MAPLE SIRUP PRODUCERS MANUAL 



VACUUM SYSTEMS 



35 



The most recent development in collecting 

 sap has been the use of vacuum to increase 

 taphole flow and facilitate sap transportation in 

 plastic tubing and pipeline systems (7, 1,7, 105). 

 To utilize vacuum, an unvented or closed tub- 

 ing system must be used. The vacuum may be 

 created by the flow^ of the sap through the 

 tubing due to gravity (natural vacuum) or by 

 the use of a pump (pumped vacuum). The best 

 vacuum system will depend on the individual 

 characteristics of terrain and tree stand for 

 each sugar bush. Where an adequate natural 

 slope exists, natural vacuum can produce siza- 

 ble increases in the yield of sap. The details of 

 installing such a system are described by Mor- 

 row (73). Gains in sap production are generally 

 directly proportional to the amount of vacuum 

 in the system, whether produced by natural 

 flow or by a pump. As there are many areas in 

 the North American maple belt where the slope 



of the land is not sufficient for an effective 

 natural vacuum, artificial vacuum systems 

 have been developed. Several agencies have 

 done research on pumping systems (19, 106). A 

 review of the different types of units that can 

 be assembled was presented at the Eighth 

 Conference on Maple Products (UU). 



It has been well substantiated that vacuum 

 markedly increases sap yield. However, the re- 

 ports on the use of vacuum emphasize the 

 relative complexity of the equipment systems. 

 Those wishing to incorporate vacuum, either 

 natural or pumped, into their sap collection 

 should obtain assistance from someone thor- 

 oughly experienced with these systems. County 

 agricultural agents in the maple sirup-produc- 

 ing areas can recommend sources of expert 

 advice on using vacuum and on installing the 

 equipment needed in a sap-collection system. 



STORAGE TANKS 



Storage tanks serve the dual purpose of pro- 

 viding supplies of sap to the evaporator and of 

 storing sap until it can be processed or hauled 

 to an evaporator plant. Tanks supplying either 

 a farm evaporator or a central evaporator plant 

 must hold enough sap for at least 2 days' 

 operation. Tanks used as pickup stations must 

 be large enough to hold the maximum daily sap 

 production of the sugar grove or of the area 

 they serve. Pickup tanks used to haul sap from 

 the sugar grove or to deliver sap to the evapo- 

 rator house must be as large as possible to 

 reduce the cost of haulage. 



Wherever possible, locate the tanks so that 

 they can be filled and emptied by gravity (figs. 

 64 and 65). When this is not possible, motorized 

 pumps (electric or gas engine) can be used. 



The tanks should be located in a cool place 

 (fig. 66) and not inside the warm evaporator 

 house, since warm sap favors microbial gi'owth. 

 The tanks should be covered to keep out foreign 

 material, and the cover should be clear plastic 

 or some other transparent material that will 

 transmit the short ultraviolet rays of daylight 

 (100). This type of installation is especially 

 suited for roadside storage. 



If abovegTound tanks are not emptied fre- 

 quently, they should be insulated to prevent 

 the stored sap from freezing. Underground 

 tanks with opaque covers, although less likely 

 to freeze, are difficult to irradiate with ultravi- 

 olet light (fig. 67). When the covers of under- 

 ground tanks are not transparent to the ultra- 

 violet irradiation, germicidal lamps must be 

 installed at the top of the tanks to illuminate 

 the entire surface of the sap. Underground 

 tanks will usually keep the sap at a more even 

 (and perhaps at a slightly lower) temperature 

 than will aboveground tanks. But since many 

 of the bacteria that infect sap gi-ow well at low 

 temperatures, underground storage will not 

 prevent microbial fermentation and spoilage of 

 sap. Even lowering the temperature of the sap 

 by adding ice will not prevent this. 



Large storage tanks such as those at the 

 evaporator house should also be provided with 

 germicidal, ultraviolet lamps to prevent micro- 

 bial gi-ovd,h. These lamps should be mounted at 

 the top of the tanks above the liquid level and 

 arranged so that they will illuminate as much 

 of the surface of sap as jwssible. Directions for 

 making an inexpensive ultraviolet-irradiation 



