Front view of a stainless steel industrial double diaphragm pump with red caps on a white background.

3D render of a silver and black industrial double diaphragm pump with red caps on a white background.

Stainless steel industrial diaphragm pump with black center section and red ports on white background

3D render of a stainless steel double diaphragm pump with a cutaway view showing internal components

DP3X Series

1-1/2 Inch Stainless Steel Air Operated Double Diaphragm Pump

The DP31-40 is the 1-1/2 inch stainless steel pump in the DP3X series, designed for applications where corrosion resistance and mechanical strength matter. It delivers up to 90 GPM, which is 340.7 LPM, at 120 psi or 8.3 bar, passes suspended solids to 6.4 mm, and lifts 5.8 m dry. The 316 stainless steel body resists rust and chemical attack, making it suitable for aggressive liquids like acids, alkalis, and solvents. The stall free air motor ensures consistent operation under load, and the lube free system means no oil mist and no maintenance on the air line.

Maximum flow rate	90 GPM (340.7 LPM)
Maximum operating pressure	120 psi (8.3 bar)
Suspended solids max diameter	1/4" (6.4mm)
Fluid inlet	Rp 1-1/2 (1-1/2 BSP, parallel), 1-1/2 NPT
Fluid outlet	Rp 1-1/2 (1-1/2 BSP, parallel), 1-1/2 NPT

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Key Benefits

What The 1-1/2 Inch Stainless Steel Build Buys You

Corrosion resistance, durability and consistent performance come from the stainless body and the patented air end design.

Built To Resist Chemical Attack

Aluminum or cast iron versions would corrode in these fluids, so this pump is the only viable option for long term duty.

Stall Free Operation Under Load

The pilot air valve gives the major air valve a fast, positive shift signal, so the pump does not hang at mid stroke when starting under load or during a cycle change.

No Oil On The Air Line

The self lubricating air system requires no external oiler, so there is no oil mist in the exhaust and no need to refill a lubricator during maintenance rounds.

Dual Ceramic Dynamic Seals

Both the major air valve and the pilot air valve use ceramic dynamic seals, which resist wear from dirt in the air supply and extend the life of the air end.

Quiet Operation With Less Air Use

The built in vacuum chamber reduces discharge air pressure, which lowers both the cooling effect that causes icing and the exhaust noise, while also reducing air consumption.

Drop In Replacement For Other Brands

Installation dimensions, port positions and foot spacing match other major AODD brands, so the base, piping and air line usually stay unchanged during replacement.

Who It Is For

Who Buys This Pump

This pump is chosen when the fluid is corrosive, the duty is continuous, or the environment demands stainless steel for hygiene or durability.

Chemical plants transferring acids, alkalis, and solvents between storage tanks and process lines
Pharmaceutical and biotech facilities handling sterile or reactive liquids where contamination and corrosion must be avoided
Food and beverage plants processing acidic condiments or cleaning fluids where stainless steel is required
Surface preparation and electroplating shops moving quenching oil, electroplate liquid and rinse water
Waste water treatment plants handling aggressive sludge and chemical dosing streams
OEMs integrating a reliable, durable pump into skid-mounted systems or filtration carts

Problems It Solves

Problems This Pump Is Bought To Fix

Most inquiries for this model come from plants that have already experienced failure with a less robust pump.

A pump made of aluminum or cast iron corroded in acid or alkali, leading to leaks and downtime.
A pump stalled at mid stroke during start-up, causing delays and inconsistent flow.
An oil-lubricated air end created oil mist in the room, which contaminated the product or triggered safety alarms.
A pump failed after a few months due to wear on the air valve seals from dirty air supply.
A pump could not be installed in the same space because the footprint did not match the old unit.

Application Scenarios

Where It Ends Up In A Plant

01

Chemical Transfer And Blending

The pump moves acids and solvents between tanks at 340.7 LPM with no risk of metal contamination or corrosion.

02

Pharmaceutical Formulation

It transfers shear-sensitive liquids without introducing particles or wear debris, thanks to the ceramic seals and stainless body.

03

Tank Farm And Bulk Tank Transfer

It handles aggressive liquids over long distances with a 5.8 m dry suction lift, eliminating the need for a foot valve.

04

System Flush And Recirculation

It can be dead headed against a closed valve during cleaning cycles without damage, and restarts cleanly when the valve opens.

