two stage hydraulic pump adjustment made in china

The drop from high flow/ low pressure to low flow/high pressure is usually adjustable from 400-900psi. I think a few of the cheap china pumps might not have a adjustment and are preset. Barnes and haldex,and their china clones will have and adjustment. I would suggest adding a pressure guage before trying to adjust anything. If you dont know where your at (pressure wise), how can you know where your going.

Another thing could be with your 4in bore cylinder, your pressure isnt building up enough during split to need the low flow/high pressure. You need a guage to check this. Your engine size is bigger than original and probably isnt bogging down any when the pump loads up. I have a 5in bore cylin with a 28gpm pump and the shift pressure is around 900psi. I dont think I have ever had my pump drop into high pressure either. Your 4in bore cylinder at 900psi is about a 5 1/2ton splitter, and 19.5tons at 3000psi , My 5in bore cyl at 900psi is almost 9tons and 29 1/2ton at 3000psi. If you are splitting soft, easy to split wood, you might never see your pump shift into the high pressure side of the pump. Dont be misled by the tonnage advertisements of store bought splitter, My splitter would be considered a 34-37 ton splitter by some manufacturers. You dont neccesary need the that much tonnage to split wood. Many folks split wood with a 5ton splitter.

In this article I would like to throw in my modest opinion about non-original spare parts - a frequent discussion topic among folks involved in the business of hydraulic pump and motor overhauling.

Although workshops can"t repair pumps without spare parts, they can choose where to buy the spares, and this choice is the key factor that defines how much money they make and how much "overhauling quality" they deliver. With so many suppliers and resellers of non-genuine replacement parts for hydraulic pumps and motors popping up every day, choosing the right "economic" supplier has become all but an easy task involving trial and error overhauls, pissed-off mechanics, pissed-off customers and even forever lost contracts and clients.

A mechanic, for example, being the person who shoves the parts into them pumps and motors, will always prefer genuine replacement parts over any aftermarket ones for one simple reason - they are easy to work with, they always fit and require no "finishing touches" - ergo his work is faster and simpler. Genuine parts last long and are hardly ever faulty, which makes the testing and adjustment procedures safer and reduces the risk of having to re-open overhauled units to a minimum. A mechanic doesn"t care about how much they cost because he"s not the one paying for them.

The truth lies, as always, in the golden middle, and I, personally, came to the conclusion that although most of the times you do get what you pay for, this doesn"t mean that you can"t get a bargain for a penny every once in a while, so a sound overhauler keeps his eyes and mind open and uses both genuine and aftermarket parts in a combination defined by his trial an error experience and the pump/motor application demands. This approach is sound because even in pre-recession years there were hydraulic equipment owners who actually preferred aftermarket to genuine in the pursuit of cutting down overhaul expenses. So, some clients will want the genuine quality, and some will want the lower price - and in order to satisfy both you, naturally, have to be able to serve both, but - if your goal is to deliver quality repairs, aftermarket part suppliers should be chosen with a cool head and on the basis of quality, not price!

OK, you say, so I am a hydraulic equipment owner, and I"ve got this excavator pump to repair, how do I know if I am going to be scammed with them Chinese spares? Well, there is no simple answer to this question...There is an opinion that if an overhaul is backed up by warranty than you"re on the safe side, no matter what parts were used - this, unfortunately, is not entirely true, because if you"re the unlucky hydraulic pump owner caught in the "error" stage of the new supplier trial and error validation process, you can get two different answers and two very different bills depending on how honest the company you are dealing with is. An honest workshop will admit their fault and try to correct the mistake as fast as they can, and if you are not the first-time customer you might even get the - "sorry about that, dude, the parts"re all **cked up..." confession, while a less candid workshop will give you the standard "commission errors committed by non-qualified personnel plus hard particle contamination in conjunction with the inappropriate oil temperature and deficient system design" excuse, and make you pay for their poor part supplier choice. So I"d say that warranty alone isn"t a guarantee, and would cast my vote for warranty combined with transparency - if a workshop has good experience with their non-genuine spare parts supplier - they won"t be ashamed to admit that the parts are not original.

