What is Chemical Injection?
Chemical injection is the process designed to assist in the production of oil where various chemicals are injected into the crude oil to provide a degree of protection. For example; a scale inhibitor will prevent the build-up of scale on the pipes and fittings used to transport the oil on its journey to the refinery. Flow meters are used to monitor and control the amount of chemicals added to the crude oil and biocide prevents the build-up of organisms in the pipe.
Corrosion inhibitor is the most popular additive to be measured but there are various types depending on the type of main liquid. Pour point depressant is added to reduce the pour point thereby making the oil easier to flow through the main pipelines. Most of the chemicals added tend to be at low flow rates of the order of 0.01 to 40 litres per hour. LDH or Low Dosage Hydrate Inhibitor has the highest injection rate sometimes up to 17,000 litres per hour. It is designed to inhibit water based mixtures which would otherwise have a tendency to freeze.
A typical turndown ratio of 500:1 is measurable with some Positive Displacement flow meters. Often the systems are relatively slow dynamically and need only slight adjustments from day-to-day, which is why manual controls are still popular. It is important that the flow measurement system for the chemicals is able to cope with the pulsing nature of the pumps used and also with the high pressures that are encountered. These can be up to 1380bar/20,000psi/20ksi in modern systems injecting sub sea. Topsides injection is at lower pressures typically from 200 to 1000 psi.
Chemical Injection Additives
Methanol is often used with the same effect but more exotic chemicals are used for similar purposes all with the intention of reducing cost on the way to the refinery. It is a less known fact that flow meters are used to measure these chemicals which contribute 30% of the cost of running an offshore platform. Control systems are often manually set from the flow meter displayed value (either locally or from the SCADA system) and there is a trend towards automation of this process using control valves.
Chemical Injection Flow Meters
There is also a trend towards measuring the chemicals sub sea i.e. underwater rather than when the crude oil reaches the surface. Not only does the flow meter have to work at high internal pressures of over 10,000 psi, 690bar but also with external pressures up to 345bar/5,000psi. The flow meter within our range that is suitable for chemical injection, is the VFF which is often called the Chemical Injection Flow Meter with over 5,000 installed on Chemical Injection worldwide.
What’s the best chemical injection flow meter?
Litre Meter VFF rotary piston positive displacement flowmeters have proven to be the foremost solution for chemical injection flow metering applications. They are able to handle the wide range of flows at pressures from a few bar up to 10,000 and 20,000 psi (690 and 1,380 bar) and higher. The FlowPod instrument has been developed after […]
Since 1985, we’ve supplied businesses worldwide with a large selection of durable, industry-standard Positive Displacement flow meters. For the last four decades, we’ve built a huge catalogue of products to suit your every need organised by flow ranges – from our standard range of flow meters (popular in the UK, EU and US), to our […]