A customer is custom tinting 5 gallon pails of silicone sealant for the construction industry. The formulas consist of a white silicone base, a highly thixotropic material with viscosity at 1,000,000 centipoise. The base white which is approximately 90% or more of each pail has concentrated colorants of 3,000,000 centipoise added in small amounts to the pail to finish the color formula. The customer hopes to both automate the existing manual process, and increase the production rate by a magnitude of 3.

Engineering Discovery at customer site:

Silicone is highly thixotropic, which means the greater the velocity of this material being pumped the lower the viscosity becomes.
Very viscous materials. Pumping these thick materials builds high pressure at the pump outlet and high pressure losses through the tubing.
Since the base white silicone is 90% of each batch, it must be pumped at a significant rate in order for the customer objective of tripling the projection rate can be met.
Typically handling viscous materials of this nature, require large pumps and tubing which usually mean a significant loss of accuracy for a dispenser.

Lab Trials at GFS site:

Customer sent samples of both the base white silicone and the concentrated colorants to GFS.
It was determined that the trace amounts viscous colorants required for the formulas could be moved from Stainless Steel pressure tanks through standard nylon tubing by applying a small amount of pressure to the vessel. Simple, repeatable, pulseless flow which would result in the needed accuracy at the dispenser.
High Torque agitators necessary for each SS Pressure tank.
It was found that the base white silicone which is pumped from customer supplied drum/pump system would require a surge bladder to reduce the large pulses being generated by the customer supplied drum pump.

Our Solution:
Gravimetrix

The Gravimetrix system was comprised of a 10 Nozzle Dispense station positioned above a high resolution scale.
A purged control enclosure houses the controller, operator interface, and intrinsically-safe mouse and keyboard.

The colorants are supplied via Stainless steel pressure tanks with agitators (smooth pulseless flow) while the base is supplied by drums fitted with pneumatic pumps and agitators and fed to a GFS supplied special surge bladder system..

Benefits:

More than tripled customer production rate.
Automatic calibration. Full Sql Server based reporting system.
Directly interfaces to customers’ formula database.
All wetted materials are of Stainless Steel construction. Easy to keep clean and maintain.
Traceability of each batch produced.