Maintenance

September 2007

Stop Water from Drying Up Your Operation

This must-know advice and top 10 indicators of pump malfunction will help enhance the longevity of your pumping equipment.

by Stephanie Morgan

In crushed stone and sand and gravel operations, water sometimes can be your worst enemy.

With high heads (Total dynamic head is resistance in pumping, and the resistance is a result of the forces of gravity and friction loss against the water as it moves.) weighing heavily on pump shafts in deep pits, sand- and silt-laden groundwater eating away at wear parts, and large solids threatening to ruin impellers, there are numerous issues that could bring pumping to a halt. When pumping stops, so does production. Whatever type of centrifugal pump you use, the precautions and preventive maintenance plans for aggregate dewatering pumps are relatively similar.

Understanding the basics

The solids-laden water at the bottom of a pit can quickly eat away at a pump. Choosing a pump that has solids handling capability and hardened wearplate metallurgy will help combat wear patterns. While a regular maintenance schedule is the best insurance policy, these fundamental startup and handling procedures will also help prolong the life of a pump:

• Change the engine oil and filter after the first 100 hours.

• When preparing for cold weather, drain the discharge line and volute so that the suction line and volute drain enough to prevent damage to the volute, wearplates, and seals if any remaining water freezes and expands.

• To prevent establishing suction directly from the bottom of a pit, where the most damaging material is commonly found, use a floating screen/strainer on your suction that enables solids to pass that are no larger than the manufacturer’s published solids handling size.

• Do not move the pump with hoses attached.

• Be aware of the environment.

The most important aspect of pumping water is sizing the pump to match the task at hand (see “Pumping for Maximum Production,” Aggregates Manager, May 2007).

Knowing your surroundings

With the appropriate pump selected based on flow, lift, and distance, focus then turns to site requirements. Most water in mines and quarries is laden with abrasive materials that cause pump wear. While some deterioration is a byproduct of the materials being pumped, other wear is a result of poor site preparation. Regardless of the type of pump you’re using, the following site preparation tips can help minimize common maintenance problems for any type of pump:

• Select a site as close as possible to the source to be pumped that has a relatively straight path between the fluid source and the suction inlet of the pump.

• Locate the pump far enough from the high wall face to protect operators and prevent pump damage due to falling minerals.

• Be aware of and make provisions for the power source of the pump, whether it is engine or motor driven.

• Choose a site that is flat and on firm, compacted ground.

• Lay out piping runs before installation.

• Consider the pump’s total, loaded weight when selecting hoisting equipment used for final installation.

• Use a system check valve to prevent backflow (water hammer) between pump on/off cycles.

• When connecting suction and discharge pipework to the pump, be sure to support connections and piping to minimize pump-end strain, which leads to seal failures and casing breakage (see Figure 1).

• Use reinforced high-pressure discharge hose rated for system pressures at the discharge connection of the pump.

• Install a drain connection at the bottom of vertical pipe runs.

Pampering your pump

Routine maintenance will enhance the longevity of pumping equipment. Particularly, if operating around the clock, pumps will require routine inspection. At a minimum, this should include inspection of the following:

• Mechanical seal oil levels.

• Volute drain valve (open and close and make sure it is clear).

• Engine oil, fuel, and radiator coolant levels (if applicable).

• Grease fittings at the bearing bracket (if applicable).

• Hydraulic fluid (if applicable).

• Hydraulic line fittings and O-rings (if applicable).

• Electric cables for signs of wear (if applicable).

Electric submersible pumps may require the few observations already mentioned. Beyond that, semi-annual and annual maintenance evaluations might be all that are necessary. Long cycle maintenance should include thoroughly cleaning and inspecting for visible damage, inspecting the cable for abrasions or cuts, having an electrician evaluate the motor insulation, and inspecting the wearplate(s) and impeller.

Proper pump and hose setup is shown here.

In addition to daily maintenance, electric motor-driven and engine-powered pumps should experience routine pump-end maintenance at 250 hours of service. Once you have reviewed the engine manual for the manufacturer’s recommended service schedule, the 250-hour pump-end service should include the following:

• Flush the pump-end with clean water.

