This presentation on General deficiencies found during inspection of gates for dams, canals etc and remedy with case studies was done by Shri D.K.Mehta at All India Seminar on Safety Inspection and O & M of gates conducted by Gujarat State Center of The Institution of Engineers (India) on July 3rd 2015 at Ahmedabad.

1. GENERAL DEFICIENCIES
FOUND DURING
INSPECTION AND REMEDY
WITH CASE STUDIES

2. Introduction
Incidents of distress can be attributed to the
deficiency of planning, structural design,
hydraulic design, fabrication, erection,
operation and maintenance. Vibration,
cavitations, non-closure, corrosion, erosion
and aging problems, improper selection of
materials and neglect of lubrication of
components have resulted in mal-functioning
and even failures of gates in the past.

4. (1)Fig (1)

5. (1) Problem and Solution
Problem:
Washing away of the gate took place due to detachment of left side
trunnion girder
On inspection of all gates, the following deficiencies of gate
structures were observed:
1. Inadequate welding between trunnion girders and tie flats. In fact
the flats were welded only at flanges of trunnion girders.
2. Existence of substantial gaps of varying degree between tie flats
and webs of trunnion girders.
3. Eccentricity due to incorrect alignment of trunnion girders
4. Apprehensions about inadequacy, welding the insulated tie flats with
anchor girders

6. (1) Contd…
Solution:
1. An improvised scheme adopted to connect the webs of the trunnion
girders and tie flats by way of welding additional plates all along the
web of the trunnion girder on either side of each tie flat. (See Fig.)
2. In order to tackle eccentric transfer of load from trunnion bracket to
trunnion girder, additional plates of triangular shape were welded on
the flange plate of trunnion girder .

7. (1) Contd…
Solution:
3. In view of suspected deficiency of tie flat- anchor girder
junction, one tie flat near upstream flange of anchor girder
was exposed and it was revealed that the tie flats were
welded only to flanges and not to the webs of the anchor
girder.
4. The tie flats were welded only to flanges and not to the webs
of the anchor girder. Drive pins to connect the tie flats and
anchor girders and weld the pins to lock (See Fig). The
blockouts were then filled by epoxy mortar and epoxy grout.

8. (2) Failure of Radial Gate Leaf
Gate Features: 23nos. 12.941m x 9.85m and 2 nos. 4.877
x 9.85m spillway radial gates operated by rope drum hoists.

9. (2) Problem and Solution
Problem:
One of the end gates of smaller span failed while in closed position
at the the top right arm and horizontal girder. Failure of the
corresponding joint between bottom arm and horizontal girder and
also between the arm and trunnion hub, resulted in wrenching away
the arm assembly down the river. Skin plate assembly and
horizontal girders slid downstream and impacted on the trunnion
girders. On inspection the following observations were made:
 Webs of both the horizontal girders had twisted.
 End portions of skin plate beyond last vertical stiffeners had bent.
 Side guide rollers were jammed.
 End plates of trunnion hubs had bent.
Provision of spillway stoplogs as also of cat-walk bridge at trunnion
level had not been made.

10. (2) Contd…
Solution:
1. Provision of tie beams in between the end arms to take
care of side thrust of smaller gates. The Provision
existed for larger size gates.
2. Provision of bearing stiffeners and Drain Holes.
3. Stiffening of top cantilever portion of skin plates.
4. Strengthening of arm sections and their junctions.

11. (3) Difficulties encountered during
erection of Radial Gates
Gate features:18 nos. 15.00m x 14.565m
spillway radial gates operated by rope drum
hoists.

12. Fig (3)

13. (3) Problem and Solution
Problem:
 Distortion of tie flats: Tie flats (190 mm X 63 mm)
were procured in either single or two lengths. The pieces
procured in two lengths were butt welded. Maximum of
25mm kink was noticed close to the butt-welded joints .
4mm distortion was observed in a length of 130 to
300mm forming a maximum angle of deflection of the
order of 4 degrees due to distortion
 Fouling of tie flats with end arms : Arm hub connectors
were fouling with the exposed portions of embedded tie
flats restricting the lift of gate to 10.20m as against
designed lift of 14.565m.

14. (3) Solution
 The rectification of distorted tie flats was
carried out by welding additional plates of size
150mm x 10mm and 210mm x 8mm at the
location of kinks on the interior side
 In order to analyze stress pattern a finite
element computerized analysis on STAAD-III
was carried out.
 A proposal involving cutting & strengthening
Arm Hub Connector formulated.

15. (4) Distress of Radial Gate
Gate features:3 nos. 12.00m x 19m spillway
radial gates operated by rope drum hoists.

