SWEP S500T

They cannot be told apart by dimension or material: both are 979 x 304 mm with 316/316L plates, copper braze and a 684.65 GPM max flow. The difference is the model itself. The S500T is the evaporator in this frame size, optimized for very demanding chiller applications, while the B500T is the base model the frame is named after.

For a replacement that settles the question quickly. If the nameplate reads S500T, the replacement is an S500T with the same plate type, plate count, material code and pressure class. A B500T that fits the brackets is not evidence that it will hold the chiller's evaporating temperature.

Any fragment of the designation helps. The catalogued S500T configurations read S500Tx50, S500Tx90, S500Tx130, S500Tx170 and so on, between 50 and 220 plates, so a surviving plate count narrows it sharply. A legible article number does the same.

With nothing readable, measure the 979 x 304 mm outline and the port centres to confirm the frame, count the plates along the edge of the pack, and record the type and size of each connection. The material code and pressure class cannot be measured; give us the refrigerant and the design pressure on the chiller's own data plate and we will confirm them.

No. 684.65 GPM (155.5 m3/h) is the ceiling set by the ports, not a design point. A real selection lands well below it, at the flow where the pressure drop through the chosen plate count is acceptable to the pump.

The time to look beyond a single S500T is when the design water flow approaches that ceiling, or when the allowable pressure drop cannot be met even with a large plate pack. The usual answer is the one modular chillers are built on: split the duty across two or more units in parallel. See Pressure Drop.

Mount it vertical and pipe the water counter-current to the refrigerant. On a 979 mm tall body the upper and lower connections are far apart, so pipe strain has a long lever to work with - support the headers on their own steelwork and let the unit stand on its base.

In a modular chiller, each module's exchanger should see the same water flow. Unbalanced headers leave one module short of flow, and that module runs colder and is the first to trip on low temperature. At 220 plates the published formula gives about 240 kg (529 lb), so plan the lift.

The frame builds to 420 plates; the configurations on file run from 50 to 220. More plates add surface, cut water pressure drop and tighten the approach. They also add depth, and weight at 1.0186 kg (2.246 lb) per plate.

On an evaporator the gain is not free. Spreading the same refrigerant flow over more channels lowers the velocity in each one, and at part load that can upset distribution and oil return. Choose the plate count from a rating at both full and minimum load. Plate Count and Capacity explains the trade.

These models are catalogued alongside the S500T. Each has its own page with its dimensions, materials and part numbers.

SWEP B500T - Shares the B439 envelope with a different plate generation.