Ammonia Plant

The material code first: the designation must carry SPS or SN. Then the pressure class and the code stamp the plant's jurisdiction requires, and the connection type, since ammonia pipework is normally welded steel and the exchanger has to arrive with connections that suit it.

If the unit being replaced is a gasketed or welded exchanger, say so. A brazed pack cannot be opened for inspection or mechanical cleaning, and on some plants that changes the maintenence routine enough to matter. We would rather raise it at the quote than after delivery.

Describing the secondary fluid as "brine" and leaving it there. All the attention goes to keeping copper away from the ammonia, and the other circuit gets a one-word description.

The plates see both fluids. A glycol solution is ordinary duty for 316 plates, but a chloride-bearing brine pits 316, and the damage appears as pinhole leaks between the circuits some time after commissioning. Name the secondary fluid by its chemistry and concentration so the plate material is chosen for both sides of the exchanger at once.

Treat it as a limit, not a target. A maximum flow is set by what the ports can pass, and a selection normally lands well inside it once the allowable pressure drop on the secondary side is taken into account.

Where the plant duty is larger than one pack can carry, units are piped in paralell. That also gives the plant a degree of redundancy and keeps each pack at a manageable size. Send the capacity, the evaporating or condensing temperature and both secondary-side temperatures and we will set the frame, plate count and number of units.

Orientation, oil and freezing. A two-phase duty needs the pack mounted vertically so liquid and vapor distribute and separate as intended.

Oil carried over from the compressors tends to collect at the low points of an ammonia system, so the piping around the evaporator needs a way to drain it; oil coating the plates costs capacity that no amount of surface gets back. On a water or weak-glycol chiller, add flow proving and freeze protection. Water freezing in the channels can split a pack, and on this duty that puts ammonia into the secondary loop.