Assembly and sealing techniques of middle and low pressure hydraulic cylinder

Hydraulic cylinder pressure in the following 16Mpa is known as the middle and low pressure hydraulic cylinder, it is widely used in engineering machinery, such as bulldozer, loading machine, flat machine, crane and so on. This kind of hydraulic cylinder seal parts at home and abroad often used oil resistant rubber as the material, such as nitrile rubber, rubber cloth and ternary nylon and rubber folder, and other. Hydraulic cylinder seal inside and outside the two parts: the outer seal portion including between the cylinder and the cylinder head static seals and cylinder head guide sleeve and piston rod dynamic seals, the second is to ensure that the hydraulic cylinder does not produce leakage; inner seal part comprises a piston and cylinder diameter between the dynamic seal and the piston and piston rod connected at the static seals. The performance status of these seals is the key to decide whether the hydraulic cylinder can reach the design capability. There are 16 MPa grade engineering hydraulic cylinder common cylinder head structure type welding flange connection, Neckar key connection, threaded connections and clamp spring connecting etc. 4.

Below the hydraulic cylinder seal assembly of the relevant requirements as follows:

(1) sealing cylinder and cylinder head

In order to ensure the static sealing performance between the cylinder and the cylinder head, in addition to the choice of reasonable stationary fit clearance, suitable O-ring outside, the best in O-ring by squeezing the side fitting nylon backing, which can improve the sealing ring of the bearing capacity, increase the flange bolts or cylinder cover screw preload, anti stop work due to the vibration loosening, leads to static sealing surface relative to the wrong move and wear, resulting in damage to seals.

(2) the sealing piston rod and cylinder guide sleeve hole

The piston rod and cylinder clearance guide sleeve is not up to the requirements of the original design

Because of the long-term use, the guide part of the wear out of the round, strain, gap or gap oil film seal damage and so on are the main factors causing the leakage of piston rod. In this condition, even if the new seal, will produce the symptoms of hydraulic oil leakage from the piston rod.

All sealing parts of the assembly shall be in accordance with the standard.

Y - shaped, V - shaped, U - shaped, Yx - shaped sealing parts, such as the quality of its appearance can not be concave and convex, impurities, bubbles, scratches and burr flying edge, etc., the dust ring is loaded into the piston rod, otherwise should be replaced by a new.

The surface layer of chrome plated piston rod without shedding or serious uneven.

The bending deformation of the piston rod should be in accordance with the design requirement. The linear degree of the piston rod surface is less than 1000mm in 0.3mm, which can be checked by the instrument. Construction site inspection, can not install sealing the cylinder head guide sleeve coated hydraulic oil into the piston rod on, then full stroke reciprocating sliding and rotation, feel gapless as appropriate.

(3) the cylinder head and piston rod assembly

Before the assembly using gasoline or cleaning oil (it is strictly prohibited to use diesel or kerosene cleaning all fittings, and the residues of the cylinder inner ring grooves of thick cloth or glabrous cotton cloth to wipe clean with, into the seal, and shall be in the sealing piece and a guide sleeve contact surface coated with hydraulic oil (a strict ban on stem assembly). Cylinder head into the piston rod best using loaded assembly from the horizontal direction or the vertical direction, ensure that are concentric, with hard sticks gently tap into. Conditions can also be processing a guide sleeve, and nut is screwed in or with a hardwood into, both to protect the surface of the oil seal, and ensure the cylinder cover can be successfully loaded in the cylinder.

(4) piston seal assembly

Assembly must check the back of the guide ring is worn, if the wear should be replaced, so that the piston and cylinder liner can ensure the normal clearance between the hole. Guide ring is also known as wear-resistant ring, often from tin bronze, PTFE, nylon 1010, MC nylon and poly formaldehyde, etc. with oil resistance, wear resistance, heat resistance and low friction coefficient of material. Non metal material guiding ring incision width with the guide portion of the increase in the diameter of the increase must leave expansion, to prevent serious phenomena of scuffing of cylinder bore in the high temperature and high pressure work, cause the cylinder is discarded. The fit clearance between the piston and the piston rod is generally small, and if the gap is too large, it should be replaced or matched with the piston assembly. The piston head of the card key connection should be able to rotate, no axial clearance. The threaded connection to have enough pre tightening torque, and cotter pin, a locking spring or radial fastening screws lock, but cotter pin and a fastening screw overhanging section should not be too long, lest and cylinder bottom for inner hole part of the buffer action of the collision caused by the use of the cylinder or piston head off serious fault occurs in the process.

(5) assembly of cylinder and piston rod assembly

Assembled piston, piston rod, a cylinder head and seal assembly of a whole composition, how to make the piston head can correct, safe, non-invasive into clean inside the cylinder is an important link to ensure the hydraulic cylinder not working within the vent. The piston and cylinder head structure of different connection modes, different assembly process.

Cylinder tube with flange connection

When the cylinder barrel end hole chamfering part at no bumps to bite, piston surface has been coated on the hydraulic oil and the cylinder bore and piston concentric can piston assembly is mounted. Cylinder static seal at incision of backing should apply grease or industrial Vaseline, and guarantee that the back lining does not eject the dislocation, to to the specified torque and uniform symmetrical fastening cylinder head bolts.

The button inside the cylinder head connection

Assembly must be within the cylinder surface of the card key to fill and level up, in order to ensure the cylinder surface of the inner circle block, piston seal not damaged, two kinds of commonly used methods: factory job or under the conditions, processing block 3 clasp, the fill card slot, to be the piston and cylinder head guide sleeve into the cylinder, then the three pieces of cards ring out, and then into the card key. Need to be reset after the cylinder head guide sleeve mounted on the positioning ring, Kahuang etc.