Pressure Testing of API Tanks

Reliance

Procedure for Pressure Testing of API Tanks

EPCMD-2-QM00-JEP-ME-010

01

10.09.2012

00

17.12.2011

Rev

Date

Issued for Implementation Issued for Implementation Description

PPP

KMP / EMK / KSS

SNS

PPP / PKD

PKS / EMK / KSS

SNS

Prepared by

Checked by

Approved by

Reliance Contents 1. Purpose

…………………………………………………………………… ……….……………………...3

2. Scope …………………………………………………………………… ………..……………………………3 3. References …………………………………………………………………… …………………………….3 4. Abbreviations and Terms ………………………………………… …………………………………3 5. Responsibilities ……..……………………………………………………………………………………3 6. Methodology ……….……………………………………………………………………………………..4

EPCMD-2-QM00-JEP-ME-010 00 Confidential © Reliance. All rights reserved

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Reliance 1.

Purpose Different portions of API tanks are required to be tested as per the code requirement to establish the integrity of the Tank. Testing includes welding of bottom plates by vacuum box test, reinforcement plate welds of nozzles by air test, the shell by filling with water and tank roof welds by applying pressure as per approved drawing/data sheet. For better understanding of the code requirement and to provide uniform approach of tank testing, step by step instruction is required regarding the different testing procedures of API tanks. The purpose of this procedure is to define the activities involved in testing, documentation formats and responsibilities and authorities for pressure testing of API tanks.

2.

Scope This procedure covers step by step instructions to perform testing of different components of API tank.

3.

Reference API 620

Design and Construction of Large, Welded, Low Pressure Storage Tanks. Welded Steel Storage Tanks

API 650

Relevant Tank Data Sheet/ Approved Drawings All documents referred in this document shall be assumed as latest revisions.

4.

5.

Abbreviations and Terms DCC

Document Control Center

HOD

Head of the Department

QMD

Quality Management Department

Responsibilities 

Construction

Managers

/

Engineer

in

Charge

are

responsible

for

implementing this procedure in their area.



HOD QMD is responsible for maintaining this procedure.



DCC is the custodian of this document

EPCMD-2-QM00-JEP-ME-010 00 Confidential © Reliance. All rights reserved

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Reliance 6.

Methodology

6.1

Vacuum box testing—General

6.1.1 All Welds shall be visually inspected and cleared by Reliance QMD personnel before commencing for vacuum test. 6.1.2 A notification of intent to perform vacuum box testing shall be submitted by Contractor to Reliance, as per contract condition. 6.1.3 The welds of bottom plates and tank roof welds will be tested by using a vacuum box with a proven soap solution (Approval must be taken from Reliance QMD prior to use) suitable for the detection of leaks. The vacuum box test shall enable any leak in the seams to be positively located by the bubbles or foam formation. The procedure for vacuum testing of fixed roof welded storage tanks as per API 650/620, document no: EPCMD-2-QM00-JEPME-042, shall be followed to perform the test. 6.1.4 The bottom plates shall in any case be tested before the hydrotest of tank. 6.1.5 Adequate lighting shall be provided inside the tank while performing vacuum test, if test is done after tank erection. 6.1.6 Before performing vacuum box test, standing water, weld slag, mud, dirt and other debris, which may prevent bubble formation, shall be removed. 6.1.7 Vacuum shall be applied to the joints using a vacuum box with glass window in the top. The transparent window of the vacuum box shall be kept clean to ensure good visibility while performing the test. 6.1.8 A partial vacuum can be created by means of a hand or motor-driven vacuum pump. 6.1.9 The gauge in the vacuum box should register a partial vacuum of at least 3 psi. (g) Unless specified otherwise in the engineering specification. A calibrated pressure gauge shall be used to ensure that pressure will not exceed the

specified limits.

6.1.10 The desired minimum partial vacuum shall be maintained till the inspection of the weld length is complete with a minimum period of 25 seconds unless specified otherwise in the engineering specification. 6.1.11 If any leak exists, it shall be located and repaired and the repaired area shall be re-tested. 6.1.12 Form EPCMD-2-QM00-FMT-ME-046 will be used to document performance of vacuum box testing. EPCMD-2-QM00-JEP-ME-010 00 Confidential © Reliance. All rights reserved

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Reliance 6.2

Inspection of Reinforcement – Plate Welds

6.2.1 All reinforcement pads shall be tested after PWHT. 6.2.2 Weld slag, mud, dirt and other debris shall be removed from the weld joints which may prevent bubble formation. 6.2.3 A pneumatic pressure of 15 psi (g) maximum, unless specified otherwise in the engineering specification, shall be applied between the tank shell and the reinforcement plate on each opening, using the telltale hole. 6.2.4

A calibrated pressure gauge shall be used to ensure that pressure will not exceed the

specified limits.