• Lock out and tag out the power source.

• Disconnect suction hose piping.

• Shine a flashlight into the suction inlet to inspect for visible wear and pitting.

• Check front wearplate clearances with the impeller for signs of wear.

• Examine and correct all hoses, belts, wiring, and connections around the motor or engine.

• Drain and replace mechanical seal oil and engine oil.

• Check and replenish grease at the motor adaptor or bearing bracket.

• If you are using a venture-style, automatic self-priming pump, disconnect the ejector assembly and inspect it for wear, including the O-rings and nozzle. Evaluate the ball, seat, O-rings and screen in the ejector and discharge non-return valve assemblies.

• Assess the compressor air lines and perform compressor maintenance per the manufacturer’s recommendations. Hydraulic submersible pumps share many of the same 250-hour maintenance tips for the pump-end and powerpack. For additional maintenance, also replace the return filter on the hydraulic reservoir. At 1,000 hours, change the hydraulic fluid and replace the suction filter.

Doing your part

Pumping in mines and quarries can be done from various vantage points. Water may be used to clean the mined product or equipment or to keep cutting tools from overheating. It may also need to be pumped up and out of a pit, from one pond to another, or from below the ground. The urgency with which water needs to be moved can also vary from routine processes to groundwater infiltration emergencies. Though forces of nature are beyond your control, pump maintenance is not. Whatever the pump and purpose, maintenance enhances operational reliability and can go a long way in stopping water from drying up your operation.

Stephanie Morgan is a technical writer for Godwin Pumps. Morgan has a degree in English — Professional Writing from Elizabethtown College in Elizabethtown, Pa. She also is a senior member of the Society for Technical Communication.

Photos and figures for this article are courtesy of Godwin Pumps.

Left to right, top to bottom: 1. Greasing the fittings at the bearing bracket prevents overheating, which can cause premature wear and vibration — and then failure. 2. If the pump does not prime, check the O-ring and the suction for signs of damage or wear. 3. When considering the space requirements for a pump, remember to consider the pump’s power source. 4. Inspect the non-return valve ball for signs of wear. 5. The flanges shown here are properly aligned to prevent strain on the pump and pipes.

Top 10 Indicators of Pump Malfunction

Make sure to always acknowledge the obvious. Simple observations provide good clues about potential problems. Be aware of these 10 indicators of pump malfunction and their possible solutions.

Problem	Solution
1. Pump does not start	Check the power supply Flush the pump clean Remove any obstructions
2. Pump does not prime	Check the lift distance Reposition the inlet/piping Remove any obstructions in the suction/strainer and/or ejector assembly Replace the suction or discharge hose Check for O-ring and gasket damage Check the seat and valve for damage Check the compressor drive and belts
3. Pump outputs insufficient product	Check the suction/discharge gauge reading Check and clear the strainer/screen Check for kinked or damaged hoses Shorten hose length or increase hose diameter Reduce total dynamic head or revisit pump selection Repair or replace the impeller Adjust throttle/speed setting
4. Pump requires excessive power	Check the impeller/pump body Revisit pump selection Adjust throttle/speed setting Check and reset impeller clearances
5. Pump vibrates or overheats	Check the impeller/pump body Check and clear the strainer/screen Repair or replace the impeller Reduce excessive suction lift Adjust throttle/speed setting
6. Pump has emulsified (milky) hydraulic fluid or seal housing oil	Drain and replace fluid or oil Rebuild/replace mechanical seal Evaluate pump cycle down time
7. Fluid temperature is high (hydraulic pump)	Top off with clean fluid Replace a worn hydraulic motor Check for obstructions
8. Fluid in the reservoir is low (hydraulic pump)	Locate and replace broken hydraulic line Replace O-ring seal in quick-release coupling
9. Pressure relief valve is high	Check for obstructions Replace filter Repair/replace quick-release coupling Check and tighten all couplings Readjust valve for 3,500 psi Check hydraulic hose length Check pump throughput
10. Motor protection trips (electric pump)	Verify that the power supply matches the motor requirements Allow the pump to cool down