KrosFlo® Permeate Scale (QTY Permeate Scale)

KrosFlo® Permeate Scale (QTY Permeate Scale) — Product Introduction

The KrosFlo® Permeate Scale, also referenced in system documentation as the QTY Permeate Scale, is a precision electronic weighing device developed by Repligen Corporation (formerly Spectrum Laboratories) and engineered specifically for integration with KrosFlo® Tangential Flow Filtration (TFF) systems—including the KR2i®, KMPi®, KrosFlo FS-Series, and KrosFlo RS-Series platforms. Its primary function is to provide real-time, gravimetric measurement of permeate (filtrate/through‑liquid) mass accumulated in the permeate collection vessel during ultrafiltration (UF) and diafiltration (DF) operations. By replacing manual volume readings from graduated cylinders or beakers, the Permeate Scale enables fully automated process control, accurate flux calculation, and GLP/GMP-compliant electronic data capture.

Operating Principle and Workflow Integration

In a typical TFF process, feed solution is recirculated tangentially across a membrane surface. A portion of the liquid passes through the membrane pores as permeate and is directed into a collection container—usually a single-use bag, bottle, or stainless-steel vessel—which rests on the Permeate Scale. The scale's load cell continuously monitors the increasing mass of the permeate container, transmits the signal via RS‑232 (or optional USB/Ethernet) to the KrosFlo system controller or KF Comm® data acquisition software, and the system computes both cumulative permeate mass/volume and instantaneous permeate flow rate (g/min or mL/min). The controller can then use this information to trigger process endpoints (e.g., target diafiltration volume), adjust pump speed to maintain a desired flux, or generate audit-trail reports for regulatory review.

Prior to a run, the operator places the empty permeate container on the scale and performs a tare/zero operation—either manually on the scale's keypad or automatically via the KrosFlo software. During filtration, the scale compensates for minor environmental vibrations through built-in digital filtering, ensuring stable readings even in active laboratory or pilot-plant environments.

Key Features and Benefits

• High-Precision Gravimetric Monitoring:​ Available in multiple capacity grades—from analytical-scale 400 g (readability 0.01 g) for early R&D work to pilot/production models up to 250 kg—the Permeate Scale delivers resolution ratios as fine as 1:10,000–1:12,500, suitable for low-flux hollow-fiber or cassette membranes.

• Seamless System Integration:​ Native compatibility with Repligen KF Comm® and KlariFi™ software allows permeate mass data to be logged alongside transmembrane pressure (TMP), recirculation flow rate, and temperature, producing a complete, time-stamped process record that supports 21 CFR Part 11 compliance when deployed in validated environments.

• Bio-Process-Friendly Construction:​ The weighing platform and support column are fabricated from 304-grade stainless steel with a smooth, crevice‑free finish. Selected models feature a detachable platform, sealed indicator housing (IP66), and waterproof stainless loading template (IP67), protecting internal electronics from accidental splash or routine sanitization with mild detergents.

• Robust Overload Protection:​ Equipped with a 5- or 6-point mechanical overload protection system rated up to 150 % of full-scale capacity, safeguarding the strain-gauge load cell against inadvertent placement of heavy vessels.

• Dynamic Readout and Alarms:​ Large, high-contrast LCD displays (with white LED backlight on larger models) present stable mass readings; production-scale units add tricolor checkweigh LEDs for rapid visual status indication. Programmable high/low weight alarms can be linked to system interlocks to pause or terminate a run when a preset permeate mass is reached.

• Multiple Scale Options for Process Scale-Up:​ The same fundamental technology scales from bench (400 g / 4 kg) through pilot (10–50 kg) to commercial manufacturing (100–250 kg), allowing consistent permeate monitoring methodology across the entire biopharmaceutical development lifecycle.

Typical Applications

The KrosFlo Permeate Scale is widely used in:

• Monoclonal antibody / recombinant protein concentration and diafiltration​ — determining DF buffer exchange ratios via cumulative permeate volume.

• Viral vector and AAV purification​ — gentle, low-shear monitoring of permeate generation from shear-sensitive samples.

• Plasmid DNA and mRNA cleanup​ — precise tracking of desalting or buffer exchange progress.

• Cell culture harvest clarification​ — quantifying filtrate yield from microfiltration steps.

• Exosome / nanoparticle isolation​ — low-volume, high-resolution permeate detection in research settings.

Installation and Compliance Notes

The scale is supplied with a leveling foot system and bubble indicator to ensure correct horizontal placement, which is critical for gravimetric accuracy. Power is selectable 100–120 V or 220–240 V AC, 50/60 Hz depending on region and model. When used in GMP facilities, the Permeate Scale can be included in equipment qualification protocols (IQ/OQ) and its serial communication output supports integration into site-level Manufacturing Execution Systems (MES) or LIMS.

Technical Specifications

Data summarized from Repligen KrosFlo system documentation and product datasheets. Specific model availability and specifications are subject to change—please consult the current Repligen datasheet for your region.

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