Now, a separate word must be said about Chinese suppliers of spare parts for hydraulic pumps and motors. There are hundreds of companies in China that will sell you spare parts for almost any existing brand, with the quality ranging from superb to unacceptable and even ridiculously unacceptable. However with most suppliers (and especially resellers) the fact that you have received a batch of supreme quality spares doesn"t guarantee that you will get the same quality in the next batch. So if you ever decide to "go oriental" - be prepared for nasty surprises! (At least that was the situation at the moment of writing - December 2011).

My calling is more technical than commercial, therefore I am mainly interested in the quality of the spares rather than their price or where they come from - so please, don"t bother asking me for a list of "unofficially approved" Chinese suppliers of cheap yet extremely high quality spare parts for hydraulic pumps and motors - I won"t provide it because I frankly don"t have it! We do use some aftermarket spares from China, we did have our share of mishaps and disappointments with Chinese made parts, and our initial "Hurrays" got eventually replaced by "Boos" for most of them. Since our policy has always been to never let a client pay for a breakdown caused by a low quality part, a couple of lessons "learned the hard way" taught us that in most cases (not all, though) using Chinese spares in hydraulic pumps and motors is like using bathroom soap for filling cakes - looks and smells nice, yet still tastes like crap...

Control: Push Button Stop/ Start, Lever Valve Action - Control lever forward: Pump into hose A / Control lever backward: Returns to reservoir on hose A

Electric hydraulic pumps are pray coating, anti-corrosion, pollution-resistant, durable. Lightweight and compact design make it easy to be moved. Double speed pump design, with the high flow in low pressure. The actuator can be fast moved on no-load status.Internal high and low pressure automatic reversing valve and external adjustable pressure valve to make it easy to calibrate the working pressure and avoid the over load. Motor starter has the function of preventing overload, overheat and leakage. The pump can be matched with both double acting and single acting cylinders. Choosing the solenoid valve electric hydraulic pump, remote operation can be realized.

The electric motor to drive a hydraulic pump is normally sized to provide 13% more electrical horsepower than the hydraulic horsepower required in the system. In the example below, the amount of electrical horsepower can be found to drive a 100 GPM pump with a maximum pressure of 5000 PSI.

Many hydraulic systems do not require full pump volume at maximum pressure. On presses for example, high flow is need to close the press however, once contact with the part is made, high pressure is needed, not high volume. A horsepower control valve (HCV) is frequently used to automatically reduce the pump volume when a preset pressure is reached. Once the setting of the horsepower control is reached, the pump volume will be inversely proportional to the pressure. This means that if the pressure increases 20%, the pump volume is reduced by 20%. This maintains a constant current draw of the electric motor. Let"s say that the horsepower control in the previous system is set at 3000 PSI. We can now find out how much electrical horsepower is required to drive the pump:

If the pressure were to build 10% to 3300 PSI, the pump volume would drop 10% to 90 GPM, maintaining the electrical horsepower at or near 200. If the horsepower curve is linear then the pump would deliver approximately 60 GPM to the system when the pressure is at the maximum of 5000 PSI.

If the horsepower control valve is set too high, the electric motor can trip out. If the valve is set too low then adequate volume may not be available at lower pressures. What prompted this article was a call I received yesterday from an Oriented Strand manufacturer who had installed a new pump on their press. It was one of four high pressure pumps used on the press. The press was taking too long to build pressure and reach the desired distance setpoint. When the current was checked on the new pump it was found to be considerably lower than the three existing pumps. Adjusting the horsepower control valve allowed the pump to deliver a higher volume of oil at a higher pressure.

Variable-displacement pumps are used in hydraulic systems where the flow requirements vary. This usually means the system has several actuators and, depending on the current cycle of the machine, the number of actuators moving at a given time will fluctuate. The most common type of variable-displacement pump is the pressure-compensating pump.

Pressure-compensating pumps are designed to deliver only the amount of flow required by the system to maximize efficiency and avoid heat generation. The compensator is adjusted to a pressure somewhat higher than that required to move the system’s heaviest load.

A pressure-compensating pump will deliver its maximum flow until the system pressure reaches the compensator setting. Once the compensator setting is reached, the pump will be de-stroked to deliver only the amount of flow that will maintain the compensator setting in the line.

