Operation Manual For Valve Repairing Grinder VRM-PM800B

VRM-PM800 VALVE REPAIRING GRINDER
(Version 1.0)
RETOP Valve Repair Co., Ltd.
June 2014 
RETOP VALVE REPAIR CO., LTD. Zigong Sichuan, China T 86-813-2208857 WITEAM COMMERCIAL global@re-top.com www.re-top.net "1
OPERATION MANUAL
Patented Product, Counterfeiting Not Allowed!

FOREWORD

You are welcome to buy valve repairing grinders from us and become our
customer.
In this manual, operation instructions to the VRM-PM800B Model Valve
Repairing Grinder shall be provided. Valve repairing grinder is specially
designed for repairing of various valves, and it is developed based on the
principle of dynamic balance. Its main function is grinding after build-up
welding for the damaged valve parts. The grinder will be driven by
variable frequency motor. It features with infinitely variable speeds,
constant power, constant torque, planetary grinding head, as well as
coordination of revolution and rotation, thus, strong grinding capability can
be provided to make the grinding surface up to mirror finish level.
VRM-PM800B Model Valve Repairing Grinder is the second generation
product, improved from the VRM-PM800 model valve repairing grinder.
The grinder had obtained the National Invention Patent of China; it is not
only beyond the conventional valve repairing modes through universal
machine tools, but also different to the mechanical equipment for valve
manufacturing, the chucking tools and the process flow. The grinder is
one kind of special equipment to grind the build-up welding section on
valve sealing faces, which uses stainless steel and cemented carbide
welding materials.

Contents
1 Features and Performance Parameters of the Grinder 4
1.1 Grinder Features 4
2 Installation of Wedge block Components 5
2.1 Introduction to the Wedge block Components 6
2.2 Installation of Wedge blocks 6
2.3 The Function and Installation of the Guiding Plate 6
2.4 The Usage of the Guiding Ruler 7
3. Build-up Welding of the Sealing Surface 8
4 Installation of Grinding Disc Extension Rod 9
5 Installation and Connection of Grinding Disc 10
6 Elevation Height Adjusting 11
7 Selection of Hoisting Assembly 12
7.1 Motorized and Manual Forklift 12
7.2 Fixed Hoisting Assembly 12
7.3 Traveling Block 12
7.4 Placement of Valve on the Repairing Table 12
8 Installation of Grinding Disc 14
9 Regulation of Grinding Precision 15
10 Grinding Procedures 16
10.1 Feeding for Preliminary Test (Grinding Wheel) 16
10.2 Power-on for Grinding 16
11 Grinding Materials and Grinding Wheels 17
11.1 Selection of Grinding Materials 17
11.2 Selection of Opening, Speciﬁcation and Hardness 17
12 Cooling of Work Pieces 18
12.1 Formula of Cooling Fluid (for reference only) 18
12.2 Type of Cooling 18
13 Wedge Disc Manufacturing and Assembly 19
14 Electrical Installation 20
14.1 Overview 20
14.2 Electric Circuit Diagram 20
15 Matters Need Attention 21

