Specifications include, but are not limited to: 104.1 Tank emptying, hydrostatic testing, and subsequent draining, cleaning, and preparation for inspection: 104.1.1 Prior to Seller beginning this work item, the City's plant operations will, at minimum, prepare the tank for the contracted service by draining the tank to approximately 99% empty, or about 500 pounds of liquid chlorine remaining in the tank.; 104.1.2 Seller shall be responsible for disconnecting the piping to the tank at the hammer unions on the pipes feeding to and from the angle valves, and plugging, capping, or blind flanging all connections to prevent entry of moisture into any of the pipes or fittings.; 104.1.3 Seller shall pull a vacuum on the tank if needed and remove all remaining liquid and gaseous chlorine from the tank. Seller shall purge the tank of all chlorine liquid and gas by continuously filling the tank with plant supplied potable water, with a temporary overflow system, and with the vapor extracted from filling the tank being sparged into sodium hydroxide solution. Any excess chlorination of the water shall be neutralized as needed to result in a pH between 6.0 and 9.0. Interruption of the fill process shall not be permitted as this can cause localized corrosion of the tank interior. Seller shall be responsible for providing all equipment and chemicals necessary to construct the waste gas sparging and removal system.; 104.1.4 Once the tank is full, the pressure relieve valve shall be removed and the opening shall be sealed with a blind flange.; 104.1.5 Seller shall then conduct hydrostatic testing by applying pressure of up to 1½ times the design maximum allowable working pressure (MAWP) of the tank and monitoring the pressure with a calibrated pressure gauge for any pressure drop that would indicate tank weakness or leaks. The pressure gauge shall be, at minimum, four inch (4") nominal dial size, liquid filled, with accuracy of 1% of full span. Seller shall be responsible for locating all leaks. All leaks shall be located and sealed, and the hydrostatic pressure test continued until a determination is made on the certifiability of the tank. Certifiability shall be established from the tank's ability to maintain pressure for thirty (30) minutes with a pressure drop of 1.0 % or less being indicated on the gauge. Written and signed documentation by the inspector of the successfully sustained pressure reading and recordable pressure drop after 30 minutes shall constitute certification. The excess pressure shall then be relieved.; 104.2 Tank inspection: 104.2.1 Seller shall have the interior and exterior of the tank inspected by a certified pressure vessel inspector for pits, cracks, and/or corrosion, and provide documentation of inspection results.; 104.2.2 A qualified pressure vessel inspector shall measure the shell thickness at designated test point locations utilizing a calibrated ultrasonic thickness measurement device. The inspector shall establish a test point location grid based on the minimum design criteria described in this section. The inspector shall record the thickness readings on a form that shows a representative diagram of the grid design, the test point numbering system used, and which can be used for future reference to ensure periodic thickness testing at the same test point locations. The test grid minimum design criteria are as follows: A. The spacing and number of test points shall be sufficient to reveal any substantive difference, or pattern of change, in shell thickness from corrosive etching as a function of chlorine liquid surface level and/or fluctuations of liquid levels within the tank.; B. There shall be more test points along any given circumference circle, formed from a vertical plane intersecting the tank's cylindrical section, than the number of tests along any given horizontal plane running parallel to the cylindrical axis for the horizontal length of the tank. The number of test points along circumference circles shall be the same for all circles; and the number of test points along any horizontal plane intersecting the shell shall be the same along all horizontal planar intersections.; C. At a minimum, the test points on each circumference circle on the tank shall be spaced every six inches (6") vertically, corresponding to incremental liquid levels in the tank, and shall be evenly spaced horizontally, as further described below: a. Each tank at the A.B. Jewell WTP has a six-foot (6') diameter and twenty (20’) foot length, exclusive of the hemispherical end caps. Testing shall be at liquid level increments of six inches (6") on four (4) circumference circles spaced every five feet (5') symmetrically between the tank ends, and along one vertical plane intersecting the center of each tank end: (4 circles x 12 x 2 points/circle) + (12 x 2 end lines) = 120 total test points.; b. Each tank at the Mohawk WTP has a seven-foot (7') diameter