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BHARAT HEAVY ELECTRICALS LIMITED PRODINFO:

TIRUCHIRAPPALLI - 620 014. of 13

PRODUCT INFORMATION CONVENTIONAL VALVES and SAFETY, SAFETY RELIEF VALVES

PRODUCT INFORMATION

VALVES & SOOT BLOWERS

Bharat Heavy Electricals Limited

ISSUED BY PRODUCT ENGINEERING VALVES – BHEL TIRUCHY




INDEX OF CONTENTS

Section Product Covered Page No.

01 INTRODUCTION 03

02 CONVENTIONAL VALVES 04

03 SAFETY & SAFETY RELIEF VALVES 09





Section 1.0 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 3500 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.

HPLP Bypass Control System up to 500 MW. Full bore valves, Surface Wellheads, X-mas trees up to 10000 psi. Sub-sea wellheads, Mudline suspension systems up to 10000 psi. Casing support systems for Oil Exploration and Production. Quick Closing Non-Return valves (QCNRVs) up to 600 Class. Soot Blowers Silencers and Water Level Gauges.

1.2 TECHNOLOGY :

BHEL has adopted a two pronged strategy of selective technology acquisition and in-house R&D based development to introduce contemporary technology. Technology transfer agreements were entered into with the leaders in the world in the respective type of valves.





Section 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. Ie. Fully ClosedTo stop the flow or fully opened to allow the flow.

2 Globe Valve

3 Swing Check Non-Return Valves

Allows the medium to flow in one direction. When reverse flow occurs, the valve closes.

4 Piston Lift Check

5 Regulating Regulating Valves Used for Flow Quantity Regulation

GATE VALVE GLOBE VALVE





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 400; class 600; class 900; class 1500; class 2500; class 4500. Class 800 is non listed rating obtained by interpolating class 600 class 900.Increase in class number indicates higher fluid pressure with respect to material.

Forged valves are available in class 800, class1500 & class 2500Cast valves are available in class 150; class 300; class 400; class 600; class 1500; class 2500.

CHECK VALVE – GENERAL ARRANGEMENT





2.4 VALVE BODY MATERIAL :

Valve body is made of following materials. Type of material selection depends on the fluid / medium’s temperature and /or its corrosive nature. 1. Carbon Steel used upto -425C / 800 F. 2. Alloy steel used upto 550 C (593 C) / 1100 F 3. Stainless steel used upto 600C- mostly used for corrosive nature of medium.

Material type (<=2 inch)Forgings

(>=2 inch) Castings

Composition

Carbon Steel Upto 425 C

A105 WCB / WCC C-Mn-Si

Alloy SteelAbove 425 C

F11 - 538 C F22 - 593 C

WC6 - 538 C WC9- 593 C

1 1/4 Cr 1/2 Mo2 1/4 Cr 1 Mo

Stainless Steel 600 C

(304) / 316

CF8 CF8M

18Cr & 8Ni16Cr 8Ni 2Mo

A217-C12A material (Cr-Mo-V Steel) also developed to cater to Super-critical boiler applications.

2.5 END CONNECTION Valve assemblies are mounted on pipe lines by the following means: 1. Socket weld ends 2. Screwed ends 3. Flanged ends 4. Butt welded ends.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 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. 1. Hand wheel operation - generally provided on many of the valves. 2. Gear operation - higher size valves are provided with gearbox for easy operation. 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.





4. Chain wheel operated - When operating floor level is very much below the valve (axis) chain wheel with chain is provided for operation. 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.

2.7 SPECIAL FEATURES : 1. Gland sealing arrangement,2. Limit Switch arrangement,3. Locking Arrangement,4. Indicator Arrangement, 5. By-Pass Valve Arrangement, 6. Pressure Relieving Arrangement, 7. Balance Hole Arrangement,8. Drain Hole Arrangement .

2.7.1 Gland Sealing Arrangement: Valve stem (operating element) is connected to Wedge / Disc (closing element) at one end, and connected to handwheel / actuator (actuating element through yoke bush for opening /closing the valve). Disc / Wedge is kept inside the pressure part while the actuating elements are kept outside the pressure part. A Stuffing box is provided at the bonnet of the valve, allows the stem movement & at the same time arrests the medium 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 packings 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.

