I am commissioning a new power unit and piping system which will feed two existing MTS manifold/servo system. Unfortunately the company in charge of the project/sub-contractor allowed the steel pipes to fill with water and debris. Replacing the pipes is not an option. My big concerns are assuring an adequate flush and rust coming off after the flush is completed. Would appreciate any constructive comments.

• power unit: two 100hp motors, ~120gpm @ 3000psi
  
• piping system (sized for future expansion to 180gpm): 2" pressure, 2.5" return, black steel, 3 branches 25-40ft each
  
• filters: 2um kidney loop, 5um @ pump discharge, 5um @ reservoir return (will be removed after flush), 5um at manifold inlets

Supplier's flushing plan:
- MTS manifolds and servos will not be connected during commissioning, will be replaced with shunts
- temporarily install 5um return filter at reservoir
- fill reservoir with 3um filtered oil
- purge air from branches
- flush each branch individually with 120gpm until online particle counter gets ISO 16/13/9 or better.

ISZ

Are the 5um FILTERS at the servo valve manifolds a Non-Bypass type? OR ANOTHER WAY OF ASKING, Do the 5um filters have 30-50 PSI Bypass Valves? I never use Filters with Bypass valves on Proportional or Servo valve circuits. I consider it is better to shut the machine down because a plugging filter slows the cycle or even stops it instead of when the valves lock up from contamination that bypassed from Surge Flow or neglect of proper moitoring. Pressure Swithches that are available for all filters and can indicate an impending problem and alarm maintenance a filter element needs changed under normal operation. The Non-Collapse Filter Elements are not cheap but they are a lot less ecpensive than DOWNTIME due to contaminated valves.

I always replace Proportional and Servo Valves with their companies Manual Flushing Valves or a Bang-Bang valve and cycle those circuits with high flow, first with the actuators lines disconnected and then reconnected to each other to make a Loop path. Also manually cycle the disconnected cylinders to empty them of all the oil possible so when they are reconnected to their flow lines they get filled with filtered oil.

Pay Me Now or Pay Me Later takes effect when Proportionalor Servo Valves are concerned. Even everyday Spool Valves work better and longer on clean oil.

I dont envy the task as something is always overlooked.I have done this a few times over the past year when ill informed maintenance crews think they are doing the right thing,One thing i can recommend from previously flushing and kidney looping systems is that ENSURE that the temp of the fluid is at optimum operating temperature.
Your flushing /cleaning plan looks solid.I work for a very large mining company and we found the oil coming in from our supplier didnt meet ISO standards,they have spent 00's of 000's of dollars to correct this from their distributor if you want the oil clenaliness reliability test this too!

The presence of water and debris can lead to future troubles, normally black steel is not suitable for servo systems, the welded black steel release during the time small scales dangerous for servo valves, so stainless steel is the correct choice for the interconnecting piping when there are servo valves.

The presence of water and related rust worsen the problem. Because the welding & rust presence pickling is mandatory, otherwise the piping will release continuously rust and scales

There is no possibility to flush very big debris, moreover no system has enough filters around to block flame cutting debris like this

Big debris can walk around back and forth making only noise because too much heavy to reach the equipments(photo found in internet)

If the pipe route goes down into trenches then up to the hydraulic equipment, happen if the big debris is too much heavy it is not able to overcame the vertical branch.

When the system works, peaks of flow, can be strong enough to allow the debris to reach critical valves

I had to work hard to persuade a client to modify the piping as shown in the sketch, after modificationthe malfunction stopped.

So I Suggest to inspect as many critical spots as possible; shooting photo in order to inform the client about the risk of residual contamination can still remain after flushing.

Last suggestion regards the servo valves, better choice is when are external pilot line type.

Whith this version, a small pilot line filter, without by-pass mounted directly on the manifold protect the critical stage of the servo.

Because the size of the pilot line is small, Then the cost stainless steel pipes is low and the pilot filter last longer

Luciano

1. filters: We usually apply a bypass type low pressure element in front of a high pressure non bypass unit. The first (bypass type) filter is the service item that gets normal routine changes (cheaper)

The non bypass is last chance in case the first one bypasses too much or is ignored. The elements also cost 10x as much, so by using the series approach we have the non bypass protection but (usually) at low cost element prices.


2. Your piping: flushing and filtering is great, but I would be more concerned that all that does is remove the loose dirt. If there is water there is likely rust formed. It won't be all removed. It will be flaking off at bad times for months or years.

We had a similar situation with some open hydrostatic pipes, made of hot rolled instead of P&O steel, then allowed to rust over that. Not my project, and about 8 years ago, so memory is foggy. Had a company in with a trailer mounted heater and pump unit. They flushed a hot water caustic or acid of some sort that removed the rust and flushed at very high Reynolds numbers because it was water based and very thin. After about 12 hours of that, they flushed with clear hot water, then went to light oil flushing. In addition I think they went over accessible pipes with air impact hammers on the outside (although I think with thick wall pipe that was probably more placebo effect for the customer than actually effective).

The company was a national chain or franchise with regional offices but I don't know who it was.


There are also flexible rubber sandblasting processes for blasting pipes in place, but I would not go there. Unless all welds are guarantied to have no internal crevices of any kind, anywhere, there is likely to be trapped sand grit.


It is a pain, and hard to sell schedule delay to management, but pay now or pay later, and often.

good luck
kcj

quote:

We usually apply a bypass type low pressure element in front of a high pressure non bypass unit.

Excellent idea Kevin. I will be using that approach in the future for sure. Users should love the operating cost reduction which should save a lot more than the additional Filter cost over the years.

Completed the initial fill and pressure check today. Some minor leaks but otherwise OK so far.

