Twelve-Story Riser: A Throttled Valve That 'Reads Normal'
You are at a 12-story office tower for the annual inspection of the wet system. At the riser you find the 6 in. OS&Y control valve open but only four handwheel turns off the backseat; the valve normally takes 22 turns from closed to open. The valve's tamper switch shows 'normal' at the fire alarm panel, and panel history shows no supervisory signal at any time in the past year. Downstream, the double check valve assembly's No. 2 check drips from the test cock. The impairment log has one entry from three weeks ago: 'water off 6 hours, 4th floor build-out,' with no AHJ notification, no fire watch, and no signature. The property manager wants the annual tag and says the valve 'must be open because the switch says so.'
1. Evaluate the valve finding. Is the system adequately supplied, and what does the tamper switch reading tell you?
Read the worked answer
Two independent failures, not one.
- Valve position. Twenty-two turns closed-to-open, found four turns off the backseat, means roughly 80% closed - effectively shut for hydraulic purposes. Some water passes, which is more dangerous than an obviously closed valve: the system looks live and is not. This is a critical deficiency; the riser cannot deliver design flow.
- Supervision. A valve supervisory switch is set to go off-normal within a couple of turns of the fully open position. At four turns open it should be in alarm. It reads normal, and there is no supervisory signal in a year of panel history - the switch is misadjusted, failed, jumped out, or the point is disabled. That is an independent critical deficiency, because every future closure will also go unreported.
- The manager's logic inverts the purpose of supervision: the switch exists to detect an abnormal valve, and a switch that never reports abnormal proves nothing.
Corrective action: open the valve fully, then prove the switch by taking the valve off-normal, observing the signal at the panel and the supervising station, and restoring it. If it does not signal, repair or replace and retest. Both items are reported as critical.
2. What should have happened during the six-hour shutdown three weeks ago, and what do you do about it now?
Read the worked answer
What the record shows.
What the impairment procedure requires:
- Notify the owner and, before the impairment where practicable, the AHJ and fire department.
- State the extent (which risers/floors), expected duration, and compensating measures - fire watch in affected areas, hot-work prohibition, occupant notification, extra extinguishers, expedited response.
- Record start and end times, who isolated and who restored, and what verification was done at restoration.
What the log shows: a duration, no notification, no fire watch, no signature. That is a procedural and documentation deficiency, and it matters because the log is the only evidence the system was ever restored. Verify restoration by test - valve position, main drain, alarm - rather than accepting the entry at face value.
Going forward, give the manager a one-page impairment form and a pre-planned procedure so the next shutdown is executed and recorded correctly, and note the past event in the report without overstating what you can prove.
3. The valve is now fully open. What testing and records work remains before the annual certificate?
Read the worked answer
Before the annual certificate.
- Prove supervision in both positions with the monitoring company on the line; record the times and the signal received at the panel and the supervising station.
- Re-baseline the main drain. Run the test now that the valve is fully open and record static and residual. Every prior reading was taken through a throttled valve; using them as the baseline would understate the real supply and could later mask a genuine 10% loss. Note the reason for the new baseline in the report.
- Investigate the dripping No. 2 check test cock. It may be only water trapped in the cock from the last test - open and close it and watch whether it continues to weep at static and under flow. If it weeps under flow, a fouled check seat is passing water, the assembly may not protect the potable supply, and that is a repair plus an assembly re-test, likely with a shutdown.
- Document as-found conditions, notifications, corrective actions, and results, and give the owner a written list of open items. Certify the inspection; do not certify away the deficiency.