Technical Design Considerations for Filtration Vessels
Technical Design Considerations for Filtration Vessels
Filtration is an important component of the oil & gas industry to protect downstream equipment such as compressors, gas turbines, amine or glycol absorbers, molecular sieves, PSA's, metering stations, mercury guard beds, gas fired heaters or furnaces, and heat exchangers. Depending on process requirements, filtration removes a wide range of contaminants including solids, liquids and semi-solids, hydrocarbon condensate and provides a clean process for downstream equipment and customers.
There are several types of gas filtration vessels available on the market including vertical and horizontal coalescers and filter separators. The application and process details determine the type, size and design of the vessel. Commercial and regulatory requirements also influence the choices. There are several factors to consider when looking for a filtration solution and, in this article, we share the main technical design considerations.
Defining the purpose of a new vessel is the best place to start.
- An important question to answer is what needs to be achieved and why.
- Which downstream equipment is the vessel protecting?
- What is the contaminant to be removed?
Clarity in purpose creates a clear decision tree and narrows options quickly.
Another important factor is how and where the vessel will be used. Based on location, some choices can be made.
- Is the vessel for a remote location where it may be managed remotely? Is it going off-shore?
- Is it in a plant where it is easy to access and maintain?
- What kind of clearances are available where the vessel needs to be installed?
- Materials of construction
The materials used for vessels go a long way in determining its reliability and safe operation. Therefore, it is very important to make the right choice in selecting the appropriate material.
- Consider requirements around operating temperatures and pressures, chemical compatibility, corrosion resistance to both acids and bases,
- NACE and ASME guidelines and lethality helps to decide on materials of construction like aluminum, nickel alloys, carbon steel or stainless steel.
- Decisions also need to be made around surface preparation and coating options.
- Pressure and temperature ratings
The pressure and temperature ratings determine the design, connections and bolt up piping.
- Design involves parameters such as maximum safe operating pressure and temperature, safety factor, corrosion allowance and minimum design temperature.
- Construction is tested using nondestructive testing, such as ultrasonic testing, radiography, and pressure tests. Hydrostatic tests use water, but pneumatic tests use air or another gas.
- In most countries, vessels over a certain size and pressure must be built to a formal code. In the United States that code is the ASME Boiler and Pressure Vessel Code (BPVC).
- Operating conditions
Process flow description along with pressure, temperature, contaminants drive decisions around the type of vessel or housing.
The goal is to maximize efficiency while preventing contaminant re-entrainment. For example, re-entrainment can occur when liquid droplets accumulated on a coalescer element are carried off by the exiting stream. This occurs when velocity of the exiting stream, or annular velocity, exceeds the gravitational forces of the draining droplet.
- Upset conditions
The vessel needs to be designed to withstand temperature, pressure ratings for upset conditions to ensure the process works even when upstream conditions change. For example, if the heat exchanger upstream is not working well and the feed is received at higher temperatures. A well-designed vessel will be capable of handling the required range of operating conditions.
- Maintenance requirements
Access to the elements and instrumentation should be taken into consideration.
- Factors such as expected frequency of changeout or even geographical location of the installation can drive decision making.
- If the filters are going to be changed frequently, there are very efficient closures available that can reduce the changeout time compared to other closure types.
- If the vessel is to be located in extreme climates, vertical vessels may be challenging for operations as they require ladders and platforms.
- Process Connections
Parameters defining the inlet and outlet conditions can create unforeseen problems. Velocity and pressure drop limits through piping and transitions should be calculated to avoid shearing and fracturing of contaminants.
Manifold considerations can optimize operational performance of multi-unit systems. In addition, instrumentation connections and capabilities should address the contaminant volumes to keep vessel performing as designed.
- Non-process connections
Pressure safety valves for pressure relief, thermal safety valves, drains for clean outs for waste stream management are all points of discussion for design.
- In-house knowledge available
One other factor to consider is the knowledge available in-house, experience with existing equipment and availability of filtration experts on staff. This will determine the level of oversight, communication and project management requirements. Clarity on company specific design and NDE requirements at the start of a project is also important for successful project execution.
The technical design considerations highlight the fact that experience and expertise are both essential for high quality vessel design that will suit the application and deliver in upset conditions so when selecting a filtration solutions partner, consider their industry experience and knowledge, in-house capability, aftermarket supply, as well as references.
Jonell Systems provides a wide range of filtration solutions and expertise in refining and midstream applications. Our vast product offering allows our filtration experts to provide you with the best fit technology to address your filtration challenges to increase run times between changeouts, protect your downstream equipment, reduce your total cost of ownership and deliver a high-quality product downstream.
Find out more about our solutions for the oil & gas market and refineries or call or get in touch to organize an obligation free filtration optimization consultation today!