February 2, 2010 

'Inside Hydraulics' Newsletter
http://www.hydraulicsupermarket.com


IN THIS ISSUE
1. A word of advice from President Ford
2. A simple technique for preventing 'dry' starts
3. 132 cardinal sins... of hydraulics
4. Content for your web site or e-zine
5. Help us spread the word
6. Tell us what you think

1.

A word of advice from President Ford

If you've been hanging around with me for any length of time, you'll be aware that one of the core philosophies I espouse is the extreme value of ongoing education. And not 'education' only in the formal sense of the word, but continuous learning in all its various forms.

It's being my observation over many years now that almost everyone divides into one of two groups: those who make continuous learning a lifelong habit and those who do not; those who are willing to pay the price for success and those who are not.

And it always gives me pleasure to watch the progress of our members - many of whom have been with me for more than seven years now, as they forge ahead in their careers. This story from Cameron Ward from Wollongong, Australia is typical:

"I completed my Mechanical Engineering degree in 2001 and in 2004 joined the fluid power engineering team at a local steel mill. I've learnt so much in this time and am always excited to learn more.

We've recently carried out a reline of our #5 Blast Furnace. Part of this was to install three completely new hydraulic systems - from the ground up. New reservoirs, pump sets, valve stands, and more than three kilometers of carbon and stainless piping.

In addition to the work on the reline, in keeping with the philosophy that we should always keep learning, I've started my 2nd degree. I am studying Civil Engineering now - I'm 36 with a wife and 2 kids too. Talk about a busy year.

Going back to Uni has re-enthused me to learn and learn - I'll always have a soft spot for hydraulics, and will always want to learn more and more. So I've signed up to your 'Hydraulics Pro Club' and am looking forward to my first issue."

About guys like Cameron all you can say is: you can't keep a good man down; they're going places. But I'd also say Cameron's story is unique in at least one way.

The majority of College/University educated people who join large companies generally do not invest their own nickel on education, training or personal development. The usual attitude is: "I'm not spending anymore on education until my student loans are paid off."

And since it takes 'em about 20 years to take care of that, the learning stops. If they're lucky, the company may pick up the tab but often the employee doesn't take it nearly as seriously as if they spent their own nickels. And as with any other form of thumb-sucking dependency, it comes with inherent risk.

President Ford once said: "Government that is big enough to give you everything you want, is big enough to take everything you have." When it comes to your ongoing education and professional development, I'd say a company that is big enough to give you everything you want is big enough to take everything you have.

The point, which is perhaps rude and unwelcome to some: this is too important to be left up to someone else.

But I hear from a LOT of members who do just that:

"I am currently working for the US Coast Guard. We have two journeyman mechanics and two apprentices. None of us has had any formal training in hydraulics. I came across your web site a few years back and subscribed to your newsletter. It has been very informative. I am trying to find a good school that one or more of us can go to for some in-depth training. I saw your home study course, but I don't think the government will go for something like that..."

Like I said, nice if you can swing it: but not wise to depend on it for your professional development and career prospects. And know where the buck stops: 'if it's going to be, then it's up to me'.


The Nice Things People Say ...

"The knowledge I've gained from this information has been so valuable it has earned me a raise!" Find out more ...

Jack Bergstrom
Heavy Equipment Mechanic
Sharpe Equipment


2.   A simple technique for preventing 'dry' starts

One of our members sent in this question:

"Some time ago I was subcontracted to remove a 30 gpm, 4000 psi rated pump from one plastic injection press and install into a similar system for the same company.

The pump and prime mover are both beside and below (approx 12") the bottom of the reservoir; a "flooded inlet" design. AND, except for the ball valve at the tank port, no other noted restrictions.

The customer insisted that I fill the pump case; I did so, but reassured that except for the reservoir being empty, the pump would always have an adequate fluid level. I know that to be safe, there's no harm in filling the pump case, but if a pre-fill is forgotten, would it damage the pump?"

This is a fair question and worthy of detailed discussion here. Because like almost all other questions relating to hydraulics, the short answer is: "it depends".

And 'it depends' because there are always a number of possible variables to consider. In the above situation, we are considering a piston-type pump with a 'flooded inlet'. A flooded inlet means there is a head of oil above the pump's intake. In other words, the pump is mounted below minimum oil level. And in a perfect world, this would be the only position you would find hydraulic pumps mounted in.

