How to Select the Most Efficient Diaphragm for Your AODD Pump

Staff Writer
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How to Select the Most Efficient Diaphragm for Your AODD Pump

Pumps are a vital technology that helps operators complete essential processing and transfer functions in many industrial applications across multiple markets. Without this technology, these applications wouldn’t function as optimally as they do today.

When it comes to these industrial applications, making the right pump technology choice is paramount. While many different technologies exist, air-operated double-diaphragm (AODD) pumps tend to be a common choice for a diverse range of fluids, such as chemicals, food, oil, paint and adhesives, among many others.

AODD pumps work well with these fluids because of their design characteristics. These pumps, which rely on compressed air to function, can self-prime, run dry, process fluids with solids up to 3 in. (76 mm) in diameter, achieve suction lift up to 30 ft. (9 m), resist deadhead pumping conditions and even operate while submerged. AODD pumps also feature a sealless design, which keeps valuable fluids in the pump.

Even with all these perks, another careful consideration must be made to enjoy all the benefits of AODD pumps. Operators must also pick the right diaphragm from a verified supplier when selecting this pump technology for an application. This decision is critical to the safety and efficiency of the AODD pump and helps ensure – with the right diaphragm – the pump’s long-term integrity and functionality.

Pre-selection
Before selecting the proper diaphragm, operators should ensure they are making that selection from a verified supplier or one recommended by the pump manufacturer. Operators who neglect this pre-selection step run the risk of obtaining a diaphragm that is not up to the standards set by the manufacturer.

In some cases, operators could be purchasing a pirated diaphragm. In either case, these unverified parts can negatively impact the performance of the AODD pumps. Detrimental effects include performance downgrades in the pump’s operation, pump damage and the lack of a warranty and manufacturer support.

Diaphragm materials
AODD pumps have been around since 1955, giving operators plenty of time to test and review the impact of different diaphragms on this technology. Three main material families are used to categorize AODD pump diaphragms – rubber, thermoplastic elastomer (TPE) and polytetrafluoroethylene (PTFE) or Teflon. Each material provides characteristics that make them well suited for varying applications.

Rubber: Rubber diaphragms are made from synthetic rubber with a nylon fabric mesh to assist with the diaphragm’s flexibility. There are four available rubber diaphragm materials, which are neoprene, Buna-N, EPDM and Viton. Each of these materials aids the AODD pump in different applications and conditions.

For example, neoprene is a general-purpose, low-cost diaphragm designed for nonaggressive chemical applications, such as water-based slurries and seawater. It is known for its longevity and abrasion resistance. Buna-N works best with petroleum and oil-based fluids, ranging from gasoline to turpentine. Also referred to as nitrile, this diaphragm provides moderate longevity and abrasion resistance. It also functions well in food and beverage applications.

EPDM is a low-cost alternative diaphragm for pumping dilute acids or caustics. Typically found in the food, pharmaceutical, manufacturing and paint and coating industries, EPDM diaphragms are known for having good longevity and moderate abrasion resistance. On the flip side, Viton diaphragms are designed to handle extremely hot temperatures and harsh chemicals. It features exceptional performance with aggressive fluids, such as aromatic and chlorinated hydrocarbons, and has moderate longevity and abrasion resistance.

TPE: TPE diaphragms are made through injection molding, meaning they don’t require a fabric reinforcement like their rubber counterparts. These diaphragms also have four material options, which are polyurethane, Wil-Flex®, Saniflex™ and Geolast®.

Polyurethane functions as the general-purpose diaphragm, designed for nonaggressive chemical applications such as water and wastewater. Its longevity and abrasion resistance are exceptional. Wil-Flex serves as a more affordable version of PTFE. Made of Santoprene®, this diaphragm is best suited for handling acidic and caustic fluids, such as sodium hydroxide and hydrochloric acid. Because it has excellent longevity and abrasion resistance, this diaphragm is used in the chemical, pharmaceutical, wastewater and chemical industries.

Saniflex provides good longevity and excellent abrasion resistance. Made of Hytrel®, this diaphragm is ideal for food processing applications and offers low compression set characteristics. Geolast, similar to nitrile (Buna-N), is commonly used in petroleum applications due to its enhanced oil resistance and low oil swell. It offers moderate longevity and good abrasion resistance.

