Question

Give AT LEAST 5 METHODS of priming pumps.. Show their illustrations and describe how each methods are used in priming pumps.

Answer 1

Following are the five methods of priming -

1.Eductor priming, 2. Drop-The-Suction-Pipe priming, 3. Natural Priming, 4. Jet Assist Priming, 5. Ladder pump Priming.

1. Eductor priming

In this priming method, Sealing the discharge line at some point near to the pump. The discharge line sealed by using a flap valve or a pinch-to-prime device, filling it with water or by immersing a portion of it near the point where it leaves the dredge hull. Connecting the suction port of an eductor to a port in the top of the pump shell or in the discharge pipe if the pump is a top discharge model. The main goal is to use the eductor to pull a vacuum on the pump shell and cause water to enter and completely fill the pump shell.

2. Drop-The-Suction-Pipe priming-

This method used on the friction winch with its free-fall features. The procedure is very simple - raise the suction until the inlet reaches higher than the top of the pump shell, and open a vent valve on top of the pump shell and pump the system with full of water. When water flowed out of the suction inlet and vent valve it is main time to pump. Close the vent valve and release the hoist brake. Start the pump at the split second the suction hits the water. Apply the hoist brake and catch the ladder before it bangs the bottom. If the timing is right, the pump primed and kept pumping. If the pump lost its prime, this process to be repeated because in a large volume air got into the system before pumping commenced.

3. Natural Priming

In this method of priming, if the eye of the impeller is at or below the surface of the water then the pump may prime without any problem. The pump discharge port is at the high point in the system and a vent valve in the high point to allow air to escape. This vent allows air to escape and make room for water.

4. Jet Assist Priming-

In this method of priming installing a suction jet assist. If the pump shell and suction pipe are completely full of water the pump will prime at any starting speed. Slow starts are best the priming. A slow startup speed is necessary if there is some air in the top of the shell. Slow rotation causes the pump to lower the pressure at the eye of the impeller and cause water to start flowing in from the suction pipe and proceed to full prime as all the air is gradually expelled from the pump shell.

5. Ladder pump Priming.

In this priming method, Most of the ladder pumps prime automatically. If air is trapped in a ladder pump. it may prevent pump priming until the pump is immersed to a considerable depth. The trapped bubble of air should be compressed sufficiently to allow water to rise high enough into the pump for priming.