Mettler Toledo LJ16 Spécifications télécharger pdf (Page 57)

Chapter 5: General Installation Guidelines

Piping Design

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Piping Design

Any time that piping is connected to a tank scale (a live-to-dead connection),

there is a potential for mechanical binding. If piping is not installed properly, it

can cause weighing errors by pushing or pulling on the tank. The best way to

avoid those problems is to design piping so that it does not exert unwanted forces

on a tank. Here are some general guidelines you should follow when designing a

piping system:

• Make sure the tank’s support structure deflects as little as possible. That will

decrease the amount of deflection in the piping.

• Run all pipes horizontally from the tank so that the tank is not suspended by

the piping.

• Locate the first rigid support for the piping as far away from the tank as

possible. That will make the piping more flexible.

• Use pipe with the smallest diameter and lightest gauge possible. That will

make the piping more flexible.

• Use flexible piping or connections whenever possible.

Why is it important for piping to be flexible? Figure 5-20a shows a tank mounted

on weigh modules and supported by an I-beam. A pipe is connected to the tank

and rigidly clamped to another structure at a distance (L ) from the tank. When

the tank is empty, the pipe remains in a horizontal position and exerts no force on

the tank. When the tank is full (see Figure 5-20b), it moves downward because of

the deflection of the load cell and the I-beam. This pulls the pipe downward the

same distance that the tank deflects (∆h ). The pipe exerts an upward force on the

tank, affecting weight measurements. The more flexible the piping is, the less force

it will exert on the tank.

∆

Figure 5-20a: Empty Tank Figure 5-20b: Full Tank

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Mettler Toledo LJ16 Spécifications Page 57