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Key questions for selecting a wastewater solids handling pump

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If the liquid you’re pumping contains solids, there are a number of solids handling submersible pumps that might be appropriate for your application. To avoid clogs or burning your motor out, you need to make sure you have the right pump. There are key questions that help determine which pump will solve your problems. In this post, we’ll examine these questions so that you’re prepared when you talk with your provider.

What type of solids are you’re pumping?

Understanding the solids in your liquid helps your provider determine the right type of pump for your application. We’re focusing on wastewater, so we can assume your solids are not abrasive (abrasive solids would require a hard metal, agitator pump). Most likely, they are large and soft or long and stringy. You also need to know if the solids need to be reduced to go into your system or to discharge, or if you just need to pass them.

Large and soft solids generally need a shredder pump that will shear the materials before pumping. Long, stringy solids indicate that you’ll need a vortex pump that can pass the entire solid.

Understanding the type of wastewater is also helpful. These are generally categorized as municipal (including sewage) or industrial. While municipal wastewater is generally consistent among sites, industrial wastewater solids and contaminants often vary based on industry.

What solids loading can the pump handle?

There needs to be enough liquid either in the sump or in the system to keep solids moving with the liquid. Without enough water, the pump will clog and won’t be able to pass the solids. Most solids handling pump designs can handle approximately 5% solids by volume. If your wastewater has a higher concentration, you will likely need to add more water to the sump by changing the system to allow more water to accumulate in the sump or by adding more water to the process.

The sump pump basin size is also a factor. The basin should be sized to minimize the number of cycles per hour but cannot be so large that solids will settle instead of being brought into the pump.

How might your piping system affect the pump you need?

Understanding the design of your piping system will help your provider make sure there are no areas where the solids may settle, build up and cause clogs. This includes:

  • Size of the Piping: It must be large enough to pass solids downstream, but small enough to maintain carrying velocity to prevent solids from settling out. We recommend carrying velocity of 5-7 ft./sec. for municipal wastewater applications. As the specific gravity of the solids increases, you may need to further increase the velocity to carry the solids.
  • Vertical Lift: This is the height that water has to travel as it moves through your piping system. A significant vertical lift combined with an improperly sized pump can cause solids to recirculate and clog within the pump volute.
  • Location of Check Valves: The check valves should be as close to the pump as possible. If too far from the pump or too high, solids can build up before reaching the valve. This causes clogging as the solids backflush into the pump. Adjusting the location of the check valve generally solves these issues.

In some instances, your provider may conduct an inspection. If the entire piping system isn’t visible, you may need to show the piping system plans or explain where and how far the piping goes. The piping connections and fittings are important too.

What is the required flow rate for your system?

The flow rate is the amount of liquid that runs through the system in a given amount of time. This and the pipe sizing determine the velocity needed to pass the solids downstream through the pipes. The flow rate also indicates the appropriate size your sump should be. An undersized sump causes the pump to cycle too frequently and burn itself up.

If you don’t know your flow rate, here are two options to help your pump provider determine it:

  • Calculate the flow rate by performing a draw down test. With no water entering the sump, allow the current pump to run for as long as possible while recording the time in operation. The flow rate is the volume of liquid pumped (sump length x sump width x the change in liquid level from start to end of pumping cycle) divided by the amount of time recorded during the drawdown test.
  • If you have the model number of your current pump, researching the pump’s performance curve combined with the piping system information or a pressure gauge reading in the system can help your provider calculate the flow rate.

Translating answers to the solids handling pump you need

The answers to these questions provides the information your provider needs to make a recommendation. The natures of the wastewater and solids determine the type of pump you need (i.e. shredder or vortex pump). The flow rate (and the amount of head in the system) indicates the specific pump model you need.

In addition, you may have unique circumstances to consider, especially when dealing with harsh environments. These are the types of situations in which BJM Pumps excels. We build submersible pumps to deal with rugged applications and have 35 years of experience helping customers dealing with the issues you deal with every day. Contact us or call us at 860-399-5937 to request more information or to initiate a personalized evaluation of your submersible pump needs.

 

I manage the editorial affairs for MONETA Tanıtım, which produces specific publishing, specially for the sphere, Turkey industry. We work for content development through digital and print media, with a new generation, dynamic publishing intellection.

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Pumps

Water Pump Market and Infrastructure Development

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Water pumps are the ancient and best widespread machines, which are used in wide range of applications. They are different products which are configured, engineered, and are standardized using significant secondary equipment. Newly developed water pumps offers improved act and perform reliability with well-organized and effective results. They are classified on the basis of methods of displacement including centrifugal pumps and positive displacement pumps.