16. (4) Problem and Solution
Problem:
Lock nuts of trunnion cover plate were found sheared off. Trunnion
pin had rotated along with the hub/bush probably due to
development of friction /rust between bosh & pin. (Mat. : forged steel
with nickel chromium plating ). Rustoline was then injected, but
without success. Attempts to rotate the pin to make it free from the
hub bushing by jacks (12 capacity) but without success. Observed
that the Grease coming out from only half segment (downstream) of
trunnion.
Solution:
Suggestion was made to inject rustoline and castrol oil ( or any
Suitable lubricating medium ). It is now being envisaged to
rectify/replaced the trunnion assembly parts including pin and bush.

17. (5) Curtailment of height of radial gates
Gate features:26 nos. 15.00m x 15.24m spillway
radial gates operated by 2x115t hydraulic hoists.

18. Fig (5)

19. (5) Problems and Solution
Problem:
The work of design, manufacture and erection of all gates and
hoists, except erection of skin plate & vertical stiffener assemblies,
had been completed when it was ordered to restrict the storage level
to about >10 m head against the gates.
Solution:
 Curtailment of top of skin plate in the central portion at reduced
storage level and provision of ‘hood’ for directing wave splashes
away from the gate components.
 Discontinuation of vertical stiffeners in the central portion at top.

20. (5) Contd...
 Curtailment of primary shield to protect radial end arms at MWL in
the end
portions.
 Curtailment of secondary shield in the end portions to protect
ceramix coated piston rods of hydraulic cylinders.
 To provide electronic water level sensors to ensure raising of the
gate as soon water level reached the storage level.

21. (6) Failure of Barrage Gates
Gate features:17 nos. 17.678m span vertical
lift Barrage gates operated by rope drum
hoists.

22. (6) Problems and Solution
Problem:
 Overtopped by flash flood resulting in damages to 12
nos. of barrage gates. For want of provision of stoplogs,
no regular maintenance of gates could be carried out.
 The gate components were found very heavily rusted.
 The faulty fabrication was observed as the full depth
vertical splice joints from top to bottom were provided at
the centre line of the gate. During site inspection, it was
observed that the skin plate at the top of gate had
deflected and the top horizontal girder had apparently
failed in tension

23. (6) Contd…
Solution:
1. The existing gates were restored by welding and
strengthening.
2. Later on barrage gates were replaced with new ones with
modified sections so as to withstand higher heads due to over
topping.
3. The provision of stoplogs was introduced by cutting stoplogs
grooves along with a provision of new gantry crane.
4. In order to take care of increase in hoist capacity due to the
modifications, RCC counter weights on d/s of gate supported
on cross beams and pulleys attached to gantry girder were
introduced, thus bye-passing the existing hoist bridge..

24. (7) Refurbishment of barrage gates
Gate features :70 nos. 12.192m x 3.66m Stoney
type crest gates operated by chain hoists with
counter weight.

25. (7) Problems and Solution
Problem:
The gates erected in sixties and remained largely un-
attended as provision of regular stoplogs was not made.
However, provision of two nos. floating bulkheads was
introduced at a later date
Solution:
1. It was suggested that the existing gate leaves of bow
type girders be replaced by new gates (with plate
girders) with teflon cladded side seals. The provision of
gun metal bushes in roller train assemblies be replaced
by self lubricating bushes.
2. No. of Floating bulkheads be suitably increased.

26. (8) Overtopping of vertical lift spillway
gates
Gate features:33 nos. 12.83mx6.10m vertical
lift spillway gates operated by chain drum
hoists.

27. Fig (8)

28. (8) Problems and Solution
Problem:
Provision of free board over the gates was inadequate
resulting in exposure of top main horizontal girder and struts
to continued wetness and development of undesirable lateral
forces besides rusting and pitting of gate members. The
wave splashing also caused a loss of substantial storage .
Solution:
In order to prevent over topping of gates the following
alternative proposals were examined.
(1) Wave deflectors/Flow splitters
(2) Gate Hood
Provision of Gate Hood was finally suggested so as to direct
the flow away from the immediate downstream gate
components.

29. (9) Obstruction of bottom horizontal
girder of a wheeled gate with ogee
crest
Gate features: 2nos. 16.00mx7.80m emergency
gates of fixed wheel type operated by rope drum
hoists.

