Silver metallic double diaphragm pump with green gaskets and a red center cap.

Stainless steel double diaphragm pump with green rings and red caps on a white background

Front view of a silver metallic industrial pump with a gold cylinder component.

DP3X Series

3 Inch Stainless Steel Air Operated Double Diaphragm Pump

The DP31-80 is the three inch stainless steel pump in the DP3X series. It delivers 237 GPM, which is 897 LPM, at up to 120 psi or 8.3 bar, with a dry suction lift of 5.4 m. It passes suspended solids up to 9.5 mm and is built for continuous duty with aggressive fluids. The 316 stainless steel body resists corrosion from acids, alkalis, and chlorides. The stall free air motor ensures reliable start-up under load and smooth operation without mid-stroke hang-up. The pump is designed to fit into existing installations without modification.

Maximum flow rate	237 GPM (897 LPM)
Maximum operating pressure	120psi (8.3 bar)
Suspended solids max diameter	3/8" (9.5mm)
Fluid inlet	Rp 3 (3" BSP, parallel) / 3" NPT
Fluid outlet	Rp 3 (3" BSP, parallel) / 3" NPT

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Key Benefits

What The Three Inch Stainless Build Buys You

Volume, corrosion resistance and reliability come together in this model, but at the cost of weight and price.

The Highest Flow In The Stainless Range

At 897 LPM, it moves more fluid than any other stainless steel AODD in the DP3X series. It is the only 3 inch stainless model, so it is the only choice for high volume transfer where corrosion resistance matters.

Corrosion Resistant For Harsh Fluids

The 316 stainless steel body resists attack from acids, alkalis, chlorides and many solvents. It is suitable for use with electroplate liquids, quenching oils and liquid waste that would degrade aluminum or cast iron.

Stall Free Operation Every Time

The pilot air valve gives a fast, positive shift signal to the major air valve. The pump trips over cleanly and does not stall at mid stroke, even under heavy load or with variable air supply.

No Maintenance On The Air System

The air distribution system is self lubricating and does not require an external oiler. There is no oil mist in the exhaust and no need to refill a lubricator during routine checks.

Anti Icing By Design

A built in vacuum chamber reduces discharge air pressure, which lowers the cooling effect that causes icing and reduces exhaust noise. The published sound level is 80.5 dB(A) at 70 psi and 60 cycles per minute.

It Fits Where Your Old Pump Sits

Installation dimensions and footprint are compatible with other major AODD brands. The base, pipe spools and air line usually stay unchanged during a swap.

Who It Is For

Who Buys This Pump

Three inch stainless steel is the choice when you need high volume transfer with a fluid that attacks aluminum or cast iron. It is not for every job, but it is the only option when corrosion and flow are both critical.

Chemical plants transferring acids, alkalis, and caustic solutions between tanks and reactors
Pharmaceutical and biotech facilities moving shear sensitive liquids and sterile formulations
Food and beverage plants handling condiments, syrups, and additives where hygiene and corrosion resistance matter
Waste water treatment plants pumping liquid waste and sludge with high chloride content
Surface preparation shops moving electroplate liquids and rinse water
OEMs building skid mounted systems that must handle aggressive fluids and high flow

Problems It Solves

Problems This Pump Is Bought To Fix

Almost every enquiry for this model starts with a pump that failed at one of these five things.

A centrifugal pump loses prime as the tank runs down, while this pump self primes and can be run dry without damage
Line blockages deadhead the pump, and an AODD simply stops against the closed valve and starts again when the valve opens
Chlorides and acids attack aluminum and cast iron, but 316 stainless steel resists them
A smaller pump cannot move the volume needed, and a 3 inch model is the only way to get 897 LPM
A lighter pump is not strong enough for the duty, and the 100.79 kg body handles the stress of high pressure and high flow

Application Scenarios

Where It Ends Up In A Plant

01

Bulk Tank And Tank Farm Transfer

Self priming with 5.4 m of dry suction lift, so it transfers from a bulk tank or a tank farm without a foot valve.

02

Chemical Processing And Formulation

Air throttling gives smooth flow control from a trickle to 897 LPM, which suits dosing into a reactor or blending a batch.

