As the saying goes: 'Before the army moves, the provisions must be ready.' Before operating a high-pressure plunger pump, it is absolutely essential to add oil, and it must be good quality oil. Oil is one of the 'provisions' for the plunger pump. If you operate the pump without oil, it will produce loud noise, and the connecting rod will quickly seize or even melt, while the crankshaft will suffer severe wear, causing the high-pressure pump to fail within minutes. Therefore, remember to add oil before use！！！

 

 

But what kind of oil should be used for a high-pressure plunger pump? How to choose the right oil grade? Although the oil we usually use seems fine, does it have hidden damage to the high-pressure pump? It's really a headache. Don't worry. Let's listen to the editor's explanation:

 

 

In the previous article, we first looked at small pumps (generally referring to pumps with a flow rate not exceeding 50L/min or pressure below 50MPa). Small pumps should use diesel engine oil (shortened as diesel oil) as lubricating oil. When purchasing, make sure not to choose the wrong type, such as gasoline engine oil (shortened as gasoline oil). Because gasoline oil has lower viscosity and cannot meet the lubrication requirements, resulting in low oil film strength and accelerated wear of friction pairs, which will reduce the service life of the pump in an invisible way.

 

 

Since gasoline oil is unsuitable, we will now focus on the selection of diesel oil. The selection of diesel oil mainly depends on two key parameters: API quality grade and SAE viscosity grade. These parameters are clearly marked on the oil drum, as shown in the example below:

 

 

 

 

One, API Quality Grade

 

 

API stands for American Petroleum Institute, which is the abbreviation of American Petroleum Institute. API classifies diesel oil into quality grades from low to high: CA, CB, CC, CD, CE, CF, CF-4, CG-4, CH-4, CI-4, CJ-4. The later the letter, the higher the oil quality grade. The API grade represents the oil quality level, but it should be noted that this quality grade does not directly indicate the anti-wear performance or oil change interval, but rather represents the 'comprehensive quality threshold' including environmental protection standards.

 

 

Currently, diesel engine oil in China is mainly CF-4, where the "-4" indicates that the oil is suitable for four-stroke diesel engines. CF-4 is used for high-speed direct-injection diesel engines, and its performance in fuel consumption and piston deposits exceeds that of CF. It is particularly suitable for heavy-duty trucks, and small high-pressure plunger pumps generally also use this grade of diesel oil. Compared to CD, CF-4 has more comprehensive performance, and its oil change interval is twice that of CD.

 

 

II. SAE Viscosity Grades

 

 

SAE stands for the Society of Automotive Engineers. SAE classifies engine oil into eleven grades: 0W, 5W, 10W, 15W, 20W, 25W, 20, 30, 40, 50, and 60.

 

 

The first six grades are for winter use and are marked with the letter "W." This type of oil is used in low-temperature environments, and has low viscosity. Therefore, for areas with lower temperatures, oils with smaller numbers should be selected. The lower the oil viscosity, the higher the engine's starting speed; at the same time, the lower the oil's pour point, the easier it is to pump the oil, allowing it to reach the lubrication points more quickly and reducing the time the engine experiences dry friction.

 

 

The last five grades indicate the oil's viscosity at 100°C. The higher the number, the greater the viscosity. Since this type of oil has relatively higher viscosity, it is more suitable for use in high-temperature summer conditions. For areas with higher temperatures, products with higher grade numbers should be selected.

 

 

To adapt to temperature changes, multi-grade viscosity all-season oils have been developed. For example, the designation SAE 15W-40 indicates that the oil meets the winter low-temperature viscosity performance specified by the prefix part of the designation and the summer high-temperature viscosity performance specified by the suffix part. The smaller the number before the "W," the better the oil's flowability at low temperatures, making vehicle startup easier. The larger the number after the "W," the better the oil's viscosity at high temperatures, resulting in stronger oil film strength. This type of oil is generally suitable for use throughout the year.

 

 

 

After introducing these two indicators, let's go back to look at which oil to choose for small high-pressure pumps. First, from the API rating, the quality level should not be lower than CF grade. If a lower grade, such as CD grade, is selected, the oil should be changed every 500 hours, but in this case, it needs to be changed every 250 hours, otherwise the lifespan of the high-pressure pump will be greatly reduced.

 

 

Secondly, the viscosity should not be lower than 40. If the environmental temperature changes greatly, it is recommended to choose multi-grade composite type, and 15W-40 is recommended. Please adjust according to the working environment of the pump. If unsure, please consult us.

 

 

Above we introduced the oil selection for small pumps. Let's continue to talk about how to select oil for large pumps below.

 

 

Large pumps, due to higher flow or pressure, have friction pairs that bear greater loads and crankshafts that experience greater alternating loads compared to small pumps. Therefore, large pumps generally use gear oil.

 

 

Gear oil is divided into two types: one is industrial gear oil, and the other is vehicle gear oil. Which one should we choose for our large pumps? Can both be used?

 

 

III. Industrial Gear Oil

 

 

Let's first look at industrial gear oil, which is classified according to the International Organization for Standardization (ISO) standards. Its quality grades include: L-CKB, L-CKC, L-CKD, L-CKE, etc. For large pumps, heavy-duty industrial gear oil L-CKD is generally selected.

 

 

 

Viscosity is also based on ISO standards, and is classified from low to high as: VG68, VG100, VG150, VG200, VG320, VG460, etc. For large pumps, VG220 is generally selected. If pressure or flow is low, it can be reduced to VG150. Combined with the quality grade, we generally select L-CKD 220. If the load is greater, it is best to choose gear oil with extreme pressure additives (EP).

 

 

Four. Vehicle Gear Oil

 

 

Let's now look at vehicle gear oil, which is similar to the engine oil mentioned in our previous article. Its quality grades also follow API standards, with common grades including GL-3, GL-4, GL-5, etc. For large pumps, GL-5 is generally selected.

 

 

Viscosity is classified according to SAE (Society of Automotive Engineers) standards, divided into seven grades: 70W, 75W, 80W, 85W, 90, 140, 250. The first four are winter-grade oils marked with 'W', as these gear oils are used for winter low-temperature conditions, with lower viscosity. Therefore, for areas with lower temperatures, gear oils with smaller numerical grades should be selected.

 

 

 

 

For example, the designation 80W-90 indicates that the part before the hyphen represents the winter low-temperature viscosity performance, and the part after the hyphen represents the summer high-temperature viscosity performance, making it a multi-grade gear oil. For large pumps, GL-5 SAE 85W-90 gear oil is generally selected.

 

 

Note: Regardless of large or small pumps, if a gear box is used, it is recommended to add CKD 220 gear oil. Additionally, for small pumps used to transport high-temperature liquids, it is also recommended to add CKD 220.

 

 

To save customers the trouble of searching for suitable oil, our company has specially commissioned a batch of oil designed for high-pressure pump plungers. This custom oil provides high-pressure plunger pumps with effective lubrication, wear resistance, sealing protection, and high- and low-temperature performance. With this oil, the oil-change interval can be extended to 500 hours, avoiding hidden damage to high-pressure pumps caused by unsuitable oils.

 

 

A good pump deserves good oil. When purchasing a pump, bring along a bucket of oil, and you will no longer worry about oil. For pricing and details, please consult our sales representatives.