Use and maintenance of progressive distributor

In recent years, centralized lubrication technology has been increasingly used in heavy machinery such as engineering machinery and mining machinery. As a key component in the centralized lubrication system, the progressive distributor has also gradually attracted people's attention. How to correctly use and maintain the distributor is a key issue to ensure the normal operation of the system. This article will briefly introduce the structure, functional principle, basic usage and common fault analysis and troubleshooting of two common progressive distributors.

1 Classification of progressive distributors

The progressive distributor is a device used to quantitatively distribute grease to each lubrication point. It is mainly divided into two types: sheet type and block type.

1.1 Slice Allocator

The sheet distributor is generally composed of 3 to 9 pieces. They are the first piece IE (without plunger), the middle piece ME and the end piece EE, which are assembled by hexagonal countersunk bolts and locking washers, and O-rings are used to seal between the distributor blocks. There is a plunger in each sheet of the middle block to distribute and discharge grease. The diameter and stroke of the plunger determine the displacement of each stroke. The plunger must perform the grease distribution action after the previous plunger has completed the grease discharge action, so that the movement of the plunger can be fully controlled to ensure that the distributor can work continuously.

In Figure 1a, the grease flows in through the inlet of the distributor, passes through all the oil distribution blocks, and reaches the plunger I. The plunger I is pushed to the left, and the grease is discharged from the pressure area on the left side of the plunger to the outlet 1.

After that, plungers II and III are replaced in turn, and the grease is pressed toward outlets 2 and 3. After plunger III is replaced, the grease directly enters the left side of plunger I, pushing plunger I to move right, and the grease is discharged from the pressure area on the right side of the plunger to outlet 4.

Finally, plungers II and III are replaced in turn, and the grease is pressed toward outlets 5 and 6. After plunger III is replaced, the grease enters the right side of plunger I again, and a new cycle begins. As long as grease is supplied to the distributor, the above cycle will continue. However, if one plunger becomes blocked, the cycle will no longer continue.

In order to meet the lubrication needs of large oil lubrication points, the progressive distributor sometimes needs to stack two or more outlets. Each distributor block has two outlets. In order to achieve the purpose of combining the two into one, it is necessary to remove the countersunk screws separating the two sides and screw a locking screw into the outlet on one side to block the oil outlet on that side. In this way, the output of the closed side is directed to the other side, that is, the outlet flow on the other side is doubled (see Figure 3).

1.2 Block Allocator

The block distributor is a smallest distributor group with a block overall design, with 3 to 10 outlets on each side. There is a plunger between each corresponding two outlets to distribute and discharge the grease. The diameter and stroke of the plunger determine the displacement of each stroke. Like the slice distributor, each plunger has two tasks, one is to distribute the grease in proportion, and the other is to control the flow of grease. The working principle diagram of the block distributor is shown in Figure 4, and its plunger action is the same as that of the slice distributor.

2 Use and troubleshooting of progressive distributors

2.1 Use of progressive distributor

Correctly understanding and using the distributor is the key to ensuring the stable operation of the distributor. In actual use, we need to pay attention to two points:

(1) Ensure correct installation.

The connection between the joints and pipelines must be firm and without leakage; during the assembly process of the plate distributor, the environment must be kept clean and tightened with the specified tightening torque. Too loose will cause leakage between the plates, and too tight will damage the O-rings between the plates, thus affecting the use of the distributor.

When installing the distributor, make sure that the distributor plunger is in a horizontal position.

(2) To ensure the quality of grease, use grease strictly in accordance with system requirements.

The fit between the plunger and the oil chamber in the distributor is relatively precise, and the clearance fit tolerance is generally 3 μm. If inferior grease is used, the grease will separate under high pressure (3-4 MPa) during the lubrication cycle gap, that is, the crude oil and the soap base will separate. If the time is long enough, such as more than 7 days, the soap base will solidify in the plunger guide ring groove and the oil supply chamber, which will cause the distributor to be blocked even at a pressure of 30 MPa.

The main reason for this phenomenon is the problem of the grease itself, so it is recommended to use some grease with good fluidity. And use different greases according to different working environments, specifically: use No. 000 lithium-based grease at -30℃～-10℃; use No. 1 lithium-based grease at -10℃～10℃; use No. 2 lithium-based grease above 10℃.

2.2 Fault monitoring and troubleshooting of progressive distributors

2.2.1 Fault Detection

The distributor equipped with a travel indicator is easy to detect. As shown in Figure 5, remove the plunger locking screw 1 and screw in the travel indicator 2. If the indicator pin pops out, it means that the plunger in the outlet moves freely and there is no blockage. Otherwise, it can be determined that the distributor is faulty.

Its working principle is: when the piston 4 moves, the plunger 3 will move to the right, and the indicator pin 5 will be pushed out; once the piston moves to the other side under the action of grease, the indicator pin 5 and the plunger 4 will return to their original positions under the action of the spring 6.

If the indicator is not installed, you can detect it according to the following method. Taking Shantui centralized lubrication and crawler track automatic tensioning system as an example, the detection of the disc distributor is explained.

(1) Remove the main line and start the lubrication pump to determine whether the oil can be discharged normally; (2) Screw on the main line, place the three-way reversing valve on the lubrication side, and then remove the corresponding screw plugs under the distributor oil outlet one by one, and start the pump each time. After the screw plug is opened, if a large amount of grease overflows, it indicates that the piece is blocked. Remove the faulty distributor and mark the piece. (3) If the main distributor is not faulty, check the secondary distributor according to the above method. If the system is large, it is recommended to install a grease nipple on the distributor and use a manual pump for detection.

2.2.2 Troubleshooting

Take out the faulty distributor and troubleshoot it as follows:

(1) Loosen the corresponding screw plug under the oil outlet, push the plunger back and forth (be careful not to push it out). If the plunger moves freely, screw the screw plug back and check the other distributor blocks in turn. (2) Take out the plunger that has been determined to be difficult to move, and check whether there are scratches on the inner hole and surface of the distributor. If the scratches are serious, the distributor needs to be replaced (note: the plungers are not interchangeable). (3) If there are traces of hard grease on the plunger and the inner hole surface, it means that the entire distributor needs to be cleaned. At this time, use a manual oil gun to pressurize the distributor to 20 MPa, and then immerse it in hot water at about 90 ℃. After the pressure drops to 0 MPa, clean it again with oil to completely remove the residual grease. The corresponding oil pipeline should also be thoroughly cleaned. (4) After inspecting and cleaning all the distributor blocks, install them in the previously marked order, pay attention to the correct installation position of the sealing ring, and do not allow defects or protrusions. Check the seals between the first block, the middle block and the last block. To avoid plunger blockage, the specified tightening torque should be used when installing the bolts. (5) Finally, use an oil gun to fill the distributor with oil, check that the distributor is operating normally, then install it into the system and start to check the entire system. The fault detection of the block distributor can refer to the photodistributor. However, it should be noted that once a plunger or its inner hole surface is severely scratched, the entire block distributor cannot be used any more.