03

Waste Water Treatment And Filtration Feed

The pump can be dead headed as the filter cake builds and the pressure rises, then restart when the filter is cleaned.

04

System Flush And Recirculation

One person can run it dry for hours during a system flush without damaging the diaphragms or seals.

Technical Features

How The Air End Is Built

The hydraulic end of an AODD pump is simple. The air end is where pumps differ, and where Nuodean holds its patents.

Major Air Valve Plus Pilot Air Valve
The pilot valve is shifted mechanically by the actuator pin and pneumatically by the compressed air, then it shifts the major valve. That two stage signal is what makes the changeover positive and fast.
Dual Ceramic Dynamic Seals
Both the major air valve and the pilot air valve run ceramic dynamic seals. They resist wear, tolerate a dirty air supply and keep discharge contamination down over a long life.
Self Lubricating Lube Free Air System
No lubricator is fitted to the air inlet and none is needed, which removes both a maintenance task and the oil mist that a lubricated pump puts into the room.
Anti Icing Vacuum Chamber
The built in vacuum chamber reduces discharge air pressure, which lowers the expansion cooling that ices an air motor and drops the exhaust noise at the same time.
Interchangeable Installation Envelope
Port positions, foot spacing and overall envelope follow the major brands, so this pump can be dropped into an existing installation.
Selectable Wetted Materials
Center body, fluid caps and manifold, seat, ball check, diaphragm, connection thread and hardware are each chosen in the model code rather than fixed at the factory.

Specifications

Published Performance

Transcribed from the Nuodean data sheet published for this pump.

Maximum flow rate	237 GPM (897 LPM)
Maximum operating pressure	120psi (8.3 bar)
Suspended solids max diameter	3/8" (9.5mm)
Fluid inlet	Rp 3 (3" BSP, parallel) / 3" NPT
Fluid outlet	Rp 3 (3" BSP, parallel) / 3" NPT
Air inlet	3/4" BSPT female (3/4" NPT available on request)
Maximum dry suction lift	17.6 feet (5.4m)
Weight	222.2 lbs (100.79kg)
Model series code	DP31, DP31-Air80, DP31-Flu80

Materials

Material Options

Set in the model code. Ask us if you need a combination the code allows but the sheet does not show.

Wetted body material	316 stainless steel
Diaphragm options	2-Nitrile, 4-PTFE/Santoprene, 9-Hytrel, B-Santoprene
Ball check options	2-Nitrile, C-Hytrel, 4-PTFE, E-Santoprene
Seat options	1-Aluminum, 2-316 Stainless Steel, 4-PVDF

Performance figures are transcribed from the Nuodean data sheet for this pump. Flow is measured at the pump discharge with water at ambient temperature; your duty point depends on air supply pressure, suction conditions, fluid viscosity and discharge head. Ask our engineers to confirm the duty point before you order.

Quality Control

Before It Is Crated

Every pump is run on air before it leaves, so the shift behaviour is checked rather than assumed
Sound level is published for the model at 70 psi and 60 cycles per minute so you can hold us to it
Ball, seat and diaphragm materials are checked against the ordered model code at assembly
The pump ships with the data sheet and both the fluid section and air section part lists

Customization

What You Can Change

Center body in aluminum or cast iron
Fluid caps and manifold in aluminum, 316 stainless steel or cast iron
Seat in aluminum, 316 stainless steel, PVDF, carbon steel, hard stainless steel, Santoprene, Hytrel or nitrile
Ball check in neoprene, nitrile, Viton, PTFE, EPDM, acetal, polyurethane, stainless steel, Hytrel or Santoprene
Diaphragm in neoprene, nitrile, Viton, PTFE with Santoprene backing, EPDM, acetal, Hytrel or Santoprene
NPT or BSP threaded fluid connections, stainless steel or carbon steel hardware
3/4 inch NPT air inlet in place of the standard 3/4 inch BSPT, on request

Comparison

Against The Alternatives

Where this pump wins and where you should be buying something else.

