required by DoT Safety Regulation 178.3456(b) shall be provided when frameless type tank
construction is used in which the tank constitutes in whole or in part the structural member in
lieu of a frame.
3.17 Type I tank body and equipment. In addition to the requirements of 3.16 through
3.16.13, type I semitrailer shall be furnished with the additional equipment specified in 3.17.1
3.17.1 Sump and bottom cleanout. A 6-inch minimum diameter sump with a bolted flange
closure plate shall be provided at the bottom rear of the tank.
3.17.2 Dip pipe. A pipe of type 316L stainless steel extending from within the 6-inch sump
to the outside of the tank at the top rear, within the rear flashing box, shall be provided. The pipe
shall be flanged to the top of the tank and shall be not less than 3 inches in nominal diameter.
* 3.17.3 Outlet valves and piping. The top of the dip pipe shall be provided with a 3-inch
nominal diameter discharge valve with the valve control readily accessible from the rear
platform. Automatic means of remote closure conforming to DoT Safety Regulation 178.345-9
shall be included. Piping of type 316L stainless steel not less than 3 inches in nominal
diameter shall extend down from the valve to a convenient working height from the ground at the
rear and shall terminate with a second 3-inch valve and a blank, bolted flange, complete with
3.17.4 Air inlet assembly. An air inlet assembly shall be provided at the rear manhole for
discharging the payload using the self-contained air pressure system (see 3.17.5). The air inlet
line shall be at least a one inch diameter pipe. The pipe at the air compressor unit shall be
provided with an air pressure gage visible to the operating personnel. The pipe leading from the
compressor shall be provided with a 35 psig pressure relief valve, a check valve, a tee with a
drain line to the ground ending with a drain cock, and terminate with an air inlet fitting. A
rubber hose of sufficient diameter and length with couplings (Dickson-Boss type or equivalent),
shall be furnished for installation between compressor line and tank line.
3.17.5 Pressure system. A self-contained pressure system for unloading the tank shall be
furnished. The system shall include a diesel engine driven air compressor with a capacity of not
less than 100 cubic feet per minute (cfm). The compressor shall be a two stage air cooled type.
The air compressor shall be mounted in conjunction with the engine (see 22.214.171.124), with mounts
of the type that shall minimize transfer of the compressor engine vibration to the semitrailer.
The compressor engine unit shall be provided with a suitable platform and housing. Sufficient
access for personnel to operate and maintain the unit shall be provided within the housing area.