Water pumps are used and operated in a huge range of end use industries including waste water treatment plants, chemical, oil and gas, and several industries including food and beverages, pulp & paper manufacturing, power generation, and mining.

The important factors that are anticipated to increase demand for water pump are increasing usage of water pumps in the oil & gas sector, rising demand for energy especially in developing countries, and advent technologies in water pumps enabling efficient separation processes for gas and liquids. In addition, rising need for wastewater treatment in the industrial sector and rapid infrastructural developments the ongoing developments in the industrial sector, especially in power and energy and agriculture.

Growing reliance on groundwater for other agricultural purposes and irrigation instead of monsoons in developing nations, such as India, is expected to increase the demand for water pumps in the agricultural sector is also driving the market growth. In addition, government initiatives for recycling wastewater for reducing water pollution globally. The major factor that hampers the market growth is decreasing the cultivation and farming of agave plant, fights in Mexican countries, rising energy and fuel prices.

One of the opportunity observed in the target market is need to drink clean water for maintaining a disease-free and healthy lifestyle, the construction of water recycling industries, and the increasing demand for solar water pumps.

The global water pump market is segmented into type, application, and region. Type segment is sub segmented into reciprocating pump, centrifugal pump, and rotary pump. Centrifugal pump segment is growing due to they are usually used in various applications and are available in various configurations including single-stage pumps, axial and mixed flow pumps, multi-stage pumps, sealless and circular flow pumps, and submersible pumps in order to encounter the problems associated with flow control across various end use industries. Application segment is sub segmented into oil & gas refines, chemical, and water & wastewater. Water and wastewater is growing due to higher investment in power & energy sector in emerging economies.

North America has the largest share for the water pump due to increasing domestic and household activities in developed nations, like Canada and the U.S coupled with rising government initiatives in the U.S. for recycling wastewater. Asia Pacific market register significant share due to high growth in water & wastewater treatment and power sector. Europe is also having the moderate growth share due increasing water scarcity and higher demand for better sanitation in UK, Germany, Spain, and France. (Source: scoop.market.us)

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A lot of hot air

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Water treatment facilities rely on filtration systems to remove waste products as part of the process to recycle the water before it returns to the river. These filters are periodically cleaned by backwashing them with air bubbles produced by large blowers. Following two unexpected blower failures, Sulzer was asked to investigate the cause and improve the reliability of the system.

In the UK, one of the regional water companies has an agreed framework contract with Sulzer for the repair of the blowers on its sites. The contract came about through a need for the company to have a single source for blower repairs, rather than having to deal with numerous original equipment manufacturers (OEMs). Fortunately, Sulzer has engineers at its Bristol Service Center that previously worked for blower manufacturers and can offer considerable expertise to the customer.

Matt Knight, blower repair engineer at Sulzer, explains: “We have a contract to repair blowers from any manufacturer. All the work that Sulzer carries out is done in-house, which means that the customer always knows how a repair is progressing and they can come and see for themselves.”

Unexpected problems

In this case, the water treatment works operates three blowers as part of a complex cleaning cycle for the media in its filtration system, but two of them had failed in quick succession and been sent to Sulzer’s service center. The repairs were completed, and the assets returned to be installed by the site’s own engineers.

The maintenance team on the water treatment works had only just reinstalled the two repaired blower units and shortly after they were commissioned, they failed again. This left the aeration process with only one blower, the bare minimum for operation, but there was also considerable concern for the reliability of the remaining unit.

The units were removed once again and returned to Sulzer’s service center. Once they had been stripped down, it was clear that they had both suffered from overheating which had caused the rotors to expand and become seized.

The intensity of the heat build-up in the blowers was evidenced on one of the units by the fact that the plastic cabinet extraction fan had melted. Once the blowers had been disassembled, it was found that the rotor had friction-welded itself to the housing.

The fact that both blowers exhibited the same failure mode, suggested that the cause of the problem was not related to the unit itself, it was more likely to be a restriction, either on the inlet side or in the discharge line.

Investigation resolves issue with blowers overheating

Matt continues: “We have a very good working relationship with this customer and the blower repairs are just one aspect of the service we provide. The fact that we complete all of our repairs in-house gives us complete confidence in the quality of the repairs that we deliver. It also means we can give progress updates whenever they are required and return the repaired equipment with minimal delays.”

As soon as the blower repairs got underway, Sulzer offered to carry out an investigation at the treatment works to find the root cause of the problem. The engineers inspected the inlet filters along with the discharge pipework, using a borescope, but no obstructions were found.

Attention then turned to the pressure relief valves (PRVs), which were situated inside the acoustic cabinets, and should have lifted in the event of the blowers operating against a restriction or excessive load. Both PRVs were removed and found to be seized, however, while this accounted for the failure of the blowers, these valves were not the cause of the restriction.

