A laboratory vacuum pump should be compared using both pressure capability and pumping speed, together with compatibility and the limits of the connected equipment. One pressure number does not describe the performance of the whole system.
Clarify the pressure reference
Check whether a quoted pressure is absolute or relative to atmospheric pressure. Record the unit and the measurement conditions. Values using different references cannot be compared safely by their numerical size alone. If a catalogue uses an ambiguous vacuum rating, request the manufacturer’s definition.
Separate ultimate pressure from pumping speed
Ultimate pressure describes a pressure limit under specified test conditions. Pumping speed describes how quickly gas can be removed under stated conditions. Actual system behaviour also depends on leaks, restrictions, vapour load and the equipment connected. Do not assume a pump will achieve its headline pressure in every installed system.
Check compatibility and maintenance
Ask the manufacturer which gases and vapours the exact pump can handle, which materials contact the process stream and what protective arrangements are required. Confirm the applicable maintenance and service requirements. These details can change the suitability and running cost even when two pumps have similar headline ratings.
Evaluate the complete assembly
Verify the pressure limits of vessels, tubing, fittings and instruments independently. Confirm electrical requirements and the accessories included in the quotation. Ask which measuring device is appropriate for the intended pressure range. A nominal pump rating is not evidence that every connected component is compatible.
A useful comparison record
Record the model, pressure reference and unit, pumping speed and its conditions, compatibility information, required accessories and service documentation. Identify any unresolved points before comparing total costs. Use the manufacturer’s instructions for selection, installation and operation; this guide is a way to organise the questions, not an operating procedure.
Worked example: resolving a pump-frequency mismatch
The Synthetika listings state 99 mbar absolute and 31 L/min for Rocker 400C, and 25 mbar absolute and 23 L/min for Rocker 410C. Both pages also state 220 V/50 Hz. These are transcribed listing values, not measurements made by Lidocaineshop.
Rocker’s indexed 2025–2026 guide separates the 410C maximum flow as 23 L/min at 60 Hz and 20 L/min at 50 Hz. This creates a specific question to resolve before using the supplier’s 23 L/min figure for a 50 Hz unit. The full manufacturer PDF could not be downloaded during this check; obtain the current manual for the quoted item code.
Do not combine a maximum flow and an ultimate pressure into a claimed simultaneous operating point. Request the relevant performance curve and exact electrical variant. This comparison records a discrepancy; it does not declare which supplied unit has been tested.
Sources and editorial record
Synthetika: Rocker 400C listing
Synthetika: Rocker 410C listing
Rocker: 2025–2026 manufacturer product guide (PDF)
Publisher: Lidocaineshop. Source check: 25 October 2026. Prepared with AI assistance. No independent laboratory testing, batch certification or supplier endorsement is asserted.
Related guides
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Laboratory equipment: a specification and documentation guide
How to prepare a laboratory request for quotation
Prepared with AI assistance. Check product-specific claims against the documents for the exact batch or model.
A water-circulating pump needs two separate specification records
LANSGT’s SHZ pump page distinguishes desktop SHZ-D(III) variants from the vertical SHZ-95B family and describes both vacuum generation and circulating-water functions. The family page does not establish the configuration of an individual quotation.
Original comparison exercise: make one row for the vacuum side and another for the water circuit. Treat the missing values as questions to resolve, rather than importing figures from a similar-looking pump.
| Record | Ask the manufacturer to specify | Avoid this assumption |
|---|---|---|
| Vacuum side | Pressure reference, units, test conditions and pumping performance for the quoted model. | A water-flow figure is not the gas-pumping speed. |
| Water circuit | Circulation rating and the conditions attached to it. | A circulation claim does not establish the cooling performance of the whole installation. |
| Materials | The materials exposed to the intended medium and the variant identifier. | A broad corrosion-resistance claim is not a compatibility confirmation. |
| Electrical variant | Nameplate voltage, frequency and model-specific documentation. | Specifications from different electrical variants are interchangeable. |
No operating values are supplied in this exercise. Selection and operation require the manufacturer’s instructions for the complete assembly. Keep any answer with its document revision so that a later model substitution cannot silently inherit an earlier assessment.
Compare the equipment catalogue with the equipment documentation guide; the catalogue identifies the item to investigate, while the guide organises the evidence still needed.
Source review: 25 October 2026. Publisher: Lidocaineshop. Original editorial exercises prepared with AI assistance. Supplier statements are attributed to their source; no independent product testing, certification or commercial partnership is claimed.