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The exchanger the process is developed on
A pilot plant runs at 1 to 50 liters where production runs at 2,000, and its heat exchanger has to do two things a production unit never does: change duty every week, and produce numbers that predict the big unit. A 2 sq ft double tubesheet shell-and-tube with 1.5 in tri-clamp ends, or a six-plate gasketed unit on a bench frame, is the standard answer, built to the same finish and joint design as production because the validation package will cite it.
This page covers the small end of the range, quick-change skids, and the trap of scaling up an exchanger that was oversized at pilot.
Sizes, skids, quick-change and scale-up
What the small end of the range looks like
A sanitary shell-and-tube starts at a 1 in shell with seven 0.25 in tubes 12 in long, about 0.7 sq ft, and grows through 2 and 3 in shells to 10 or 15 sq ft before it is a production unit. All of them are double tubesheet if the site wants them to be, with the gap scaled down but still open. Gasketed plate units go from four plates on a bench frame to twenty, with the same plate pattern the production unit will use so the channel geometry scales. Tube-in-tube for viscous pilot product is a single 0.5 in tube inside a 1 in jacket, in clamp sections a technician can rearrange. HeatX quotes these as catalog sizes with lead times of weeks, because a development group waiting on a custom exchanger is a development group not developing.
The skid and quick-change arrangement
The pilot suite wants one utility skid and several exchangers. The skid carries a chiller or TCU connection, a steam or hot water supply, a set of tri-clamp headers and a stand; the exchangers hang on the stand with 1.5 in clamps on both sides and swap in five minutes. A heater and a cooler with a clamp hold tube between them make a pilot pasteurizer or a media sterilizer; the same cooler alone is a buffer chiller; the plate unit replaces the shell-and-tube when the experiment needs a tighter approach. What makes this work is that every exchanger has the same connection size, orientation and stand interface, which is a decision made at the first order and kept.
Making the pilot data scale
Heat transfer scales on velocity and geometry, not on area. A pilot shell-and-tube run at 0.5 ft/s through 0.25 in tubes tells you almost nothing about a production unit at 5 ft/s through 0.75 in tubes, because the pilot ran laminar and the production unit will run turbulent. The pilot exchanger is chosen so that the tube-side velocity and the wall temperature match what production will see, which usually means fewer, longer, smaller tubes than a catalog picker would choose, and a flow rate at the top of the pilot pump's range. Fouling rate, product degradation at the wall and the temperature-time history the product experiences then transfer to the full-size unit with a straight face.
The common mistake
Oversizing the pilot unit because it is cheap to. A 10 sq ft exchanger on a 1 gpm pilot stream reaches the outlet setpoint in the first foot of tube and runs the rest at the utility temperature, so the product sees a long residence at the wrong temperature, the pilot run looks fine because the outlet is right, and the production unit designed from it shows a degradation problem that was never in the data. The pilot exchanger is sized on the pilot duty with the same margin the production unit will have, 15 to 25 percent, not with the margin a spare catalog part happens to offer.
Send the pilot flow range, the temperatures, the setpoint tolerance and the expected production scale, and HeatX picks the unit that still tells the truth at scale-up. Call and talk it through with an engineer: 1-805-484-2992
Lab and pilot plant exchanger process conditions
Small units are specified the same way as production ones, and these rows show that build. Compare the ranges with your experiments and send your fluids, connections and sterilization method for quoting.
| Condition | Detail |
| Product | Buffers, media, WFI, intermediates, solvent streams |
| Flow range | 0.1 to 20 gpm tube side; 1 to 20 sq ft surface |
| Temperatures in / out | Anything from 2 C to 121 C on the product side, set per experiment |
| Hold | Hold tubes supplied as clamp spools, 1 to 60 seconds at pilot flow |
| Utility | Bench chiller or TCU at 1 to 10 gpm; 15 psig steam or 90 C water; house chilled water |
| Approach | 2 to 5 C so the outlet reaches setpoint at the low end of the flow range |
| Construction | Double tubesheet shell-and-tube 1 to 3 in shell, or gasketed plate 4 to 20 plates on a bench frame |
| Finish / class | 316L, 15 to 20 Ra electropolished; ASME BPE fittings; ASME stamp on request |
| Connections | 1 in and 1.5 in tri-clamp product side; tri-clamp or NPT utility side |
| CIP / SIP | Autoclavable or SIP in place at 121 C; fully drains when tipped on its stand |
Common FAQs
Not proportionally. Finish, double tubesheet, welding and documentation cost about the same at 2 sq ft as at 20, so the small unit costs more per square foot.
Shell-and-tube units under about 3 ft with clamp ends fit a standard autoclave with the shell side open. Plate units are steamed in place.
Whichever production will use. If production will be tubular, pilot on tubes even though a plate is more compact; the pilot exchanger exists for data, not footprint.
The same package as production if asked: material certs, finish readings, weld records and pressure test. Many groups take a reduced set and upgrade later.
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