API 16D BOP Koomey Unit: Selection, Replacement and Buying Guide
An API 16D BOP Koomey Unit stores and supplies the hydraulic energy needed to operate blowout preventers and related drilling well control equipment.
Depending on local terminology, the same type of equipment may be called a BOP control unit, BOP accumulator unit, BOP closing unit, Koomey accumulator, oilfield accumulator unit or hydraulic BOP control system.
These terms are often used interchangeably in the field. The actual equipment, however, is not one-size-fits-all.
A compact closing unit for a mobile land rig may control only a few hydraulic functions. A deep drilling rig may require several isolated accumulator banks, redundant charging pumps, multiple remote control stations, a blind shear boost circuit and hazardous-area electrical equipment.
Reservoir capacity and accumulator bottle count are therefore only part of the selection process. The final configuration also depends on verified BOP operator volumes, the approved operating sequence, pressure settings, charging performance, rig utilities, remote control requirements and installation environment.
SGPE supplies project-specific BOP control systems for drilling projects that reference applicable API 16D requirements. Before recommending a configuration, the engineering team reviews the hydraulic demand, charging pumps, accumulator arrangement, remote controls and equipment interfaces.
This guide explains how an API 16D BOP Koomey Unit works, how to select the correct configuration and how to compare supplier proposals. It also covers legacy Koomey Unit replacement, drilling rig retrofit projects, compatibility checks, factory acceptance testing, pricing factors and quotation preparation.
Quick Answer: What Should You Check Before Buying?
Before purchasing a BOP Koomey Unit, confirm the complete BOP stack and list every hydraulic function the control system must operate.
You will also need the opening and closing volumes of each BOP operator, the approved emergency sequence, minimum final pressure, rig voltage, available compressed air, remote panel requirements, hose lengths and environmental conditions.
When comparing proposals, do not rely only on reservoir capacity or accumulator bottle count. Compare the calculated usable hydraulic volume, charging pump performance, control function schedule, remote panel scope, FAT requirements and documentation package.
For a replacement project, the proposed unit must also match the existing hydraulic, electrical, pneumatic and mechanical interfaces.
API 16D BOP Koomey Unit at a Glance
| Item | Typical Project Requirement |
|---|---|
| Main purpose | Store and distribute hydraulic energy for BOP operation |
| Controlled equipment | Annular BOPs, ram BOPs, choke-line and kill-line valves, and diverter functions |
| Main components | Reservoir, accumulator bottles, charging pumps, control manifold, regulators, gauges and remote panels |
| Installation options | Skid-mounted, trailer-mounted or containerized |
| Pump options | Electric, air-driven, diesel-driven or combined |
| Remote controls | Pneumatic, hardwired electrical, PLC or touchscreen |
| Main applications | Land drilling, offshore surface BOP systems, rig upgrades and selected workover projects |
| Key sizing inputs | Operator volumes, pressure settings, operating sequence and temperature |
| Main performance test | Accumulator drawdown test |
| Main purchasing risk | Comparing bottle count without checking usable hydraulic volume |
| SGPE project scope | New-build, replacement, retrofit and interface-matched systems |
What Is an API 16D BOP Koomey Unit?
An API 16D BOP Koomey Unit is a surface hydraulic control system used with drilling well control equipment.
It stores pressurized hydraulic fluid and directs that fluid to the selected BOP operator when the crew activates a control function.
Depending on the approved BOP stack, one control unit may operate an annular BOP, pipe rams, variable bore rams, blind rams, blind shear rams and hydraulic choke-line or kill-line valves. The system may also control a diverter, hydraulic connector or another project-specific auxiliary function.
A complete BOP control unit normally includes a hydraulic reservoir, nitrogen-charged accumulator bottles, charging pumps, pressure regulators, directional valves, gauges, transmitters and alarms.
Local and remote panels allow the drilling crew to operate the required functions from approved positions around the rig.
The charging pumps draw control fluid from the reservoir and transfer it into the accumulator bottles. As hydraulic fluid enters each bottle, it compresses the nitrogen and stores energy.
When a function is selected, the control manifold sends fluid to the correct hydraulic chamber. The accumulators provide immediate flow, while the charging pumps restore system pressure after the operation.
This stored-energy arrangement allows the BOP control system to respond more quickly than a hydraulic power pack that depends only on pump output.
What Does “Koomey Unit” Mean in the Oilfield?
“Koomey Unit” is widely used in drilling operations as a field term for a BOP accumulator or closing unit. However, Koomey may also refer to a specific branded product line.
The actual requirement should therefore be defined before a quotation is requested.
One project may need an original OEM control unit or original replacement parts. Another may require an independently manufactured BOP closing system that replaces an older unit while matching its existing interfaces.
Rig owners may also use a replacement project to modernize the control system. Existing skid locations or hydraulic connections can sometimes remain in place while obsolete pumps, regulators, gauges, pneumatic controls or remote panels are replaced.
An independent supplier should describe this equipment accurately as a replacement BOP control unit, replacement BOP accumulator unit or retrofit BOP closing system engineered around the applicable API 16D project requirements.
An independently manufactured system should not be presented as an original OEM product without authorization.
For a Koomey Unit replacement proposal, SGPE can review equipment photographs, nameplates, hydraulic schematics, remote panel arrangements and skid dimensions. Completing this review before manufacturing reduces the risk of incorrect assumptions about interchangeability, installation work, spare parts and control logic.
