Diaphragm Pump NDP Series pumps are the backbone of the industrial line of AODD pumps. A unique, patented air-valve design ensures stall-free operation throughout product life. Bolted construction and common component replaceable parts maximize uptime and increase profitability. If you require specialty pumps, please click here to see our High Pressure, UL, CSA, Powder and FDA diaphragm pumps.
What is a Double Diaphragm Pump How it works in an industrial application?
It is a 1:1 positive displacement pump technology using compressed air to transfer a known volume of liquid from point A to point B. Due to the variety of materials available and their inherent operating characteristics, there aren’t many liquids that can’t be pumped with an air operated double diaphragm pump. If there is a high solids content, higher viscosities present, wide ranges of pH, possible dry running conditions, variable flow rates, suction lift required or if you just want something portable this pump technology is an excellent choice. Provided the flow rates are between .5 - 250 GPM and one has compressed air available, this is an inherently or explosion proof way to transfer almost any liquid.
What is a double diaphragm pump and how does it work? Explained
An air operated double diaphragm pump is a pneumatic pump that uses a patented air valve that directs compressed air between two sides of the pump, back and forth. It can operate on regular compressed air, clean dry air, nitrogen, or even natural gas. This air valve switching pushes compressed air behind a diaphragm and that directly applies the force to the liquid in the chamber forcing it up and out of the pump. That same force pushing one diaphragm out is drawing the other diaphragm in, as they are attached to a common center shaft, and that creates a vacuum in the opposite liquid chamber.
While one side is evacuating liquid, the other side is filling up and this process goes back and forth to create the actual liquid transfer and subsequent flow rate necessary. There are typically four ball check valves inside a standard type of pump only allowing the liquid to travel from the bottom suction manifold out through the top discharge manifold. You can run this technology anywhere from a few psi or air pressure all the way up to 125psi of pressure depending on flow rate and discharge pressure required.
While the NDP pump line up is the most common and is considered the industry standard, sometimes there are more exotic applications that these can be used on as well. Things like ultra-high purity chemicals, pharmaceuticals, alcoholic beverages, food products, higher viscosities, or solids contents (up to 40% by weight) are also possible with this technology. Simple modifications can be made to most sizes allowing for customization for each application. Pneumatic pumps are often used when transferring highly explosive liquids as they are easily grounded and are inherently safer being operated with compressed air.
How does a double diaphragm pump work?
Note there are two diaphragms and four check balls in most standard pumps. The diaphragms are used to draw the liquid into and push it out of the pump depending on which direction it is traveling. In standard pumps, the check balls are designed to only allow the liquid to travel through the bottom of the pump and then out the top when operating.
When the compressed air pushes one of the diaphragms out towards the liquid chamber, forcing the bottom check valve down and the top check valve up, it directly applies whatever air pressure you gave the pump onto the liquid forcing it up and out of the pump. At the same time, the other diaphragm is being drawn in creating a vacuum in the opposite pumping chamber and drawing the bottom check ball up and the top check valve down. Then the air will switch and start the cycle in the other direction, always evacuating one chamber while filling the other creating the full pump cycle.
They have an infinitely variable flow rate depending on how much air volume and pressure you give the pump. The higher the flow rate, the longer the discharge piping or thicker the fluid, the more pressure and volume you give the pump. There are standard side ported, center ported and split manifold pumps as well as UL, CSA, ATEX and FDA compliant pumps available.
When should you specify a pneumatic double diaphragm pump?
An air operated double diaphragm pump is typically used where air is readily available, and the characteristics of the application are better suited for the technology. If you have solids, a thicker liquid, self-priming requirements, dry running potential, explosion proof specs, variable flow rates, shear sensitive liquids, something submerged, portability required, or the application calls for dead heading a diaphragm pump is an excellent choice. Things like sumps, tanker unloading, and simple water or chemical transfer applications are the most common and basic. There are process or more challenging applications for the technology also in industries like carpet manufacturing, paint plants, pharmaceutical facilities, semiconductor fabs, the printing industry and powder transfer. Each application will have their own requirements and the pumps can be modified accordingly to achieve the flow rates required while also maintaining long pump lives.
There is the standard NDP pump line up and a list of customizations that can be made in addition to specialty pumps design for specific applications or industries. A couple of examples of that are electropolished or solid PTFE pumps for the semiconductor industry along with mechanically actuated XDP valve designed pumps for filter presses or even 2:1 high pressure designs and even powder transfer set ups. Certain industries may also require regulator agency qualifications like UL, CSA, FDA or ATEX which are also all available.
Double Diaphragm Pump Body Material Types
Double diaphragm pumps can be ordered in the following materials: Polypropylene (PPG), Kynar® (PVDF), Groundable Acetal, Aluminum (ADC-12) and Stainless Steel (316) and Cast Iron.
Double Diaphragm Pump Seal and check ball Material Types
Buna N 180°F (82°C), Neoprene 180°F (82°C), Santoprene®(TPO) 180°F (82°C), EPDM 212°F (100°C), PTFE 212°F (100°C), Hytrel® (TPE) 248°F (120°C), Viton® fluoroelastomer 248°F (120°C). Please note that Polypropylene and acetal pumps have a maximum liquid temperature of 180°F (82°C) regardless of diaphragm material.
Double Diaphragm Pump Common Fluids
There are many industrial paints, polymers, hardeners, varnishes, lacquers, greases, adhesives, latex, acids plus bases and titanium Dioxide or fumed silica powders that require mixing and blending at various temperatures and flow rates. Some of the most common acids pumped are Hydrofluoric, Sulfuric and Nitric. Some of the most common finished products pumped are wines, paints and various adhesives or coatings. A double diaphragm pump can continuously transfer single or plural components through the up and down stream avenues of a fluid handling system.
Double Diaphragm Pump Common Applications
Filter Presses, adhesives, paints, chemical additive, winery pump over transfers, general wastewater transfer, drum pumps, tanker unloading, spraying, dosing, pigments, colorants, flavorings, filling machines and mixing tanks all use diaphragm pumps to manage their fluid handling systems.
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