Teledyne Hastings Instruments Blog

In this blog, we will discuss various system connections, or fittings, that are available for both our mass flow and vacuum products. We will briefly explore why you might select a particular family of fittings for your system. Also, we will touch on some basic installation Dos and Don’ts.

Mass Flow Meters and Mass Flow Controllers

Many users of low flow (0-5 sccm up to 0-25 slm) instruments appreciate the convenience of compression fittings. The Swagelok ™ brand of compression fittings is very popular, and many users ask for these by name. Compression fittings can be very reliable; also, they can be quickly uninstalled and reinstalled as needed. And, unlike VCR ™ and VCO ™ fittings (we will talk more about these in a minute), compression fittings do not require a separate o-ring or single-use gasket. Our flow products are offered with various size Swagelok™ brand compression fittings. While the 1/4” size is the most popular for many low flow applications, we also offer, even smaller, 1/8” size as well. Metric sizes, including 10 mm and 12 mm, are also available. Then, for even higher flow applications, we also offer 1/2”, 3/4”, 1”, 1.5” and even 2” Swagelok ™ fittings. Note that the largest compression fittings require a swaging tool. (Link?)

Per the “Tube Fitter’s Manual” published by Swagelok®, here are the steps for manual installation of Swagelok Tube Fittings up to 1 in. or 25 mm.

1. Fully insert the tube into the fitting and against the shoulder; rotate the nut finger tight.
   
   
   
2. Mark the nut at the 6 o’clock position.
   
   
   
   
3. While holding the fitting body steady, tighten the nut 1 ¼ turns to the 9 o’clock position.
   For 1/16, 1/8, and 3/16 in. or 2, 3, and 4 mm tube fittings, tighten the nut ¾ turn to the 3 o’clock position.
   
   

Reassembly Procedure is as follows:

1. Prior to disassembly, mark the tubing at the back of the nut, mark a line along the nut and body flats. Use these marks to ensure that you return the nut to the previously pulled-up position.
   
   
   
2. Insert the tubing or tube adapter end connection with pre-swaged ferrules into the fitting until the front ferrule seats against the fitting body.
   
   
3. While holding the fitting body steady, rotate the nut with a wrench to the previously pulled-up position, as indicated by the marks on the tubing and flats. At this point, you will feel a significant increase in resistance. Tighten the nut slightly.
   
   

The VCR ™ system from Swagelok™ is very popular with users who need high purity, all-metal, reliable sealing for either positive pressure or vacuum applications. For these fittings, a gasket, usually metal, is used to seal between the two symmetric sealing faces. In some cases, an elastomeric or PTFE gasket can be used. Metal gaskets (e.g. copper, nickel, or stainless steel) in VCR ™ connections should only be used once. Metal gaskets can be purchased with a retainer to hold the gasket in place when installing. The gasket is secured between the mating surfaces and the nut is drawn finger tight. Then, to finish installation, two wrenches are used to tighten the connection and create the leak-free seal. Note that copper gaskets require a 1/4 turn (90°) beyond finger tight while nickel and stainless steel only require an 1/8 (45°) of a turn.

HFC-302 with VCR fittings

The VCO™ system is convenient when the user wants to have fast make and break connections. It is also handy when space is limited. One part of the VCO™ connection includes an o-ring while the mating connection has a flat smooth finish. Installation is easy. A nut is made finger tight and then a wrench is used to tighten by 1/8 (45°) of a turn.

Usually, your fitting selection and piping are going to be a function of the flow rate. Our application engineers are available via email, phone or LiveChat to help you.

Vacuum Gauges

There are several popular systems of connections for vacuum gauges. Selection of a system should be driven by base pressure, outgassing load, and of course, cost.

For many users who just need to reach the mTorr range of pressures, tapered pipe thread (NPT: National Pipe Tapered) connections are simple, require no external clamps or bolts, and can be assembled quickly. However, PTFE tape or some other sealant should be used on the threads for two reasons. First, the tape/sealant fills the void between the mating thread surfaces and second, the tape/sealant acts as an anti-galling lubricant between the threads.

When wrapping PTFE tape onto NPT threads, start with clean surfaces and a clean cut of the tape. Make sure the tape is flat as it is wound onto the sealing surfaces and wrap in the direction of the threads. Two to three wraps is adequate. End the wrap with a clean cut of the tape. Tighten the connection with a wrench. How tight? Well, there is no right answer except to say that you want the system to seal, but you don’t want the threads to strip. So, use a wrench until tight, but do not try to force and overtighten.