Whenever more flow is demanded by the system (such as would occur when an additional actuator begins to move), the pump will increase its stroke to meet the new flow demand. Whenever the system flow needs to decrease (such as when one or more actuators are stopped), the pump stroke is reduced.

When the system is stopped completely, the pump stroke is reduced almost to zero. It will stroke only a very small amount or whatever is required to maintain the compensator setting in the line, overcoming any system bypassing or leaks. While a pressure-compensating pump is efficient, the standby pressure remains high.

Adjusting a pressure-compensating pump is quite simple. With all flow blocked and the system idle, the compensator valve is adjusted to the desired pressure. However, some pressure-compensating pumps have two valves mounted on the pump body.

The two adjustments can look nearly identical. This type of pressure-compensating pump is called a load-sensing pump. The second adjustment is called either a “load-sensing” valve or “flow-compensator” valve.

A load-sensing pump is designed to reduce its pressure to a much lower standby level whenever the system is idle. This can conserve energy and reduce heat and wear in systems that spend a significant amount of time in an idle condition.

The two separate pressure adjustments allow setting the compensator valve to the required maximum system pressure and the load-sensing adjustment to a much lower standby pressure.

Whenever the system is moving a load, the high-pressure adjustment limits the system pressure. For instance, as a cylinder is extended, pressure in the system will build as necessary to move the load. Eventually, the cylinder reaches the end of its stroke, and flow is blocked.

Most load-sensing systems have a pump-loading directional-control valve of some sort that can place the system in an idle condition until it is necessary to move another load. When the pump-loading valve is shifted, the system pressure drops to the much lower load-sensing valve setting.

A load-sensing valve usually is smaller than the compensator valve and typically mounted directly on top of the compensator. The compensator valve is closer to the pump. The load-sensing valve is factory preset and normally does not need to be adjusted during the initial pump setup. In most pumps, the factory preset is approximately 200-300 pounds per square inch (psi).

The most common reason to adjust a load-sensing valve is because someone unfamiliar with the pump has mistakenly attempted to set the maximum system pressure by adjusting the load-sensing valve instead of the compensator. This not only can result in unstable system pressure but in some cases can also void any warranty on the pump.

A typical configuration of a pressure-compensating pump is shown in Figure 1. A pump-loading valve is used to determine whether the system is idle or prepared to move a load. The pump-loading valve is de-energized whenever the system is idle.

Pilot pressure on the left-hand side of the load-sensing valve is then released to the tank. The pilot line on the right-hand side of the load-sensing valve is connected to the pressure line at the pump outlet. System pressure shifts the load-sensing valve and directs pressure to reduce the pump stroke so that system pressure drops to the load-sensing setting of 300 psi, as illustrated in Figure 2.

When a load is to be moved, the pump-loading valve is energized. This directs pilot pressure to the left side of the load-sensing valve, keeping it from shifting. System pressure shifts the compensator valve to de-stroke the pump exactly the amount necessary to limit system pressure to the compensator setting, 3,000 psi as shown in Figure 3.

To make the pressure settings, always adjust the load-sensing valve first. The pump should be deadheaded by closing the manual hand valve. With the pump-loading valve de-energized, pressure will build only to the current setting of the load-sensing valve. Adjust the load-sensing valve to the desired pressure.

Once the load-sensing valve is set, energize the pump-loading valve. System pressure will then build to the current compensator setting. Adjust the compensator to the desired setting. Open the manual valve, and the system can be placed back into service.

Jack Weeks is a hydraulic instructor and consultant for GPM Hydraulic Consulting. Since 1997 he has trained thousands of electricians and mechanics in hydraulic troubleshooting methods. Jack has...

Thanks to the radial configuration of its small piston pump elements, the radial piston pump is suitable for generating pressures of up to 700 bar. The elements are arranged in multiple rings, which enables the pump to generate higher flow rates with lower pulsation.

The type-LP pumps are valve-controlled, alternating plunger pumps based on the principle of a pneumatic-hydraulic pressure amplifier. Depending on the transmission ratio (surface ratio – hydraulic piston : pneumatic piston), they can attain hydraulic pressures of up to 630 bar at an air pressure of 6 bar, for example.

