Wednesday, October 07, 2009

Hydrostatic Test of Piping

1. General
i. This document present the Hydrostatic testing procedure for carbon steel & Alloy steel piping that shall be applied of piping installation system
ii. This document describes minimum requirements of the Hydrostatic testing such as: scope, safety, method, etc.
iii. Any deviation from this procedure requires written approval from CUSTOMER.

1.1. Scope
i. The following items are not included of this procedure:
a) Any package unit previously tested by manufacturer.
b) Plumbing systems
c) Pipe lines and systems opened to the atmosphere
d) Instrument piping between the root valve at the process or utility line and the connected instrument and control piping used to connect air or control apparatus.

ii. The following items are not included on Hydrostatic Test:
a) Pumps, compressors and turbines.
b) Equipment and Supplier furnished piping that specifically recommended by Manufacturer not to be tested.
c) Vessels or equipments supported by structure or foundation, that not capable to support hydrostatic test load.
d) Vessels or equipment having internals or linings that can be damages by test liquid.
e) Vessels or equipment included in the pressure test shall not be greater than shop test pressure for equipment as stated on the vessel drawing, Vendor’s equipment drawing, or data sheets. If the piping test pressure is greater than the vessel or equipment test pressure, the piping shall be disconnected, blinded, and tested separately. If the piping cannot be disconnected (welded connection), One of the following shall be performed:
- CONTRACTOR shall request written approval from the Vendor to test at required piping test pressure.
- Reduce piping test pressure as necessary after discussing with CUSTOMER.
f) Certain types of exchangers are specifically designed for a low allowable differential pressure between shell and tubes, as stated on the Vendor drawings and data sheets. These should be checked.
g) Pressure vessels with two or more pressure chamber are specifically designed for a low allowable differential pressure between pressure chambers as stated on Vendor drawings. These should be checked.
h) Instruments and utility piping systems shall be protected from damage when hydrostatic test is going.
i) Instrumentation equipment shall not be hydrostatic tested during pipe testing. This includes relief valves, orifices plates, flow nozzles, displacement and turbine meters, level gauge, transmitters, self contain pressure regulators, pressure gauges, etc.

1.2. References
i. Customer specification
- Piping Specification

ii. Contractor procedures
- Project Quality Assurance Plan
- QA/QC Procedure
- Inspection and Test Plan
- Construction Procedure
- Field testing Procedure
- NDE Procedure
- Welding Procedure

iii. Codes and Standards

1.3. Conflicting requirements

In case of conflict between this procedure and its associated specification and the above codes and standards, the CONTRACTOR shall bring the matter to CUSTOMER attention for resolution and approved in writing.
Should conflicts exist between this procedure and other documents, the following order of precedence shall govern:
- Scope of work
- Data sheets
- Other CUSTOMER specification
- Other Referenced Publications
- Approved Construction drawings

2. Responsibility
2.1. Project Quality Control Manager
Project Quality Control Manager is responsible for assuring that the Hydrostatic test activities are conformed to the procedure, specification and code/ standards.
2.2. QC Engineer
QC Engineer is responsible for publish this procedures and required documents of it.
2.3. Examiner
The examiner is responsible for controlling the Hydrostatic test activities, witnesses all of inspection and test activities, and recorded.

3. Requirements
3.1. General
i. After completion of construction or pipe has been replace and relocated, each piping system necessary to perform hydrostatic test. It is aimed to demonstrate that the piping system has the strength required, to meet the design conditions, and to verify that the piping system is leak free.
ii. CONTRACTOR shall prepare test package.
iii. The testing shall be in according with Test Package.
iv. Isolation of Equipment and piping not subjected to pressure test.
Equipment that is not to be subjected to pressure test shall be either disconnected from the piping system or isolated by blanks or similar means.
Valves may be used for this purpose provided that valve closure is suitable for the proposed test pressure. CUSTOMER shall be aware of the limitations of pressure and temperature for each valve subject to test condition.
Isolated equipment and piping must be vented.
v. All drains, vents, sample point shall be isolated or plugged prior to hydrostatic test.
vi. In case of the piping system is painted or insulated, the pipe joints that will be leak tested shall be un-painted or un-insulated or covered formerly until the examination had been successfully completed.
vii. All of defects detected during hydrostatic testing shall be repaired in accordance with Project specification. After the defect repaired, the hydrostatic test shall be repeated.
viii. If only minor repairs or modifications take place, the test shall not be repeated. It only requires some examination to ensure the repairs or modifications accepted; such as: radiographic examination, liquid penetrant examination, etc, with refers to CUSTOMER approval.
ix. A flanged joint at which blanks are inserted to blank off other equipment during the test need not be tested after removal of the blank.
x. Piping which is opened to atmosphere and does not potentially have back pressure; such as: drains, vents, outlet of safety valves, etc. are not required to be hydrostatic tested, but must be 100% visually inspected.
xi. All pressure gauges and pressure recorders to be used for testing shall be calibrated.
xii. Flanged globe control valves shall not be included in the hydrostatic test systems. Where necessary temporary spools may be used in place of these control valves, or blind flanges shall be provided at the up-stream and down –stream flange of the valve and the system tested through the by pass. Welded in control valves shall have the internals removed and a blind flange fitted over the opening.
xiii. All equipment that is removed from lines during hydrostatic testing (particularly control valves) must be disconnected by qualified mechanic technicians and protected with wooden plugs or plastic caps.

