Quality First-Donper stainless heating water tank promoting

the healthy development of heat pump industryHuangShi DongBei Mech-Electric Group Solar Energy Co.Ltd. Xiongyan Shi

Prologue:Quality is the core competitiveness. To verify continually the anti-corrosive

property of products after 2013, Donper pays a return visit and verification to the

previous users again. Through the way of products replacement, In January 2015,

Donper recalls parts of stainless pressure water tank which have been used for ten

years to be the sample of verification. Through the dissection verification of the

technical department, there are not corrosive signs in the inner tank straight welding,

water pipe welding and inner head welding

一、 Quality is the core competence of the companySince 2004, Donper Co. has been researching, producing and selling on

stainless steel heating water tank. According to the features of air source heat pump,

solar water heating and hanging furnace heating, etc., developed specialized water

tank and hundreds models, and achieved several intellectual property rights. Donper

accumulated rich experience on technology and research, particularly outstanding on

stainless steel tank in application area, invented “stainless steel corrosion protection

wall patented technology”, “stainless steel heat pump tank with internal coil”,

“stainless steel pressure tank with anastomosing pattern of distributed device” etc.,

attracted more attention by the same industry.

The quality is one of the core competence in company. Donper has been always

focused on the quality, reviewed the quality and validation from our customers after

2013, for validating the corrosion property. In January 2015, random sampling of

tanks which sold in 2005, recalled 10 years stainless steel tanks as the random

sampling through the old exchange for the new, and technology Dpt. dissected and

turned out that there were no corrosion in straight seam welded, water pipe welding

and photosensitive head welding of the inner tanks. (Following shown)

（Figure A, Before the anatomy) (Figure B, cut open outside tank)

(Figure C, anatomy)

(Figure D, part of inner tank)

二、 The quality factor of stainless steel water tank1、Raw material control

As you know, SUS304 stainless steel belongs to austenite metallic material, its

main components are chromium,nickel,carbon etc. Once the material occur some

problems, no matter how advance the process is, it cannot resolve the corrosion

problems. So how to control the quality of raw material, became the most important

target to making a high quality stainless steel water tank.

Through the professional management process, efficient controlling methods and

stable supplier channels, Donper avoid the fake SUS304 stainless steel come into

factory and ensure the quality of material from the source.

Product structure design

Product structure design mainly include itmes as below:

⑴ Study system features in application fields, such as realizing mutual

compatibility between heat pump circulation system pressure bearing, heat pump unit

heating capaicty, circulation flow and material;

⑵ Components design and assembly must adhere closely to the standard of

pressure vessel;

⑶ Power of heat exchanger is larger than heating capacity of matched heat pump

units;

⑷ For water tank compressive strength, test pressure must be 1.5 times or twice

larger than Max. working pressure.

3、 Anti-corrosion processing after welded

Donper first inaugurates anti-corrosion wall patent in nation wide. No water

tanks met corrosion even after 10 years of using because of the technology. Every

single water tank was tested and processed before shipped.

SUS304 stainless steel has high reliability of anti-corrosion itself due to

automatic argon arc welding, but the material became not strong enough to resist

corrosion after 1000℃ of processing and welding. Welding line endanger the whole

tank. Molecular structure changed, the harm matter carbon poor chromium appeared.

Welding line becoming rusting when carbon poor chromium encounters chloridion

released in the water. When the tiny thing happening, the whole tank is going to dead.

Donper discovered the phenomenon, special processing procedure adopted.

Harm matter like carbide was cleared, then several microns protective film would

covered on welding line. The protective film is major composed by chromium.

Thanks to the dense and uniform film, water tanks made by Donper have high

performance on corrosion resistant.

4、heat insulation performance

The factors that affect heating water tank heat insulation performance are water

temperature, heat conductivity coefficient of insulation material,ambient temperature

and insulation thickness.

Therefore, Donper uses low heat conductivity coefficient and stable American

DOW foaming. During the design, the using condition for heating water tank to match

system and system using area are considered in deciding the thickness of insulation

5、heating water tank pressure-bearing strength

Water tank pressure bearing strength is an important factor in designing, which

affects the service life of heating water tank directly. Water tank pressure-bearing

strength mainly includes

（1）Max.working pressure; （2）fatigue pulse strength.

When designing heating water tank, the working condition of tank to match the

system must be considered, different system has different pressure-bearing condition.

For example, for gas boiler water tank, usually the heating power is 18-36KW,

therefore, the gas boiler will heat the water every 10 minutes, during the process, heat

expansion will happen for many times. However, solar usually spends a day to heat

the water.

三、ConclusionQuality is the life of a company, the cornerstone of enterprise's survival and

development, and the root of the healthy development of the industry. Only sustained

innovation, strict management, the spirit of excellence, research and focus on

applications, and persistent efforts can the high quality and first-class products be

produced.

The author: ShiXiongYan, Engineer

He is in charge of the research of the solar hot water systems, stainless pressure

heating water tank and solar collectors in HuangShi DongBei Mech-Electric Group

Solar Energy Co.Ltd. Devoted to the technical research of flat plate solar collectors,

heat transfer of solar hot water system, the structure design of pressure water tank,

stainless pressure water tank welding and anti-corrosion.