As I often use my excavator (a 2005 HH EH80cs = Kobelco sk80cs) for lifting & holding things, even the small amount of cylinder drift I have in my bucket circuit (about 0.6mm / 5 minutes) is more than the zero I would like. My boom & arm circuits have virtually zero drift because the original equipment lock valves in those circuits are working as they should. Whereas, my bucket & thumb circuits have no lock valves. This is a common design deficiency come to find out. Also, excavators in the US typically do not have original equipment hose burst valves...another common design & safety deficiency in my opinion. Whereas in the UK & Europe, hose burst valves have long been required by law. So, to remedy my problem, it seems that I'm going to have to add a lock valve & hose burst valve to at least my bucket circuit, & possibly add a hose burst valve to both my arm & boom circuit if I want a complete solution. Has anyone added such valves to their excavators, either just lock valves, or just hose burst valves, or combo lock valves-hose burst valves?? If so, please post some details, like brand/model/where is the valve located/what piping or connections were req'd/machine brand-model added to/how has it worked out?
All hydraulic cylinders are designed to drift slightly. I think hose burst valves are somewhat of a new thing for excavators. I've only seen them on machines coming from Europe. My issue with them is that I have not seen any accident reports that show a boom or stick cylinder hose ever burst and cause damage let alone an injury. A hydraulic hose basically has a life cycle of about 6,000 hours if not damaged externally or overheated. Letting hoses get to the point of being able to burst is negligence on the part of the operator and the owner of the machine. At this point I deem burst valves as another expense required by someone not of the industry who thinks they see a potential. Basically, excavators were never meant to be a crane so early on the engineers felt the necessity of load locks was not necessary. Later on the cost of renting crane time to set large pipe meant construction companies could save considerable money on a project if the excavator could lift and set the pipe. Setting 72" concrete pipe with drain channels in the bottoms is a very intense process, especially for the guys in the ditch. I have never seen a lock valve installed on the bucket circuit. All those machines had a quick coupler installed and the buckets were removed before any big picks were attempted. I have installed lock valves on big Komatsu excavators, PC650 and PC1000 size. Those were installed directly on the cylinders, rod side for the stick cylinder and piston sides for the boom. Cats have what are called anti drift valves installed on the house side of the hoses feeding those cylinders. There are two basic ways the valves are operated. Load locks are basically check valves that can be forced open to allow fluid to pass the opposite way. I've seen them operated by pilot pressure from the joystick or by flow from the opposing circuit. I have only seen them available from the manufacturers of the machine.
I only have small machine so burst valves are not applicable to me but here in Aus i think the rules are as follows. If you are on a work site and lifting a object over 1000kg you are required to have burst valves fitted. Most machines have been retrofitted with them no problems but many unhappy people due to the cost. I fitted a pilot operated check valve to my aux circuit as i was experiencing bleed off of pressure causing thumb release objects. I was very unhappy with cylinder creep on my blade but acceptable figures from the manual were a joke so i have just lived with it.
Yep, I agree that they are a joke...that's the point of my request...I want to see if a range of manufactures think they are a joke.
John C....thanks for your info, but I'm more cynical the older I get..,IMO the manufactures don't include such valves because it is more profitable to sell us "idiots" cranes & boom lifts than to make it easy for us to get the maximum out of our excavators!! In my case, Kobelco saw fit to put lock valves in the boom & arm circuits...how much more would it have cost to include one in the bucket circuit?? And as for the example you cite setting heavy pipe, but with the bucket removed, the load is still attached to the quick coupler which is held by the bucket cylinder, so it will still drift.
Did you purchase your machine new? Is your machine gray market? There is no requirement to date in the USA requiring lock valves or hose burst valves that I am aware of. If you know of any please provide the cite and the authority for the requirement. The cost of the additions that I did in the early nineties was twenty thousand dollars plus per machine. Are you saying that cost should be imposed by government on everyone? What about people who only use an excavator for its intended purpose, to dig dirt? Are they to be charged an extra premium because someone thought it was a good idea? The bucket was removed to lessen the weight on the front of the machine and increase the overall lifting height of the load. The bucket circuit would only be carrying the weight of the object being lifted. The boom and stick circuits will also be carrying the boom and stick weight plus the weight of the object. The drift on the bucket cylinder would also only be in a small arc. As far as thumbs go, you are not supposed to be working under a gripped load. Any load with the chance of having people working under it is required to have a positive connection. Excavators are not a problem, try log loaders used in the Pacific Northwest. A new machine can drift an inch of minute and people work under them all the time.