The purpose of a chemical injection skid is to inject a precise amount of chemicals into a system either continuously or intermittently to protect its mechanical integrity by preventing corrosion and formation of foam, wax or scale. This ensures optimal operations. The skid consists of a chemical storage tank, pumps, valves and various kinds of process instrumentation, e.g. for level, pressure and flow measurement. Skids are mainly built by specialized OEM companies on request by end-users who utilize them in their operations.
To create an optimal balance between protection of the system where the chemical gets injected and OPEX it is essential that the skid performance is reliable and repeatable, i.e. it must be able to operate in a tight tolerance band with respect to the amount of chemicals being injected. Injected chemicals must be just enough for asset protection, but no more than this as it would only result in unnecessary use of expensive chemicals.
In the past it has been common practice to over-inject chemicals to be on the safe side; on the one hand to avoid costly downtime and repairs, and on the other hand to compensate for the increasing measurement uncertainty provided by conventional flow technologies as they wear out during operations. Today, the modern technology of Coriolis flowmeters enables end-users to both optimize their productivity and minimize their OPEX safely and long-term thanks to reliable performance. In addition, the absence of non-moving parts provides significant savings in reduced maintenance and corresponding efficiency gains compared to conventional flow measurement technologies.
For the above-mentioned reasons, there is an increasing preference by end-users to use Coriolis flowmeters for chemical injection.
The savings accrued by avoiding over-injection of chemicals can be substantial. The ROI of a Coriolis based chemical injection skid can be reached in just a few months thanks to the highly accurate measurement of the expensive chemicals used, thereby avoiding costly over-injection.
The recently released Proline Promass A from Endress+Hauser was developed with chemical injection in focus. It comes in three different sizes covering the various flow rates needed. Thanks to its lightweight and space-saving design, Promass A assists in keeping the skid compact and light. Actually, the smallest measuring device (size DN 1 [1/24”]) is no larger than a wallet.
A multitude of threaded and flanged process connections are available in different pressure ratings up to a maximum of 430.9 bar (6250psi). The Promass A is offered either with a 4-wire compact or remote transmitter (Promass 300 & 500) or as a loop-powered 2-wire device (Promass 200). Promass A can be used at process temperatures between –50 to +205 °C (–58 to +401 °F) and its wetted parts made of stainless steel 316L or Alloy C22 are NACE MR0175/MR0103 compliant.
Not only the wetted parts of the Promass A provide high corrosion resistance, but also the 316L sensor housing is especially suited for harsh ambient conditions in the offshore and onshore sectors where aggressive, salty air is present. The design and complete fitting options of Promass A are complemented by an unprecedented measuring performance, a result of its innovative sensor concept.
In contrast to traditional Coriolis sensor designs, the measuring tube geometry of Promass A is formed centrosymmetrical in relation to the exciter. Furthermore, the measuring tube is excited to oscillate at a significantly higher frequency than usual. This leads to a symmetrical oscillation and perfectly balanced measuring tube movement. The measuring performance of Promass A is also not affected by external influences. This is ensured by a vibration-compensating base plate, which acts like a “shock absorber” that effectively shields the entire sensor system from external interference factors.
As a result, even the smallest flow rates of just a few grams per minute can be measured with previously unreached zero-point stability and accuracy.
Promass A is a Coriolis flowmeter that meets the majority of the various specifications defined by our customers. The enhanced low-flow performance has improved the accuracy levels we can offer to our customers for the most challenging applications. Generally, we prefer to use two-wire instrumentation on our skids since it reduces cost, complexity and weight as no external power supply is needed. With the introduction of the Promass A 200 we finally have a loop-powered Coriolis flowmeter that meets our demands. In addition, we also appreciate its intrinsically safe Ex concept and the corresponding safety gains.
With the newly purchased skids containing the Promass A we see a significant savings potential in the overall chemical usage as we now can operate with significantly tighter tolerance bands. This will support our competitiveness in a challenging market.