08-Conv Valves Product Info

8/6/2019 08-Conv Valves Product Info

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BHARAT HEAVY ELECTRICALS LIMITEDWRITE-UP ON CONVENTIONAL VALVES

INTRODUCTION

BHEL started the manufacture of valves at the Tiruchy complex, along with the

manufacture of boilers in 1965. The conventional Gate, Globe and Check valves

manufactured were initially intended for use in Thermal Power Plants. Subsequently, the

design and production capabilities were systematically upgraded to include Safety

Valves, Safety Relief Valves, Quick closing Non-return Valves, HPLP Bypass System

and Oil Field Equipment. The scope for supply of these valves has been extended to

industrial markets such as chemical, petrochemical, fertilizer plants, Refineries, nuclear

power plants.1.1 PRODUCT RANGE:-

The Valve Plant manufactures Cast and Forged Steel Valves for a variety of

applications. The product range under design and manufacture include the following:-

Gate, Globe and Non-return valves for pressure ratings up-to 4500 class and

temperatures up-to 540'C.Safety and Safety Relief Valves with set pressures up to 220 Kg/sqcm and

temperature up to 570'C.


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2.0 CONVENTIONAL VALVES

Valves are mechanical devices designed to direct, allow, disallow, mix or

regulate the pressure, flow or temperature of a process fluid. The basic function of a

valve is to Isolate Flow as the Value Engineering experts put it in Verb -Noun form. This

article is intended to give a over-view of the general valves being manufactured at BHEL

and also to help the process Engineer to identify the valve he needs for an application.

Sl. Valve Type Valve Category Application

1 Gate Valve Isolating Valves Used to isolate the line. i.e. FullyClosed or to stop the flow or fullyopened to allow the flow.

2 Globe Valve

3 Swing Check Non-ReturnValves

Allows the medium to flow inone direction. When reverseflow occurs, the valve closes.

4 Piston Lift Check

5 Regulating Regulating Valves Used for Flow QuantityRegulation

GATE VALVE

GLOBE VALVE


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2.1 MATERIAL FORM OF VALVE BODY:-

1. FORGED VALVES : Valve sizes of 2 & below are made of forgings.2. CAST VALVES : Valve sizes of 2 & above are made of castings.

2.2 VALVE SIZES

Valve sizes are identified by its equivalent nominal pipe size (NPS) of the piping on

which these valves are mounted. In BHEL, valves are manufactured from 1/4 to 36 of

valve sizes. Forged valve category includes 1/4 to 2 and Cast Valve category includes

2 to 36.

2.3 PRESSURE - TEMPERATURE RATING

Maximum permitted pressure of the medium with respect to its temperature are given in

the Standard ASME- B16.34 for the corresponding valve body material. These ratings

are specified by CLASS NUMBER. The strength of the material reduces with increase

in temperature and the permissible pressure also reduces with increase in temperature

of the medium.

The class ratings identified in ANSI-B16.34 are as follows: Class 150; Class 300; class


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CHECK VALVE GENERAL ARRANGEMENT

2.4VALVE BODY MATERIAL:

Valve body is made of following materials. Type of material selection depends on

the fluid / mediums temperature and /or its corrosive nature.

1. Carbon Steel used upto -425 C / 800 F.2. Alloy steel used upto 550 C (593 C) / 1100 F

3. Stainless steel used upto 600 C- mostly used for corrosive nature of medium.


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Socket welded & Screwed end type of connections are provided for valve sizes 2&

below.

Flanged ends and Butt-welded end type of connections are given for valve sizes 2 &

above.

2.6 SPECIAL FEATURES :

In addition to the basic features to specify the valve namely Valve type, Size, Material of

Construction, Rating, End Connection & Operation, host of special features are

available of which few are elaborated below :

2.6.1 OPERATION:-Isolating Valves and regulating valves are operated by one of the following

methods, which depend on the size of the valve & the system requirement.

* 2.6.1.1 Hand wheel operation - generally provided on many of the valves.

* 2.6.1.2. Gear operation - higher size valves are provided with gearbox for every

operation.

* 2.6.1.3. Motor operated - valves are provided with electrical actuators for remote

operation. Higher size valves are generally provided with electrical actuators for ease of

operation.


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2.6.1.5. Extension spindle operation - When the operating floor level is very much

above the valve (axis), a stand with hand wheel or electrical actuator is provided at the

operating level & its spindle is connected to valve.

2.6.3 SPECIAL FEATURES :

a) Gland sealing arrangement


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from leaking to the atmosphere. In this arrangement a little amount of leakage can occur

over a period of service of the valve.

When the medium is toxic or like NH3, H2S. Such small leaks thro stuffing box is

avoided by providing a gland sealing arrangement.

Generally a lantern ( a fluid jacket ) is introduced at the middle of the packing s

and dissolving medium / water is allowed to circulate. This dissolves the leaking

medium, which is connected thro leaking medium, which is removed thro connected

piping.

When the valve is used in vacuum service, this arrangement eliminates the

outside air getting into the valve body.


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3 LOCKING ARRANGEMENT:

Wherever the System warrants that the operation of the Valve shoud not be done by

unauthorised personnel, locking arrangements are provided to keep the Valve in either

open or closed position until operated upon. Hook type for Gate Valves and chain type

for other Valves are common.

4 INDICATOR ARRANGEMENT:


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5 By-Pass Valve ARRANGEMENT:

By-pass valve arrangement is provided in valves to equalize the pressure in both

the inlet and outlet of the valve so that the valve can be opened easily. This is also

helpful in warming up the outlet pipeline for preventing sudden thermal shock.

