Howden Roots Metric Series, Installation, Operation And Maintenance Manual

ISRB_2002 GEA 19171 Roots URAI 

Page 8 of 32

Technical Supplement for URAI-G Gas Blowers 

Technical Supplement for 32, 33, 36, 42, 45, 47, 53, 

56, 59, 65, 68, 615 Universal RAI-G blowers 

Precaution: URAI-G blowers: Care must be used when 

opening the head plate seal vent chamber plugs (43) as 

some gas will escape–if it is a pressure system, or the 

atmospheric air will leak into the blower if the system is 

under vacuum. There is a possibility of some gas 

leakage through the mechanical seals. This leakage on 

the gear end will escape through the gear box vent, and 

on the drive end, through the grease release fittings. If 

the gas leakage is undesirable, each seal chamber must 

be purged with an inert gas through one purge gas hole 

(43) per seal. There are two plugged purge gas holes 

(1/8 NPT) provided per seal. The purge gas pressure 

must be maintained one PSI above the discharge gas 

pressure. Also, there exists a possibility of gear end oil 

and drive end grease leakage into the gas stream. 
Roots Universal RAI-G rotary positive gas blowers are a 

design extension of the basic Roots Universal RAI 

blower model. URAIG blower uses (4) mechanical seals 

in place of the standard inboard lip seals to minimize 

gas leakage into the atmosphere. 
These units are intended for gases which are compatible 

with cast iron case material, steel shafts, 300/400 series 

stainless steel and carbon seal components, viton o-

rings and the oil/ grease lubricants. If there are any 

questions regarding application or operation of this gas 

blower, please contact factory. 
A simple but very effective lubrication system is 

employed on the drive shaft end bearings. Hydraulic 

pressure relief fittings are provided to vent any excess 

grease, preventing pressure build-up on the seals. A 

restriction plug and metering orifice prevent loss of 

lubricant from initial surges in lubricant pressure but 

permit venting excess lubricant under steadily rising 

pressures. 
Using a pressure gun, slowly force new lubricant into 

each drive end bearing housing until traces of clean 

grease comes out of the relief fitting. The use of an 

electric or pneumatic grease gun could force the grease 

in too rapidly and thus invert the seals and should not be 

used. 
Gear end bearings, gears and oil seals are lubricated by 

the action of the timing gears which dip into the main oil 

sumps causing oil to splash directly on gears and into 

bearings and seals. A drain port is provided below each 

bearing to prevent an excessive amount of oil in the 

bearings. Seals located inboard of the bearings in each 

headplate effectively retain oil within the sumps. Any 

small weepage that may occur should the seals wear 

passes into a cavity in each vented headplate and is 

drained downward. 
Proper lubrication is usually the most important single 

consideration in obtaining maximum service life and 

satisfactory operation from the unit. Unless operating 

conditions are severe, a weekly check of oil level and 

necessary addition of lubricant should be sufficient. 
During the first week of operation, check the oil levels in 

the oil sumps about once a day, and watch for leaks. 

Replenish as necessary. Thereafter, an occasional 

check should be sufficient. 
More frequent oil service may be necessary if the blower 

is operated in a very dusty location.

Lubrication 

Due to sludge build-up and seal leakage problems, 

Howden Roots recommendation is DO NOT USE 

Mobil SHC synthetic oils in Roots blowers. 
Proper lubrication is usually the most important 

single consideration in obtaining maximum service 

life and satisfactory operation from the unit. 
URAI Air and Gas gear end bearing lubrication/oil 

with splash lubrication on the gear end only (Drive 

end grease lubricated). 



  The specified and recommended oil is Roots Synthetic 

Oil of correct viscosity per Table 2, page 16. 



  To fill the gearbox, remove the breather plug (25) and 

the oil overflow plug (21) - see page 15. Fill the reservoir 

up to the overflow hole. 

DO NOT OVERFILL

. Place the  

breather and the overflow plug back into their respective 

holes. 



  The lubrication should be changed after initial 100 hours 

of operation. 



  Proper service intervals of the oil thereafter are based 

on the discharge air temperature of the blower. Please 

refer to the information below to “How to properly 

determine the oil service intervals” shown on this page. 



  Unless operating conditions are quite severe, a weekly 

check of the oil level and necessary addition of lubricant 

should be sufficient. During the first week of operation, 

check the oil levels in the oil sumps about once a day, 

and watch for leaks. Replenish as necessary. 



  If you choose to use another oil other than the specified 

and recommended ROOTS Synthetic, use a good grade 

of industrial type non-detergent, rust inhibiting, anti-

foaming oil and of correct viscosity per Table 2, page 16. 

ISRB_2002 GEA 19171 Roots URAI.indd   8

17/09/2015   12:52