Major Factors to Consider in Designing and Installing a Chemical Injection Skid System

1.Scope and Compliance: Define clearly the purpose and functions of this skid system. Here you will define what chemical it is pumping, what would be the flow and pressure of that chemical. What is the function of the chemical in the overall process? How critical it is and if it requires redundancy and what is the duty cycle. Also briefly describe the environment where the system is located and where it will be injecting. Depending upon the application, industry and environment there will be a list of compliance requirements. Make a complete list of pump, environmental, structural and locational compliances.
2.Location / Structural & Power: Both the location of the facility and the location of the system within the facility are major factors that need to be surveyed. The structure on which the system will be mounted and structural requirements of the skid itself needs to be defined based upon the location and its vulnerabilities. The availability and feasibility of power which in most cases would be electric and in some cases would be solar or pneumatic would determine the motive system driving the injection pump.
3.Chemical and Performance Specifications: Choice of material of construction for the wetted parts and its corrosion resistance is not just a reliability issue but also a serious safety concern. The rate at which the chemical needs to be injected directly impacts the  effectiveness of the process. The pressure at which the chemical needs to be delivered would dictate the strength of the pipes and power for the driver / motor for the pump.
4.Control System: This is the brains of the system. The control system turns the pumps or valves on and off depending upon the verification of the actual flow delivery. Here we determine the sensors and other measurement devices and how they will work together to deliver the performance required for optimum process efficiency.
5.List of major components and procurement planning: Now we are ready to put together a detailed Bill of Material for the skid based on the answers of the questions above and the specifications from the customer or the engineering company. This is also where the budgeting and costing of the system is verified. The components are sourced and their deliveries matched to the schedule of the project.
6.Assembly, Reliability & Testing: Most systems are often assembled in a separate manufacturing facility and then delivered to the project site. Sometimes the system is delivered in modules and assembled at the site. And there are occasions where the entire assembly is done at the site. A plan needs to be drawn for preliminary leak and electrical testing for each component and as a system.
7.Transportation / Installation and Start Up: The skid system needs to be designed for easy and safe transportation. There needs to be close coordination with the site for delivery, installation and start up.

Scope and Compliance

For any project it is important to get everyone on the same page about the purpose and scope. It is just as important if not more important to define what the system is not designed to do as it is to define what it is designed to do. Often there is what is known as engineering creep that gets in and we end up with a system that is way over-designed and over-budget.

Start with a simple definition of purpose. It could be as simple as “to deliver precise amount of anti-scalant chemical to prevent scaling in the system pipes”. Then we can add what redundancies we intend to have in the system. For example we can state that there will be one main pump and one stand by. There could be similar redundancies incorporated in power source, motive driver and main controls and sensors for example. It is important to define the control system and how it will communicate with the broader process controls and sensors at the site. A quick consideration of the size and survey of the location is often useful at this stage.

If the system is being used in Oil and Gas industry often compliance with API standards is mandatory. Depending upon the location of the system Class 1 Div 2 explosion proof electrical devices including motors and valves would be required. It is useful here to work with a checklist of potential hazards and industry standards to come up with a list of relevant compliances. This is also the opportunity to determine whether quality procedures and QMS are a requirement for all vendors.

An important detail that often gets omitted here is the specific requirement for compliance testing and documentation. This avoids delays and budget busting if these are not clearly defined at this stage.

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