API 16D Scope and Application Boundaries
API Specification 16D addresses control systems for drilling well control equipment and diverter equipment.
Typical applications include onshore drilling rigs, offshore surface BOP systems, new-build drilling packages, diverter control packages, rig refurbishment projects and replacement of existing drilling BOP control units.
Selected workover projects may also specify an API 16D control system when they use drilling-type BOP equipment and similar operating arrangements.
Hydraulic accumulator systems are used with other pressure-control packages as well. However, API 16D should not automatically be treated as the only applicable standard for every coiled tubing, snubbing, hydraulic workover or wireline application.
Each operation may involve different equipment, response requirements and control logic. The technical basis must therefore be confirmed from the actual pressure-control package and project specification.
For broader control-system information, buyers can also review the API 16D BOP Control Unit and API 16D BOP Accumulator Unit pages.
Why Usable Accumulator Volume Matters
A blowout preventer cannot perform its intended function without enough hydraulic pressure and fluid volume.
The BOP may have the correct bore size, pressure rating and ram configuration. Its hydraulic operator still requires enough fluid to open or close within the specified time.
During a well control event, the crew may need to close an annular BOP, close a pipe ram and operate a choke-line valve. Another emergency sequence may require blind shear ram activation followed by an additional critical function.
The BOP control unit must complete the approved sequence while maintaining the specified minimum pressure.
An undersized or poorly maintained accumulator system may cause slow BOP response, insufficient closing force, low usable volume or excessive pump recovery time. Other warning signs include unstable annular pressure, frequent pump cycling and delayed remote panel response.
In a serious case, the system may fail to complete the required operating sequence.
For this reason, the accumulator package should be evaluated together with the BOP stack, API 16C Choke Manifold, API 16C Kill Manifold, hydraulic valves and approved well control procedures.
Reservoir size alone does not prove that the system has enough emergency operating capacity. The engineering calculation must focus on the usable hydraulic volume available between the selected pressure limits.
How Does a BOP Koomey Unit Work?
The operating process begins at the hydraulic reservoir.
Electric or air-driven pumps draw clean control fluid from the reservoir and send it into the high-pressure accumulator section.
Each accumulator bottle contains a nitrogen section and a hydraulic fluid section. A bladder or another suitable separating element prevents nitrogen from mixing with the control fluid.
As the pump transfers fluid into the bottle, the nitrogen compresses and stores energy. The pump stops or unloads when the system reaches its upper pressure setting. It starts again after the pressure falls to the lower setting.
The control manifold regulates and distributes pressure to each BOP function.
The annular BOP normally receives adjustable pressure so that the crew can control the force applied to the packing element. Ram BOPs and hydraulic valves may operate from another regulated pressure circuit.
A blind shear ram may require a dedicated boost circuit when normal manifold pressure cannot generate the required shearing force.
When the operator selects “close,” the directional valve sends fluid to the closing chamber while fluid from the opposite chamber returns to the reservoir. Selecting “open” reverses the flow.
The accumulator bottles provide the immediate hydraulic volume. Meanwhile, the charging pumps restore system pressure for the next operation.
Typical BOP Control Unit Technical Parameters
The figures below are common engineering references for surface BOP control systems. They do not define one mandatory API 16D configuration.
Final values must follow the approved sizing calculation, verified BOP operator data and project specification.
| Technical Parameter | Common Reference Value | Selection Note |
| Maximum accumulator pressure | Commonly up to 3,000 psi / 20.7 MPa | Confirm against the approved hydraulic design |
| Typical manifold pressure | Often around 1,500 psi / 10.3 MPa | Match the ram BOP and hydraulic valve operators |
| Typical annular pressure range | Adjustable, often up to approximately 1,500 psi / 10.3 MPa | Follow the annular BOP manufacturer’s recommendation |
| Typical nitrogen precharge | Often around 1,000 psi / 6.9 MPa at reference temperature | Temperature and system design affect the setting |
| Pump-start pressure | Project-defined below maximum storage pressure | Coordinate with the usable-volume calculation |
| Pump-stop pressure | Normally near the selected maximum pressure | Confirm during FAT |
| Number of control functions | Commonly 4 to 20 or more | Match the complete BOP stack |
| Remote control stations | Commonly 1 to 3 or more | Depends on rig layout and operating philosophy |
| Electric power supply | Often 380–480 V, 50/60 Hz, three-phase | Confirm the actual rig supply |
| Pneumatic supply | Commonly around 90–125 psi / 0.62–0.86 MPa | Check both pressure and available airflow |
| Ambient temperature | Commonly around −20°C to +50°C before customization | Add winterization or high-temperature protection when required |
| Installation type | Skid, trailer or container | Select according to mobility and environment |
Main Components of a BOP Control Unit
Hydraulic Reservoir
The reservoir stores the control fluid and receives fluid returning from the BOP operators.
A suitable reservoir provides enough capacity for the complete hydraulic circuit. It also leaves room for fluid expansion, air separation, sediment collection and routine maintenance.
Typical equipment includes a level indicator, filling and drain connections, an inspection cover, suction and return ports, a breather and filters. Depending on the project, the reservoir may also include a low-level alarm, temperature indicator or heater connection.
Reservoir capacity does not equal usable accumulator volume. A large tank cannot compensate for an undersized accumulator bank, incorrect nitrogen precharge or insufficient charging performance.
Accumulator Bottles and Banks
Accumulator bottles store the hydraulic energy required for rapid BOP operation.
