Providing uninterrupted power for monitoring and control equipment is essential in many oil and gas upstream, midstream and downstream applications, from a safety, economic and environmental point of view. The nature of these operations places them in remote locations, which means they are off the electrical power grid. This further implies a sparse population, with limited engineering and technical resources available to maintain these assets. In addition, these locations are usually accompanied by harsh, inhospitable conditions, such as extreme cold, intense heat, or the challenging conditions of being offshore.
The focus for many oil and gas companies is to ensure sufficient primary and back-up power should they experience loss of voltage from their battery systems. The batteries used can be either Lead Acid or Lithium Ion. Since batteries are drained when connected to a load, there is a growing need for a reliable battery charging options.
There is also a drive to reduce emissions in the oil and gas sector, which is leading to increasing interest in technologies that consume little to no hydrocarbons and have a positive environmental impact.
Having readily available ‘on-demand’ battery charging capability is a very attractive proposition for companies operating in remote, off-grid locations. Providing an extremely compact battery charger, offers greater convenience and space saving benefits in a space-restricted offshore operation. Lastly, there are transportation and storage benefits of using these kinds of compact designs in offshore or land-based, remote locations.
Using back-up power directly from the grid can be expensive, which is why more operators in remote locations are choosing renewable forms of energy such as solar, turbine and wind to power electronic instruments on gas pipelines.
Differential pressure battery chargers, like an alternator in a car, ensures the battery maintains its charge by providing a cyclic burst of energy for the instances when the battery voltage drops below the set level. When the voltage drops, the control system will detect the need to charge the battery and allow the gas to pass through the turbine to generate the current needed to charge the battery. When the power in the battery returns to the required voltage, it will enter into standby mode until the next charging cycle.
Parker offers the DB1 Differential Pressure Battery charger as an alternative to solar panel systems and large battery packs that are used to power electronic instruments on gas pipelines. Unlike solar panels, the DB1 can be installed in almost any location and is not affected by snow, ice, rain or dust build up. It is also extremely compact and lightweight and is capable of charging 365/24/7 on demand.
The DB1 is capable of producing a 12 or 24 volt power output to keep the battery fully charged in remote locations. It consistently monitors the battery’s temperature and charge level and produces up to 50 watts of power.
A growing application for this type of battery charger is Well Injection. Well injection applications stimulate the flow of oil. The pressure difference between the gas being injected into the well and the pressure resulting from the gas exiting the well is what spins the turbine on the DB1. This is particularly relevant on off-shore platforms, where there are unmanned well jackets.
The most common application is at the city gate stations or what are called regulator stations. These sites are located on the outer limits of a city on a gas pipeline. Gas pressure is reduced from 800-900 psi to 100-200 psi. This pressure difference is what is used to spin the turbine and generate the charge for the battery.
How the technology works
Battery chargers, such as the DB1, use the differential pressure developed across a pressure regulator on natural gas pipelines to run a small turbine-powered generator. Controlled start-up for these kinds of units makes turning the system ‘on’ as simple as flicking a switch. The generator output is used to charge a lead acid battery – similar to our Thermo-Electric Chargers (TECs). However, unlike the TECs, the DB1 does not consume any natural gas. Power is produced by allowing a small portion of the gas (up to 1440 psig system pressures) to flow through a turbine, bypassing the pressure regulating valve. The amount of gas flowing through the turbine is low relative to the total line flow, and remains stable, keeping the DB1 transparent to the pressure control system. The pressure regulator automatically adjusts for the slight decrease in flow resulting when the DB1 runs.
The power produced by the DB1 is micro-processor controlled to provide the ideal temperature compensated battery charging current and voltage to the battery. The DB1 also provides internal diagnostics to detect possible system problems. The system status can be locally or remotely monitored using the open collector alarm output. An optional communications controller is available to provide real-time communications with the DB1.
Differential pressure battery chargers
Demand is increasing for differential pressure battery chargers. Some of the reasons why include the ageing workforce increase and the skills shortage are important socio-economic factors. These factors point to a lack of knowledge transfer particularly with regards to asset maintenance. In addition, oil and gas companies are also looking to reduce their power usage.
The DB1 can be used anywhere in the world. It can be installed directly on the pipeline as it is Class 1 Division 1, Group D. As a compact unit, the DB1 is the right system for the times, as it meets all the requirements for no emissions, no use of conventional power, compact design and minimal user intervention. It is therefore little surprise that there was been an increase in demand for these products to meet the needs of the oil and gas industry.
B.J. Jackson is product manager, Parker Hannifin, Instrumentation Products Division