Centrifugal pumps are commonly used in chemical processing applications to move liquids efficiently. These versatile pumps provide reliable flow while handling aggressive chemicals and fluids. In this article, we will explore what makes centrifugal pumps well-suited for chemical processes and discuss key considerations when selecting, operating, and maintaining them.
How Centrifugal Chemical Process Pumps Work
Centrifugal pumps work by spinning liquid to create flow. The basic components include an impeller, casing, shaft, seal assembly, and bearing frame. The curved impeller spins on the shaft inside the casing. As it rotates, the impeller generates centrifugal force that accelerates fluid outwards. This moving liquid applies pressure to the casing, forcing flow through the discharge port. The pump casing guides the liquid to and from the impeller.
Centrifugal pumps create flow by adding velocity and kinetic energy to the fluid. The smooth, non-turbulent flow minimizes shear and protects the integrity of the pumping liquid. Centrifugal pumps provide continuous flow at various pressures and capacities by adjusting impeller size and speed.
Centrifugal Chemical Process Pumps Applications
Centrifugal chemical process pumps find extensive use in the chemical industry, where the handling of corrosive, toxic, and hazardous fluids is common. These pumps are employed in processes such as chemical transfer, acid circulation, solvent recovery, and wastewater treatment. Their ability to handle a wide range of chemicals makes them indispensable in chemical plants, refineries, and pharmaceutical industries.
Benefits of Centrifugal Pumps for Chemical Processes
There are several key reasons why centrifugal pumps are well-suited for handling chemicals and liquids in industrial processes:
Handles Viscous Fluids: The centrifugal pumping action can efficiently move high-viscosity fluids like oils, syrups, and slurries containing solids. The semi-open impeller handles shear-sensitive fluids with minimal degradation.
Full Flow at Startup: Centrifugal pumps provide full flow instantly upon startup unlike positive displacement pumps. This allows faster startup of processes.
Low Shear Hydraulics: The smooth flow pattern gently handles fragile compounds like polymers and proteins. Shear forces are lower compared to other pump types.
Handles Air Pockets: Small amounts of air or gas do not affect centrifugal pump operation or create air locking issues. Trapped air can freely pass through the impeller.
Higher Flow Rates: Centrifugal pumps excel at higher flow rates and heads compared to positive displacement pumps. The high flows help quickly fill tanks and speed production.
Easy Maintenance: Centrifugal pumps have straightforward designs with easy external access for maintenance and repairs. Dynamic seals and mechanical seals can be replaced quickly.
Self-Priming Models: Many centrifugal pumps are self-priming, removing the need for foot valves and external priming equipment. Self-priming centrifugal pumps contain an internal chamber that primes automatically.
Selecting Centrifugal Pumps for Chemical Processes
Several factors must be considered when selecting an appropriate centrifugal pump model for chemical process applications:
Materials of Construction: The pump must be made from materials that withstand the chemical, pressure, and temperature conditions. Common materials include stainless steel, alloy steel, bronze, titanium, and exotic alloys.
Capacity and Pressure: Determine the flow rate, head pressure, and suction conditions the pump must handle. Add safety factors for future capacity needs.
Viscosity: Higher viscosity fluids require impellers designed to handle viscous liquids and prevent shear degradation. Consider gear pumps for extremely thick liquids.
Abrasion: When pumping abrasive slurries, select hardened pump components and thicker clearances. Consider a vertical cantilever pump configuration.
Sealing: Determine if the fluid is compatible with mechanical seals or if packing is required. Double seals prevent leakage of hazardous compounds.
Safety: Explosion proof motors and close-coupled designs enhance safety for combustible chemicals and hydrocarbons.
Proper Installation of Centrifugal Pumps
Correct installation is critical for proper operation and long life of centrifugal pumps. Here are key installation guidelines:
Mounting: Mount pumps on sturdy foundations according to manufacturer specifications to minimize vibration. Ensure adequate NPSH available by keeping suction piping tight.
Alignment: Carefully align pump and driver shafts to prevent premature wear on seals and bearings. Use dial indicators when aligning coupled pumps.
Piping: Install piping to allow future maintenance access to the pump. Keep suction lines short and straight with few elbows. Ensure adequate pipe supports and allow for thermal expansion.
Monitoring: Install gauges to monitor differential pressure, flow rate, temperature, vibration, and power. Monitors allow early detection of potential issues.
Priming: Follow manufacturer's instructions when priming end-suction and self-priming models before startup. Avoid running pumps dry.
Direction of Rotation: Double check motor rotation matches the direction indicated on the pump casing before starting. Incorrect rotation can seriously damage the pump.
Safe Operation Tips
Adhering to safe operating procedures prevents issues when running centrifugal pumps:
Monitor: Check vacuum and discharge gauges and flow meters to ensure proper operation within design limits. Observe for leaks, high vibration and abnormal noise.
Throttling: Avoid excessive flow throttling which can increase temperatures. Throttling the suction can cause cavitation damage. Use bypass lines or recirculation to control flow.
NPSH: Ensure adequate NPSH during startup and operation to prevent cavitation. Cavitation bubbles collapse violently, eroding impeller surfaces.
End of Curve: Do not operate pumps at the far right of the pump curve near shutoff head. The steep curve can lead to instability and mechanical problems.
Minimum Flow: Maintain flow above the minimum flow recommendation from the manufacturer to prevent overheating damage and seal failure.
Clearance: Monitor pump clearances and realign couplings or replace impellers when clearances exceed recommended values. Increased internal leakage reduces performance.
Contamination: Keep pumped liquids free of solids by using inlet strainers. Abrasive particles rapidly wear internal surfaces.
Reliable Maintenance Practices
Developing a comprehensive preventive maintenance plan is crucial for maintaining reliability and longevity of centrifugal pumps. Here are key maintenance best practices:
Inspections: Perform frequent visual inspections of pump seals, packings, bearings, alignments and clearences. Check for leaks, high vibration and noise.
Lubrication: Ensure bearings are greased regularly per manufacturer specifications. Insufficient lubrication causes premature failure.
Seal Servicing: Repair or replace mechanical seals and seal support systems at first signs of leakage to prevent damage of pump components.
Wear Ring Replacement: Periodically replace worn impeller rings and casing rings to maintain pump efficiency and minimize internal recirculation.
Fastener Torquing: Re-torque cover bolts, packing nuts and foundation bolts to factory specifications. Loose parts can lead to leaks and vibration issues.
Alignment: Check pump and motor alignment on a yearly basis minimum to prevent premature bearing and seal failures from misalignment.
Spare Parts: Keep spare parts like seals, wear rings, bearings, and gaskets in inventory to allow quick repairs and reduce downtime.
Staff Training: Have maintenance staff properly trained to install, maintain, and troubleshoot pumps according to manufacturer standards.
Following basic best practices keeps centrifugal pumps operating reliably at peak efficiency for chemical processing applications. Partnering with reputable pump suppliers also provides valuable technical expertise. With proper pump selection, installation and maintenance, centrifugal pumps will continue performing safely for years.
Need help selecting the right Chemical Process Pumps for your application? Contact us at firstname.lastname@example.org or +86 15032857866; Our technical sales engineers have the extensive product knowledge and will be able to help you.
Here are a few of the Chemical Process Pumps made by An Pump Machinery, a reputable manufacturer of centrifugal pumps.