Understanding the application

The blowers operate on a 24-hour cycle, producing scour air that backwashes the filter media. During the cleaning cycle, the blowers are not required to operate all of the time, and they are regulated by an unload valve, which vents excess air to the atmosphere. This avoids stop/starting of the blowers during the cleaning cycle.

All three blowers are regulated by this valve, and closer inspection found that the diaphragm chamber was full of water, preventing it from operating. This, combined with the PRV failures, had led to the blowers becoming distressed very quickly; only the proper function of the remaining PRV had prevented the last blower meeting the same fate.

The unloading valve was stripped and cleaned, but the recommendation was to replace all of the PRVs as well as the unloading valve to be sure the blower circuit would continue to function reliably. With over 15 years of service, these valves had performed well, but without a regular maintenance schedule, their operating condition remained unchecked.

Delivering the solution

While the on-site investigation was completed, the engineering team at the Bristol Service Center removed the damaged rotors and, using OEM drawings, machined the rotors and the casing back to original dimensions, ensuring the correct clearances were provided. The blowers were reassembled and returned to site, where they were reinstalled.

The Sulzer engineers compiled a field report for the customer that detailed the findings of the investigation and recommended implementing a maintenance routine for the PRVs, the unload valve and the non-return valves, to ensure continued, reliable operation.

Matt concludes: “Without the on-site investigation, we could have just repaired the blowers and they would have continued to fail. The combination of our technical expertise and application knowledge has been invaluable in resolving this issue and ensuring long-term reliability for our customer.”

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Mastering the waterways of Fuzhou

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In the capital city of China’s Fujian province, water is plentiful. Located by the sea and established on top of several rivers, commanding the water has always been key to the people living here.

People say 100 rivers run through Fuzhou. Water has been shaping the city since it was founded more than 2000 years ago. For better and worse. Sharing the riches of
the nearby sea with the citizens and pouring rain from the neighbouring mountains on to them.

Today, water remains a decisive denominator for Fuzhou. It is now attracting the eyes of China, when cities from near and far seek inspiration as to how to effectively manage water, being one of the country’s Sponge Cities. Societies, where smart design and solutions allow them to absorb, integrate and treat water in ways that help preserve the resource, and handle the effects of problems like flooding.

“We experience many challenges with water. During rainy periods, we have all too much, while the dry periods leave our waterways stagnating. That is one reason why we depend upon our floodgates to distribute water to where it should go, whether it is too much or too little,” says Pu Jiang, CEO and Co-Founder of Fuyuanxing Mechanical and Electrical Company.

Better living, great reliability

Wang Chuan Qi walks around the floodgate. He routinely inspects the station, making sure everything is running as it should. It is. He has primary responsibility for its operation at this point. This floodgate is built on top of one of the city’s many small rivers, the Chating. And here, its main function is usually making sure the waterway does not stagnate and leave water black and smelly, and a nuisance to the citizens of the area.

“It has to work. Always. Normally to make sure that water flows satisfyingly to the benefit of the people living here, but also in times with a risk of flooding. From my perspective, one of the great things about this solution is that the great performing Grundfos pumps are installed directly in the floodgate, which makes them easily accessible for service and maintenance. This allows us to conveniently make sure things work at all times,” says Wang Chuan Qi, Vice General Manager and head of the engineering team at Fuyuanxing. 

He is supplemented by Mr Song Zhi Guo, General Manager for the Fuzhou Water Environment Project at the Beijing Enterprises Water Group, and he is particularly happy about the support his company has gained from Grundfos, and the new options the floodgates present to him:

“Grundfos devoted its core products and competencies to the project in Fuzhou. The technical competence of the team and the user-friendly equipment have won great recognition from our company and Fuchou Municipality as well. With the pump gate system, we are able to create flow in the waterways. Residents can walk and live along the river. They are very pleased that clean water is brought to their doorsteps,” he says.

Perfect stepping Stones

While the pump gates of Fuzhou help ensure the right flow in the city’s rivers, they also attract the right attention. The Sponge Cities are great examples to follow, and this makes being part of their solutions highly valuable. The solution in Fuzhou is quite unique. The propeller pumps are built directly into the floodgates, allowing both ease in operation and maintenance, when performing their important task.

“Managing water intelligently is one of the largest challenges society faces. In China and globally. Being part of the solution in Sponge Cities like Fuzhou allows us to put our expertise to work in solving issues of flooding, while also making the city more pleasant to live in, thus making a difference for the people and supporting the Sustainable Development Goals. While also developing our own knowledge, so we can continue to make a difference,” says Leo Jie Zhang, China Business Managing Director, WU at Grundfos.

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