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Quotes - Engineering - SalesEngineering and Selection
How a Plate Selection Gets Made
Eight figures size a gasketed plate unit. Per side: how much fluid moves, how hot it arrives, how cold it has to leave — and how much head that side can afford to lose. The first six fix the area. The last two decide whether that area can be arranged into a pack your pumps will actually push through.
Area is the easy half. Plate heat transfer coefficients are high and predictable, so the arithmetic converges quickly. What takes judgement is the channel arrangement — how many passes, how many channels per pass, which plate pattern — because that is what trades approach temperature against pressure drop. The same plate count can be arranged into a unit that hits a 2°F approach at 12 PSI, or one that hits 5°F at 4 PSI. Both are correct answers to different questions.
Tell us which constraint is hard. If the pump curve is fixed, say so and we will hold pressure drop. If the approach is contractual, say that instead and we will tell you what it costs in head. A selection made without knowing which one binds is a guess that looks like an answer.
What Belongs in the First Email
Name both fluids and say what state they are in. Propylene glycol at 40 percent is a different selection from ethylene at 25, and a stream carrying fibre is a different selection again — that is what points at a free-flow plate rather than a standard herringbone pack.
Then the envelope: design pressure and design temperature each side, the space the frame has to fit, and the connection sizes and orientation if it ties into existing pipework. If the duty is potable, sanitary or subject to a jurisdictional requirement, that belongs in the enquiry rather than in the order.
The Design Point Is Not the Whole Job
Ask what the unit runs at for most of the year, not just what it has to survive on the worst day. A pack sized only for peak load runs at low channel velocity the rest of the time, and low velocity is what lays down fouling on a plate surface.
Startup and upset matter too. A unit brought up cold against full steam sees a thermal transient the steady-state calculation never shows, and gaskets remember it. Give us the low end of the load as well as the peak, and say whether the unit cycles.
Selection Notes
Which Construction Answers Which Duty
Clean liquid-to-liquid duty is the standard gasketed Accu-Therm pack. Product contact, CIP and 3-A requirements point at the sanitary construction. A refrigerant on one side points at semi-welded, where plate pairs are laser welded so no gasket sees the refrigerant. Streams carrying fibre or particulate point at free-flow, whose wide unobstructed channel passes what a herringbone pack would bridge. Where a leak between the two media is unacceptable to an authority, double-wall construction vents any breach to atmosphere where it can be seen.
Away from the gasketed frame: Temp-Plate embossed panels put the heat transfer surface into or onto a vessel rather than in a pipe run; brazed plate covers small, clean, high-pressure duty with no gaskets at all; and falling film chills water directly on the evaporator surface without a glycol loop in between.
Fouling Allowance Is a Decision
A plate unit does not want the generous fouling factor a tubular unit is often given. Over-surfacing drops channel velocity, and low velocity on a plate is what causes the deposition the allowance was supposed to cover. The turbulence a herringbone pattern generates does more for fouling resistance than extra area does.
What we would rather have than a table value is your own history: water analysis, cleaning interval, and what the last unit on the same service looked like when it was opened. If you have that, send it.
Leave Room in the Frame
A gasketed frame can carry more plates than it ships with, if the carrying bar and tie bolts were specified for it. Deciding that at purchase costs very little. Discovering later that a debottlenecked process needs thirty percent more duty, and that the frame cannot take it, costs a new frame.
Leave physical room too. The pack has to open for inspection, which means clearance in front of the follower plate at least equal to the pack length, plus room to swing plates out on the carrying bar.
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