1 Features and Performance Parameters of
the Grinder
1.1 Grinder Features
VRM-PM800B Model Valve Repairing Grinder is a special machine tool for valve repairing, which is
designed, developed and manufactured by RETOP Valve Repair Co., Ltd. and obtained the National
Innovation Patent of China. VRM-PM800B is improved from the first generation product VRM-PM800
model grinder; the new model has a good performance and its various performance indicators reached
international level. In addition to its high price performance ratio, it owns some innovative functions that
other similar products do not have; it is a good alternative to other valve repairing products. VRM-
PM800B has a compact and reasonable overall layout, and its high rotation speed, high precision and
high rigidity could provide high efficiency and reliability for user’s operation.
The grinder is mainly consists of two columns and a repairing table. The repairing table is made of high-
tensile steel, which could greatly improve the bending resistance, torsional rigidity performance of the
grinder during its operation; meanwhile, the stability of the grinder could be enhanced by making two
times of ageing treatment to the repairing table. The highly rigid and highly stable repairing table provides
a strong guarantee for the high precision operation of the overall grinder.
The grinder is equipped with an independent spindle unit which is configured with high-precision special
bearing. Special purpose bearing grease shall be applied to lubricate the bearing. The entire spindle unit
has little thermal deformation, good thermal stability and good precision retaining ability and it is
maintenance free. Meanwhile, the entire spindle unit has a good rigidity and an ideal mounting and
dismounting performance. The spindle is driven through high power AC variable frequency motor,
therefore, the spindle unit could perform rough grinding and fine grinding to the valve sealing surfaces in
an high-precision, high-rigidity, high rotation speed and efficient manner.
The grinder is provided with column sleeves which are driven by the electric motor to save both time and
labor; meanwhile, the column sleeves are provided with limiting devices to avoid faulty operation and
provide safety assurance for users in operation.
As the feeding system of the grinder is completely driven by the variable frequency motor through direct
connection, it has a good rigidity, dynamic performance and it has no noise. Because one rotation (360°)
of the hand wheel represents 0.1mm feed in the feeding system, the operating precision is improved
greatly to make the grinder realizing precision movement and positioning. High-duty grinding could be
made to the sealing surfaces after build-up welding or spraying with stainless steel or cement carbide
materials to reach a roughness of 0.8; high speed precision grinding could be made to the sealing
surface only by replacing the wheelhead and adjusting the rotary speed, reaching a curvature tolerance
of 100%, radial curvature tolerance of 100% and a surface roughness of 0.6.

Main Technical Specifications and Parameters (Unit: mm)
Dual Columns
H OD WT
2265 188 25
Column Sleeve
L OD ID
300 240 188
Beam L 530 W 240 H 300
Beam Enclosure L 330 W 340 H 360
Repairing Table
L W Face Plate Thickness 50
1400 1200 Machine Leg Height 200
Combined Wedge Block
L W For valve body &
wedge disc
processing900 90
Grinding Disc Extension
Rod
L OD Structure
Morse taper
grade 4
450, 600 70 – 75 Taper and Flange Type
Main Transmission Spindle
L OD Rotary Speed
668 50 – 90 0–3000 r/min
Spindle Sleeve
L OD Travel
414 150 60
Center Distance
Column to Spindle Center Repairing Range Plain Grinding Precision Sealing Surface
of the Valve Body
to Be Grinded700 DN200 – DN800 0.01mm-0.03mm
Grinding Disc Specification
DN200–DN250 DN300–DN350 DN400–DN450 DN500–DN550
DN600–DN650 DN700 DN750 DN800
Pain Grinding Tool,
Chamfer Grinding Tools,
Grinding Wheel Rack
DN200–350 DN400–800
L 60, W42, TK 20 L 70, W 45, TK 23
Grinding Wheel
DN200–350 DN400–800
BW50×25×13A46LB35 BW75×32×20A46LB35
Hand Feed Wheel For feeding and retracting, one rotation of the hand wheel (360°) represents a feed of 0.1mm
Stopper Used to control the elevation range and spindle locker, so as to ensure personnel and equipment
safety
Spindle Locker Used to replace the grinding disc extension rod, grinding disc and grinding wheel rack when the
spindle is in stationary state
Wire Control Switch Manual wire control to facilitate the grinding operation and the replacement and fine adjustment of the
grinding disc, grinding wheel, and grinding disc extension rod
Speed Regulator Used to control rotation of the grinder spindle, so as to regulate the grinding speed
Speed Motor Variable frequency motor model: YVP112M-50-A, motor power 4KW, 380V
Frequency Converter Model: HD30-4T5P5G/7P5P
Elevation Motor Model: Y90S-4, motor power 1.5KW, 380V
Elevation Mode Gear reduction, elevation speed 1120mm/min
Elevation Range Elevation range 1400mm, operating height 1300mm
Operating Height 2300mm

