Guide
Word
Deviation Causes
Consequences
Safeguards
Action Required
NONE NO FLOW (1) Blockage in line - Loss of flow to reactor, noreaction due to control response. - DEA solidifies in line.
- Possible line rupture due to pump overpressure.
- Pump motor burn out, possible fire. - Line is electrically traced to maintain DEA as liquid. - Pump is tripped by pressure in line. (a) Temperature indicator and controller needed on line to control tracing. (b) Design pipes to take maximum pump pressure. (2) Solid DEA in tank As for (1)
- Cavitation in pump
- (c) Heat tank using
jacket and/or coil (3) Pump fails As for (1)
- DEA stays in storage tank - Backflow through valve V-8 - Heat exchanger overheat, line expansion
- Standby pump Covered by (a), (b), (c)
(4) Pressure in line = pressure in reactor
As for (1) and (3) - Pressure controller on reactor - Pressure controller on line Covered by (a), (b), (c)
(5) Valve fails closed or blocks
As for (1) and (3)
- Overpressure in line before valve leading to rupture. - Bypass valve in place (d) Regular inspection and maintenance of valves.
(6) Leak or drain left open
As for (1) to (5)
- DEA released from pipework – hazardous.
- Potential damage to surrounding
- FRC on line - Trip on pump
(e) Put a blanking plate on drain flange plate.
equipment. inspection of lines to look for leaks.
(g) Use flow controllers on all lines with the potential to leak. (7) Empty tank/leak in
tank/LSL fails
As for (1) to (6) - Level alarm on tank. (h) Ensure regular inspection of tank for leakage. (8) Heat exchanger blockage
As for (1) to (7) - (g) Ensure good
heat exchanger cleaning and inspect after cleaning.
MORE OF MORE FLOW
(9) Pump overpower or both pumps operating
- Heat exchanger cannot heat stream enough – DEA solidifies - Reactor overflow/overpressure - Excess DEA in reactor passing through process
- Possible line rupture
- Electrically traced line for preventing solidification - FRC on line
(h) Use a locking off procedure for pump not in use.
(g) Surge meter to prevent pump overpressure (10) FRC gives incorrect
value (too low)
Same as (9) - (i) Check FRC
regularly
(11) Valve failure Same as (9) - Valves fail
closed
(j) Design valve for maximum pressure (12) Lower pressure in reactor Same as (9) - Pressure controller on reactor Covered by (a) to (j)
LESS OF LESS FLOW (13) FRC gives incorrect value (too high)
- Less reaction
- Higher DEA outlet temperature from heat exchanger
- Insufficient reactor pressure - Potential higher flow in other
sections of line possibly leading to pipe rupture
(14) Partial blockage/leak in pipe
Same as (1), (6) and (13) Discussed previously
Covered by (a) to (j) (15) Pump underpowered Same as (13)
- Backflow of nitrogen into DEA line
- (k) Fit non return
valve to reactor inlet.
(16) High reactor pressure
Same as (13)
- Reactor vessel rupture
- Relief valve for reactor
- Pressure controller on reactor
Covered by (a) to (k)
(17) Valve stuck partially closed
Same as (13) - Valves should
fail closed
Covered by (a) to (k) (18) Fouling in pipes and
heat exchanger
Same as (13)
- Reduces heat transfer which could lead to DEA solidifying
- Covered by (a) to (k)
(19) Insufficient DEA in tank
Same as (13)
- Potential cavitation in pump
- Level alarm on tank Covered by (a) to (k) REVERSE REVERSE FLOW (20) High reactor pressure
As previously discussed Reactor pressure control
Covered by (a) to (k) (21) Reactor isolation
valve fails open
- Backflow of reactor contents (including hydrogen) to DEA line
- (l) Add FIC to all
reactor inlet lines, shut down if backflow into DEA line is detected. MORE OF MORE
PRESSURE
(22) Pump overpower Discussed previously - Covered by (a) to (l)
(23) PIC gives wrong value (too low)
Discussed previously - Covered by (a) to (l)
(24) Thermal expansion of DEA due to heat
Discussed previously Discussed previously
(m) Design pipes for higher pressure and
expansion (25) Steam rate
fluctuation to heat exchanger
Discussed previously - Temperature controller on steam flow
Covered by (a) to (m)
(n) Consider
cascading flow and temperature control for heat exchanger steam
(26) Blockage/ closed valves
Discussed previously Discussed previously
Covered by (a) to (n) LESS OF LESS
PRESSURE
(27) Pump failure Discussed previously Discussed previously
Covered by (a) to (n) (28) PIC gives wrong
value (too high)
Discussed previously Discussed previously
Covered by (a) to (n)
(29) Leakage Discussed previously Discussed
previously
Covered by (a) to (n) (30) Valves more closed
than expected
Discussed previously Discussed previously
Covered by (a) to (n)
NONE OF NO
PRESSURE
(31) Solid DEA in tank with pump running
Discussed previously Pipe buckles Discussed previously Covered by (a) to (n) MORE OF MORE TEMPERATU RE (32) Excess steam in to heat exchanger Discussed previously
- Reactant too hot, potential reaction problems
- Vaporisation in reactor - Thermal strain in pipes
Discussed previously
Covered by (a) to (n)
(33) Electrical tracing too hot
Discussed previously Discussed previously
Covered by (a) to (n) (34) Strong sunlight Discussed previously Discussed
previously
Covered by (a) to (n) (35) Tank coil too hot Discussed previously Discussed
previously
(o) Add temperature control to tank
LESS OF LESS TEMPERATU RE (36) Insufficient steam in to heat exchanger Discussed previously
- Insufficient reactor pressure
Discussed previously
Covered by (a) to (o) (37) Tracing failure Discussed previously Discussed
previously
Covered by (a) to (o) (38) Cold weather Discussed previously Discussed
previously
Covered by (a) to (o) (39) Tank coil too cold Discussed previously Discussed
previously
Covered by (a) to (o)
START UP (40) Too fast - Heat exchanger too cold to heat
DEA to required temperature
Discussed previously
Covered by (a) to (o) SHUT
DOWN
(41) Corrosion
(42) Some DEA solidifies in line
Discussed previously Discussed previously