A plate selection turns on six figures: on each side, how much flow, how hot it arrives and how cold it has to leave. Tell us as well what head each side can give up, and what the system is designed to hold, and the answer is settled.
Send those and back comes a model, a plate count, a price and a lead time. The rest — materials, connection sizes, code stamp, the space the frame needs — we settle together.
Everything goes in the message box: how much flow each side, how hot in and how cold out, what head you can give up, and what the system is designed to hold. Swapping out an existing unit? The nameplate — or one clear photograph of a single plate — will usually do on its own.
How much of each fluid moves, how hot it arrives, how cold it has to leave. Six figures, three per side, and the area falls out of them arithmetically. Short one? We can usually solve for it — just say which of the others must not move.
Then the pressure drop each side can spare. On a plate unit this is not a footnote — it is half the selection. The same duty can be met by a short wide pack at low head or a long narrow one at high head, and only your pump curve knows which is right.
Design pressure and temperature come last. They seldom move the plate count and they always move the price, since they set the frame rating, the plate gauge and whether a code stamp is involved. Give us what the relief valve is set at, not what the system runs at day to day.
Water against water is the easy case. Glycol drags the film coefficient down and pushes the flow up for the same duty, and how much glycol matters as much as which glycol. Oil moves it further still. Steam does not fall in temperature at all — it condenses — so on a steam duty give us the pressure at the unit and leave the outlet temperature blank.
Say plainly if either side is potable, is product, or has to meet 3-A. That decides gasket material, whether the construction is sanitary, and whether an authority will require double-wall plates — all of which are cheaper to design in than to discover at submittal.
If a stream carries solids or fibre, say what and how much. It is the difference between a standard pack and a free-flow one, and it is not a detail that can be corrected after the unit ships.
Photograph the nameplate if there is one. A Mueller model designation encodes the frame, the plate pattern, the port size and the rating all at once, which means we can confirm it — or name what supersedes it — without calculating anything.
Where the nameplate is gone, or the unit was built by someone else, we work from the hardware: plate count, plate pattern, gasket profile, port diameter, frame length between head and follower. Clear photographs of a single plate, front and edge, do most of the identification.
The clearance that catches people on a plate unit is not depth for withdrawal — it is room to open the pack. The follower has to travel back at least the pack length, and plates have to swing out on the carrying bar. Against a wall or in a tight plant room, that often sets the frame before the thermal calculation does.
Tell us the real quantity rather than one unit you intend to multiply, because quantity moves price and lead time separately. A need-by date lets us say which selections are on the shelf. A ship-to city puts freight on the quote instead of into a later surprise.