Outlined here is a comprehensive 25-Step guide on peristaltic dispensing pumps, which we have worked hard to cover all aspects you would need to consider. Should you have any queiries about what we've described below or simply require more information please feel free to contact us.
1 - What are the primary uses of dispensing peristaltic pumps?
These pumps have the advantage of only allowing the substance being pumped to interact with the peristaltic pump tubing, which decreases the risk of contamination from other parts commonly found in other pump types. Therefore, they are particularly suited for aseptic filling.
The main applications of dispensing peristaltic pumps are:
Automated aseptic fill/finish in the production of pharmaceuticals, biopharmaceuticals, and drugs is fully implemented.
The preparation of benchtop media or reagents in laboratory suites involves filling or inoculating bottles, vials, Petri dishes, and media bags.
Blister packs and containers for cosmetics and contact lenses filled at high speeds.
Dispensing extracts, fragrances, and other additives.
In food production involving incorporating colours, dyes, flavours, vitamins, and other ingredients.
2 - How to choose a peristaltic pump for the specific dispensing applications?
Calculate the volume to be dispensed and the required dispensing time.
Establish the acceptable level of accuracy for your process.
The final choice is a trade-off between the expense of the substance being pumped and the cost of equipment and consumables, such as peristaltic pump tubing, in this situation.
3 - What dispensing accuracy can be achieved with a peristaltic pump?
The level of accuracy is influenced by several factors, including the dispensing volume. A table is provided below as a reference, and the values shown are obtained from an extremely precise pump. For a typical pump head (non-dispensing), a safe assumption would be 5-10% accuracy.
No.
Dispensing volume (uL)
Accuracy
CV
Tubing element ID (mm)
1
30
0.83%
0.38%
0.5
2
40
0.71%
0.41%
0.8
3
90
0.57%
0.29%
1.2
4
120
0.43%
0.16%
0.5
5
130
0.83%
0.50%
1.6
6
270
0.26%
0.08%
0.8
7
400
0.58%
0.27%
2.4
8
530
0.43%
0.13%
1.2
9
760
0.42%
0.14%
3.2
10
990
0.47%
0.15%
1.6
11
1610
0.46%
0.06%
2.4
12
2480
0.17%
0.05%
3.2
* The results shown in the table above may vary depending on the substance being pumped, as well as other factors, and can differ based on the specific application.
4 - What we need to determine after we select the pump head?
After selecting the appropriate pump, it is necessary to optimize the dispense settings, which typically include the top dispense speed and the ramp-up and ramp-down profile, also known as the speed profile, as well as the suck-back angle, which determines how far back the rotor will move back (reverse) after each dispense to prevent dripping.
The tubing's quality is critical, as even an excellent pump head may not provide significant advantages if the tubing is not pump grade.
To ensure the best results, it might be necessary to test and validate the tubing from multiple suppliers, and the final validation step should involve testing the same tube with different batch part numbers.
5 - How do you classify peristaltic pump tubing, and what is tubing smoothness?
Tubing is classified as transfer, pump grade, or dispensing. The final design may include a combination of dispense and transfer tubing.
The tubing's smoothness and the residue left in the tubing after each dispense are other essential factors. Ideally, the tubing will leave no residual liquid and provide the best accuracy. To determine the residue, the tube can be weighed before and after each measurement.
6 - What is a recipe?
Dispensing settings are like recipes that specify the speed, ramp-up and ramp-down profiles, suck-back angle, time between dispense cycles, and dispense time, among other factors.
7 - What is suck back angle (suck back angle)?
The suck-back angle, which determines the amount of backward movement of the rotor after each dispense to prevent dripping, is also an important factor.
8 - What is the password protection?
Dispensing pumps of higher quality will feature password protection to prevent unauthorized access and alteration of dispensing settings.
9 - What to watch for when doing validation work for dispensing tubing?
When conducting validation work for dispensing tubing, it is important to determine if the tube set needs to be gamma irradiated before use. This is because the gamma irradiation process can impact the tubing's performance. Additionally, final testing should be conducted on samples that have undergone gamma irradiation.
10 - Will the volume dispensed change with the number of doses?
The dispensing tubing will experience changes with use, and it is important to decide whether to run the tubing before each use to improve accuracy or if calibration will suffice. This process is known as "running in" the tubing.
11 - How to select a dispensing needle for peristaltic pumps?