30. (9) Problems and Solution
Problem:
During erection of emergency gates, the bottom horizontal girder
flange of emergency gate was found to be obstructed by ogee crest
disabling seating of skin plate on the gate sill thus leaving a gap of
270mm between skin plate bottom and sill beam.
Solution:
1. After site inspection, a number of alternatives were considered.
2. Extension of skin plate at bottom by 80 mm along with suitable
stiffening of extended portion of gate bottom.
3. Reduction in depth of horizontal girder, along with provision of an
additional web plate.
4. Removal of bottom girder flanges from current location and
rewelding modified and strengthened bottom girder thus making an
‘l’ shaped girder instead of ‘I’ shaped.

31. (10) Non-closure of Silt Flushing Tunnel
Gate
Gate features:2nos. 1.50m x 2m high head silt
flushing fixed wheel gates operated by rope
drum hoists.

32. (10) Problems and Solution
Problem:
When one of the gates (with upstream skin plate & sealing) was
partially operated at high reservoir level, it was noticed that the gate
was not closing. The main cause was identified as impinging of
water jet on the bottom girder, thus creating upthrust on the gate
resulting in non-closure.
Solution:
1. Modification of gate bottom involving cutting of bottom inclined plate
such that the issuing jet was at about 45 degree to the horizontal.
2. Provision of 45 mm wide plate on the upstream side of the gate
causing additional down thrust on the gate thus facilitating gate
closure.
3. Replacement of rubber seals by teflon cladded seals.

33. (11) Jamming of Spherical Roller of Fixed
Wheel Gates
Gate features:8 nos. 18.00m x 5.35m fixed wheel
type under sluice gates operated by rope drum
hoists.

34. Fig (11)

35. (11) Problems and Solution
Problem:
Silt laden water entered into the spherical roller bearings causing
jamming of the bearings of wheels resulting in their sliding instead of
rolling. Bearing was in totally broken condition with dislocation of its
rollers and deposition of silt and clay inside the bearing. Oil seal on
one of the sides was oriented in the reverse manner and that the ‘O’
rings were located on the outside of the counter-head screws
thereby allowing water to enter into the bearings through the threads
of the screws. (See Fig.).
Solution:
Changing the location of O-rings and by fitment of oil seals in correct
orientation. Size of O-ring & no. of screws increased.

36. (12) Catapulting of Service Gate
Gate features:2nos. 3.30m x 4.20m vertical lift
fixed wheel type intake service hates operated
by 45t hydraulic hoists.

37. Fig (12)

38. (12) Problems and Solution
Problem:
The gate had catapulted to a height of 8.60m and lodged itself on the dogging
platform. The hoist stem rod completely buckled and guide shoes sheared.
Operating Criteria provides for balanced raising of gate achieved by crack
opening (Max. 150 mm)
During Balancing by Crack opening, the penstock portion between the gate and
turbine got filled up and the pressure nearly equal to reservoir head started
acting at the bottom side of the gate while the pressure at the top remained
equal to atmospheric pressure. It was also found that the gap between the gate
body and downstream wall was small thus restricting the flow of water through
this gap. The pressure developed at the bottom side of gate was of such a high
magnitude that the gate was catapulted.
On detailed inspection following observations were made:
1. Hoist links twisted
2. Gate Assemblies got twisted, Max. twist being 55mm.
3. Seals bases bent at centre about 4 mm.
4. Left Side guide shoe and lock plate of wheel assembly damaged.

39. (12) Contd…
Solution:
Rectification and strengthening measures carried
out on Gates. Hoist stem replaced.
Following Model studies recommended to arrive
at exact reason of the failure:
1. Relationship between the crack opening and gap
between the gate body and downstream wall.
2. Typical back of gate opening configuration.
3. Effects such as catapulting height, uplift forces
and pressures on the system during unbalanced
operation.
4. Effect of speed of opening of gate.

40. (13) Bulging of Gate Shaft Liners of Penstock
Gates
Gate features:2nos. 5.0mx9.0m fixed wheel type
penstock emergency hates operated by 500t
capacity hydraulic hoists.

41. Fig (13)

42. (13) Problems and Solution
Problem:
Emergency gate shaft got filled up to about 73 m head probably on
account of flow of water through the hole left un-plugged in the air
vent shaft while the gate was in closed position. Shaft again got
filled about 50m head. After Dewatering, crack of 15mm width at the
interface of 2nd and 3rd stage concrete in the bonnet chamber floor
on the U/s side of bonnet cover. U/s Welded joint of the bonnet
body has opened at a height of 1.30m above the gate upstream
liner had bulged towards downstream to a maximum of 146mm
causing profuse leakage.

