Ask Dr. Dave / Columns

Ask Dr. Dave

March 1, 2005
/ Print / Reprints /
ShareMore
/ Text Size+
March 2005

QUESTION: We are pumping a high-viscosity sealant through a robotic application system. Can you suggest a sensor that will monitor flow through the tubing and nozzle?

ANSWER: There are several types of flow sensors that you might investigate for your system. However, I would recommend that you look at two types, namely acoustic sensors and ultrasonic Doppler sensors. An acoustic sensor is essentially a very sensitive microphone that can detect movement of the liquid inside a tube and will be the simplest type of sensor if it works in your system and factory environment. A Doppler sensor is very sensitive and relies on the reflection of ultrasonic sound waves from solid particles or air bubbles in the sealant. Several companies manufacture these detectors, and both can be used on the outside of your pumping system.

QUESTION: I am confused by the terms "form-in-place gasket" and "cure-in-place gasket." Could you please clarify these terms?

ANSWER: Both terms are used to describe liquid gasketing compositions designed to replace cut or molded gaskets, with the major benefits being that they avoid the necessity of stocking a wide inventory of different-sized solid gaskets and they can be very cost effective in high-volume production situations, like the automotive industry. Unfortunately, the inventors of these terms probably got the definitions backward. Form-in-place is the term used to describe technologies like liquid RTV silicones or anaerobic sealants that are applied between two flanges immediately before assembly and then cure in place to form an elastomeric gasket (see where the confusion comes in?). Form-in-place gaskets rely on good adhesion to surfaces to maintain seal integrity. Cure-in-place gaskets are usually liquid silicones, acrylics or ethylene acrylic rubbers that are "formed in place" by applying to one flange only on a part and then curing by heat or UV radiation. Form-in-place gaskets are often applied in a production line of an OEM auto manufacturer, whereas cure-in-place gaskets are particularly suitable for a component manufacturer who can cast, stamp, or mold a part, apply a gasket and then supply a gasketed part to his customer. Form-in-place gaskets can be readily replaced in repair situations by applying the liquid gaskets from a cartridge or tube. Form-in-place gaskets can sometimes replace cure-in-place gaskets, but this may not be possible because of differences in flange designs for these two types of systems. In the latter case, one has to use a cut or molded gasket or buy a new part with the gasket already attached.

By the way, you may also come across the term "flow-in-place gaskets," which is another way to describe cure-in-place systems...but let's not confuse the situation further.

Q&A Exchange is written by Dr. Dave Dunn of F.L.D.Enterprises, a technical consultancy and full-service industrial market research firm specializing in the adhesives, sealants, specialty rubbers, and plastics fields. Dr. Dave is a former vice president and director of Loctite Corp., and has spent many years troubleshooting adhesive and sealant problems. Questions for publication should be directed to him at 242 Trails End, Aurora OH 44202; (330) 562-2930; FAX (865) 251-9687; e-mail DrDave242@att.net ; or visit http://www.fldenterprises.com .

Did you enjoy this article? Click here to subscribe to Adhesives & Sealants Industry Magazine.

You must login or register in order to post a comment.

Multimedia

Videos

Image Galleries

ASI April 2014 Photo Gallery

Our April 2014 issue is now available!

Podcasts

ExxonMobil Tackifier Expansion

Dwight Tozer, vice president of ExxonMobil’s Adhesion Industry business, discusses the company’s latest tackifier expansion project with Editor-in-Chief Susan Sutton.

More Podcasts

Adhesives & Sealants Industry Magazine

ASI July 2014 cover

2014 July

Our annual Distributor Directory helps you locate a distributor that best suits your needs. Check it out today!

Table Of Contents Subscribe

THE ADHESIVES STORE

handbook-sealant-tech.gif
Handbook of Sealant Technology

The Handbook of Sealant Technology provides an in-depth examination of sealants, reviewing their historical developments and fundamentals, adhesion theories and properties, and today’s wide range of applications.

More Products

ASI 2014 Buyers GuideASI's Buyers' Guide

Annual purchasing resource for equipment used in the manufacture/formulation of adhesives, sealants, pressure sensitives, tapes and labels and for application of finished adhesives. 

Clear Seas Research

With access to over one million professionals and more than 60 industry-specific publications, Clear Seas Research offers relevant insights from those who know your industry best. Let us customize a market research solution that exceeds your marketing goals.

STAY CONNECTED

facebook_40px twitter_40  youtube_40pxlinkedin_40 google+ icon ASI 30px