What is the reason for the failure of the double-wall corrugated pipe closed water test?

In municipal drainage engineering, the closed water test of double-wall corrugated pipes is a key link in testing the sealing of pipelines. However, the failure of the test occurs from time to time, which not only affects the progress of the project, but also may cause hidden dangers of leakage. Combined with construction practices and industry standards, the failure of the closed water test is mainly caused by the following three types of problems:

1. Pipeline socket installation defects

1. Interface sealing failure Socket installation is not in place is the most common problem. For example, the socket of DN300 pipeline should be inserted into the socket depth of not less than 120mm. If the actual insertion depth is only 80mm, the rubber ring will not be fully fitted and a leakage channel will be formed. In addition, the offset of the installation position of the rubber ring (such as the third ripple not embedded in the socket) or the use of non-matching sealing rings (such as SN8 pipeline misuse SN4 sealing ring) will destroy the sealing performance.

2. If the crowbar is used to forcibly push the pipeline connection during the construction of the interface damage, it is easy to cause scratches on the inner wall of the socket or depressions on the outer wall of the socket. A project once used mechanical brute force to connect the DN600 pipeline, resulting in a 3mm deep scratch at the interface, and the water seepage exceeded the standard by 3 times during the closed water test.

2. Improper control of the construction process

1. The foundation treatment is not up to standard and the trench is not backfilled according to the specification after overdigging, which is the main reason for the settlement of the pipeline. For example, the bottom of a trench in a project was overcut by 30cm, only backfilled with plain soil and the compaction was less than 90%. During the closed water test, the pipeline appeared 15mm uneven settlement, and a 0.5mm crack was generated at the interface.

2. Backfill quality defects The axillary corner of the bottom of the pipe is not filled with medium coarse sand, or the backfill soil contains stones with a particle size greater than 50mm, which will destroy the force balance of the pipeline. A project was mixed with concrete blocks in the backfill, resulting in local compression and rupture of the pipeline. The water leakage during the closed water test reached 1.2L/(min · km), far exceeding the allowable value of the specification by 0.3L/(min · km).

3. Materials and test preparation issues

1. Pipe quality defects Some manufacturers in order to reduce costs, the quality is not up to standard.

2. Test operation is not standardized If the pipeline is not fully soaked before the closed water test, it will affect the test results.

Water Closure Test Qualified Operation Guide

Prepare

Before the test

Use 1:3 cement mortar to seal the nozzle, maintain for more than 3 days

The water level rises to 2m above the top of the pipe, if the upstream well depth is insufficient, the height of the wellhead shall prevail

Check the appearance of the pipeline and repair the visible cracks

Test process Control

Soaking time is not less than 24 hours

Water seepage measurement time 30 minutes

Measured water seepage "GB50268-2008" Allowable value (such as DN300 pipe allowable water seepage 0.3L/(min ・ km))

Leakage repair plan

Slight leakage: use HDPE electrode hot air welding, with geotextile wrapping

Serious damage: remove the damaged section, replace the new pipe and reconnect 117277984 Interface problem: remove the interface, replace the sealing ring after cleaning up the debris

Hubei AD Building Materials: Professional double-wall corrugated pipe solution provider

As the source manufacturer of Hubei HDPE double-wall corrugated pipe, Hubei AD Building Materials Co., Ltd. strictly implements the ISO9001 quality management system, and the product ring stiffness reaches SN8 level far exceeding the industry standard. For the closed water test problem, the company provides:

Technical support: free welding training and closed water test guidance

Emergency service: 24 hours response, 48 hours to arrive at the site to deal with leakage

Quality assurance: pipe quality assurance 50 years, closed water test unqualified unconditional return

If you need technical consultation or product procurement, please call the service hotline: 17399989993.