The sleeve compensator, also known as a tubular expansion joint, is a compensation device used in hot-fluid pipelines. It is primarily designed to absorb and compensate for axial thermal expansion displacements that occur after straight pipelines have been installed. This type of compensator is directly installed in pipelines that convey non-corrosive fluids—whether flowing in one direction or multiple directions. The sleeve-type compensator is widely used in pipelines across various industries, including urban heating, metallurgy, mining, power generation, petrochemicals, and construction. It mainly consists of a sleeve (core pipe), an outer casing, and sealing materials.

Structural features

It mainly consists of a sleeve (core tube), an outer shell, and sealing materials. It is used to compensate for axial expansion and contraction of pipelines as well as axial rotation at arbitrary angles. With its compact size and large compensation capacity, it is suitable for media such as hot water, steam, and oil-based fluids. Thermal expansion is compensated through the sliding motion of the inner sleeve relative to the outer sleeve.

The inner sleeve of the sleeve-type compensator is connected to the pipeline and employs a high-performance, self-pressurizing dynamic sealing principle and structure. It can freely slide within the outer casing as the pipeline expands or contracts, thereby meeting the sealing requirements of any type of pipeline. A new synthetic material is used for the seal between the outer casing and the inner sleeve; this material is highly resistant to high temperatures, corrosion, and aging, with an applicable temperature range from -40°C to 150°C, and even up to 350°C under special conditions. This design ensures both axial sliding and prevents leakage of the medium inside the pipe.

The sleeve-type expansion joint is equipped with an anti-pull-off device that ensures it won't be pulled apart even when fully extended or contracted, thereby significantly enhancing the overall safety of the pipeline network.

The sleeve-type expansion joint is suitable for media with engineering pressures ≤ 2.5 MPa and media temperatures ranging from -40℃ to 600℃.

The sleeve-type compensator employs a new type of sealing material—the flexible graphite ring—which features high strength, a low coefficient of friction (0.04–0.10), resistance to aging, excellent performance, and ease of maintenance.

The sleeve-type compensator boasts a long service life, with a fatigue life comparable to that of the pipeline itself. Its sliding surfaces undergo special treatment, providing excellent corrosion resistance even in environments such as saltwater and saline solutions—more than 50 times better than that of austenitic stainless steel. Moreover, if the sealing performance weakens over the years due to wear, the flanges can be re-tightened to restore the seal. Alternatively, the bolts can be loosened, the compression ring removed, and one or two additional sealing rings installed before re-tightening the compression ring and continuing operation.

Sleeve-type expansion joints have no requirements regarding chloride ion content and are particularly suitable for systems where the chloride ion concentration in the medium or surrounding environment exceeds the standard.

The directly buried sleeve-type compensator can be directly buried underground, eliminating the need to install maintenance wells during installation and resulting in lower project costs.

Type

Sleeve-type expansion joints come in two types: unidirectional and bidirectional. The bidirectional type is characterized by the fact that, regardless of which end of the expansion joint the medium flows into, the sliding sleeves at both ends of the expansion joint always slide freely, thereby achieving bidirectional compensation and increasing the compensation capacity.

Common product series

ZHTTB-B Series Elastic Sleeve Compensator

ZHZTB-B Series Directly Buried Sleeve Compensator

ZHN-H-I Series Thrustless Sleeve Compensator

ZHN-H-II Series DC Thrustless Sleeve Compensator

ZHYTB-A Series Disposable Sleeve Compensators

ZHSLT Series Dual-Flow Sleeve Compensator

Installation method

General sleeve

1. The sleeve-type compensator should be properly stored during installation to protect it from exposure to sunlight, rain, and contamination by sand and dust.

2. During installation, verify that the model and specifications of the compensator match the design. The product surface should be free from defects such as dents, indentations, or severe rusting that could affect product quality.

3. If the overall length of the finished single-use compensator matches the sample, there is no need to further stretch or compress it. However, if the installation markings on the expansion joint pipe have changed, you should adjust them accordingly before proceeding with installation.

4. For bidirectional non-thrust compensators, the medium flow direction indicated in the simplified diagram must be strictly followed during installation. When the medium is steam, this precaution is taken to prevent air pockets from forming inside the compensator. To ensure that the compensation amounts in both directions are equal, the bidirectional compensator must be positioned exactly midway between two fixed points during design.

5. The pipe sections welded to both ends of the compensator must undergo beveling treatment. After welding, a hydrostatic pressure test shall be conducted as required (during the pressure test, the bolts at both ends of the packing chamber should be tightened until no leakage is observed). Twenty-four hours after operation begins, the bolts at both ends of the packing chamber must be tightened again.

6. To ensure that the pipeline remains free from lateral displacement and undergoes only axial expansion and contraction, install guiding supports on the side of the expansion joint. When both ends of the compensator experience axial displacement, guiding supports should be installed on both sides to ensure that the axial displacement does not cause the compensator’s eccentricity to exceed ±1 degree.

7. The thermal insulation and waterproof structure of the compensator can be the same as that of the pipeline, but it must not impose any restraining forces on the expansion joint section.

8. Special circumstances will be discussed separately.

New sleeve-type

1. When installing the compensator, first check whether its specifications match the order details.

2. The sliding sleeve of the unidirectional compensator should be installed on the inlet side of the medium.

3. The pipe sections welded to both ends of the new sleeve-type expansion joint must undergo beveling treatment. After welding, a hydrostatic pressure test shall be conducted in accordance with acceptance criteria, at a pressure 1.5 times the working pressure. During the pressure test, if any leakage is detected in the sealing device, the bolts should be tightened evenly until no leakage occurs.

4. The compensator shall be installed along the pipeline’s centerline, with an eccentricity exceeding 1% to prevent excessive friction during operation and to ensure proper sealing performance.

5. Guided sliding supports should be installed near the compensator on the pipeline to prevent lateral displacement.

6. Pay attention to protecting the sliding surfaces; absolutely avoid any scratches or corrosion.

7. The outer sleeve of the bidirectional compensator shall be supported by fixed supports and kept concentric with the pipeline; the compensation distances on both sides should be approximately equal.

8. The compensator can be installed at its maximum length under all temperature conditions, without the need for pre-stretching or pre-compression (the maximum length is the product’s length as shipped from the factory).

Advantages of sleeve compensators

1. The sleeve compensator boasts a long service life, with a fatigue life comparable to that of the pipeline itself. Its sliding surfaces have undergone special treatment, giving them excellent corrosion resistance even in environments such as salt water and saline solutions—more than 50 times better than that of austenitic stainless steel. Moreover, if the sealing performance weakens over the years due to wear, the flanges can be re-tightened to restore the seal. Alternatively, the bolts can be loosened, the compression ring removed, and one or two additional sealing rings installed before tightening the compression ring again, allowing the compensator to continue functioning effectively.

2. Sleeve compensators have no requirements regarding chloride ion content and are particularly suitable for systems where the chloride ion concentration in the medium or surrounding environment exceeds the standard.

3. Sleeve compensators come in two types: unidirectional and bidirectional. The bidirectional type is characterized by the fact that, regardless of which end of the compensator the medium flows into, the sliding sleeves at both ends of the compensator always slide freely, thereby achieving bidirectional compensation and increasing the compensation capacity.

4. Direct-buried sleeve compensators can be directly buried underground, eliminating the need to install maintenance wells during installation and resulting in lower project costs.