2 Installation of Wedge block Components
2.1 Introduction to the Wedge block Components
There are 24 threaded holes on the repairing table to install two pieces of 5° wedge blocks (Fig. 2-1)
which their installation positions can be adjusted by setting different hole spacing to repair and machine
valves with various sizes (DN200-DN800) on the repairing table. The wedge blocks are used to bring the
original slant sealing surface to a horizontal plane to facilitate machining operation. There are two very
important accessories supporting the use of wedge blocks, i.e. guiding ruler and guiding plate, both of
which determines the fitness accuracy and the percent of contact area when the grinded and machined
valve sealing surface and the wedge disc are assembled and guarantee zero leakage of the machined
valves.
2.2 Installation of Wedge blocks
As each wedge block has two ends (i.e. larger end and smaller end) that the larger end is thicker and
the smaller end is thinner, wedge blocks should be installed properly as specified below. Firstly,
determine the appropriate threaded hole spacing on the repairing table to install the valve to be repaired
based on its size, then, place the smaller ends of the two wedge blocks towards the columns and align
them to the mounting holes of the repairing table and fasten them slightly with 4 nos of M16 hexagon
socket head cap screws, and then measure, adjust the opening sizes of the two wedge blocks before
tightening them up. Please note: the opening sizes of the two larger ends and that between the two
smaller ends of the two wedge blocks must be equal.
2.3 The Function and Installation of the Guiding Plate
Machining operation is not allowed if the valve body is placed on the wedge block randomly, or
otherwise, there would be certain angle between the grinded sealing surface and the wedge disc when
assembling them, which will further lead to sealing failure. The guiding plate is a device to avoid such
angles. It is one piece of rectangle steel plate after fine grinding; and it is a carrier tool of the wedge
Fig. 2-1 Structure of Wedge Block

block and will be used together with the guiding ruler. The operating spacing of two wedge blocks is
determined based on the valve size: the operating spacing of the wedge blocks should be appropriately
increased along with increase of the valve sizes; however, the boss and the concaved shoulder of the
double flanges should be placed on the two wedge blocks. It is very easy to install the wedge blocks: as
there are threaded holes on the larger end of the wedge block, firstly install the wedge block and then fix
the guiding plate; that is OK.
2.4 The Usage of the Guiding Ruler
The guiding ruler is arc-shaped and the widths of both ends are equal, and the horizons of both ends
are same. It will be used together with the guiding plate to adjust the depth of parallelism between the
valve’s sealing surface and the wedge block and thus to control and/or eliminate the angle between
them. You must be careful to make such adjustment accurately.

3. Build-up Welding of the Sealing Surface
The efficiency of valve sealing surface grinding operation largely depends on the quality of build-up
welding, and higher quality of build-up welding of the sealing surface represents higher grinding
efficiency. Main factors guaranteeing good build-up welding quality are as below:
1) Polish and flush the scale layers on the sealing ring (or surface) with abrasive cloth, clear water or
grind off the parts severely corroded with the polishing machine before welding so as to avoid pores on
the surface to be grinded after build-up welding.
2) Spot welding or repair welding to the sealing surface are not allowed when conducting deep level
repairs to the old valves, and 360° full circle build-up welding must be made so as to generate a new
sealing surface and prolong the service life of the valves.
3) The welding beads on the sealing surface conducted build-up welding should be even and with same
width, and the surface of the welding beads should be smooth. The height of the build-up welding layer
on the valve’s sealing surface is generally 3-4mm, and its width should be 2-3mm greater than that of
the sealing surface of the old valves; the widths of stop valve’s valve flap and the gate valve’s wedge disc
after build-up welding treatment should be greater than 3mm. Hemming (360°) build-up welding to the
wedge disc and the flap must be made and repair welding must be mad to the pits, gaps appeared after
turning or grinding processes, so as to guarantee their roundness and assembling width (actual size).
The thickness of the build-up welding layer of the wedge disc should be determined by the opening
parameters of the sealing surface of the valve body, which refers to the distance between the left and
right sealing surfaces (sealing rings) of the valve body. There are still bigger end (valve port side of the
middle flange) and smaller end (bottom section of the valve cavity). Before build-up welding of the
wedge disc, it should accurately measure the distance between the two ends of the sealing surface and
determine the thickness of build-up welding layer based on the measured parameters, which should be
no less than 2.5mm so as to guarantee enough allowance for machining.