Bottle quantity cannot be selected from nominal capacity alone. A proper sizing review also considers nitrogen precharge, maximum storage pressure, pump-start pressure, minimum final pressure, operating temperature and the required emergency sequence.
Most importantly, the calculation must include the verified opening and closing volumes of every controlled BOP and hydraulic valve.
The bottles are normally arranged in practical banks with isolation valves, check valves and pressure protection. This layout improves maintenance access and limits the effect of one accumulator becoming unavailable.
Electric Charging Pumps
Electric pumps provide stable charging for many land drilling rigs, offshore surface systems and fixed installations.
A typical package includes a motor, hydraulic pump, coupling, mechanical guard, suction strainer, check valve, relief valve, isolation valve and pressure switch. A starter, motor protection and local controls may also be included.
Before selecting the pump, confirm the rig voltage, frequency, phase and hazardous-area classification. Motor enclosure, starting method and cable-entry requirements must also match the project.
A proposal that states only “electric pump included” does not provide enough information for technical comparison.
Air-Driven Charging Pumps
Air-driven pumps provide an independent charging source when the rig has sufficient compressed air.
Many land drilling systems use electric pumps for normal charging and pneumatic pumps as backup. The air-driven pumps still need adequate inlet pressure and airflow to achieve the specified output.
The RFQ should identify the normal and minimum rig air pressure, available airflow, compressor capacity, connection size and air quality.
Clean, dry air helps protect pneumatic equipment. Moisture, contamination or insufficient pressure may reduce charging performance and shorten component life.
Hydraulic Control Manifold
The control manifold distributes hydraulic fluid to each controlled function.
A typical manifold includes directional valves, regulators, gauges, check valves, relief valves, isolation valves, bleed valves and hydraulic outlets.
Clear labels should identify every function. Depending on the BOP stack, the panel may show Annular BOP, Upper Pipe Ram, Lower Pipe Ram, Variable Bore Ram, Blind Shear Ram, Choke-Line Valve and Kill-Line Valve.
The final arrangement must match the approved hydraulic schematic and actual BOP stack.
Pressure Regulators and Boost Circuits
The annular regulator controls the pressure supplied to the annular BOP. Excessive pressure may accelerate packing element wear and affect stripping performance.
Ram BOPs and hydraulic valves may operate from another regulated circuit. A blind shear ram may also require a dedicated pressure boost system.
The required boost pressure must be checked against the BOP operator design and the pipe or casing the ram is expected to shear.
Gauges, Transmitters and Alarms
The control unit should clearly indicate accumulator, manifold, annular, pump discharge and rig air pressure.
Standard land systems often use mechanical gauges. Modern rigs may also require electronic transmitters connected to a PLC, touchscreen or rig data system.
The alarm package may monitor low accumulator pressure, low reservoir level, low rig air pressure, pump failure, high fluid temperature, power failure or communication loss.
Local and Remote Control Panels
The main panel allows the crew to operate the BOP functions at the accumulator unit. Remote panels provide control from the driller’s position, toolpusher’s office or another approved location.
A conventional rig may use pneumatic remote panels. A modern rig may use hardwired controls, PLC push-button stations or touchscreen panels with pressure displays, alarms and event recording.
Critical functions, especially blind shear ram activation, may need protective covers, two-step operation or project-specific interlocks.
The remote control system can be configured around the rig layout, required indications, operating philosophy and communication method.
Hydraulic Hoses and Connections
Hydraulic hoses and tubing connect the BOP closing unit to the surface BOP stack.
The hose package must be selected for working pressure, test pressure, line length, pressure loss, temperature range, fire resistance, fitting type, bend radius and mechanical protection.
Long or restricted lines can slow BOP response. Incorrect connections or hose exit directions may also delay installation.
The RFQ should state the distance between the control unit and BOP stack, together with the planned routing and required interfaces.
Matched API 16D BOP Control Hoses and fittings can be included when accurate connection and length information is available.
Typical System Configurations
| Configuration Factor | Typical Options |
| Installation | Skid-mounted, trailer-mounted or containerized |
| Charging pumps | Electric, pneumatic, diesel-driven or combined |
| Control functions | Annular BOP, ram BOPs, hydraulic valves, diverter and auxiliaries |
| Remote control | Pneumatic panel, hardwired panel, PLC panel or touchscreen |
| Accumulator arrangement | Single or multiple isolated banks |
| Environmental package | Standard land, desert, winterized or offshore |
| Monitoring | Gauges, transmitters, alarms and event logging |
| Special functions | Blind shear boost, emergency control and remote shutdown |
A compact land drilling system may combine one electric pump, two air-driven pumps, several accumulator bottles and four to eight controlled functions.
A larger deep-drilling package may use multiple accumulator banks, dual electric pumps, pneumatic backup pumps and more than ten functions. It may also include several remote stations, redundant transmitters, blind shear boost pressure and hazardous-area electrical equipment.
Two systems with the same reservoir size can still provide different usable volumes and charging performance. The complete technical scope is therefore more important than one headline parameter.
