Manhole Quality Identification

Manhole is an opening component embedded in a pipe mouth, container or equipment structure, used for personnel entry and exit, equipment maintenance and safety inspection. It usually consists of a short barrel section (or short tube), a flange and a cover with a handle. The manhole has a removable cover or door panel for easy opening and closing by the operator. When designing and selecting manholes, relevant standards and manuals are generally referenced.

Zhongke Testing and Appraisal Institute can provide manhole quality appraisal services and make accurate appraisals in terms of product design analysis, load analysis and product quality analysis.

manholes are divided into normal pressure and pressure manholes according to the pressure;
manholes are divided into round, oval and rectangular manholes according to their shapes. The rectangular manholes are only suitable for normal pressure equipment;
manholes are divided into installation positions It is divided into horizontal and vertical installation manholes;
manhole cover fixation methods include rotating cover and hanging cover;
manhole opening speed has ordinary type and quick opening type. The structure and size of manhole are generally standardized, and you can refer to the relevant manuals for selection or design.

HG/T 2055.2-2019 Glass-lined manhole with sight glass
QC/T 1065-2017 Road transport of flammable liquids and dangerous goods tank vehicles Manhole cover
HG/T 2053-2018 Glass-lined equipment Manhole flange
YD/T 5178-2017 Communication pipeline manhole and hand hole atlas
HG/T 2055.1-2015 Glass-lined manhole
CB/T 3921-2013 Marine auxiliary boiler manhole device
CB/T 4392-2014 Marine manhole cover
NB/T 47040-2013 Boiler manhole and hand hole device
HG/T 2053-2006 Glass-lined equipment manhole flange
CB/T 3921-2001 Marine auxiliary boiler manhole device
0CB/T 3981-2008 Ballast water tank manhole cover with inspection hole
1QB/T 2072.6-1994 Sugar making machinery, general parts for pressure vessels, rectangular manhole
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"According to the information provided by the client, the demander and supplier signed a "Purchase Contract". The subject matter was 12 low-pressure vessels and towers (composite panels), including the "vacuum distillation tower and vacuum stripping tower" involved in the case. The contract equipment started to be used, and the demander discovered that the "manholes of the vacuum distillation tower and vacuum stripping tower" involved in the case (hereinafter referred to as "the case involved") The flange cover and flange stainless steel lining of "Manhole" appeared to have problems such as bulging and deformation in many places. After repair and repair by the supplier, the above-mentioned problems still appeared in the lining of the "manhole" involved. The demander believed that the reason was that the supplier did not manufacture according to the requirements of the design drawings and the design materials; while the supplier believed that it was caused by improper design standards selected by the designer and had no direct relationship with the manufacturing quality. In order to find out the reasons for the bulging and deformation of the "manhole" involved in the case, the purchaser proposed to conduct quality appraisal. "

Identification analysis results:

The identification expert group's relevant information, on-site investigation and inspection results, and calculation results of the "manholes of vacuum distillation towers and vacuum stripping towers" involved in the case After discussion and comprehensive technical analysis, the following appraisal opinions were made:

1) The main reason for the bulging and deformation of the flange cover of the "manhole" involved in the case is that the lining layer is thin and cannot withstand the load under high temperature and negative pressure conditions, resulting in instability and deformation of the lining layer. At the same time, the difference in linear expansion coefficient between the stainless steel lining plate and the carbon steel body causes the deformation of stainless steel to be greater than that of carbon steel at high temperatures, which also causes bulging and deformation to a certain extent.
2) The main reason for the bulging and deformation of the flange of the "manhole" involved in the case is that the difference in linear expansion coefficient between the stainless steel lining plate and the carbon steel body causes the deformation of stainless steel to be significantly greater than that of carbon steel at high temperatures.