Now, when you have a flooded inlet, there are essentially two things you want to make sure of before you spin the pump: first, that the pipe or hose between the tank and the pump's inlet is purged of air, and second, if the pump has a 'case' that it is full of oil.

Gear and vane pumps don't have a 'case' as such, so once you have purged the inlet line of air, you are good to go. Oh, and you can't purge the air from the inlet line without opening the insolation valve (if fitted) first - which is kinda reassuring.

But if it's a piston pump you're dealing with, the physics are a little different and there's another possible variation to consider: Some piston pumps have a 'flooded housing' (case). This means the pump's intake port is connected to, or is common with the housing or case. In other words, if the pump has a flooded housing, flooding the inlet, floods the housing or case as well - in theory at least.

Piston pumps with a flooded housing are easy to pick, because the generally don't have a case drain line. They don't need one because the case is common to the inlet, and therefore the tank.

But this doesn't mean flooded housing piston pumps don't require special attention during pre-start. Imagine an installation where there is say 3 feet or 1 meter of head above the pump, and the intake line is 4" or 100 mm in diameter and 1 meter long. The pump housing has a volume of about a gallon or 4 liters.

Now imagine you have just changed out this flooded housing pump, so the intake line and the pump's housing will be full of air. When you open the inlet line isolation valve, oil floods the inlet and the housing of the pump. But the air in the inlet line and case has nowhere to go - except to be compressed into the housing of the pump (remember there is no case drain line to allow this air to bleed back to tank).

The solution is simple enough, but often overlooked. After the isolation valve is opened, the uppermost plug in the pump's case should be carefully 'cracked' to allow trapped air to escape from the case. This ensures none of the pump's internal parts are 'dry' upon start up.

Piston pumps which do NOT have a flooded housing can still flood their own case - assuming they have a flooded inlet of course. But it happens SLOWLY. This is because the only connection between the pump's inlet and its case are via internal clearances - mainly between the pistons and their bores.

So with the pump installed and the inlet flooded, oil leaks slowly past half the total number of pistons - the other half will be communicating with the pressure port, and as the case fills, air is displaced back to tank via the case drain line.

As you can imagine, it can take several hours or longer for the case to be completely filled in this way. So in a situation where the pump is changed out and the machine is immediately re-started, it is essential that the pump's case be filled manually with clean oil through its uppermost case drain port to avoid damage.

If this all sounds way too complicated, I can simplify it for you: Before re-starting a piston pump, crack loose the uppermost connection on its housing or case. If oil comes out, the housing is full and you can check this step off. If oil doesn't come out, you need to make it so that it does.

So to answer this member's question: Yes, the customer was correct in insisting the pump case be filled with oil - or at least confirming that is was. And yes, the pump could most certainly have been damaged if this step had been missed.


"This book has the potential to save many organizations lots of money. It should be on the bookshelf of every engineer, supervisor, planner and technician who deals with hydraulic equipment... it's worth its weight in gold." Find out more

Alexander (Sandy) Dunn
Plant Maintenance Resource Center



3.   132 cardinal sins... of hydraulics

At the end of last year, I ran a little competition in which I invited readers to send me their favorite must-not-do or 'Cardinal Sin' related to hydraulics. Several hundred members submitted entries and I edited and compiled them all into one, succinct document, titled:

132 'Cardinal Sins' of Hydraulics ... What NOT To Do With Hydraulic Equipment.

It's well worth the read and a gift for all members, so if you haven't got your copy yet, ~OptIn_23~


4. Content for your web site or e-zine

Need some fresh content for your web site or e-zine? You now have permission to reprint these 'Inside Hydraulics' articles on your web site or in your e-zine, provided:

1. Each article is printed in its full form with no changes.

2. You send an e-mail to editor@hydraulicsupermarket.com to advise us where you'll be publishing them.

3. You include the following acknowledgement at the end of each article:
About the Author: Brendan Casey has more than 20 years experience in the maintenance, repair and overhaul of mobile and industrial hydraulic equipment. For more information on reducing the operating cost and increasing the uptime of your hydraulic equipment, visit his web site: http://www.InsiderSecretsToHydraulics.com


5. Help us spread the word

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6. Tell us what you think

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Just e-mail the editor at: newslettersuggestions@hydraulicsupermarket.com

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