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

6. Assembly, Reliability and Testing

1 pic - AquFlow Metering Pumps

By definition, any system is an assembly of many individual components, parts and sub-assemblies. Many of these are manufactured by separate companies. When the system does not work properly it results in each manufacturer suspecting the issue to be with the other component manufacturer. As a result, this experience could become very frustrating quickly. Proper care and evaluation at the time of selection of these components are essential. Understanding of compatibility between components requires mechanical, hydraulic, electrical and chemical analysis to ensure these work well together and produce the end result desired by the customer. This is where a good systems integrator comes in with the expertise and experience to make it all come together and perform as per expectations.

One of the important considerations during the assembly is that it should be designed not only to perform onsite but also be able to withstand the movements and impacts during transportation if the system is assembled offsite. Adequate provisions need to be allowed to lift and place it in a truck, unload it from there and place it precisely on the intended site. While many pipes and fittings can be adequately supported for onsite operation, they will not be able to survive the transportation and handling resulting in leaks. Hence extra support should be installed for pipes and any other heavy component. The pipes also need to have easy to assemble unions at the ends so the suction and discharge piping can be installed correctly and quickly. A flexible coupling or tubing may be required in difficult and demanding situations. Do not have pipes or fittings carrying chemicals directly above important and sensitive components which will be vulnerable to a drip of chemicals corroding critical parts which could result in failure and hazard.

Another area often overlooked during the assembly process is the accessibility for service and repair of each component. Valve handles sometimes are pointing in the wrong direction or pump head is pointed towards the back making it more difficult to monitor the flow and service if needed. It is essential to understand the exact location and accessibility of the platform or base upon which this skid will be mounted so all components are still accessible when the skid is placed on the site platform. Clearance around the back and sides is important as there may be a wall behind which will prevent access or on the sides you may have hazards at the location that will endanger service personnel. And finally, it is always recommended to have a chemical containment basin at the base to prevent chemical from falling on the ground polluting the environment.

The system needs to be tested at the manufacturer’s facility with similar conditions as it will be operated onsite. The hydraulics need to mimic the site conditions and the electrical controls also need to be similar. This testing needs to take into account the normal variations you may experience onsite such as the level of the tank dropping below the pump (if applicable) or blockage in the discharge piping causing over pressurization. Electrical signals should also run the entire range of standard voltages and signal strengths to see if there is a vulnerability in the system.

Reliability testing not only means extended durations of the test under worst conditions but also cycling back and forth from extremes many times to see if such rapid variations expose weaknesses in the system. Environmental extremes such as ambient temperature extremes, humidity and rain need to be accounted for and protected against. This does not mean that every system needs to be protected against every environmental threat. For instance, we need not worry about rain and water ingress if the system is located indoors. On the other hand, if the system is located outdoors in very cold temperatures we may want to test it under those conditions to ensure that the system can start and operate well under these conditions. Starting, stopping and especially the interim periods when the system is sitting idle are important to consider for a reliable performance.

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