How to choose a Wilden pneumatic diaphragm pump? Step by step, based on the intended use case.

Anyone who has experienced the pitfalls of buying a  Wilden pump knows that it is not enough to just look at the diameter 

and flow rate when selecting a pump. What is your medium, what is the temperature, whether there are particles, and whether 

electricity can be used on-site—these are the real keys to deciding which series and material to choose.

Let’s talk based on actual usage scenarios. Whether you are engaged in chemical industry, food or mining, you can find 

corresponding selection ideas.

First understand the medium, this is the first step in selection.

When you get a selection requirement, the first thing you should ask is not "how big is the flow rate", but "what are you pumping?"

Once the medium is determined, the materials of the pump body and diaphragm are basically determined. Wilden's pump bodies are

 commonly made of aluminum alloy, cast iron, 316 stainless steel, polypropylene (PP), and polyvinylidene fluoride (PVDF). Diaphragm

 materials mainly include nitrile rubber (Buna-N), neoprene, EPDM, fluororubber (FKM), Wil-Flex™ and Teflon (PTFE).

Don't underestimate this step. It is also a 1-inch pump with a PVDF pump body and a PTFE diaphragm that can pump concentrated 

sulfuric acid. If it is replaced with an aluminum alloy pump body and a nitrile rubber diaphragm, it will be scrapped in a few days.

Temperature should also be considered together. Many people only look at the chemical properties of the medium and forget that

 temperature will limit the material. For example, fluororubber (FKM) can withstand 176°C, but if you choose a polypropylene (PP) 

pump body, its upper limit is only 79°C. The temperature limits of the pump body and diaphragm must be met at the same time, 

whichever is lower.

Choose according to the scene and take your seat accordingly

Pumping acids, bases and corrosive chemicals

This is one of the most common applications for  Wilden pumps. The selection idea is very clear: PVDF or PP plastic pumps are preferred 

for pump bodies, and 316 stainless steel or Hastelloy is preferred for highly corrosive conditions. The preferred diaphragm is PTFE (Teflon),

 which is resistant to strong acids, alkalis and organic solvents.

There is a detail that is easy to overlook: if you are pumping oxidizing media such as sodium hypochlorite, nitrile rubber (NBR) and 

polyurethane (PU) diaphragms are prohibited. PTFE or Wil-Flex™ is the right choice. Wil-Flex™ is cost-effective in terms of acid and 

alkali resistance, and its wear resistance is better than ordinary neoprene, making it suitable for working conditions with both corrosion 

and wear.

Pumping mud and sewage containing particles

In scenes such as mining, ceramics, and sewage treatment, it is normal to have particles in the medium.

The Wil-Flex™ diaphragm is more stable, has outstanding wear resistance, and has a much longer life than nitrile rubber diaphragms. 

If the particles have high hardness and sharp edges, you can consider a thickened diaphragm or ceramic ball seat to extend the service 

life.

There is a hard limit on particle size: usually no more than 50% of the pump outlet diameter. Before selecting a model, first confirm 

the millimeters of the largest particles in your media. This data is very critical. The particle diameters that different  Wilden models can 

pass vary greatly, ranging from 1.6mm to 25mm.

Pumping high viscosity media

For high-viscosity fluids such as grease, glue, and mud, the logic of pump selection is completely different from that for clean water.

There are two core ideas: one is to choose a large diameter pump body to reduce flow channel resistance; the other is to compensate

 for the flow loss caused by viscosity by increasing the air source pressure. Wilden pneumatic diaphragm pumps can handle liquids with

 viscosity below 20,000 cP.

There are also particularities in installation. The diameter of the suction pipeline is preferably one size larger than the pump inlet. The 

pump should be located as close to the liquid surface as possible or placed below the liquid surface, so that the suction distance is short

 and the pump is easy to pump.

Oil extraction and petroleum products

The selection in this scenario is the simplest: choose nitrile rubber (Buna-N) for the diaphragm, which is the standard choice for 

transporting gasoline, diesel, hydraulic oil, and engine oil.

