Common Industrial Submersible Pump Questions


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Common Questions When Selecting a Submersible Pump

Our Applications Engineers receive questions daily about industrial submersible pumps from all over North and South America. While each situation is unique, there are common questions that arise especially when you’re dealing with harsh, rugged applications in any industry. In this post, we’ll share our answers to the most common questions we hear, and hopefully we can simplify your selection process – we may even clarify some issues you may not have thought to ask.

How many starts per hour can a submersible wastewater pump handle? Can a cast-iron pump handle more than a stainless steel pump?

Let’s first define what “starts per hour” means – It’s the number of times in an hour that a pump starts pumping and then stops – also known as the “duty cycle”. Both stainless steel and cast-iron BJM pumps are rated for ten starts per hour or fewer. Exceeding this number can cause the pump’s motor to overheat; over time, it can burn out the motor completely. Although cast-iron pumps tend to dissipate heat more quickly than stainless steel, neither type should be exposed to excessive cycling.

Too-rapid cycling can result from a variety of factors. For example, if you use an oversized pump, the level of flow the pump provides will overrun the input to the sump. That forces the pump to start and stop repeatedly to keep the level in the sump at the desired level.

Adjusting the float switches to provide a longer runtime reduces the number of starts/stops in an hour. Other options include using discharge valves where appropriate or variable frequency drives (VFDs). However, the best option is to ensure the capacity of the submersible wastewater pump matches the requirements of the application.

To find the right pump, always provide detailed information on the system to the pump supplier, including the level of discharge, piping, elbow, and valve types involved.  Also, share details on the geometry of the sump (its height, width, depth), fluid levels (full level, empty level), and the speed at which fluid enters the sump. This helps provide a more precise calculation for the gallons per minute requirement to satisfy the starts per hour limitation. If it turns out your system requires a heavy-duty cycle, BJM’s Fahrenheit pumps are a high-endurance wastewater pump option to handle it.

Are stainless steel pumps better suited for low pH or high pH applications?

The chemicals (and its concentrations) and solids in the fluid matter more for pump selection. Aggressive chemicals like sulfuric acid and hydrochloric acid corrode cast iron or bronze pump components, and also attack O-rings, seals, and power cable materials. Pumps constructed of plastics, 316 stainless steel, or more exotic alloys may provide greater protection against acidic and caustic chemicals, food processing residues, liquids and by-products.

For insights on which materials can stand up to specific chemicals, consult one of the many chemical resistance charts available, such as Graco’s Chemical Compatibility Guide or Cole-Parmer’s Chemical Compatibility Database.

What’s the maximum fluid temperature to which to expose a submersible pump without a high-temperature rating?

Pumps without a high temperature rating handle fluids up to 104°F (40°C), which are common in clean-up applications in food and beverage processing facilities. For temperatures higher than 104°F (40°C), BJM offers the Fahrenheit® high temperature submersible pumps, designed to handle liquid temperatures up to 200°F (93°C). Ideal applications include beverage/bottling plants, poultry/meat/dairy processing and boiler blowdown.

Pumping liquids at temperatures higher than 200°F is not recommended because water approaching the boiling point will introduce bubbles and create cavitation. When those bubbles pop, they can damage the internal surfaces of the pump over time. By eroding the surface of the impeller, they can create imbalances that lead to mechanical seal failure.

Industrial Flow Solutions specializes in the design, manufacturing, sales and service of pumping and fluid management solutions for harsh, rugged environments. With OverWatch™ Direct In-Line pump systems, BJM Pumps® products and Stancor® Pumps and Controls, we offer a comprehensive portfolio of submersible wastewater pumps and direct in-line pumps and pump controls ideal for industrial, commercial and municipal wastewater pump applications.

IFS offers problem-solving solutions for Industries including Mining & Materials, Food Processing, Construction, Commercial Building Trades, Municipal Wastewater, and Power Generation/Utilities. With over 35 years of application and design engineering experience, Industrial Flow Solutions provides you the assurance that you are getting the best-fit pump for your application.Contact one of our Application Engineers today to learn more. 860-631-3618 | flowsolutions.com

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