Versus the 3 inch aluminum pump	The aluminum version is lighter at 49.8 kg and cheaper, but it cannot handle acids, alkalis or chlorides. Use stainless when the fluid attacks aluminum.
Versus the 3 inch cast iron pump	Cast iron at 63.5 kg is the choice for abrasive slurry duty where wall wear matters. Stainless steel is the choice when corrosion resistance matters more than abrasion resistance.
Versus the 2 inch stainless steel pump	The 2 inch moves 340.7 LPM and weighs 38.3 kg. Use the 3 inch only when 897 LPM is genuinely needed and the 2 inch is not enough.
Versus the 3 inch non-metallic pump	The non-metallic pump handles acids and alkalis that would attack stainless steel, but it only moves 177.9 LPM. Pick non-metallic on chemistry, not on flow.
Versus the 3 inch flap valve pump	The flap valve model passes solids up to 50 mm, but it is not suitable for high pressure or high flow duty. Use the DP31-80 for volume and pressure, not for large solids.
Versus a centrifugal pump	The centrifugal is cheaper to run at a fixed high flow with clean fluid. This pump wins when the tank runs dry, the line blocks, the fluid carries solids or the area cannot take a motor.

Use Guide

Getting The Best Out Of It

Five things that decide whether this pump does 897 LPM or half of it.

Give It Real Air
Flow follows air. Use the full 3/4 inch inlet, keep the hose short and confirm the compressor can hold pressure at the flow the pump asks for.
Do Not Throttle The Suction
Throttle the discharge or the air, never the suction. Starving the suction is what causes cavitation, hard running and short diaphragm life.
Match The Elastomer To The Fluid
Diaphragm and ball material is chosen in the model code. Get the chemistry right and the pump lasts. Get it wrong and nothing else you do will save it.
Keep Suction Lift Honest
The published 5.4 m is a dry lift figure on the data sheet. Priming a flooded suction is always easier, so put the pump below the tank where the layout allows.
Stock The Two Repair Kits
One air section kit, DP31-Air80, and one fluid section kit, DP31-Flu80, coded for your diaphragm and ball material. Between them they cover almost every wear part.

Documents

Documents For This Pump

Straight from Nuodean's own literature: fluid and air section drawings, product data sheets, series catalogues.

PDF 3 inch metallic AODD pumps data sheet Product Data Sheets PDF 1.2 MB Download PDF DP3X AODD PUMPS Catalogue Series Catalogues PDF 18.1 MB Download PDF Fluid Section of 3 inch DP11 Metallic Pump Fluid And Air Section Drawings PDF 148 KB Download PDF Air Section of 3 inch DP11 Metallic Pump Fluid And Air Section Drawings PDF 199 KB Download

Need a 2D or 3D CAD model of this pump? CAD on request via WhatsApp.

Answers

3 Inch Stainless Steel Air Operated Double Diaphragm Pump FAQ

What flow will this pump actually give me?

237 GPM, which is 897 LPM, is the maximum with a free discharge and full air supply. Real duty points are lower. Send us the discharge head and the air pressure you can hold and we will tell you where on the curve you land.

Can it run dry?

Yes. An air operated double diaphragm pump can be run dry and can be dead headed against a closed valve without damage. That is the main reason plants choose one over a centrifugal pump.

What is the largest solid it will pass?

3/8 inch, which is 9.5 mm, on the suspended solids figure from the data sheet. If your fluid carries bigger solids, look at the 3 inch flap valve pump at 50 mm.

Will it replace another brand of three inch AODD pump?

Usually yes. The DP3X pumps are built so that installation dimensions and footprint are compatible with other brands. Send a photo of the nameplate and the pipework and we will confirm before you buy.

Which diaphragm should I order?

PTFE with a Santoprene backing for aggressive solvents and acids, Santoprene for general duty and long flex life, Viton for hot oils and aromatics, nitrile for petroleum products. Tell us the fluid and the temperature and we will put the right code on the quotation.

How loud is it?

80.5 dB(A) at 70 psi and 60 cycles per minute, as printed on the data sheet. Slower cycling is quieter, and a piped exhaust takes more off.

What connections does it come with?

Fluid inlet and outlet are Rp 3, which is 3 inch parallel BSP, or 3 inch NPT. The air inlet is 3/4 inch BSPT female, with 3/4 inch NPT available on request.