4 Installation of Grinding Disc Extension Rod
The lengths of the valve body are different for different sized (DN) valves. The operating height for
grinding process refers to the vertical length of the valve body placed on the wedge blocks. The
extension rods are the connecting link between the main transmission spindle and the grinding disc; the
lengths of the two kinds of extension rods are different, and their structures are also slightly different. It
will be determined by the valve conditions that which kind of extension rods should be used, i.e. use the
flange type extension rod (650mm) for large valves (DN400-DN800), taper type extension rod (450mm)
for small valves (DN200-DN350). Both ends of the flange type extension rod are provided with flange
plates; the mortise joint will be connected with the tenon joint of the transmission spindle’s flange plate
through threaded connection, while the tenon joint will be connected with the mortise joint of the
grinding disc through threaded connection. Do not damage the mortise & tenon joints when making
connections.

5 Installation and Connection of Grinding Disc
Re-Top Valve Repairing Grinder could repair a wide range of valves with various specifications, which
covers 13 kinds of specifications from DN200 to DN800, and we also customized 12 pieces of grinding
discs specifically for valve repairing. Taper type extension rod should be connected to the grinding discs
for DN200-DN350 valves; as there are threaded holes on the external taper end, the taper type
extension rod should be tightened by M14 bolts and nuts. Flange type extension rod should be
connected to the flange type grinding discs for DN400-DN800 valves.

6 Elevation Height Adjusting
As the grinding disc suitable for DN200-DN350 valves is installed on the extension rod in advance, the
grinding disc cannot reach the valve chamber if the height of the location of the grinding disc is lower
than the height of the valve; therefore, it must adjust the height of the main set to operate properly. The
adjusting procedures are: switch on the power and operate the hand controller to elevate the main set
150-250mm above the valve, then, place the valve on to the wedge blocks. For DN400-DN800 valves, it
may first place the grinding disc and the extension rod into the valve chamber if it is impossible to move
the grinding disc in the valve chamber when the main set is elevated to its height limit, then, lift the valve
and place it on to the wedge blocks and make the connection between the extension rod and the flange
plate of the transmission spindle and the connection between the extension rod and the grinding disc;
as the extension rod and large grinding disc are heavy, auxiliary tools and equipment are required for the
connection.