Bud: "Are the 5um FILTERS at the servo valve manifolds a Non-Bypass type?"
A: Unfortunately not. The subcontractor who made the pump skid seems to have a flip/flop attitude about filtering. "We ALWAYS put a filter after the pump but before the main line, and also at the point of use with servos." (Why filter oil before you send it down a potentially dirty pipe?) "It's just the way it is, the filters will bypass until your oil gets warm." (Why does this sound like a bad idea?)

Newmanite: "I work for a very large mining company and we found the oil coming in from our supplier didnt meet ISO standards"
A: I concur. I checked the bottoms of the oil barrels as I transferred/filtered the oil and noticed a surprising amount of debris.

Luciano: "Pickling is mandatory, otherwise the piping will continuously release rust and scale. Stainless steel is the correct choice for interconnecting piping when there are servo valves."
A: The piping was pickled as received, but that didn't help when the pipes had water in them for 4 weeks. And I tried to get SS at the beginning of the project, which was rejected due to $$. But we are paying that back now!

Luciano: "shooting photo in order to inform the client. Last suggestion regards the servo valves, better choice is when are external pilot line type."
A: I am the client! I have been thinking about converting my valves to external pilot supply. I have found the necessary sandwich block already and one of the MTS manifolds has the non-bypass filtered supply ready to go. In either case I still want to run a filter before the manifold to protect the spool valve and actuator seals.

Kevin J: "If there is water there is likely rust formed. It won't be all removed. It will be flaking off at bad times for months or years. .....flushed a hot water caustic or acid of some sort that removed the rust and flushed at very high Reynolds number."
A: Rust did form - and particles flaking off months from now is my big worry. The piping subcontractor suggested the acid flush, but the hydraulic subcontractor told/convinced everyone it wasn't necessary.

ISZ

Ice Station Zebra, would you believe people are still against having TRAINED/DEDICATED persons Designing, Maintaining and Installing fluid Power Systems????????

Your story is not all that uncommon. I have assisted in many startups and have found your situation to be the norm when it comes to that simple hydraulic circuit.

Then people wonder why the TRAINED/DEDICATED persons from other disciplines are replacing Fluid Power equipment on a regular basis.

The College of Hard Knocks works, SORT OF, but is not the way to go for a system as diverse as Fluid power.

Bud: "...would you believe people are still against having TRAINED/DEDICATED persons Designing, Maintaining and Installing fluid Power Systems????????"

I believe it....and live with the consequences almost every day. I have worked for 4 different off-road equipment manufacturers and only one of them had a dedicated hydraulic expert that any project could tap for help. With my previous employer I was the only person in the engineering dept that truly understood how the whole system worked, and I was JUST the sr. test engineer!

I have a similar issue on one of my current projects where the sr. design engineer (with minimal machine driving experience) is telling me, my test engineers, and my test technicians (each with years of hands-on experience) that our opinions don't matter. He and another newbie designers drove the machine and they think the controls are good.

I have thought several times about taking some advanced fluid power courses. My fear is that I will get stuck doing ALL the hydraulic testing, or I still won't be taken seriously.

-------------------

The really sad part of this whole experience is that I all but handed them a proper design and solutions to the various issues as they arose, but I have been marginalized due to my "lack of expertise." It all comes down to the contractor being "just good enough" with their designs to keep on making money.

ISZ

ISZ,

Kickbacks and inflated egos over-rule common sense for management a lot of times. I just ran across a similar instance where a "hydraulic god"
sold a company 50 Vickers PVM pumps with the wrong shaft seals. In addition to furnishing the wrong seal initially the vendor is selling them a replacement seal for $39.50 ea. I can buy the correct OEM seal from Vickers for $9.20 ea.
Maytag

quote:

We usually apply a bypass type low pressure element in front of a high pressure non bypass unit.

Kevin;
Second thoughts:
How do you protect the Low Pressue Filter from the High Pressure Filter, without a Bypass setup, from blowing its element holder IF the High Pressure Filter happens to get stopped up. Or, am I thinking wrong?????

On critical circuits using Proportional or Servo valves I install a Dual High Pressure Filter with and Open Cross Over valve to switch sides if/when a pressure switch reaches more than 150-250 PSI back pressure.

I also use a 5 Micron filter in an Off-Line setup that changes the circuit volume every 2-4 hours. It is also plumbed with a 3-Way Ball Valve to allow filling the system with oil from a new drum, or other unfiltered makeup oil.

quote:

Kevin;
Second thoughts:
How do you protect the Low Pressue Filter from the High Pressure Filter, without a Bypass setup, from blowing its element holder IF the High Pressure Filter happens to get stopped up. Or, am I thinking wrong?????

The first one in line, closest to pump, is the low pressure drop element with bypass head. typically 3000 psi rated housing, but 75 psi or so element. Second one is the 3000 psi housing, and 3000 psi non bypass element. So if all goes well, the first element does the work and indicates service at less than 75 psi. The second, high pressure, high dollar, element seees very little dirt load. If the bypassing oil plugs the second element, the flow stops, but element does not collapse. We do not have indicators on the second filter, but do have pressure gauges or QC taps before and after it. A few times the elements have reached say 100 psi drop and time to change. ideally there should be indicators on the non bypass filters, but thery weren't available from the vendors we used.
Have done this with Hydac, Schroeder, and Parker filters. Originally, it was a field fix to a woefully undersized filter package (design outsourced because they wanted 'thinking outside the box' ideas.....) Big and bulky, but solved the problems. Worked well enough that I use it standard practice in critical circuits when I can.

Filthy railroad griding environment, thousands of hp in sparks. I have personally done a couple hundred particle tests, and we routinely hold x-14-10 fluid in either oil or water glycol.


kcj