The KF system is convenient for users who need a fast leak tight system connection for their vacuum gauges. “KF” is short for Klein Flansche which is German for small flanges. Vacuum systems with KF flanges can reach into the 10^-8 Torr range. KF sizes, such as KF-16 and KF-25, are related to the maximum nominal inner diameter tubing in millimeters that can be attached to the flange.

Teledyne DV-6-KF-16 (Shown with o-ring assembly and clamp)

And lastly, ConFlat hardware is ideal for high vacuum and ultrahigh vacuum systems. ConFlat flanges have a knife-edge that seals against a gasket, usually copper. The connection is made by tightening a series of bolts; the number of bolts is a function of the size of the flange. Clean, baked, suitably pumped systems using ConFlat hardware have been known to reach pressures below 10^-13 Torr.

DV-6 Gauge Tube with ConFlat Flange

If you would like to discuss your application for vacuum gauges, mass flow meters, or mass flow controllers, we are standing by. You can reach us by phone (1-800-950-2468), email (hastings_instruments@teledyne.com) , or by using our LiveChat box at www.teledyne-hi.com or clicking on the box below.

Note: All photos of Swagelok fittings in this blog are used with their written permission.

Did you know? Even if your flow controller does not have the color touchscreen display, the 300 Vue flow line still allows you to switch between analog & digital control by using the zero button. (See the diagram below). You can also toggle between RS232 & RS485. This is a convenient feature when users want to switch their setup. Instructions can be found in the manual (pg. 14).

And, of course, we have our free Windows™ software. With the software, you can quickly configure and control your 300 Vue. And you can also record flow data and store to a file If you would like us to send a secure transfer download link for the free software, click here: https://www.teledyne-hi.com/resource-center/software

Teledyne Hastings designs and build mass flow controllers for a broad array of markets from clean laboratory environments to heavy industrial installations. Recently, we have been asked to provide our newest line of Digital 300 Flow Meters and Controllers into more demanding environments. And, we are proud to offer an optional IP-67 enclosure, which provides protection against dust and water. More on our product later in the blog.

But first, let’s explore the IP, or Ingress Protection, rating system.  NEMA (National Electrical Manufacturers Association) publishes a standard (ANSI/IEC 60529-2004) entitled, “Degrees of Protection Provided by Enclosures (IP Code)”. The corresponding international standard is IEC 60529. The introduction to the IP Code starts:

This standard describes a system for classifying the degrees of protection provided by enclosures of electrical equipment for two conditions: 1) the protection of persons against access to hazardous parts and protection of equipment against the ingress of solid foreign objects and 2) the ingress of water.

The IP Code rates the degree of protection by using two numbers. The first number describes protection against solid particles; the second number describes protection against liquids. The Wikipedia page describing the IP Code provides a couple of nice tables to help us quickly understand the numbers.

Which now brings us back to the Teledyne IP-67 rated enclosure. The first number, “6”, indicates that our enclosure is completely protected against dust. The second number, “7”, indicates that our instrument can withstand submersion in water up to a meter in depth for up to 30 minutes.

One side note about IP ratings, if you follow the battle between Samsung Galaxy and Apple iPhone, you may have seen an article published by CNET last September (2017). In the article, it was stated that the iPhone 8 and 8 Plus are certified with an IP67 rating, while the Samsung Galaxy S8 is rated IP68. And by the way, yes… according to Reddit, the whole putting the wet iPhone in rice thing to dry it out, does work.  

In order to claim the IP-67 rating, Teledyne Hastings has sent test instruments to NCEE Labs in Lincoln Nebraska. In general, there are two tests, one for dust and one for water. Aaron Steggs, Senior Test Engineer with NCEE explains, “The testing to receive the dust rating is not trivial. There is a vacuum test on the enclosure to ensure that no ingress of dust can occur. The vacuum pressure used is 2kPa.”

Aaron goes on to explain a little about the water test, “When talking about immersion testing, there is a greater chance of water being forced into any opening due to the weight of the water about the instrument under test.”

In any case, we have passed both the dust and water test and now you can have the accuracy and fast response of the Digital 300 Series in an IP rated enclosure.

For more info about our digital 200 mass flow meters and controllers, please visit www.teledyne-hi.com or click the button below for more inforamation on the IP-67 version now available.