Modular Sludge Lancing Equipment for Mushroom Type ... - BARC

BARC Newsletter

Modular Sludge Lancing Equipment for Mushroom Type Steam Generators of Pressurised Heavy Water Reactors (PHWRs) Shirish Nawathe, K.L. Soni, J. Aparna, J.N. Kayal, B.B. Rupani, L.R. Mohan and H.P. Vyas Reactor Engineering Division Bhabha Atomic Research Centre

Abstract Periodic sludge lancing enhances steam generator life by mitigating corrosion between its tubes and tube sheet. The present modular sludge lancing equipment has been designed to dislodge and remove sludge from secondary side of tube sheet of mushroom type steam generators of PHWRs. This equipment comprises of a closed loop De-mineralised Water Circulation System (DWCS), highpressure remote lancing Jet Manipulator Assembly (JMA) and Remote Visual Inspection System (RVIS). This entire system including JMA & RVIS is monitored and maneuvered by electronic instrumentation and PLC based supervisory control units.

Introduction

T

HE EQUIPMENT IS BASICALLY DIVIDED into six process modules, specially designed JMA, I & C panels, electrical power supply panel and RVIS. All dimensions of modules are within 2.8 m. The modules are interconnected with suitable flexible hoses with

cam type Quick Release Couplings (QRC). Successful working of sludge lancing equipment is demonstrated on a steam generator mock up assembled in Engg Hall-3 for this purpose. The schematic flow diagram of the sludge lancing equipment is shown below.

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System Description The high-pressure water jet dislodges the sludge from the secondary side of Steam Generator tubes (of limited heights ~~ 150 mm) and tube sheet face, which gets collected on the bottom tube sheet. This is extracted to Sludge Tank (ST-1) by self-priming air operated double diaphragm pump (EP-1 or EP-2) capable of handling 0 to 18.0 m3 / hour of sludge water. The Sludge Tank (ST-1) has in-built filtering (wire mesh of size 200 microns) provision to collect the sludge particulate above 200 microns. The flow of sludge water is from out side to inside. The provision has been made to clean the tank using wire brushes from three hand holes. The provision also exists to remove the special filtering part outside for cleaning purpose as and when required. A set of lowpressure hoses of 40 (from SG to diaphragm pump) & 50 mm size (for interconnection of all other modules), pressure gauges, thermowells and safety devices such as relief valves are provided. The sludge water is fed from ST-1 to a Rotary Cleaner (RC) for the separation of particulate above 100 microns with the help of a centrifugal booster pump (BP-1: 18 m3 / hr at 5 kg/cm2). The rotary cleaner consists of motorised rotary filter drum and a scraper. It is basically useful when liquid is heavily loaded with sludge. Sludge is collected into the bottom hopper and periodically withdrawn by operating drain valve as and when required. The outlet from the RC is passed through basket filters BF1 (30 microns) & BF-2 (2 microns) or BF-3 (30 microns) & BF-4 (2 microns) and then to the main storage tank (ST-2). The storage tank has a total capacity of 4.0 m3 and is divided into two partial compartments for the sludge settling purpose. Drains are provided for each of these compartments. A central manhole of 600 mm diameter is provided for internal access and cleaning The sludge water is then passed through a compact Plate type Heat Exchanger (PHE) or a bypass line and a cartridge filter CF-1 or CF-2 or CF-3 (each 0.5 micron) with the help of a Supply

pump (SP-1: 18 m3 / hr at 8 kg/cm2) for further finer filtration. A high pressure Triplex Pump (TP: 9 m3/hr at 250 kg/cm2 from main discharge and 6 m3/hr from pump bypass with available Jet Manipulator Assembly and nozzles) feeds the filtered sludge water to SG through Nozzle head as high-pressure jets. The Triplex Pump can operate from 0-250 kg/cm2. The Jet Manipulator Assembly maneuvers the nozzle head. Triplex pump (TP) is connected to valve station by 25mm high-pressure hose and the nozzle head is connected to valve station through a 15mm high-pressure hose. The sludge of the secondary side of SG is cleaned with the help of highpressure water jet stream emerging from eight nozzles of Jet Manipulator Assembly. The total system hold up is about 6 m3 of DM water. The system material of construction is stainless steel and the flexible hoses are PVC with inner ss wire braiding with quick release couplings at the ends. High-pressure hoses are made from metal wire reinforced rubber with high pressure QRC at the ends. During the cleaning process, pH and conductivity of DM water are continuously monitored and recorded on duel channel recorder. DM water is to be replaced if the conductivity exceeds 100 microns Si/cm (micro siemen per centimeter) at increased foaming and if the pH goes out of the range (5 to 10).

