Industrial Pumps Blog

Positive displacement pumps operate by trapping fluid and physically moving it through the pump to the discharge outlet. There are two principal types of positive displacement pumps; rotary and reciprocating.  In this post we will deal with reciprocating types of positive displacement pumping systems.

Examples of reciprocating pumps include pistons, hand water pumps and windmills. Though they are still in use today for certain applications, they have largely been displaced by more efficient pumping mechanisms.  However, in the 19th Century and during the height of the Industrial Revolution, reciprocating pumps played a huge role in the economic development of both Europe and the United States.

Reciprocating pumps operate by the use of a plunger, piston or some form of diaphragm.  The operation of the plunger or piston acts to create a vacuum which acts on the fluid (i.e. suction), and this moves the fluid in the direction of the vacuum. The reciprocating pump may be a “simplex” or single cylinder pump or multiple cylinders may be used.  Reciprocating pumps tend to be produced in duplex and triplex forms, though there are some examples of quad cylinder mechanisms.

In addition to the number of cylinders, reciprocating pumps are further classified by how they “fire”, i.e. the pump can be a single action suction creating and discharge mechanism or it may have a double action so that suction operates in both directions (as does discharge).

Reciprocating pumps can be powered by a variety of energy forms including water, air, steam and belt-driven motors.  Clearly, these pumps are forerunners of modern pumping systems, but they are relatively inefficient and suitable for pumping relatively small amounts of fluids, typically water.  Modern applications of reciprocating pumps include managing highly viscous fluids, such as concrete.  Reciprocating pumps tend to be chosen where there is a need for a low flow rate to be delivered against high resistance.

Positive displacement pumps come in two main flavors: rotary and reciprocating.  Both have similar operating function; however there are distinct differences and applications for each type of industrial pump.

Rotary displacement pumps use rotation to create a vacuum which creates suction to draw fluid through the pump. The vacuum created displaces the fluid through the pump into the discharge pipe, hence the name positive displacement.  Rotary pumps are extremely efficient in operation as air is removed from the pump lines by the rotary action and this removes any need for air bleeding from the lines which is a manual operation.

There are some drawbacks to rotary pumps.  The differential between the moving, rotating parts and the pump enclosure are extremely close, which means the pump speed is limited to avoid erosion and excessive wear. High speed operation of rotary pumps generally leads to enlargement of the differential and a loss in pumping efficiency.

There are three main types of positive displacement rotary pumps.  The simplest are gear pumps which use two gear mechanisms aligned in parallel with enmeshed teeth.  The turning of the gears creates a flow of fluid between the teeth and outer body of the casing, with the fluid being discharged. Gears with a large number of small teeth generate a regular flow while larger and fewer gear teeth generate a pulsing flow which tends to flow in gushes.

Screw pumps are more complex and are comprised of two screws with counter threads which turn in opposition to one another. The screws are placed upon shafts with gears on them which are enmeshed with each other to generate a uniform turning movement of the two threads. The turning motion generates a fluid flow through the pump, but again the differential spacing between the pump casing and rotating threads must be minimalized to ensure efficient operation.

Finally, moving vane pumps comprise of a rotor mounted inside a cylindrical casing.  The turning rotor causes fluid flow between the pump housing and rotor which creates fluid flow through the pump.

Oil fields that were ignored several years ago are now considered a viable proposition. Oil reserves are falling, but the need for oil is increasing, despite many attempts to try and move away from using it. Smaller oil fields are often located in extremely remote locations and once the oil has been discovered it needs to be transported many thousands miles. The only way get crude oil from remote place to the oil refinery is through oil pipes and to move the oil on its journey pumping systems have to be installed along the way.

The process of pumping crude oil between oil field and refinery is complex and consumes excessive amounts of energy and energy is highly expensive.

Cost margins have never been tighter, but the process of transporting crude oil is a major area of cost. It’s necessary for oil producers to look at efficiencies for transporting crude oil. Old pumping systems are inefficient: they use more energy and require substantial maintenance. Additionally, environmental controls in all areas are increasing fast and this is particularly the case for oil producers who are specifically targeted to reduce their carbon footprint.

Oil producers need to find ways of improving crude oil transportation, reduce costs, become more efficient and recognize their responsibility to the environment. This can be achieved in a number of ways and many oil producers have now partnered with companies that specifically analyze the pumping and transportation systems and produce solutions to increase efficiency and reduce costs. Improving efficiency generally means that the rate that crude oil is transported increases and results in higher production and less cost. The result is good for the environment and those invested in the oil industry.

It’s important that oil producers continuing to adopt technological changes both now and in the future.

Crude oil is likely to have traveled several thousand miles and undergone various processes and treatments before it is suitable for delivery to a customer. Oil fields are often in remote places and crude oil has to pass through highly complex pipeline networks on its journey. It can be transported by oil tankers by land and sea. All these methods consume substantial energy and increase costs considerably by the time the crude oil is refined.

There are several challenges facing the oil industry:

• Reducing the cost of energy consumption between oil field and oil-refinery
• Reducing the cost of overall maintenance and operating procedures
• Reducing the environmental impact.