As for the pump body, aluminum alloy can be used in mildly corrosive oily media, while cast iron pumps are suitable for papermaking,

 chemical industry, mining and other scenarios, and have strong wear resistance. But if the oil contains aromatic hydrocarbons or

 chlorinated hydrocarbons, aluminum alloy will not work and stainless steel will have to be replaced.

Food, pharmaceutical and hygienic applications

In this type of scenario,  Wilden’s PS series (Saniflo™ HS) must be used, not just any stainless steel pump.

The design of the PS series has several key points: self-draining flow channels, support for cleaning in place (CIP), and the pump body

 is made of polished stainless steel or PVDF, which meets certification requirements such as 3A, FDA CFR 21.177, and USP Class VI. 

Simply put, its flow channel has no dead ends, the cleaning fluid can be flushed clean, and there will be no residual materials causing 

cross-contamination.

If you are doing pasteurized products, protein-based products or biopharmaceutical aseptic processes, the PS series is a must. Even 

if ordinary industrial pumps are made of stainless steel, the flow channel design and surface finish cannot meet hygienic standards.

Flammable and explosive environment

In mines, chemical workshops, and oil and gas sites, explosion-proof requirements are strict.

The advantage of Wilden pneumatic diaphragm pump itself is here: it is powered by compressed air, does not generate sparks, and 

does not generate heat during operation. But if you need formal certification to satisfy safety audits, choose an ATEX-certified model. 

Wilden's Advanced series and X series metal pumps and plastic pumps have passed ATEX 94/9/EC certification.

If it is a coal mine environment, look directly at the BQG series. This is a mining pump specially developed by  Wilden for the Chinese 

market. It has a mining product safety mark certificate, can convey mud with particles, and is allowed to run dry. It is applicable to

 scenarios such as underground drainage, gas environment, and wastewater around equipment.

Air source and installation, don’t ignore the aspects

After selecting the pump body and diaphragm, there are two things to confirm.

Air source conditions. The working pressure range of Wilden pneumatic diaphragm pump is usually 0.7~8.6bar, the pressure ratio is 

generally 1:1-6bar air source inlet, and the outlet pressure is also about 6bar. If you need higher outlet pressure to overcome pipeline

 resistance, either increase the air source pressure (not exceeding 8.6bar) or choose a high-pressure pump. Air consumption is directly 

related to the size and flow rate of the pump. Large pumps require larger air compressors, which must be taken into account when 

selecting.

Self-priming height. Under standard circumstances, the dry suction height of the Wilden pump is about 4 to 6 meters, and the wet 

suction height can be 7 to 8.6 meters. If your installation location is far away from the liquid level, or the viscosity of the medium is 

high, the self-priming ability will be compromised. At this time, you should consider lowering the pump or shortening the suction stroke.

Finally, a few honest words

Wilden has indeed many product lines. The Advanced™ series is highly versatile and covers most common working conditions; the 

Pro-Flo® SHIFT series is suitable for continuously operating production lines, saving gas and electricity; the metal series can withstand

 high temperatures and high pressures; the PS series pipes are sanitary grade; and the BQG pipes are used in mining.

When selecting a model, don’t pursue “the most expensive and the best”. Choose based on your actual working conditions. 

Prepare the information such as medium name, concentration, temperature, particle condition, required flow rate and on-site air 

source conditions, and the selection will be more than half faster.

There is another pitfall that is easy to step on: the diaphragm is a consumable, and no matter which material you choose, it has a

 life limit. It is more practical to check the condition of the diaphragm regularly than to worry about which material to choose. 

 Wilden's clamp design is easy to disassemble and assemble, so daily maintenance does not require a lot of effort.

If you have specific working condition parameters on hand, you can first narrow down the range by comparing the above scenarios, 

and then check the performance curves of the corresponding series, and you can basically make a decision.