7 Selection of Hoisting Assembly
Hoisting assembly is essential for this grinder to repair valves, and the selection of proper type of hoisting
assembly relates to the progress and efficiency of valve repairing, as well as safety in production.
Therefore, it should be treated seriously and there are three types of hoisting assemblies selectable:
7.1 Motorized and Manual Forklift
Firstly, motorized forklift is preferred for wider sites and spacious environments, which is featured with
high power, flexible movements, stable operation, large loading capacity, higher hoisting height and is
suitable in particular for the repairing, hoisting and handling of large size valves with a weight over 3 tons.
Then, 3-ton manual forklift can be used for a loose repairing environment. All in all, forklift is a necessity
for valve repairing operations.
7.2 Fixed Hoisting Assembly
Fixed hoisting assembly is one kind of stationary hoisting assembly designed specially for hoisting of
valves to be grinded and machined, which will be installed by the side of the grinder and cannot be used
to handle valves like the forklift. As the large size valves are large and heavy, and the weight of DN400-
DN800 valves can reach 1-2 tons, and the weight of high pressure valves above PN6.4 (MPa) is even
higher, hence the load capacity of the hoisting assembly should be designed above 3 tons. In order to
facilitate valve handling, grinding of both sides of the sealing surface, the fixed hoisting assembly should
be capable of rotating by 360°. Although both chain blocks and electric blocks can be used, we
recommend it is better to use electric blocks if the height of the workshop is enough. From a point of
view of professional valve repairing, fixed hoisting assembly is ideal.
7.3 Traveling Block
Traveling block has a large lifting capacity and wide operational range, and it can move freely horizontally
and longitudinally. However, it is not specific and fixed for professional valve repairing, and it has a low
efficiency on adjusting the inclination of valves under repair. The reason is that the travelling block is
shared by all workers in the same workshop and the possibility in waiting is inevitable, which will affect
the valve repairing progress and work efficiency. Furthermore, traveling block should be installed at a
higher place and it is liable to cause swing during hoisting operation due to the longer wire cables, which
would easily lead to friction between valve body and grinder body and hinder the positioning of the
valves to be repaired.
7.4 Placement of Valve on the Repairing Table
Erect the valve and hold the double flange end down and the other end up. Place the valve onto the
wedge block with the hoisting assembly (keep the middle flange in same direction with the big end of
the wedge block). Conduct preliminary adjustment for center-to-center and line-to-line alignment, i.e.
align the flow orifice of the valve to the center of the grinding disc and slightly lower the grinding disc till it
is enough to install the grinding disc. However, you should carefully observe the descent height of the
grinding disc to avoid deformation or damage to the grinding disc due to the impact with the seal ring.
As the valve body is inclined for some degree on the wedge block and there is certain angle between it
and the grinder’s spindle, hence, the grinding disc cannot be put into the valve chamber in on try, or

otherwise it will collide with the valve wall. Therefore, it should handle and adjust the valve body for two
time before get it in a proper location.

8 Installation of Grinding Disc
Install the grinding head when the grinding disc and the valve orifice preliminarily aligned center to center,
meanwhile, adjust the position of valve body so as to preliminarily adjust the grinding surface of the
build-up welding layer of the valve.
The steps are as below:
1) Firstly install a grinding head on the grinding disc at a position enough to cover the build-up welding
surface by the grinding wheel. After installing the grinding head, manually rotate the grinding disc slowly
for one turn around the sealing ring and carefully check whether the grinding head covered the entire
grinding ring. It must be correctly adjust the width covered by the grinding head on the grinding disc and
properly record the positioning parameter well-tuned (screw fixation location).
2) Install the second and third grinding heads as per the parameters set for the first one. When
repairing large size valves, it can use six ∅50×25×13 grinding wheels or 3 ∅75×32×20 grinding wheels.
3) Collision or friction between the extension block where grinding wheels to be installed and the valve
guide rib are strictly forbidden and avoided, and a least 5mm interval should be provided. Friction
between the upper end of the extension block and the sealing surface at the upper section of the valve
body is not allowed, so as to ensure the smooth operation of the grinding head. Screws to secure the
extension block must be tightened to avoid flyout when the grinding head runs in high velocity.
4) The installation method of the chamfering grinding head is same to that of plane grinding head, but
you need to align it with prudence to ensure the internal and external roundness of the sealing ring after
chamfering operation.

9 Regulation of Grinding Precision
Grinding precision refers to the sealing precision in general for assembling of the grinded valve sealing
surface and the wedge disc after machining out the plane by placing it on the wedge block. The center
line of the valve sealing surface and the center line of the wedge block must be coincident to make the
precision of the wedge disc and valve sealing surface up to standard to meet the requirements of zero
leakage sealing performance, or otherwise, there would be angles or broken line on the seal belt. In
short, valves placed on the wedge block must be aligned center to center and line to line, no deviation
and offset is allowed. Method to control the precision: firstly hold the lower end of the guiding ruler close
to the guiding plate and take it as the basic reference and hold the upper end of the guiding ruler on
close to the plane covering the two screw holes at the bottom of the middle flange, then, adjustment
should be made if there is clearance at the left or right side, which indicates the valve is not aligned
properly on the wedge block. Specifically, you should hammer the backside of the middle flange with
clearance or use other means to hold it close to the middle flange and eliminate the clearance, make it
match perfectly. When everything is done, fix the valve on the wedge block with the bolted pressing
plate.