43. (13) Contd…
Solution:
On site inspection, it was suggested that upstream bonnet plate be
replaced and damaged concrete backing (in particular 3rd
stage
concrete of 650 mm thickness) removed and recast after creating
dry conditions. The additional provisions of anchors in u/s body liner
and effective keying by angle stiffeners etc. were made from safety
considerations.
General guidelines:
1. Recheck the design of bonnet plates (with stiffeners in longitudinal
as well as transverse direction) for withstanding full external
pressure with permissible stress at 80 % Y.P.
2. Check adequacy of bonnet body anchorage with concrete with the
assumption that there will be hollows behind the liner in which water
can seep and exert water pressure.
3. Check whether the stiffening ribs are provided with large enough

44. (13) Contd…
4. Check provision of adequate grout holes in the bonnet plate to
grout any hollows that might be created during concreting
operation or subsequent shrinkage
5. Check provision of adequate dowel bars at suitable intervals
between second & third stage concrete.
6. Check that coarse/fine aggregates proposed to be used are non-
reactive in ASR.
7. Check that the concreting behind the liners is limited to the
maximum of
1.0m in a single lift.
8. The floor of bonnet chamber be made water tight.

45. (14) Modification of Gate Bottom
Shapes
Gate features:2 nos. 1.829mx3.658m vertical lift
fixed wheel type service and emergency gates
operated by electric hoists

46. Fig (14)

47. (14) Problems and Solution
Problem:
The service gates are provided with upstream sealing and skin plate
whereas the emergency gates are having downstream sealing and
skin plates. It was reported that the gates create difficulty in closing
besides vibrations, cavitation problems and profuse leakage past the
gates.
Solution:
Redesign the bottom lip slope of the service gate , an angle of 35
degrees or more with the horizontal between the controlling edge of
the gate and downstream edge of bottom-most girder (See Fig ).
Likewise for emergency gate, the bottom lip shape was proposed to
be modified to provide for flow convergence of to flow passage so as
to achieve positive pressure on gate bottom.

48. (15) Mal-functioning of Fixed Wheel
Service gate
9nos. 3.050m x 4.575m high head vertical lift fixed
wheel type service gates operated by rope drum
hoists.

49. (15) Problems and Solution
Problem:
The gates were not self-closing even at low reservoir levels. It was
observed that the stainless steel cladding of rubber seals had
peeled off at certain locations and wheels were not rotating freely
and bulging of stainless steel plate of liner of breast wall had taken
place..
Solution:
1. The seal seats and breast liner plates cladded with 1.25 to 5mm
stainless steel plates be removed fully as it was damaging the seals
and obstructions to movement of gate.
2. Stainless steel cladded seals be replaced with Teflon cladded seals
3. The Bottom Shape of gate be modified by reducing the depth of
girder, while maintaining a lip angle of not less than 32 degrees.

50. (16) LESSONS LEARNT
1. Corrosion of structural members
2. Lubrication of machinery components should be attended regularly
3. Provision of stoplogs meant for maintenance of main gates.
4. The brass/ bronze/stainless steel cladding has peeled off. Use of
such cladded seals be discontinued and these should be replaced
by teflon cladded seals
5. The sealing arrangement for spherical roller bearing of wheel
assemblies should be designed and maintained with extreme care.
Any slip up can result in jamming of wheels .
6. In case of gates used for balancing of water pressure by crack
opening, care should be taken to ensure that the area of crack
opening is smaller than the area between down stream edge of
the gate and the shaft (slot) normally designed as “ back of gate
orifice” which could otherwise cause catapulting of the gate.

51. (16) LESSONS LEARNT
7. Overtopping of gates should be suitably
protected. It can lead to vibrations and corrosion
in the gate structure.
8. Special attention should be accorded to the
bottom shapes of the gates. The geometry of
gate bottom may have to be established from
hydraulic model studies particularly for high
heads unless data for similar installation is
available.
9. While planning the fabrication activities of the
gate, the vertical joints should not be located at
the centre of gate, instead these should be
planned at the least possible bending moment
location. Also splice joints should be suitably
staggered.

52. (16) LESSONS LEARNT
10. The project authorities should formulate suitable
guidelines for inspection, operation and maintenance of all
gates and hoist structures. Suitable training should be
imparted to operating staff. A logbook of operation,
inspection, maintenance and repairs for each gate
structure should be maintained at the project site.
11. The provision of suitably designed dowel bars between
different stages of concrete is essential for safety and
performance of the structure. The surfaces of previous
stages of concrete should be thoroughly roughened and
treated before laying the next stage. Adequate grouting
measures should be provided for concreting behind the
steel liners in order to grout any hollows that might be
created during concreting operation or subsequent
shrinkage.

53. THANK YOU