Difference between revisions of "Reboiler Steam Condensate Pots(HT-1113A/B)"

Revision as of 17:46, 2 July 2018

Purpose

Amine Reboilers Steam condensate pots (HT-1113A/B): The Amine Reboilers Steam condensate Pots (HT-1113A/B): are vertical separators that serve as steam traps (see Figure 6). The accumulators receive the steam condensate draining from the reboilers to prevent the liquid from backlogging in the reboiler tubes. The tubeside accumulation of steam condensate decreases the heat transfer in the reboilers and increases the potential for water hammer damage. Condensate is pushed out of the pot by steam pressure to the LP steam condensate header.

Instrumentation

The Amine Reboilers Steam condensate pots have the following process controls and instrumentation:

• a level gauge glass (LG-1864)
• a local pressure gauge (PI-1863)
• a level transmitter (LIT-1864) that relays to a DCS based level controller (LV-1814). The controller modulates a level control valve to maintain the accumulator at setpoint; the level control valves throttles the flow of condensate pumped from the accumulator.

Operation

The Amine Reboilers Steam condensate pots are equipped with the following flowlines and valving:

• A steam outlet off of the top of the Condensing pot that sends flash steam back to the reboiler
• Outlet line to the Reboiler lean Amine outlet, this line is equipped with a manual drain and is used to add water make to the process train. This line has an orifice plate (FE-1821) that transmits water flow to the DCS, so the CRO can see if water make up is flowing.
• Outlet line to the LP steam condensate header
• A pressure gauge (PG-1846A/B) locally indicates the pressure of incoming 65# steam

Additional Lines and Valves

The Amine Reboilers Steam condensate Pots (HT-1113A/B) are each equipped with:

• A pressure relief valve (PRV-1865) set at 150 psig. The PSV relieves to atmosphere.
• A 2” manual amine drain valve

Operations Monitoring

During monitoring rounds at the Amine Reboilers Steam condensate pots, the Area Operator:

• ensures that each condensate Pots steam flow control valve is in service
• ensures that lean amine is draining correctly from the reboiler’s drawoff section to the still’s bottom section (LG-1819)
• ensures the levels in the reboiler condensate Pots are equal

The Amine Reboilers are major consumers of FNNPF’s 65# steam. Therefore, the start-up of a reboiler is a coordinated task between the CRO and the Area Operator to maintain stable steam pressures and prevent fluctuation in the steam demand. During train start-up, the Area Operator must open the reboilers’ 65# steam valves slowly, so that the reboilers begin to generate stripping steam:

• rapid addition of steam to the reboilers may result in rapid regeneration of large volumes of steam that will surge into the regenerator and cause tray damage
• rapid addition of steam to cold piping can trigger severe water hammer impact damage.

Warning! The incorrect, hasty start-up of piping or equipment causes a hazardous situation known as condensation-induced water hammer. Condensation-induced water hammer occurs if condensate forms in steam piping:

• when ambient cooling causes condensate to from in a steam pipe, the newly-formed liquid suddenly occupies much less volume than the former steam, and a low-pressure void is created
• steam accelerates to extreme speed as it races to fill the void. At this extreme speed, the steam may sweep settled condensate along to form a liquid condensate slug that fills the pipe’s cross-section. The fast-moving steam behind the slug will hurl the slug down the pipe at extreme speed.
• the high-speed condensate slug will impact any downstream obstruction (such as an elbow or closed valve) with enough force to rupture the steam pipe. Fractured pipe debris and ejection of steam can harm nearby personnel.