If wireless instrument doesn't exist, build it
By Mark V. Goloby
It started with a question, which created the need, which begat the search, which ended with a completely new tool for chemical injection monitoring.
The question seemed simple enough: How can we tell if a chemical injection pump quits injecting?
We have experience using wireless data techniques to remotely monitor cathodic protection systems, and our customer needed the answer to that question to insure no interruption of the prescribed level of chemical injected into his pipeline.
We first searched for an off-the-shelf solution to integrate into a wireless data device. Given low flow rates as little as one-half gallon per day and an actual per-stroke injection rate measured in cubic centimeters per stroke, such an instrument was not readily available. After a fruitless search, the only alternative was to develop it.
First, we conducted an analysis of the operating environment, which is an investigation into the operating conditions in which the product must perform.
Most injection pumps operate within a Class I, Division II, location under high pressure. Many are offshore, requiring special consideration for salt-air conditions. Those factors, plus the low flow rate, made for an interesting challenge.
We determined that the desired—or even better—results could be obtained on the low-pressure, gravity feed side of the injection cycle, as opposed to the high-pressure side. This eliminated the need for the high-cost fittings and equipment specifications required to operate under high pressure. Complying with the Class I, Division II, and addressing the salt-air environment remained a challenge, however.
Nothing was readily available to measure injection rates of less than 5 gallons per day (gpd), yet we needed an instrument flexible enough to measure a range of flow rates, from as little as 1/2 gpd to 20+ gpd.
The answer came with an analysis of the measurement technique. While it was impossible to measure the flow in stream, the delivery of a chemical can be broken down into smaller increments that can be tracked on a per-day basis. This formed the foundation for what we now call our chemical injection monitoring (CIM) system.
The chemical flows from a large holding tank into the CIM, a measuring device incremented to meet a defined volume measurement. These increments accumulate and then deliver over a wireless data network to a host system. This allows customers to access the data as they wish. You can establish alarms for high and low activity, as well as a database to accumulate long-term trends. From this data, users can perform a more thorough analysis of the effectiveness of the chemical injection program.
In order to answer the original question-"Is the pump injecting chemical?"-a set of generated data points vastly changes chemical inventory management. Suddenly, knowing the pump is injecting chemical is a minor concern.
With the CIM, we now know how much chemical is injected, how much has been injected over a variety of date ranges, and how much is left in the holding tank, all on a real-time basis.
Historically, a technician went to a chemical injection point to determine its status. There, the tech determined whether the pump was vapor locked, whether the chemical had run dry, and whether everything was in proper working order.
In the first two scenarios, there are faults with the injected chemical scenario. In the third, the trip was a waste of time. All three required a return trip in short order.
The CIM transforms the current status from an unknown to a known factor. The technician can now reasonably determine in advance if a trip is necessary and, if so, what tools or chemicals to take.
Also, with real-time information from the CIM, the company can implement tighter chemical inventory management techniques. Depletion time can be anywhere from a month to 9 months, and real-time metering makes real-time billing a new possibility.
All these factors lead to higher levels of asset integrity management and more efficient use of injection chemicals. IT
Behind the byline
Mark V. Goloby, president of Total Cellular Technologies since 1993, has been in the business of providing wireless data systems for various pipeline-related applications, as well as a host of other wireless human-to-machine interfaces.