10 Grinding Procedures
Velocity + grinding wheels are the key elements for the grinding function, and the amount of feed of
grinding operation is much smaller than that of turning operation. Grinding operations for the work
pieces made by common type grinding machines are based on turning, milling operations, which are to
increase the precision of the work pieces, while the grinding operations made by Re-Top’s valve
repairing grinder are for the valve sealing surface with stainless or cement carbide build-up welding
layers, totally by grinding and no extra processing from preliminary grinding to fine grinding. It is where
our grinder is uniquely different to other brands. The design philosophy, structure, grinding functions and
operations of the grinder differs to others.
The operation method of this grinder is as below:
10.1 Feeding for Preliminary Test (Grinding Wheel)
Unprocessed build-up welding surface is uneven, and the salient points on it will be grinded off one by
one through intermittent grinding operation. As big impact force to the grinding wheel will be generated if
feeding too fast during preliminary grinding period and then cause damages and cracks to the grinding
wheel easily, hence, trying of the appropriate amount of feeding step by step is necessary. The specific
practices are: rotate the hand wheel on the grinder body with right hand in counter-clockwise direction
(indicated by the arrow), meanwhile, rotate the spindle flange plate or grinding disc extension rod with
left hand, so as to learn and get hold of the contacting conditions of the work pieces. The grinding wheel
would contact the grinding surface if heard slight swishing sound in the valve chamber, then, you can
stop rotating the hand wheel and retract to wait for power-on.
10.2 Power-on for Grinding
Power on the grinder, lock the columns, and regulate the speed governor (potentiometer). Feed steadily
with constant velocity when the revolution of the spindle reached 1000/Min, and increase the velocity
gradually along with the velocity consumption of the grinding wheel, and then you can feed with
constant velocity when it reaches 1200/Min-1500/Min. You can retract and power off the grinder when
the sealing surface is bright and smooth, and the weld marks disappeared and it width reached a proper
level. Next, replace the grinding head with a chamfering grinding head to conduct internal and external
chamfering grinding and change into the previous grinding head to conduct positioned grinding with
constant velocity when chamfering grinding is completed. Conduct fine grinding with constant grinding
until the completely disappear of friction sound as a result of grinding operation when the handle rotated
below the hand wheel and stopped rotation.

11 Grinding Materials and Grinding Wheels
11.1 Selection of Grinding Materials
There are so many of welding materials for the valve sealing ring, such as stainless steel, cement
carbide, cobalt-based, tungsten carbide etc., which has different functions with respect to their acid
resistance, alkali resistance, heat resistance, corrosion resistance and wear resistance, and different
hardness. Thus, it is necessary to select appropriate grinding materials specific to the properties and
hardness of the welding materials, for example, monocrystalline fused alumina, fused alumina zirconia
and pink fused alumina grinding wheels can be selected for 304, 316 stainless steel. For another
example, green silicon carbide grinding wheel should be used for cobalt-based and tungsten carbide
welding materials with a hardness over HRC50. The grain size of the grinding materials for the grinding
wheels should be 46#.
11.2 Selection of Opening, Specification and Hardness
1) Flaring cup grinding wheels are suitable for plane grinding, particularly for intermittent grinding of
uneven work pieces;
2) Small size grinding wheels are suitable for valves with a smaller cavity and their specifications are
BW50×25×13 and BW75×32×20, and the specification for chamfering plat grinding wheel is
BW100×60×20.
3) Medium soft grinding wheels, marked as L, should be used for welding materials with hardness over
HRC50, and soft grinding wheels, marked as K, should be used for welding materials with hardness
over HRC50.