PTFE: Due to its chemical makeup, PTFE can be used with a wide range of fluids, even highly aggressive variations, such as hydrocarbons, acids, caustics, ketones and acetates. Featuring excellent longevity and moderate abrasion resistance, PTFE works best in food and beverage and pharmaceutical applications. PTFE, however, is non-elastic, so a backup diaphragm of a different material is required for flexibility and memory. Options for backup diaphragms are Neoprene, Saniflex and high-temperature Buna-N.

Several considerations
Operator knowledge and experience with diaphragms serve as one option for diaphragm selection. But even the most experienced operator should still look at several factors before choosing their diaphragm. As we’ve seen with the materials and their distinct properties and features, there isn’t a universal diaphragm for every application.

To determine the best diaphragm for a given application, there are seven primary factors to consider – abrasion resistance; chemical resistance; temperature ranges; sanitary standards; inlet condition; longevity; and cost.

Abrasion resistance is the diaphragm’s ability to withstand wear and friction when encountering solids and particles in the processed fluid. Chemical resistance measures the compatibility of the diaphragm’s material with the processed fluid. Temperature ranges indicate the flexibility and performance of the diaphragm at varying temperatures, as well as its capabilities in extremely high and low temperatures.

Sanitary standards come into play primarily in diaphragms used in food and beverage applications. These standards help ensure that the diaphragm complies with hygienic or sanitary standards. The inlet condition looks at a diaphragm’s capacity to move fluid from one place to another. Longevity, also known as flex life, is the expected lifecycle of the diaphragm before replacement. Cost involves multiple factors, such as initial price, rated longevity of the application, downtime expenses and diaphragm replacement labor.

Compatibility cheat sheet
With material capabilities and performance factors identified, operators can make an informed decision about what diaphragm will work best with their AODD pumps in a given application. But there is also an expedited way to guide operators to the type of diaphragms that will best suit their respective applications.

Wilden®, part of PSG®, developed a Diaphragm Selection Guide that shows which materials work best in each common AODD pump application. The guide compares and rates the longevity, abrasion resistance, chemical resistance, temperature limits and relative cost of each material type. Operators can use the guide, along with additional research and expert advice, as a snapshot into each diaphragm’s capabilities and performance in different applications.

The guide uses ratings from A to C to help operators determine which diaphragms keep the application’s maximum fluid temperature as close to the center of the operating temperature limits as possible. Wilden recommends using diaphragms with “A” or “B” ratings for the best diaphragm performance.

Additionally, Wilden has a more extensive guide for diaphragm materials and their performance when processing different chemicals. Known as the Wilden AODD Pump Chemical Compatibility Guide, this resource provides a rating system for more than 700 chemicals on different diaphragm materials.

The rating system runs from A to D, with A being the best rating and D being the least favorable. The diaphragm materials are rated against each chemical, with A meaning the chemical has a minor effect on the diaphragm; B meaning the effect is minor to moderate; C meaning the effect is moderate to severe; and D meaning that diaphragm material is not recommended for use with that chemical.

For example, EPDM and PTFE have an “A” rating when handling acetic acid, while polyurethane and Saniflex pull “D” ratings. Meanwhile, all diaphragm materials perform well when handling aluminum chloride, with each one earning “A” ratings except for polyurethane and Saniflex, which both earned “B” ratings for that chemical.

The guide also provides ratings for metal housings and plastics. The metal housings included in the guide are alloy C, aluminum, cast iron, Halar ECTFE-coated, and stainless steel. The plastics category includes acetal, nylon, polyethylene, polypropylene, PVC and PVDF.

Conclusion
Whether an operator needs to pump water, wastewater, paints, slurries, food products or acids, AODD pumps are designed to process all of them effectively and efficiently. To get the best performance out of an AODD pump, operators must select the best diaphragm for their application. The optimum diaphragm will help ensure safe, efficient and cost-effective functionality while contributing to the pump’s longevity.

Choosing the right diaphragm means carefully identifying and considering multiple factors, processes and application parameters into the equation. Considering only one or two factors isn’t adequate and can adversely impact the performance of the pump and diaphragm. Fortunately, operators have a wealth of information and guides to assist them in this process, ensuring they find the right diaphragm that functions best with their application.

