Instrument Inspection Report

Jika ada sebuah instrument (sensor, controller, actuator atau apapun) yang mengalami ketidak beresan, maka tindakan awal adalah melakukan investigasi, kemudian bari dilakukan tindakan-tindakan yang dianggap perlu.
Berikut ini adalah investigation report yang pernah saya buat, mengenai pekerjaan troubleshooting sebuah PSV model tubular yang dipasang pada sebuah fire pump unit.
Entah benar atau salah, ini hanya coretan seorang teknisi rendahan…

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EQUPMENT INSPECTION REPORT
EQUIPMENT TAG NUMBER:   XXXXX-XXXX
EQUIPMENT DESCRIPTION:   FIRE PUMP “A” DISCHARGE PRESSURE SAFETY VALVE
SERVICE:                                         FIRE SUPPRESSION SYSTEM
REPORT DATE:                             JANUARY 2, 2009
A. Equipment Data
TAG NUMBER: 71PSV-0209
MANUFACTURER: CLA-VAL
SIZE: 8”
CAT. NO.: 850-20
STOCK NO.: 20325618B
CODE: YM
B.  Failure Description
Based on the previous performance test it was reported that PSV was cracking open at 110PSI instead of it supposed to be at 200 PSI


C. Summary of Finding

• Previous report regarding PSV failure was reviewed.
• Inspect internal part of the PSV.
• PSV was pressure tested with pressurized water and air as a media.
• Adjusted PSV, set at 200PSI
• Performed fire pump performance test (this step included the performance of the PSV at once)
• Found 1710 GPM at 153 PSI

D.  Site Observation and Inspection

Manpower involved:

• 3 Instrument technicians
• 2 Mechanical technicians
• 1 field operator

Observation Before Inspection:

Based on the previous report regarding failure of the PSV of fire pump A, it is reported that PSV started to crack at the discharge pressure of below of 110PSI (based in the P&ID, the setting supposed to be 200PSI)

Prior to go too far to the investigation and troubleshooting, following down below is the principle of the PSV used:

Principle of operation

Function Testing:

Prior to go to the further investigation and inspection, for a base-line information purpose, the function test needs to be carried out. Following procedure was carried out to perform functional testing of the PSV

To adjust the PSV to its design setting, it was required to provide a 200 PSI pressure signal source to simulate the process pressure. To carry out this task, it was also required to do some tubing lines modification to provide an adjustment arrangement as shown in the following figure 1b.

Original installation and temporary modification

After modification has been done and all equipment required are in place:

1.    Fire pump was run to provide PSV inlet pressure (pump discharge pressure) at 100 PSI.

2.    Pressured up hand pump while monitor P2, found P2 equal to the inlet pressure (i.e. 100 PSI)

3.    At pressure from hand pump reached 110PSI (indicated at P1), P2 started to drop down to 45 PSI, it was indicated that the PSV started to open and passed the pressure from the inlet line down to overboard.

4.    Adjusted pilot regulator (clock-wise) up to maximum it can turn, but the P2 could not reach 100 PSI as it supposed to be. This indicated that the PSV was passing

5.    Based on this finding, INTERNAL PART INSPECTION needs to be done.

1. INSPECTION

1.1 Removal

For internal part inspection purpose, the PSV was rotated from the spool to be able to inspect its internal part. Figure 2 below shows how the PSV rotated out of the spool.

Add caption

PSV temporary reposition

1.2 Leak Test without Pressure
After rotated and the internal parts can be seen, then downstream side of the PSV (upper position) was filled with the water to check the diaphragm tightness during no pressure. And the result was no water came out from the upstream side of the PSV (lower position), this indicated that the diaphragm was fully tight during no pressure both at the diaphragm chamber and the process side. See figure 2 below to look more detail.

