when this is advantageous. The use of these systems has grown in recent years as the demand for total containment of wastes (zero discharge) has increased.
Vacuum transfer systems come in various types. Typical components include one or more vacuum blowers, a filtration device to protect the blower, vacuum hoses, and cuttings boxes with vacuum hose ports or vacuum lids that seal on the box lip. The vacuum pump may be skid mounted and can be either electric or diesel powered. Noise reduction devices and sound insulation should be used to reduce noise levels to below 80 dB, if possible. Many of the units commonly in use exceed noise levels set by the Occupational Safety and Health Administration and require hearing protection to work around them.
A vacuum pump is connected via hoses and/or pipes to a filtration unit, which in turn is connected to a collection box (or hopper, although these are rarely used). A hose or pipe connects to either a single point or to a manifold with multiple suction points at the waste source. The vacuum must be continuous to permit transport of the cuttings. The cuttings box allows the cuttings to fill in from one of the openings while the vacuum is pulled through the other side. While cuttings and waste are traveling through the hoses, sufficient velocity must be maintained to prevent them from settling in the line. Once the waste reaches the cuttings box, the material velocity slows, allowing the transported material to drop out into the collection chamber. Once the box is full, the hoses are switched, or the valve positions on the manifold are changed, to fill other boxes. As boxes are filled, they are lifted away and replaced with empty boxes.
