A skid is a process chromatography system on a frame: pumps, valves, sensors, a column holder and a controller sized for litres rather than millilitres. Choosing one is a question about the process it will run for years rather than about a specification, because the flow range, the number of valves and the records it produces are what decide whether a step can be operated and validated on it.
chromatography skids, and sizing by flow and pressure
A skid is sized on the linear velocity the resin needs multiplied by the column's cross section, which gives a flow range, and on the pressure the packed bed and the flow path generate at that flow. Turn-down matters as much as the maximum: a system that cannot hold five per cent of its top flow accurately cannot run a small column, and a laboratory that will scale up and down needs either two systems or one with a wide verified range. Ask for the flow accuracy at the low end rather than the specification's midpoint.
What the valves and sensors decide
Every step the process needs has to exist in hardware: inlet selection for several buffers, a sample path, column selection if more than one column is plumbed, outlet fractionation, and bypass for the sensors. Sensors are conductivity, pH, ultraviolet at one or several wavelengths, pressure before and after the column, flow and temperature. A step that reads a conductivity setpoint cannot be run on a skid without conductivity in the right place, so the process description is written before the system is specified.
Single use flow paths and cleaning
A stainless skid is cleaned and sanitised in place, which means a validated cleaning procedure, hold time studies and swab sampling, and it suits a plant running one product often. A single use path on the same frame removes cleaning validation and cross contamination risk and replaces it with a consumable cost per batch and a supply chain to qualify. Multi-product facilities increasingly buy both on one frame, and the deciding arithmetic is batches per year against the cost of a cleaning validation.
Buffer preparation beside the skid
Chromatography consumes buffer in tens of column volumes, so buffer preparation and hold capacity is part of the purchase even when it is quoted separately. In-line dilution or in-line conditioning from concentrates cuts the vessel count and the floor space substantially, at the cost of a more demanding control loop and its own validation. Whichever route is chosen, the volumes have to be worked out from the method's own column volumes per step, since a skid that outpaces its buffer supply simply waits.
What the controller has to record
On a process system the record is part of the product. The controller has to log every sensor and every valve action against time with a user and a reason for any manual intervention, hold the recipe under version control, and export a batch report a quality unit will accept. Ask to see a real batch record from the software rather than a screenshot, check how a recipe change is authorised, and confirm the system's own qualification documents are supplied rather than written by you afterwards.
single use chromatography, and what a single use chromatography system changes
A single use flow path replaces cleaning validation with a consumable: tubing, sensors and a prepacked column arrive gamma-irradiated and are discarded after the batch, so there is no hold time study, no swab sampling and no cross contamination argument between products. What changes operationally is the supply chain and the cost per batch, since every run consumes a set, and the qualification moves to the supplier's own change control. Multi-product facilities and clinical programmes buy it for the changeover time; a plant running one product often still favours stainless.
single use valves, and what a single use valve costs to gain
Valves in a disposable path are pinch valves acting on tubing, or preassembled manifolds with membrane valves, rather than the rotary and diaphragm valves a stainless skid uses. The gain is that nothing product-contacting is cleaned. The costs are real: fewer positions in a practical manifold, a flow path designed before the batch rather than reconfigured during it, a pressure rating below stainless, and tubing that creeps under long compression. So a single use step is designed with the valve count fixed, which is why the process description comes before the hardware.
Questions people ask about chromatography skid
How is a skid sized?
From the resin's linear velocity and the column's cross section, which give the flow, and from the pressure the bed generates at that flow. The low end of the range matters as much as the top.
Stainless or single use?
Stainless suits a plant running one product often and carries cleaning validation. Single use suits multi-product facilities and trades that validation for a consumable cost per batch.
What is often left out of a quote?
Buffer preparation and hold capacity, the qualification documents, and the sensors a particular step needs in a particular position.