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 compressed air, then it triggers the major valve. This two-stage signal ensures a fast, positive shift and prevents stall-out.
Dual Ceramic Dynamic Seals
Both the major air valve and the pilot air valve use ceramic dynamic seals. These resist wear from dirt and maintain tight sealing over long life.
Self Lubricating Lube Free Air System
No lubricator is fitted to the air inlet and none is needed. This removes a maintenance task and eliminates oil mist in the exhaust.
Anti Icing Vacuum Chamber
The built in vacuum chamber reduces discharge air pressure, which cuts expansion cooling and noise, and lowers air consumption.
Interchangeable Installation Envelope
Port positions, foot spacing and overall envelope match other major brands, so this pump can be installed without changing pipework or base.
Selectable Wetted Materials
Center body, fluid caps, 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	90 GPM (340.7 LPM)
Maximum operating pressure	120 psi (8.3 bar)
Suspended solids max diameter	1/4" (6.4mm)
Fluid inlet	Rp 1-1/2 (1-1/2 BSP, parallel), 1-1/2 NPT
Fluid outlet	Rp 1-1/2 (1-1/2 BSP, parallel), 1-1/2 NPT
Air inlet	3/8" BSPT (3/8" NPT Available On Request), female
Maximum dry suction lift	19 feet (5.8m)
Sound level	80.5 db(A) at 70 psi, 60 cycles/min.
Weight	84.5 lbs (38.3kg)
Model series code	DP31-40, DP31-Air40, DP31-Flu40-XX

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	1-Neoprene, 2-Nitrile, 3-Viton, 4-PTFE/Santoprene, 5-E.P.R, 6-Acetal, 9-Hytrel, B-Santoprene, G-Nitrile
Ball check options	1-Neoprene, 2-Nitrile, 3-Viton, 4-PTFE, 5-E.P.R, 6-Acetal, 8-Polyurethane, A-Stainless Steel, C-Hytrel, E-Santoprene
Seat options	1-Aluminum, 2-316 Stainless Steel, 3-Polypropylene, 4-PVDF(Kynar), 5-Carbon Steel, 8-Hard 400 Stainless Steel
Housing options	A-Aluminum (Center Body), C-Cast Iron (Center Body), S-Stainless Steel (Fluid Caps Manifold), C-Cast Iron (Fluid Caps Manifold)

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 3/8 inch BSPT, on request

Comparison

Against The Alternatives

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

Versus the 1-1/2 inch aluminum version	Same 340.7 LPM and same 8.3 bar, but 38.3 kg against 23.4 kg. Choose aluminum when weight and portability matter and the fluid does not attack metal.
Versus the 1-1/2 inch cast iron version	Cast iron at 36.1 kg is the choice for abrasive slurry duty where wall wear matters. Stainless steel is the choice when corrosion resistance and hygiene are required.
Versus the 1-1/2 inch non-metallic version	The polypropylene pump handles acids and alkalis that would eat aluminum, at a lower 378.5 LPM. Pick non metallic on chemistry, not on flow.
Versus the 1 inch stainless steel version	The 1 inch version delivers only 133 LPM, which is not enough for high volume transfer. Step up to 1-1/2 inch when flow exceeds 133 LPM.
Versus the 2 inch aluminum version	The 2 inch reaches 651 LPM and passes 9.5 mm solids, but weighs 29.6 kg and needs more air. Step up only when 340.7 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.

Use Guide

Getting The Best Out Of It

Five things that decide whether this pump does 340.7 LPM or half of it.

Give It Real Air
Flow follows air. Use the full 3/8 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 5.8 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-Air40, and one fluid section kit, DP31-Flu40-XX, 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: product data sheets, series catalogues.

PDF 1.5 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

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

Answers

1-1/2 Inch Stainless Steel Air Operated Double Diaphragm Pump FAQ

What flow will this pump actually give me?

90 GPM, which is 340.7 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?

1/4 inch, which is 6.4 mm, on the suspended solids figure from the data sheet. If your fluid carries bigger solids, look at the 3 inch models at 9.5 mm or the heavy duty flap valve pump at 50 mm.

Will it replace another brand of 1-1/2 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 1-1/2 (1-1/2 BSP, parallel) or 1-1/2 NPT. The air inlet is 3/8 inch BSPT female, with 3/8 inch NPT available on request.