These challenges have to be dealt with effectively with while ensuring that improvements are made to the process. Improvements have taken place, helped by increasing competition amongst oil producers, but cost reductions must take place and the industry needs to look at ways to streamline its operation an increase its efficiency.

One of the major cost areas is the crude oil pumping systems. They are essential for moving oil across land and under water, but many are outdated, inefficient and often fail. This results in it being an area that could vastly be improved therefore producing a reduction in energy consumption and associated costs.

If pumping systems are improved profitability increases. Efficient pumping systems use far less energy and this automatically makes the process more environmentally friendly. Additional benefits from using efficient pumping systems include reduced breakdowns and fewer maintenance requirements resulting in more oil getting from the oil fields to the oil-refineries.

Upgrading highly expensive pumping systems involves substantial initial investment, but the future returns to oil producers will more than pay-back the investment. Building new pumping systems takes time and cannot be achieved overnight. Forethought and planning are required then ultimately oil transportation costs can fall.

Power plants need to be efficient: they can’t afford downtime as this is costly. The pumping system is at the center of a pumping plant and must be reliable and operate to maximum capacity at all times. A power plant is contracted to supplying its customers with their product. The inability to supply the product, due to mechanical and other failures, can result in severe financial consequences and potential loss of business. In addition overall running costs escalate while maintenance is undertaken so the effect can three fold if a power plant has downtime.

Power plant operators need to work in partnership with other organizations that provide advice and support to ensure their power plant runs efficiently and is technologically up-to-date.

Different power plants require different skills but the knowledge gained from one type of power plant can be extensively used in another. Power plant partners need to be able to provide solutions to increase production, improve reliability and reduce costs. A partner needs to be able to prove its experience and skills and to deliver results.

Power plants deal in many aspects of oil delivery, each requiring specialist knowledge. The techniques employed and the efficiencies learned in delivering one type of fluid can often be utilized in another type of fluid so working in partnership with an experience organization has multiple benefits.

Power plant partners combine the skills and knowledge gained from operating and advising others. It’s important to ensure that they have the ability to offer help and solutions to all areas of power plant management.

Introducing and implementing the solutions presented by power plant partners improves reliability and production rates ensuring that the product can be delivered on time to the customer. A power plant benefits from increased production and improved customer relations. Costs reduce and profitability increases.

Check out any recent engineering survey and you find many, if not most, installations are fitted with oversized and underutilized pumps. Underutilization is inefficient: it costs the same to operate irrespective of whether the utilization rate is 50-per cent or 100-percent.

It comes down to built-in operational margins that increase between the original design requirements and ultimate pump installation. Designers know the required flow rate, but instead of recommending a pump that fits the flow rate they build in an extra percentage. The engineering team looks at the design recommendations but consider it sensible to allow for a greater flow rate – a safety margin. Already the pump is bigger than required so, there’s added running costs and under utilization: possibly 10-percent or more. Once the pump size has been reviewed and discussed by the various parties in the chain there’s every chance that a pump may be 15 to 20-percent bigger than required resulting in unnecessary initial expenditure and ongoing running costs.

A 20-percent oversized pump is likely to consume around 20-percent more energy, but aside from the extra running costs and under utilization, other factors are involved in fitting oversize pumps. Pumps are designed to operate at full capacity. If the flow rate is 20-percent less than the pump was designed for then it needs to be adjusted to compensate for less fluid to pass through it. Pumps operating at less than full capacity are more likely to need extra maintenance during their lifetime. Underutilized pumps suffer from extra wear. Bearings go out of alignment then the pump starts to vibrate and this makes for further wear. The pump has to shut down for costly repairs and so the flow rate ceases while the pump is being repaired.

The more times this occurs the less efficient the installation becomes and efficiency and costs are interlinked.

After the electric motor, pumps are the most ubiquitous machine in the world and as such, they have a tremendous impact on how much of an impact we make upon our environment.  We rely upon pumps to deliver clean drinking water, to deliver fuel to our car engines, to make our refrigerators and washing machines work, and so many more applications. In this instance, we refer to “greener pumping systems” as ones which use less energy or utilize fewer material resources in their construction and design.

Reducing energy consumption by pumps is a highly effective way to make pumping systems greener.    The primary opportunity to make pumps more energy efficient is in the appropriate application of pumping technology to the application.  Using pumping solutions which are not well-designed or suitable for the use to which they are being put will render the environmental cost in terms of inefficient energy consumption, inordinately high.

In addition, deciding upon an appropriate pump type is also essential for efficient pump operation generally and not simply energy consumption.  Inefficient pump operation will not only consume greater energy for work performed units, but will also result in great material consumption by the installation in respect of shortened life cycle and increased maintenance and repair materials required.

The road to greener pump solutions starts with a proper assessment of the pumping system and work which is required to be performed.  Immediate gains in pumping efficiency can be achieved by concentrating on pump sizing at the design stage.  The average pump only operates at 40% efficiency while 10% of pumps operate at less than 10% efficiency – more than half of pump installations are operating at less than 50% efficiency resulting in a huge waste of energy being consumed.

