HAZOP Example

[Type text]

Guide Word

Deviation

NONE

NO FLOW

Causes (1) Blockage in line

(2) Solid DEA in tank (3) Pump fails

(4) Pressure in line = pressure in reactor

Consequences

Safeguards

Action Required

- Loss of flow to reactor, no reaction 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. (c) Heat tank using jacket and/or coil Covered by (a), (b), (c)

As for (1) - Cavitation in pump As for (1) - DEA stays in storage tank - Backflow through valve V-8 - Heat exchanger overheat, line expansion As for (1) and (3)

- Standby pump

- Pressure controller on reactor - Pressure controller on line

Covered by (a), (b), (c)

(d) Regular inspection and maintenance of valves. (e) Put a blanking plate on drain flange plate. (f) Regular

(5) Valve fails closed or blocks

As for (1) and (3) - Overpressure in line before valve leading to rupture.

- Bypass valve in place

(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

[Type text] equipment.

MORE OF

MORE FLOW

(7) Empty tank/leak in tank/LSL fails

As for (1) to (6)

- Level alarm on tank.

(8) Heat exchanger blockage

As for (1) to (7)

-

(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 Same as (9)

- Electrically traced line for preventing solidification - FRC on line

Same as (9)

- Valves fail closed - Pressure controller on reactor -

(10) FRC gives incorrect value (too low) (11) Valve failure

LESS OF

LESS FLOW

(12) Lower pressure in reactor

Same as (9)

(13) FRC gives incorrect value (too high)

- Less reaction - Higher DEA outlet temperature from heat exchanger - Insufficient reactor pressure - Potential higher flow in other

-

inspection of lines to look for leaks. (g) Use flow controllers on all lines with the potential to leak. (h) Ensure regular inspection of tank for leakage. (g) Ensure good heat exchanger cleaning and inspect after cleaning. (h) Use a locking off procedure for pump not in use. (g) Surge meter to prevent pump overpressure (i) Check FRC regularly (j) Design valve for maximum pressure Covered by (a) to (j)

Covered by (a) to (j)

[Type text]

(14) Partial blockage/leak in pipe (15) Pump underpowered

(16) High reactor pressure

(17) Valve stuck partially closed (18) Fouling in pipes and heat exchanger

REVERSE

MORE OF

REVERSE FLOW

MORE PRESSURE

(19) Insufficient DEA in tank (20) High reactor pressure (21) Reactor isolation valve fails open

(22) Pump overpower (23) PIC gives wrong value (too low) (24) Thermal expansion of DEA due to heat

sections of line possibly leading to pipe rupture Same as (1), (6) and (13) Same as (13) - Backflow of nitrogen into DEA line Same as (13) - Reactor vessel rupture

Same as (13) Same as (13) - Reduces heat transfer which could lead to DEA solidifying Same as (13) - Potential cavitation in pump As previously discussed - Backflow of reactor contents (including hydrogen) to DEA line

Discussed previously -

- Relief valve for reactor - Pressure controller on reactor - Valves should fail closed -

- Level alarm on tank Reactor pressure control -

Covered by (a) to (j) (k) Fit non return valve to reactor inlet. Covered by (a) to (k)

Covered by (a) to (k) Covered by (a) to (k)

Covered by (a) to (k) Covered by (a) to (k)

Discussed previously Discussed previously

-

(l) Add FIC to all reactor inlet lines, shut down if backflow into DEA line is detected. Covered by (a) to (l) Covered by (a) to (l)

Discussed previously

Discussed previously

(m) Design pipes for higher pressure and

[Type text]

LESS OF

NONE OF MORE OF

LESS PRESSURE

NO PRESSURE MORE TEMPERATU RE

(25) Steam rate fluctuation to heat exchanger

Discussed previously

- Temperature controller on steam flow

(26) Blockage/ closed valves (27) Pump failure

Discussed previously

(28) PIC gives wrong value (too high) (29) Leakage

Discussed previously

(30) Valves more closed than expected (31) Solid DEA in tank with pump running (32) Excess steam in to heat exchanger

Discussed previously

Discussed previously Discussed previously Discussed previously Discussed previously Discussed previously Discussed previously Discussed previously

(33) Electrical tracing too hot (34) Strong sunlight (35) Tank coil too hot

Discussed previously

Discussed previously

Discussed previously Pipe buckles Discussed previously - Reactant too hot, potential reaction problems - Vaporisation in reactor - Thermal strain in pipes Discussed previously Discussed previously Discussed previously

Discussed previously Discussed previously Discussed previously

expansion Covered by (a) to (m) (n) Consider cascading flow and temperature control for heat exchanger steam Covered by (a) to (n) Covered by (a) to (n) Covered by (a) to (n) Covered by (a) to (n) Covered by (a) to (n) Covered by (a) to (n) Covered by (a) to (n)

Covered by (a) to (n) Covered by (a) to (n) (o) Add temperature control to tank

[Type text] LESS OF

LESS TEMPERATU RE

(36) Insufficient steam in to heat exchanger (37) Tracing failure

Discussed previously - Insufficient reactor pressure Discussed previously

(38) Cold weather

Discussed previously

(39) Tank coil too cold

Discussed previously

START UP

(40) Too fast

SHUT DOWN

(41) Corrosion (42) Some DEA solidifies in line

- Heat exchanger too cold to heat DEA to required temperature Discussed previously

Discussed previously Discussed previously Discussed previously Discussed previously Discussed previously Discussed previously

Covered by (a) to (o) Covered by (a) to (o) Covered by (a) to (o) Covered by (a) to (o) Covered by (a) to (o) Covered by (a) to (o)