function Calc_DrawDown()
{
	form = document.calc;

	DrawDownRatio	= form.DDR.value;
	DrawBalance		= form.DB.value;
	TubeOD			= parseFloat( form.OD.value );
	TubeID			= parseFloat( form.ID.value );

	if( TubeID >= TubeOD )
	{
		alert( 'Tube OD must be greater than Tube ID.' );
		return false;
	}
	if( TubeID <= 0 )
	{
		alert( 'Tube ID must be greater than 0.' );
		return false;
	}


	TipOD = Math.pow( ((( Math.pow( TubeOD, 2 ) - Math.pow( TubeID, 2 )) * DrawDownRatio ) / ((( Math.pow( DrawBalance, 2 ) * Math.pow( TubeOD, 2 )) / Math.pow( TubeID, 2 )) - 1 )), 0.5 );
	DieID = (DrawBalance * TipOD * TubeOD) / TubeID;

	TipOD	= Math.round( TipOD * 1000 ) / 1000;
	DieID	= Math.round( DieID * 1000 ) / 1000;

	form.TipOD.value	= TipOD;
	form.DieID.value	= DieID;

	return false;
}

function Calc_PPH()
{
	form = document.calc2;

	FPM				= form.FPM.value;
	Density			= form.Density.value;
//	Area			= form.Area.value;
	TubeOD			= form.OD.value;
	TubeID			= form.ID.value;

	Area	= ( 3.1415927 / 4 ) * ( Math.pow( TubeOD, 2 ) - Math.pow( TubeID, 2 ));
	PPH = (Density) * (60) * (Area) * (12) * FPM;

	PPH	= Math.round( PPH * 1000 ) / 1000;

	form.PPH.value	= PPH;
		
	return false;

}

function Calc_FPM()
{
	form = document.calc3;

	PPH				= form.PPH.value;
	Density			= form.Density.value;
	TubeOD			= form.OD.value;
	TubeID			= form.ID.value;

	Area	= ( 3.1415927 / 4 ) * ( Math.pow( TubeOD, 2 ) - Math.pow( TubeID, 2 ));
	FPM		= ( 1 / Density ) * ( 1 / 60 ) * ( 1 / Area ) * ( 1 / 12 ) * PPH;

	FPM	= Math.round( FPM * 1000 ) / 1000;

	form.FPM.value	= FPM;

	return false;

}