Maintenance and repair technology of plate heat exchanger

(1) Maintenance content

1) Intermediate repair content

① Dismantle the inlet and outlet pipes and clean up sundries;

② Check the rubber lining of inlet and outlet pipes to ensure that there is no crack or damage;

③ Check and measure the bolt preload and the overall dimension of the plate.

2) Maintenance contents

① Including intermediate maintenance.

② If the heat exchanger is scaling, it shall be removed for cleaning, or another on-line chemical cleaning of the pipeline shall be carried out.

③ Check the elasticity and compression deformation of the sealing strip with a magnifying glass and replace it if necessary.

④ Check the deformation of the heat transfer plate.

⑤ Check the heat transfer plate for corrosion, perforation and other defects.

(2) Maintenance technology

1) Before disassembling the plate heat exchanger, measure and record the overall dimensions of the compressed plate heat exchanger.

2) Remove the sealing rubber strip. In order to prevent the thread cutter from breaking the plate, the liquid nitrogen quenching method can be used to quench and deform the rubber strip, and then tear it off.

3) Remove adhesive residue from the sealing groove.

4) Inspect the heat transfer plate for cracks or perforations by light method or penetration method.

5) Wash the dishes with clean water.

6) Reassemble.

7) Air tightness and hydrostatic test.

(3) Reassemble

1) Before assembly, clean the sealing groove with acetone, apply 401 adhesive and stick the sealing strip in a horizontal position.

2) Each group of 50 plates with sealing strips shall be pressed with 20-30mm steel plate to keep the ambient temperature within 30-35 ℃ for 24h.

3) After lifting the parts, gently lift the glands at both ends and put on the fixing bolts.

4) Tighten the bolts evenly with a torque wrench.

5) The total compression of the measuring plate after assembly can generally be calculated by the following formula:

L=（ δ 1+ δ 2）n+ δ two

Where l - total length of plate bundle after fastening, mm;

δ 1 - plate thickness, mm;

δ 2 - thickness of the sealing strip after compression (generally 80% of the uncompressed thickness, the compression amount is 20%, and the compression amount does not exceed 35%), mm;

N - number of heat transfer plates.

6) Install the inlet and outlet inner bushings. δ

7) Full pressure test. Firstly, plug the population pipe of the fluid channel on one side of the plate and fill it with water, then add a blind plate with a short exhaust pipe on the outlet pipe of the working medium channel on the other side of the plate, and install a pressure gauge on the pressure test side. After water filling, pressurize with a manual pump with 1.25 times the working pressure and maintain the pressure for 30min. There is no pressure drop when the outer pipe is connected.

8) Unilateral pressure test. In order to ensure no internal leakage, the method of one-sided pressure test can also be adopted, that is, the tested side is filled with water, the other side is not filled with water, and the test pressure is the working pressure. It is qualified if the pressure is not reduced for 20 minutes. One side pressure test is generally not conducted for plate heat exchanger to prevent large deformation of plate heat exchanger and damage to plate heat exchanger and sealing strip.

9) Air tightness test. According to the requirements of plate heat exchanger, the tightness test shall be carried out after the hydrostatic test. The test pressure shall be 1.05 times the working pressure. Brush around the plate of the heat exchanger with soapy water to check for air leakage.