Why the A-Measurement Matters When Closing a PHE
Why the A-Measurement Matters When Closing a PHE
A plate heat exchanger rarely leaks because the bolts are loose. More often it weeps because the pack was closed to the wrong gap. The plate heat exchanger A-measurement is the figure that keeps that gap right, and it is worth understanding before the next service.
What Is the A-Measurement on a Plate Heat Exchanger?
The A-measurement is the distance between the inside face of the frame plate and the inside face of the pressure plate, with the pack compressed. Every unit leaves the factory with its own figure, set by the plate count and the plate depth, and it appears on the PHE drawing and, on most units, the nameplate.
Note it while the pack is still tight. Recorded early, it is the only reliable reference you have once the unit is open.
Too Loose and Too Tight
Close the pack short of the figure and the gasket never reaches the compression it needs. The unit weeps at start-up, or the gasket blows out at the first pressure surge. Close it past the maker's lower limit and the gasket is crushed; press further and the plates deform. There is an upper and a lower limit, and the safe window sits between them.
Plate Heat Exchanger Tightening Torque Is Not the Target
Operators often ask for a plate heat exchanger tightening torque value. The target here is the A-measurement. Tighten the bolts crosswise and evenly in small steps, keeping the frame plate and pressure plate parallel, until the pack reaches the figure. Chasing a weep with more torque is where over-tightening plate heat exchanger gasket damage begins, and it is far harder to undo than to avoid.
Getting the figure right also heads off the plate heat exchanger leaks after maintenance that turn up days later, once the duty is back on.
FAQ
Q: Where do I find the A-measurement?
A: On the PHE drawing and, on most units, the nameplate. If neither is to hand, measure and record it before you open the pack.
Q: What if I have changed the number of plates?
A: Use the new figure issued with the revised plate count. The old value no longer applies.
Q: Can I close to a slightly tighter gap to stop a leak?
A: Only within the limits the maker allows. Below the minimum, the gasket and the plates are at risk.
Need the Right Gasket?
Send a photo of the nameplate and the old gasket, plus your fluid and temperature. We will match the part and quote. Email info@newroc-phe.com.
