Valves and Instruments Blog

Archive for July, 2008

Pressure Gauges – Who needs them?

Tuesday, July 1st, 2008

The older I get the better I used to be, and the more opinionated I get!  Just ask my second wife.  So, bear with me, and let me vent on pressure gauges.

Install them!
I’m not sure why, but somewhere, sometime, someone decided to save money and skimp on installing pressure gauges.  Make sure you install them through out your system so that you can determine what’s going on later.  Obvious places include suction/discharge of pumps, inlet/outlet of pressure reducing stations and control valves, in your headers and the lines feeding your equipment.  You can never have too many gauges when you’re trying to troubleshoot a system problem.

Use Isolation Valves!
Make sure that you can separate your gauge from the process.  Needle valves are great for metering the fluid and reducing shock to the gauge from quick opening.  Male x Female NPT Ball Valves provide tight shutoff.  In any event, install an isolation valve so you can easily replace damaged gauges in the future without shutting down your process.

Don’t buy the cheapest gauge you can find!
Just like buying a Yugo, Pinto or a Vega (for you young folks – these were cars), you get what you pay for.  All gauges are not created equal!  For process plants the Ashcroft 1279 series gauges have the most robust bourdon tube design in the industry, as well as the best warranty.  Other gauges look the same, but they won’t perform as well or last as long.

Vibration – Deal with It!
There are a few ways to deal with vibration.  Obvious but often overlooked is to isolate the gauge from the source of the vibration (normally the piping).  Remote mount the gauge using one of our Teflon Lined SS Braided Hoses.  They solve the problem and look cool at the same time.  Can’t remote mount the gauge, select a liquid filled gauge or have us Glycerine or Silicone Fill a conventional gauge.  The liquid will dampen the effects of the vibration and the gauge will last longer.   The premium solution is to install the DuraPlus® Ashcroft gauges.  Their patented dampening movement outperforms liquid filled products.

Bottom line…
You need pressure gauges to tell what your process is doing, and I need them to help put food on the table to feed my bottomless pit teenage son.

A Blog on a Valve Web Site?

Tuesday, July 1st, 2008

Finally, after all these years, servicing great customers, selling great products, and working with great people, I have my chance to be heard by all the world.  Yes, I get my own soapbox, my five minutes of fame, my shot at the spot-light (reflecting off my hair-challenged noggin).   Will anyone listen?  Only time, and Google Analytics will tell.

Starting my 2nd half-century (I just hit the big 5-0), I’ve had over 30 years of applying valves and Instrumentation products to solve the problems of the industrial, commercial, process, power, chemical, pharmaceutical and every other type customer imaginable.  When I started, our technological tools were, slide rules & adding machines, then calculators, then programmable calculators, fax machines…then finally Al Gore invented the Internet, so now I blog!  While not a technological tool, it is a great communication tool, if anyone decides to listen.  To quote me, “A Blog is like having a conversation with your wife (no malice intended sweetie), but you can ignore it without having to suffer the consequences”.

That said, I hope you enjoy our postings.  The intention is to provide you with useful information, delivered in a light, informative manner (not intended to be arrogant).

PS:  Support  my new candidate for the 2008 presidential election:  http://www.youtube.com/watch?v=CQxRFP87a2s

Solenoid Valves – Minimum Differential Pressure Revealed

Tuesday, July 1st, 2008

Over the last 25 years, I’ve sat through dozens of training presentations on solenoid valves.  Every time the topic turns to minimum pressure differential, the presenter starts drawing hieroglyphics on the chalkboard with squeaky chalk.  If you don’t know what a chalkboard is, just Google it.   Then, pointing at his third grade level “drawing”, he starts explaining about diaphragms, pilot holes and all other non-sensicle (I know non-sensicle is not a word) stuff.  The room responds with blank stares and the occasional snore.  Topic covered and time to move on…

There are basically two types of designs in solenoid valves.  Direct Acting and Internally Piloted.

Direct Acting
The simplest to understand is Direct Acting.  When a Direct Acting valve operates, the coil directly acts upon the core of the valve and directly opens or closes the orifice in the valve body.  This valve does not need a minimum differential pressure across the valve body in order to operate.  In other words, the upstream line pressure and the downstream line pressure can be the same, and the valve will work – Zero Minimum Differential Pressure.   As the orifice size increases, and the line pressure increases, the amount of force to move the valve core also increases.  Eventually the coil size and the power requirements cause you to look for another solution, the Internally Piloted valve.

Internally Piloted
There’s a little more to the Internally Piloted valve, but it’s not rocket science.  Internally Piloted valves use line pressure and a diaphragm to assist the operation of the valve.  By using a small bleed hole in the diaphragm, the valve core acts upon the small bleed hole, and uses the line pressure to operate the valve.  These valves typically require a Minimum Pressure Differential of 5 psi.  In other words, the upstream line pressure has to be at least 5 psi greater than the downstream line pressure for this valve to operate.  Don’t know what your line pressures are?  Install some pressure gauges. We have them!

A word of caution about Internally Piloted Valves:  They work great on clean fluids.  It’s a good practice to always install strainers in from of them to keep the pilot bleed hole from getting plugged.  For dirty fluids, our piston valve would be a better solution.

Being a visual learner myself, I found a nice explanation on how a washing machine solenoid works, at least in the UK.  Check it out http://www.youtube.com/watch?v=e5434dDB-7w