Transfer of Polymers in Aqueous Emulsion
The Client
The client is a long-established Italian company specializing in the production and commercialization of chemical products, including polymers, intended for textile, non-woven, coating, and adhesive sectors. The company has collaborated with Granzotto on several occasions to optimize its plant dedicated to the production of vinyl emulsions. The products manufactured find application in wood coating, decorative finishes, construction, and metal protection.
The Project
The interventions detailed in this case study were aimed at improving production efficiency. The focus was primarily on installing new transfer lines for liquid products within the water-based vinyl emulsion production plant. The implemented lines were equipped with PIG systems capable of recovering residual product in the pipelines, thereby preventing solidification during the harsh winter months, which could disrupt operations.
The Polymer Production Plant
The scope of the production plant in which Granzotto operated consists of multiple tanks with varying functions. The polymerization reaction of the monomer in solution takes place in a dedicated reactor. The resulting product is then transferred to finishing tanks, where specific additives are incorporated to complete the formulation. Subsequently, the product is transferred to outdoor storage tanks. From these, the product can be routed to the packaging line, to buffer tanks, or directly loaded onto tankers.
Granzotto’s first intervention focused on two transfer lines connecting the reactor to four finishing tanks. Both lines were equipped with PIG systems to minimize cross-contamination and reduce production times, given the client’s requirement to produce batches of widely differing products consecutively.
The second intervention, implemented earlier, targeted the transfer lines connecting the finishing tanks to the outdoor storage tanks, as well as those linking the storage tanks to the packaging line and buffer tanks. In the first segment, the product is transferred from the finishing tanks to a manifold plate, where an operator manually connects an external flexible hose to route the product to one of the storage tanks. Granzotto introduced an automated control system to verify the accuracy of the operator’s connections, blocking the transfer if incorrect, via valve control.
In the second segment, the product is transferred from the storage tanks to another manifold plate, from which it can be routed to additional tanks, the packaging line, or directly to tankers. Here, too, all lines were equipped with PIG systems to prevent product residues from solidifying when exposed to low temperatures.
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The Solutions
The challenges faced by the client were related to the residual product remaining in the pipelines after transfer operations, particularly in the plant’s outdoor segment. These issues caused production slowdowns and frequent maintenance interventions.
As noted, the problems were resolved by installing transfer lines equipped with G-RECO pigging systems for recovering residual products. Specifically, bi-directional silicone PIGs with four sealing blades and a dovetail were used. This type of PIG ensures excellent sealing and enables high product recovery but requires careful handling. The asymmetrical shape of the PIG, due to the dovetail, tends to open in the reverse direction during its return to the launch station, hindering its movement. Leveraging decades of experience, Granzotto ensured the system’s optimal reliability.
The driving fluid for the installed PIGs is water on the forward journey and air on the return. The choice of water as the driving medium was based on the need for a uniform motion, which air, being a compressible gas, could not guarantee. In the event of obstructions in the pipelines, the use of air could have caused “water hammer” effects due to compression of the driving medium, potentially compromising the integrity of both the PIG and the plant over time. The slight possibility of water leakage ahead of the PIG poses no issue for the client, given the aqueous nature of the treated product.
An interesting feature of the installed pigging systems is the ability to clean both the PIG and the launch chamber. This operation is essential to prevent polymer emulsions from accumulating in the chamber or on the PIG, which could compromise functionality. To clean the PIG completely, it must be fully retracted into the station, outside the pipeline. However, upon restarting, if the PIG is not inserted into the pipeline to engage at least the first sealing diaphragm, the driving water would flow past the PIG without generating the necessary pressure.
To address this, Granzotto implemented a pneumatic piston to insert the PIG into the pipeline after cleaning. This included specially designed seals that allow the piston to move without obstructions while withstanding the pressures of both the product and the water. To achieve the required tolerances for effective sealing, Granzotto designed the components and entrusted precision machining to trusted specialized partners.
In addition to the insertion pistons, the interventions required the installation of other specialized components. For example, to manage product recovery via PIG on the line directed to packaging — where the product comes from both external storage tanks and buffer tanks — a three-way valve with a specific actuator was installed. This actuator has three positions at 0°, 120°, and 240°. Correct calibration of the valve’s end stops was necessary to ensure effective PIG operation.
The intervention near the reactors required special precautions due to the area being subject to the European Union’s ATEX Directive 2014/34/EU, which governs potentially explosive atmospheres. In this area, there was a risk of pneumatic hoses made of plastic tearing, causing excessive air discharge and ignition hazards. To eliminate this risk, pneumatic connections were made with copper tubing, and all components used in the area (tubes, valves, sensors) were certified to meet ATEX requirements. Upon completing the intervention, Granzotto provided the client with a declaration of compliance with the regulation.
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