The type of dispensing needle needs to be selected early in the project as it will affect dispensing performance. Testing with a different needle than the final design can significantly affect the results.
The material of the needle should be compatible with the substance being dispensed. For example, if dispensing corrosive substances, a stainless steel or PTFE-coated needle may be necessary.
The tip of the needle will depend on the substance being dispensed and the accuracy required.
The connection of the needle should be compatible with the peristaltic pump tubing being used.
12 - Pulsation with peristaltic pumps, which can potentially harm the substance being dispensed. How to minimise the effect?
However, Equilibar has developed a solution to this problem through their product, which can effectively mitigate the negative effects of pulsation. In particular, their single-use pulsation dampener has proven to be quite effective.
Ramping up and ramping down cycle refers to the process of gradually increasing or decreasing the speed of a peristaltic pump during dispensing. This is done to prevent splashing or foaming and to improve accuracy. The pump starts at a slower speed, ramps up to a higher speed for the majority of the dose, and then ramps back down to a slower speed at the end of the dose. This process is often programmable and can be customized to the specific needs of the dispensing application.
14 - What is drip/back angle control?
This function that can be programmed to avoid dripping of substance pumped after each dispensing cycle. To accomplish this, the peristaltic pump's direction is briefly reversed at the end of each dose, ensuring that any residual liquid is drawn back into the tubing instead of being allowed to drip out.
15 - In what way can the design of the peristaltic pump head decrease pulsation?
Although peristaltic pumps are generally less pulsatile than most positive displacement pumps, they still exhibit some level of pulsation. The peristaltic pump head design involves compressing twin tubes using offset tracks to split the inlet flow, generating two sets of pulses that are out of phase with one another. These channels are then combined at the discharge, resulting in the cancellation of one pulse by the flow of the other, which leads to a uniform and smooth outlet flow. This is acheieved very well using the DMD15-13 Low Pulse pump head.
Phase compensation schematic
16 - Why install a filling nozzle?
To make the droplets more predictable and easier to control, it is recommended to install a filling nozzle with suitable geometry.
17 - Will the length of the tubing affect dispensing accuracy of peristaltic pump?
Additionally, the delivery and suction tubes should be kept as short and direct as possible, with bends of a large radius (at least four times the tubing diameter) to avoid pipe reducers and lengths of smaller bore tubing than the pump head section.
18 - Where should the pump be placed to increase the peristaltic pump dispensing?
The pump should ideally be located at or just below the level of the fluid to be pumped to ensure a flooded suction giving maximum pumping efficiency.
19 - How to effectively dispense viscous substances with peristaltic pumps?
When pumping viscous fluids, it is recommended to run the pump at a slow speed, with a 2.4mm wall thickness tubing for the best results.
20 - When to recalibrate the peristaltic pump in an open loop dispensing system?
The pump should also be recalibrated after changing pump tubes, fluid, or any connecting pipework, and periodically to maintain accuracy.
21 - What is gravimetric dispensing?
If dispensing by weight, Gravimetric systems integrate a balance and are as accurate, as the accuracy of the scales. Good peristaltic systems integrate with scales creating a closed loop dispensing system enabling to dispense without the need of calibration and recalibration.
Volumetric dispensing can be added to existing systems via a clamp-on sensor or offer direct flow measurement.
Ultrasonic clamp-on flow meters are available to measure the flow rate with claimed accuracy up to 2% deviation from actual flow.
The pump system can compensate for variabilities in flow, including cold tubing, worn tubing, back pressures, and fluid friction, by measuring the actual flow rate and automatically adjusting the drive speed to overcome any inconsistencies. It is ideal for micro-volume filling with high precision and efficiency to prevent costly overfilling and has a modular design.
23 - What are suction and delivery tubing, and should these be used with peristaltic pumps?
Do use suction and delivery pipes equal to or larger than the bore of the tube in the pump head. When pumping viscous fluids use pipe runs with a bore several times larger than the pump tube.
24 - What is an open loop dispensing system?
Its dispensing without a feedback signal from lab scales or flow meter only feedback component.
25 - What is modular design of peristaltic pump dispensing system?
You can use one touch screen or PLC to control many pumps to making the system most effective. Not every pump needs to have separate control unit. The dPOFLEX PFS filling system would be a more than capable choice.
Get in touch
Contact our engineers today if you have any questions regarding your dispensing pump application by calling 01953 609930 or email sales@pctflow.com.
