Control Narrative For HAZOP PDF

**Process Description** ======================= Ammonium Nitrate solution produced by either ANS 1 & 2 at a strength ranging from 90 -- 94% m/m is pumped to tank 5 with the intention of reducing the strength to 87,5 thereafter pumping to Tank Farm for use in Emulsion or ANS sales. The strength of t...

**Process Description** ======================= Ammonium Nitrate solution produced by either ANS 1 & 2 at a strength ranging from 90 -- 94% m/m is pumped to tank 5 with the intention of reducing the strength to 87,5 thereafter pumping to Tank Farm for use in Emulsion or ANS sales. The strength of the ammonium Nitrate solution in the tank is adjusted using weak ammonium nitrate solution dosed into Tank 5. The rate of dosing is controlled by shutoff valve X1 after obtaining feedback from density meter (DT-XXX) installed in Tank 5. The duration in which the shutoff-dosing valve X1 is open is based on a timer to avoid excessive dosing while allowing time for the tank to mix effectively with the weaker ammonium nitrate solution resulting in a uniform mixture. The jet mixer and circulation line currently installed in tank 5 system ensures sufficient agitation of the contents of the tank. **Control Instruments** ======================= +-------------+-------------+-------------+-------------+-------------+ | **Tag \#** | **Descripti | **Function* | **Failure | **Interlock | | | on** | * | Mode** | ** | +=============+=============+=============+=============+=============+ | AE XXX | Density | Measure | Fail Low | None | | | Meter | Ammonium | | | | | | Nitrate | | | | | | Solution | | | | | | Strength in | | | | | | tank 5 | | | +-------------+-------------+-------------+-------------+-------------+ | X 1 | Dosing | Maintaining | Fail Closed | 1. Tank 5 | | | Control | Density set | | High | | | Valve | point set | | Level | | | | by the | | | | | | operator by | | 2. No pump | | | | Dosing weak | | in | | | | Ammonium | | operati | | | | Nitrate | | on | | | | solution | | feedbac | | | | into Tank | | k | | | | 5. | | | | | | | | | | | | *Two modes | | | | | | of | | | | | | operation | | | | | | for the | | | | | | valve | | | | | | namely: | | | | | | Auto and | | | | | | Manual. | | | | | | Preference | | | | | | to be on | | | | | | auto* | | | +-------------+-------------+-------------+-------------+-------------+ **Control Philosophy** ====================== *Tank 5 Ammonium Nitrate Strength Control* **Parameter** **Set point** **Control** **Input Variable to Control** --------------- --------------- ------------------------------------------------------ ------------------------------- Concentration 87,5% Dosing of Weak Ammonium Nitrate solution (30 -- 50%) Density & Temperature **Control Scenario Planning** ============================= **Scenario** **Response** **Failure to Respond** --------------------------------------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- High Concentration in Tank 5 X1 opens and dosses on a timer before closing with the aim of mitigating against over dosing. Once uniform mixture has been achieved operators can export to Tank Farm Failure of valve results in no dosing of ANSSER solution due to fail close functionality in the valve. There is a manual valve in which operators can open to adjust strength in tank as per current practice. Low Concentration in Tank 5 X1 valve stays closed. Increasing strength procedure as per current operation using ANS 1 & 2 solution to increase strength in tank before exporting to Tank Farm No effect High Level in Tank 5 and Strength is high No dosing to prevent overflow of tank as per interlock on dosing valves Address as per current operations Low level in Tank 5 with low concentration X1 valve stay closed. Increasing strength as per current operation using ANS 1 & 2 solution to increase strength in tank before exporting to Tank Farm No effect Faulty Density Meter ( High Or low concentration) Manual test verification before export to Tank farm None