If you want to combine speed with powerful movements (rapid traverse – creeping), a compact, dual-stage system is the right choice for your application. A gear pump feeds the system with a high delivery flow at low pressure, and a radial piston pump with high pressure but a low delivery flow. The two pumps and flanged directly onto one another to form a compact unit.

The pump elements form the basis of the radial piston pump. When working in extremely tight spaces, they can also be installed separately. This allows the user to build almost any form of high-pressure system imaginable.

The double pump element type DMPE integrates both a low-pressure and a high-pressure piston. As soon as the low-pressure limit is reached, an in-built valve depressurises the low-pressure piston. Multistage pumps which can be adapted to a variety of demands can be designed by the user.

The valve bank type VB consists of several directional seated valves, connected in parallel. As a ball valve, it is tightly sealed with zero leakage in the closed state. 2/2, 3/2, 4/2, 3/3 and 4/3 directional seated valves can be provided. The valve bank can be fitted directly onto hydraulic power packs with connection blocks.

Pressure-limiting valves reliably protect the hydraulic system from being subjected to excessive system pressure. The MV type comes in a wide range of designs and pressures of up to 1000 bar for the high-pressure range.

The RHC-type check valve is available as an insert valve in 6 different sizes. Thanks to its range of pilot ratios and optional hydraulic release, it can be used in similar applications to load-holding valves.

The KA-type compact hydraulic power pack is designed for intermittent operation. Its housing contains a tank, an oil-immersed motor, and a high-pressure or dual-stage pump. Valve banks of types BA and VB can be mounted directly on it to form an incredibly compact system solution.

The compact hydraulic power pack type HKL enables you to work in both intermittent and continuous operation. Here too, it is possible to mount valve banks of types BA and VB directly on the power pack. This type of power pack is used primarily for hydraulic tools.

With a balance disc, the axial force is completely compensated; no axial thrust bearing is required. Due to the smaller balancing leakage flow, total efficiency of the pump is higher than the pump efficiency with the balance drum design.

While Forum’s portable hydraulic hand pumps assist many types of low- and high-pressure testing, they are especially well-suited for oilfield uses such as removing cores from core barrels, testing valves, fittings, tubing and casing. They are also effective for setting cement retainers where mud or cement pumps aren’t available, or as actuators for hydraulically-controlled valves and systems.

Manufactured for strength and durability, these lightweight, two-stage force hydraulic pumps are small enough for your crews to carry them through manholes/restricted spaces and to remote locations for testing. Operating equally well with hydraulic mediums of water or oil, you can change between the low-pressure and high-pressure ranges within seconds.

For high-pressure operation, the pumps feature flexible discharge hoses manufactured with a tough, smooth exterior over a wire-braided reinforcement. Oil-resistant and durable, the hoses contain compact connectors and extra-heavy hydraulic reducers for easy connection to the pumps.

Hydraulic cylinders provide the unidirectional force required to power your industrial equipment for heavy lifting. Telescopic hydraulic cylinders, which are ideal for dump trailers and platform truck trailers, give the extended stroke lengths required for a range of versatile purposes. When purchasing telescopic hydraulic cylinders, consumers are frequently faced with the decision between single-acting and double-acting hydraulic cylinders. Learn what distinguishes the two types of telescopic cylinders to determine which cylinder is appropriate for your high-power hydraulic requirements. The hydraulic cylinder is the industrial world’s workhorse. Learn about the benefits and drawbacks of single and double-acting hydraulic cylinders. The function of your cylinder decides whether you should choose a single-acting or double-acting hydraulic cylinder. Single-Acting Hydraulic Cylinder Single-acting cylinders generate force exclusively in one direction, whether it is a push or pull action. These are also referred to as “plunger” cylinders. They are utilized in lifting operations where hydraulic pump pressure stretches the hydraulic cylinder and a mass or spring retracts it. Single-acting cylinders contain only one port through which the hydraulic pump’s pressurized oil passes. This causes the piston to extend in one direction, compressing the piston’s spring. After releasing the air via the cylinder port where it entered, the spring