Verification of Initial Sealing for Manhole Door Self-Sealing Gasket D43.01 in Boiler Overhaul

Verification of Initial Sealing for Manhole Door Self-Sealing Gasket D43.01 in Boiler Overhaul

In the overhaul of power plant boilers, the sealing reliability of the steam drum manhole door is directly critical to the safe startup/shutdown and long-term operation of the unit. As a key static sealing component, the manhole door self-sealing gasket D43.01 features a high-resilience flexible graphite composite structure and a self-locating snap-fit design, and it has been widely applied in numerous 600MW-class power plants domestically. However, even with the use of high-quality products, failure to correctly verify the sealing status after installation can still lead to steam leakage, increased heat loss, and even unplanned outages. Therefore, after the manhole door is closed, how can one scientifically verify that the D43.01 self-sealing gasket is correctly in place and has achieved initial sealing?

1. Basic Visual Inspection

Visual inspection is fundamental. After D43.01 is installed, it should lie flat against the flange sealing surface, with no twisting, flipping, or localized warping. When closing the manhole cover, a slight "click" sound indicates that the elastic snap-fit has engaged initially.

2. Auxiliary Judgment by Manual Touch

Wearing clean gloves, lightly press along the manhole perimeter to feel if the gasket compression is uniform. D43.01 has excellent pre-compression capability at room temperature (standard compression 3–5mm). If any area is noticeably soft or shows a gap, it indicates an installation offset, requiring immediate adjustment. Do not rely on forcing it tight with bolts.

3. Recommended Cold-State Air Tightness Pre-Check

Before filling the boiler with water (pre-boiler water fill), compressed air at 0.2–0.3MPa can be introduced into the steam drum. Then, spray soapy water on the outside of the manhole. If no continuous bubbles are generated, it can be fundamentally confirmed that the D43.01 has formed an effective initial seal. Although this method is not a mandatory procedure, it is highly practical when closing the manhole for the first time after a major overhaul and significantly reduces the risk of rework during the hydrostatic pressure test stage.

4. Critical Monitoring During Hydrostatic Pressure Test

When the pressure is raised to 1.25 times the working pressure, dedicated personnel must closely monitor the manhole area for any signs of seepage, condensation, or "sweating." According to third-party testing, D43.01 has a sealing life of 3  years under operating conditions , provided it is "installed correctly the first time and verified thoroughly."

We are consistently committed to providing highly reliable boiler sealing solutions for the power industry. The manhole door self-sealing gasket D43.01 not only complies with specifications such as TSG 11-2020 and DL/T 438, but also earns customer trust through its ease of installation, ease of verification, and long service life.

HKZX-2025-12-11