3 replies to this topic

[vaibhav02]

Hi Folks,

 

I’m troubleshooting a puzzling safety-device failure and would appreciate the community’s insight.

 

Plant & Duty

• Unit: Continuous deodoriser for palm oil (7 horizontal vessels, vacuum stripping).

• Heating medium: HP steam loop (~50 bar g @ 240 – 260 °C) from a natural-circulation boiler.

• Rupture disc: REMBE BT-KUB-1, DN25, Inconel®, rated 95 bar g @ 298 °C (batch 2202109). Installed upstream of the safety valve on the boiler outlet; vent stub rises ~4 m, then to atmosphere.

• Transmitter: 54 PI 240 (0 – 100 bar g, 1 s scan rate).

Failure history

Date Operating pressure when disc burst Expected burst Notes 22 Jun 2025 20.6 bar g 95 bar g Header temp 189 °C; no PI spike recorded. Dec 2024 (similar case) ≈ 25 bar g 95 bar g Same disc model & location.

Trend data show repeated shutdown sequences where pressure falls to the transmitter’s low cut-off (≈ 0.3 bar g) for 6 – 18 h, then ramps slowly back to 60 – 70 bar g during startup.

 

Two hypotheses

1. Vacuum-induced low-cycle fatigue

   • During cooldown the closed steam circuit pulls near-full vacuum (transmitter can’t read below 0 bar g).

   • The reverse-acting dome flexes inward; next startup reverses the load to +70 bar g.

   • After a dozen cycles the burst point drifts down to ~20 bar g and the disc finally opens.

   • Evidence: identical pressure cycles every shutdown; no collateral pipe damage; fracture surface shows beach-marks.

2. Single water-/steam-hammer spike

   • Condensate in the 4 m vent stub is accelerated by incoming steam, creating a very short 100 + bar pulse that the PI tag misses.

   • The disc ruptures cleanly at the spike, PI plot only captures the 20 bar tail.

   • Evidence: some startup traces show 30–50 bar oscillations; hammer in similar lines has reached 5–10 × design pressure in literature.

My questions to the forum

1. Have you seen reverse-acting discs derate by >70 % purely from vacuum/pressure cycling? How many cycles did it take?

2. Can a short hammer pulse really shear a KUB-type disc without leaving dents or pipe-support damage nearby?

Thanks in advance for your thoughts!

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[breizh]

Hi,

1) check with manufacturer the possible scenarios,

2) Corrosion is also a possibility together with cycling and spikes

3) Do you have a PM program in place to check regularly the RD condition?

 

Note: It seems to me that the PSV pops up, this means you have an upset in your process!

 

Breizh

[Pilesar]

Rupture disks are susceptible to physical damage during installation as well as corrosion. Installing them within a holder helps protect them.

[latexman]

That is a premium RD that goes into a holder. Agree with breizh, contact the vendor. They are expert at this.