DE-Lecture09-Basic-Pump-Hydraulics

DE-Lecture09-Basic-Pump-Hydraulics - Dredging Dredging...

Info icon This preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Dredging Engineering Lecture 09 Basic Pump Hydraulics Luis Prieto-Portar 2010
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
The Parts of a Dredge Pump. In Lecture 08, slide 13, we saw that the basic dredging centrifugal pump is a (1) volute, single stage, single suction, with a closed, single-curvature, non-clogging, overhung, radial curved-vane runner, and a horizontal, split or solid casing. (1) The term volute means spiral , and is named after the shape of the casing which is a equiangular spiral where its radius r is given by r = ae θ tan α . This shape was derived by the brilliant French mathematician, Blaise Pascal (1623-1662). The curve possesses the property that the acute angle α between the radius and the tangent to the spiral is a constant. The ensuing equiangular shape produces an equal velocity of the flow around the circumference. At the same time the velocity is converted into pressure, and is gradually reduced as it flows to the discharge end of the pump.
Image of page 2
(2) The closed-vane runner has shrouds (sides) that totally enclose the vanes. This set up creates closed channels from the “eye” of the pump (the entrance from the suction side) to the periphery of the runner. (3) A straight or single-curvature runner has its vanes curved backwards, opposite to the direction of rotation. On the other hand, double-curvature runners have their vanes curved in two directions, such as the blades of a ship propeller. (4) Non-clogging runner s have fewer vanes so that there are larger areas for larger solids to get through. The largest number is usually five vanes, which is useful for very fine and soft soils (silts and fine sands). (5) An overhung runner has the drive shaft supported on only one side.
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Pump liners are used to protect the pump casing (shell), pipeline, fittings, runners and cutters from wearing out due to abrasion. These liners and replaceable rings are placed inside the pump casing. They also serve the important function of sealing the high pressure discharge volume from the low pressure suction volume. Pump casings are made from 12% manganese steel alloy because it provides high shock resistance, is non-magnetic, very ductile and is easily welded. Another common alloy is Ni-Hard (International Nickel Company), also provided as ABK Metal (by American Brake Shoe Company), Flintmetal (by Morris Machine Works) and Gasite (by Georgia Iron Works). Stuffing box provides a seal around the runner shaft where it enters the pump casing. Runner thrust is the axial thrust of a single-suction runner, due to the two opposing forces: (1) the change in the momentum of the mixture entering the runner, which tends to force the runner backward, and (2) the opposing force caused by the discharge from the runner. The pump’s discharge is at a much higher pressure than at the suction, thus moving the runner forward.
Image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern