Recommended Slurry Pump Flushing Procedure
Dec 01, 2020
All slurry pumps must be flushed immediately after shutdown. Failure to do so can allow slurry to settle in the casing, build up in the suction or discharge piping and attach to the slurry pump liners, impeller and / or seal components. Mechanically sealed slurry pumps are especially susceptible to failure from solids build-up. Subsequent starts of the equipment can then tear liners, damage impellers, fail mechanical seals and damage piping components and their support structure.

If the solids in the casing cause the impeller to start in a bogged condition, excessive shaft deflection can occur, and may result in mechanical seal, bearing, and foundation failures. Piping and piping support structure and drive train damage can occur as well.

The exact procedure required in each installation will vary. The entire flushing process may take as little as 15 minutes for a small slurry pump, but may take hours for a large slurry pump. The desired end result is to have the slurry pump completely filled with clear liquid and to not have damaged the slurry pump or pumping system in any way during the flushing sequence. The suction valve should be closed. It is assumed there is a drain valve located in the suction line between the slurry pump and the suction valve.

Slurry Pump should not be rotating and the liquid in the slurry pump should be stationary, not flowing in or out of the slurry pump, prior to starting the flush procedure. The best position for the discharge valve during flushing is dependant on site conditions.

If there is a closed discharge valve in the system the vent valve between the slurry pump and the discharge valve must be open. If there is no vent valve the discharge valve must be open.

If the discharge valve is closed and there is no vent valve, (or if the vent valve is closed) it is possible to create a vacuum or over pressurize the slurry pump during the flush and drain sequence that could damage or displace the liners in the slurry pump or damage other slurry pump and piping components. 

Flushing
1. With the discharge vent or discharge valve open, open the drain valve on the suction line and drain the pump until slurry stops issuing from the drain valve. This leaves the bottom of the slurry pump casing below the suction line full of slurry.
2. With the discharge vent or discharge valve open, close the drain valve and open the flush line to fill the slurry pump completely. Minimum liquid level should be at least past the slurry pump discharge flange.
3. With the discharge vent or discharge valve open, open the drain valve and drain the slurry pump until liquid stops flowing.
4. Repeat this process until clear liquid comes out of the drain valve. Storage/not operating
5. Slurry Pumps not operating for any period of time and potentially exposed to process gasses should be filled completely with water to prevent gases from attacking metal components in the slurry pump.
6. If the possibility exists the suction valve will leak and allow solids into the slurry pump during idle periods, filling the slurry pump discharge with clear water up to the height of slurry in the suction tank will help minimize solids leaking into the slurry pump.
7. Regular checks should be made to ensure the liquid in the slurry pump does not drain off. The discharge vent should be left open to prevent vacuum creation should liquid leak from the slurry pump during the storage/not operating period.
8. It may be necessary to change the liquid in the slurry pump during storage periods to prevent a buildup of acids or solids in the slurry pump.

Frequency required will be site condition dependant. Cycle times for draining and filling the slurry pump and pipe will vary depending on slurry pump size and the piping system. Based on site conditions this flushing procedure should be modified as necessary to achieve the end goal of a clean undamaged slurry pump and piping system full of clear water.