PETROLEUM PLANT UTILITIES

o          Fuel Gas System

The primary source of fuel gas will be downstream of the expander compressor. For start-up purposes fuel gas will be taken from the two feed gas lines upstream of plant isolating valves and will tie-in to the main fuel-gas header upstream of the FG scrubber.

An orifice type meter shall be installed to measure overall plant gas consumption, which covers but is not necessary limited to, the following:

•           Fuel gas for gas turbine driven compressors and gas engine generators

•           Fuel gas for hot oil furnace heater

•           Purge gas

•           Pilot gas for flare and burn-pit ignition system

The Fuel Gas Package will comprise of the following:

•           Fuel Gas Scrubber (1 x 100 %)

•           Fuel Gas Filters (2 x 100 %)

•           Fuel Gas Heater (1 x 100 %)

The fuel gas off take is at 285 psig before let down into the fuel gas scrubber. The gas is totally dry for star-up, the gas taken from the pipelines will be water-saturated, so a fuel-gas heater is provided to elevate the gas temperatures.

o          Seal Gas System

The system will be designed and supplied by the selected Compressor VENDOR.

The seal gas system shall be able to handle the primary seal gas requirement of the selected gas compressors.

The Seal Gas Package might comprise of the following:

•           Seal Gas Scrubber (1 x 100 %)

•           Seal Gas Filter/Coalesces (2 x 100% )

•           Seal Gas Electrical Heaters (2 x 100%)

In addition, seal gas treatment and its control system shall be provided on the compressor skids.

o          Flare and Vent Systems

All hydrocarbon pressure relieving devices, with the exception of low temperature extraction section gases, will discharge to the high pressure flare header. This includes PSVs, rupture disks if approved for use, and emergency blowdown valves. To prevent any liquid entering the flare stack, a flare K.O. drum, and liquid removal pumps will be required. Downstream of the KO drum a water seal-drum shall be provided to prevent air from entering the flare header system.

The Flare Capacity shall be based on a worst-case scenario. The design shall be completed in detail engineering.

A flare header designed for the maximum plant throughput will pass 250 MMscfd under blocked outlet condition. The emergency blowdown rate will quickly reduce to below the normal maximum throughput of 250 MMscfd and is not the controlling case. If adequate protection against blocked discharge and failure of the protective systems cannot be economically achieved relative to the cost of a larger capacity flare system the system shall be sized for the maximum throughput. It is anticipated that an elevated flare system will be used.

In order to reduce the header size a maximum Mach number of 0.7 may be used for emergency discharge assuming the use of a conventional pipe flare. Consideration is also to be given to the use of a sonic flare tip operating at an elevated back pressure (approximately 30-50 psig at the tip inlet) which will considerably reduce radiation levels at and around the plant.

In addition to the HP flare a cold vent line shall be installed, which will be elevated and suspended from the HP flare stack. Some of the relief valve discharges and vents in the unit are at a very cold temperature and cannot be sent to the wet carbon steel flare system. These cold discharges would cause the formation of ice and hydrates with potential blockage of the free path to the flare. The cold temperature of these discharges are also too cold for the use of carbon steel material in the piping and flare. Therefore a separate cold flare system consisting of a stainless steel, (or other material suitable for the discharge condition), flare header shall be provided. Simulation indicates that cold liquid will not condense out during discharge, so a KO drum has not been indicated for the cold vent system. Bidders to confirm this fact or advise the installation of a SS KO-drum. Use of this separate line for the relatively low pressure De-C2 discharge allows a higher back pressure in the CS HP flare header thus reducing header size.

The radiation levels for personnel and equipment at the limit of the restriction zone resulting from the HP Flare shall not be more than the following:

(ref: API 520 Part II - Sizing, Selection and Installation of Pressure-Relieving Devices in Refineries):

•           Equipment Protection    5000     Btu / (hr.ft2)

•           Personnel, one minute exposure            1500     Btu / (hr.ft2)

•           Personnel, continuous exposure            500       Btu / (hr.ft2)

Liquids collecting in the Flare K.O. Drum are to be directed via the Flare K.O. pump to the Closed Drain Drum. The requirement for sizing of these pumps is removal of all liquid between LLH and LLL in 30 minutes.

The water seal drum will have a permanent water-line connection, level controlled to maintain a position seal in the drum. A water seal drum is not envisaged for the cold vent. This cold vent line will be fuel-gas purged only from its extreme upstream point. 

The flare system will comprise of:

•           HP flare header

•           HP flare stack

•           Cold vent header

•           HP flare tip

•           Flare ignition system

•           HP flare KO drum

•           HP flare KO drum pump

•           HP water seal drum

Individual atmospheric vents are to be used where possible with crossovers minimized and air-cooled exchanger fans used to assist dispersion. Flame arrestors shall be fitted at individual local atmospheric vents.

o          Instrument and Utility Air System

The Instrument and Utility Air System will comprise the following main components:

•           Instrument / Utility Air Compressors (2 x 100 %)

•           Instrument Air Drier (2 x 100 %)

•           Instrument / Air Receiver

•           Utility Air Receiver

•           Instrument and Utility Air Distribution Systems

Air Compressors and Air Dryers capacity is shown in Table-4.

The air receiver shall be sized for 30 minutes of air capacity from low pressure alarm down to low low pressure shutdown initiation.

o          Diesel Fuel System

The diesel storage facility with filter coalesces; loading facilities and transfer are to be provided. The storage tank shall be designed to accommodate the diesel fuel demand of diesel generator for 8 days in base load continuous operation condition, supply the diesel fire pumps and provide fuel for vehicle use through a day tank and vehicle fill hose.