Greener pumping systems can also be achieved by focusing on the materials used in the construction of the pumps themselves.  Modern design tools allow for precise calculations of stress limits which means better material use can be designed into the construction of the pump itself.  By minimizing the amount of material needed in construction, a greener pump results however the pump’s structural strength and capacity are still within the design tolerances needed for the pumping solution to perform its job.

Consumers treat clean water for granted, however the notion that water is a finite resource which must be recycled and protected is gaining traction amongst the general public and legislators alike.  Water shortages and city wide water supply concerns for cities such as Las Vegas and Los Angeles are bringing the issue of water supply to the fore of the national consciousness.

Water treatment policies have tended to fall into one of three categories – disposal, biological or chemical waste treatment or perhaps a combination of all three.  The first solution, simple disposal, is becoming harder to perform due to the environmental restrictions placed upon operators by legislators and industry bodies.  This means that our water is being subjected to greater treatment processes with a view to re-using the water or allowing non-toxic water with minimal environmental impact only being discharged as effluent.

The systems required to perform water treatment or sophisticated and complex; they require careful management to continue in effective operation.  Not only are they hard to maintain and operate, they are also very expensive!

Pump Protection Issues

Incoming water flows bring with them a collection of detritus and especially damaging grit.  Protecting the entire pump infrastructure, from primary through to tertiary pumping installations, is absolutely vital to maintaining effecting waste water treatment operations.  It is not only how pumps are installed which has altered over time, but also how the water itself is subjected to pumping processes in a bid to extend equipment life and optimize operations.

Wet submersible pump units are increasingly being installed instead of traditional suction pumps.  Dry submersible pumps are also becoming more common too as the industry and suppliers have developed better solutions for waste water treatment.  The idea behind dry submersible pumps is that they are installed in a dry area but then connected to an adjacent wet pit, which means that access to the pump can be effected for maintenance and necessary repairs. (more…)

Leaking sulfur is a serious environmental issue, and in the context of an oil and gas refining operation, this is a doubly serious concern.  The oil and gas industry are one of the most regulated sectors of the global economy from an environmental perspective, and regulatory control is only likely to increase despite the strides made in delivering a reduced environmental impact.

One by-product of refining operations is liquid or molten sulfur which must be removed from refined petroleum products, particularly diesel fuel.  Recovering the sulfur also contributes to the bottom line with many operators selling the by-product to make fertilizer, detergents and for manufacturing rubber amongst other applications.

Sulfur has a high melting point, 250 degrees Fahrenheit, however it has an upper bounded range of 300 degrees Fahrenheit before it begins to increase in viscosity to the extent it will solidify once more.  The sulfur must be constantly heated above 250 degrees F, but kept below 300 degrees in order to allow effective processing operations.

This narrow bounded range puts excessive pressure upon pump mechanical seals which will soon start leaking.  This in turn contributes to equipment reliability and availability, as well as increasing maintenance downtime and costs.

A Novel Solution

Bellows seals are the traditional solution for this type of pump seal leakage, however sometimes a non-standard approach will yield a more effective result.  Instead of simply following the manual, thinking out of the box can and will help to solve the leakage problem and deliver operational benefits which are specific to an installation.

For instance, instead of a bellows seal, a pusher seal can be considered.  Using this slurry seal design, which has a spring on the air side which spring-loads the pump face, there is also a greater amount of space between the ID and sleeve OD which means that sulfur accumulations are not going to create “hang ups” as often.

The US imposed a 230-mile exclusion zone around the US coast to ensure low sulfur emissions, and the European Union followed suit with stringent new regulations on the use of low-sulfur fuels to reduce emissions.  The impact on marine shipping operators should not be underestimated, however there are very good reasons for the anti-pollution moves and pressure to further tighten the rules and enforce global reduction in emissions is intensifying.

Some industry insiders have observed that the fifteen largest merchant ships currently operating on the world’s oceans are thought to be responsible for as much pollution as all the cars currently on the roads around the world (around 800 million). The typical giant container ship is capable of emitting the same amount of carcinogens as fifty million vehicles.

The reason for such high levels of pollutant emissions from marine vessels is directly related to the fuel used; bunker fuel is low grade oil and holds up to two thousand times the sulfur content as the gas you pump into your own car in the US (or in most European countries).

The US buffer zone is expected to save around 8,000 lives on an annual basis (though US researchers found that around 60,000 deaths in the US were caused by shipping pollution).  The cost has been estimated at around USD $330 billion in annual healthcare costs associated with respiratory and heart conditions.  The main reason for the reduction in deaths due to marine shipping pollution are the reductions in particulate pollution, with sulfur pollutants reducing by 98% (due to burning ultra-low sulfur fuel); general particulates by 85%; and finally, reducing NOx pollution by approximately 80%.

The issue of marine shipping pollution is set to become of greater significance as emerging economies, particularly the Chinese, continue to grow and engage in more international trade.  The demand for a more cost efficient container ships has led to a new breed of low-cost but high-pollution ships which utilize diesel engines as powerful as those found in land-installations but powered by the high-sulfur fuel which is at the root of the emission problem.