Key Questions to Ask When Ordering single screw pump

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All pumps and pump suppliers are not created equal. Furthermore, pumps, especially rotary lobe pumps, are not one-size-fits-all. Make sure you have the information you need to make an informed purchase for a pump that will get the job done for you.

Q: What is this pump designed for?

A: Each style of pump is designed to tackle specific tasks. Some have a wider range of tasks they can perform compared to others.

For example, the centrifugal pump was designed to efficiently pump clear, clean liquids with viscosities similar to water. This is why they are generally less expensive than other pump styles. Progressive cavity pumps were designed to pump thick, viscous material with some solids efficiently. Elastomeric rotary lobe pumps were designed to pump manure and other various viscosities and solids efficiently. 

Q: What is my long-term investment to price ratio?

A: Most global pumping applications are pumping clear clean fluids similar to water. Pumps that are designed to handle other materials and fluids are more expensive because they are niche applications. It's important to consider that the family of pumps designed for the application closest to your needs may not be the lowest priced offering in the short term, but they very well may be the most cost-effective solution over the life of the equipment. A cheap pump is not a good buy if you have to routinely replace it due to failure because it is a poor fit for your operation. Read more about the total cost ownership of a pump.

Q: How many pumps do I need, based on the skills of my maintenance crew?

A: It is vitally important to know whether repairs can be done in-house, or if you will need to send the equipment out for repair. Pumps that need outside repair often come with a service contract that adds to your long-term cost. And sending a pump out means downtime if you don't have a backup. Know if your pump has to be sent halfway across the world for service.  

If the pump can be serviced in-house, you then need to look at your in-house resources. If you have a crew full of MacGyvers, you can get by with one pump. If your maintenance crew has problems telling a wrench from a hammer, you probably want to have a backup piece of equipment. If you have an average crew, you need to consider how critical the application is to determine whether you need a backup pump or not. If you can do the repairs in-house, it is best to keep spare parts on the shelf to minimize downtime. If you'll be keeping spare parts on hand for in-house repairs, it makes sense to have a pump that has fewer and smaller parts, making it easier to keep the pump up and running and taking up a minimum amount of inventory space. 

Q: How hard is it to get ahold of my sales rep?

A: You may think you have a handle on your pump operations. However, it is often not as important to have all the answers, as it is to know where and when to get answers and assistance. How many times have we gotten a piece of equipment that works great, but when it fails, we can only call the service center between the hours of 7 and 9 a.m. CST because the plant is located in Europe or Asia? Or worse, they have a local sales office you assume you can rely on, but they are unable to answer your questions or will not return your calls. Always make sure you have a quality local representative or manufacturer's representative that you can reach quickly when it matters most. It makes a world of difference in protecting your equipment and keep it operating at its best performance.

Q: How hard is it to get spare parts?

A: You bought the right pump for the application. You have a top-notch maintenance crew. You have a backup pump because it is a critical application. You have a world-class local rep. Unfortunately, someone forgot to open the suction valve when the backup pump kicked on and the pump has cratered. You get your rep on the , but unfortunately the parts for your pump are made one Tuesday a month, and it's Wednesday morning' Does your manufacturer have a good supply of spare parts ready to ship to you quickly? If not, ask your local representative if they can carry some on the shelf. Failing that, you may need to spend additional money to carry some increased inventory on your own shelf.

Q: Does your pump manufacturer have good technical support you can access directly?

A: Let's face it, not every question is going to be able to be answered by the sales rep. You need a good reliable contact at the manufacturer who can help guide you through difficult applications or provide some guidance to extend the life of your systems.  

Q: Does your manufacturer offer factory training?

A: You can have the best maintenance crew in the land, but without proper training, they may not understand the nuances of a specific pump design ' like the difference between a casing O-ring and a seal O-ring. Having your maintenance personnel go through factory training is critical to minimizing your downtime by giving them all the knowledge necessary to keep your pumps operating at peak efficiency and getting them back up to operating conditions when things go wrong.

Q: Does your pump manufacturer have quality local representatives who can help your crew out of a jam?

A: We've all been there: your dewatering equipment has gone down and your crew is hard at work putting out the fire. Now, your primary clarifier pump has gone down and you're expecting a storm to come through. Having a local rep that not only understands your pumps, but has factory trained personnel that can come out and help get you back up and running in a pinch, is invaluable.

If you're considering a Vogelsang rotary lobe pump, here is an easy rundown of answers to those questions:

If you are looking for more details, kindly visit Shuanglian.

• Vogelsang salespeople and distributors are trained experts in pump technology, so they can help you choose the ideal pump for your specific needs. Find a local dealer/distributor here.
• Vogelsang pumps can be serviced in-house and on-line. Watch a video overview.
• Sales reps and distributors are glad to offer quotes that include the initial and long-term costs of your pump that includes spare parts, service work, etc. 
• Vogelsang has a global sales network with a manufacturing facility in Ravenna, Ohio, that carries parts on the shelf. 
• Vogelsang offers factory training several times a year at no cost to the end user (you make travel arrangements, they put you up in the hotel and feed you during training.) Get details here.
• A nationwide network of local reps offers local service that can get you out of any jam.

Visit the Vogelsang Storefront

Below are some of the frequently asked questions regarding screw pumps: -

What type of media can be handled by screw pumps?