The Diesel Fuel system comprises of:

•           Diesel Fuel Storage Tank

•           Diesel Fuel Daily Tank with fill hose

•           Diesel Fuel Loading Pump

•           Diesel Fuel Transfer Pump

•           Diesel Fuel Transfer Filter

OPEN AND CLOSED DRAINS SYSTEM

The drain system design is based on segregated systems, described below.

The Open Non-Hazardous Drainage System provide drainage for locations that are designated non-hazardous. This system is segregated from all other open or closed drain systems.

Non-hazardous areas generally include storage vessel areas for utility materials such as lubricating oil, diesel fuel, etc. The drain system from these areas, referred to as the Open Non-Hazardous Drains (ONHD), handles fluids collected from open drip pans, tundishes and floors in non-hazardous areas.

Discharge of the ONHD to the system shall be by open galleys for the floor drains and a tundish type system for equipment maintenance drains. The disposal stream is discharged into the API Separator 1 Skimmer. The hydrocarbons settling out in the Separator / Skimmer will be pumped to burn pit for final disposal.

The Open Hazardous Drainage System provides drainage for areas that are designated hazardous. These generally include all process areas and locations where hydrocarbons are present in significant quantities. The drains system from these areas, referred to as the Open Hazardous Drains (OHD), handles fluids collected from open drip pans, tundishes and floors in hazardous areas. The open drain system must only be used for draining hydrocarbon fluids from process vessels after preparation for maintenance (depressurization).

The OHD streams are collected and routed to the API Separator Skimmer by a separate channel. Collected hydrocarbons are pumped to burn pit for final disposal.

Water from open drain system will be directed to the API separator / skimmer and then disposed to the river. The design of the water handling system as minimum it will comprise:

·         API Separator / Skimmer

·         1 x oily water pump

The Closed Drain System (CD) consists of a permanent pipe work connection and collection header for routing drained liquids to a vented closed drain drum. It handles hazardous fluids from process vessels, keeping them out of contact with the atmosphere.

The Closed Drain Drum is designed with sufficient volume to receive the drained fluids and to permit vapor disengagement. A safety margin is applied to cover additional volumes, which may be drained. A high level alarm is installed to prevent overfilling. The drum shall have a minimum design pressure of 100 psig (eliminating the risk of rupture in the event of a deflagration). The vent is sized to discharge the highest vapor flow that could enter the drum if gas blow by should occur.

The sizing requirement for the closed drain drum pumps is the removal of all liquids between LLH and LLL in 30 minutes to the API Separator/Skimmer.

Overview of drain system:

The Closed Drain System shall be designed to receive and degas the maximum expected production of raw condensate and oil from the various sources, and will consist of:

·         1 off - closed drain drum

·         2 off -100 % closed drain drum pumps & motors

DESIGN TEMPERATURE PHILOSOPHY

The design temperature shall be based on the maximum operating temperature plus a minimum margin of 20°F.  For equipment operating at ambient conditions, the upper design temperature shall be at least equal to a maximum black bulb temperature of 160°F unless it is insulated or other corrective action is taken.  Fire conditions will not be considered in establishing the design temperature of a vessel.

For process coolers, consideration should be given to designing downstream equipment for the upstream design condition. Reliance on devices such as temperature trips to protect downstream equipment in the event of cooling failure may introduce risk, as the instrument response time may not be sufficiently rapid to offer adequate protection. This will be reviewed on a case by case basis.

Compressor Suction Scrubbers

Compressor suction scrubber design temperatures are defined as the highest of the following:

a)     Maximum operating temperature at the compressor suction in the event of air cooler failure.

b)    Maximum recycle temperature (discharge minus JT drop across anti-surge valve) in the event of air cooling failure.

c)     Maximum normal operating temperature plus 50°F.

Compressor Discharge

Maximum operating temperature on compressor discharge will be defined as 20°F above the predicted maximum normal operating temperature to allow for lower efficiency at off-design operation.  The maximum discharge temperature shall be confirmed by the compressor vendor.

Shell and Tube Heat Exchanger

For shell and tube heat exchangers, whenever the shell side fluid is hotter than the tube side fluid, the design temperature on the tube side shall be made equal to the shell side design temperature.

Over Pressure Protection Requirements

Protection of equipment against overpressure and other excessive operating conditions shall be in accordance with API RP 14C (Basic Safety System), API RP 520 (Pressure Relieving Systems) and API RP 521 (Pressure Relief and Depressuring Systems).

INSTRUMENT CONTROL VALVES

1.1          Control Valves

Control valves shall be installed with the actuator in the vertical position on a horizontal line. Control valves shall be installed so that they are readily accessible from grade or platforms.  Wherever possible, they should be located at grade for ease of maintenance. Clearance shall be provided above and below a control valve so that the bottom flange and plug or the actuator and plug may be removed with the valve body in the pipeline.  Sufficient clearance shall also be provided for valve removal.

1.2          Shutdown/ Blowdown Valves

All actuated ball valves shall be of the 90º rotation type and be complete with all necessary controls mounted on the valve. Actuator types shall be Pneumatic Spring Return. The valve stem orientation shall be as stated on the data sheet. Correct operation of the valve shall not be affected by the position of the valve or actuator.

1.3          Pressure Relief Valves

All pressure relieving devices shall be sized in strict accordance with applicable local, state, and national code requirements. Safety relief valves shall be sized by calculating ASME areas required for the most severe relieving case and shall follow the ASME requirements. Nomenclature and formulas used shall be according to API RP 520. Valve selection and installation shall be based on API RP 520, Part I and Part II.  Closed relief valve discharge systems shall be designed in accordance with API RP 521.