6.2.5 While each space is subject to the pressure, a proven soap solution (Approval must be taken from Reliance QMD prior to use) suitable for the detection of leaks shall be applied to nozzle welds and reinforcement welds inside and outside the tank in accordance with code requirements. Form EPCMD-22

QM00-FMT-ME-069 will be used as an acceptance record for this test. 6.2.6 The pneumatic pressure shall be maintained till the inspection is complete with a minimum period of twenty-five (25) seconds, unless specified otherwise in the engineering specification, for the formation of bubbles/foam, which will indicate leakage. Should any leak exist, it shall be repaired and the reinforcement pad shall be re tested.

6.3 2

Water fill Test Ensure the requirements of EPCMD-2-QM00-JEP-ME-026, ―Procedure for Quality control of Site Erected Atmospheric Tanks‖, before starting water fill test.

6.3.1 Water fill testing of tanks shall be performed in accordance with the relevant API code and to any limiting test information identified in approved drawings. After fabrication of the tank, the completion of all the activities specified in the Inspection & Test Plan (ITP) and NDT, pressure test clearance will be given jointly by Reliance execution engineer and Reliance QMD personnel. Before starting the water fill test, Contractor shall submit a comprehensive test procedure for approval. When tanks are hydrotested using seawater, temporary sacrificial anodes are to be installed in accordance with tank data sheet requirements. 6.3.2 A notification of intention to pressure test shall be submitted to Reliance in advance as per contract. EPCMD-2-QM00-JEP-ME-010 00 Confidential © Reliance. All rights reserved

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Reliance 6.3.3 The sequence of filling, emptying rates and holding periods for tank hydrotesting shall be identified in the Contractors submitted test procedure. 6.3.4 An analysis of the test water shall be carried out together by Reliance and Contractor with any proposals to use chemical inhibitors prior to testing. For tanks fabricated from austenitic stainless steel test water must not contain more than 50 ppm of chlorides unless otherwise specified in engineering specification. 6.3.5 Roof Manhole and/or other roof fittings having as large an area as the water inlet must be open before filling the tank to prevent accumulation of pressure. 6.3.6 The initial filling of a tank with water shall be done slowly and a continuous surveillance shall be maintained for the whole of the filling period. 6.3.7 Visual inspection to be performed on the tank perimeter by the Contractors QC Inspector(s) & Reliance Engineers during initial filling and at specific intervals during the filling of the tank. 6.3.8 Level surveys shall be performed at the periphery of the tank for settlement at regular intervals before water filling, then at quarter, half full, three quarter full and full and after emptying. The shell elevation measurement shall be made at equally spaced intervals around the tank circumference not exceeding 10m (32 ft.) The minimum number of such points shall be eight. Sufficient time shall be allowed to ensure even settlement during water filling. Minimum 24 hrs interval shall be given at quarter, half full and three quarter level unless otherwise specified in engineering specification. The Contractor shall establish a visible reference level point. Settlement tolerances shall be in accordance with the API code. The test water shall be held in the tank at maximum level for a minimum of one day or until the tank foundation settlement has ceased for all practical purposes unless specified otherwise. 6.3.9 Uneven settlement of the tank on its foundation shall be reported immediately and filling shall be stopped at any signs of excessive settlement. Form EPCMD-2-QM00-FMT-ME-140 is to be used for recording settlement at different intervals. 6.3.10 Should any leakage occur when the tank is filled with water, it shall be repaired with the water level at least 1.0 foot below the work unless specified otherwise.

EPCMD-2-QM00-JEP-ME-010 00 Confidential © Reliance. All rights reserved

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Reliance 6.4

Testing of Roof The roof of a tank designed to be gas tight shall be tested by applying internal pressure as specified in the datasheet/ drawing but, in any case, the pressure shall not exceed the weight of the roof plates. Manometer tubes shall be used for monitoring the air pressure. Approved Soap solution shall be applied to the weld joints for the detection of leaks. Alternatively, vacuum testing can be done as per clause no.-6.1 of this procedure for the testing of roof weld joints after obtaining specific approval from engineering.

6.5

Post Hydrostatic Test

6.5.1 Roof Manhole and/or other roof fittings having as large an area as the water outlet must be open before emptying the tank. All roof blinds shall be removed before emptying the tank. 6.5.2 After the tank has been emptied, all blinds/spades shall be removed and permanent gaskets, bolts and piping work connected to the tank shall be reinstalled as per drawings. 6.5.3 Hydrotest water may be reused by transferring it to other tank as required and when practical. Discharges of test water, if not being reused shall be controlled as per the direction of Reliance Construction Manager.

6.6

Safety Precautions

6.6.1 Roof manholes shall be open while filling or emptying the fixed roof tank(s) for test purposes to avoid damage by excessive vacuum or pressure loading. 6.6.1 Warning signs clearly mentioning that ―Tank testing under progress‖ shall be displayed.

6.7

Record Records are to be maintained in the following formats and to be retained for the period as mentioned in the contract. EPCMD-2-QM00-FMT-ME-046

Vacuum Box Testing Record.

EPCMD-2-QM00-FMT-ME-069

Reinforcement PAD Pressure Test Record

EPCMD-2-QM00-FMT-ME-140

Inspection Report for Water Filling and Foundation Settlement of Tank

2

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