2.7.2 Limit Switch Arrangement :

Two limit switches are mounted on a framework, which is connected to the valve yoke. A lever that is connected to the valve stem actuates the respective limit switch, when the valve is in fully opened / fully closed position, which in turn gives signal to the control room for necessary use.


pe-valves, 01/03/-1,




2.7.3 Locking Arrangement :

The valves may be in a location where it is necessary to ensure that the valves are either in open or close position as desired and this condition shall not be altered either accidentally or unknowingly. In such a case, the valves are provided with locking arrangement. The locking arrangement is generally hook type for cast Gate Valves and it is chain type for other valves.

2.7.4 Indicator Arrangement :

It may be desirable in some cases to know the position of the valve ie., whether it is fully open or closed or partially open condition. This is an optional feature in manual hand wheel operated valves. Generally all BHEL make Gear operated valves are provided with indicator arrangement.

2.7.5 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.

2.7.6 Pressure-relief Arrangement:

Pressure relief valve arrangement is provided in valves to prevent fluid thermal expansion when the valve is in closed condition. This is carried-out by a PRV line connecting the inlet / outlet of the valve with the Bonnet above the Wedge.

2.7.7 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 to connect the Bonnet and the inlet / outlet.

2.7.8 Drain Hole Arrangement

When the system warrants draining of the valve by removing the sediments accumulated during service of the valve, a drain hole is provided at location G (down most part of the valve) with a suitable plug/ pipeline.





Section 2.0 SAFETY & SAFETY RELIEF VALVES

2.1 INTRODUCTION :

Safety and Safety Relief Valves (SV & SRV) are automatic pressure relieving devices used for relieving the excessive pressure build up in Pressure Vessels. The basic function of a SV is to prevent the system pressure in a steam generator from exceeding a predetermined value by automatically discharging the steam as soon as the set pressure is attained. Besides operating at the set pressure, the SV should be able to discharge the full evaporative capacity of the boiler to avoid the possibility of continued pressure build up. Various National and International codes pay heavy attention towards the selection,design, manufacture, testing and performance of SV on boilers and pressure vessels. Safety valves are used in boilers mainly in the following locations : Boiler drum, Superheater headers, Reheater inlet & outlet Headers, Soot blower line, PRDS stations, CBD tank, Deaerator , CRH line to deaerator, etc.

2.2 CLASSIFICATION OF PRESSURE RELIEF VALVES :

Pressure relief valves can be classified as follows :(a) Safety Valves (b) Relief Valves (c) Safety Relief Valves.

(a) Safety Valves (SV) : SV is an automatic pressure relieving device actuated by the static pressure upstream of the valve and is characterised by the rapid full opening or the pop action. It is used for Gas or Vapor service and is used mainly in Boiler applications.

(b) Relief Valves (RV) : RV is an automatic pressure relieving device actuated by the static pressure upstream of the valve and open in proportion to the increase in pressure over the opening pressure. It is primarily used for liquid service.

(c) Safety Relief Valves (SRV) : SRV is an automatic pressure relieving device which may be used either as a safety or relief valve depending upon application and the medium used. SRVs are usually of closed bonnet type to prevent escape of medium to surroundings. Special design of SRVs are available for used in back pressure systems. Pressure relief valves are also classified as Weight loaded pressure relief valves, spring loaded pressure relief valves and pressure assisted pressure relief valves based on the loading pattern of the valves. Of these the direct spring loaded type is the one that is most commonly used in practise for high pressure applications.





2.3 CODES GOVERNING SAFETY VALVES :

Various National and International codes are available which govern the design , manufacture, testing and performance of Safety valves. The codes are based on the past experience in the field and provides safety for operation and working of boilers and pressure vessels. The important codes applicable are :

(a) Indian Boiler Regulations (IBR), (b) ASME Section I for Power Boilers, (c) ASME Section VIII for Unfired pressure vessels, (d) API Standards 526 & 527, (e) BS 6759 etc. 2.4 SELECTION & SIZING OF SAFETY VALVES :

The factors to be considered in the sizing and selection of SV for steam generators for use in India are as follows :

