#0012b, 17-Jul-2013

Technical Bulletin
Preventing Condensation When Operating a
SYNRAD Water-Cooled Laser
Description:
This Technical Bulletin describes steps you can take to prevent condensation when operating your water-cooled SYNRAD laser.
Condensation can damage electrical components as well as internal laser optics.

This Bulletin covers the following topics:• How condensation forms• Dew point temperature calculations• Coolant recommendations and guidelines• Setting chiller temperature• Steps to prevent condensation• Summary

Important Note:
It is the customer’s responsibility to eliminate any possibility of condensation damage to the laser. Condensation causes severe
laser damage that is not covered under warranty and leads to very expensive repair costs.

How condensation forms
Condensation is a concern with all water-cooled lasers and is especially dangerous when water-cooled lasers operate in hightemperature / high relative humidity environments. Condensation forms when the laser’s coolant temperature is lower than thedew point temperature of the surrounding air. This causes water vapor in the warm, moist air to condense into liquid water on
the colder surfaces of the laser, including internal / external coolant lines, electronic circuit boards, and optical components.
Condensation damage occurs when moisture condenses out of the surrounding air, causing water droplets to form inside thelaser housing. This can lead to catastrophic failure of laser electronics and/or damage to optical surfaces.

Dew point temperature calculations
To determine the dew point temperature of your operating environment, refer to Table 1 below. Note that temperatures areshown in degrees Fahrenheit; values in parenthesis are degrees Celsius. Look down at the Air Temp column on the left and locate
an air temperature that corresponds to the air temperature in the area where your laser is operating. Follow this Air Temp row
across until you reach a Relative Humidity column matching the relative humidity percentage of the laser’s environment. Thevalue at the intersection of the Air Temp row and Relative Humidity column is the Dew Point Temperature in °F (°C).

The chiller’s temperature setpoint must be set above the dew point temperature. For example, if the ambient air temperature is85 °F (29 °C) and the relative humidity is 60%, then the dew point temperature is 70 °F (21 °C). Adjust the chiller’s temperature
setpoint to 72 °F (22 °C) to prevent condensation from developing inside the laser.
Table 1 Dew Point Temperature Chart in Degrees Fahrenheit (°Celsius)
Relative Humidity (%)
Air Temp°F (°C)

202530

35

40

45

50

55

60

65

7075

80

85

909560(16)------

32(0)

36(2)

39(4)

41(5)

44(7)

46(8)

48(9)

50(10)

51(11)

54(12)55(13)57(14)

59(15)

65(18)

--

--

33(1)

37(3)

40(4)

43(6)

46(8)

48(9)

51(11)

53(12)

55(13)

57(14)

59(15)

60(16)

62(1764(18)70(21)

--

33(1)

37(3)

41(5)

45(7)

48(9)

51(11)

53(12)

56(13)

58(14)

60(16)

62(17)

64(18)

65(18)

67(19)

69(21)

75(24)

--

37(3)

42(6)

46(8)

49(9)

52(11)

55(13)

58(14)

60(16)

62(17)

65(18)

67(19)

68(20)

70(21)

72(22)

73(23)

80(27)

35(2)41(5)46(8)

50(10)

54(12)

57(14)

60(16)

62(17)

65(18)

67(19)

69(21)

71(22)

73(23)

75(24)

77(25)

78(26)

85
(29)

40
(4)

45(7)

50(10)

54(12)

58(14)

61(16)

64(18)

67(19)

70(21)

72(22)

74(23)

76(24)

78(26)

80(27)

82(28)

83
(28)

90
(32)

44(7)

50(10)

54(12)

59(15)

62(17)

66(19)

69(21)

72(22)

74(23)

77(25)

79(26)

81(27)

83(28)

85(29)

87(31)

88(31)

95
(35)

48(9)

54(12)

59(15)63(17)67(19)

70(21)

73(23)

76(24)

79(26)

81(27)

84(29)

86(30)

88(31)

90(32)

92(33)

93(34)

100(38)52(11)

58(14)

63(17)

68(20)

71(22)

75(24)

78(26)

81(27)

84(29)

86(30)

88(31)

91(33)

93(34)

95(35)

97(36)

98(37)

Coolant recommendations and guidelines
Using the proper coolant greatly increases the heat removal capacity and efficiency of your chiller. SYNRAD recommends thelaser’s cooling fluid contain at least 90% distilled water by volume. In closed-loop systems, use a corrosion inhibitor/algaecide suchas Optishield® Plus or equivalent as required. Avoid glycol-based additives because they reduce the coolant’s heat capacity andhigh concentrations may affect power stability. For SYNRAD lasers, the minimum coolant setpoint is 18 °C (64 °F) so glycol is notnecessary unless the chiller is subjected to freezing temperatures.
If tap water is used, chloride levels should not exceed a concentration of 25 parts per million (PPM) and total hardness should bebelow 100 PPM. Install a filter on the chiller’s return line and inspect frequently.
Note: DO NOT use de-ionized (DI) water as a coolant. DI water is unusually corrosive and is not recommended for mixed material
cooling systems.

