A Peristaltic Pump is a positive displacement pump, meaning pump pressure does not overly affect the volume pumped.
The basic principle of the peristaltic pump traces back to human “peristalsis”. A term referring to the alternating contraction and relaxation of muscles around a tube to force the contents through it. An elastomeric tube is squeezed along a length by rollers that push the ﬂuid contained within. The tube’s restitution after squeezing produces a vacuum that draws ﬂuid continuously into the tube. This creates a gentle pumping action that doesn’t cause any damage to the product. Contaminations are avoided because the ﬂuid is contained within the tube (the only part of the pump that comes in contact with the pumped media). The pump employs a rotor with rollers mounted on it that continually compress and occlude some portion of the tube. This action moves the ﬂuid through the tube with a constant rate of displacement for each revolution of the rotor, enabling a precise measurement of the volume of fluid pumped through the tube.
Where to use a peristaltic pump?
Peristaltic Pumps can be used by many industries for a variety of applications. Some of these include, but not limited to:-
- Water and Wastewater Treatment Plants for pumping sludge and dosing chemicals
- Food and Beverage Industry for the gentle transfer of product through food grade hoses
- Chemical manufacturing for processing or transferring chemicals through a variety of hoses compatible to the fluid to be pumped
- Mining for the transfer of slurries and dosing chemicals
- Pulp and Paper Industries for dosing chemicals
- Ceramic and Metallurgy industries
- Marine, Construction and Biogas industries
Why use a Peristaltic Pump?
A peristaltic pump has many advantages over other types of positive displacement pumps.
Unlike lobe pumps or helical rotor pumps, peristaltic pumps do not have seals. And unlike diaphragm pumps, they do not have valves. These are areas that can become problematic.
A major overhaul on a peristaltic pump [generally a hose replacement] is simple to do and costs will generally be less than 20% of the pump cost. A lobe pump or helical rotor pump major overhaul will generally take much longer [causing lengthy downtime] and cost between 50-80% of the cost of the pump.
A peristaltic pump can run dry without damage, so if a suction blockage occurs or a pump cut-off switch fails, there is no costly repair bill. This cannot be said for helical rotor or lobe pumps, where running dry would cause major damage.
How to apply Peristaltic Pumps
The first thing to consider when selecting a peristaltic pump is whether the duty is continuous (8+ hours of continuous operation), or whether it is intermittent (eg. 1 hour on, one hour off). This will determine how fast the pump can be operated.
The next step is to determine the flow and pressure the pump needs to produce. Higher pressures will determine clearance settings for rollers etc.
Next is to take into account the fluid being pumped and determine a suitable hose material to suit. Some chemicals will require hoses with “good” or “excellent” ratings for that particular chemical. Higher pressure applications will need hoses rated for the pressures of the application. Food products will require hoses with FDA-CFR certification, and hoses requiring CIP or SIP will need to be temperature rated for the hot water or steam cleaning required.
The temperature of the pumped media also needs to be considered to ensure hoses are rated for the required temperature.
Lastly, determine whether the pump needs pulsation dampeners. Generally recommended when pumps are:
- On a suction lift
- Pumping high pressures
- Running faster than “standard” speeds.
What to look for in a Peristaltic Pump?
There are many types and manufacturers of Peristaltic pumps. Industrial peristaltic pumps can be purchased for light duties or short term applications, but those looking for a pump that will deliver years of dependable service, should look for the following:
- Cast and machined housings instead of fabricated ones.
- Cast rotors instead of fabricated ones
- Rollers instead of shoes (so that the pump does not need to be filled with lubricant that needs to be replaced each time a hose is replaced, and has the potential of contaminating the pumped fluid). Rollers will also allow for the use of leak detectors to quickly detect a failed hose.
- A hose clamping system that includes bolting cast blocks together, instead of a system relying on standard hose clamps.
What are the limitations of Peristaltic Pumps?
As with all pumps, peristaltic pumps are limited by the flow they can produce and the pressure they can develop. With Ragazzini pumps, flows to 180m3/hour can be produced, and pressures to 15 bar can be developed.
The size particle that can be passed by a peristaltic pump is also a limiting factor, with most ranges limited to under 60mm of spherical solid that can be passed by the largest pump.
Peristaltic pumps are also limited by the temperature their hoses can handle. This will generally be between 75oC and 95oC.
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