API 16D BOP Koomey Unit Applications
| Application | Main Configuration Priorities |
| Conventional land drilling rig | Skid-mounted system, electric and pneumatic pumps, pneumatic driller’s panel |
| Mobile workover rig | Compact skid or trailer, fewer functions and quick rig-up hose package |
| Deep drilling rig | Larger usable volume, multiple pumps, blind shear boost and additional alarms |
| Offshore surface BOP system | Marine coating, stainless tubing, hazardous-area components and offshore lifting |
| Desert drilling project | Sunshade, dust protection, high-temperature seals and improved filtration |
| Cold-climate drilling | Reservoir heaters, low-temperature fluid, insulated lines and heated enclosure |
| Rig refurbishment | Interface survey, replacement pumps, upgraded controls and revised drawings |
| New-build drilling package | Integrated BOP stack, control system, remote panels, hoses and documentation |
Land Drilling Rigs
Land rigs may use skid-mounted, trailer-mounted or containerized systems.
A fixed rig may need a standard skid with electric and pneumatic charging pumps. A mobile unit may benefit from a trailer-mounted package and quick-connect hose arrangement.
The proposal should reflect the available installation space, electrical supply, compressed-air capacity, controlled functions and remote panel locations.
Deep Drilling and Large BOP Stacks
A deep drilling rig may use several ram cavities and multiple hydraulic valves.
This arrangement can require more usable accumulator volume, higher charging capacity, several remote stations and a blind shear boost circuit.
The system must be sized from verified operator volumes and the approved sequence. Drilling depth alone does not determine accumulator capacity.
Offshore Surface BOP Systems
Offshore applications may require marine corrosion protection, stainless steel control tubing, fire-resistant hydraulic hoses and hazardous-area electrical equipment.
Limited platform space may also require a compact layout and carefully planned maintenance access.
The proposal should reflect the coating system, tubing material, electrical classification and lifting criteria.
Desert and High-Temperature Drilling
Desert rigs expose control equipment to heat, dust, sand and direct sunlight.
A suitable package may include sunshades, high-temperature seals, protected air intakes, improved filtration and hydraulic fluid temperature monitoring.
Rapid temperature changes between day and night should also be considered.
Winterized and Cold-Climate Drilling
Low temperatures increase hydraulic fluid viscosity and may reduce seal flexibility.
A winterized package may require reservoir heaters, heated enclosures, low-temperature hydraulic fluid, cold-resistant seals and insulated lines.
Transport, storage, cold startup and normal operating conditions should all be included in the review.
Rig Upgrades and Brownfield Projects
Older drilling rigs may use pumps, regulators, gauges or remote panels that no longer match current operating requirements.
A retrofit may add accumulator capacity, replace charging pumps, install new regulators or convert pneumatic controls to PLC operation.
Pressure transmitters, alarms, event recording, new hoses and updated hydraulic drawings may also form part of the upgrade.
This replacement and modernization requirement is the main difference between a general BOP control unit page and a Koomey Unit buying guide.
API 16D BOP Koomey Unit Selection Guide
Step 1: Define the Application
Begin with the rig type, BOP stack and operating environment.
Confirm whether the unit will serve a conventional land rig, deep drilling rig, offshore surface BOP system, mobile workover rig, new-build package or existing rig retrofit.
This decision affects the installation layout, pump redundancy, remote control method and environmental protection.
Step 2: List Every Controlled Function
A request for “one complete BOP control unit” does not provide enough information for sizing.
Each hydraulic function should be listed separately.
| Controlled Item | Quantity | Opening Volume | Closing Volume | Required Pressure |
| Annular BOP | Project-defined | Manufacturer data | Manufacturer data | Manufacturer data |
| Upper pipe ram | Project-defined | Manufacturer data | Manufacturer data | Manufacturer data |
| Lower pipe or variable bore ram | Project-defined | Manufacturer data | Manufacturer data | Manufacturer data |
| Blind shear ram | Project-defined | Manufacturer data | Manufacturer data | Manufacturer data |
| Choke-line valve | Project-defined | Manufacturer data | Manufacturer data | Manufacturer data |
| Kill-line valve | Project-defined | Manufacturer data | Manufacturer data | Manufacturer data |
This function schedule determines the number of manifold valves and remote controls.
Step 3: Collect Verified Operator Data
Two BOPs with the same bore size may use different hydraulic operators and fluid volumes.
For each controlled item, provide the manufacturer, model, bore size, working pressure, opening volume, closing volume and required control pressure.
| Required Information | Example |
| Equipment | Annular BOP |
| Manufacturer | To be confirmed |
| Model | To be confirmed |
| Bore size | 13-5/8 in |
| Working pressure | 5,000 psi |
| Opening volume | Manufacturer data |
| Closing volume | Manufacturer data |
| Required pressure | Manufacturer data |
| Locking arrangement | If applicable |
| Special requirement | Stripping or emergency closure |
When original data is unavailable, drawings, manuals, nameplates or dimensional information may be needed before the design can be confirmed.
Step 4: Define the Operating Sequence
Accumulator sizing depends on the operations the unit must complete before pressure falls below the permitted limit.
One project may require the system to close the annular BOP, close a pipe ram, operate a choke-line valve and activate a blind shear ram. Another project may use a different sequence.
The drilling contractor or end user must define the approved sequence. It should not be assumed by the control unit supplier.
Step 5: Confirm the Pressure Basis
The design basis should identify the nitrogen precharge, pump-start pressure, pump-stop pressure, maximum accumulator pressure and minimum final pressure.
It should also define the annular control pressure, ram BOP control pressure and any blind shear boost requirement.
These values directly affect the calculated usable volume.
