Check Valves; Temperature Rise - Grundfos CR Series Installation And Operation Manual

Check valves

A check valve may be required on the discharge side of the pump to prevent the pump's inlet pressure from being exceeded. For example, if a pump with
no check valve is stopped because there is no demand on the system (all valves are closed), the high system pressure on the
discharge side of the pump will "find" its way back to the inlet of the pump. If the system pressure is greater than the pump's maximum inlet
pressure rating, the limits of the pump will be exceeded and a check valve needs to be fitted on the discharge side of the pump to prevent this
condition. This is especially critical for CRN-SF applications because of the very high discharge pressures involved. As a result, most CRN-SF installations
require a check valve on the discharge piping.
Bypass
A bypass should be installed in the discharge pipe if there is any possibility the pump may operate against a closed valve in the discharge line. Flow
through the pump is required to ensure adequate cooling and lubrication of the pump is maintained. See Table A for minimum flow rates. Elbows
should be a minimum of 12" from the orifice discharge to prevent erosion.

Temperature rise

It may sometimes be necessary to stop the flow through a pump during operation. At
shut-off, the power to the pump is transferred to the pumped liquid as head, causing a
temperature rise in the liquid. The result is risk of excess heating of and consequent
damage to the pump. The risk depends on the temperature of the pumped liquid and
for how long the pump is operating without flow. (See temperature rise chart.)
Conditions/Reservations
The listed times are subject to the following conditions/reservations:
• No exchange of heat with the surroundings.
• The pumped liquid is water with a specific heat of 1.0
• Pump parts (chambers, impellers and shaft) have the same thermal capacity as water.
• The water in the base and the pump head is not included.
These reservations should give sufficient safety margin against excessive temperature rise.
The maximum temperature must not exceeed the pump maximum rating.
For Pump Ends With Bellows Seals Only (CR 2, 4, 8, 16)
Remove shaft seal protectors before installing motor (see diagram at below).
1. Remove coupling guards.
2. Remove coupling halves.
3. Remove shaft seal protectors.
4. Follow motor replacement instructions on page 10.
6
Table A
Minimum Continuous Duty Flow Rates for CR(I)(X)(N)(T)
Min. Flow in GPM at Liquid Temperature
min°F to 176°F
Pump Type min°C to 80°C
CR, CRI, CRN 1s 0.5
CR, CRI, CRN 1 0.9
CR, CRI, CRN 3 1.6
CR, CRI, CRN 5 3.0
CR, CRI, CRN 10 5.5
CR, CRI, CRN 15 9.5
CR, CRI, CRN 20 11
CR, CRN 32 14
CR, CRN 45 22
CR, CRN 64 34
CR, CRN 90 44
CRT 2 1.3
CRT 4 3.0
CR, CRX, CRN, CRT 8 4.0
CR, CRX, CRN, CRT 16 8.0
*Grundfos Cool-Top is only available in the following pump types.
Pump
CR 1s CR 1 CR 3
Type
Standard
(CR)
I Version
• • •
(CRI)
N Version
• • •
(CRN)
* CRN 8 and 16 are only available in CRN-S. A CRN-S is a CRN pump without staybolts. All rubber parts are FXM.
Btu
(4.18
lb.°F
Cool-Top™
at 210°F at 248°F at 356°F
at 99°C at 120°C at 180°C
0.7 1.2 1.2*
1.3 2.3 2.3*
2.4 4.0 4.0*
4.5 7.5 7.5*
8.3 14 14*
14 24 24*
17 28 28*
21 35 35*
33 55 55*
51 85 85*
66 110 110*
2.0 3.3 N/A
4.5 7.5 N/A
6.0 10 10*
12 20 20*
CR 5 CR 10 CR 15 CR 20 CR 32
• • • •
• • • •
Pump
Type
CR 1s, 1, 3
CR 5
CR 10
CR 15
CR 20
CR 32, 45, 64, 90
kJ
).
kg°C
CR 45 CR 64 CR 90 CR 8
• • • •
• • • • •*
Time for Temperature
Rise of 18° F (10°C)
Seconds
210
240
210
150
120
60
CR 16
•*
Minutes
3.5
4.0
3.5
2.5
2.0
1.0