Analysis and Handling Method of Common Faults of Plate Type Heat Exchanger

Analysis and Handling Method of Common Faults of Plate Type Heat Exchanger

15 Feb 2019

The common faults of plate heat exchanger include liquid string, leakage, excessive pressure drop and inadequate heating temperature.

Schematic diagram of plate heat exchanger
String fluid
1. Causes
(1) Cracks or perforations occur in plate corrosion due to improper selection of plates.
(2) Operating conditions do not meet the design requirements.
(3) Stress corrosion is caused by residual stress after sheet cold stamping and too small clamping size in assembly.
(4) There is slight leakage at the plate leakage trough, which causes harmful substances in the medium to concentrate and corrode the plate, forming a series of liquids.

2. Processing Method
(1) Replace the plate with cracks or perforations and find the cracks on the spot by light transmission method.
(2) Adjust the operating parameters to meet the design conditions.
(3) The clamping size of heat exchanger during maintenance and assembly should meet the requirements, not the smaller the better.
(4) reasonable matching of sheet materials.

External leakage
1. Causes
(1) The clamping size is not in place, the size is not uniform everywhere (the size deviation should not be greater than 3 mm everywhere) or the clamping bolt is loosened.
(2) Some gaskets are separated from the sealing groove, the main sealing surface of the gaskets is dirty, the gaskets are damaged or the gaskets are aging.
(3) The plate deforms and the misalignment of the assembly causes the running mat.
(4) There are cracks in the plate sealing groove or the second sealing area.

2. Processing methods
(1) In the pressureless state, the clamping equipment should be re-clamped according to the clamping size provided by the manufacturer. The dimensions should be uniform and uniform. The deviation of the clamping size should not be more than (+0.2N) (N is the total number of plates), and the parallelism between the two clamping plates should be kept within 2 mm.
(2) Make a mark on the leakage site, then the heat exchanger is disintegrated and solved one by one, and the gaskets and plates are reassembled or replaced.
(3) Dismantling the heat exchanger and repairing or replacing the deformed part of the plate. When there is no spare parts, the deformed plate can be temporarily removed and reassembled for use.
(4) When reassembling and disassembling the plate, the plate surface should be cleaned to prevent dirt from adhering to the gasket sealing surface.

All-Welded Plate and Frame Heat Exchanger
Excessive pressure drop
1. Causes
(1) The operation system pipeline has not been cleaned properly, especially many dirt (such as welding slag) in the newly installed system pipeline enters the inside of the plate heat exchanger. Because of the narrow cross-section area of the flow channel of the plate heat exchanger, sediments and suspended solids in the heat exchanger accumulate in the corner hole and the diversion zone, resulting in a large reduction of the flow channel area and pressure loss in this part.
(2) When the plate heat exchanger is first selected, the area is too small, which results in the high flow velocity between plates and the high pressure drop.
(3) The pressure drop of plate heat exchanger is too large due to the scaling on the surface of plate after a period of operation.

2. Processing methods
(1) Clean up dirt or plate scaling in the heat exchanger runner, and clean the newly operated system once a week according to the actual situation.
(2) Soft water after softening treatment is the best choice for secondary circulating water. Generally, suspended substance concentration in water is not more than 5 mg/L, impurity diameter is not more than 3 mm, and pH is more than 7.

The concentration of Ca and Mg should not exceed 2 mmol/L when the water temperature is not more than 95 C.

When the water temperature is higher than 95 C, the concentration of Ca and Mg should not be more than 0.3 mmol/L, and the mass concentration of dissolved oxygen should not be more than 0.1 mg/L.

(3) For central heating system, the method of primary and secondary water replenishment can be adopted.

ACCESSEN, as an expert plate type heat exchanger supplier, wish to build long-term cooperation with overseas customers.