Step 6: Select the Pump Arrangement
| Pump Arrangement | Typical Application | Main Advantage |
| One electric plus two air-driven pumps | Conventional land rig | Practical primary and backup arrangement |
| Two electric plus two air-driven pumps | Larger land or deep drilling rig | Higher charging capacity and redundancy |
| Dual electric pumps | Rig with reliable electrical power | Simple operation and strong charging performance |
| Electric plus diesel-driven pump | Remote or special project | Independent mechanical backup |
| Customized multi-pump package | Offshore or critical application | Project-specific redundancy |
Confirm the electrical supply, rig air capacity, required recovery time and backup philosophy before selecting the pumps.
Step 7: Select the Remote Control System
| Remote Panel Type | Typical Use | Main Characteristics |
| Pneumatic driller’s panel | Conventional land rigs | Simple and compatible with rig air |
| Pneumatic toolpusher’s panel | Secondary control station | Provides additional remote access |
| Hardwired electrical panel | Fixed rig applications | Direct control with clear indications |
| PLC push-button panel | Modern drilling rigs | Logic, alarms and system integration |
| Touchscreen panel | Advanced drilling package | Pressure displays, event logging and diagnostics |
The project should define the number and location of remote stations, functions available at each panel, required pressure displays and communication method.
Suitable protection against accidental activation of critical functions should also be specified.
Step 8: Confirm Environment, Layout and Documentation
The project specification should state the ambient temperature, humidity, altitude, hazardous-area classification and exposure to dust, salt spray, snow or direct sunlight.
It should also define the maximum skid dimensions, lifting requirements, hose exit direction and maintenance-clearance limits.
Finally, the RFQ should identify the required FAT, third-party inspection and document package.
Koomey Unit Replacement and Retrofit Guide
Replacing an older BOP control system requires more than matching the reservoir size or skid footprint.
The new unit must suit the current BOP stack, hydraulic demand, rig utilities and operating philosophy. It must also connect correctly to the existing hoses, pilot lines, remote stations and power supplies.
Replacement Survey Information
| Survey Item | Information to Record |
| Existing skid | Dimensions, weight, lifting points and maintenance access |
| Accumulator section | Bottle size, quantity, banks and pressure settings |
| Charging pumps | Type, quantity, capacity and power supply |
| Control functions | Labels, valve positions and operating logic |
| Hydraulic interfaces | Hose size, fitting type and exit direction |
| Remote controls | Panel type, location and pilot or cable arrangement |
| Utilities | Voltage, frequency, phase, air pressure and airflow |
| Documents | Existing hydraulic, electrical and general arrangement drawings |
| Certification | Project, inspection and hazardous-area requirements |
Six Areas of Replacement Compatibility
Hydraulic Compatibility
Confirm operating pressure, flow demand, operator volumes, hose sizes and connection types.
Functional Compatibility
Verify the number of functions, valve positions, operating logic and emergency controls.
Electrical Compatibility
Check the voltage, frequency, phase, motor requirements, hazardous-area classification and communication interfaces.
Pneumatic Compatibility
Confirm the available air pressure and airflow, pilot-line sizes and remote panel operation.
Mechanical Compatibility
Check the installation space, lifting points, maintenance access, hose directions and transport limits.
Documentation Compatibility
Confirm the required drawing format, certificates, FAT records, manuals and spare-parts documentation.
Full interchangeability should not be claimed until these checks have been completed.
Common Koomey Unit Retrofit Options
A replacement project may add accumulator capacity, install new electric or pneumatic pumps, upgrade pressure regulators or replace directional control valves.
Older pneumatic remote panels may also be replaced with PLC controls, electronic pressure transmitters, alarms and event recording.
Other options include new hydraulic hoses, revised function labels, hazardous-area electrical equipment, winterization and desert protection.
SGPE can prepare a project-specific replacement proposal after reviewing the existing control system and current operating requirements.
API 16D BOP Koomey Unit Buying Guide
Compare Usable Volume, Not Bottle Count
A proposal may list many accumulator bottles but still provide limited usable hydraulic fluid.
The quotation should state the bottle size, total nominal volume, nitrogen precharge, maximum pressure, pump-start pressure, minimum operating pressure and calculated usable volume.
Compare the Complete Pump Package
The proposal should identify pump type, quantity, capacity, motor power, air consumption, automatic pressure settings, backup arrangement and expected recovery time.
Pump quantity alone does not provide a meaningful comparison.
Verify the Control Function Schedule
The control manifold and remote panels must include every required BOP and hydraulic valve function.
A missing function may require an expensive design change after manufacturing begins.
Compare Remote Panel Scope
A pneumatic panel, hardwired control station and PLC touchscreen system do not provide the same features.
Check whether the quoted scope includes pressure transmitters, alarms, valve position feedback, event recording, communication hardware, remote cables or pneumatic pilot tubing.
Confirm Hazardous-Area and Environmental Requirements
Motors, enclosures, junction boxes, cable glands, solenoid valves, instruments and panels must suit the specified area classification.
The proposal should also describe the actual desert, winterized or offshore protection package. A general environmental label does not provide enough detail for technical comparison.
Check FAT, Documentation and Lifecycle Support
Confirm the tests, reports, calculations and manuals included in the price.
A lower-cost proposal may exclude important performance tests or engineering documents.
The commercial review should also consider spare-parts availability, pump maintenance, component standardization, hose replacement and future upgrade options. The lowest purchase price may not provide the lowest lifecycle cost.
Assess the Supplier’s Engineering Process
A qualified supplier should request the BOP stack data, operator volumes, pressure basis, operating sequence, rig utilities, interface drawings and FAT requirements.
