Kohler Generator Sets 20--2800 kW User Manual download pdf (Page 21)

TP-5700 7/93 9Section 3 Location

The composition of the mounting pad should follow

standard practice for the required loading. Common

specifications call for 2500-3000 psi (176-211 kg/cm

)

concrete reinforced with eight-gauge wire mesh or

number 6 reinforcing bars on 12-inch (30-cm) centers.

The total weight of the mounting pad should be at least

equal to the weight of the generator set (a density of 150

lbs. per cubic foot [68.4 kg per 0.03 m

] for concrete can

be used for this calculation). Suggested concrete

mixture by volume is 1:2:3 parts of cement, sand, and

aggregate. A layer of 8-10 inches (21-26 cm) of sand or

gravel should surround the pad for proper support and

isolation of a pad located at or below grade. All

generator sets should be anchored to concrete with

bolts buried in the surface of the pad. Expansion-type

anchors are not acceptable.

Note: Always refer to the dimensional drawings for the

generator and accessories when considering

placement of conduits and fuel lines. Dimensions

are provided on these drawings for rough-ins and

stub-ups of electrical and fuel connections.

3.4 Vibration Isolation

Mounting bases for generator sets 30kW and larger are

typically made from “I” or “C” section fabricated steel

with a width of 2-3 inches per channel. Length varies

with the size of the unit, resulting in a static load on the

mounting base of 10-25 psi (0.703--1.758 kg/cm

)ifthe

total bottom surface of the channel is in contact with the

mounting base. All generator sets should have vibration

isolation between the engine-generator and skid or

mounting base. See Figure 3-5. This may consist of

neoprene or combination spring and neoprene isolators

between the engine-generator and skid, or spring-type

mounts between the skid and mounting pad. An

advantage of factory-installed mounts between the

engine-generator and the skid is that engine-generator

alignment is not affected by stress induced in handling,

shipment, or mounting on an uneven surface. A less

rigid skid may be used, reducing weight and installation

time. All connections between the generator and

mounting base s uch as conduits, fuel lines, exhaust

piping, etc., must have flexible sections to prevent

breakage and isolate vibration to the generator set.

Generator sets 350 kW and larger are usually mounted

directly to a structural steel base. For these units, the

manufacturer’s recommended vibration isolators

should be installed between the base and mounting

pad. Because of the reduced mounting surface area of

these individual mounts, the static load on the mounting

surface will increase to the range of 50--100 psi

(3.515--7.03 kg/cm

The vibration isolation efficiency of neoprene pad-type

mounts is approximately 90%. When installed at or

below grade, this degree of isolation will prevent

transmission of objectionable vibration to the

surrounding structure. Spring-type isolators can be

expected to provide isolation efficiency of 98%. This

type of mount may be desirable for above-grade

installations.

In some critical applications where the generator set is

installed above grade or where earthquake-proof

mounts are specified, it may be necessary to install

spring-type vibration isolators under the generator set

mounting base. Check state and local codes for such

requirements. Accessory vibration mounts should be

installed at the locations of the standard predrilled

mounting holes.

TP-5700-3

1. To engine-generator

2. Skid cross member

3. Neoprene vibration isolator

Figure 3-5 Neoprene-Type Integral Vibration

Isolators

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 55 56

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Kohler Generator Sets 20--2800 kW User Manual Page 21

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