Common LACT Components
Charge pump and motor
The LACT charge pump and motor are the primary source of energy for the system. It is important to understand the design aspects of the charge pump to ensure the system works properly and safely. Learn more.
Basket strainers are designed to help remove particles and debris from the fluid. They are typically located upstream of the pump to protect the pump and meter. The strainers will trap and collect materials through a perforated basket designed to collect solid materials. The strainers are designed to collect large amount of debris but if the differential pressure becomes too large they can rupture sending the debris into the pump and meter. In many cases a differential pressure gauge is supplied and used to monitor the amount of material in the basket strainer.
Air eliminators are components that are designed to remove entrapped air before it enters the meter. The less air in the fluid the more accurate the meter measurement. Air eliminators are installed in one or two locations before the meter; one being on the basket strainer and the other being at the highest point of the piping system.
BS&W Probe and Monitor
These monitors are an integral and important part of the LACT system. They are required to monitor the quality of the process fluid and are typically installed in a vertical run of pipe. The monitor often works with the divert system. When the probe detects fluid with an excess BS&W content the monitor will send a signal to the LACT controller to actuate the divert valve and diver the bad fluid into the reject line so that it is not metered and transferred. When the monitor detects good oil for a given time the divert valve will then allow the oil to pass through the meter.
Valin BS&W monitors contain:
- An adjustable range from 0-3% in increments of 0.1%
- Time delays mechanisms that prevent false alarms
- A “fail safe” feature
- Data tracking features
The divert valve is located before the meter and is used to control the direction of the oil. It can go one of two ways, through the meter or into a “reject” line that transfers the fluid off the skid to another designated location. When the LACT system is off or the BS&W content exceeds the contract value the valve will be in the closed position which diverts any fluid off skid. Conversely when unit is on and the BS&W content is adequate the valve will open and allow the fluid to flow through the meter.
The sample system consists of a probe that retrieves the sample and a storage container for the samples, and typically a pump to drain the storage container. The contents of the container are used to verify the quality of the fluid against the components for a given time period to verify the fluids transferred are what the instruments said they were. API gravity is also determined from the contents of the container. It is important that the container be vapor tight to prevent and evaporation of fluids or loss of entrained vapors. Learn more.
The flow meter is the heart of the LACT. It is used to measure the amount of fluid passing through the system during a transfer of custody. It is designed for accurate and precise measurement and responsible for accruing totals for a given time period. Learn More.
The prover manifold consists of three valves and two tees. It is used for calibrating the LACT meter with another meter. This should be done on a frequent basis depending on how much fluid is transferring custody. The proving meter is also used as a check against the LACT meter and requirements for proving are often built into lease agreements and contracts. The manifold should have 3 full port valves no smaller than the fluid meter size and equipped with sealing devices. The line valve shall have a double block and bleed balve to provide for leak testing during the proving operation. The ends of the manifold shall have quick coupling ends with locking devices and dust caps.
Back Pressure Valve (BPV)
A backpressure valve is typically installed downstream of the flow meter. It is designed to hold a minimum pressure against the LACT system to make sure the meter operates at a pressure greater than the vapor pressure of the fluid. When a centrifugal pump is used the back pressure valve supplies a constant pressure against the pump and in return the pump supplies a constant flow rate through the meter.
The back pressure valve can be used to regulate flow through the systems as long as the pressure remains above the vapor pressure of the fluid. A pressure sensing line is installed upstream of the valve to communicate with the valve on when to open and how far to open. When the system is off the BPV should be in the closed position. It is a good idea to install a BPV on the reject line if the system is equipped with a divert valve and reject line. The valve will prevent the pump from operating at a high flow rate (running away) due to a lack of back pressure.
The LACT control panel houses the electrical automation and data gathering components. It controls the LACT operation and works off inputs and sensors from the system and supply lines.