A quotation prepared only from reservoir capacity or bottle count may not be based on enough information.
Avoid Common Buying Mistakes
Common purchasing mistakes include using unverified BOP operator volumes, omitting the emergency operating sequence, ignoring pneumatic pump airflow and selecting the wrong motor voltage.
Buyers may also underestimate hydraulic hose length, compare different remote control systems as though they were equal, accept an undefined FAT scope or order a replacement unit without interface drawings.
How Much Does an API 16D BOP Koomey Unit Cost?
An API 16D BOP Koomey Unit does not have one standard price. Cost depends on the complete technical, testing and documentation scope.
| Price Factor | Effect on the Quotation |
| Accumulator capacity | More usable volume requires more or larger bottles |
| Number of functions | Additional functions increase manifold and panel scope |
| Pump arrangement | Dual electric, pneumatic backup or diesel pumps affect cost |
| Remote controls | PLC and touchscreen panels cost more than basic pneumatic panels |
| Hazardous-area equipment | Suitable motors, enclosures and instruments increase cost |
| Environmental protection | Offshore, desert and winterized packages add components |
| Hydraulic hose package | Longer or fire-resistant hoses affect cost |
| FAT and inspection | Third-party witnessing and additional records add cost |
| Documentation | Detailed calculations and data books require more engineering work |
| Spare parts | Commissioning and operating spares affect package value |
SGPE may prepare a preliminary budget price from a general configuration. A technically reliable quotation, however, requires the BOP stack, operator volumes, pressure requirements, rig utilities and control scope.
Customers comparing an API 16D BOP control unit price, BOP accumulator unit for sale or Koomey Unit replacement cost should review the complete technical scope rather than the headline price.
Factory Acceptance Testing
A reliable BOP control unit manufacturer should complete a documented factory acceptance test before shipment.
| FAT Item | Main Verification |
| Visual and dimensional inspection | Dimensions, layout, labels, guards, lifting points and access |
| Hydraulic leak test | Test pressure, medium, holding time and acceptance criteria |
| Pump performance test | Charging rate, start and stop pressure, leakage and backup operation |
| Accumulator drawdown test | Usable hydraulic volume and final pressure |
| Local function test | Correct opening and closing direction |
| Remote panel test | Response, indications and communication |
| Alarm and interlock test | Low-pressure alarms, emergency controls and logic |
| Electrical inspection | Motors, grounding, enclosures and control functions |
| Document review | Drawings, certificates, calculations, reports and manuals |
The accumulator drawdown test is one of the most useful checks because it confirms how much fluid the system can deliver while maintaining the specified minimum pressure.
SGPE can submit the FAT procedure for approval before testing. Depending on the contract, the test may be witnessed by the customer or an approved third-party inspection agency.
Project Documentation
| Document | Purpose |
| General arrangement drawing | Confirms dimensions and component layout |
| Hydraulic schematic | Shows circuits, valves, regulators and connections |
| Electrical schematic | Shows motors, controls, alarms and power supply |
| Accumulator sizing calculation | Confirms required usable hydraulic volume |
| Pump capacity calculation | Confirms charging and recovery performance |
| Inspection and test plan | Defines inspections, witness points and hold points |
| FAT procedure and report | Records functional acceptance testing |
| Calibration certificates | Confirm instrument accuracy |
| Material and component records | Support quality verification |
| Operation and maintenance manuals | Support commissioning and lifecycle service |
| Recommended spare-parts list | Supports planned maintenance |
The document language, file format and approval process should be confirmed during the quotation stage.
Installation, Inspection and Maintenance
The skid should be installed on a stable foundation with enough access around the pumps, manifold and accumulator banks.
Each hydraulic connection should be checked against the approved schematic rather than hose color or the previous rig arrangement.
New hoses and tubing should be flushed before connection. Contamination can damage pumps, regulators, directional valves and seals.
After filling the reservoir, confirm the fluid type, level and cleanliness. The accumulator precharge should then be checked with dry nitrogen and approved charging equipment.
Finally, test each charging pump and operate every function from the main station and each remote panel.
| Inspection Interval | Typical Checks |
| Daily or each shift | Pressures, fluid level, pumps, visible leakage and alarms |
| Weekly or scheduled interval | Filters, hoses, fittings, remote panels and electrical terminals |
| Periodic maintenance | Pump service, gauge calibration, relief valve testing and precharge checks |
| Major service | Accumulator inspection, valve overhaul, hydraulic flushing and full function test |
A normal pressure reading does not prove that the system still provides enough usable hydraulic volume. Periodic drawdown or performance testing gives a clearer indication of actual condition.
Common BOP Control Unit Problems
| Problem | Possible Causes | Recommended Check |
| Slow recharge | Low air pressure, low voltage, worn pump, blocked strainer or leakage | Test each pump and compare the result with FAT data |
| Frequent pump cycling | Hydraulic leakage, regulator leakage, low precharge or faulty check valve | Inspect the circuit before changing pressure settings |
| Aggressive annular closure | Excessive annular pressure or regulator fault | Confirm the recommended BOP control pressure |
| Slow remote response | Long pilot lines, low air pressure, restricted tubing or electrical fault | Check the circuit from the remote panel to the control valve |
| Pressure loss without operation | Hydraulic leakage, nitrogen loss or bladder damage | Depressurize safely and inspect the accumulator banks |
| Hydraulic fluid overheating | Continuous pump operation, bypassing, restricted flow or high ambient temperature | Identify the heat source before adding cooling |
Brand clarification: “Koomey Unit” appears in this article as a commonly used oilfield search term. Unless a quotation expressly states otherwise, an independently manufactured replacement system should not be interpreted as an original OEM-branded product.
