RETORT-BENCH APPURTENANCES
261
the intake of air. A flange is provided at the valve-rod giand which gives sufficient room for the valve to be withdrawn when re-facing is necessary.
The same principleof interposing a liquor seal is made us'e of in. Cort’s anti-dip (Fig. 176), but in. this case a double dip pipe is employed, the.outer pipe beingin the nature of a sliding sleeve. When the retort doors are closed the sleeve is drawii upwards to its füllest extent, so that the gas passes direct from, the inner pipe to the foul main. When the doors are opened the sleeve, by means of suitable gear, is dropped, and forms a liquor seal which precludes the possibility of air going forward.
Helps’ anti-dip (Fig. 177) employs no mechanically operated appliance ; hence one of the chief difficulties with dry mains is avoided. Attached to the back of the hydraulic main,
and running the whole length of the main, is a displacement ch.am.ber, Communi-cation is effected between. the hydraulic and displacement chamber by means of the small pipes, as shown, whilst a three-way valve has two of its ports connected to the two connect-ing pipes respectively, and the third to a supply of gas under pressure, taken back (say) from the mains leaving the purifiers. The displacement chamber, by a turn of the three-way valve, is accordingly put in connection with the vacuum exerted on the hydraulic by the exhauster or with the pressure in the mains beyond the purifiers. The level of liquor in the hydraulic is set so as to give a clear passage through the dip pipe; and, when the retort doors are shut,the displacement chamber is under a similar vacuum to that prevailing
Sliding Sleeve
Fig. 176.—Cort’s Anti-dip.
Fig. 177.—Helps’ Anti-dip.