这是api 650-2009附录h的内容，请参考： h.4.6 roof supports h.4.6.1 the floating roof shall be provided with adjustable supports, unless the purchaser specifies fixed supports. h.4.6.2 unless specified otherwise, the height of the floating roof shall be adjustable to two positions with the tank in service. the design of the supports shall prevent damage to the fixed roof and floating roof when the tank is in an overflow condition. h.4.6.3 the purchaser shall specify clearance requirements to establish the low (operating) and high (maintenance) levels of the roof supports. the low roof position shall be the lowest permitted by the internal components of the tank including shell nozzles with internal projections. if specified, a single position support height shall be based on the purchaser-specified clearance dimension. the purchaser shall provide data to enable the manufacturer to ensure that all tank appurtenances (such as mixers, interior piping, and fill nozzles) are cleared by the roof in its lowest position. in addition to fitting elevations, such data shall include minimum mixer operation level and low level alarm settings (if applicable). if not specified otherwise by the purchaser, the following apply: h.4.6.3.1 the high roof position shall provide a 2-m (78-in.) minimum clearance throughout the bottom, between the roof and the tank bottom. h.4.6.3.2 where propeller-type mixers are used, the support legs shall provide a minimum clearance of 75 mm (3 in.) from the underside of the internal floating roof (or roof notch) to the tip of the mixer propeller. h.4.6.4 support attachments in the deck area shall be designed to prevent failure at the point of attachment. on the bottom of the steel welded deck plates (used on types h.2.2a, b, c, d, and g), where flexure is anticipated adjacent to supports or other relatively rigid members, full-fillet welds not less than 50 mm (2 in.) long on 250 mm (10 in.) centers shall be used on any plate laps that occur within 300 mm (12 in.) of any such support or member. h.4.6.5 supports shall be fabricated from pipe, unless cable or another type is specified on the data sheet, line 34 and approved by the purchaser. supports fabricated from pipe shall be notched or otherwise constructed at the bottom to provide complete liquid drainage. cable supports shall be adjustable externally and shall not have an open penetration at the floating roof surface. fixed roofs shall be designed or verified suitable for cable support loads, when used, per agreement between the purchaser and tank/roof manufacturers. h.4.6.6 steel pads or other means shall be used to distribute the loads on the bottom of the tank and provide a wear surface. with the purchaser’s approval, pads may be omitted if the tank bottom will support the live load plus the dead load of the floating roof. if pads are used, they shall be continuously welded to the tank bottom. h.4.6.7 aluminum supports shall be isolated from carbon steel by an austenitic stainless steel spacer, an elastomeric bearing pad, or equivalent protection, unless specified otherwise by the purchaser. h.4.6.8 special protective measures (corrosion allowance, material selection, coatings) are to be evaluated for supports that interface with stratified product bottoms, which may include corrosive contaminant combinations not found in the normal product. the purchaser shall specify if any protective measures are required. h.4.6.9 for tanks with internal coatings, the purchaser shall specify on line 23 of the data sheet any special requirements for minimizing corrosion where the leg contacts the tank bottom, such as a flat plate or bull nose on the leg base, a thicker base plate, or other means. h.4.6.10 consideration shall be given to the use of fixed supports for the operating position (low level) of internal floating roofs, which utilize cable supports suspended from a fixed roof. these supports are typically not adjustable, are sealed to prevent emissions, and are for the operating position (low level) set at a level as specified by the purchaser. the use of fixed supports for the low level position are intended to reduce the frequency of fixed roof loading. the operating position (low level) and length of the cables shall be such that sinking and/or collapse of the internal floating roof will not apply loads to the support cables. h.4.6.11 if cable supports are used, the supports shall be adjustable from the fixed roof while the floating roof is floating and with the cables unloaded. h.4.6.12 cables, cable segments, or cable connections which support the floating roof are prohibited from using a fusible link or other devices which are designed to fail at a specified load limit. h.4.6.13 cables used to support internal floating roofs shall be 300 series stainless steel and shall be flexible to facilitate repeatable lay down patterns on the floating roof as it travels up and down within the tank. lay down patterns shall be positioned to avoid rim seals and floating roof appurtenances that could prevent the cable from freely extending as the floating roof lowers.