Setting chiller temperature
SYNRAD water-cooled lasers are designed to operate and perform to their stated specifications at a coolant temperature between
18 °C–22 °C (64 °F–72 °F). When the dew point temperature is above the coolant temperature, condensation can occur and there
are two very important factors to consider: (1) Operating the laser at a coolant temperature lower than the dew pointtemperature will cause condensation that could shorten laser lifetime significantly. (2) Raising the coolant temperature setpoint
above the dew point temperature will help prevent condensation; however, a coolant temperature above 22 °C (72 °F) can affectlaser performance and shorten laser component lifetimes.
As a guide to adjusting your coolant temperature setpoint, consider the following example. The normal room air temperature
where your laser is operating is around 29 °C (85 °F) and the relative humidity is around 70%. From Table 1 above, thiscorresponds to a dew point temperature of 23 °C (74 °F). Remember that condensation on cooling tubes occurs when theirsurface temperature is below the dew point temperature.
In order to prevent condensation, adjust the chiller setpoint a few degrees above the dew point temperature. Do not choose anarbitrarily large number, but instead choose a setpoint value just above the dew point, like 25 °C (77 °F), and then carefully
monitor the laser (and external RF supply, if applicable) for signs of condensation during and after operation.
The chiller temperature setpoint must be set as low as practical because coolant temperature above our specified maximum
coolant temperature range of 22 °C (72 °F) will affect laser performance. Mode quality and power stability degradation is the mostnoticeable short-term effect of under-cooling the laser. Long-term, the laser may suffer a shortened lifetime due to excessive
heating of the laser’s RF circuitry. Please note that laser specifications quoted in the Operator’s Manual are valid only in thespecified coolant range of 18 °C–22 °C (64 °F–72 °F).
The best way to achieve long laser life and optimum laser performance is to air-condition the laser environment and thenmaintain a coolant temperature setpoint between 18 °C–22 °C (64 °F–72 °F).

Steps to prevent condensation
The most effective step an end-user can take to prevent condensation in a high heat / high humidity operating environment is toinstall an air-conditioning system!
In addition to lowering the ambient air temperature around the laser, an air-conditioning system will also lower relative humidity.
The cost of a robust air-conditioning system is far less than the cost of repairing a damaged laser.
Implementing one or more of the practices described below may reduce the risk of condensation enough that coolant
temperatures can be set within the recommended range of 18 °C–22 °C (64 °F–72 °F).
1. For Firestar f201/f400, i401, and p100/p250 lasers, apply 2 to 5 PSI (0.14 to 0.34 bar) of high-purity grade nitrogen,breathing grade air, or compressed clean, dry air to the Gas Purge port. See Technical Bulletin #15 for details and gas
filtering specifications.
2. Incorporate a small air-conditioner into the laser system to ventilate the laser enclosure. Air-conditioning lowers ambient
air temperature and reduces relative humidity so that the laser’s operating environment becomes independent of the enduser’s industrial environment. Consistent operating conditions lead to better laser performance and longer lifetime while
minimizing service costs.
3. Duct an existing air-conditioning vent directly over the laser housing to lower local air and dew point temperatures.
4. Install a local dehumidifier to reduce the relative humidity level in the area of the laser.
5. Increase the recommended coolant flow rate by 1.0 to 1.5 gallons per minute (3.8–5.7 liters per minute). However, do notallow coolant pressure to exceed 60 PSI (4.14 bar).

6. An often-overlooked procedure to minimize condensation is to simply turn off the chiller any time the laser is not lasing.
Turn off the chiller and remove DC power from the laser anytime the laser is not processing material—overnight, during
shift changes, or during lunch and operator breaks.

SummaryAll water-cooled lasers can develop condensation when operating in high temperature / high relative humidity environments. The
coolant temperature must always be adjusted a few degrees above the dew point temperature to prevent condensation;
however, if coolant temperature is too high, then laser performance may degrade, and service lifetime is reduced.
The best choice to protect your laser processing investment is to air-condition the laser environment. Lowering the dew pointtemperature by reducing ambient air temperature and relative humidity means that coolant temperature can be set within therecommended range for optimum laser performance and lifetime.

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