FIELD OF INVENTION
The present invention relates to a manhole door handing device for self sealing of the manhole
door in vertical heaters of a power plant. More particularly the invention relates to an handling aid
for handing of the manhole door to provide a quick aid in all positions i.e. from insertion to
placement, removal and reposition.
BACKGROUND OF THE INVENTION
High pressure feed water heaters are employed to increase the thermal efficiency in the
regenerative cycle of a power plant. Tube side of these high pressure feed water heaters are
designed for a pressure of 285 to 300 kg / sq.cm.g. High pressure conditions on the feed side calls
for utmost care in the design of each component and assembly with full consideration for the
reliability and safety aspects. Due to the high pressure, process considerations and design
optimization, the channel side is formed by welding hemi-spherical dome with the lipped tubesheet.
This channel has two branch connections for feed water inlet and outlet for this heater. Channel is
divided inside with the help of a partition plate with a door in the partition plate for access to the
other side. A manhole door opening is also provided for the maintenance of these heaters.
Prior art for the closing arrangement of this manhole opening was to bolt the cover plate to
manhole facing with the conventional bolting arrangement. Due to the high pressure conditions,
these conventional bolting arrangement lead to leakage. Further opening and handling of cover
during maintenance causes difficulty. In order to overcome these problems, a self sealing manhole
door device is developed for providing sealing on this manhole door opening.
OBJECTS OF THE INVENTION
Therefore, an object of the invention is to propose a manhole door handing device for self sealing
of the manhole door in vertical heaters of a power plant, which can seal the leakage of the manhole
door after closing due to high pressure conditions.
Another object of the invention is to propose a manhole door handing device for vertical heaters of
a power plant, which can provide a quick aid in all positions that is from insertion to placement,
removal and reposition of manhole door.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be described in detail with the help of the figures of the accompanying
drawings in which:
Figure 1 shows the high pressure feed water heater with manhole door.
Figure 2 shows the manhole door cover handling aid below the H.P. heater.
Figure 3 shows the manhole door cover handling aid.
DETAILED DESCRIPTION OF THE INVENTION
Manhole door cover handling device (M) is made of the following major parts as shown in Figure 3
1. Worm wheels
2. Bearing
3. Jack Screw / lead screw
4. Guide pipe
5. Base plate with handles and wheels
6. Wheel assembly
7. Top plate / worm wheel guide plate
8. Worm
The following steps are followed for manhole door cover removal.
Step 1 - as shown in Figure 4, the manhole door cover handling aid (M) is positioned exactly
below the H.P. heater (H) and the height for operation is adjusted.
Step 2 - as shown in Figure 5, the worm wheel guide plate / top plate (7) is bolted with
manhole door cover (10).
Step 3 - as shown in Figure 6, the cover is lifted (L) by about 50-100 mm along the vertical
axis with the help of rotation of lead screw (3).
Step 4 - as shown in Figure 7, with the lift of cover and touch of cover partition plate, the
cover is tilted by about 75° to horizontal axis.
Step 5 - as shown in Figure 8, the cover (M) is rotated by 90° along the vertical axis.
Step 6 - as shown in Figure 9, the manhole door cover (M) is lowered down to come out of the
opening in the channel / water box. Since the manhole door opening is oblong in shape, opening
size is greater than the width of door, and hence manhole piece will come out freely.
For insertion and re-position / closing of manhole door cover (M).
For insertion and re-position / closing of manhole door cover, reverse sequence as specified above
is to be followed from step 6 to step 1.
WE CLAIM
1. A manhole door handing device for self sealing the manhole door in vertical heaters of a
power plant, comprising:
- worm wheels (1) for providing swivel movement to the top plate (7);
- a set of bearing (2) for guiding the lead screw (3);
- a lead screw (3) for providing vertical movement to the top plate (7);
- a guide pipe (4) for enclosing the lead screw (3);
- a base plate (5) for accommodating the lead screw (3);
- a handle and the wheel assembly (6);
Characterized in that,
a top plate (7) is bolted with the manhole door cover (10) and is capable of moving up and
down by rotating the lead screw (3) and is able to swivel and tilted with respect to vertical
axis.
2. A method for handling the device as claimed in claim 1 for removal of manhole door cover
in vertical heaters of a power plant comprising the steps of:
Step 1 - positioning the manhole door cover handling device (M) exactly below the high
pressure heater and adjusting the height for operation.
Step 2 - bolting the worm wheel guide plate (7) with the manhole door cover (10);
Step 3 - lifting the cover by about 50 to 100 mm along the vertical axis by rotating the lead
screw (3);
Step 4 - tilting the cover (10) by about 75° to vertical axis.
Step 5 - rotating the cover by 90° along the vertical axis; wherein,
Step 6 - the manhole door cover is lowered to come out of the opening in the channel /
water box when the manhole door opening being oblong in shape and opening size being
greater than the width of door, the manhole door piece (10) comes out freely and for
insertion and re-position / closing of manhole door cover (10), a reverse sequence from step
6 to step 1 is followed.

A manhole door handling device comprising of worm wheels (1) for providing swivel movement to
the top plate (7), a set of bearing (2) for guiding the lead screw (3) which provides vertical
movement to the top plate (7). A guide pipe (4) encloses the lead screw (3). A base plate
accommodates the lead screw (3), a handle and a wheel assembly. The top plate is bolted with the
manhole door cover (10) and is capable of moving up and down by rotating the lead screw (3) and
is able to swivel and tilted with respect to vertical axis.