A black industrial diaphragm pump with green accents and a red port cover on a white background.

Industrial double diaphragm pump with black housing and red port caps on a white background

DP3X Series

3 Inch Cast Iron Air Operated Double Diaphragm Pump

The DP31-80 is the three inch cast iron pump in the DP3X series, and it is the model chosen when a plant needs high volume transfer of abrasive or heavy fluids with a durable, long-life air end. It moves up to 237 GPM, which is 897 LPM, at up to 120 psi or 8.3 bar, passes suspended solids to 9.5 mm and lifts 5.4 m dry. The cast iron center body and fluid caps make it resistant to wear from abrasive slurries and heavy solids, and the stall free air motor means it starts under load every time instead of hanging at mid stroke.

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 Cast Iron Build Buys You

Durability, volume and resistance to wear sit differently on this model than on the aluminum or stainless version of the same hydraulic end.

The Most Durable Three Inch In The Range

At 96.7 kg, it is heavier than the aluminum version at 49.8 kg, but the cast iron body resists wall wear from abrasive slurries and solids that would erode aluminum over time.

897 LPM From An Air Line Alone

All the pump needs is a 3/4 inch air line. No motor, no starter, no VFD, no earthing and no electrical area classification paperwork.

It Will Not Stall At The End Of A Stroke

A pilot air valve gives the major air valve a positive, fast shift signal. The pump trips over cleanly instead of sitting at mid stroke waiting for someone to tap the air end.

No Oiler On The Air Line

The air distribution system is self lubricating and lube free, so there is no oil mist in the exhaust and nothing to top up on a maintenance round.

Anti Icing By Design

A built in vacuum chamber lowers discharge air pressure, which cuts both the temperature drop that causes icing and the exhaust noise. The published sound level is 86.5 dB(A) at 70 psi and 60 cycles per minute.

It Fits Where Your Old Pump Sits

Installation dimensions and footprint are compatible with the major AODD brands, so the base, the pipe spools and the air line usually stay exactly as they are.

Who It Is For

Who Buys This Pump

Three inch cast iron is the heavy duty choice. It goes in when the fluid is abrasive, the solids are large, and the plant wants long life from a pump that can handle continuous duty.

Mining and quarrying plants transferring slurry, tailings and mineral concentrates with high solids content
Foundries and metal casting facilities moving sand, grit and metal fines in coolant and wash water
Waste treatment plants handling sludge, grit and solids-laden wastewater
Chemical plants moving abrasive resins, catalysts and reaction byproducts
Manufacturers of abrasives, ceramics and refractories transferring dry or semi-dry materials in liquid suspension
Plants replacing a competitor three inch AODD pump and unwilling to change the pipework

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 soon 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
Abrasive slurries and grit wear out close clearance pumps, while the cast iron body and 9.5 mm solids pass capability resist that wear
Electric pumps bring an area classification argument to a dusty or wet environment, and air drive avoids that argument entirely
A lighter pump at 49.8 kg cannot withstand the mechanical stress of high solids and high flow, and 96.7 kg can

Application Scenarios

Where It Ends Up In A Plant

01

Slurry And Grit Transfer

Self priming with 5.4 m of dry suction lift, so it moves abrasive slurries from sumps, tanks and hoppers without a foot valve.

02

Tanker And Drum Unloading

The 897 LPM capacity handles large volumes of liquid with solids, and the cast iron body resists wear from repeated transfer duty.

03

Filter Press And Filtration Feed

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

04

Sump And Pit Emptying

One person carries it to the pit, drops the suction hose in and runs it dry at the end without burning anything out.

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	213.1 lbs (96.7kg)
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	Cast iron
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 version	Same 897 LPM and same 8.3 bar, but 96.7 kg against 49.8 kg and higher resistance to wall wear. Choose aluminum when the fluid is non-abrasive and portability matters.
Versus the 3 inch stainless steel version	Stainless steel at 84.5 kg is the choice for corrosion resistance in aggressive chemicals. Cast iron at 96.7 kg is the choice for abrasive duty where wall thickness and wear resistance matter.
Versus the 3 inch non metallic version	The polypropylene pump handles acids and alkalis that would eat cast iron, at a lower 210 GPM. Pick non metallic on chemistry, not on flow.
Versus the 2 inch cast iron version	The 2 inch reaches 90 GPM and passes 9.5 mm solids, but weighs 79.5 kg and needs more air. Step up only when 897 LPM is genuinely not enough.
Versus a centrifugal transfer 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.
Versus the 3 inch flap valve pump	The flap valve pump passes 50 mm solids and is better for very large or irregular solids. This pump gives more flow and better pressure control for continuous transfer.

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 Cast Iron 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?

86.5 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.