About the Author:
Tom Zuckett is the AODD Business Development Manager, Americas for PSG® and Wilden® and can be reached at tom.zuckett@psgdover.com. Wilden is a product brand of PSG®, Oakbrook Terrace, IL, USA, a Dover company. PSG® is the global pump, metering and dispensing-solution expert, enabling the safe and efficient transfer of critical and valuable fluids that require optimal performance and reliability in applications where it matters most. Additionally, PSG is a leading provider of flow meters designed to reduce waste and downtime while accurately measuring, monitoring and controlling the distribution of fluids. Headquartered in Oakbrook Terrace, IL, USA, PSG is comprised of several world-class brands, including Abaque®, All-Flo™, Almatec®, Blackmer®, Ebsray®, em-tec®, Griswold®, Hydro™, Malema™, Mouvex®, Neptune®, PSG® Biotech, Quantex™, Quattroflow®, and Wilden®. PSG products are manufactured on three continents – North America, Europe and Asia – in state-of-the-art facilities that practice lean manufacturing and are ISO-certified. PSG is part of the Pumps & Process Solutions segment of Dover Corporation. For additional information on PSG, please visit psgdover.com. PSG: Where Innovation Flows.

How to choose the best grease: same viscosity, different performance

Staff Writer
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How to choose the best grease: same viscosity, different performance

Not all greases are created equal. But beyond just making sure they choose the right type of grease for an application; how can maintenance teams know which grease will perform best and last as long as possible?

Local lubrication specialists Lubrication Engineers (LE) South Africa use a brute force mechanical test tool called the “rat trap” to assess how two lubricants compare.

LE National Marketing Manager Gavin Ford explains that the rat trap test can show how two greases with the same viscosity react differently to the same force or pressure over time. Each lubricant is applied to a plate on the apparatus and then the spring-loaded clapper is released. “When we release it, it hits both plates with the same speed and force. We then compare how the two lubricants have reacted. We can snap the device several times to simulate what would happen over time or with continuous use,” explains Ford.

Picking the correct grease
However, the rat trap tool is only one element for determining if the selected grease is the right one for the intended application.

“People often think a grease is a grease is a grease,” says Ford. “However, greases are used for such a wide range of applications, their viscosity and properties vary significantly. You can get greases that are the consistency of peanut butter, toffee or honey. Obviously, each of these lubricants will behave differently,” he adds.

To measure grease consistency, the National Grease Lubricating Institute (NLGI) has created a standardised scale. It grades grease consistency from 000 to 6.  The penetration test measures how deep a standard cone falls into a grease sample in the tenths of millimeters. Each NLGI grade corresponds to a specific worked penetration value range.

Equipment manufacturers use this scale to recommend the grade of lubricant required for their equipment components, and it’s essential to adhere to this recommendation to optimise the effectiveness and longevity of equipment. “If an equipment manufacturer specifies NLGI 001 and you’re using NLGI 2, you’re going to run into problems, because the grease penetration is different,” says Ford.

The power of additives
In its greases, LE uses proprietary additives, Almasol, Quinplex and Monolec. Almasol is a solid wear-reducing additive that is able to withstand extremely heavy loads, harsh chemicals and temperatures up to 1,038 degrees Celsius. It is attracted to metal surfaces, forming a microscopic layer, but does not build up or affect clearances. Almasol minimises metal-to-metal contact and the resulting friction, heat and wear. Monolec is a wear-reducing additive that creates a singular molecular lubricating film and Quinplex is an impact-resistant additive that contributes towards outstanding water resistance.

When used as a comparative product in the rat trap test, a grease without Quinplex inevitably disperses from the plate where it’s been applied much quicker than one that contains this additive. “The non-Quinplex grease loses its tackiness and heats up far more quickly,” says Ford. “Each of our unique, proprietary additives has been designed to yield specific benefits. This is a tangible way we can show our customers just how much of a difference our unique additives can make in protecting their equipment.”