Module Description For ease of mobility and accommodations the entire lancing system has been divided into 6 main modules. Each module has been provided with collection trays at bottom to collect small spillage from the system. Spillages from different modules will be collected in a central drain or trench by PVC hoses. The modules are designed for ease of mobility with chassis frame mounted on lockable swivel castor wheels. Suitable jacks have been provided to allow the trolley to take a firm location wherever required. Properly designed lifting lugs/ hooks have also been provided for lifting/ pulling the entire module with help of crane for transportation, loading


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BARC Newsletter and unloading. The six modules are described in following paragraphs.

Module No 1: This module (1.4 x 1.2x 1.34 m) houses two air operated diaphragm pumps (EP-1 and EP-2), suction and discharge piping, associated valves and instrumentation. The provision of supporting suction hose on a magnetic stand exists to avoid obstruction in suction flow.

BF-3 and 2 microns from BF-2 or BF-4. One set of filter assemblies (BF-1 & BF-2 or BF-3 & BF-4) will be on line during lancing operation. The other set of filter assemblies will be either standby or under cleaning as the case may be. The filter bags are made out of polypropylene material and capable of withstanding a pressure of 6.0 Bar.

Module No 2 : This module (2 x 2.5 x 2.8m) houses sludge tank (ST-1), Centrifugal Pump (BP-1), Rotary Cleaner (RC) (suitable to remove particulate of 100 microns and above), associated piping, valves and instrumentation. However, a spare Centrifugal Pump (BP-2) is also available. Module No 3: This module (1.2 x 2.2 x 2m) has a set of Stage-I filter assemblies namely BF-1 & BF-2 and BF-3 & BF-4 in series parallel arrangement. These are bag type filters capable of separation of sludge 30 microns from BF-1 or

Module No 4: Main storage tank (ST-2) occupies the entire space of module No 4 (2.5 x 1.7 x 2m) and is mounted on an open trolley/chassis frame. This has two compartments to facilitate settling of crud


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BARC Newsletter escaped from module No 3. The volume of this tank is about 4.0 m3.

also been provided. The main pump motor control panel and other related accessories are located on this module itself. This pump is mounted on open movable chassis frame.

Jet Manipulator Assembly (JMA)

Module No 5: This module (2 x 2.4 x 1.5m) accommodates a supply pump (SP-1), plate type Heat exchanger (PHE) and a set of stage-II filters (CF-1, CF-2 & CF-3) (suitable to remove particulate of size 0.5 micron and above), associated piping, valves and instrumentation. However, a spare Centrifugal Pump (SP-2) is available.

Module No 6 : This module (1.5 x 3 x 1.5m) houses High pressure Triplex plunger pump (TP) that is most critical assembly of lancing process. An accumulator shall be provided at the discharge end of this pump to smoothen the flow pulsation if desired at a later stage. The pump is equipped with a pressure relief valve to obviate any abnormal pump behaviour. A bypass with pre set pressure device for lowpressure discharge with unloader device on discharge has

The jet manipulator assembly consists of mainly three sub assemblies, namely horizontal positioning device, Lifting device and nozzle head (photograph given below). Each sub assembly is designed to pass through hand hole, having 180 mm diameter and 100 mm wide gap between steam generator shell and shroud. All wetted components of the jet manipulators assembly are made from stainless steel and gripping shoes are made offrom aluminium to avoid damage to the tubes. All three components of JMA are assembled after insertion through a hand hole.