Information Required for an Accurate Quotation
| RFQ Category | Required Information |
| Application | Rig type, onshore or offshore location and operating environment |
| Standards | Applicable API requirements and project specifications |
| BOP stack | Manufacturer, model, bore size and working pressure |
| Hydraulic data | Opening volume, closing volume and required control pressure |
| Functions | Complete controlled-function schedule |
| Operating sequence | Required emergency operations and minimum final pressure |
| Utilities | Voltage, frequency, phase, air pressure and airflow |
| Controls | Main panel, remote panels, PLC and communication requirements |
| Installation | Skid limits, hose lengths, connections and lifting requirements |
| Inspection | FAT, third-party inspection and documentation requirements |
| Logistics | Spare parts, packing requirements and delivery destination |
For a replacement project, also provide photographs, nameplates, existing schematics, remote panel details and interface dimensions.
SGPE can prepare a preliminary configuration from the available information. Once the technical inputs are confirmed, the engineering team can issue a detailed proposal and commercial quotation.
Frequently Asked Questions About API 16D BOP Koomey Units
1. What is an API 16D BOP Koomey Unit?
An API 16D BOP Koomey Unit is a surface hydraulic control system that stores and supplies the energy required to operate blowout preventers and related drilling well control equipment. It is also commonly described as a BOP control unit, BOP accumulator unit, BOP closing unit or oilfield accumulator unit.
A complete system normally includes a hydraulic reservoir, nitrogen-charged accumulator bottles, electric or air-driven charging pumps, pressure regulators, directional control valves, gauges and local or remote control panels. Depending on the approved configuration, the unit may operate annular BOPs, ram BOPs, blind shear rams, choke-line valves, kill-line valves and diverter functions on land drilling rigs, offshore surface BOP systems and selected workover units.
2. Is a Koomey Unit the same as a BOP accumulator unit?
In everyday drilling operations, Koomey Unit, BOP accumulator unit, BOP closing unit and BOP control unit are often used to describe similar hydraulic well control systems. However, Koomey may also refer to a specific branded product line, so the terms should not automatically be treated as identical in a commercial quotation.
A purchaser should clearly state whether the requirement is for an original OEM product, original spare parts or an independently manufactured replacement BOP control system. For a legacy Koomey Unit replacement or rig retrofit project, the proposed system must be reviewed against the existing hydraulic, electrical, pneumatic and mechanical interfaces before interchangeability can be confirmed.
3. What equipment can an API 16D BOP control unit operate?
A correctly configured API 16D BOP control unit can operate an annular BOP, pipe ram, variable bore ram, blind ram, blind shear ram and selected hydraulic choke-line or kill-line valves. Depending on the drilling package, it may also control diverter functions, hydraulic connectors or other auxiliary well control equipment.
The actual control scope depends on the approved BOP stack and operating philosophy. A conventional land rig may require only a limited number of functions, while a deep drilling or offshore surface BOP system may require several ram cavities, multiple hydraulic valves, a blind shear boost circuit and more than one remote control station.
4. How do you size an API 16D BOP Koomey Unit?
Sizing begins with the complete controlled-function schedule and the verified opening and closing volumes of every BOP operator and hydraulic valve. The calculation must also reflect the approved operating sequence, nitrogen precharge, maximum accumulator pressure, pump-start pressure, minimum final pressure and expected operating temperature.
Reservoir capacity and bottle count alone are not enough to determine whether the unit is suitable. The key value is the usable hydraulic volume available between the selected pressure limits. Pump recovery time, rig air capacity, electrical supply and any blind shear boost requirement should also be reviewed before the final BOP accumulator configuration is approved.
5. How many accumulator bottles does a BOP control unit need?
There is no standard accumulator bottle quantity that suits every drilling rig or BOP stack. The required number depends on each bottle’s nominal volume, nitrogen precharge, maximum storage pressure, pump-start pressure, minimum allowable pressure and the total hydraulic demand of the approved operating sequence.
For example, a compact land rig controlling one annular BOP and a limited number of ram functions may need a smaller accumulator bank than a deep drilling rig with a double ram BOP, blind shear ram and several choke-and-kill valves. A reliable proposal should therefore state both the nominal accumulator capacity and the calculated usable hydraulic volume.
6. What pressure does a surface BOP Koomey Unit use?
Many surface BOP control systems store hydraulic fluid at pressures up to approximately 3,000 psi or 20.7 MPa. Individual functions are then regulated to suitable operating pressures, which are often lower than the maximum accumulator pressure.
Ram BOPs and hydraulic valves commonly operate from a regulated manifold circuit, while the annular BOP normally receives adjustable pressure to control packing element force. A blind shear ram may require a dedicated boost circuit when standard manifold pressure cannot provide the required shearing force. Final settings must always follow the approved hydraulic design and the BOP manufacturer’s operator data.
7. Should a BOP control unit use electric pumps, air-driven pumps or both?
Many land drilling BOP control units use electric pumps for normal charging and air-driven pumps as an independent backup. This arrangement provides practical redundancy when both electrical power and compressed air are available at the rig.