How Africa’s industrials can decarbonise, lower energy costs and increase reliability all at the same time

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How Africa’s industrials can decarbonise, lower energy costs and increase reliability all at the same time

In African countries, particularly those with a well-developed industrial sector, a significant portion of energy production may come from the industry’s own power plants. This is especially true in countries where the reliability of the grid is low, and industries rely on self-generated power to ensure a stable energy supply. In this article, we are offering insights into our approach in supporting energy-intensive industries to optimise the use of renewable energy and reach their decarbonisation objectives.

In Africa, just like anywhere else, energy-intensive businesses are under great pressure to decrease CO2 emissions as they continue to compete in the global marketplace. Wärtsilä knows more about this than most: many of our mining and industrial partners in Africa operate their own microgrids, either from choice or necessity. They want to deploy renewables but need to do it efficiently and economically. Managing power intermittency and dispatchability is not a simple task, and most businesses struggle to make the most of hybrid power configurations. We will demonstrate how renewable balancing can not only reduce the CO2 emissions of operations, but also ensure overall system reliability and lower the cost of electricity going forward.

Making the most of your assets
Each industrial site is unique, there is no such thing as one size fits all when it comes to decarbonisation. There is a whole range of constraints, conditions and variables that are specific to each operation, site, and facility. And yet, there is one central question that everyone must answer to solve the decarbonisation challenge: how can I maximise the integration of renewable energy whilst ensuring reliability of supply and competitive energy costs?

When adding renewables and intermittency into grids, managing the increased complexity that inevitably ensues in a smart way becomes critical. Avoiding curtailment, managing reserves, and optimising the fuel consumption of thermal assets are the key elements that will get you further along the decarbonisation process. At an early stage, advanced power system modelling will help understand the impact of different operational profiles, figure out the optimal power generation strategies and leverage the benefits of dispatch optimisation.

Optimising your energy generation strategy
The optimal power generation strategy must reconcile three key objectives that are often considered contradictory. The first goal is to maximise renewable energy generation to lower CO2 emissions. The second is to guarantee that the supply of power is steady and reliable. Thirdly, to ensure that the total system cost remains competitive. Fail to achieve any of these goals, and your entire plan will tumble.

This is why smart decarbonisation strategies involve a holistic view over the entire microgrid, optimising the mix of renewable energy for baseload power, backed by energy storage and balancing engine technologies for dispatchable power.

While wind and solar power can offer emission-free energy at lower costs than fossil fuels, their intermittent nature adds uncertainty into the system. Adding renewables to your asset fleet will therefore require changing the way power balance is managed in order to ensure reliability, minimise the curtailment of renewables, and reduce the fuel consumption of thermal assets. Flexible power must be available to ramp production up or down at the same rate that wind or solar production fluctuates, but also to match the fluctuating energy demand in real time.

Flexible engine power plants and energy storage systems (ESS) can work together to support renewables integration. Both energy assets can react quickly and efficiently cope with multiple daily start and stops. ESS ramp extremely quickly, while engine power plants  generate flexible, reliable power also during periods with low renewable generation and offer the advantage of being able to run on different fuels, from natural gas and liquid fuels or biofuels today, to locally produced hydrogen and its derivatives tomorrow as they become competitive and broadly available.

Thanks to this multi-fuel capability, not only do engine power plants provide a great hedge against fuel supply risk, but they are also the ultimate “future-proof” technology for decarbonisation. Gas engines can already run with 25% hydrogen blend without major modifications. We anticipate that a few years from now engines will be capable to run entirely on green fuels like hydrogen to reach 100% renewables and net-zero.

An intelligent energy management system (EMS) enables seamless operation of any mix of power assets. Wärtsilä’s state-of-the-art GEMS Digital Energy Platform utilises real-time data, renewable forecasts as well as machine learning algorithms, to optimise the dispatch of dynamic generation assets with speed, instead of applying a rigid rule-based model. GEMS’ optimisation and control capabilities enable reliability, minimised emissions, and reduced costs.

Decarbonisation is a journey, not a destination
For companies to remain competitive, their decarbonisation process must be based upon three pillars : emission reduction, competitive cost, and reliability. To get this done, the journey to net-zero for mining and industrial businesses in Africa cannot rely on a single solution. It is a long-term, future-proof plan that involves a data-driven management of energy assets.

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