3.2. Safety
i. Suitable precautions in the event of piping system rupture shall be taken to eliminate hazards to personnel in the proximity of lines being tested.
ii. All flange connection shall be checked to avoid the loose bolt that it can cause injury
iii. Warning sign and board will be displayed in the area.
iv. Only the concerned parties will be allowed to entry the test area, to prevent unwanted person to entry the area, a watchman together with a safety man will be guard during testing.
v. If the location of testing close to other activities, barricade area with rope shall be applied.
vi. No body standing behind end of pipe that being tested.
vii. Check the thickness of temporary blind, flange or spool piece as per design.
viii. Put information of each valve that pipeline under hydrostatic tested for preventing unauthorized personnel operates it.
ix. The thickness of plate, which will be used for temporary blind, shall be attached on the test package.
x. During test, the pressure shall be close monitored by a man as a safety precaution.

3.3. Hydrostatic test Data
i. The maximum test pressure data for each line shall be specified in the piping line list. Additional data, as listed below, shall be provided by CONTRACTOR in accordance with project specifications.
ii. Maximum Stress during Test
a) At no time during the pressure test, the circumferential (hoop) stress of any part of the piping system shall be subjected greater than 90% of the yield strength (0,2% offset) at test temperature.
b) In addition, the sum of longitudinal stresses due to test pressure and live and dead loads at the time of test, excluding occasional loads, shall not exceed 90% of the yield strength at test temperature.

3.4. Hydrostatic test Blind
i) Plain test blanks with 1/16 inch flat non-asbestos gaskets shall be used for blanking flat face, raised face, ring joint, male and female, and tongue and groove type flanges. However, where permanent operational blinds are installed, they may be used for field pressure testing. Only approved manufacturers blinds may be used. No field fabricated blinds may be used as blind flange.
ii) All temporary blanks, or spectacle blinds, used for isolation during hydrostatic test shall meet required thickness as designated. Gasket material shall be used on both sides of isolation blank plate.

3.5. Test Water Criteria
i) Water shall normally used as the test medium unless otherwise specified by the CUSTOMER. Test water shall be clean and shall be of such quality as to minimize corrosion of the materials in the piping system.
Test water shall avoid foreign matter such as: sand, rust, or other particles in to the pipe line.
ii) The use of sea water is prohibited.
iii) Water for austenitic stainless steel, such as: piping, vessels, and equipment including those with stainless steel cladding, linins, or internals shall use suitable purposes.
iv) Piping, vessels and equipment must be drained thoroughly after testing. If complete draining is impossible, the system shall be flushed free from all test water using boiler condensate or de-mineralized water.
v) It should be noted that risk of pitting corrosion is considerably diminished if the time between pressure testing and start up is as short as possible. If the time is longer, flushing with condensate or de-mineralized water is recommended.
It also applies to medium and high nickel alloys and ferritic chromium stainless steel where pitting corrosion is a risk.

3.6. Temperature of Test Medium
i) Temperature of test medium shall be that of the available source unless otherwise specified by the CUSTOMER. The test pressure shall not be applied until the system and the pressurizing medium are approximately at the same temperature. When conducting pressure test at low metal temperature, the possibility of brittle fracture shall be considered.
ii) Minimum Metal Temperature
At time of testing, the minimum pipe metal temperature shall refer to code and standard.

3.7. Hydrostatic Test Schedule
Pressure testing shall be performed following the completion of Post weld heat treatment and NDE refer to “ITP at shop” or “ITP at Field”, and other fabrication, assembly and erection activities required to provide the system or portion thereof subjected to the pressure test with pressure retaining capability.

4. Hydrostatic Test Method

1 comment:

  1. thx buddy, i've been lookin for this.


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