(a) The valves must confirm to the Indian Boiler Regulations of 1950 with all its amendments. (b) Spring loaded valves of FULL lift type are preferred. (c) The total relieving capacity of the drum and superheater svs should be greater than or at least equal to 100 % of the MCR. (d) The drum safety valves shall discharge at least 75% of the MCR and the superheater svs shall discharge around 20 % of the boiler MCR. (e) Reheater outlet safety valves should relieve at least 20 % of the reheater flow and combined reheater inlet and outlet valves must discharge at least the total maximum flow through the reheater. (f) Generally welded inlet valves are preferred and the final selection of the SVs is done to yield the best economy. (g) An electromatic relief valve (ERV) is provided on the superheater outlet / reheater outlet to take care of the pressure surges in boiler operation. This valve is set to open prior to the spring loaded SV in the location concerned and thereby prevents the frequent lifting of the SV. However the discharge capacity of the ERV cannot be accounted for satisfying the code requirements of the combined relieving capacities as indicated in clause (c) and (e) given above.

2.5 PRODUCT REQUIREMENTS :

The SV should be designed, manufactured and tested to meet the following product characteristics. Tests are to be conducted with saturated steam for acceptance of the product.





(a) The valve, up to the seat, should be hydraulic tested to 1.5 times the design pressure of the valve. (b) The valve should be set to the correct set pressure as envisaged in the design. Tests are to be repeated to assure the valve setting. (c) The valve should not leak at 94% of set pressure. (d) The discharge capacity of the valve should be proved by Type testing as per appendix 'L' of IBR. (e) The lift of valve should be measured and proved during type testing. (f) The closing down pressure should also be demonstrated during the type testing to achieve blow down values with 5% (IBR) (g) Also the valve details, materials of the parts used and test data are to be reported in Form-III c and Item 11 of IBR for approval of the product in utility and industrial boilers.

2.6 CONSTRUCTION FEATURES : BHEL Safety and Safety relief valves are manufactured in collaboration with M/s Dresser Industries of USA. For the power boiler applications, the following safety valve product ranges are manufactured and meets requirements of IBR :

2.6.1 1700 SERIES SAFETY VALVES :


LEVER

SPINDLE

SPRING

Y OK E

SPG.ADJ USTER

DISC

BODY

DISC HOLDER

GUIDE

CAP

ADJ .RING PINS

UP.ADJ .RING

LO.ADJ .RING




This design of valves are mainly used in the Boiler drum, superheater and reheater circuits.

(a) Inlet nozzle is profiled to give the maximum discharge.

(b) Thermo disc provides extremely tight closure and compensates for temperature variation around the periphery of the seat in steam service. Thermal stresses are minimised, seat distortion is prevented and permanent tightness is achieved.

(c) Compensated Back pressure assisted closing feature results in positive and precise closing of the valves to ensure blow down values within Code requirements.

(d) Independent adjusting means for Blow down (upper adjusting ring) and clear Popping action (lower adjusting ring) ensures the best setting of the valves.

(e) Locking arrangements for the spring compression and adjusting rings ensure undisturbed settings.

(f) Hydrostatic plugs are provided for hydraulic testing of the boilers with valves installed in site. The HT plugs are to be replaced with disc prior to steam testing of the valves.

2.6.2. 1811 SERIES SAFETY VALVES :

This is a low cost safety valve product line with two ring control. The valves are designed only up to a maximum set pressure of 700 Psi. These valves are used in the following locations :

(a) Soot blower steam header, (b) PRDS stations, (c) CBD tanks etc.

These valves are also available with thermodisc design for better performance in high temperature applications.





SAFETY RELIEF VALVES

2.6.3 1900 / P SERIES SAFETY RELIEF VALVES :

These valves are of the closed bonnet design to all pressure and open yoke design for use upto 600 psig applications. Thermo discs are used for better leak tightness of valve seats. These valves are selected for pipeline applications for boiler PRDS systems, deaearators, Gland seal lines etc.

2.6.4. 1900 SERIES SAFETY RELIEF VALVES :

These valves are mainly used in process industries. Typical application in power plants are for feed water heaters, oil systems and compressed air services. These are not covered under IBR scope.


CAP

SPG.ADJ USTER

WASHER

SPRING

SPINDLE

GUIDE

DISC HOLDER

ADJ .RING PIN

ADJ .RING

NOZZLE

BASE

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