and sixteen-foot (16') length, exclusive of the elliptical end caps. Testing shall be at liquid level increments of six inches (6") on three (3) circumference circles spaced every five feet (5') symmetrically between the tank ends, and along one vertical plane intersecting the center of each tank end: (3 circles x 14 x 2 points/circle) + (14 x 2 end lines) = 112 total test points; 104.3 Removal and replacement of valves: 104.3.1 Seller shall remove and replace all angle valves, the pressure safety relief valve, the two (2) gas and two (2) liquid excess flow valves at AB Jewell, the three (3) gas and one (1) liquid excess flow valves at Mohawk, and all gaskets. The City of Tulsa will provide the following replacement valves and gaskets for the Seller to install at each plant: A. 4 – Angle Valves (Midland Part # A-713-ML); B. 1 - Safety Relief Valve (Midland Part # A-14227-ML for the A.B. Jewell plant, and Crosby Part # 1-1/2 JQ-225 for the Mohawk plant); C. 2 – Liquid Excess Flow Valves (Midland Part # A-129); D. 2 or 4 – Vapor Excess Flow Valves (Midland Part #`A-128); E. 5 – Valve Gaskets (Midland Part # 17-20-GY); 104.4 Dry gas purging, dew point testing, pressurizing, and leak detection, return to service: 104.4.1 The interior of the tank shall be thoroughly wiped dry by hand with absorbent lint-free cloth and all debris removed to provide a completely clean and dry tank interior.; 104.4.2 Prior to replacing the manway assembly, Seller shall remove any remaining visible moisture from the inside tank walls by purging the tank with dry, heated air.; 104.4.3 The rebuilt and complete manway assembly shall be fitted on the tank, and the bolts tightened to four hundred fifty (450) ft-lbs of torque.; 104.4.4 The tank shall be pressurized with a dry gas purge to bring the tank interior to a thoroughly dry condition. The drying process for the tank, valves, and appurtenances shall follow a procedure that yields the same results as those from the recommendations of Section 8.3.5 of Chlorine Institute Pamphlet 5 Bulk Storage of Liquid Chlorine, Edition 8, June 2011, and ensure no moisture remains in any tank parts, valves or fittings subject to chlorine exposure when the entire system is returned to service.; 104.4.5 Seller shall conduct a dew point test to ensure dryness. The test shall achieve a dew point of minus forty (-40) degrees Fahrenheit or lower. Testing and recording is to be performed at 100, 75, 50, and 25 psi. Testing shall be fully documented, including proof of calibration of testing equipment, and approved by Water Supply Manager before proceeding. Seller shall then reconnect all piping to the system. ; 104.5 Corrosion repair and touch-up painting: Note: Tank inspection may reveal that work described in this section should be performed before some or all the work described in the previous section or other previous sections.; 104.5.1 Each tank was sandblasted and repainted in the fall-winter of 2011-2012. Prospective bidders will have the opportunity to inspect the tanks' and manway exterior surfaces during a site visit at the time of the mandatory pre-bid conference. Bidders shall propose remediation work, e.g., sandblasting and painting as needed.; 104.5.2 The exterior of each tank and adjoining pipe shall be inspected for corrosion, rust and failed paint areas. Areas found to be deficient shall be sandblasted to SP-10, inspected for flaws, and painted with paint system specified herein and in strict accordance with manufacturer's instructions. Existing paint on tanks and pipe is lead-free. Exterior paint system shall be AMERCOAT® 68HS 1 coat (2.5 mil min DFT), AMERCOAT® 383HS 1 coat (4.0 mil min DFT), and AMERCOAT® 450HS 1 coat (2.0 mil min DFT), or equal. Paint system shall be approved by Water Supply Manager. Paint shall be supplied by Seller. Existing placards, labels, or data nameplates permanently attached to the tank shall be protected during painting.; 104.5.3 The discovery of any area(s) on any interior tank surface, or manway surface or manway flange or flange surface that is concealed while the tank is in service during the pre-bid site visit, and which is subsequently determined to need repairs involving machining and/or welding, or replacement at substantial additional cost to Seller and not explicitly provided for in bid price, shall be promptly brought to Water Supply Manager's attention. A repair plan, outside of this contract, will then be arranged with Seller. All service repairs shall be clearly documented as part of this contract.; 104.5.4 Any work that produces sparks or can otherwise be a source of ignition is considered hot work requiring a Hot Work Permit. The Seller shall notify the Superintendent about the need for a Hot Work Permit. Hot Work Permits shall be provided by the Seller and shall meet the minimum requirements outlined in OSHA 1910.252 and the City of Tulsa Safety and Health Manual, Section 302.