12 Cooling of Work Pieces
Grinding heat, reflected by the grinding temperature, will be generated in the process of grinding due to
internal friction of the sealing weld materials and external friction of the grinding wheel. Grinding heat is
not obvious during intermittent grinding operations and the grinding temperature is not too high;
however, the width of the sealing face get more and more clear along with the gradual grind-off of the
salient points on the build-up welding layers of the sealing ring, and then the grinding temperature will
increase accordingly. Particularly, the temperature at the grinding area will usually reach 1000℃ –
1500℃ when intermittent grinding finished and the build-up welding layer flatted, therefore, sufficient
cooling must be made.
The function of the cooling fluid is to flush the abrasive dust and abrasive grains to avoid scratches to
the grinding surface or blocking of grinding wheels. The cooling fluid also has lubrication effect, which
could reduce the friction between the abrasive grains and the surface of the work pieces and improve
the surface smoothness of the work pieces.
12.1 Formula of Cooling Fluid (for reference only)
12.2 Type of Cooling
1) Water tank + water suction pump, cooling with circulation water.
2) Provide intermittent artificial cooling with water stored in plastic bottle (cooling fluid prepared).
Soda (soda ash) 1%
Sodium Nitrite 0.25 — 0.5%
Water 98.75 — 98.5%

13 Wedge Disc Manufacturing and Assembly
Before turning the wedge discs after build-up welding or spray welding, it should first measure the
precise opening size of the big end and small end of the sealing ring of the valve body, in another word,
it should preliminarily get the thickness of the big end and small end of the wedge disc and provide a
sound basis and reliable parameters.
The methods are as below:
1) Apply build-up welding on one side of the wedge disc and machine out the plane through turning
machine with special tools, then, apply build-up welding to the other side and precede the turning
process. It should be noted that internal and external full circle build-up welding and repair welding for
surface layer should be made to the wedge disc to avoid welding notches or sags.
2) Repeat the turning process for several times coordinating with the valve sealing surface machining
process when turning the wedge disc, i.e. adjust and correct its position on the wedge block with the
dial gage based on the squeezing mark on the sealing belt of the wedge disc, so as to align with the
center of the circle and realize the alignment as shown in Fig. 13-1 and then to eliminate the included
angle and guarantee the goodness of fit and contacts between the valve sealing surface and the wedge
disc.
3) Fine grinding should also be made to the wedge disc with special grinding tools without removing the
repairing clamping fixture when turning of the wedge disc is completed, or alternatively to unload it to
conduct lapping.
4) Put the wedge disc into the valve chamber to seal and assembly it and conduct preliminary seal
test with city water; and overall valve assembly can be made when there is no overflow of water drops
and no moistures.
Fig. 13-1 Alignment of Valve Body and Wedge Disc

14 Electrical Installation
14.1 Overview
The power input, power output, rpm display, speed regulation and overload protection, safety protection
of the driving shaft motor are controlled by the frequency converter, and only power indicator, power
switch, potentiometer, air switch, AC contactor, leakage protection switch are installed on the outside
panel.
14.2 Electric Circuit Diagram

15 Matters Need Attention
■ As there is certain angle between the vertical grinding disc extension rod and the valve body slightly inclined
on the gradient block and the space between the grinding disc and valve channel is small, it requires
handling the valve body for several times to adjust the grinding disc to put it into the valve chamber. In this
process, collision or friction between the grinding disc and valve wall are not allowed, or otherwise the
precision of the grinder will be affected.
■ Operator should not face the middle flange of the valve during grinding operation to avoid injury as a result of
broken grinding wheels.
■ Although the transmission shaft lock could facilitate the installation of the grinding disc and grinding head
while the grinder is not running, its use while the grinder is in operation is forbidden.
■ Collision between valve body and the grinder body or flange plate on the transmission shaft are not allowed,
regardless which kind of hoisting assembly is used, when installing the valve on the repairing table.
■ Extension block for the grinding head should be placed on the groove for grinding disc and retaining screws
should be tightened to avoid personal injury due to flyout of grinding head during operation.
■ Dusts, sands and coolants on the repairing table, columns, gradient blocks and grinding head should be
cleaned and maintained with machine oil before going off duty.
Patented Product, Counterfeiting Not Allowed!

Operation Manual For Valve Repairing Grinder VRM-PM800B

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