The jet manipulator moves in forward or backward direction along with central no-tube lane to dislodge the sludge and deposits from the tube sheet of the secondary side of steam generator. The nozzle head directs the multiple jets along the narrow inter tube lanes having 3 mm width, on both sides of the central no tube lane. The nozzle can be set to move at different elevations such that the multiple jets will graze along the narrow tube lane to create the sludge lancing action. The provision exists for lancing in both forward & reverse movement of JMA.


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Remote Visual Inspection System (RVIS) The inspection system is based on standard 1/3" CCD B&W/ colour miniature camera module with a suitable lens to carry out the visual inspection of the area after sludge lancing operation.

Mock-Up Facility A full-scale mock-up of more than half of the lower part of the steam generator secondary side has been fabricated to qualify the handling procedure of JMA and RVIS & qualification and training of manpower. The mock-up includes the two hand holes at extreme ends of no-tube lane and one hand hole perpendicular to the No- tube lane. The tubes are arranged in three rows on each side and along the No-tube lane, five rows perpendicular to the No-tube lane and another five rows at 30º/150º from the No-tube lane. The base plate simulates the tube sheet. The mock-up has been made of stainless steel material to avoid corrosion and the tubes are of Incalloy material to simulate the actual tubes of steam generator. The lancing operation can be demonstrated for its satisfactory performance as regards to its accuracy and speed of positioning with the space restrictions on this mock-up. The sludge removal ability can be demonstrated, while maintaining the system parameters.

Performance Testing And Characterisation The entire system has been tested successfully in Hall-3, however, the work for preparation of dummy sludge and simulation of its bonding is being planned. The performance tests shall commence very soon.

Conclusion This equipment has been developed successfully by BARC as an import substitution against a purchase order from NPCIL following a global tender, which meets all the technical requirements of tender specifications.

Acknowledgement The authors are especially indebted to Mr R.K. Sinha, Associate Director, Reactor Design & Development Group for his kind guidance in development of sludge lancing equipment. The authors would also like to express their gratitude to Mr R. K. Modi of Division of Remote Handling & Robotics and Mr P.B.S. Sengar of Waste Management Division for their valuable contributions to design and development of sludge lancing equipment.

This paper was adjudged as the Best Paper in the poster session presented at the 13th Annual Conference of Indian Nuclear Society (INSAC-2002) on "Nuclear Technology Catalyst for National Development", held at Mumbai during October 9-11, 2002


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BARC Newsletter About the authors … Mr Shirish Nawathe, B.E. (Mech) from 28th batch of Training School, is actively working for design & development of mechanical systems/ components required for PHWRs, AHWR, Critical Facility for AHWR, Sub Critical Facility etc. Earlier, he has also worked for technology transfer related activities.

Mr K.L. Soni, B.E. (Mech) from 18th batch of Training School, is actively working for design & development of mechanical systems/ components required for PHWRs and AHWR. He is also working for development of import substitution components.

Ms J. Aparna, B.E. (I & C) from 33rd batch of Training School, is actively working for design, procurement, installation and commissioning of process instrumentation & control for various testing facilities required in support of R & D for PHWRs & AHWR.

Mr J.N. Kayal, B.E. (Mech) from 20th batch of Training School, is working on development of technologies for inspection and repair of reactor components and life extension of the same.

Mr B.B. Rupani, Head, Reactor Coolant Channel Section, RED, is from 17th batch of Training School and has taken a leading role in design & development of various systems and technologies required for in-service inspection, repair and life extension of coolant channels of PHWRs. He is also responsible for development of many technologies regarding AHWR coolant channels.

Mr L.R. Mohan, Head, Instrumentation section, RED, is from 15th batch of Training School and has carried out design, procurement, installation and commissioning of process instrumentation & control for Dhruva reactor, many engg set-ups and IX plan projects.

Mr H.P. Vyas graduated in 1970 from L D college of Engineering, Ahmedabad, in electrical engineering and joined 14th batch of Training School. After successful completion of training, he joined RED. He obtained MBA in 1984 from University of Mumbai. He has sound knowledge of French language. He actively worked for design & development of components & systems of Dhruva reactor. He worked for design of Superconducting Super Collider project in Dallas-Texas during 1991-92. Presently, he is heading Technical Services Section, RED, and working for design & development of AHWR systems.


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