6 Pressure-relief ARRANGEMENT:


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7 Balance Hole Arrangement

The purpose of providing a balance hole arrangement is similar to that of

providing a PRV. Wherever a PRV cannot be provided and a similar chance of fluid

thermal expansion exists, a balance hole is provided by making a small hole in the

wedge connect the Bonnet and the inlet/outlet.

8 D i H l A t


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Preventive Maintenance of Valves

All Types of Valves:

1.It shall be ensured that no solid foreign particles are present either in the valves orpipelines before

the valves are installed to avoid damage to sealing surfaces.

2. Valves shall be properly stored. The end caps shall be kept in position and shall beremoved just

before installation only.

3. All the valves shall be serviced during annual shut down by experienced servicepersonnel.

4. The following remedies are available for technicians at site to solve the minorproblems. If the

problem still persists, Valve services of BHEL shall be contacted

Conventional valves:

1. Gland leakage

Gland bolts are to be tightened evenly, as soon as leakage is noticed, and arrested.

Additional packing shall be added, if necessary (at the next available shut down)

If l k i t ki h ll b l d ith t f ki


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4. VALVE PASSING

Valve passing is mainly because of damaged sealing surfaces, due to entrapment offoreign particle between wedge / disc and body seat. The same is to be attendedby lapping of both the body and wedge / disc seat. It is preferable to attend thevalves immediately after steam blowing, in case the valves are involved during steamblowing operation

5. Actuator setting:All Motorised Valves are set at BHEL for the required Torque/ Limit values

and shall not be disturbed at site. These Values can be altered only by trainedpersonnel when essential.

All gate valves of size 100mm and above and pressure rating 1500 CL and aboveshall be set for POSITION SEATING . i.e, valve closing shall be by CLOSEPOSITION limit switch trip only. The close Torque limit shall be connected as

backup/parallel connection.Valve Opening shall be by OPEN POSITION Limit switch trip.

All other gate , globe and regulating valves shall be set for TORQUE SEATING only.i.e, valve closing shall be by CLOSE TORQUE limit switch trip ony. The closeposition limit should NOT be connected as backup/parallel connection.Valve Opening shall be by OPEN POSITION Limit switch trip.

For all Gate valves the during initial 5% opening, of the valve from its close position,the OPEN TORQUE LIMIT SWITCH should be bypassed to ensure smooth openingof the vale.

Th d O l d l (OLR) h ld b d h l


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VALVE ACTUATOR SETTING PROCEDURE

Ref: VAL/ACT_SETPROC/Rev:02

1.0 Open Limit switch setting:In open direction the stem movement shall be terminated (stopped) by open limitswitch OLS1.

While setting the OLS1 the following points shall be taken care.1. When the actuator supply is tripped by limit switch, the stem will move a

little further distance before coming to stop. This distance (say inertiadistance) shall be measured by trial and error, as this varies from actuatorto actuator.

2. The stem shall not hit the back seat when fully open. The clearanceneeded from back seat (say Back seat clearance) is given below forvarious valves.

TOA Valve of 1500C & above and size 2-1/2 and above

8mm

Forged Steel Valves -size 2 & below 1 mmCast Steel Valvessize 2 & above 3 mm

1.1. Setting procedure:

1. Open the valve with hand wheel such that the stem stops by touching theback seat and no more opening is possible.

2. Rotate the hand wheel in close direction move the valve stem to get the back seat clearance through a distance as indicated above Mark this

Valve Back seatclearance


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2.2 Position seated valve:While setting the CLS1 the following points shall be taken care.

1. When the actuator supply is tripped by limit switch, the valve will move a

little further distance before coming to stop. This distance (say inertiadistance) shall be measured by trial and error , as this varies fromactuator to actuator.

2. The valve shall not have metal to metal contact when fully closed. Theclearance needed from bottom position (say Close seat clearance) isgiven below for various valves.

2.2.1 Setting procedure:1. Close the valve with hand wheel such that the stem stops and no further

movement is possible.2. In open direction move the stem to get the close seat clearance. Mark

this point on the stem.3. Now open the valve little further for a rough inertia distance. Now set the

Close limit switch (CLS1) at this point.4 C t th t t t th i i di l d N dj t th

Valve Close seat clearanceTOA Valve of 1500C & above and size 4 to 6 5mm

TOA Valve of 1500C & above and size 8 to 10 7mmTOA Valve of 1500C & above and size 12 and above 9mm


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2. In open direction, rotate the hand wheel to move the valve stem to get the Bypass clearance. Now set the Close limit switch (CLS1) at this point.

3.0 Aux. Limit switch (Intermediate limit switch) setting.Aux. Limit switches are used for indication of end position. They may also beused for any intermediate position indication/interlock as required by customer.

It is necessary to set these limit switches at respective end position to avoid anyambiguity at site.

1. Procedure for setting of aux. Limit switch for open direction (OLS2) issame as that of OLS1, and the OLS2 switch is to be set at the sameposition of OLS1.

2. Procedure for setting of aux. Limit switch for close direction (CLS2) issame as that of CLS1, and the CLS2 switch is to be set at the sameposition of CLS1.

4.0 Torque switch settingThe open torque switch OTS and close torque switch CTS are to be set to thevalue given in VAD.

5.0 Dial Position Indicator setting.The full close/open position of dial position indicator shall be set at the pointwhere the valve stem comes to a complete stop after being tripped undernormal conditions through limit/torque switch in the corresponding direction. EPTif applicable also to be set to the same position as above.

Th b tti di ti ll t d i S t P i t di


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Documents

08-Conv Valves Product Info