Progressive cavity type screw pumps are used for highly viscous, heavy, abrasive, and aggressive media like potato pulp, cement slurry, mine water, sugar molasses, sludge, fruit pulp, municipal solid waste, phosphate dosing, milk of lime, slurry, animal feed transfer, high consistency pulp, viscous adhesives, edible oil, resin, solvents and binding agents etc.

What is the working principle of progressive cavity type screw pumps?

The screw pumps work on the principle of rotary positive displacement system. The main component, a metal-single threaded rotor, rotates around its principal axis and also around the axis of the stator section producing cavities at reduced pressures, which move axially from inlet to outlet.

Are screw pumps self-priming?

Yes. Screw pumps are inherently self-priming.

What Capacity and pressure can a single screw pump handle?

A single screw pump can handle capacity up to 300m3/hr and pressure up to 48 Kg/cm2 generally. Each manufacturer has its own range. It does not cover downhole screw pumps.

What are the distinctive features of single screw pumps?

Some of the distinctive features of screw pumps are-

• Single screw pumps are positive displacement type pumps. These pumps can handle solids in suspension or media containing a high percentage of solids.
• Due to the reversible rotation capabilities, progressive cavity pumps can perform with equal efficiency in either of the directions.
• These are silent running pumps which have separate bearing housing. It enables the fluid to flow with no contamination.
• Single screw pumps have high mechanical efficiencies which helps in extra power savings.
• Screw pumps also have low downtime losses.
• Screw pumps are non-clogging. They can handle solids in suspension or media containing a high percentage of solids.

What type of drive systems options are available with screw pumps?

Screw pumps can be run through following types of drive arrangements-

• V-belt/Pulley type drive system
• Geared motor drive system with flange mounted motor with driven coupling
• Gearbox with electric motor with drive and driven coupling

What importance does drive system has in the pumps?

The selection of drive is really important. The starting torque depends upon fluid being pumped. Slurries and viscous fluids shall have higher starting torque values. The selection also depends upon compression fit between rotor and stator. Viscosity correction factor should be taken into account while calculating drive power required. The drive should have torque values higher than that required by the pump at all times; during start as well as during operation. Drive manufacturer's published data should be consulted to select proper drive.

Can these pumps be customized as per requirement?

Yes. Screw pumps are versatile in nature. Each pump can be customized on the basis of the duty parameters. Refer to the enquiry format as shared in pump specification sheet.

• Media to be handled-
• pH-
• Presence and size of solid particles-
• Flow rate-
• Discharge pressure required-
• Viscosity of fluid-
• Temperature-
• Duty Conditions (Continuous/ Non-continuous)

What precautions should a buyer take before installing and running the screw pumps?

Screw pumps, if installed with all precautions and instructions given by the supplier, prove to last for 25- 30 years in terms of life. The most important precautions to be taken care of are-

• Pump should NEVER run dry.
• Flushing line provision to be given in the pumps. Flushing the pump with normal tap water is required before starting and after stopping the pump as the liquid/media has the tendency to jam/solidify.
• Foundation and grouting of the pump should be strong to avoid any vibrations in pumps.
• Timely replacement of small/fast moving parts due to operational wear and tear to ensure that life of bigger parts is not effected.

SCREW PUMP

SPECIFICATIONS SHEET-

Should be as per pump type

While sending us single screw pumps enquiries many buyers share with us the standard technical enquiry sheet of other type of pumps like centrifugal, gear pumps and various other technology pumps while asking for screw pump. We have been discussing with the buyers time to time that there are multiple parameters which are applicable for one pump type but not for other pump type. We suggest the below while enquiring for screw pumps-

The client must keep in view following points while sharing the enquiry-

• Single screw pumps are not cost- effective and efficient on water.
• If a pump designed for viscous fluids is run on water, then -
  • At slow speeds the slip will be more,
  • Volumetric efficiency will be low,
  • Installed motor for viscous product will run inefficiently,
  • Mechanical efficiency will be low,
  • This clarifies why absorbed kW on water is more than the liquid power.
• On water or water like fluids the same model can be run at much higher rpm; implying that for a rated capacity we can select a lower model at higher rpm; entire characteristics of the two pumps on two different liquids water and viscous fluids will be different.
• Impeller is not applicable in screw pumps as it is a part of centrifugal pump.
• Pump shut-off Head, suction specific speed or critical speed is not applicable for single screw pumps.

Therefore it's important to restrict the data sheet to the actual fluid /pump type ONLY.The client must specify following:

• Sealing pattern- whether the requirement is for pump with gland packing or mechanical seal
• Drive system- whether the preferred drive system is V-Belt pulley driven, geared motors with driven coupling or motor and gear box with drive and driven coupling.
• VFD- Whether the pump will be operated with VFD or without VFD.
• Material of Construction- Preferences for MOC of pump parts like casing, rotor, stator etc. NOTE: If any data is not available with the client, it is always advisable to discuss the same with pump supplier and vice versa.

It is important to note-

• Capacity cannot vary once the rpm is fixed.
• NPSHA cannot be negative. If it is negative, liquid will not reach the pump and the pump will run dry.
• NPSHA should always be greater than NPSHR.
• Mechanical efficiency of the pump is dependent on capacity, differential pressure, measured absorbed kW and design of pump.
• There is nothing such as cold efficiency/hot efficiency in progressive cavity type pump.

Courtesy: Risansi Industries Limited : @risansi.com Web: www.risansi.com