Downstream side was filled up with the water to check the leak

1.3 Leak Test with Pressure
To check if the diaphragm leaks under pressure, then with upper side still filled up with the water, the diaphragm chamber was pressurized with fresh water as a media with 95 PSI of pressure. During this step, water came out from upper side of the PSV (downstream side) which was indicating that diaphragm leaks (see figure 4b, green colored illustration). Then the pressurization media was changed with pressurized air (100 PSI) instead of fresh water. See figure 4a below to see how the pressurized water/air was applied.

Leak Test

No pressure penetrated thru the diaphragm with air as a media. This was proving that somehow, the leakage has been fixed by stimulate de-formatted diaphragm to back to it’s tubular form.

1.4    Re-installation
After inspection was completed, the PSV put onto the piping as shown in figure 5 below

Re-installation

2.    ADJUSTMENT/RESETING
To adjust the PSV to its design setting, it was required to provide a 200 PSI pressure signal source to simulate the process pressure. To carry out this task, it was also required to do some tubing lines modification to provide an adjustment arrangement as shown in the following figure 6b.

Re-Setting

After modification has been done and all equipment required are in place:

• Fire pump was run to provide PSV inlet pressure (pump discharge pressure) at 100 PSI.
• Pressured up hand pump while monitor P2, found P2 equal to the inlet pressure (i.e. 100 PSI)
• At pressure from hand pump reached 120PSI (indicated at P1), P2 started to drop down to 45 PSI, it was indicated that the PSV started to open and passed the pressure from the inlet line down to overboard.
• Adjusted pilot regulator (clock-wise) up to maximum it can turn, hence P2 back to 100 PSI equal to the inlet pressure.
• Pumped up again hand pump up to 200 PSI, hold the pressure of the hand pump at 200 PSI.
• Turn pilot regulator anti-clockwise to decrease the setting, until the P2 drop down to 45 PSI, which was indicating that PSV started to crack.
• After pilot regulator was set at 200 PSI, while P2 stay at 45 PSI at that moment, decrease pressure at the hand pump gradually until P2 increased equal to the inlet pressure (100 psi).
• It was found P2 back to 100 PSI at P1 (hand pump or pilot pressure) was 180 PSI). It indicated that the PSV fully closed at pilot/sensing pressure at 180 PSI.
• PSV is stated as a correctly set at desired set point at 200 PSI.

3.    PERFORMANCE TEST

• Reinstalled all of the tubing lines of the PSV, as original arrangement, as shown in figure 6a above. But let P2 installed.
• Performed the following procedure (refer to figure 7)
  • Inform panel operator that the job will be carried out
  • Put engine in manual mode
  • Open antisurge valve 100%
  • Put antisurge valve controller in AUTO mode
  • Put engine throttle valve at minimum position
  • Start fire-pump engine either with battery or pneumatic starter
  • Increased engine speed gradually to the rated speed (1760 RPM)
  • Monitor and record performance (see attached log sheet)
  • Close ASV by 10% so it will open 80%, record performance as per log sheet
  • Repeat step 9 by 10% decrement of ASV opening or until the discharge pressure is 150 PSIG.
  • Open ASV 100%
  • Decrease engine speed gradually and stop it
  • Put ASV at 25%
  • Open discharge valve of the fire pump
  • Put engine control in AUTO mode and nominal speed

Simplified flow diagram

PERFORMANCE TEST LOG SHEET

Performance Test Log Sheet

E.    Spare Part Required

• Diaphragm (internal part)

F.  Pictures

PSV in-field ajdusment

Pressure at diaphragm chamber

Outlet of PSV

Piping and Instrumentation Diagram

G.    Failure Root Cause
It is suspected that the tubular diaphragm was temporarily de-formatted (created small tiny hole) by the sudden pressure at PSV’s inlet during commissioning phase, causing the water at the diaphragm chamber escaped thru the diaphragm to the PSV’x outlet hence the PSV open (or crack open)
Why during performance test it worked perfectly? This is suspected that the small tiny hole created by the de-formatted diaphragm was back to its original form and the hole closed, hence the PSV works properly.
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