A larger drilling package may use dual electric pumps together with pneumatic backup pumps to achieve faster recovery and greater redundancy. Remote projects may also consider a diesel-driven charging source. The final pump arrangement should reflect the required charging time, rig voltage, available air pressure and airflow, maintenance philosophy and environmental conditions.
8. Can a BOP control unit operate during an electrical power failure?
The accumulator bottles store hydraulic energy, so the control system may still complete selected BOP operations after electrical power is lost. The number of available operations depends on the remaining accumulator pressure, usable hydraulic volume and the emergency sequence defined for the rig.
Where sufficient compressed air remains available, an air-driven backup pump may continue charging the accumulator banks during an electrical failure. However, the actual emergency capability must be confirmed through the approved sizing calculation and accumulator drawdown test rather than assumed from bottle count alone.
9. What remote control panel should a drilling rig use?
Conventional land rigs often use pneumatic driller’s panels because they are simple, familiar to field crews and compatible with rig air systems. A second pneumatic panel may also be installed in the toolpusher’s office or another approved location.
Modern drilling rigs may use hardwired electrical panels, PLC push-button stations or touchscreen controls with pressure displays, alarms, event recording and system diagnostics. The most suitable option depends on the rig layout, hazardous-area classification, communication requirements and operating philosophy. Critical functions such as blind shear ram activation may also require protective covers, two-step operation or project-specific interlocks.
10. What is an accumulator drawdown test?
An accumulator drawdown test verifies how much hydraulic fluid the BOP control unit can deliver while maintaining the specified minimum pressure. It provides a more meaningful capacity check than simply confirming the number or nominal size of the accumulator bottles.
During factory acceptance testing, the system is charged to the approved pressure and then operated or discharged according to the agreed test procedure. The final pressure and delivered fluid volume are recorded to confirm whether the accumulator package meets the required operating sequence. This test is particularly important for deep drilling rigs, large BOP stacks and legacy Koomey Unit replacement projects.
11. How much does an API 16D BOP Koomey Unit cost?
The price of an API 16D BOP Koomey Unit depends on the complete technical, testing and documentation scope rather than one standard model number. Accumulator capacity, charging pump arrangement, number of control functions, remote panel type, blind shear boost system and hydraulic hose package all affect the quotation.
Cost may also increase when the project requires hazardous-area electrical equipment, offshore corrosion protection, desert or winterized packages, third-party inspection, witnessed FAT, detailed calculations or extensive spare parts. Buyers comparing an API 16D BOP control unit price or Koomey Unit replacement cost should review the complete technical scope instead of selecting the lowest headline price.
12. What information should I send for an SGPE BOP Koomey Unit quotation?
An accurate quotation requires the BOP stack manufacturer, model, bore size, working pressure and complete controlled-function schedule. The request should also include the opening and closing volumes of each operator, required control pressures, approved emergency sequence, minimum final pressure and any blind shear boost requirement.
SGPE also needs the rig voltage, frequency and phase, together with the available compressed-air pressure and airflow. Remote panel requirements, hydraulic hose lengths, connection types, skid limitations, ambient conditions, FAT scope, third-party inspection and documentation requirements should be included where applicable.
For a Koomey Unit replacement or drilling rig retrofit project, photographs, equipment nameplates, hydraulic schematics, remote panel details and interface dimensions will support a more accurate compatibility review and commercial proposal.
Why Choose SGPE for a BOP Control Unit Project?
SGPE supplies customized BOP accumulator and control systems for oil and gas drilling projects.
Instead of recommending a unit only by reservoir capacity or bottle count, the engineering team reviews the controlled functions, operator volumes, pressure basis, operating sequence and rig utilities.
The review may also cover accumulator bank arrangement, pump selection, annular pressure regulation, blind shear boost requirements, remote control stations and hydraulic interfaces.
Available configurations include skid-mounted, trailer-mounted and containerized systems. Depending on the project, the control package may include pneumatic remote panels, PLC push-button stations, touchscreen controls, pressure transmitters, alarms and matched hydraulic hoses.
For replacement projects, SGPE can review existing drawings, nameplates, photographs and interface dimensions before preparing a retrofit proposal.
For harsh environments, the system can be reviewed for desert protection, low-temperature operation, offshore corrosion protection and hazardous-area electrical requirements.
Before shipment, the agreed FAT may cover hydraulic leakage, pump charging performance, accumulator drawdown, local and remote functions, alarms, interlocks and electrical controls.
This project-specific process helps the customer obtain a technically matched control system instead of a generic accumulator package.
Related SGPE Well Control Equipment
SGPE can also supply related surface well control equipment, including API 16A Annular BOPs, API 16A Ram BOPs, API 16C Choke Manifolds, API 16C Kill Manifolds and API 16D BOP Control Hoses.
The available scope may also include BOP test units, drilling spools, adapter spools, hydraulic choke-line and kill-line valves, BOP spare parts and ram assemblies.
These products can form part of a complete surface well control package for land drilling, workover and selected offshore applications.
Request an API 16D BOP Koomey Unit Quotation
A reliable proposal starts with accurate technical information. Our engineering team will review the information and prepare a control-system configuration based on the actual drilling well control requirements.
Customers may request information about an API 16D BOP Koomey Unit price, custom BOP control unit quotation, BOP accumulator unit for sale, BOP closing unit supplier proposal, Koomey Unit replacement, drilling rig BOP control system or BOP remote control panel.
E-Mail:
info@sgpe.com
